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Application of integral casting technology for coke oven door lining

Application of integral casting technology for coke oven door lining

Abstract: In view of the shortcomings of the original brick coke oven door, such as short service life, difficulty in repair, easy heat dissipation, and easy slag adhesion, the causes of damage to the door lining were analyzed and studied. It is proposed to improve the furnace door lining structure, develop new materials and adopt integral casting method. Coating the lining surface of the furnace door with an anti-slag agent can effectively prevent coking and slagging on the lining of the furnace door during the coking process. It can increase the service life of the coke oven door by more than 2 times, reduce heat loss and reduce the labor intensity of workers, and ultimately achieve the goals of production safety, energy saving and longevity.

Keywords: integral casting; energy saving; longevity

Overview

At present, domestic coke oven doors mostly use clay bricklaying technology. During actual operation, the coke oven door lining bricks have to withstand relatively severe temperature changes, with the working temperature alternating between 1200°C and ambient temperature. It also has to bear the friction with the coke when pushing the coke, as well as the erosion of ash, slag, moisture and acid gas and the deposition of carbon. When cleaning up the sticky slag such as carbon, the coke oven door lining brick will also be damaged. Due to the high thermal conductivity of clay bricks, generally in the range of 1 to 1.28W·(m·K)-1, the surface temperature of the coke oven door is high and the heat dissipation loss is large.

The coke oven doors of Laiwu Iron and Steel Co., Ltd. currently use this clay brick-laying process, but there are the following problems in use: (1) The brick-laying oven door lining has many brick joints, which is prone to coking, serious erosion, and short service life. (2) The thermal insulation effect is poor, the temperature outside the coke oven door is 150°C on average, sometimes reaching 260°C; (3) The sealing effect is average, and some flue gas leaks. At present, some developed countries at home and abroad use large-scale prefabricated bricks for coke oven doors on the coke oven machine side and coke side. The bricks have good thermal insulation effect, strong sealing, energy saving and environmental protection, and long service life. However, it is difficult to install and replace large-scale prefabricated blocks, which increases labor intensity. To this end, we have studied the integral pouring technology for the coke oven door lining. After more than a year of production practice, the results have been remarkable.

Tests

Main raw materials

Mullite was selected as the main raw material in this experiment. Aluminate cement is used as the binding agent, silica powder and alumina powder are used as fine powder, a small amount of andalusite is added as an expansion agent to reduce the shrinkage of the coke oven door, and composite polyphosphate is added as a water-reducing agent.

Test plan and performance testing

Raw material ratio: 30% to 40% of M60 mullite with particle size ≤0.088mm. 15%~20% of M60 mullite with a particle size of 1~3mm. M60 mullite with particle size 3.1~8mm is 30%~35%; steel fiber is 1%~3%; high alumina cement with particle size ≤0.088mm is 1%~4%. 5%~8% of silica powder with particle size <0.5μm; 4%~7% of alumina powder with particle size <0.5μm; 1%~5% of andalusite with particle size ≤0.045m.

After many tests and optimization, the optimal ratio is: M60 mullite (≤0.088mm): 40%; M60 mullite (1~3mm): 15%. M60 mullite (3.1~8mm): 30%; steel fiber: 3%; high alumina cement (≤0.088mm): 4%. Microsilica powder (<0.5μm): 3%; alumina powder (<5μm): 3%; particle size ≤0.045mm andalusite: 2%; plus 0.2% sodium tripolyphosphate and 8.5% water.

The optimized proportion of raw materials was made into 160mm × 40mm × 40mm sample blocks, vibrated into shape, naturally cured for 24 hours, and baked in a 110°C oven for 24 hours. The performance was compared with the original furnace door lining bricks. The results are shown in Table 1.

Table 1 Performance comparison

  Original ratio New ratio
Bulk density/(g·cm³)(110℃,24h) 2.15 2.24
Compressive strength/MPa(110℃,24h) 33.9 37
Flexural strength/MPa(1200℃,3h) 7.6 10.2
Porosity/%(110℃,24h) 15.5 14.5
Thermal expansion coefficient/%(1000℃,3h) 0.46 0.38

After testing the above formula, the results show that the new ratio can meet the requirements of the coke oven door lining, so the new formula is selected as the material for the coke oven door lining.

Industrial application test

At present, most coke oven door linings in China adopt bricklaying technology, and the overall casting is also made of large prefabricated blocks spliced together. Such large prefabricated blocks are difficult to assemble and disassemble due to their heavy weight, and if one is broken, adjacent prefabricated blocks will also be damaged during the disassembly process, so it is not economical and reasonable. Based on research on large-scale prefabricated blocks, we developed an integral pouring process for the coke oven door lining.

