On the Issue of Reducing Temperature Nonuniformity of the Glass Ribbon at the Anzhero-Sudzhensk Glass Factory
Abstract Generated abstract
This paper addresses temperature nonuniformity in the glass melt and forming ribbon during vertical drawing of sheet glass through a boat at the Anzhero-Sudzhensk Glass Plant. Based on thermocouple measurements in the conditioning zone and across the ribbon width, the authors identify several sources of transverse temperature differences, including asymmetric water supply to barrier coolers, uneven cooling near boat ends, scale formation, and cooling conditions in the machine shaft. They propose paired barrier coolers with two-sided water supply, direct temperature monitoring in the boat slot and ribbon, automatic temperature control linked to electric heating, modified box coolers with central water inlet and mesh baskets, and regulated water cooling near the moving ribbon. The reported measurements indicate that the revised cooler arrangement can substantially reduce melt temperature differences, with the proposed devices intended to improve sheet glass quality and output.
Full Text
ON THE ISSUE OF REDUCING TEMPERATURE NONUNIFORMITY OF THE GLASS RIBBON AT THE ANZHERO-SUDZHENSK GLASS PLANT
I. P. Chashchin, M. S. Landsman
(Presented by the scientific seminar of the departments of PMAChP and OKhT)
Maintaining isothermy in the glass melt, as well as in the glass ribbon being formed, in the production of sheet glass by the method of vertical drawing through a boat is one of the most important conditions for reducing striation, eliminating thickness nonuniformity, and reducing glass breakage [1, 2]. The direct flow of glass melt that forms after the barrier cooler at a distance of 0.2–0.5 m from it usually has a temperature nonuniformity across the width of up to 30–40°C. The barrier cooler, which is a pipe 3 inches in diameter, reduces convective glass exchange between the melting and conditioning basins [3], but, because water is supplied from one side, it promotes temperature nonuniformity across the width of the glass-melt flow.
The investigations we carried out to measure temperatures in the conditioning zone by thermocouples loaded on the 2nd system of the Anzhero-Sudzhensk Glass Plant are given in Table 1.
Instead of the cooler described above, we proposed, for this section of the furnace, coolers consisting of two pipes 3 inches in diameter, installed side by side and immersed halfway into the molten glass. Water was supplied to the coolers from two sides, and after appropriate adjustment they made it possible to reduce the temperature nonuniformity of the glass-melt flow.
The measurement results are given in Table 2.
Table 1
| Before the cooler | Before the cooler | After the cooler | After the cooler |
|---|---|---|---|
| left side | right side | left side | right side |
| 1285° | 1270° | 1250° | 1210° |
Table 2
| Before the cooler | Before the cooler | After the cooler | After the cooler |
|---|---|---|---|
| left side | right side | left side | right side |
| 1280° | 1265° | 1210° | 1205° |
The temperature nonuniformity of the glass-melt flows entering the slots of the boats for drawing is composed of the temperature differences created along the entire path of the flows: after the barrier cooler, increased heat removal from the sides of the flow relative to the center, the different path length from the center of the corresponding “cross” to the ends of the boat slots. More intensive cooling of the “onions” from the ends of the boat relative to the center, and uneven formation of scale on
on the walls of the coolers installed in the under-machine chamber [4, 5, 6], and the introduction of water into the coolers from the side of the edges further increases the temperature nonuniformity, which may reach 30–40°C in the glass ribbon.
We proposed that temperature measurements be carried out directly in the slot of the boat by drilling through the body of the boat and installing thermocouples directly in the slot; for the glass ribbon, by means of thermocouples built into one of the rollers of the fourth pair.
The results of the measurements we carried out of the temperature of the glass ribbon at the level of the 4th pair of rollers at three points across the width of the ribbon are given in Table 3.
Table 3
| Side | I | II | III | IV | V | VI | VII | VIII | IX |
|---|---|---|---|---|---|---|---|---|---|
| Machine | Machine | Machine | Machine | Machine | Machine | Machine | Machine | Machine | Machine |
| Temperature, °C | Temperature, °C | Temperature, °C | Temperature, °C | Temperature, °C | Temperature, °C | Temperature, °C | Temperature, °C | Temperature, °C | Temperature, °C |
| Right | 385 | 378 | 382 | 348 | 357 | 342 | 347 | 403 | 372 |
| Middle | 443 | 398 | 411 | 378 | 399 | 395 | 377 | 410 | 394 |
| Left | 373 | 357 | 389 | 330 | 355 | 348 | 344 | 364 | 349 |
Reducing the temperature nonuniformity of the incoming stream of glass melt into the boat slot is proposed to be achieved by automatically maintaining the temperature in this zone. The system consists of four thermocouples installed in the body of the boat, connected in pairs, and an indicating and amplifying unit connected to the electric-heating system for the glass melt. Maintaining isothermy across the width of the glass ribbon is proposed through a modified design of box-type coolers, which have a central water inlet; the coolers are placed in a basket made of coarse-mesh netting of brass or nickel, which, along with reducing temperature nonuniformity, diminishes the harmful influence of cold convection currents but does not impede heat exchange by radiation.
The temperature regime in the machine shaft is proposed to be regulated by supplying water to pipes installed directly on both sides of the moving glass ribbon (5 pairs of lifting pipes up to the 8th pair of rollers), according to the readings of an instrument connected to thermocouples built into one of the rollers of the machine.
All the above devices make it possible to increase the output of sheet glass and improve its quality.
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