Title - PROCEDURE FOR PREPARING A MIXTURE OF GLASS RAW MATERIALS FOR A GLASS FURNACE FOR GLASS MANUFACTURING

Abstract

A glassmaking process comprising the preparation of a mixture of glassmaking raw materials for a glass furnace, wherein water, sand, and sodium carbonate are mixed in mass proportions of between 0 and 5%, 40 and 65%, and more than 0 and at most 25% respectively, and, within less than 10 minutes, preferably simultaneously, calcium oxide is incorporated in a mass proportion of between 1 and 20% of the total, the calcium oxide having a particle size such that more than 97% by mass does not pass the 0.125 mm sieve, more than 96% by mass does not pass the 0.5 mm sieve, and preferably more than 95% by mass does not pass the 1 mm sieve.

Description

27558 GLASS MANUFACTURING PREPARATION AND GLASS FURNACE Description The invention relates to the glass industry. Melting the constituent materials of glass requires a large amount of energy. The temperature of the glass bath is on the order of 1300 to 1500°C. Depending on its composition, the glass is intended for direct domestic use, such as drinking glasses and glassware, or indirect use, such as ceramic hobs, or for industrial use. The furnace is subjected to very high thermal and mechanical stresses. It is constructed with high-quality refractory linings. These refractory linings are expensive and sensitive to certain glass constituents that are susceptible to chemical reaction. Since refractory linings are poor conductors of heat, the glass bath is heated from the top. A liquid or gaseous fuel burner is located between the glass bath and the furnace roof, called the vault. The glass bath is heated primarily by radiation. The exhaust gas temperature ranges from 1300 to 1600°C, depending on the type of glass. Furthermore, glassmaking releases large quantities of gas. The glass bath is degassed for several hours to prevent bubbles from forming in the glass. To facilitate degassing, refining additives such as sulfates may be used. The furnace operates in batches of glass of a chosen composition. The exhaust gases, resulting from degassing and combustion, are evacuated through a chimney. The Applicant has continued with the objective of a further reduction in energy consumption related to the mass of glass produced. In soda-lime glass, the main starting materials are limestone, sodium hydroxide (for example, in the form of sodium carbonate, Na₂CO₃), and silica (in the form of quartz sand). The limestone and sodium carbonate release CO₂ during the glass refining process. Document JPS55100236 describes the use of slag for glassmaking. However, numerous technical obstacles have not been addressed. The Applicant is unaware of any industrial implementation of this technology. US 2,084,328 describes a glass furnace charge made from wet-mixed dolomite and kaolin. The dolomite and kaolin slurry is 1858782 of 17 calcines, then it is mixed with the ash of sodium hydroxide, sand and quicklime. Document US2005 / 0022557 describes a Na2CO3 and SO2 premix and in parallel a CaCO3 and SiO2 premix with prior reaction, followed by a mixture of two premixes and a complement of SiO2 after introduction into a glass furnace. Document US2012 / 0216574 concerns a glass manufacturing process comprising the calcination of CaCO3 to form CaO, the formation of a liquid-phase Na2SO3 glass, and the liquid-phase mixing of CaO and Na2SO3 to form a soda-lime glass. Furthermore, the Applicant has learned of a “Glass Trend Seminar” held on October 18 & 19, 2012 in Eindhoven, where Mr. Hande Sesigür, Mr. Melek Orhon, and Mr. Banu Arslan of SISECAM presented a document titled “Alternative Raw Materials for Improving the Melting Properties in Glass Production.” This document refers to a trial introduction of calcined limestone into a glass furnace, resulting in a slight reduction in energy consumption, easier melting, and an increase in the furnace's specific output, but at a higher cost per ton of glass produced. The trial also resulted in a significant amount of dust above the glass bath, increased corrosion of the furnace walls, and problems with particle adhesion. The Applicant has conducted tests. Replacing limestone with quicklime in glassmaking materials presents difficulties, particularly related to the reactivity of lime with atmospheric humidity. The economic balance of quicklime is less favorable than that of limestone, despite the reduced tonnage transported and handled. Furthermore, lime with a coarse particle size melts slowly in the glass bath and can leave infused particles. Lime with a fine particle size generates dust from the combustion gases. Some of the lime is lost and can clog the flue pipes below the furnace. Despite these obstacles, the