Malaysia customer order 120 tons refractory bricks and refractory castable.
In the initial operation of a φ3200mm single-nozzle coal water slurry gasifier in a company, local overtemperature phenomenon of the vault often occurs, and the maximum temperature of the cylinder wall reaches 350℃, which has reached the upper limit temperature required by the design of the cylinder wall, bringing great hidden dangers to the stable operation of the gasifier. However, this situation will gradually return to normal after the gasifier runs for a period of time. After several cycles of operation, it is found that the vault overtemperature position of this gasifier is basically the same after each feeding, and the temperature will gradually decrease after running for a period of time and return to normal. The section view of the vault of the gasifier is shown in Figure 1. The vault is composed of spherical head, thermal insulation material, refractory castable and heat-resistant tiles.
Cause analysis
2.1 Direct Cause
During the repair process, it was found that the arch castable is no longer a whole, but has been cracked into 3 parts along the longitudinal. After removal, it can be seen that the surface of the castable has obvious traces of fire, which is dark blue. After the removal was completed, the inspection of the inner wall of the spherical head of the arch found that there were traces of fire in the inner wall of the metal, and the position was consistent with the over-temperature position during operation.
The direct cause of the local overtemperature of the vault is that the castable of the vault produces large longitudinal cracks, and the brick cracks of the hot surface tiles are large. During the operation of the gasifier, the process gas is channeled through the brick cracks and castable cracks to the inner wall of the dome, resulting in the local overtemperature of the vault. However, after a period of operation, coal powder and cinder will slowly fill the cracks and cracks of the hot surface brick, and the high-temperature process gas can not produce reflux in the cracks to form a dead zone, and the phenomenon of overtemperature of the vault will gradually disappear and return to normal temperature.
2.2 Other Reasons
1) There are problems in the quality of the original arch refractories and the quality control of the masonry process. In order to make the castable have good fluidity during the construction process, a lot of water is often added, resulting in slow solidification speed and low strength, and it is easy to cause cracking of the arch castable in the original oven.
2) Improper control of the oven speed in the original oven of the gasia furnace, and too fast pressure boost rate after guiding will cause the high-temperature process gas to quickly reach the inner wall of the spherical head through the crack of the refractory material, forming a local reflux, and then causing local overtemperature of the vault.
3) During the operation of the gasifier, the central oxygen control is too low, resulting in the flame area near the vault area, the brick wall is not easy to hang ash and slag, and the high-temperature gas is easier to pass through the crack of the refractory material to the inner wall of the spherical head, aggravating the local overtemperature of the vault.
03
Corrective measures
3.1 Control the quality of refractory products
In the process of refractory processing, there are raw material quality problems, long storage time and failure of materials, which will affect the furnace wall temperature of gasifier after the materials are put into use. For example, the storage time of chromium corundum castable is too long, the solidification time is slow, the strength is low, and the high iron content of high chromium brick is easy to heat transfer and make the cylinder wall overtemperature. Strengthening the quality control of refractory raw materials is the first line of defense to ensure the stable operation of coal water slurry gasifier and prevent overtemperature of the vault. Before the local overtemperature of the gasifier vault, there were basically no quality control measures for the gasifier refractories. In view of the problems, the corresponding control of key indicators such as the production date and chemical composition of the materials was strengthened. Each batch of primary materials was inspected before the use of the refractories, and the solidification and strength test of chrome-corundum castable was carried out in accordance with the proportion. The material chemical composition of high chromium brick was analyzed.
3.2 Strengthen the quality control of refractory masonry process
To strengthen construction quality control, the first is to select a construction unit with corresponding qualifications, and the construction unit can prepare a reasonable construction plan, and after approval, construction can be carried out. During construction, the upper and lower flanges of gasifier should be used as the basis to pull the bidirectional center line to ensure the masonry size of refractory materials. The amount of water added to castable in the construction process and the construction temperature when pouring chromium-corundum castable are screwed to prevent problems such as solidification caused by too fast construction. After completion of construction, carefully check and accept the size of brick joints and various parts to ensure the quality of masonry.