The thermal process, as a result of which a homogeneous melt is formed from the charge (mixture of raw materials) - glass mass, is called glass melting. Glass melting is carried out in glass melting furnaces at a temperature of 1350–1500°C. There are five cooking stages.

1. Silicate formation is a stage of solid-phase chemical reactions. The charge components under the influence of T = 900–950°C undergo physical and chemical changes, reactions occur in the solid phase with the formation of double carbonates and silicates, and a liquid phase appears due to the melting of eutectic mixtures. As a result, a dense sintered mass is formed.

2. Glass formation - the stage of obtaining a melt - glass mass without solid inclusions. At this stage, with an increase in temperature to 1200–1250°C, the processes of silicate formation are completed, the sintered mass melts, and excess silica (SiO2) gradually dissolves in the silicate melt. By the end of this stage, a chemically inhomogeneous melt is formed, which includes many bubbles.

3. Clarification (degassing) - the stage of the release of glass mass from visible gas inclusions. At this stage, as the temperature rises to Тmax = 1400–1500°C, the viscosity of the melt decreases (η = 100 pz), visible small and large gas bubbles are removed from the melt. As a result, we obtain a transparent melt without gas inclusions.

4. Homogenization - the stage of acquiring chemical, physical and thermal homogeneity by glass mass. This stage proceeds simultaneously with clarification at the same temperatures. During the processes of convection and diffusion, the chemical composition of the melt and its properties are aligned. As a result, we obtain a homogeneous melt - glass mass.

5. Studka - the stage of glass mass cooling. At this stage, the glass mass is prepared for molding. The temperature of the glass mass decreases to 1000–1100°C, as a result of which the viscosity of the melt increases (η = 104–108 poise).

In fact, the division of the glass melting process into five stages is conditional. The first four stages are superimposed on each other and go almost simultaneously, they are separated from the fifth stage (studki) in time and space. The first, second, third and fourth stages take place in the cooking room, and the fifth - in the working zone of the furnace.

Thus, glass melting is a complex physical and chemical process. Physical processes include charge heating, moisture evaporation, melting of charge components, dissolution of charge components in the melt, polymorphic transformations, volatilization of components; chemical processes - the formation of silicates, the dissociation of carbonates, sulfates, nitrates, the removal of chemically bound water.

Let us dwell in detail on each stage of cooking.

Silicate formation takes 10% of the glass melting time. The rise in temperature inside the charge layer is very slow, so there is enough time for solid-phase reactions to occur.

The main raw materials for soda-lime-silicate glasses are soda, dolomite, limestone, quartz sand, which interact with each other in the solid phase and form double carbonates and silicates according to the reactions (3):

Na 2 CO 3 + MgCO 3 \u003d Na2Mg (CO 3) 2 T> 300 ° C

Na 2 CO 3 + CaCO 3 \u003d Na 2 Ca (CO 3) 2 T\u003e 550 ° C

Na 2 Ca (CO 3) 2 + 2SiO 2 \u003d

Na 2 SiO 3 + CaSiO 3 + CO 2 Т = 600–800°C

Na 2 CO 3 + SiO 2 \u003d Na 2 SiO 3 + 2CO 2 Т> 700–850 ° C

2CaCO 3 + SiO 2 \u003d Ca 2 SiO 3 + 2CO 2 T> 600 ° C

The eutectic CaNa 2 (CO 3) 2 -Na 2 CO 3 melts at T = 740–800°C and the compounds melt: CaNa 2 (CO 3) 2 at T = 813°C and Na 2 CO 3 at T = 850° C. The resulting melt envelops the grains of SiO 2 .

There are processes of dissociation of carbonates (4):

MgCO 3 \u003d MgO + CO 2 (P \u003d 1 bar) T \u003d 540 ° C

CaCO 3 \u003d CaO + CO 2 (P \u003d 1 bar) T \u003d 910 ° C

Na 2 Ca (CO 3) 2 \u003d CaO + Na 2 O + 2CO 2 (P \u003d 1 bar) T \u003d 960 ° С

The released CO 2 gases make the sinter porous. There are modification transformations of quartz grains.

The transformation α quartz ® β quartz is of fundamental importance, since in this case the strength of the grains decreases, microcracks appear in them, as a result of which their reactivity increases.

The reactions in the lead-potash mixture are somewhat different from those in the soda mixture. The main raw materials for crystal are quartz sand, potash and red lead. The reactions of silicate formation are carried out in the following order (6):

K 2 CO 3 + SiO 2 \u003d K 2 SiO 3 + CO 2 T \u003d 300 ° C

2Pb 3 O 4 = 6PbO 2 + 2O 2 Т = 445–597°C

PbO \u003d SiO 2 \u003d PbSiO 3 T \u003d 480–580 ° C

2K 2 CO 3 + 3SiO 2 = K 2 SiO 3 + K 2 Si 2 O 5 + 2CO 2 Т = 600–800°C

melting Pb 3 O 4 T = 830°C

melting PbO T = 886°C

double lead silicate PbO + SiO 2 = PbSi 2 O 5

The processes of silicate formation are studied using the methods of DTA - differential thermal analysis, DTG - thermogravimetry; using a gas analyzer, the qualitative and quantitative composition of the resulting gases is established; using XRF - X-ray phase analysis - the qualitative and quantitative composition of hard sinter.

Ways to accelerate the stage of silicate formation include:

a) increasing the content of fusible components in the charge (alkaline and alkaline earth oxides, borates);

b) introduction of 1% cooking accelerators (fluorides, chlorides, ammonium salts) into the charge, which reduce the temperature of silicate formation reactions by 80–100°C;

c) moisturizing the charge up to 3–5%;

d) silicate formation is an endothermic process that goes with the absorption of heat and requires high costs warmth. With an increase in temperature by 100–150°C, silicate formation is accelerated by a factor of 2.

Glass formation takes 80% of the glass melting time. After completion of the stage of silicate formation in the sinter in solid form, approximately 30% of the excess amount of quartz grains is present. At the stage of glass formation, quartz dissolves in the silicate melt. This process is very slow and proceeds in the diffusion mode (with an activation energy E a = 43.7 kcal/mol).

The process of dissolution of solid SiO 2 in melts is reduced to two stages: destruction crystal lattice solid body and the transition of particles into the melt; diffusion of SiO 2 particles transferred into the melt.

The following conditions affect the rate of glass formation:

a) the size and shape of quartz grains: angular and small grains dissolve faster than rounded and large ( optimal size particles r = 0.1–0.7 mm);

b) the higher the concentration of alkali oxides in the melt, the shorter the dissolution time of SiO 2 ;

c) the higher the melting temperature, the faster the dissolution of SiO 2: with an increase in temperature for every 10°C, the rate of glass formation increases by 10%;

d) additional introduction of surfactants, which reduce the surface tension of the melt, increases the dissolution rate (for example, the introduction of sulfides in amounts of 0.1–0.3% increases the rate of glass formation by 30%);

e) high viscosity hinders diffusion; to reduce the viscosity of the glass mass, an increase in temperature is required. Optimum temperature is T = 1550–1600°C; in addition, all SiO 2 passes into the amorphous modification;

f) convective flows of glass mass accelerate diffusion processes, therefore mechanical mixing with the help of ceramic propeller mixers in the cooking zone increases the rate of removal of the dissolution products of SiO 2 grains from the diffusion zone and reduces the dissolution time.

Clarification - the release of glass mass from visible gas inclusions. Sources of gases in glass melt are:

a) air adsorbed by charge particles;

b) charge humidity – 3–7% H 2 O;

c) sublimation of volatile charge components As 2 O 3 , NH 4 Cl, CaF 2 and others;

d) decomposition of the charge components: H 3 BO 3 \u003d 3H 2 O + B 2 O 3; Me 2 CO 3 \u003d Me 2 O + CO 2; MeSO 4 \u003d MeO + SO 3;

e) interaction of glass mass with the atmosphere of the furnace, which contains 88% N 2 , 12% CO 2 , as a result of which the waste of the charge is 17–20%.

The release of glass mass from gas inclusions has a large practical value to combat glass defects - bubbles. Between the gases released during the decomposition of the charge components, the gases of the furnace atmosphere and the glass mass, an interaction occurs, as a result of which the gases dissolve in the glass mass.

Distinguish between physical and chemical dissolution of gases. During physical dissolution, the gas passes into the melt without changing its chemical form:

About 2 atm. ® O 2 rasp.

In the absence of polyvalent ions, oxygen O 2 and inert gases dissolve mainly physically. During chemical dissolution, the gas passes into the melt, changing the chemical form:

CO 2 atm. ® (CO 3) 2 rasp.

Water H 2 O, nitrogen N 2, sulfur gases SO 2, carbon dioxide CO 2, oxygen O 2 (in the presence of polyvalent ions) dissolve mainly chemically. The ratio of the amount of physically soluble gases to chemically soluble gases is 1/1000…10000.

The solubility of gases depends on the composition of the glass mass. In borate melts, the solubility of H 2 O is higher than in silicate ones. This is explained by the greater stability of =B–OH groups compared to ≡Si–OH. With an increase in the acidity of the melt, the solubility of SO 3 decreases.

The solubility of gases depends on temperature. With increasing temperature, the solubility of all gases increases, with the exception of sulfur gases. As T increases, the SO 3 bubbles shrink, so sulfate clarification is carried out at a lower temperature.

Dissolved gases affect the properties of the glass-forming melt. The decrease in the viscosity of glass mass is associated with the destruction of bridging oxygen, a decrease in the degree of bonding of the framework, and an increase in the mobility of particles. For example, the surface tension of the glass mass decreases, since SO 4 2–, CO 3 2–, OH – are displaced into the surface layer and play the role of surface-active substances (surfactants).

