RU2784080C1 - Method for charge preparation for producing colorless sheet glass with increased transparency - Google Patents

Abstract

FIELD: glass industry.

SUBSTANCE: invention relates to the glass industry and can be used in the production of colorless float glass. Batch preparation includes dosing, mixing and wetting in a mixer of quartz sand, soda ash, dolomite, limestone or marble, feldspar, sodium sulfate, as well as small additives. Before a direct transition, quartz sand and dolomite are replaced with similar materials with a reduced iron oxide content, and marble is used instead of limestone. Further, during the first 20-24 hours of the transition period, selenium, cobalt oxide and erbium oxide are added to each portion of the mixture prepared in the mixer in an amount 3-5 times greater than the required value, which is 0.0026-0.004% for selenium, for cobalt oxide - 0.00051-0.0008% and for erbium oxide - 0.0064-0.01% by weight of the charge. And at the end of the transition period, these materials in an amount 3-5 times more than the required value are loaded into each 3-5th portion of the mixture being prepared. In the process of the reverse transition to the production of colorless sheet glass with a standard light transmittance, the supply of selenium, cobalt oxide and erbium oxide to the charge is stopped, and as marble, quartz sand and dolomite with a reduced content of iron oxide are consumed, they are replaced with starting materials. In this case, during the first 24-36 hours of the reverse transition, iron oxide is added to each portion of the mixture being prepared in the amount of 0.05-0.113% by weight of the mixture. After that, its supply to each portion of the mixture is reduced to 0.0227-0.0015% and is stopped when marble, quartz sand and dolomite with a reduced content of iron oxide are completely replaced with starting materials.

EFFECT: increasing the accuracy of dosing and mixing of small batch additions and reducing the time for the forward and reverse transition from the production of colorless sheet glass with a standard light transmittance to the production of colorless sheet glass with increased transparency.

1 cl, 1 dwg, 3 ex

Description

The technical solution relates to the glass industry and can be used in the production of colorless sheet glass with increased transparency, produced by a high-performance float method, and in the production of rolled sheet glass intended for the manufacture of solar cells. Usually, for melting colorless glass, a mixture is prepared consisting of quartz sand, soda ash, dolomite, limestone, feldspar, sodium sulfate, as well as physical and chemical decolorizing additives based on selenium, cobalt oxides, cerium and other raw materials. At the same time, selenium and cerium oxide are expensive materials, partial or complete replacement of which significantly affects the reduction in the cost of the charge.

Usually, physical and chemical decolorizers of glass melt are used in the production of colorless glass containers, and in the manufacture of colorless flat glass with a standard light transmittance (for technical flat glass this coefficient is less than 90%) are not used. Such sheet glass, as a rule, has a bluish or greenish tint, visible when the glass is viewed end-to-end. These shades in glass are mainly due to the presence of iron oxides in its chemical composition, which gives the glass a green color. To reduce the effect of iron oxides on the transparency of glass, the so-called physical and chemical decolorizers of glass melt are introduced into the composition of the charge. Physical decolorizers in the form of selenium and cobalt oxide, by imparting additional shades to the glass (selenium gives a pink tint, and cobalt oxide gives a blue tint), compensate for the green color and increase the transparency of colorless glass. And chemical bleaching agents, for example, sodium nitrate, cerium oxide, etc., are strong oxidizing agents, which, during their dissociation, release oxygen and make it possible to transfer iron oxide FeO, which intensively stains glass green, into iron oxide Fe2O3, which introduces a greenish color to a lesser extent. shade. An additional effect is achieved when using glass decolorizers of a mixed type [1]. Erbium oxide can be attributed to such components of the glass mixture, the use of which allows not only to effectively contribute to the chemical discoloration of glass mass, but also leads to a partial replacement of expensive selenium due to the ability to color glass in pink.

Obviously, in order to increase the transparency of colorless glass and exclude a greenish tint from it, it is necessary to use charge components (mainly quartz sand, feldspar and carbonate rocks) with a reduced content of iron oxide, the concentration of which for different types of glass varies within the following limits:

optical glass - no more than 0.01%;

crystal - 0.01-0.015%;

technical glass - 0.03-0.07%;

window glass - 0.05-0.15;

glass containers - 0.05-0.25% (for premium class glass containers, this figure should be no more than 0.02%).

The concentration of iron oxide in colorless sheet glass with increased transparency (light transmission coefficient above 90%) should be close to the range of the corresponding parameter for crystal. At the same time, the minimum content of iron oxide eliminates the presence of blue and green shades of the glass surface, and glass with such a concentration of coloring impurities differs from technical sheet glass with a standard light transmittance in high purity and absolute transparency. Due to its characteristics, such glass has found wide application for the manufacture of various interior and architectural elements - facade railings, glass stairs, partitions, floors, balustrades, as well as glass furniture, shower cabins and much more.

It should be noted that the process of preparing a glass charge for the production of colorless sheet glass with increased transparency is in many respects similar to the process of preparing a charge for the manufacture of colorless containers. The main components of the raw mixture in both cases (with slight differences in percentage) are: quartz sand; soda ash; dolomite; limestone, chalk or marble; feldspar (rarely used alumina); sodium sulfate; as well as chemical and physical decolorizers of glass mass, supplied to mixers in rather small (several grams) doses. Particularly low weight of dosed portions of selenium and cobalt oxide is typical for the production of colorless glass containers, which is primarily due to the relatively low productivity (80-330 tons of glass mass per day) compared to the production of float glass, where the capacity of glass melting furnaces varies within from 600 to 1000 tons. Therefore, for the preparation of glass charge in the production of glass containers, dosing and mixing lines are most often equipped with mixers with a capacity of 1500 liters. For uniform mixing of several grams of selenium and cobalt oxide in such a volume, decolorizers are fed into the mixer as part of premixes (pre-mixtures of Se and CoO with filler). Sometimes it is also practiced to manually enter into the mixer small additives, previously weighed on a laboratory balance.