Applicant has persevered and developed a mixture of glass raw materials. A difficulty arises during the preparation of the mixture. In the absence of water, the powdered mixture lacks cohesion and generates a large quantity of dust. However, water and lime react together exothermically. The resulting temperature makes the mixture difficult to handle. The Applicant has developed a procedure for preparing a precursor mixture that provides a mixture with low heating and low dust generation, see WO2019002802. The particle size distribution of the constituents added to the The mixture of 1858782 and 17 is largely preserved, with the difference that mechanical transfer processes can generate a crushing effect that slightly reduces the particle size. When introduced into a glass furnace, this mixture allows for a reduction in the energy required for glass production and in the amount of CO2 released, on the order of 3 to 6%. Furthermore, the melting time of this mixture is shorter than that observed when using calcium carbonate. This results in increased furnace productivity, which also translates into a further reduction in energy consumption of on the order of 4 to 6%. The Applicant has continued its investigations to understand the dust generation phenomenon. For high melting kinetics, a fine lime was applied, taking into account the availability of workers at the lime kilns. However, in the mixing workshop and in the transport circuit of the prepared composition, the problem of dust emitted into the ambient air arose. A dust removal circuit was installed. However, the dust removal circuit was clogged with a fine, adherent lime, which was therefore unstable over time. The invention improves the situation. The invention proposes a glass manufacturing process comprising the preparation of a mixture of glass furnace raw materials, in which water, sand, sodium carbonate are mixed in mass proportions between 0 and 5%, 40 and 65%, and more than 0 and at most 25% respectively, and secondary glass raw materials, and, within a period of less than 10 minutes, preferably simultaneously, calcium oxide and optionally calcium carbonate are incorporated in a mass proportion between 1 and 20% of the total, the calcium oxide having a particle size such that more than 97% by mass does not pass the 0.125 mm sieve, more than 96% by mass does not pass the 0.5 mm sieve, preferably more than 95% by mass does not pass the 1 mm sieve. In one embodiment, the raw materials for secondary glasses comprise at least the following: Al2O3, MgO, K2O, BaO, CeO2, Er2O3, TiO2, B2O3, ZnO, SrO, SnO2. In one embodiment, the preparation of the mixture takes place without the application of heat. In one embodiment, the raw materials are powdered. In one embodiment, the particle size is measured using a square mesh sieve. 1858782 of 17 In one embodiment, the aforementioned calcium oxide has a granulometry d10 between 0.5 and 2 mm and d90 between 3 and 4.5 mm. In one embodiment, the calcium oxide is formed in grains with a thickness between 20 and 60% of their length and width. Sieving can be used to measure the particle size distribution of the elongated grains. In one embodiment, the aforementioned calcium oxide is formed in grains less than 10 mm wide. In one embodiment, the aforementioned calcium oxide is formed in grains less than 3 mm thick. In one embodiment, the aforementioned calcium oxide is formed in grains less than 15 mm long for 90% of the grains. In one embodiment, the aforementioned mixture of water, sand, calcium oxide and sodium carbonate with at most 5% moisture. In one embodiment, the sodium carbonate has a particle size distribution with less than 5% passing the 0.075 mm sieve, less than 15% passing the 0.150 mm sieve, and less than 5% not passing the 0.600 mm sieve. In one embodiment, the aforementioned mixture of water, sand and sodium carbonate has at most 3% moisture with the sodium carbonate having a particle size mostly greater than 0.500 mm and less than 1.000 mm. In one embodiment, the aforementioned mixture of water, sand and sodium carbonate has at most 2% moisture with the sodium carbonate having a granulometry mostly less than 0.250 mm. In one embodiment, the calcium oxide comprises by mass less than 1000 ppm of Fe2O3, preferably less than 900 ppm, plus preferably less than 850 ppm. In one embodiment, the initial temperature of the raw materials is at least 30°C. The rate of hydration of sodium carbonate is increased. In one embodiment, the calcium oxide has a particle size distribution such that more than 98% by mass does not pass through the 0.08 mm sieve. In one embodiment, the calcium oxide has a particle size distribution such that more than 97.5% by mass does not pass through the 0.2 mm sieve. In one embodiment, the calcium oxide has a particle size distribution such that more than 97.5% by mass does not pass through the 0.5 mm sieve. In one embodiment, the calcium oxide has a particle size distribution such that more than 98% by mass does not pass through the 0.125 mm sieve. 