The processes of leveling the gas concentration in the melt or between the melt and the furnace atmosphere are determined by the diffusion of the dissolved gas. The diffusion coefficient of all gases increases with increasing temperature.

Clarification of glass melt proceeds as follows. The gas bubble is formed at the bottom of the pool and is held on a solid surface due to surface tension forces. The gas bubble in the melt is affected by the Archimedes lifting force and the Stokes force, which prevents the bubble from moving upwards. In the condition of equilibrium, the Archimedes and Stokes forces are equal, it is possible to calculate the rate of bubble rise:

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where V is the rate of bubble rise; r is the gas bubble radius; ρ c , ρ g - density of glass mass and gas; η is the viscosity of the glass mass.

The equation is valid for bubbles with a radius greater than 0.4 mm. Studies of the kinetics of gas evolution show that at 175°C, moisture and hydration water are removed, at 525°C, chemically bound water is removed, at 300°C, CO 2 from MgCO 3 , at 700°C, CO 2 from BaCO 3 , K 2 CO 3 , Na 2 CO 3 , at 675°C - decomposition of nitrates and release of O 2 , NO 2 , NO, at 1050°C - release of O 2 from the clarifier: Sb 2 O 5 = Sb 2 O 3 + O 2 .

The rate of clarification of glass melt is affected by:

a) mechanical mixing (glass mass is mixed using mechanical mixers or ultrasound, which allows to increase the clarification rate by 30-60%);

b) bubbling glass compressed air through the bottom of the furnace, which is especially effective for removing CO 2 ;

c) an increase in temperature in the clarification zone by 10°C, leading to an increase in the clarification rate by 5%. This reduces the viscosity of the melt and increases the rate of rise of gas bubbles;

d) additional electrical heating of the glass mass in the clarification zone, which makes it possible to speed up the process by 3 times, since heating induces convection;

e) additional introduction of 1% clarifiers into the mixture - substances that decompose at high temperatures (more than 1200 ° C) and release large gas bubbles. Due to the difference in partial pressures of clarifying gases and associated gases, as well as the diffusion of gases from an area with high partial pressure to an area with low partial pressure, small bubbles of associated gases disappear, and bubbles of clarifying gases grow, capturing other gas inclusions, and rise to the surface . Thus, the process of degassing of glass mass is carried out.

Homogenization is the process of increasing the homogeneity of glass mass. The reasons for the heterogeneity of the glass melt are: the heterogeneity of the glass composition (since the content of individual oxides is different: SiO 2 - 50–70%, Me 2 O - 15%, MeO - 10%, silicates of different composition are formed in the glass melt); heterogeneity of raw materials from batch to batch; different granulometric composition of raw materials; heterogeneity or stratification of the charge.

After the clarification stage, the glass melt, which is heterogeneous in chemical composition, has a cellular structure. The task of the homogenization stage is the destruction of the cellular structure, the averaging of the chemical composition, and the increase in its homogeneity.

Convective currents have a significant effect on the rate of clarification. Under the influence of convective flows of glass mass in the furnace, due to the gradient distribution of temperature, the cells are stretched into streaks, thin filamentous inclusions of a different chemical composition. Strands enriched with SiO 2 have a lower surface tension compared to glass mass and therefore easily dissolve in it. Strands enriched with Al 2 O 3 have a higher surface tension compared to glass mass and therefore dissolve poorly. The presence of striae indicates poor quality glass melt.

driving force convection is the temperature and density gradient of the glass melt. The movement of the glass mass in the furnace is mixed, the Reynolds number (Re) varies from 1–2 to 20–30. The speed of glass mass in the production flow is 2–30 m/h. There are also transverse convective currents (V = 1.5 m/h). As a result of the occurrence of longitudinal and transverse convective flows, the glass mass performs a complex helical movement.

Diffusion also plays an important role in homogenization processes. The driving force of diffusion is the gradient of the chemical potential (gradient of the concentration of the component), directed towards its decrease. The diffusion coefficient (D) depends on the nature of the cation: the diffusion coefficient for modifier cations (Na, Li, K) is an order of magnitude higher than for glass-forming cations Si, B, P; in addition, D decreases with increasing cation radius, and with increasing temperature - increases.

The rate of homogenization is affected by:

a) bubbling of glass mass with compressed air, which creates additional convective flows and doubles the rate of homogenization;

b) mechanical mixing, which increases the rate of convection and diffusion and increases the rate of homogenization by 12–15%;

c) additional electric heating, which increases the rate of convection and diffusion by 20%.

The degree of homogeneity of the glass mass affects the yield of suitable products in accordance with the equation

y \u003d ax 2 + in + c,

where y is the yield of good products; x is the degree of homogeneity; a, c, c are constants depending on the composition of the glass mass.

The homogeneity of glass mass directly determines the durability of glass products and affects their mechanical, chemical properties and thermal stability. It is determined by the electrochemical method by the potential drop at the ends of the platinum electrodes. For chemically homogeneous glass melt EMF< 3 мВ. Однородность стекла определяют по разбросу значений показателя преломления и плотности стекла, допускаются отклонения Δn и Δd соответственно 0,005 и 0,01 г/см 3 .

Studka is the preparation of glass mass for molding. As a result of studding, the glass mass must have a viscosity of: 4.8·10 8 dPa·s - for manual molding of products; 10 9 -10 8 dPa s - for mechanical molding; 10 9 -10 8 dPa s - for mechanical blowing of electric lamp glass.

The main condition for studka is a gradual, continuous and slow decrease in the temperature of the glass mass without changing the composition and pressure of the gas atmosphere of the furnace, so as not to provoke the formation of secondary gas inclusions - "midges", and also without violating the thermal uniformity of the glass mass, which can cause different thicknesses of sheet glass and fluctuations in the weight of drops for piece goods.

Glass cooling methods include:

a) barriers in the gas space in the form of a screen, bridge, narrowing of the arch to reduce the supply of heat by radiation from the cooking to the working zone of the furnace;

b) barriers on the glass mass in the form of ceramic boats, pinch, flow, which contribute to the heat loss of the glass mass.

Quality control of glass mass is carried out throughout the entire melting time. Television cameras monitor the position of the foam boundary and the glass mass mirror. The glass maker every hour takes samples of glass mass from all melting zones, controls the color, the presence of solid and gas inclusions. Control over the constancy of the glass mass level is carried out automatically by a level gauge, which is blocked with the charge loader. Control over the condition of the kiln masonry is carried out from viewing windows at the ends of the kiln walls. Control over the constancy of the chemical composition of glass and its properties is carried out chemical methods in the factory laboratory.

Glass melting is carried out in glass melting furnaces. According to the principle of operation, they are divided into batch and continuous furnaces. Pot furnaces are batch furnaces, in the same volume all five stages of cooking proceed sequentially in time. They are used for cooking optical, colored glasses and crystal. The productivity of pot furnaces is 0.6–4 t/day, the efficiency is 6–8%.

Bath ovens are continuous ovens separate parts kilns at the same time proceed five stages of cooking. Productivity 4–400 t/day, efficiency 17–28%. They are used for melting sheet, container and section glass. They are classified:

a) by type of fuel - gas, electric and liquid fuels;

b) by type of heat exchanger - recuperative and regenerative;

c) by design features - with a duct, with a pinch;

d) gas in the direction of the flame - with transverse, longitudinal and horseshoe-shaped;

e) electric furnaces according to the principle of heat transfer - direct heating, indirect heating and high-frequency.

The control of the operation of the glass melting furnace is achieved by observing the established thermal and technological operating modes of the furnace, depending on the type of furnace, its size, productivity, glass and charge composition, type of fuel, automation and mechanization.

Thermal regime depends on fuel consumption, pressure and composition natural gas. The pressure and composition of gases in the furnace are determined by the ratio of gas and air, the intensity of thrust (a vacuum in chimney). The composition of the gases in the furnace may vary depending on the combustion conditions.

The nature of the gas atmosphere in the furnace is determined by the concentration of CO and O 2: oxidizing - O 2 > 2%, reducing - CO = 0.3–0.4%, neutral - CO = 0%.

Heat exchangers - regenerators and recuperators - use the heat of waste flue gases for heating working gases (natural gas and air). In ceramic recuperators (pipe in pipe), the gas temperature reaches 1000°C. The advantage of the heat exchanger is its low cost and constant cold air heating temperature (600–700°С). The disadvantages include low efficiency.

The regenerator usually consists of a tall chamber. The regenerators are located in pairs on both sides of the bath furnace, the regenerator chamber is filled with refractory material, the regenerator grate is laid out taking into account the largest gas contact surface. Hot flue gases, passing through free channels, heat the regenerator masonry. When the refractories are heated to a certain temperature (1100°C), the direction of the flame is automatically switched. Served in a heated chamber cold air, which is heated up to 300–500°C. The advantage of the regenerator is a more complete use of the heat of flue gases, more high efficiency compared to the recuperator.

Refractory materials are needed for the construction of glass melting furnaces. They have the following requirements:

a) high fire resistance (heat resistance). Refractories must be resistant to temperatures above 1500°C;

b) high corrosion resistance. Low solubility of refractories in glass mass. There is a rule: acid refractories - for acid melts of glass mass, basic refractories - for basic melts;

c) heat resistance - resistance of refractories to temperature fluctuations. Refractories with high porosity have high heat resistance, but negligible strength;

d) sufficient mechanical strength;

e) low thermal conductivity of refractories, which plays an important role in temperature distribution and heat loss in furnaces;

f) the electrical resistance of the refractory must be higher than that of the glass melt, so that the refractories do not melt when melted in electric furnaces.

Based on the above requirements, different refractories are used for the glass melting furnace, differing in composition and properties.

According to the production method, refractories are divided into ceramic, obtained by sintering, and fused, formed by casting.