Mixers in charge preparation lines for the production of float glass usually have a volume of 4500-5000 liters (the mass of the charge in them varies from 5000 kg to 6200 kg), so evenly distribute in this volume small portions of selenium and cobalt oxide weighing from several tens of grams to several hundred grams is quite difficult.

There is a known method for preparing glass charge [2], which includes dosed supply of free-flowing (quartz sand and feldspar) components into the mixer and moistening them with water, alternately supplying the main clumping materials (soda ash and sodium sulfate) to the mixer at the end of the moistening operation and subsequent measurement of mobility prepared raw mix. After supplying 75-90% of the charge components to the mixer and reaching the mobility of the mixture of the nominal value, small additives are supplied. The use of such a mixing of the main components of the charge with small additives makes it possible to more evenly distribute materials such as selenium and cobalt oxide throughout the volume of the mixer and exclude them from falling into insufficiently mixed areas of the mixture. However, this method of supplying microadditives to the mixer increases the batch preparation time and is typical only for dosing and mixing lines with mixers having a volume of not more than 1500 liters.

When using mixers with a volume of 4500-5000 liters in the process of preparing glass charge, first dry mixing of all components, including small additives, is carried out, and then the mixture is moistened. Therefore, this method cannot be applied in the production of high performance float glass. Another technological aspect is also important, associated with the preparation of the charge during periodic repainting or discoloration of glass mass in a glass melting furnace, and which is not only not taken into account in the considered method, but is not used in the production of glass containers. In order to reduce the time of the forward and reverse transition and reduce the production costs associated with the occurrence of a significant amount of cullet with transitional color characteristics and a variable light transmission coefficient in the process of repainting or discoloration of glass mass (the same components are often used for this - selenium and cobalt oxide), it is necessary changing the mode of adding additives to the charge. Reducing the time of transition from the production of sheet glass of one color to glass of another color is achieved by introducing an increased amount of dyes or decolorizers (the so-called shock or doping dose) into the charge loaded into the glass melting furnace during the first 20-36 hours of transition to production with other color characteristics.

In this regard, the closest technical solution to the claimed solution is a method for the production of colored glass in the mass [3]. In this method, which includes the preparation of a charge from the main glass-forming components, as well as selenium, cobalt oxide, iron oxide (crocus or iron powder) and other additives, with periodic repainting of the glass mass, selenium and cobalt oxide are added to the charge during the day in an amount three times more than the required value. Such an increase in the concentration of small additives in the charge allows you to quickly change the color of the glass during the direct transition and leads to lower production costs, which are further reduced by the use of cullet with variable color, accumulated in previous cycles of periodic repainting of the glass mass. But in this method, the reverse transition from the production of colored sheet glass to colorless sheet glass with a standard light transmittance is achieved only by stopping the introduction of selenium, cobalt oxide, iron oxide and other additives into the charge. Moreover, this transition is not intensified in any way. In addition, a direct transition to the production of sheet glass with other color characteristics does not provide for the replacement of some basic glass-forming materials (quartz sand, limestone, dolomite) with other grades of similar materials, which, on the one hand, is an advantage, since it does not require additional technological operations to receive and storage of these materials. However, when switching to the production of sheet glass with increased transparency, this technological aspect is of decisive importance, since the content of iron oxide in the charge components should be minimal. So, for example, the replacement of limestone with marble makes it possible to reduce the concentration of iron oxide in this carbonate rock by 0.04%, and the use of dolomite from the Kovrov Quarry Administration in the Vladimir Region instead of dolomite. on dolomite of the enterprise "Kavdolomit" (Vladikavkaz) also gives a significant reduction in iron oxide in its composition. It is also important to note that in this technical solution for the preparation of one portion of the charge, a sufficiently large amount of selenium is required, which gives the glass the required pink hue, but actively volatilizes at all stages of preparation and transportation of the charge, as well as glassmaking. Therefore, the partial replacement of expensive selenium with erbium oxide, which is both a physical and chemical decolorizer of glass mass, allows the claimed technical solution not only to improve the quality of glass, but also to reduce its cost.

The problem to be solved is to increase the accuracy of dosing and mixing of small charge additives and to reduce the time of the forward and reverse transition from the production of colorless sheet glass with a standard light transmittance to the production of colorless sheet glass with increased transparency.