1858782 of 17 In one embodiment, the calcium oxide has a particle size distribution such that more than 97% by mass does not pass through the 1 mm sieve. In one embodiment, the calcium oxide has a d50 granulometry between 1 and 4 mm, preferably between 1.5 and 4 mm, more preferably between 2 and 3.25 mm. In one embodiment, the aforementioned sand is dry. The amount of water added is carefully controlled. In the variant without added water, preferably associated with medium or coarse particle size, energy consumption is reduced. The sand is considered dry with a moisture content of less than 0.1%. The sand can be dried by heating to a temperature of 15 to 20°C above ambient temperature. In one embodiment, water is present in the aforementioned sand, preferably 3 to 6% by mass. At least 3% prevents the sand from drying out. At most 4.8% is conducive to slow heating. At most 6% is conducive to low dust development. The cost of adding water is avoided. In one embodiment, the calcium oxide is without the intentional addition of aluminum oxide. The aluminum oxide may be added during mixing. In one embodiment, reclaimed glass is incorporated into the raw material mixture, either before or after the addition of calcium oxide, in a mass proportion of between 5 and 40% of the total. The reclaimed glass may come from degraded glass batches. These batches have a known composition so that the quantities of the other raw materials are adjusted to the desired glass quality. In one embodiment, the raw material mixture is prepared in the solid state. This prevents water evaporation, which would occur with a slurry. It also avoids the energy consumption associated with pre-melting the raw materials. In one embodiment, the mixture of raw materials is prepared at a temperature between ambient temperature and ambient temperature increased by 20°C. In one embodiment, the raw material mixture is prepared at a temperature between +0 and +35°C relative to the previous temperature of the water, sand, sodium hydroxide carbonate, and calcium oxide. A weighted average may be taken as the previous temperature. In one embodiment, the raw material mixture is prepared without the application of thermal energy. This prevents the mixture from drying out, which generates fines and 1858782 of 17 then of powders. In one embodiment, the aforementioned mixture is loaded into an electric oven. In one embodiment, a mixture of water, sand, sodium hydroxide, and calcium oxide, and optionally calcium carbonate, is loaded into a glass furnace. The calcium oxide is present in a mass proportion of between 1 and 20% of the total mixture. The mixture is then heated by at least one burner with a flame directed towards it. This burner provides good efficiency and a glazing effect, directing the powders onto the surface of the molten glass bath. In one embodiment, the oxidizer supplied to the burner is oxygen. The glazing effect of the powders is increased. In one embodiment, water, sand, sodium carbonate, and calcium oxide, and optionally calcium carbonate, are present in mass proportions of 0–5%, 40–65%, 1–25%, and 1–20%, respectively, for 25% recycled glass incorporated. The percentage of recycled glass may vary by adjusting the aforementioned proportions. In one embodiment, the decarbonation of Na2CO3 is carried out in the glass furnace in the liquid phase. In general, the mixture of raw materials refers to the raw materials of glass. Other features and advantages of the invention will become apparent upon examination of the detailed description below, and of the accompanying drawings, in which: [Figure 1] is a diagram of the ambient air measurements made to the kiln loader with the test batches of quicklime. [Figure 2] is a diagram of the ambient air measurements taken under the kiln hopper, at the level of the vibrating inlets with the test batches of quicklime. [Figure 3] is a temperature evolution curve of the vitrifiable mixtures according to the quicklime used and the percentage of moisture in the sand. [Figure 4] is an evolution curve of the amount of powders recovered during laboratory tests according to the quicklime used and the percentage of moisture in the sand. The attached drawings may serve not only to complete the invention, but also, if necessary, to contribute to its definition. In addition to the tests reported in WO2019002802, other tests have been carried out. 1858782 of 17 Most subsectors of the glass industry use wet