Ceramic refractories are used for laying the walls and roof of the furnace. These are grog (Al 2 O 3 30–43%, SiO 2 51–66%), dinas (SiO 2 94–98%), mullite (Al 2 O 3 60–75%, SiO 2 21–40%). Advantages of ceramic refractories: high temperature resistance, high porosity, high refractoriness.

Fused refractories are used for laying the walls and bottom of the pool bath. These are bakor 33 (Al 2 O 3 49–50%, ZrO 2 32–34%, SiO 2 12–13%), fused quartz (SiO 2 99%). Advantages of fused refractories: low porosity, high mechanical strength, high corrosion resistance, high refractoriness. Disadvantages: low heat resistance and radiation hazard.

The most important criteria for the selection of refractories are durability, safety and reliability, corrosion resistance; the price of refractories is taken into account last.

When melting glass in continuous bath furnaces, all processes of batch conversion into clarified and homogenized glass mass proceed on the surface of the glass melt filling the furnace pool. The designs and dimensions of modern continuous bath furnaces are very diverse and are determined by the composition and properties of the produced glass mass, the method of molding products, and the scale of production.

Structurally, the bath oven is divided into heated (cooking and clarification zones) and unheated (studding and working zone) parts. In the heated part, the charge is boiled, clarified, homogenized and the initial cooling of the glass mass takes place.

AT unheated part of the cooling of the glass is completed, and devices for its production are adjacent to it. By productivity, bath furnaces are divided into small (2-15 t/day), medium (up to 100 t/day) and large (100-450 t/day). Small glass melting furnaces have a heated area of ​​10 - 50 m 2, they are used for the mechanized production of large glass products, glass containers. Large furnaces with heated area from 90 to 300 m 2 are designed for the production of sheet glass.

Fig.7. Scheme of zones in the tank furnace of sheet glass with a machine channel: heated part - cooking zones ( 1 ) and lightening ( 2 ) and the unheated part - student zones ( 3 ) and production ( 4 )

Loading the charge and cullet into the furnace is carried out by mechanical loaders of the tabletop or rotary type onto the surface of the molten glass mass through the loading pocket. The mixture and cullet form a layer of about 150-200 mm thick, slightly immersed in it, on the surface of the glass melt. The mixture is heated from below by glass melt and from above by flame radiation. The surface of the charge is sintered, then a layer of foamed melt is formed on it, which flows down, exposing the fresh surface of the charge. The process of sintering, melting and removal of the melt from the surface of the charge goes on until the last layer of the charge turns into a melt covered with cooking foam. While boiling, the charge layer breaks up into isolated areas surrounded by foam, which then completely dissolve, and only foam remains. Part of the bath furnace, covered with a layer of charge, forms the border of the charge; the adjoining part covered with foam is the foam boundary. These two parts are collectively referred to as the cooking zone, which is located between the filling end of the bath furnace and the quelpunkt (maximum on the temperature curve along the length of the furnace). The part of the kiln next to the quelpunkt is called the clarification zone; this zone is characterized by the release of gas bubbles, as a result of which the surface of the glass mass is covered with accumulations of bubbles and seems "pockmarked". The clarification zone is adjacent to the stud zone, the surface of which must be mirror-like, since the release of gases must end. Studka continues in the production zone, where the glass mass cools down, acquiring the viscosity necessary for production.

To ensure the stability of the operation of the furnace, it is necessary to achieve stability in the length of each of the zones. Changing the boundaries of the melting zone causes a violation of the heating regime of deep layers, which can lead to the involvement of glass mass defective in terms of thermal and chemical homogeneity into the production flow. The stability of the length of the zones along the length of the furnace is achieved due to the precise maintenance of the temperature maximum for the glass mass at the border of the melting zone and the clarification zone; the constancy of the composition of the charge and the ratio of the charge and the battle; stabilization of specific removals of glass mass; stable thermal and gas regimes.

The glass mass in the bath furnace is in continuous motion, main reason which is the difference in levels that occurs under the conditions of selection of glass mass at the working end of the furnace. For this reason, in the bath furnace there is always a working stream, which is fed by fresh portions of the charge, which are converted into glass mass. In addition to this main working flow, the entire glass mass is involved in convection movement due to the difference in melt temperatures across the zones of the furnace basin. The quelpunkt plays a special role in the organization of convection flows, creating a thermal barrier on the way of the working and heat flows of glass mass. The thermal barrier along the line of the temperature maximum forms the boundary between the flows of glass mass in the bath furnace. From this boundary, the hottest glass mass flows down to both ends of the furnace, cools down, goes down, and moves back in the near-bottom region, creating circular flows. A temperature gradient also occurs in the transverse direction, since there is always a temperature difference near the walls of the pool and in the longitudinal axial part of the furnace. Therefore, in addition to longitudinal heat flows, there are also transverse circular flows.

Longitudinal heat flows have a bulk and working cycle. The bulk cycle is formed by the flow of cooling glass mass at the filling end of the furnace, which goes down, flows in the near-bottom area to the quelpunkt line, where it rises and returns back to the end of the batch loading.

Fig.8. The trajectory of the movement of longitudinal convection flows of glass mass in the tank furnace of sheet glass: BUT– bulk cycle; B- production cycle

The production cycle is formed by the working flow of glass mass, which is partially used for molding, and part, cooling down, descends to the bottom layers and returns back, closing the circle in the quelpunkt area. The power of the streams depends on the temperature difference on separate sections bath furnace, on the amount of glass produced, the depth of the pool and other reasons. The flow rates depend on the design of the furnace and on the place of their circulation and are 8-15 m/h for the working cycle, 5-7 m/h for the bulk cycle, and about 1 m/h for the transverse one (near the walls).

Properly organized flows of glass mass contribute to a more complete flow of all stages of glass making. Loose streams improve conditions for penetration, clarification and homogenization of glass mass. The flows of the production cycle contribute to the flow of temperature-homogeneous glass mass to the production. At the same time, the flows can adversely affect the quality of the glass melt when their direction and speed change, so the main condition for the normal operation of the bath furnace is strict observance of the constancy thermal regime, while the flows of glass mass remain stable, their intensity and paths remain unchanged.

For each furnace, depending on its design and type of glass, a certain technological mode of glass melting is established, which includes: thermal mode along the length of the furnace and temperature regime along the length of the furnace up to the molding zone.

The existing methods of intensifying the glassmaking process can be divided into two groups: physical-chemical and thermal engineering. Physico-chemical methods include: fine grinding of batch components, batch granulation, the use of cooking accelerators and illuminators, mechanical mixing and bubbling of glass mass. Thermotechnical methods include: increasing the temperature in the cooking zone, the use of electric heating.

According to the source of thermal energy, there are fiery, electric and flame-electric glass furnaces.

In flame furnaces, heating is carried out by burning natural gas in the flame space of the furnace. Maximum temperature gas space reaches 1650 0 С. The specific heat consumption is 10-14 MJ/kg of glass mass. The specific removal of glass mass from the area of ​​the melting pool, depending on the type of glass, reaches 900–3000 kg/(m2 day). Thermal efficiency of flame furnaces is 16-25%.

Heating electric ovens is based on the properties of molten glass mass to conduct electric current at temperatures above 1000 0 C and release heat according to the Joule-Lenz law. Electric furnaces for glass melting have the following advantages compared to flame furnaces: no heat loss with exhaust gases, reduction of volatile compounds losses from the charge and glass mass, creation of the necessary gaseous medium above the glass mass mirror. The temperature of the glass mass reaches high values ​​(up to 1600 0 С) compared to flame furnaces (1450-1480 0 С). The productivity of the most common electric furnaces is in the range of 0.4-4.0 tons / day. Large most modern furnaces have a capacity of 150 - 200 tons / day. The maximum specific removals are higher than in flame furnaces and range from 6000 to 10000 kg/(m2 day). Electricity consumption is 1-2 kW/kg of glass mass. The thermal efficiency of electric furnaces is 60 - 70%. The disadvantages of electric furnaces include the high cost of electricity and electrodes. The efficiency of flame furnaces can be increased up to 45-50% when using additional electric heating (AEP). The role of the DEP is to strengthen the thermal barrier of the furnace (quelpoint line) and supply heat to the charge from below, which speeds up the penetration process. Advantages of DEP: decrease in temperature in the under-roof space and increase in the furnace campaign; stabilization of the thermal regime and improvement of the quality of glass mass. The introduction of DEP makes it possible to bring specific removals up to 3000–4000 kg/(m2 day) and increases the productivity of the furnace by 10–60%.

The required productivity of the furnace is achieved by observing the established technol. and thermal conditions and the necessary routine maintenance of the furnace.

Glassmaker. stoves yavl. complex heat engineering. aggregates consisting of nodes with different modes of operation. Main part of the furnace yavl. slave. camera and therefore the mode of operation of all other nodes is subject to the mode of operation of the slave. cameras.

Each furnace has its own thermal and technological. modes, cat. depend on the type of furnace, its size and productivity, the composition of the glass and charge, on the type of heat source, and for flame furnaces on the type of fuel, etc.

The main types of glass melting furnaces at present are pot furnaces, in which glass melting processes proceed sequentially in time in the same vessel, and continuous bath furnaces, in which melting processes take place in separate parts of the furnace. Continuous bath furnaces are most widely used in glass production as they are more productive, economical and mechanized. Pot ovens used in the melting of optical, technical and other special types of glass in small quantities.

The operation of furnaces of various types is characterized by production, efficiency and heat consumption for melting glass. Efficiency of furnaces, %: pot - 6-8; bathroom periodical - 15; continuous bathrooms - 17-28; electric - 60.

The productivity of modern furnaces reaches 400 t st. per day or more. Electric furnaces - 80 tons / day.

The most effective in terms of the share of useful heat spent on cooking st. electric ovens. But their spread is constrained by the high cost of electricity compared to the cost of natural gas and other fuels.

The most uneconomical yavl. pot ovens.