This technical result is achieved by the fact that in the method for preparing a mixture for the production of colorless sheet glass with increased transparency, including metered supply to the mixer, mixing and moisturizing in it the main glass-forming components stored in silos of the dosing-mixing line and consisting of quartz sand, soda ash , dolomite, limestone, feldspar, sodium sulfate, as well as selenium and cobalt oxide, which are loaded into the blender of the charge supplied to the glass melting furnace during the periodic transition from the production of colorless sheet glass with a standard light transmittance to the production of colorless sheet glass with increased transparency first, within 20-24 hours with a concentration 3-5 times higher than the required value and produced in each cycle of batch preparation in the mixer, after which the amount of selenium and cobalt oxide in the batch is reduced to the required concentration. Before switching to the production of colorless sheet glass with increased transparency, quartz sand used for the production of colorless sheet glass with a standard light transmittance and containing 0.04% iron oxide in its composition is replaced with quartz sand with an iron oxide concentration of 0.01-0, 02%, dolomite with an iron oxide concentration of 0.06% and limestone with an iron oxide concentration of 0.05% are respectively replaced with dolomite with a reduced iron oxide content of 0.04% and marble with an iron oxide concentration of 0.01%, and to selenium, the required concentration of which in the charge is 0.0026-0.004%, and cobalt oxide, the required concentration of which in the charge is 0.00051-0.0008%, erbium oxide is added, the initial concentration of which in each prepared portion of the charge is also in during the first 20-24 hours of the transition period exceeds by 3-5 times the required value equal to 0.0064-0.01%, and at the end of the transition period, the supply of selenium to the mixer, cobalt oxide and erbium oxide are produced in every 3-5 m cycle of batch preparation in an amount 3-5 times greater than the required value for one cycle, and before the completion of the campaign for the production of colorless sheet glass with increased transparency and before switching back to the production of colorless sheet glass with with a standard light transmittance, the dosed supply of selenium, cobalt oxide and erbium oxide to the mixer is stopped, and as it is consumed, the quartz sand with a reduced content of iron oxide remaining in the silos of the dosing and mixing line is replaced with the original quartz sand with an iron oxide concentration of 0.04%, dolomite with a reduced content of iron oxide on the original dolomite with an iron oxide concentration of 0.06%, and marble on the original limestone with an iron oxide concentration of 0.05%, while in each cycle of preparation of the mixture fed into the glass furnace, into the mixture during the first 24 -36 hours of reverse transition add iron oxide in the amount of 0.05- 0.113% of the mass of the prepared portion in the mixer, after which the supply of iron oxide to the charge in each cycle of its preparation in the mixer is reduced depending on the marble remaining in the silos of the dosing and mixing line, as well as quartz sand and dolomite with a reduced content of iron oxide to a value of 0 0227-0.0015% of the mass of the prepared portion of the mixture and stop the supply of iron oxide to it when marble, quartz sand and dolomite with a reduced content of iron oxide are completely replaced with the starting materials used to prepare the mixture in the production of colorless sheet glass with a standard transmittance Sveta.

The advantage of the proposed method of batch preparation is the possibility of a faster direct transition from the production of colorless sheet glass with a standard light transmittance to the production of colorless sheet glass with increased transparency and the reverse transition with a periodic change in the range of products, which in turn leads to a decrease in production costs.

Another advantage is a reduction in the amount of cullet having a transitional chemical composition and an increase in the output of colorless sheet glass with specified light transmission parameters during direct and reverse transitions in the operation of large-capacity glass melting furnaces.

An additional positive effect from using the proposed method of batch preparation is achieved by replacing most of the charge (about 70%) of expensive selenium, which, together with cobalt oxide, is an effective physical decolorizer of glass mass, by erbium oxide, which, unlike selenium, does not volatilize (losses from volatilization can reach 50%) and at the same time is both a physical and a chemical bleaching agent.

In addition, the lighting characteristics of glass, welded from the charge prepared according to the proposed method, are improved, since the charge provides for the replacement of part of the raw materials with similar components with a lower content of iron oxide. Moreover, during the reverse transition, to quickly restore the initial concentration of iron oxide in colorless sheet glass with a standard light transmittance, the use of initial raw materials and a “shock” (doping) increase in the concentration of iron oxide in the charge during the first 24-36 hours of the reverse transition are provided. After that, the concentration of iron oxide supplied additionally to the mixture is gradually reduced to zero and thereby stabilize the total content of this impurity in the glass, the concentration of which is determined by the content of iron oxide in the raw materials used.

It should also be noted that small doses of selenium, cobalt oxide and erbium oxide in the proposed method are fed into the mixer not in every charge preparation cycle, but in every third to fifth cycle. Moreover, in every third-fifth batch of the charge, doses of these materials are fed into the mixer with a concentration 3-5 times greater than the required value for one portion of the charge. This allows more accurate dosage of bleaches (for example, it is much more difficult to accurately dose 40 g of cobalt oxide and evenly mix them in 5000-6000 tons of charge than to perform the same operations with a mass of 120-150 g). At the same time, the average concentration of glass decolorizers in the charge is equal to the specified value, and their effective averaging in the glass mass is carried out due to the large volume of baths of glass melting furnaces for float glass, which have a capacity of 600-1000 tons of glass per day (the mass of glass in the baths of such furnaces is 2000-2500 tons). Obviously, in the production of glass containers using glass melting furnaces of much lower productivity and volume, it is impossible to perform such an operation, therefore, premix preparation is envisaged, which requires equipping weighing lines with additional dosing and mixing equipment.

The process of preparing the mixture for the production of colorless sheet glass, both with a standard light transmittance and with increased transparency, is implemented using a dosing and mixing line (Fig. 1), which includes: the first silo 1 of quartz sand; second silo 2 quartz sand; third silo 3 quartz sand; fourth silo 4 quartz sand; the first silo 5 of soda ash; the second silo 6 soda ash; the first silo 7 of dolomite; second silo 8 dolomite; the first silo 9 limestone (marble); the second silo 10 limestone (marble); silo 11 feldspar; supply hopper 12 sodium sulfate; supply hopper 13 selenium; supply hopper 14 of cobalt oxide; supply bin 15 of erbium oxide; supply bin 16 of iron oxide (crocus is used as this material); four-component weight batcher 17 of quartz sand; two-component weight dispenser 18 soda ash; two-component weight batcher 19 dolomite; two-component weigher 20 limestone (marble); one-component weigher 21 feldspar; one-component weigher 22 sodium sulfate; two-component weight batcher 23 selenium and cobalt oxide; two-component weight batcher 24 erbium oxide and iron oxide; assembly line 25; sleeve switch 26; the first mixer 27 with a water supply system 28 for moistening the mixture and an unloading hopper 29; the second mixer 30 with a system 31 for supplying water to humidify the mixture and an unloading hopper 32; belt conveyor 33 for supplying charge to the glass melting furnace (not shown).