mixes to limit dust from raw materials, particularly sodium carbonate or sand (crystalline silica). The target moisture content varies from one facility to another. In the presence of moisture, quicklime reacts, resulting in heat release due to the exothermic hydration reaction and increased dust generation. Hydrated lime is much more susceptible to this phenomenon than quicklime or anhydrous lime. This dust is emitted simultaneously during the preparation of raw material mixes, in the transport circuits upstream of the furnace, when the mix is ​​introduced into the furnace, and even within the furnace itself. This ultimately leads to clogging of the regenerators due to the accumulation of refractory deposits downstream of the furnace. Furthermore, since they are rarely used in glassmaking, the quicklime available on the market is often poorly suited to the specific needs of transparent glass: - Chemical characteristics: few limes have an iron content level adapted to our needs, as iron is a contaminant of glass that degrades the discoloration and transparency of the glass produced. - The particle size of quicklime is often very fine (d50 between 0.15 and 0.5 mm) to meet the needs of existing applications, for example metallurgical, chemical or agricultural. Through its research program, the Applicant has succeeded in using this type of quicklime in its glass furnaces. It was identified that lime particles smaller than 0.100 mm presented a problem. It was subsequently determined that reducing the proportion of small particles, in some cases by setting the limit above 0.100 mm, proved advantageous for achieving a tangible, stable, and reproducible result regarding dust emissions. Several batches of quicklime were then tested: The batches had very different particle sizes: batch 1 had a d10 size of less than 0.08 mm, a d50 size of 0.17 mm, and a d90 size of 3.18 mm, while batch 2 had a d10 size of less than 0.08 mm, a d50 size of more than 2.5 mm, and a d90 size of 3.76 mm. The particles were approximately the same size in all three dimensions. Batch 2 appeared to be particularly affected by the presence of very coarse particles, which did not pass through the 8 mm sieve, resulting in excessively slow melting. 1858782 of 17 [Table 1] Sample Quicklime Batch 1 Sieve Diameter Measurement mm % Rejection % Cumulative 4 10.3 10.3 3.15 4.5 14.8 2 6.9 21.7 1 9.4 31.1 0.5 8.5 39.6 0.2 13.5 53.1 0.125 26.5 79.6 0.08 3.7 83.3 remainder 16.6 99.9 [Table 2] Quicklime Sample, Lot 2, Sieve Diameter, Measurement (mm), % Rejection, Cumulative %: 4, 34.9, 34.9, 3.15, 15.2, 50.1; 2, 12.4, 62.5; 1, 10, 72.5, 0.5, 5.4, 77.9, 0.2, 4.6; 82.5, 0.125, 2.5; 85, 0.08, 2.4; 87.4, remainder, 12.5, 99.9 After the removal of the coarsest particles by sieving in the laboratory, the granulometric spectrum of the sieved batch 2, with a granulometry d10 of less than 0.08 mm, d50 of 0.19 mm, and d90 of 1.9 mm, is similar to that of batch 1. [Table 3] Sample Quicklime lot 2 sieved 5 mm sieve diameter measurement mm % rejection % cumulative 4 2.5 2.5 3.15 4.3 6.8 2 10.8 17.6 1 15.4 33 0.5 12.4 45.4 0.2 14.2 59.6 0.125 7 66.6 0.08 8.3 74.9 remainder 25 99.9 A batch no. 3 of quicklime grains with a particle size of less than 3.6 mm. 1858782 of the 17 particles had a shape with approximately equal three dimensions. The percentage of fines is similar to that of batch no. 4. A batch of 4 flat-shaped quicklime grains. In other words, the thickness is approximately 20 to 60% of the length and width. The width is less than 10 mm. The thickness is less than 3 mm. The length is generally less than 15 mm. Industrial test To confirm the impact of these particle sizes on the production site, tests were carried out in a production oven with batches 1 to 4 presented below. Quicklime has been introduced in accordance with WO2019002802. The impacts on dust emissions in the work environment have been measured: [Table 4] Loader in furnace Vibratory inputs Inhalable [10-6g / m3] Thoracic [10-6g / m3] Alveolar [10-6g / m3] Inhalable [10-6g / m3] Thoracic [10-6g / m3] Alveolar [10-6g / m3] Reference lime 2604 788 217 2065 1132 432 Cal lots 1 and 2 936 519 154 4034 1740 453 Cal lot 3 825 239 103 208 134 70 Cal lot 4 121 68 38 379 174 78 - Batches 1 and 2 do not guarantee a substantial improvement in dust emissions. If the balance favors the input of materials into the furnace, the emission level at the feed inlets remains unchanged or degrades, as illustrated previously. The fraction of fine particles present has been identified as the source of this problem. - Batch 3 presents interesting dust emissions, especially in the vicinity of vibrating inlets: between 85 and 95% reduction for inhalable dusts, and between 80 and 90% reduction for alveolar