The operation of the furnace is characterized by the mode, the cat. head on heat consumption, pressure and composition of gases. Depending on T to separate zones stoves set the fuel consumption. The level of T is determined by the difference in the income-consumption of heat: the > this difference, the higher the T of the furnace.

1. Glass furnaces: purpose, general classification, performance indicators.

The process of obtaining from the charge suitable for the production of glass mass occurs in a glass melter. ovens, supply required temperature conditions and heat fluxes to materials.

Furnaces are divided into: 1) Glass-making; 2) Annealing and 3) Special purpose (Tempering, foaming furnaces).

Glassmaker. oven - basic heat engineering assembly in glass technology. Ex. many designs and types of furnaces, cat. have a common signs.

Glassmaker. ovens by appointment affairs. for: furnaces for the production of container, sheet, high-quality glass.

According to the principle of action: 1) Intermittent action - all stages of glassmaking: silicate formation, glass formation, clarification, homogenization, churn - proceed in the same volume of the furnace, but at different time intervals. Periodic are: bathroom, potted. 2) Continuous action - all stages of glass melting origin. simultaneously, but in different furnace volumes (bath furnaces).

By type of fuel, cat. used for heating the furnace: 1) Liquid fuel stoves; 2) On gaseous; 3) Electrical ovens.

By way of fuel supply: 1) With transverse flame direction; 2) With a horseshoe; 3) With a longitudinal direction of the flame.

According to the method of using the heat of the exhaust gases: 1) Regenerative (intermittent heat exchanger); 2) Recuperative (continuous heat exchanger - a pipe in a tube); 3) Furnaces of direct heating (heat is not used in any way).

By design: 1) Flowing; 2) With a communal pool, etc.

By performance: 1) Furnaces of low power (capacity up to 15 tons per day); 2) Medium power (15-100); 3) High power (more than 100).

Body balance:

Receipt articles: chem. and physical fuel heat, phys. the heat of the combustion air.

Expenditure items: 1) Heat consumption for glass-making (useful heat expended); 2) Heat loss in the environment. environment through the laying of the furnace; 3) With escaping flue gases; 4) Radiation through the open hole of the furnace; 5) With flue gases.

Indicators of the efficiency of the furnace:

1) TKPD– thermal efficiency. Calculation: 1 way- according to chem. fuel heat (μ = Q glass melting/Q fuel); 2 way– according to the actually consumed heat (μ = Q

glassmaker/Q fact.).

2) Specific heat consumption- defined as the ratio of actually supplied heat to productivity. (Q sp. \u003d Q actual / P, kJ / kg)

The largest TKPD in electric. furnaces (up to 75%) (no losses with flue gases)

Pot furnaces: types, purpose, device and design features.

GP is mainly used for cooking specials. glass (technical, optical, color glass). In such furnaces, a small amount of glass mass is prepared and => arose. Possibility to carefully prepare them.

GP cases: 1) With upper; 2) With bottom; 3) Combined way. fuel supply.

GP - furnace period. actions. In the work camera installed. from 1 to 16 pots. Cooking in pots.

Multi-pot ovens - 10-16 pots; for cooking tsvetn. glass

1; 2-uh GP - for cooking optical. and tech. glasses.

HP with a top flame supply - for melting glass (high-temperature) with a short run-out (refractory glass).

HP with a lower flame supply - for fusible glasses, cat. require to continue. production modes (optical and graded glass).

GPU with combined flame supply - for melting refractory glass, cat. require a long exposure (when cooking, the upper oven works, and when working out, the lower oven works).

GPU designs:

slave. furnace chamber,

kiln roof

glass maker pot

1. cadium burner

   air regenerator

   channel for sampling smoke. gases

   glass collection pit

9,10 - metallic. strapping

11- add. channels for the selection of smoke. gases

Slave. GP chamber in shape can be: round, rectangular. or oval.

Lower part of the work cameras - circle. In the circle opposite the pots there are windows for inserting or removing the pots. These windows can be bricked up or covered with shutters. The damper has windows for maintenance. pots - charge loading, vyrab. glass melt. Between the windows there are walls and naz. piers. The arch can be based on piers or suspended, as in a bath stove. The place where the stove pots are installed. stall. The walls of the work cameras run out with a slight inclination inward, which allowed. provide uniform. warming up the pot. Under the furnace, it was made of fireclay refractories or made of clay-sand masses. District of affairs from chamotte. refractory., and top. part of the work chambers and arch from dinas. Regenerators are produced from fireclay. refractories, because a high temperature was achieved only when melting glass. Strapping - to compensate for stresses, cat. arose. in masonry with thermal expansion of refractories and for support. the whole structure. Lower the strapping is mounted in the masonry of the furnace, and the metal is pulled together at the top. connections 10.

Shkvara - glass melt, cat. flows into wells.

Cadium burner - for supplying gas-air. mixes in the work. furnace chamber; for sampling from the furnace smoke. gases; to collect greaves.

Implemented lower flame supply.

Disadvantage: 1) The flame hits upwards, => shortening the life of the furnace, due to the harsh working conditions of the vault and reducing the life of the pots; 2) Uneven. heating over the cross section of the pot.

Advantage: 1) Uniform. heating the pot in height; 2) For each. pot m. create your own opr-th temperature regime.

Double pot rectangular regenerative bake

In such an oven, in order to ensure uniform heating of the slave. kiln chambers, the width of the summer of the burners should correspond to the width of the slave. oven chambers; the flame should not is directed not at the burners, not at the roof of the furnace, then the reliable operation of the furnace is ensured.

Slave. the camera is a rectangle (1). 2 - regenerators.

Disadvantage: 1) uneven. heating the pots in height.

Cold under such furnaces can lead to crystallization (freezing) of glass mass.

The disadvantage is solved: under the furnace they make massive.

Most modern. GP - regenerative.

Regenerative GPU :

This design allowed make the bottom not massive, but warm and => solidification of the glass mass, thus. you can be warned!

Recuperative GP for techno-economics. performance surpasses regenerative HP. They are well regulated, => app. for high cooking glasses.

Slit burner:

It is located in the bottom of the oven.

Gas or liquid is used to heat the HP. fuel (fuel oil). For burning fuel oil, droppers are used, i.e. fuel oil is dripped onto the hot masonry and then the vapors enter the burner.

Design features: 1) For regenerative. furnaces per 1 m2 of the hearth of the furnace e. account for ~ 15-20 m2 of regenerator nozzles; 2) For regenerative ovens ud. nozzle rotation d.b. 15-20 m2 of reheating per 1 m3 of furnace volume.

Glass melting processes in pot glass furnaces. Technical and economic indicators and operation of pot furnaces. Glass pots.

In pot ovens, you can use round and oval pots. It is better to use oval ones, because it is better to use the area of ​​the hearth.

If you use round pots, then most of their surface is turned outward - to the circle, which impairs heat transfer.

Pots are low and high. High ones are used if the glass mass has good thermal transparency. Low and wide - if the thermal transparency is not high.

In GP, ​​temperature modes of operation are distinguished: heating, glass melting, studka, production.

Temperature chart of the furnace:

In the GP, the charge is loaded in a furnace heated to high temperatures. Loading the charge and battle impl. portions. The mixture is loaded onto cullet. Loading impl. so that the mixture does not touch the walls of the pot, because she is very active. After the penetration of one portion of the mixture (flashing), a trace is loaded. portion. So the glass melt is welded until the pot is full. Then comes clarification and homogenization. For homogenization use agitators. Further studka (III). Working out (IV). Only 60-70% of glass mass is produced.

The first brewing in a new pot is carried out only on cullet (at GP), => increase the service life of the pots. If the stove is multi-pot and the life of the pot is limited (4 months), the pots have to be changed while the stove is running. To do this, the pot is heated in ovens to 900 degrees, and the oven itself is cooled to 1100 degrees and the already hot pot is placed in the oven.

Pots are made from fireclay refractories by stuffing into metal. or plaster molds. There are quartz and other pots.

Techno-econ. pok-whether GP

efficiency< 5%, ГП применяются при пр-ве сортового, оптич. стекла, уд. расход тепла – 30 000-75 000 кДж/кг, производительность – 800-1300 кг/за цикл работы печи.

GP advantages: 1) High quality of prepared glass mass; 2) You can often change the composition or color of the glass.

Disadvantages: 1) High beat. heat consumption for melting glass; 2) Low performance.

Bath furnaces of periodic action: purpose, design features, principle of operation.

Such furnaces are used for melting high quality glass melt in small volumes.

Unlike GP, in VP, glass melting is carried out in the lower part of the slave. kiln chambers - basin. Because the walls of the pool are cooled by air from the outside, then the service life of the pool in comparison with the HP will be longer. The depth of the pool is determined by the composition of the produced glass and can be in the range of 700-300 m.

The operating mode of the VP is similar to the GP, i.e. there are the same temperature regimes (heating, melting glass, stud, working out) and one cycle of the furnace.

kiln roof

fiery space

working window

1. glass drain channel

   channel for sampling smoke. gases

2. recuperator

   walls of the fiery space

As in GP, ​​glass mass is not completely produced (only 60-70%). To change the range in the design of such furnaces, it is provided. glass drain system. If it is necessary to drain the stelomass, then the channel is heated and it pours out.

Characteristics of the furnace: productivity - 480-3500 kg of glass per day, sp. heat consumption for cooking - 11000-27000 kJ / kg.

The mixture in the VP is loaded with shuffle.

Our company develops projects of electrical melting furnaces for melting glass of various grades, basalt, frits, ... We manufacture all non-standard equipment for them (electrodes, refrigerators, charge and scrap loaders). We make start-up of furnaces, adjustment and output to operating modes. We present you some options for electric ovens:

Electric furnace with a capacity of 24 tons/day for melting container glass

In August 2012, in the city of Tokmok (Kyrgyz Republic), an electric furnace with a capacity of 24 tons / day for glass containers was put into operation at the Chui-Glass enterprise under the project of CJSC SPC Glass-Gas

The cooking basin of the square-shaped furnace is heated by 12 molybdenum bottom electrodes located in the corners.