Dosing-mixing line works as follows. In the production of colorless sheet float glass with a standard light transmittance, quartz sand of grade VS-040-1 [4] with an iron oxide concentration of 0.04% is usually used to prepare a glass batch. This sand with the help of transport and technological equipment (not shown) is loaded into the first 1, second 2, third 3 and fourth 4 expendable silos, the outputs of which are connected to a four-weight weigher 17 of quartz sand. At the same time, four silos are selected from the need to provide a 5-10 day supply of quartz sand, the daily requirement of which for glass melting in a furnace with a capacity of 600-1000 tons of glass mass per day is 400-700 tons. In addition, the presence of four silos allows, during the transition to the production of colorless sheet glass with increased transparency, to change, as the silos are used up and empty, quartz sand VS-040-1 for quartz sand grades ОВС-010-В, ОВС-015-1 and ОВС-020 -B with a lower iron oxide concentration of 0.01%, 0.15% and 0.02%, respectively.

Soda ash, which is used both for the production of colorless sheet glass with a standard light transmittance and sheet glass with increased transparency, is stored in silos 5.6, the outputs of which are connected to a two-component weigher 18.

The presence of two silos 7,8 for storing dolomite, the outputs of which are connected with a two-component weight batcher 19, also (as in the case of quartz sand) creates the possibility, when switching to the production of colorless sheet glass with increased transparency, to replace dolomite with an oxide concentration in one of the silos iron 0.06% (this concentration is typical for many Russian suppliers of dolomite) for a similar material with a lower content of iron oxide, equal to 0.04%.

Similarly, as limestone is consumed, loaded into silos 9, 10, the outputs of which are connected with a two-component weight dispenser 20, before switching to the production of colorless sheet glass with increased transparency, limestone with an iron oxide content of 0.05 is replaced in one of these silos with marble ( sometimes referred to as microcalcite) with a corresponding parameter of 0.01%.

Feldspar does not change during the transition from the production of one type of glass to another and is stored in a silo 11, the output of which is connected with a one-component weight batcher 21.

Also, in the process of transition, the brand of sodium sulfate, which is filled with hopper 12, connected by its outlet to a single-component weight batcher 22, does not change.

Selenium, cobalt oxide, erbium oxide, used in the direct transition from the production of colorless sheet glass to glass with increased transparency, as well as iron oxide used in the reverse transition, are stored in hoppers 13, 14, 15, 16. The outputs of hoppers 13, 14 are associated with a two-component weight dispenser 23 of selenium and cobalt oxide, and the outputs of the hoppers 15, 16 - with a two-component dispenser 24 of erbium oxide and iron oxide.

Weighed according to the recipe in weight dispensers 17, 18, 19, 20, 21, 22, 23, 24, the raw components of the glass charge are unloaded onto the assembly line 25 and sent through the sleeve flow switch 26 to one of the mixers 27, 30. After dry mixing, the charge components using appropriate water supply systems 28, 31 are moistened. The finished mixture from the mixers is sent to the unloading bins 29, 32 and is transported to the glass melting furnace by means of a 33 belt conveyor.

The average batch recipe used for the production of colorless flat glass with a standard light transmittance produced by the float process includes the following components:

Considering that the average charge batch in a mixer with a capacity of 4500 liters (such mixers are used to prepare batch loaded into a glass melting furnace with a capacity of 600-1000 tons of glass per day) is 5000 kg, the content of components in one charge batch by weight is as follows:

The amount of iron oxide in a given portion of the charge is determined by its presence in quartz sand (0.04% or 1.2 kg), dolomite (0.06% or 0.225 g), limestone (0.05% or 0.2 kg) and field spar (0.02% or 0.05 kg). The total amount of iron oxide in one charge batch is 1.675 kg, which is 0.0335%. This value corresponds to the range of 0.03-0.07% for technical sheet glass with standard light transmittance. Obviously, in order to reduce the percentage of iron oxide to a value close to 0.01-0.015%, corresponding to colorless flat glass with increased transparency (this value corresponds to the maximum possible concentration of iron oxide in crystal), it is necessary to use raw materials with a reduced content of iron oxide . Since the main content of iron oxide is found in quartz sand, dolomite and limestone, when switching to the production of colorless sheet glass with increased transparency, it is advisable to replace these materials with similar components with a lower content of iron oxide (naturally, these charge components will be more expensive).

Consider the amount of iron oxide in the charge when using various raw materials. After replacing the original quartz sand with quartz sand grade ОВС-020-В [4], the content of iron oxide in it will decrease to 0.020% (0.6 kg with the amount of quartz sand 3000 kg in one batch of charge in the mixer). When replacing the original dolomite with dolomite with a smaller amount of ferruginous impurities in it, the content of iron oxide in it will decrease to 0.04% (0.15 kg with the amount of dolomite 375 kg in one batch of charge). And when replacing limestone with marble, the content of iron oxide in this material will be 0.01% (0.04 kg with the amount of marble 400 kg in one batch of charge). Since the replacement of feldspar in the considered method of preparing the charge is not provided (there are no brands of feldspar with a lower concentration of Fe2O3), the content of iron oxide in this material remains the same 0.02% (0.05 kg with the amount of feldspar 250 kg in one batch of charge ). The total amount of iron oxide in one batch of the charge will be 0.84 kg or 0.0168%. The total reduction of iron oxide in a portion of the charge weighing 5000 kg in this case will be 1.675-0.84=0.835 kg.

