New Type Oil Gasification Material Refractory Material Transformation

The main causes of damage to the refractory lining in the gasifier furnace are primarily due to thermal stress, frequent start-up and shutdown cycles, and inadequate expansion joints. Thermal stress occurs because the upper part of the burner bricks remains relatively cool due to the cooling effect of the Texaco burner coils, while the lower part is exposed to high temperatures from radiant heat and hot gas convection. This significant temperature difference leads to cracking and spalling of the refractory bricks. Frequent start-up and shutdown operations also contribute to the degradation of the refractory lining. During shutdowns, especially when burners are turned off, the cooling effect of the burner coils or the introduction of cold air causes a rapid drop in temperature, followed by a quick rise when the system restarts. Each cycle subjects the corundum bricks to thermal shock, which can lead to cracks and structural failure. Over time, this repeated cycling significantly reduces the lifespan of the refractory material. In addition, moisture condensation during shutdowns can further erode the bricks, accelerating their deterioration. Another issue is the insufficient size of the top expansion joints. Originally designed with a 40mm gap, it was found that this space was too small to accommodate the thermal expansion of the corundum bricks. As a result, the bricks were subjected to excessive pressure, leading to deformation and failure. Theoretical calculations confirmed that the original joint dimensions were inadequate for the operational conditions. To address these issues, several improvements were implemented starting in 1988. The number of corundum brick rings was increased from three to five, and the height of each brick was reduced from 123mm to 70mm, which helped reduce thermal stress. The mortar used was changed to a low-temperature sintered insulation brick, and the joint surface between the corundum and corner bricks was modified to a grooved design to prevent blockage. A 50mm layer of white corundum was poured into the ring gap to seal the castable, reinforced with stainless steel wire for added strength. Above this, additional bricks were installed to provide double-layer insulation and prevent loss of the castable material. The axial expansion of the entire corundum lining was calculated based on its thermal expansion coefficient, and the appropriate expansion joint height was selected to ensure a more reasonable fit, preventing internal pressure buildup that could cause damage. After implementing these measures, the performance of the refractory lining improved significantly. Cracking and casting loss were largely eliminated, and over-temperature alarms at the furnace wall were no longer observed. While the upper parts of the corundum bricks remained relatively thick, the lower sections were more prone to wear due to direct exposure to the burner flame. Despite this, the service life of the refractory lining was extended, and the frequency of major repairs was reduced. In addition to these factors, slag and gangue bricks can also be damaged due to melting and spalling. Impurities in the raw materials can form low-melting compounds that melt at operating temperatures, leading to material loss. Additionally, impurities may penetrate the brick pores and react to form new minerals with different thermal expansion coefficients, causing cracks and eventual flaking during temperature fluctuations. Accidental events such as nozzle damage, water leaks, misalignment, or quench ring failure can also accelerate refractory degradation. Poor quality of refractories, improper installation, or substandard curing processes further contribute to early failure. To improve the situation, the refractory lining was replaced when the lower section of the combustion chamber showed signs of thinning. At this point, the upper parts of the lining were still in good condition, so only the most vulnerable areas were addressed, extending the overall service life of the refractory system. Through these improvements, the problem of refractory damage, overheating, and short service life was largely resolved. This led to fewer shutdowns, reduced maintenance costs, and improved production efficiency. With better material selection, optimized operations, and enhanced masonry quality, the refractory lining now lasts for over two years, ensuring stable and long-term operation of the fertilizer plant.

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