dusts defined according to INRS technical memorandum ed984, 4th edition, October 2016, ISBN 978-2-7389-2240-3. - Lot 4 shows very interesting dust emissions, regardless of the measurement location: more than 80% reduction for inhalable dusts, and more than 80% reduction for alveolar dusts as defined above. Given these results, lot 4 has been retained. Longer-term tests have been organized with a granulometry from batch 4 in order to also have a more complete view of the behavior of this material in the kiln, and to estimate the impact of this new granulometry on the yields of tonnage produced and energy consumption observed with its variant 1858782 of 17 finely crushed: Phase 1: Introduction in accordance with WO2019002802. [Table 5] Sample Quicklime Lot 4 Sieve Diameter Measurement 1 Measurement 2 mm % Rejection Cumulative % Rejection Cumulative % Rejection % Rejection 4 9.4 9.4 22.3 22.3 3.15 23.6 33 41.6 63.9 2 45 78 31.9 95.8 1 19.3 97.3 2.5 98.3 0.5 0.4 97.7 0.5 98.8 0.2 0.2 97.9 0.2 99 0.125 0.2 98.1 0.1 99.1 0.08 0.3 98.4 0.2 99.3 remainder 1 99.4 0.2 99.5 Measurements 1 and 2 were taken by extraction from two subdivisions of the same batch of lime, which was then mixed and loaded into the kiln. The percentage of fines smaller than 0.20 mm is less than 2.5%. The percentage of fines smaller than 0.125 mm is less than 2.0%. The main lessons learned from this test are the following: Daily tonnage achieved: increase compared to the same glass obtained from limestone without quicklime. The daily tonnage yield is maintained compared to fine lime despite the increase in particle size. Energy consumption per ton of molten glass: no increase in furnace consumption linked to the increase in the particle size of the raw material, even a slight decrease of 3.46% with the quicklime of batch 4. The tables below compare 4 different periods, using quicklime from the reference batch, batch 3 and batch 4. All these production periods have the same percentage of broken glass (25%) and with the same other raw materials: sand, sodium carbonate, etc... During these 4 periods, the daily production has been set according to industrial needs without seeking a particular performance, that the normal production of the kiln is 110 tons / day in conventional feed with limestone and without quicklime. The reference batch is a quicklime that has a granulometry d10 < 0.1 mm; d50 < 0.1 mm; d90 < 0.92 mm. 1858782 of 17 [Table 6] Reference lot Day Tonnage Energy Consumption 1 127.1 100.1% 2 127.1 100.2% 3 127.3 101.7% 4 128.2 99.6% 5 128.2 98.0% 6 126.7 99.9% 7 132.1 100.8% 8 134.7 99.7% Average 128.9 100.0% Production using the reference lime yielded an average output of 128.9 tons per day over 8 days and an energy consumption in methane gas equivalent corrected for temperature and pressure normalized to 100% by comparison with the following. Daily values ​​are not very representative due to significant inertia and the residence time of the materials in the kiln; averages over 5 days or more provide useful information. [Table 7] Lot 3 Day Tonnage Energy Consumption 1 135.0 97.7% 2 134.0 102.1% 3 131.8 103.4% 4 131.3 100.4% 5 121.2 104.0% 6 133.7 96.1% Average 131.2 100.6% Production using lime from batch 3 yielded a run of 131.2 tons per day over 5 days and an energy consumption per ton of molten glass of 100.6% compared to the reference lime. The difference in consumption is not very significant, except that consumption was expected to be slightly lower than 100%. Indeed, with identical raw materials, higher production implies higher melting rates without proportionally increasing furnace heat losses, resulting in lower energy consumption per ton of molten glass. Furthermore, maintaining the furnace at a constant temperature with no production consumes energy, and as production increases, this maintenance energy cost is divided by a larger number of tons, resulting in a lower overall energy consumption per ton of molten glass. 1858782 of 17 [Table 8] Lot 4 Day Tonnage Energy Consumption 1 116.4 99.4% 2 120.2 104.1% 3 128.3 97.0% 4 128.2 103.6% 5 125.7 100.1% 6 127.2 99.3% Average 124.3 100.6% Production using lime from batch 4 during days 1 to 6 resulted in a daily output of 124.3 tons and an energy consumption of 100.6% per ton of molten glass. Compared to the reference lime, the energy consumption per ton is very close, and the output is 3.57% lower, while the energy consumption per ton was expected to increase by several percentage points. Compared to batch 3, the energy consumption per ton is identical, and the output decreases by 5.53%. Given this decrease in output, a significant increase in energy consumption per ton was expected. [Table 9] Day Tonnage Energy Consumption 7 138.0 92.3% 8 138.0 91.7% 