After similar calculations, we find that when using quartz sand ОВС-015-1 [4] (iron oxide concentration 0.015%), the total content of iron oxide in the charge will be 0.69 kg (0.0138%), its total decrease in portions in portions of the charge weighing 5000 kg will be 1.675-0.69 = 0.985 kg. For the mixture with quartz sand ОВС-010-В [4] (iron oxide concentration 0.010%), the total content of iron oxide in the raw mixture is 0.54 kg (0.01%) with its decrease equal to 1.675-0.54=1.135 kg. Thus, when using different grades of quartz sand, we obtain a range of changes in iron oxide in the charge (and, accordingly, in glass) equal to 0.01-0.0168%, which is commensurate with the same range of crystal, which differs from all types of glass (except optical glass) highest transparency.

In addition to replacing quartz sand, dolomite, limestone, used for the preparation of charge in the production of colorless sheet glass with a standard light transmittance, with similar materials with a reduced content of iron oxide, an increase in the transparency of glass and the final elimination of a greenish tint in sheet glass is achieved through the use of physical and chemical glass decolorizers. The amount of these materials in the charge is selected empirically (experimental laboratory glass melting) and is set based on the maximum possible amount (0.01-0.0168%) of iron oxide in the charge. The maximum content of glass decolorizers is as follows:

The lower value of the quantitative range of selenium, cobalt oxide and erbium oxide is determined based on the ratio of the maximum and minimum amount of iron oxide in the charge prepared from quartz sand and dolomite with a reduced content of Fe2O3, as well as marble. The reduction factor that takes into account the reduction in the amount of iron oxide is:

0.84kg: 0.54kg=1.56

Therefore, the lower value of the number of bleachers in the charge will be 1.56 - times less than their maximum value. For selenium it is 0.0026% (0.004%: 1.56=0.0026%), for cobalt oxide it is 0.00051% (0.0008%: 1.56=0.00051%), and for cobalt oxide erbium, it is equal to 0.0064% (0.01%: 1.56 \u003d 0.0064%).

Thus, the required amount of selenium needed to prepare a batch of 5000 kg is: 5000 kg × (0.0026% - 0.004%) = 130 - 200 g. The required amount of cobalt oxide is: 5000 kg × (0.00051% - 0 .0008%)=25.05 - 40 g. The required amount of erbium oxide is: 5000 kg × (0.0064% - 0.01%)=320 - 500 g.

It is quite difficult to evenly distribute a similar amount of these materials in 5000 kg without preparing premixes (pre-mixtures). Also taking into account the fact that the development of the production of colorless sheet glass with increased transparency at float glass plants began relatively recently and the glass batch preparation workshops at these plants were not designed to install additional equipment for the preparation of premixes (and this is not always possible) , an increase in the accuracy of dosing of glass decolorizers can be achieved by increasing the dose of selenium, cobalt oxide and erbium oxide by 3-5 times. At the same time, for a faster transition (direct transition) from the production of colorless sheet glass to a similar glass with increased transparency, a dose of these materials increased by 3-5 times (shock dose) is loaded into the mixer in each charge preparation cycle during the first 20-24 hours of direct transition. After this transition, which provides an intensive input of glass decolorizers, the dosed supply of selenium, cobalt oxide and erbium oxide to the mixer is carried out in every 3-5 cycles of batch preparation in an amount 3-5 times greater than the required value. The average value of these materials corresponds to the required value for each portion of the mixture being prepared. The averaging of three to five times the doses of glass decolorizers begins while still in the hopper of charge loaders of the glass melting furnace and ends in the glass melting furnace during the mass transfer of glass mass during its melting. It is advisable to increase the dose threefold when melting glass in glass melting furnaces with a capacity of 600 tons of glass per day, and a fivefold increase in furnaces with a capacity of 1000 tons of glass per day (this furnace has a higher averaging capacity).

It is necessary to start introducing selenium, erbium oxide and cobalt oxide into the charge only if the following conditions are met: after preliminary replacement of the original quartz sand in at least one of the four silos 1, 2, 3, 4 with quartz sand with a reduced content of iron oxide; preliminary replacement of dolomite in one of the two silos 7, 8 with dolomite with a reduced content of iron oxide; preliminary replacement of limestone in one of the two silos 9, 10 with marble. Moreover, this replacement should be made immediately before the transition to the production of colorless sheet glass with increased transparency.

As a rule, due to the limited demand for colorless sheets with increased transparency, the campaign for the production of this type of product for each glass melting furnace with a capacity of 600-1000 tons of glass mass per day does not exceed one to two months. At the end of this campaign, the production is returned to the production of colorless flat glass with a standard light transmittance (reverse transition). To do this, the introduction of selenium, cobalt oxide and erbium oxide into the charge loaded into the glass furnace is stopped and the use of initial quartz sand with an iron oxide content of 0.04%, the use of initial dolomite with an iron oxide content of 0.06%, and the use of original limestone instead of marble with an iron oxide content of 0.05%. To carry out the reverse transition, it is necessary to ensure: at least one of the four silos 1, 2, 3, 4 has the original quartz sand; in one of the two silos 7, 8 the presence of the original dolomite; the presence of limestone in one of the two silos 9, 10. But it is practically impossible to ensure synchronous release and simultaneous replacement in silos 1,2.3.4, 7 8, 9, 10 of materials with a reduced content of iron oxide by starting materials, therefore it is advisable to use the materials remaining in these silos, taking into account the addition of the missing amount of oxide to the charge iron (up to concentration in starting materials).

