In recent years, in order to reduce the cost of refractory materials for glass melting furnaces, glass companies have used a large number of old fused bricks in the cold repair of the furnace. However, due to the lack of strict requirements during use, the cold repaired furnace quickly appeared fire and leakage. The problems of material, fast erosion, etc. shorten the service life of the furnace. This article explains in more detail the requirements for using old fused bricks in the cold repair of glass melting furnaces, which has certain guiding significance for small and medium glass enterprises to conduct cold repairs in melting furnaces.
1 Selection and processing of old fused bricks
The "General Regulations for the Design of Daily Glass Furnace" has clear requirements on the type and quality of fused bricks used in various parts of the glass melting furnace. The old fused bricks will inevitably be corroded, burnt, and exploded due to the erosion of molten glass or the erosion of high-temperature flames. They must be selected when reused and processed as required.
(1) Preparation before processing
a. Before purchasing the old fused bricks purchased by the enterprise, the appearance and quality should be strictly inspected, and samples should be sent to the national refractory material quality supervision and inspection unit to issue a quality inspection report to avoid affecting the quality of the molten glass or premature burning.
b. If the company’s own old fused bricks need to be used on the pavement, pool wall and other parts that directly contact the molten glass, their chemical composition should be checked to prevent their composition from affecting the molten glass in the melting furnace after cold repair.
c. Before processing, all old fused bricks should be classified according to the categories of 33# non-shrinkage, 33# ordinary casting, 41# non-shrinkage, etc., and stack them on site by area.
d. Sort out all the classified old fused bricks, mark the serial number, measure the size and record.
e. Familiar with the drawings of melting furnace fused bricks, especially the types of fused bricks in various parts, the overall size of the assembly, and the size of the individual drawings.
f. According to the design requirements of the drawings, select suitable old fused bricks for processing.
g. Select the diamond saw blade with the appropriate diameter according to the size of the fused brick in the drawing.
h. Equipped with a dedicated cutting and grinding brick machine.
i. Equipped with professional measuring tools.
j. Prepare cooling water.
(2) Processing requirements
a. The part of the working surface with glass slag, metal and other sundries must be cut off.
b. The ablated part of the working face must be cut off.
c. The mouse hole part of the working face must be cut off.
d. The part of the working surface eroded by glass liquid must be cut off.
e. The corners and broken parts of the working face must be cut off.
f. Ensure that the overall dimensions of the assembly drawing and the appearance quality meet the requirements of Table 1.
Table 1. The appearance quality and size deviation of old fused bricks
(3) Requirements after processing
a. All processed old fused bricks shall be pre-assembled in the assembly area and revised according to the design requirements of the drawings.
b. When matching new bricks with old bricks, carefully consider the arrangement of bricks and the setting of expansion joints.
c. The old fused bricks that meet the requirements should be handled with care when they are transported to the site, especially in the hoisting process, using suitable pallets and packaging.
2 Masonry of old fused bricks
2.1 Pool floor tiles
Pool bottom paving bricks should be made of 75-150 m thick non-shrinkage fused cast zirconium corundum bricks and ground paving paving bricks. The ramming material must be basically the same crystal phase as the paving bricks, and it can be combined with the paving bricks to form an airtight and indivisible whole. Because old paving tiles are directly in contact with molten glass, they are affected by both the downward drilling of the metal and the upward drilling of the molten glass. The mineral phase composition and chemical composition of the parts in contact with the molten glass have changed. Therefore, the use of old fused bricks must be The part affected by glass erosion. The ramming material must be crushed from the original brick, or newly purchased ramming material whose crystal phase is basically the same as that of 33# non-shrinkage fused brick.
The paving bricks at the bottom of the masonry pool shall be operated in accordance with the following requirements:
(1) Pave the AZS 0 6 mortar on the ground of the polished AZS 50 ramming material, with a thickness of 5 m m, and use a ruler to smooth it. The paving area can accommodate a paving brick, and then the paving brick is immediately laid. AZS 0 6 Mud shall not be stored in the joints of the bricks.
(2) The joints of the paving bricks are filled with AZS 04 mud. The mud that flows out must be cleaned up. The construction personnel must keep it clean during the operation and do not bring in any impurities.
(3) Pave according to the size of the drawing, and the vertical and horizontal seams should be aligned. The width of the brick joint is not more than 2 mm in the length direction and not more than 1 mm in the width direction. The level of the bottom of the pool is ±2.5 mm.
