Study of the Effect of Temperature on the Granulation of Glass Batch
Abstract Generated abstract
This study examines how batch temperature affects the granulation of raw materials for window glass, focusing on the role of crystalline hydrate decomposition in improving plasticization and pellet formation. Production batch components from the Anzhero-Sudzhensk glass plant were granulated under ordinary laboratory conditions and at 70°C, then compared by pellet yield, density, crushing strength, and moisture content. Heating the batch to 70°C allowed the granulation time to be reduced from 10 to 5 minutes while increasing the yield of pellets larger than 3 mm, raising granule density and mechanical strength, and lowering moisture content by about 10 to 11 percent. The results support regulating temperature along the batch preparation line as a means to intensify granulation and improve product properties.
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INVESTIGATION OF THE EFFECT OF TEMPERATURE ON THE GRANULATION OF GLASS BATCH
V. M. Vityugin, V. A. Trofimov, L. G. Lotova, G. S. Smirnova
(Submitted by the scientific seminar of the Department of GCT)
The use of granulated batch for glass production increases and stabilizes the homogeneity of the glass, improves melting conditions, and significantly prolongs the service life of tank furnaces. The literature has reported various aspects of the granulation of glass batches [1, 2, 3, 4]. However, the usual technological methods of batch granulation are of low productivity. This occurs because, in the glass batch on the working surfaces of granulators, processes opposite in character take place. On the one hand, during rolling the batch is compacted, while on the other hand the forming aggregates are loosened owing to the formation of decahydrate crystalline hydrates of soda and sodium sulfate.
The formation of crystalline hydrates is determined by the temperature conditions of the granulation process. It is known [5] that at temperatures above 30°C crystalline hydrates decompose with the release of part of the water of crystallization and the melting of the remaining crystalline hydrate in the released water. This phenomenon promotes the plasticization of the batch and leads to a substantial increase both in the granulation rate and in the density and mechanical strength of the granules formed. Under production conditions, especially in winter, the principal component of the glass batch—quartz sand—is subjected to drying. In this case the temperature of the dry sand is usually 80–90°C. Depending on the conditions and time of transportation, dosing, and mixing of the batch, the hot quartz sand transfers to it a certain amount of its thermal energy. As a result, the temperature of the glass batch may be either below or above the critical temperature of decomposition and melting of the crystalline hydrates.
The purpose of the present work was to make a quantitative assessment of the influence of the temperature effect on the process of granulating glass batch for the production of window glass. Production samples of batch materials from the Anzhero-Sudzhensk glass plant were used as the objects of study. The characteristics of the raw-material components are given below: Tashlinskiy quartz sand, particle size 0.25–0.0 mm, SiO₂ content—98%, proportion in the batch—54.8%; dolomite from the Zaigraevo deposit, particle size 0.5–0.0 mm, CaO + MgO content—59%, proportion in the batch—17.3%; feldspar concentrate, particle size 0.5–0.0 mm, R₂O + Na₂O content >10%, proportion in the batch 5.23%; calcined soda, particle size—
with a particle size of 0.5–0.0 mm, Na₂CO₃ content 99.2%, proportion in the batch 15.9%; sodium sulfate with a particle size of 0.5–0.0 mm, Na₂SO₄ content 99.5%, proportion in the batch 5.27%; sodium silicofluoride with a particle size of 0.5–0.0 mm, Na₂SiF₆ content 98.8%, proportion in the batch 0.7%.
The method for preparing the batch was analogous to production conditions: sand—water—feldspar—soda—sodium silicofluoride—sulfate—dolomite. After thorough mixing, one part of the sample was pelletized under ordinary conditions on the pan of a laboratory granulator for 10 minutes. The other part of the sample was pelletized on the pan of the same granulator at a temperature of 70°C for 5 min. Heating of the batch on the granulator was carried out by means of a 500-watt radiation lamp. After granulation, the sieve composition of the granulate, the density of the granules, and their strength (by crushing load, g/granule) were determined for the average class of pellets, 5–7 mm.
The averaged and generalized results of the investigations are given in Table 1.
Table 1
Comparative results of granulation of glass batch
| Average granulation time, min | Granule yield, +3 mm, % | Average strength of granules, g/granule after 1/2 h | Average density of granules, g/cm³ after 1/2 h | Average moisture content of granules, % | Average granulation time, min | Granule yield, +3 mm, % | Average strength of granules, g/granule after 1/2 h | Average density of granules, g/cm³ after 1/2 h | Average moisture content of granules, % |
|---|---|---|---|---|---|---|---|---|---|
| Ordinary granulation methods | Ordinary granulation methods | Ordinary granulation methods | Ordinary granulation methods | Ordinary granulation methods | Granulation at a batch temperature of 70°C | Granulation at a batch temperature of 70°C | Granulation at a batch temperature of 70°C | Granulation at a batch temperature of 70°C | Granulation at a batch temperature of 70°C |
| 10 | 85.3 | 1880 | 1.78 | 23.1 | 5 | 91.0 | 2503 | 2.3 | 12.4 |
| 10 | 79.8 | 1744 | 1.87 | 23.4 | 5 | 89.1 | 2140 | 2.17 | 13.5 |
| 10 | 81.2 | 1654 | 1.69 | 22.7 | 5 | 87.9 | 2380 | 2.09 | 12.1 |
| 10 | 88.7 | 1910 | 1.81 | 24.1 | 5 | 81.2 | 2120 | 2.03 | 11.7 |
As can be seen from Table 1, when the granulation rate at a temperature of 70°C was increased by a factor of 2, the average density and mechanical strength of the granules increased by a factor of 1.2 in comparison with the ordinary method of granulation. The moisture content of the granules at a temperature of 70°C decreased by 10–11%.
Conclusions
Thus, regulation of the batch temperature makes it possible to intensify the granulation process to a significant extent, while substantially reducing the moisture content of the finished product.
From this point of view, strict regulation of the temperature regime along the raw-batch preparation line is advisable.
References
- M. E. Guryanova. Steklo i keramika, No. 5, 1959.
- M. E. Guryanova. Steklo i keramika, No. 10, 1961.
- B. K. Demidovich. Abstract of Candidate’s dissertation, Minsk, 1967.
- H. Löfler. “Granulation of batch,” Glastechnische Bericht, 193, 1951. (FRG).
- L. G. Melnichenko. Steklo i keramika, No. 11, 1954.