According to the calculations, the reduction of iron oxide in the charge when using quartz sand grade ОВС-020-В and other materials with a lower concentration of Fe2O3 is: 1.675 kg - 0.84 kg = 0.835 kg. The decrease in iron oxide when using quartz sand grade ОВС-015-1 and other materials with a lower concentration of Fe2O3 is: 1.675-0.69=0.985 kg. And the reduction of iron oxide when using quartz sand grade ОВС-010-В and other materials with a lower concentration of Fe2O3 is: 1.675 kg - 0.54 kg = 1.135 kg. Just as in the direct transition, when a “shock” dose of bleaching agents is used, so in the reverse transition, a “shock” dose (3-5 times more than the required value) is needed to quickly reduce the iron oxide in the charge. The minimum value of this “shock” dose is 0.835 kg × 3=2.5 kg (0.05% of a portion of the charge weighing 5000 kg), which corresponds to a glass melting furnace with a capacity of 600 tons of glass per day when melting the charge using quartz sand ОВС-020 -AT. And the maximum value is 1.135 kg × 5=5.67 kg (0.113% of a portion of the charge weighing 5000 kg), which corresponds to a glass melting furnace with a capacity of 1000 tons of glass per day. In this case, the range of change in the percentage of iron oxide in the "shock" dose loaded as part of the charge into the glass furnace in the first 24-36 hours (the time is established empirically) of the reverse transition is 0.05-0.113%.

At the end of the time during which a “shock” dose of iron oxide is introduced into each plumb of the charge, the remaining unused quartz sand and dolomite with a low content of Fe2O3, as well as marble, must be used in order to release the corresponding silos of the dosing and mixing line for loading them with initial materials and ensure the required supply of raw materials. In the process of such consumption of materials with a reduced content of iron oxide, the following situations may occur:

1. All materials with a reduced content of iron oxide remained unused. In this case, depending on the use of a specific brand of quartz sand, it is necessary to compensate for the decrease in iron oxide in the range of 0.835-1.135 kg (0.0167-0.0227% of the batch weight). The maximum value of the total range of compensation for the missing amount of iron oxide is 0.0227%.

2. Any two reduced iron oxide materials left. The amount of compensating iron oxide in this case has a certain average value, for example, 0.075 kg + 0.16 kg \u003d 0.235 kg or 0.0047% (marble and limestone remained)

3. The minimum value of the total range of compensation for the missing amount of iron oxide occurs when only dolomite with a reduced (0.04%) content of iron oxide remains unused. In this case, it is necessary to compensate 375 kg × (0.06% - 0.04%) = 0.075 kg (0.0015% of a portion of the charge weighing 5000 kg).

Thus, the range of change of iron oxide in the charge after the expiration of the first 24-36 hours of the reverse transition to the production of colorless sheet glass with a standard light transmittance is 0.0015-0.0227% or 0.075-1.135 kg with a portion of the charge of 5000 kg.

Since high accuracy is not required when compensating for the missing value of iron oxide (the allowable limits for the content of Fe2O3 in colorless sheet glass with a standard light transmittance vary from 0.03% to 0.07%), this amount of iron oxide (especially 0.075 kg) can be enter into a portion of the mixture without a three to fivefold increase.

Consider several examples of the implementation of this method of batch preparation.

Example #1. The charge for melting colorless sheet glass with increased transparency in a glass melting furnace with a capacity of 600 tons of glass per day is prepared on the basis of OVS-010-V grade quartz sand with a percentage of iron oxide of 0.01%.

A portion of the mixture weighing 5000 kg contains the following initial components:

The amount of iron oxide in this portion of the charge is as follows:

- in quartz sand 3000 kg × 0.04% = 1.2 kg;

- in dolomite 375 kg × 0.06% = 0.225 kg;

- in limestone 400 kg × 0.05% = 0.2 kg;

- in feldspar 250 kg × 0.02%=0.05 kg

- total: 1.675 kg (0.0335% of 5000 kg).

The amount of iron oxide in the mixture with components containing a reduced amount of Fe2O3:

- in quartz sand 3000 kg × 0.01% = 0.3 kg;

- in dolomite 375 kg × 0.04% = 0.15 kg;

- in marble 400 kg × 0.01% = 0.04 kg;

- in feldspar 250 kg × 0.02%=0.05 kg

- total: 0.54 kg (0.0108% of 5000 kg).

The reduction in iron oxide is 1.675 kg - 0.54 kg = 1.135 kg. This corresponds to the maximum reduction and minimum content of iron oxide in a portion of the mixture. For the minimum amount of iron oxide in the charge, we choose the minimum amount of selenium, cobalt oxide, and erbium oxide corresponding to their ranges of change.

The required amount of selenium in this case is 5000 kg × 0.0026%=0.13 kg, the required amount of cobalt oxide is 5000 kg × 0.00051%=0.025 kg, the required amount of erbium oxide is 5000 kg × 0.0064% =0.32 kg.

To load this amount into the charge fed into the glass melting furnace with a capacity of 600 tons of glass per day, we choose a threefold increase in the mass of decolorizers (0.39 kg of selenium, 0.075 kg of cobalt oxide and 0.96 kg of erbium oxide). First, this number of bleachers is fed during the first 20-24 hours of the direct transition to each charge batch (“shock” dose), and then in every third charge preparation cycle.