9 120.0 106.5% 10 123.0 103.8% 11 132.0 101.4% 12 138.0 93.6% 13 138.0 93.8% 14 138.0 93.4% 15 135.0 93.5% 16 125.0 99.1% 17 125.0 99.8% 18 125.0 97.7% Average 131.3 97.2% Production using lime from batch 4 between days 7 and 18 yielded a throughput of 131.3 tons per day and an energy consumption of 97.2% per ton of molten glass. Compared to the reference lime, energy consumption per ton is down by 2.8% and the throughput is up by 1.86%. Regarding batch 3, the production run is almost identical, and energy consumption per ton has decreased by 3.40 percentage points. Such a decrease in energy consumption per ton is unexpected. From another point of view, assuming that energy consumption by The energy consumption per ton of 1858782 tons evolves linearly with the production run. A run of 128.9 tons would correspond to an energy consumption per ton of 98.4%, that is, a decrease of 1.60 percentage points. However, it is generally considered in glassmaking that a coarse raw material melts more slowly than a fine raw material and therefore requires a higher energy consumption per ton of molten glass. This expected behavior is illustrated by batch 3, which, for a production run increasing by 1.78%, shows an energy consumption per ton increase of 0.6%. The same behavior was expected for batch 4. However, the energy consumption per ton of batch 4 decreases by 3.40 percentage points compared to batch 3. This difference is considerable and difficult to explain. One hypothesis would be better heat transmission within the raw materials due to the flattened shape of the lime grains. The temperature in the daily mixing hopper is lower with batch 4 than with the reference batch. The temperature is around 37 / 38°C. Dust emissions into the ambient air are significantly decreasing. Dust emissions from the kiln are evaluated by a 24-hour measurement using a cooled paddle positioned above the regenerators. On average, during this test with quicklime from batch 4, 84 mg of dust per ton of molten glass were collected on this pallet, compared to an average of 100 mg / ton of molten glass in the reference batch of quicklime. Furthermore, the chemical analysis of the collected dust shows a 50% decrease in its CaO content, indicating that this difference in dust content stems from changes in the behavior of the quicklime in the kiln. Next, an industrial test A was prepared. Identical mixtures were prepared using quicklime from batch no. 4. This time, the quicklime was introduced directly into the mixers, disregarding the introduction delay stipulated by WO2019002802, and delivered to the same kiln. The temperature of the mixture was measured at 22°C at the mixers, 25°C in the delivery truck at the workshop entrance, and 27°C in the kiln's truck receiving hopper. There was no noticeable dust emission during unloading from the truck into the hopper. These mixtures were introduced into the kiln, with a measured mixture temperature of 37°C, without causing any problems. The test corresponds to approximately 2 hours of kiln operation. During test B, the furnace was fed continuously for approximately 30 hours with an iso composition. The preparation of the mixtures was Test 1858782 of 17 was carried out with quicklime from batch no. 4, without any waiting period before the quicklime came into contact with the other wet raw materials. This long-term test confirmed the good handling conditions of the mixtures both in the mixing workshop and in the production area (no dust emissions along the conveyors, elevators, vibrating feeders, kiln loading, etc.) and the absence of any observed temperature rise, either in the mixing workshop or in the kiln, whether the measurement was taken in the receiving hopper with measured temperatures ranging from 25 to 31°C or in the daily hopper with measured temperatures ranging from 30 to 45°C. This observation is valid regardless of the moisture content in the mixture: 1.4% at the start of the test, 2.5% in the last 3 batches. The continuous recording of the temperature of the composition at the level of the hopper immediately above the kiln shows in parallel an increased stability of this parameter with respect to operation with quicklime from the reference batch. No anomalies in the operation of the oven were detected during this test. To complete these industrial tests, laboratory experiments have been carried out to confirm the behavior of this quicklime from batch no. 4. These studies were carried out by preparing a vitrifiable mixture of soda-lime glass in a test mixer (concrete mixer) according to the following operating procedure: - Humidification of a dry sand to the desired moisture percentage by incorporating water, and mixing for 180 s. - Simultaneous incorporation of