The electric glass melting furnace is made with a removable roof. The charge and cullet are loaded by a special loader over the entire surface of the cooking part. The furnace has two glass feeders, for indirect heating of which silicon carbide heaters are used.

Estimated power of electric heating is 1000 kVA, actual power is 850-900 kVA.

Specific removal from 1 m2 of cooking area 2500 kg.

The start-up of the furnace was carried out by the specialists of CJSC NPTs "Steklo-Gaz". As the commissioning work showed, the productivity of the furnace can vary from 15 to 30 tons / day without changing the quality of the glass.

Electric furnace for cooking enamel with a capacity of 1.0 t / day

TECHNICAL SPECIFICATIONS:

Productivity - 1 t/day;

Dimensions:

length - 2.8 m

width - 1 m

height - 2.1 m

Specific removal of the melt - 1000 kg/sq.m per day;

Electricity consumption - 160 kW;

Type of electrodes - molybdenum;

Top heating - silicate heaters

Flint glass melting furnace

TECHNICAL SPECIFICATIONS:

Furnace capacity - 1.5 tons/day;

Specific glass mass removal - 2143 kg/sq.m per day;

The area of ​​the cooking pool - 0.7 sq.m;

Depth of the cooking pool - 1 m;

The area of ​​the working pool - 0.72 sq.m;

Depth of the working pool - 0.4 m;

Way of development - manual;

Consumption liquid fuel for heating the working pool - 15 kg/h;

Consumption for heating the cooking pool for the period of brooding - 80 kg / h;

Electricity - 1ph, 380 V, 50 Hz;

The power of the electric heating system of the cooking pool is 100 kW;

Specific consumption of liquid fuel per 1 kg of glass mass - 0.24 kg/kg;

Specific power consumption per 1 kg of glass melt - 1.6 kW/kg;

Furnace efficiency (general) - 16%;

Efficiency of the cooking pool - 43.6%

Electric furnace for cooking crystal with a capacity of 3 tons / day

TECHNICAL SPECIFICATIONS:

Furnace productivity - 3 tons/day;

Dimensions:

Length - 5 m

Width - 3.4 m

Height - 4.2 m

Specific glass mass removal - 2220 kg/sq.m per day;

Energy consumption - electricity, 1ph, 380 V, 50 Hz;

Electricity consumption - 150 kW;

Number of oxide-tin electrodes - 28;

Gas consumption for heating the working pool - 14.5 cubic meters / hour

Electric furnace for melting borosilicate glass

TECHNICAL SPECIFICATIONS:

Dimensions:

Length - 4.25 m

Width - 2.7 m

Height - 3 m

Specific glass mass removal - 1500 kg/sq.m per day;

Energy consumption - electricity, 1ph, 380 V. 50 Hz;

Electricity consumption - 540 kW;

Number of molybdenum electrodes

plates - 12

rods - 6

Maximum cooking temperature - 1600 degrees C;

Production temperature - 1400 degrees C;

Cooling water consumption - 7 cubic meters / hour;

Cooling water hardness - up to 2.5 mg-eq/l

Electric furnace for cooking crystal with a capacity of 6 tons / day

TECHNICAL SPECIFICATIONS:

Furnace productivity - 6 tons/day;

Dimensions:

Length - 6 m

Width - 4.2 m

Height - 5.3 m

Specific glass mass removal - 2560 kg/sq.m per day;

Energy consumption - electricity, 1ph, 380 V, 50 Hz;

Electricity consumption - 326 kW;

Quantity of oxide-tin electrodes - 44 pieces;

Gas consumption for heating the working pool - 54 cubic meters / hour

Electric furnace for melting container glass with a capacity of 25 tons / day

TECHNICAL SPECIFICATIONS:

Furnace productivity - 25 tons/day;

Dimensions:

Length - 9.3 m

Width - 4 m

Height - 4.5 m

Specific glass mass removal - 2500 kg/sq.m per day;

Energy consumption - electricity, 1ph, 380 V, 50 Hz;

Electricity consumption - 1200 kW;

Type of electrodes - molybdenum

Batch glass furnace for manual production of glass melt

The furnace is designed for melting borosilicate, lead-containing, colored and colorless soda-lime-silicate glasses. In order to obtain a homogeneous glass mass, electrodes are provided in the design of the furnace. In addition, the furnace is equipped with an adjustable melt drain, which allows you to change the composition of the glasses without replacing or washing the pot. When cooking a borosilicate melt, the drain is used as a drain to remove viscous bottom layers that reduce the quality of manufactured products.

Structurally, the furnace consists of a basin made of bacor refractory in the form of a polyhedron, heating, automation and control systems, electric heating, air supply for fuel combustion, and adjustable melt drain.

Furnace productivity - 500 - 1500 kg/day;

Dimensions:

Diameter - 2120 mm;

Height - 2800 mm

Electric furnace for cooking basalt with a capacity of 70 kg/h

TECHNICAL SPECIFICATIONS:

Furnace productivity - 70 kg/h;

Dimensions:

Length - 2.75 m

Width - 1.3 m

Height - 1.25 m

Specific glass mass removal - 2240 kg/sq.m per day;

Energy consumption - electricity, 1ph, 380 V, 50 Hz;

Electricity consumption - 150 kW;

Quantity of molybdenum electrodes - 6 pieces;

Number of lanotherm heaters - 30 pcs.

Recuperative furnace with additional electrical heating for melting basalt with a capacity of 650 kg/h

This furnace was designed by us and launched in Kazan in 2007. Four bottom electrodes were installed in the digester to speed up the melting of the basalt. The method of fuel supply was chosen from the top one using flat-flame burners GPP-5, which are unique in their kind. Loaders of raw materials into the furnace - vibrating for precise maintenance of the level of the melt in the furnace. An air heater is used to heat up to 300 degrees C the combustion air. The melt from this furnace was used to obtain basalt insulation in the form of mats.

Furnace dimensions:

Length together with feeder - 8 m;

Width - 3 m;

The height of the furnace is 2.5 m.

Specific removal of the melt - 1500 kg/sq.m per day;

Electricity consumption - 250 kW.

In continuous furnaces, the charge penetration, clarification and churn of glass melt proceed in different zones of the pool (Fig. 7.2).

The largest domestic bath furnaces (for sheet glass) have a basin width of up to 10 m, a total length of 60-70 m and a depth of 1.5 m. The basins of such furnaces can hold 2000-2500 tons of glass mass. Their daily productivity is 350-450 tons. Recently, in the production of float glass abroad, sheet glass furnaces with a capacity of over 600 tons / day have been put into operation. A large unit capacity of furnaces is economically more profitable, since with an increase in productivity, specific fuel consumption and labor costs for furnace maintenance decrease. At the same time, in the production of rolling, building, technical and other types of glass, small-sized bath furnaces are used with a capacity of 5-10 to 100-120 tons / day (large daily outputs apply to furnaces that produce sheet glass by continuous rolling).

Modern high-performance bath furnaces operate at 1500-1600 °C, and furnaces for refractory technical glasses - at 1650-1680 °C. To extend the service life of furnaces and obtain high quality glass, they are laid out from refractory materials resistant to glass melt, as well as dust and charge gases at high temperatures.

Structurally, the furnace is divided into heated (cooking) and unheated (student and development) parts. In the production of sheet window, rolled and polished glass, regenerative furnaces with a transverse flame direction and five to seven pairs of burners are used. Small furnaces in the production of building and technical glass are often built on the principle of direct heating furnaces, as well as with a horseshoe-shaped flame direction. In the heated part, the charge is boiled, clarified, homogenized, and the initial cooling of the glass mass takes place; in the unheated (student) part, the cooling of the glass mass is completed. Devices for the production of products are adjacent to the student part.

Furnace piping support column; 15 - underpacking channel; - adjusting bolt space

Parts and working compartments of furnaces are structurally separated from one another. The more completely the brewing and shaping parts are separated, the more and faster the glass mass is cooled and the higher the temperature in the brewing part can be. The most radical separation of the cooking and student parts is in flow furnaces (Fig. 7.3), designed to produce small products. In view of large surface cooling in the duct, the working flow of glass mass in such furnaces is not uniform in temperature. Therefore, in large high-performance furnaces, where the temperature of the glass mass must be the same over a wide front of its production, until recently, the cooking and student parts were separated only by the gaseous medium - by a screen or a reduced arch. Recently, due to the increase in temperature and the increase in the productivity of sheet glass furnaces, it was necessary to cool the glass mass more intensively in them. For this purpose, obstacles are lowered into the glass mass along the entire width of the narrowed initial section of the student part: pipes cooled by running water (loop coolers), with an internal diameter of 70–80 mm with an adjustable depth of immersion in the glass mass (Fig. 7.4); fireproof glass barriers different designs. They can be in the form of a flat arch - a bridge in glass mass with a screen over a gaseous medium ("immersed screen" of the system of A. N. Germanov), and the bridge and the screen are cooled by air. Another type of barrier has the form of a two-arch bridge with an intermediate support, performed with or without cooling (for example, the barrier designed by the Institute of Glass). Barriers reduce the temperature of the glass, not so much because they are cooled, but because of their inhibitory effect on the circulation of the glass. Loop two-tier refrigerators reduce the average temperature of the working flow of glass mass by 40 - 50 ° C, and refractory barriers, depending on the depth of immersion and cooling intensity, by 50 - 80 ° C.