At the reverse transition, the supply of decolorizers to the charge is stopped, and in order to quickly compensate for the missing amount of iron oxide in the charge (respectively, in glass) equal to 1.135 kg, we select a threefold increase to form a “shock” dose of iron oxide 1.135 kg × 3 = 3.405 kg (0.068 %).

With the consumption of quartz sand and dolomite with a reduced content of iron oxide, as well as marble after the first 24-36 hours of the reverse transition, the missing amount of iron oxide is compensated individually or in total: in quartz sand ОВС-010-В (up to the level of ВС-040-1 ) 3000 kg × (0.04% - 0.01%) = 0.9 kg (0.018% of 5000 kg); in dolomite 375 kg × (0.6% - 0.04%) = 0.075 kg (0.0015% of 5000 kg); in marble 400 kg × (0.05% - 0.01%) = 0.16 kg (0.0032% of 5000 kg). The maximum total amount of iron oxide that must be introduced into the mixture during the reverse transition is 1.135 kg or 0.0227%. Glass welded from a mixture with a similar lowest content of iron oxide (0.0108%) has high consumer properties and can be used for the manufacture of solar panels and ultra-transparent interior details.

Example #2. The mixture for melting colorless sheet glass with increased transparency in a glass melting furnace with a capacity of 1000 tons of glass per day is prepared on the basis of quartz sand grade ОВС-015-1 with a percentage of iron oxide of 0.015%.

The amount of iron oxide in the mixture with components containing a reduced amount of Fe2O3:

- in quartz sand 3000 kg × 0.015% = 0.45 kg;

- in dolomite 375 kg × 0.04% = 0.15 kg;

- in marble 400 kg × 0.01% = 0.04 kg;

- in feldspar 250 kg × 0.02%=0.05 kg

- total: 0.69 kg (0.0138% of 5000 kg).

The reduction in iron oxide is 1.675 kg-0.69 kg=0.985 kg. This corresponds to the average reduction and the average content of iron oxide in a portion of the mixture. For the average amount of iron oxide in the charge (based on the average value of the range of variation of iron oxide in quartz sand), we select the average amount of selenium, cobalt oxide and erbium oxide corresponding to their ranges of variation.

The required amount of selenium in this case is 5000 kg×0.0033%=0.13 kg, the required amount of cobalt oxide is 5000 kg×0.00065%=0.0325 kg, the required amount of erbium oxide is 5000 kg×0.0082% =0.41 kg.

To load this amount into the charge fed into the glass furnace with a capacity of 1000 tons of glass per day, we choose a fivefold increase in the mass of decolorizers (0.65 kg of selenium, 0.163 kg of cobalt oxide and 2.05 kg of erbium oxide). First, this amount of decolorizers is supplied during the first 20-24 hours of the direct transition to each batch batch (“shock” dose), and then in every fifth batch preparation cycle

At the reverse transition, the supply of decolorizers to the charge is stopped, and to quickly compensate for the missing amount of iron oxide in the charge (respectively, in glass) equal to 0.985 kg, we select a fivefold increase to form a “shock” dose of iron oxide 0.985 kg × 5 = 4.93 kg (0.098% of 5000 kg).

With the consumption of quartz sand and dolomite with a reduced content of iron oxide, as well as marble after the first 24-36 hours of the reverse transition, the missing amount of iron oxide is compensated individually or in total: in quartz sand ОВС-015-1 (up to the level of ВС-040-1 ) 3000 kg × (0.04% - 0.01%) = 0.9 kg (0.018% of 5000 kg); in dolomite 375 kg × (0.6% - 0.04%) = 0.075 kg (0.0015% of 5000 kg); in marble 400 kg × (0.05% - 0.01%) = 0.16 kg (0.0032% of 5000 kg). The maximum total amount of iron oxide that must be introduced into the mixture during the reverse transition is 1.135 kg or 0.0227%.

Glass welded from a mixture with a similar content of iron oxide (0.0138%) also has high consumer properties and can be used for the manufacture of facade glazing, shop windows, furniture, interior elements, etc.

Example #3. The charge for melting colorless sheet glass with increased transparency in a glass melting furnace with a capacity of 1000 tons of glass per day is prepared on the basis of quartz sand grade ОВС-020-1 with a percentage of iron oxide of 0.020%.

The amount of iron oxide in the mixture with components containing a reduced amount of Fe2O3:

- in quartz sand 3000 kg × 0.020% = 0.6 kg;

- in dolomite 375 kg × 0.04% = 0.15 kg;

- in marble 400 kg × 0.01% = 0.04 kg;

- in feldspar 250 kg × 0.02%=0.05 kg

- total: 0.84 kg (0.0168% of 5000 kg).

The reduction in iron oxide is 1.675 kg - 0.84 kg=0.835 kg. This corresponds to the minimum reduction and maximum content of iron oxide in a portion of the mixture. For the maximum amount of iron oxide in the charge (based on the minimum value of the range of variation of iron oxide in quartz sand), we select the maximum amount of selenium, cobalt oxide and erbium oxide, corresponding to their ranges of variation. The required amount of selenium in this case is 5000 kg×0.004%=0.2 kg, the required amount of cobalt oxide is 5000 kg×0.0008%=0.04 kg, the required amount of erbium oxide is 5000 kg×0.01%=0 .5 kg.