Overall casting process

1) Place the coke oven door flat, clean the inside, and lay two layers of insulation material on the bottom, close to the bottom of the coke oven door.

2) Install the coke oven door mold and fix it.

3) Weigh 1.7t of castable and mix evenly with a certain particle size distribution.

4) Add 7% water, stir for 5 minutes, and pour into the oven door mold.

5) The vibrating rod vibrates to eliminate air bubbles and make the castable material even and smooth.

6) After the surface is smooth, maintain it in the mold for 24 hours.

7) Baking: Place it in a 6m kiln at 300°C for 48 hours, then leave it for 24 hours.

Research and application of anti-slag agents

The furnace door lining bricks are in the carbonization chamber of the coke oven. The produced coke will adhere to the lining bricks, and tedious procedures are required to remove carbon. Moreover, there is also certain mechanical damage and chemical erosion to the lining bricks, especially for the lightweight furnace door lining bricks with large porosity, these two situations are more serious.

An anti-slag agent with glassy glaze as the main component has been developed. Its main features are as follows.

1) The porosity is zero and there is no permeability to foreign objects, which can resist carbon deposition.

2) The anti-slag agent has the same thermal expansion coefficient as the base casting material, and is slightly smaller than the thermal expansion coefficient of the base lining bricks.

3) The anti-slag agent has good thermal stability and mechanical stability, which can protect the lining bricks and prevent the chemical erosion of the lining bricks by coking products.

On the surface of the baked oven door, apply anti-slag agent with a thickness of no more than 0.5mm. After painting, maintain it at room temperature for 24 hours. It is enough to ensure that there are no cracks on the surface.

Furnace door temperature measurement

In order to determine the thermal insulation of the coke oven door, a far-infrared thermal imaging camera is used to measure the temperature of the coke oven door. The coke loading time of every four oven doors of the 4.3m coke oven in Laigang Coking Plant is the same, so the comparison oven doors are the oven doors that are loaded with coke at the same time. 41* and 74* are two integral cast coke oven doors, and the rest are brick coke oven doors. Mark three points on the upper, middle and lower parts of each coke oven door to measure the temperature. The results are shown in Tables 2 and 3.

It can be seen from the temperatures at the upper, middle and lower points of the coke oven door that the surface temperature of the integrally cast experimental coke oven door is 20°C ~ 30°C lower than that of the original brick coke oven door, which has a good energy-saving and heat preservation effect.

Table 2 Measurement data of outer wall temperature of coke side oven door

  41# 35# 30# 25# 20# Average temperature difference/°C
upper part 95.0 122.7 125.0 134.8 130.1 33.15
middle part 127.3 154.8 151.3 146.6 140.2 20.92
lower part 114.2 170.3 128.3 130.8 135.5 27

Table 3 Temperature measurement data of the outer wall of the machine side coke oven door

  74# 70# 66# 62# 58# Average temperature difference/°C
upper part 94.7 125.1 130.2 120.5 118.5 28.9
middle part 106.9 155.4 141.0 133.5 136.4 34.7
lower part 101.2 153.0 138.2 125.5 137.2 37.3

On-site use effect

Figure 1 and Figure 2 are the renderings of the brick coke oven door and the integral cast coke oven door after use. The use time is 1.5 years and 1 year respectively. However, it can be clearly seen from the picture that half of the lining of the brick coke oven door has been damaged, and the pouring coke oven door has only minor cracks and the surface is not easy to stick to slag. From the experimental results, it can be seen that the pouring coke oven door can meet the longevity requirements.

Figure 1 Brick coke oven door lining 1.5 years old

Figure 2 One-year-old integrally cast coke oven door lining

Conclusion

With the goal of improving the comprehensive performance of the coke oven door and saving energy, this article studies a new coke oven door material formula, formulates an overall pouring process, applies advanced insulation materials, and coats the surface with an anti-slag agent. After one year of field testing, the coke oven door has been used on the coke oven well, with no obvious cracks or falling off. Compared with brick-laying coke oven doors of the same period, its service life is 2 to 3 times that of brick-laying coke oven doors. The coke oven door temperature is about 20℃ lower than that of clay brick coke oven doors, meeting the requirements of energy conservation, environmental protection and longevity. The new integrally cast coke oven door is simple to construct and easy to repair, which reduces the frequency of coke oven door replacement and reduces the labor intensity of workers. As the temperature of the outer surface of the coke oven door decreases, the deformation of the iron parts of the furnace body is effectively prevented, the leakage of gas and tar is reduced, and the furnace body is protected. It also reduces heat loss and effectively saves energy. After applying anti-slag agent, the outer surface is less likely to form slag and is easy to clean, which reduces labor intensity and is beneficial to the surrounding environment and the health of workers.

Coking Equipment Manufacturer
coke ovens
coke oven door

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