The main reasons for damage to the refractory lining of the gasifier furnace mouth are as follows. The thermal stress is too great. Due to the cooling effect of the Texaco burner cooling coil, the upper part of the furnace brick is maintained at a relatively low temperature, while the lower part of the furnace brick is maintained at a higher temperature due to the influence of high temperature radiation and high temperature gas convection in the furnace . Because the temperature difference between the upper and lower ends is very large, it is easy to cause the thermal stress of the furnace brick to be too large and crack.
Excessive driving and parking. During normal production, the temperature of the refractory lining of the furnace is relatively high, and the furnace mouth is refractory due to the cooling effect of the cooling coil of the burner (or the entry of a large amount of cold air) during parking (especially in the case of hanging the burner). The temperature of the lining dropped sharply, and the temperature rose quickly after driving. One stop is equivalent to one quick cold and one hot. According to the test results, the corundum bricks were cracked after being quenched and heated 4 times. From the commissioning at the end of 1983 to the fifth shutdown and overhaul in April 1991, the two gasifiers have been turned on and off 195 times in total, and each gasifier has been turned on and off once on average at 19.4 days. Such frequent opening and parking causes frequent rapid cooling and heating of corundum bricks and serious damage. In addition, during parking, the furnace is filled with steam. Due to the cooling effect of the burner cooling coil, condensate is easily generated at the furnace mouth, and the corrosion of condensate, carbon black, slag, etc., can easily cause spalling and pouring of corundum bricks. The material is damaged due to failure or carbonization.
The expansion joint on the furnace roof is too small. In actual use, it was found that the corundum brick and castable damaged in the furnace mouth were higher than the flange surface, and the ceramic fiber felt was pressed into a flat sheet shape. This shows that the height of the expansion joint of the original designed furnace top of 40mm is not enough, and the theoretical calculation also proves that the expansion joint is too small. In this way, the expansion of corundum bricks is hindered by strong pressure and easily damaged.
Improvement measures Since January 1988, improvement measures have been taken on the refractory lining of the gasifier and gradually improved according to the use effect. After repeated trials, the following relatively complete measures were finally taken. The furnace mouth corundum brick is changed from three rings to five rings, and the height of the single furnace mouth brick is changed from 123mm to 70mm, thereby reducing the thermal stress of the corundum brick and reducing the possibility of cracking of the corundum brick; the furnace mouth corundum brick is used The mortar is changed from alumina fire clay with high sintering temperature to third-layer insulation brick fire clay with relatively low sintering temperature, and the joint surface of furnace corundum brick and corner brick is changed from flat surface to tenon groove surface. Avoid channeling gas from this area.
White corundum with a height of 50mm is poured into the annular gap between the furnace brick and the shell to seal the refractory castable. Corundum is added with stainless steel wire as a skeleton to ensure the overall strength of cast corundum. Insulate bricks above the cast corundum to double-close the castables to prevent the castables from being damaged. According to the expansion coefficient of the corundum brick used, the axial expansion of the entire corundum brick lining is calculated, and the appropriate expansion joint height is selected to make the furnace roof expansion joint height reasonable, so as to avoid the refractory lining expansion from being blocked and generating strong pressure.
Since June 1992, the above measures have been adopted in the gasification furnace refractory lining, the usage of the furnace refractory lining has fundamentally improved, the cracking of the furnace mouth brick and the runaway of the casting material have been basically eliminated. The phenomenon of over-temperature alarm on the outer wall of the furnace mouth has also been eliminated. The use of the improvement measures for the refractory lining of the combustion chamber Judging from the inspection of the refractory lining of the gasifier in each overhaul, the thinning of corundum bricks on the top of the gasifier arch and the upper part of the barrel is not large (generally 1030mm, the remaining thickness is 80110mm ), and the corundum bricks in the middle and lower parts of the cylinder are eroded by the burner flame, and the thinning speed is very fast. There are few or even no corundum bricks used in less than 8000h. For example, in No. 2 gasifier in 1989 and 1990, the upper corundum bricks collapsed due to the thinning of corundum bricks in the lower part of the cylinder to zero, and Zibo electric drums were forced to carry out overhaul in advance. From 1990 to 1991, the thinning rate of corundum bricks was as high as about 10mm per month on average, making it difficult to guarantee a production cycle.
Causes of damage The main reasons for the damage of corundum bricks in the slag oil gasifier are the following. Melt loss. Ni, V, Ca, Na, Fe, Mg and other impurities contained in the raw residue oil used in the gasifier react with the alumina brick component Al2O3 to form a low-melting compound, which is melted and lost at the operating temperature. The amount of loss increases as the process operating temperature increases and the process gas flow rate increases. Flaking. Impurities contained in the raw material of the gasification furnace penetrate into the brick through the open pores of the corundum brick, and the rock wool reacts with the components of the brick to generate new minerals. Due to different thermal expansion coefficients or body transformation effects (such as V2O3 meeting O2 to generate V2O5, the volume increases by 40%), in the case of furnace temperature fluctuations, especially when opening and closing, slag cleaning, and hanging burner, at the junction of different minerals Cracks are generated and continue to expand, and finally flake off in flakes or blocks. The greater the temperature fluctuation, the more the number of opening and stopping, and the greater the amount of flaking.
Damage caused by accident. Such as burner nozzle damage, burner cooling water coil leakage, burner installation misalignment, over-temperature of oxygen, damaged chill ring, chilled water overflow into the combustion chamber, etc. The quality of refractory materials such as corundum bricks is poor, the quality of construction masonry is not close, and the quality of the oven is poor. The improvement measures have made improvements to the refractory lining while attacking the above aspects. The reason for the replacement of the refractory lining of the gasifier is that the corundum bricks in the lower part of the combustion chamber barrel are damaged or thinned seriously, while the thickness of the corundum bricks in the upper part of the barrel and the top of the arch is still large, so as long as the melting loss is reduced, the fastest thinning barrel The thickness of the corundum brick at the lower part of the body can extend the service life of the corundum brick at this part, and the service life of the refractory lining of the entire gasification furnace can be prolonged.
Conclusion After several years of efforts, after taking the above improvement measures, the refractory lining of the gasifier furnace port is easily damaged, resulting in overtemperature of the outer wall of the furnace port, short service life of the corundum brick in the lower part of the combustion chamber barrel, and the outer wall of the thermocouple hole is easy to overtemperature, etc. The problem has been basically solved, greatly reducing the load reduction production and shutdown maintenance caused by the gasifier. Then through the reasonable allocation of residue oil types, the optimization of process operations, the quality of lining masonry and the improvement of the quality of corundum bricks produced by the Luoyang Refractory Research Institute, the service life of the thickened corundum bricks of the gasifier has met the two-year repair The need to solve this major problem that plagues the production of fertilizers has created good conditions for the stable and stable production of large fertilizer plants.