To load such an amount into the charge fed into the glass melting furnace with a capacity of 1000 tons of glass per day, we choose a fivefold increase in the mass of decolorizers (1.0 kg of selenium, 0.2 kg of cobalt oxide and 2.5 kg of erbium oxide). First, this amount of decolorizers is fed during the first 20-24 hours of the direct transition to each charge batch (“shock” dose), and then in every fifth batch preparation cycle.

At the reverse transition, the supply of decolorizers to the charge is stopped, and to quickly compensate for the missing amount of iron oxide in the charge (respectively, in glass) equal to 0.985 kg, we select a fivefold increase to form a “shock” dose of iron oxide 0.835 kg × 5 = 4.175 kg (0 .0835% of 5000 kg).

With the consumption of quartz sand and dolomite with a reduced content of iron oxide, as well as marble after the first 24-36 hours of the reverse transition, the missing amount of iron oxide is compensated individually or in total: in quartz sand ОВС-020-1 (up to the level of ВС-040-1 ) 3000 kg × (0.04% - 0.01%) = 0.9 kg (0.018% of 5000 kg); in dolomite 375 kg × (0.6% - 0.04%) = 0.075 kg (0.0015% of 5000 kg); in marble 400 kg × (0.05% - 0.01%) = 0.16 kg (0.0032% of 5000 kg). The maximum total amount of iron oxide that must be introduced into the mixture during the reverse transition is 1.135 kg or 0.0227%.

Glass welded from a charge with a similar content of iron oxide (0.0168%) is characterized by lower cost and also has high consumer properties and can be used for the manufacture of facade glazing, shop windows, furniture, interior elements, etc.

Thus, the use of this method of batch preparation makes it possible to intensify the direct and reverse transitions from the production of colorless sheet glass with a standard light transmittance to the production of colorless glass with increased transparency. The method allows the use of raw materials of the charge with different content of iron oxide and partially replace expensive selenium with erbium oxide.

Sources of information to be considered during the examination.

1. Manevich V.E. Raw materials in glassmaking // chapter in the reference materials "Technology of glass", ed. P.D. Sarkisov. M. 2012. 647 p.

2. Efremenkov V.V., Berezin V.N., Rozhkov B.C. et al. Method for preparing glass charge // Patent of the Russian Federation for the invention No. 2115632. Published 07/20/1996

3. Efremenkov V.V. Method for the production of glass colored in the mass // Patent of the Russian Federation for the invention No. 2588013. Published 06/27/2016

4. GOST 22551 - 2019 Quartz sand, ground sandstone, quartzite and vein quartz for the glass industry. Specifications.

Claims (1)

A method for preparing a charge for the production of colorless sheet glass with increased transparency, including dosed supply to the mixer, mixing and moisturizing in it the main glass-forming components stored in silos of the dosing-mixing line and consisting of quartz sand, soda ash, dolomite, limestone, feldspar, sodium sulfate, as well as selenium and cobalt oxide, the loading of the last two of which into the blender of the charge supplied to the glass melting furnace during the periodic transition from the production of colorless sheet glass with a standard light transmittance to the production of colorless sheet glass with increased transparency is carried out first for 20 -24 hours with a concentration of 3-5 times the required value and is produced in each cycle of batch preparation in the mixer, after which the amount of selenium and cobalt oxide in the batch is reduced to the required concentration, characterized in that before switching to the production of colorless about sheet glass with increased transparency, quartz sand used for the production of colorless sheet glass with a standard light transmittance and containing 0.04% iron oxide in its composition is replaced with quartz sand with an iron oxide concentration of 0.01-0.02%, dolomite with an iron oxide concentration of 0.06% and limestone with an iron oxide concentration of 0.05% are respectively replaced by dolomite, with a reduced iron oxide content of 0.04%, and marble with an iron oxide concentration of 0.01%, and to selenium, the required concentration of which in the charge is 0.0026-0.004%, and cobalt oxide, the required concentration of which in the charge is 0.00051-0.0008%, is added with erbium oxide, the initial concentration of which in each prepared portion of the charge is also during the first 20- 24 hours of the transition period exceeds by 3-5 times the required value equal to 0.0064-0.01%, and at the end of the transition period, selenium, cobalt oxide and erbium oxide are fed into the mixer in each 3-5 m cycle of batch preparation in an amount 3-5 times greater than the required value for one cycle, and before the completion of the campaign for the production of colorless sheet glass with increased transparency and before switching back to the production of colorless sheet glass with a standard light transmittance, stop dosed supply of selenium, cobalt oxide and erbium oxide to the mixer, and as they are used up, the quartz sand with a reduced content of iron oxide remaining in the silos of the dosing and mixing line is replaced with the original quartz sand with an iron oxide concentration of 0.04%, dolomite with a reduced content of iron oxide with the original dolomite with an iron oxide concentration of 0.06%, and marble on the original limestone with an iron oxide concentration of 0.05%, while in each cycle of preparation of the charge supplied to the glass furnace, the charge is added to the charge during the first 24-36 hours of the reverse transition iron oxide in the amount of 0.05-0.113% by weight of the prepared portion in mixer, after which the supply of iron oxide to the charge in each cycle of its preparation in the mixer is reduced depending on the marble remaining in the silos of the dosing and mixing line, as well as quartz sand and dolomite with a reduced content of iron oxide to a value of 0.0227-0.0015% from the mass of the prepared portion of the mixture and stop the supply of iron oxide into it with the complete replacement of marble, quartz sand and dolomite with a reduced content of iron oxide for the starting materials used for the preparation of the mixture in the production of colorless sheet glass with a standard light transmittance.

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