The thermal efficiency of modern powerful sheet glass furnaces is 22-30%. Its value is the greater, the higher the specific productivity of the glass melting furnace, i.e., the more glass mass can be obtained with the same surface through which heat is lost. In domestic furnaces for the production of sheet glass produced by vertical drawing, the specific removal of glass melt c_m2 of the heated area of ​​the furnace is 1000-1500 kg/cyf. . Accordingly, the specific heat consumption of the two named types of furnaces is about 14,000 kJ and 10,500-10,600 kJ per 1 kg of welded glass mass.

The wear of refractories makes it necessary to stop the furnaces for major repairs. Domestic furnaces of sheet glass, lined with the latest resistant refractories, using the methods of their effective protection work between repairs 48 - 60 months.

Welding of the bath furnace with glass melt. Before melting glass in a newly built or repaired furnace tank, the furnace basin is welded with fresh glass mass. The quality of the finished glass depends on the purity and thoroughness of welding. Welding is started when the mode with a temperature exceeding the set one by 10 - 15 ° C is established in the bath furnace. First, a mixture is loaded into the furnace: 15% of the charge and 85% of cullet mixed with sorted pieces of cooled glass mass (erklez) released from the furnace after it was stopped for repairs. The loading is carried out in such an amount that the glass mass fills the furnace to the height of the two lower rows of pool beams (600 mm) at a speed of not more than 2-2.5 mm/h. After that, the welding speed is increased first to 5 and then to 10 mm/h, while increasing the content of the charge in its mixture with the breakage to the specified value. When setting the welding speed, it is necessary to ensure that there are few large bubbles in the glass melt samples from the melting part of the furnace and there are no bubbles less than 1 mm in diameter.

The movement of glass mass in continuous bath furnaces. In such furnaces, the melt and the charge floating on it are in continuous motion. The charge penetration, glass formation and clarification take place in the surface layer of the glass mass filling the furnace pools. The continuous selection of glass mass from the working part of the furnace causes a decrease in its level in the places of working out, which is replenished by a constant influx of melt from the melting part of the furnace. This is how a direct “production” or “production” flow is formed. The rest of the volume of glass mass, with the exception of some stagnant areas, is involved in convection movement, which is caused by different temperatures of the melt mass in certain areas of the pool, and, consequently, differences in the density and specific pressure of the glass mass along the length and width of the furnace.

In the most heated zone of the furnace, the glass mass has the lowest density (i.e., the largest specific volume) and forms a small hillock (mound) of the order of 1 mm or more, with which the melt
rolls towards bo - a), іmax

Lea cold areas of the oven.

Usually the area with the highest temperature of the glass is located approximately in the middle of the melting part of the furnace, and from here the glass moves towards the places where the most low temperature: to the cold charge loading zone, to the working devices and to the walls of the furnace, cooled from the outside with air to reduce the wear of refractories. Thus, longitudinal flows are created in the furnaces with two branches (cycles) directed towards the loading and exhaust ends of the furnace, and transverse flows directed towards the walls of the pool. The plane passing through the mound across the furnace basin, perpendicular to the bottom, is the place where the flows are divided, called the quelpunkt (source of flows). Having reached the end sections, the melt descends into the depth of the pool and moves in the opposite direction, creating a continuous circulation.

At the bulk wall of the furnace, the glass mass cooled by the charge descends, flows near the bottom in the opposite direction and, gradually heating up, rises to the surface in the quelpunkt plane, closing the so-called bulk cycle of longitudinal flows. A similar thing happens in the working part of the furnace, where the working cycle of convection flows is formed. The transverse flows also descend near the walls, and then rise at some distance from them and are involved in the longitudinal circulation.

A simplified diagram of the movement of glass flows in furnaces with a barrier and a duct is shown in fig. 7.5. The rising branch 1 of the bulk cycle A merges in the quelpunkt into the working cycle B, which, in front of the barrier P, is divided into branch 2, returning to the cooking part, and branch 3, passing under the barrier to the student part of the furnace. From the return branch 2, streams 4, 5 rise, which are included in the direct flow B. From the deep return branch of the flow B behind the barrier, branch 6 flows into the direct flow. The barrier, as it were, partially “breaks” the working convection flow into two cycles (Fig. 7.5, a).

On fig. 7.5, b, we see that in the flow furnace there is one main cycle of flows A, while the glass mass in the cycle £ is retarded by the wall and transfers only individual descending streams into the general circulation. If the kiln capacity is high and the working flow of the glass melt is highly developed, it can completely neutralize the convection circulation; the movement of the melt becomes direct-flow (Fig. 7.5, e).

The power and flow rate of glass mass in a given section of the furnace is the greater, the greater the difference in temperature of the glass mass in its hot and cold ends, as well as the greater the depth of the furnace and the shorter the section. With a decrease in the overall temperature of the glass mass and an increase in its viscosity, the speed and power of the flows decrease.

It follows from this that the nature and speed of movement of the glass mass in each particular tank furnace depend on the temperature level of the furnace, the position of the zones where the highest temperature of the glass mass develops along the length and width of the furnace; dimensions and performance of the furnace; charge loading method, which determines the thickness and length of the charge layer, which cools the glass melt and affects the power of the bulk flow cycle; the nature of the separation of the cooking and student pools; the degree of uniformity of heating of the glass mass over the surface and depth, depending on the method of heating, the nature of the torches and the translucency of the glass mass.

The ratio n of the amount of glass mass carried by convection flows b/ to the amount of Gu produced, i.e., n = = G / Gі, characterizes the power of the convection exchange of glass mass and is called the flow coefficient (or Nowaky number). In modern large bath furnaces of sheet and polished glass, n is close to 5; with suppressed convective circulation

The speed of the various flows of glass mass in the tank furnaces is approximately (in m/h):

Upper longitudinal flows of the bulk cycle. lower longitudinal flows of the bulk cycle. upper longitudinal flows of the working cycle (middle in the cooking part of the furnace) ..................................................

In the student part of the furnace ....................................................... ....

In the channel .................................................. .........................

Under the barrier (on an intermediate support). . . lower longitudinal flows of the working cycle

In the student part of the furnace ..............................

Cross flows near walls (lowering) . . surface flows in the vertical stretching channels of flat glass

Glass flows have a decisive influence on the thermal and technological preparation of melts in the bath furnace. Glass melt has low thermal conductivity and low radiance; therefore, without convection circulation, it would be impossible to transfer heat to the deep layers of the melt. In addition, granular convection directed towards the furnace loading wall slows down the movement of the direct working flow and slows down the movement of the charge over the melt surface in the cooking zone, thereby creating more favorable conditions for heating and penetration of the charge.

However, the positive effect of convection flows can be fully used only if they are rationally organized. It should be remembered that the direction, power and speed of the flows depend on the temperature distribution in the glass mass, which, as will be described below, does not coincide with the temperature distribution of the furnace lining in all zones. Rational organization flows requires, first of all, ensuring maximum activity of the bulk cycle flows. To do this, it is necessary to maintain a high temperature of the glass melt in the quelpunkt and a lower temperature near the loading pocket. An active bulk convection cycle is created by electrically heating the glass mass in the quelpunkt. As for the flows of the production cycle, their speed in the heated part of the furnaces is maintained at a moderate level so that the glass mass has time to become chemically and thermally homogeneous. For this purpose, the temperature of the melt in the second half of the melting part of the furnace after the quelpunkt is gradually lowered, and at the beginning of the fast cooling zone, a barrier is installed that slows down the production flow.

At the same time, the developed circulation of glass mass creates great difficulties in the operation of bath furnaces. It imparts great inertia to the furnaces: accidentally “spoiled” glass mass is not removed from the pool immediately, but circulates in it for a long time, gradually diluting. The production flows carry away heat from the melting part of the furnace to the glazing part, therefore, in modern high-temperature bath furnaces, large glazing parts are provided or artificial cooling of the glass mass is used. This leads to an increase in useless heat losses and to an increase in the cost of laying furnaces.

Any change in the movement routes and the regime of convection flows of glass mass can lead to a violation of the temperature, composition and quality of the glass mass entering the production, to a change in the production properties of glass and the appearance of defects. For a normally proceeding production, it is necessary that the routes, speeds and powers of the glass mass flows do not change over time, which is possible only with the strictest maintenance of the constancy of all parameters of the furnace mode. This is the basic rule for the operation of continuous bath furnaces.

Heat exchange processes. In the operating mode, the charge and broken glass are loaded into bath furnaces on a sublayer of heated melt. Loaded cold materials begin to receive heat from the radiation of the flame and the masonry of the furnace (top) and from the glass melt (bottom). Due to the very low thermal conductivity of the charge - 0.25 - 0.27 W / (m-K), its layer quickly warms up on the surface itself, the charge is sintered from above and below, and then the sinter is covered with a film of primary silicate melt penetrated by dissolving sand grains and emerging bubbles gases.

The middle part of the layer heats up slowly and remains free-flowing for a long time. Due to the low density (-1000 kg/m3), the mixture is immersed in the glass mass by 30–60 mm, i.e., all processes in it take place near the surface of the glass mass. Foamy primary melt with dissolving grains of sand (cooking foam) constantly flows down from the charge, revealing a fresh surface on which foam is formed again: the charge layer, as it were, gradually melts from above and below. As the mixture boils, it separates into islands surrounded by foam. The zone of the cooking pool, in which the charge and the cooking foam are boiled, is called the cooking zone.

Cooking foam is different in that it contains grains of undissolved quartz. Further along the length of the furnace, where the charge ends, the quartz grains are boiled and gas bubbles remain in the foam. This is a clarifying foam, or refining foam; the area where it is located is called the clarification zone. The refining foam, initially high and dense, thins and disappears towards the end of the clarification zone: the surface of the glass mass becomes mirror-like. The surface of the glass mass in the heated part of the furnace is conventionally shown in Fig. 7.6.