sodium carbonate, alumina, dolomite and quicklime into the moistened sand, and mixing for 120 s, with a cover over the concrete mixer. All materials have been weighed in order to reproduce on a reduced scale a standard soda-calcium mixture of the Applicant. Two distinct and complementary approaches have been carried out: - Quicklime / wet raw material reaction study: the temperature of the vitrifiable mixture after preparation was recorded by inserting a thermocouple into the core of the material. The starting temperatures were the same for all tests. For a low sand moisture content of 1.3% and lime from batch no. 4, no reaction was observed (curve in thin dotted lines with reference “test 15” figure 3), which reinforces the industrial tests. This The result from test 1858782 of 17 should be compared to the curve of the reference lime at 1.6% sand moisture (clear solid line curve with reference “test 14”), which reaches 40°C in approximately 5 to 6 minutes. Considering a higher sand moisture content of 4.8% and the lime from batch #4, an exothermic reaction is observed (long dashed curve with reference “test 17” in Figure 3), reaching 40°C in approximately 10 minutes. This increase is clearly slower than for the quicklime from the reference batch at 4% (mixed dashed curve with reference “test 16”) and 6% (thick dashed curve with reference “test 3”) sand moisture. These two reference lime tests with 4% and 6% sand moisture show a strong and rapid temperature increase within a few seconds.The test with 3% moisture content (short-stroke curve, referenced as "test 3b") of the reference sand and lime shows intermediate behavior but with a higher temperature than test 17 between 10 and 60 minutes after mixing. In other words, temperatures of 40, 50, and 60°C are reached faster with test 3b than with test 17. The lime test from batch no. 4, with a moisture content of at least 4.8%, is suitable for industrial tools. Dust measurement / dust emissions: The mixtures were prepared according to the same operating procedure. Dust emissions from the concrete mixer were measured by regularly rotating the mixer (every 15 minutes) to simulate handling of the mixture (transfer, passage through a vibrating inlet, etc.). This measurement was carried out using a dust measuring device and lasted approximately 3 hours and 30 minutes; this duration allows for the possibility of temporary storage of the mixture in the storage containers before kiln feeding. A comparison of the records obtained using quicklime from the reference batch and quicklime from batch 4 shows a very clear improvement when using quicklime from batch 4: a reduction of at least 50%, and even 90%, in dust emissions (the graphs in Figure 4 are on the same scale; the decrease in the amplitude of the peaks indicates lower dust emissions) regardless of the water content in the sand, for values ​​of 3% and 6%. Therefore, a water content in the sand between 2% and at least 7% is considered. Quicklime with a low percentage of fines offers advantages for the preparation and handling of vitrifiable mixtures, significantly reducing dust emissions into the ambient air. Its large particle size helps limit the exothermic hydration reaction due to the lower concentration of particles. 1858782 of 17 exposed surface. Unexpectedly, the layer of hydrated lime created on the surface of the quicklime grains by contact with the water present in the other materials, particularly the sand, does not appear to contribute to the dust in the feeding and storage units located above the kiln. For this reason, this raw material can be applied without observing a waiting period for the quicklime to come into contact with the other wet raw materials. 1858782 of 17 Federico Aulmann - 20219535830 Digitally signed by PORTALTRAM ITES - INPI Date: 2022.07.07 15:54:43 -03:00 Reason: Digitally Signed by the INPI Location: Buenos Aires, Argentina 1858782

Claims

1. A method for preparing a glassmaking raw material mixture for a glass furnace, characterized in that it comprises the preparation of a glassmaking raw material mixture for a glass furnace, in which water, sand, and sodium carbonate are mixed in mass proportions of between 0 and 5%, 40 and 65%, and between 0 and at most 25%, respectively, and secondary glassmaking raw materials, and, within less than 10 minutes, preferably simultaneously, calcium oxide and optionally calcium carbonate are incorporated in a mass proportion of between 1 and 20% of the total, the calcium oxide having a particle size distribution such that more than 97% by mass does not pass the 0.125 mm sieve, more than 96% by mass does not pass the 0.5 mm sieve, and preferably more than 95% by mass does not pass the 1 mm sieve. Sixteen claims follow.