2.2 Pool wall tiles
The pool wall should be made of a whole block of basically non-shrinkage-free fused cast zirconium corundum bricks vertically arranged and ground; when the double-layer pool wall is adopted, the upper layer of the fused cast zirconium corundum bricks with oblique casting is prohibited, and no shrinkage cavities should be used. ; The joints of the upper and lower pool wall tiles after grinding should not be larger than 0.3 mm to reduce the upward drilling erosion of the upper pool wall tiles by the glass liquid. After the kiln is stopped and discharged, the company should carefully check the damage to the pool wall bricks. For example, the pool wall bricks have been eroded seriously up and down, and the lower part has a "hill slope" with upward drilling erosion. The overall thickness is very thin, and there may even be fractures and material leakage. In this case, the whole brick replacement method must be selected (see Figure 1). This method requires the use of new bricks, and its masonry requirements are in accordance with GB50211-2004 "Code for Construction and Acceptance of Industrial Kiln Masonry Engineering" row. If the pool wall tiles are only eroded seriously at the upper part of about 0~400 mm, and the lower part is intact, a horizontal cutting scheme can be used (see Figure 2). The operating conditions and technical requirements of this method are as follows:
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Figure 1. Pool wall bricks that need to be replaced by whole bricks
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Figure 2. Pool wall tiles that can be horizontally cut and reused
(1) Horizontal cutting conditions: The cutting and grinding brick machine adopts a movable type. The diameter of the diamond circular saw blade is determined according to the size of the pool wall brick. The main shaft needs to be able to be supplied horizontally and vertically. The brick cutting machine needs to be equipped with a track to move in the kiln to ensure the level of the brick cutting machine, and it is also equipped with cooling water.
(2) Technical requirements for horizontal cutting: After the brick cutter cuts off the most severely corroded part of the upper part of the pool wall from 0 to 400 mm, replace it with a new non-shrinkage electric fusion brick. The horizontal construction brick gap should not exceed 0.3 mm. After replacing the new bricks, all brick joints should be closed with tape immediately to prevent debris from entering the brick joints. The lower part of the pool wall should be treated with glass slag before baking, and the inside of the pool wall should be kept smooth and even.
2. 3 Breast wall, small furnace
The breast wall and small furnace of the melting part should be oxidized cast zirconium corundum bricks with low glass phase exudation. The transverse joints of the wall bricks should not exceed 0.3 mm, the vertical joints should not exceed 0.5 mm, and the gaps between the trellis bricks should not exceed 0.3 mm. Staggered seams should be made between the ring and ring of the dome and flat dome, and the upper and lower layers of the wall bricks shall be staggered. When the breast wall is high, the bottom row of bricks should be enlarged to support the upper part to prevent the breast wall from collapsing; because the front wall is relatively high, two rows of longer bricks need to be set in the middle to extend into the insulation wall to prevent the wall from collapsing.
When using old fused bricks to build breast walls and small furnaces, the pouring port must face outwards, not toward the flame space. The surface of the casting port needs to be processed and smooth, and 5 mm AZS 06 joint material is filled between the fused brick and the high alumina brick and compacted. The vertical deviation of the breast wall and the side wall of the small furnace is 1/1000, and the elevation allows ±2 mm. For the junction of silica brickand fused brick, zircon refractory mud or low creep and crack resistant zircon brick (T0.6>1 700 °C) must be used for transition.
2. 4 Gas Tongue
It is advisable to use the oxidation method to cast zirconium corundum bricks with low glass phase exudation for the tongue of the small furnace. When cold repairing, enterprises can choose to use old non-shrinkage fused bricks for masonry. The 4 sides of the dome bricks shall be smoothed and the joints between the dome bricks shall not exceed 0.3 mm.
When masonry tongue mortar bricks, mullite bricks with phosphoric acid infiltration and with an infiltration time of more than 2 h can be used for tongue mortar bricks. The contact surface of mortar bricks and mortar bricks and wall contact surfaces need to use 3 ~ 5 mm ZrO2 65.5% fire. In the mud transition, the gaps between the mortar bricks are filled with AZS 0 4 ramming material, and a layer of AZS 50 ramming material is laid on the entire tongue mortar and tamped. At the contact point between the tongue clasp and the wind and fire wall, an expansion joint is required. If the upper wall of the regenerator is made of high-quality silica bricks, it must be transitioned with zirconium refractory mud or low-creep and crack-resistant zircon bricks (T0.6>1 700 ℃).
3 Conclusion
Using old fused bricks for cold repair of glass melting furnaces is an effective way for enterprises to reduce costs. Enterprises should carefully screen, finely process and strictly construct in the process of using old fused bricks. However, in order to ensure the normal use and age of the melting furnace, enterprises should still use new fused bricks in key parts such as the corners of the feeding inlet, kiln sills, and flow caves that are vulnerable to corrosion. After the kiln is put into production, the maintenance and scientific management must be strengthened to achieve the purpose of reducing the cost of the kiln and prolonging the age.