The same figure also shows the parameters of heat transfer occurring in different sections along the length of the heated part of the furnace. Top warmth front
The charge and glass mass are mainly (by 75 - 85%) due to the radiation of flames and red-hot masonry of the furnace, as well as through convection of moving flame gases (by 15 - 25%). From below, from the glass mass, the charge receives heat due to thermal conductivity and the melt's own thermal radiation. The amount of heat perceived by the mixture from below during flame heating is 2.5–3 times less than from above.

The thermophysical properties (thermal conductivity, heat capacity, ability to absorb thermal radiation) of charge, foam and glass mass differ significantly, so heat transfer in the melting part of glass melting furnaces is complex. Fresh cold water has the highest heat-receiving capacity.
charge; the heat absorption of the cooking and dense refining foam is half that of the cold charge. The open clean surface of the glass mass is capable of absorbing approximately 40% of the heat absorbed by the charge, since the heated melt itself radiates heat (see curve 1). The radiation absorbed by the mixture is not transmitted by it to the sublayer of glass melt: the mixture is an opaque thermal screen. Foam is a translucent screen and transmits about half of the radiation it absorbs, while pure glass mass is transparent for radiation to a depth of 100-150 mm.

Inside the melt, heat is transferred due to the fact that each heated layer of glass mass, in turn, becomes a radiator. Important role in the process of heat transfer in the furnace basin, flows of glass mass play: the circulating heated glass mass transfers its heat to the cold layers of the melt washed by it.

These properties of the batch, foam and pure glass melt explain the temperature distribution of the glass melt along the length of the bath furnace (see curves<3, 4). Шихта не только отни­мает от стекломассы теплоту, необходимую для ее физи­ческого нагрева и протекания эндотермических реакций, но и экранирует стекломассу от проникновения тепло­ты, излучаемой сверху. Поэтому расплав имеет самую низкую температуру вблизи загрузочного кармана, куда поступает холодная шихта, а самую высокую - в конце зоны рафинажной пены, где он хорошо прогревается и отдает мало теплоты.

The zone temperatures of the upper structure of the furnace (see curve 2) are distributed along the length of the furnace differently than the temperatures of the glass mass. The temperature of the laying of furnaces is the result of the balance of heat that is established in one or another section of the furnace. It is the higher, the more heat is supplied to this section and the less is spent on the technological process and on covering losses. Therefore, despite the fact that a large amount of heat is supplied to the charge cooking zone, the furnace laying temperature in this zone is lower than in the clarification zone: the charge penetration takes a lot of heat, and in the clarification zone this extraction is half as much and, in addition, the heated dense foam itself radiates heat to the upper walls and the roof of the furnace.If for some reason the foam layer becomes denser, the temperature The temperature of the furnace lining rises in this area, and the temperature of the melt decreases due to stronger shielding.From the foregoing, it follows that the temperature of the glass melt and the temperature of the furnace lining to a large extent depend on the state of the surface of the glass melt. glass mass.However, it should be borne in mind that at the end of the cooking part of the furnace, where the heat consumption temperature is reduced to cool the glass mass, and further, in the unheated student part of the furnace, the temperature of the glass mass is higher than the temperature of the masonry of the upper structure of the furnace (see Fig. curves 2, 3 in Figs. 7.6).

Due to the bulk cycle of convection flows, the boundaries of the location of the mixture and dense foam (boiling and refining) are kept at a certain distance from the loading pocket, which determines the length of the cooking zone. The longer the melting zone, the less heat penetrates the glass mass and the more difficult it is for the melt to be clarified and homogenized. Therefore, in order to ensure a constant and high quality of glass mass, such an amount of heat should be supplied to the melting zone so that the charge and dense foam do not go beyond certain limits: for example, in sheet and building glass furnaces, the length of the melting zone should not exceed 50% of the length of the heated part of the furnace .

The position of the boundaries of the charge and foam is the most important control indicator of the operating mode of the furnace. Established boundaries must be respected. If they move to the loading pocket, part of the surface of the glass melt will open and the melt will warm up; this can lead to an increase in the temperature of the glass mass in the production flow, to the rise of deep layers of glass mass and their involvement in the working flow; the latter is usually accompanied by the appearance of bubbles and chemical inhomogeneity, and sometimes by a violation of the product development process. As the melting zone lengthens (due to slower batch penetration and more abundant foam), the temperature of the glass drops; the mound separating the bulk and working cycles of flows becomes less pronounced. In this case, part of the insufficiently clarified and homogenized glass mass can flow over the surface into the area of ​​the production flow cycle and get into the production.

To stabilize the position of the boundaries of the melting zone, it is necessary that the composition of the charge, its ratio with glass breakage, the mode of their loading into the furnace, as well as the amount

The produced glass mass (eat) were strictly constant. The gas regime of the furnace should not change, and the amount of heat introduced into the furnace must correspond to its productivity. With a decrease in the productivity of the furnace, it is necessary to reduce the heat consumption. In the production of sheet and polished glass, 2800-1850-103 J are usually removed for every kilogram of decrease in furnace productivity.

Loading charge and battle. Currently, only mechanical loaders are used to load batch and cullet into bath furnaces; when setting their operating modes, they strive to ensure that the loaded materials do not linger in the loading pocket, but are also not pushed far into the furnace. Loaders must distribute the mixture over the surface of the glass mass in such a way as to provide it with the largest possible heat-receiving surface and such a form of the loaded layer, in which the resulting melting foam can drain freely.

For these purposes, the mixture is loaded with the widest possible front in the form of ridges 120–200 mm high. In recent years, the width of the loading pockets has been increased to 70% or more of the width of the furnace basin; the length of the pocket depends on the loader type.

Bath furnaces in the production of sheet and building glass are equipped with table loaders ZSh-S and rotary (Fig. 7.7). Loader tables ZSH-S end with rakes lowered close to the glass melt and have reciprocating motion. When moving back (from the furnace), charge and broken glass from the bunkers arrive on the tables; when moving forward, the materials are poured into the loading pocket and pushed into the furnace. Across the width of the pocket, several tables are installed parallel to each other with intervals between them of no more than 200 mm (Fig. 7.7, a). With a table load, the charge and the cullet enter the furnace in longitudinal ridges.

Rotary loaders (Fig. 7.7, b) are designed to load into the furnace almost continuously the charge lying on the sublayer from the slaughter. To do this, each loader has two separate hoppers and two rotors (one for cutting, the other for the charge) with rotating sector feeders underneath. Two rotary loaders are installed along the width of the pocket. The length of the pockets is increased, since an open surface of the pocket with a length of at least 1200 mm is needed to feed the cullet under the charge layer.

Loading of the mixture with a wide front onto the sublayer from the cullet, carried out by rotary loaders, allows increasing the amount of heat perceived by the mixture from above, and ensures accurate continuous proportioning of the mixture and cullet.

The rhythm of the mechanical loaders is controlled by level gauges - special devices for measuring and maintaining a constant level of glass mass in the furnace basin. Level fluctuations are permissible within very limited limits, since they cause a change in the conditions of glass formation and intensive destruction of refractories; the specified level is maintained with an accuracy of ±0.2 mm. To do this, according to the signal of the level gauge, the speed of the tables of the table loaders or the speed of rotation of the rotary feeders is changed during the continuous operation of the loaders.

Level gauges are float, electrocontact, optical, etc. In the production of sheet glass, "pecking" electrocontact level gauges with a water-cooled lever carrying a vertical platinum electrode continuously moving up and down are used. The signal from the electrode occurs at the moment of contact of the electrode with the glass mass, since a small current is applied to the electrode.

The thermal regime of the furnace. The thermal regime is characterized by the total consumption of fuel and air, their distribution over the furnace burners and the temperature level of the furnace masonry and glass mass along the furnace length. Of particular importance for the technological process is the temperature of the glass mass, but due to the difficulties of measuring it, they are guided by the temperature of the furnace masonry. The exception is the temperature of the glass mass in the student and working parts, which is the most important control parameter and must be maintained strictly constant. The temperature of the glass mass in the loading pocket is also controlled (250 - 300 mm below the melt level): in sheet glass furnaces, it should not be lower than 1200 ° C.

When setting the thermal regimes, they are set by the value of the maximum temperature of the furnace masonry, the temperature of the glass mass in the working and working parts, and the position of the charge and foam boundaries at a given furnace productivity. The position of the boundaries is set by selecting the required fuel consumption in the burners of the cooking zone, where the largest amount of heat is consumed. A large amount of heat is also supplied to the zone of dense foam (boiling and refining) to create a pronounced maximum temperature of the glass mass. Total fuel consumption in the burners of the cooking and clarification zones
ion should be 75 - 85% of its total consumption for the furnace.

The maximum temperature of the furnace masonry corresponds to the zone of dense foam. In modern gas-fired furnaces, the maximum temperature is maintained within 1560-1580 ° C, and in furnaces heated by liquid fuel - 1550 + Yu ° C.

The higher the temperature of the glass melt in the melting zone, the less fuel is consumed in the last one or two pairs of burners. If a lot of fuel has to be consumed in these burners to maintain the desired temperature of the glass mass in the stud, then insufficient heat is supplied to the cooking zone. In this mode, gas bubbles may appear in the glass mass and its temperature uniformity may be disturbed. Increased fuel consumption in the last pairs of burners (to maintain the set stud temperature) is required if the furnace is equipped with halving pockets or barriers to the gaseous medium and glass mass. However, this is done not by redistributing the gas flow among the burners, but by increasing the total gas flow to the furnace.

The air for burning fuel in modern bath furnaces is forced by a fan in a strictly established ratio with the total fuel consumption. The total and burner consumption of fuel and air are the most important control indicators of the furnace mode. Approximate fuel consumption by burners in % of the total consumption is shown in fig. 7.6.

The temperature of the glass mass and the laying of the furnace on its sides should be the same; therefore, the same flow rate of gas and air in opposite burners of the furnace should be strictly observed.

gas mode. In continuous bath furnaces, a certain pressure and composition of the gaseous medium are maintained. Furnaces must be well sealed. At the level of the glass mass, the gas pressure should be slightly positive.

In separate burners along the length of the furnace, a certain ratio of fuel and air consumption is established. This ratio is characterized by the excess air coefficient a, defined as the ratio of the volumetric content of oxygen to the combustible gases of the fuel.

First-second-third-fourth-fifth and burners

1,03-1,05 1,08-1,1 1,15-1,25

Accepted 10% more than for natural gas

When melting glasses of high translucency in all burners of the cooking zone, a should be 1.1 - 1.15.

The coefficient of excess air during combustion has a great influence on the temperature and luminosity (emissivity) of the flame. If the fuel and air entered the furnace perfectly mixed, the highest combustion temperature would correspond to the theoretical air flow, i.e. a = 1. However, in practice, the mixing of fuel and air is not ideal, therefore, the highest temperatures of natural gas combustion torches correspond to the value of a, which is somewhat higher than the theoretical one.

The emissivity of a torch depends mainly on the concentration of incandescent microscopic particles of black carbon suspended in it. Their number is greater, the smaller a. However, in order to simultaneously realize the maximum luminosity of the torch and its highest temperature, a should be 1.05-1.06 for natural gas, and 1.06-1.07 for fuel oil. Under these conditions, the greatest amount of heat can be obtained from the torches.

Maintaining the consistency of the regime. In the production of sheet glass (window and polished), the temperature of the glass mass in the working part of the furnace, measured with a thermocouple, should not deviate by more than ±1 °C; daily change in glass density according to the method of free deposition should not exceed ±0.0005-0.0007 g/cm3. To do this, it is necessary to maintain strictly constant compositions of glass and charge, the ratio of charge and cullet in the furnace load, furnace productivity and all control parameters of the regime, especially the position of the boundaries of the melting zone.

The correction of fuel consumption required when changing the productivity of the furnace is specified for each individual furnace. Fluctuations in the temperature of the furnace masonry are allowed: ±10 °С in the melting zone and ±5 °С in the zone of a pure glass mass mirror.

The productivity of the furnace must be constant in time and the same on its sides in order to avoid distortion in the position of the boundaries of the cooking zone. To
to avoid episodic fluctuations in the furnace temperature, it is necessary to maintain constant conditions for heat transfer from the furnace masonry to the external environment. Therefore, around glass furnaces, regenerators, working devices and under the bottom of the furnaces, cold or hot air should not be allowed to enter.

A change in the ratio in the glass melt of two - and ferric iron, as well as the total content (FeO + Fe2Os) entails a change in the transmission of heat rays by the glass mass, and, consequently, the temperature of the melt. To stabilize these parameters, pure iron oxide is specially added to the charge, and the constancy of the Fe0/Fe203 ratio is achieved by maintaining the specified furnace mode. In modern glass production, the constancy of the furnace regime is maintained automatically. However, automation cannot eliminate the shortcomings of the mode, so it should be used when the furnace mode is fully worked out and configured.

When melting glass in bath furnaces, it is necessary to monitor the state of the charge and foam, the position of the boundaries of the melting zone, the nature of the flames, as well as the quality of penetration and clarification of the glass mass in samples taken at the end of the melting part of the furnace using a probe-spoon.

During normal, active cooking, the charge is melted immediately upon exiting the loading pocket. Along the periphery of the ridges or islands of the charge, large bubbles of gaseous reaction products are released. During the boiling of the charge containing sodium sulfate and reducing agent, in the cooking zone and outside it, there should be no release of liquors or the appearance of dense cooking foam with inclusions of SiO2 in the form of cristobalite. If they appear, it is necessary to check the content of moisture, sand, sulfate and reducing agent in the mixture and correct them if necessary; if the charge is of poor quality, it is stopped being fed into the furnace. It is also necessary to check and, if necessary, correct the thermal and gas conditions in the cooking zone.

The refining foam (solid or in the form of loose flakes) must have a clear boundary, after which the surface of the glass mass must be mirror-like. If a thin film of foam appears on a clean surface, this means that bubbles continue to form in the glass mass, which cannot escape from the melt, because the surface of the glass mass has a low temperature (possibly due to air leaks). In this slu
tea, it is necessary to supply more heat to the zone of the charge and dense foam in order to improve the clarification of the glass mass, to check whether positive pressure is maintained in the furnace at the level of the glass mass and whether there are air leaks in the furnace or its blowing from the horns of the refractory cooling system. All observed deviations from the norm should be eliminated.

It is necessary to monitor the distribution of the charge over the width of the furnace, to prevent the accumulation of charge and foam on one side with the open surface of the glass mass on the other. With this phenomenon, a distortion occurs in the location of the boundaries of the charge and foam, leading to different heating of the glass mass along the width of the working flow. The skew is most often caused by the low temperature of the furnace and the glass mass on the side where the charge accumulates, but in some cases the skew occurs due to incorrect installation of loaders or when they operate in different modes (more charge is supplied to one side of the furnace than to the other). It is necessary to check and adjust the work of loaders, and most importantly, to adjust the thermal regime of the furnace. To equalize the temperature on the sides of the furnace, the fuel and air flow rates in the opposing burners are equalized, as well as the rarefaction and temperature of the regenerator nozzles.

When observing the torches, their length and appearance are checked. Gas jets from nozzles located in the cheeks or in the burner tooth (with the lower gas supply) must meet in the plane of entry and form a continuous flame. The latter should cover the entire width of the furnace and, in the cooking zone, spread as close as possible to the surface of the charge and dense cooking and refining foam. The flame of the torches should not fly into the inlets of opposite burners, and also touch the clean mirror of the glass. It should be light and evenly luminous: with a lack of air, the torch is long and dark, with an excess, it is transparent and short; with poor mixing of fuel and air, dark stripes or spots are visible on the flame.

Flue gas extraction conditions have a great influence on the gas and thermal regimes of bath furnaces. With a lack of thrust in any burner, the flame on the outgoing side swirls, swirls, rises to the roof, the heat transfer from it decreases, the temperature of the regenerator and channels decreases; the torch can be skewed and pulled into the adjacent burner, causing a “skew” in the temperature of the nozzles and temperature inhomogeneity of the glass mass. Therefore, it is very important, in addition to visual observation of the flares, to constantly monitor the temperatures in the regenerators and smoke channels.

The correct proportioning of fuel and air is controlled by flue gas analysis for each furnace burner; if necessary, the air flow in the individual burners is corrected. The quality of mixing depends on the design of the burners, the methods of supplying fuel to the air jet, gas and air velocities. When heating furnaces with natural gas, its speed depends on the diameter of the gas nozzle, therefore, with an increased gas flow rate, nozzles of a larger diameter are used to create the desired speed. When heating the furnace with liquid fuel, good atomization of the fuel is necessary to obtain a good torch. Therefore, it is necessary to strictly observe such specified parameters as fuel temperature, fuel and atomizer pressure in front of the injector, as well as monitor the condition and cleanliness of the injector nozzles.

Methods for controlling the modes of furnaces and controlling modes. The mode of glass melting furnaces is controlled continuously (stationary) and periodically. On the basis of stationary control, automatic control systems for furnace modes operate.

Continuously measure:

A) the level of glass mass by a level gauge;

B) the consumption of fuel and air as a whole for the furnace and for its zones using measuring diaphragms and volumetric sensors, and for individual burners, nozzles and nozzles using the same means and dispensers (for liquid fuel);

C) the temperature of the furnace walls with radiation pyrometers or through thermocouples; the temperature of the arch in the cooking part with non-through thermocouples, in the student part of the furnace and in the working channels with through thermocouples; the temperature of the glass melt throughout the furnace by through thermocouples located in the walls and in the bottom of the furnace pool and production channels; the temperature of the regenerators by radiation pyrometers sighted at the top of the nozzles and by thermocouples in the outlet burs of the regenerator sections; temperature in the chimneys by thermocouples located behind the smoke-air dampers, in front of the dampers and at the base of the chimney;

D) the pressure of the gaseous medium in the student part of the furnace with a micro-draught-and-pressure meter; rarefaction behind the trimming gates, in front of the draft gauge regulating the gate; pressure of fuel and air supplied to the entire furnace and to individual burners by manometers.

All stationary control devices work with readings registration.

Periodically measure:

A) fuel and air temperature with mercury and resistance thermometers;

B) rarefaction at the base of the chimney with a draft gauge;

C) the composition of flue gases in the horizontal channels of all burners (1 time in two days) using a portable gas analyzer of the Orsa type with a gas sampling tube-refrigerator. Periodic control also includes a systematic, scheduled check of the operation of stationary instruments and the condition of measuring diaphragms. The shift journal of the workshop records the results of periodic control, as well as data on the loading of the charge and cullet, the results of chemical analyzes of the charge and glass, information about the position of the boundaries of the charge and foam, and the quality of the glass mass samples.

Furnaces in the production of sheet window and polished glass are currently equipped with systems and means of automatic control of modes. Information about the current parameters of the furnace mode, accumulated and processed by the computer, serves as the initial signal for changing the fuel and air flow rates and the rarefaction of the chimney so that they correspond to the specified ones. Currently, glass melting furnaces operate automatic systems for changing the direction of the flame, loading the charge and cullet, maintaining constant fuel consumption and the ratio of fuel and air, as well as constant gas pressure in the studing part of the furnace and the mode of bubbling glass mass (if it is used). So that the pressure of gases in the student part of the furnace does not change, artificial air injection is used at the signal of a thermocouple installed in the glass mass in the working section of the furnace. A constant ratio of fuel and air is maintained by adjusting the volume of incoming air, while amending the temperature of the gas and air, since its fluctuations cause changes in their density, i.e., specific volumes.