100 Questions on Gasification

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1. What are the causes of tempering and flameout accidents during baking, and what are the solutions? Answer: Reason: A. The liquid level in the vaporizer is too high, blocking the downcomer opening ； B. Sudden decrease in steam extraction volume ； C. A sudden leak occurs during the furnace heating process (such as an access panel or valve being opened). Solution: A. Lower the liquid level to the normal level for drying, and continue with the drying process only after the liquid has been replaced with a suitable substance ； B. Check steam flow rate ； C. There was no mutual notification for cross-task operations. 2. What are the reasons for abnormal coal slurry flow rate when feeding material by vehicle, such as no flow or extremely low flow leading to shutdown, and what are the solutions? Answer: Reason: A. Solid coal slurry has accumulated in the coal slurry pipeline, causing blockage ； B. The pipeline backwash valve was not properly verified. Treatment method: A. Flush the clogged coal slurry pipeline to ensure it is unobstructed, then resume operation (the temperature of the gasifier must be ≥880°C, and the system must have passed the purging test) ； B. Confirm that the backflow valve is fully closed, then proceed with starting up the equipment (the temperature of the vaporizer must be ≥880°C, and the system must have passed the purging test). 3. What are the reasons for abnormal oxygen flow rate and shutdown due to low low levels when feeding material by vehicle, and what are the solutions? Answer: Reason: A. The oxygen cut-off valve is not open ； B. The timing setting value between the oxygen cut-off valve and the vent valve is not properly matched. Solution: A. Please have the instrumentation staff check the valve and temporarily stop operating the equipment ； B. When stopping feeding, re-adjust the set value. 4. During startup and shutdown, popping or explosions occur due to peroxides in the vaporizer. What are the possible causes and solutions for issues occurring at the combustion chamber, quenching chamber, carbon scrubbing tower, burners, and the pipe flange connections of coal slurry? Answer: Reason: During feeding, the coal slurry was not introduced into the furnace first; instead, oxygen was introduced first, or insufficient high-pressure nitrogen was used for purging. This led to a mixture of flammable gases that reached the explosive limit. When the system was shut down, low-pressure nitrogen failed to remove all flammable gases from the system, and an oxygen valve leaked. Handling method: If it occurs during driving, stop driving immediately and purge with high-pressure nitrogen ； Identify the cause of the explosion and assess the extent of damage, taking necessary measures ； If this occurs during the parking phase, check whether the oxygen valve is closed, and manually activate the high-pressure nitrogen vaporizer to purge it. 5. What are the causes of fires in oxygen pipelines and valves, and what are the methods for dealing with them? Answer: Reason: A. The oxygen pipeline was not cleaned thoroughly, containing slag, grease, stones, sand, etc ； B. Excessive oxygen level when setting the oxygen flow rate while driving. Handling method: Quickly close the oxygen supply valve to cut off the oxygen source and carry out fire extinguishing. Notify the air separation system to switch to the nitrogen displacement system. 6. What are the reasons for low or unstable flow readings on the coal slurry flow meter, and what are the solutions? Answer: Reason: A. The slurry pump’s single cylinder does not discharge fluid ； B. Air leakage in the pump suction line ； C. There is a leak in the coal slurry pipeline. Handling method: A. Inspect the operation of the slurry pump on-site ； B. Tightening the bolts of the leaking flange ； C. Locate and eliminate leaks in the coal slurry pipeline. 7. What are the phenomena, causes, and solutions for overheating of the gasifier furnace wall? Answer: Phenomenon: A. Process parameters above 180–225°C; an alarm is triggered at temperatures above 250°C, and the actual temperature measured on site is also above 250°C ； B. Local over-temperature alarm or excessive local temperature rise. Reason: A. Air leakage through the brick joints causes airflow short-circuiting ； B. The operating temperature of the gasifier is too high ； C. The surface thermocouple gives inaccurate readings ； D. Removal of section or local refractory bricks. Treatment method: A. Appropriately reduce the load and adjust the central oxygen ratio accordingly ； B. Adjust the slag port pressure difference to normal levels and appropriately reduce the operating furnace temperature; however, slag port blockage must be strictly avoided ； C. Check the accuracy of the surface thermocouple ； D. Stop the system, remove the burner to inspect the refractory bricks, and repair any damaged areas. E. Strictly adhere to the operating regulations regarding overheating of the furnace walls. 8. What are the phenomena, causes, and solutions related to water entering the system behind the quenching chamber of the gasification furnace? Answer: Phenomenon: A. The flow rate of the quenching water decreases (due to an increased venturi pressure difference, which results in a higher pressure in the quenching chamber) ； B. Drop in the quench chamber liquid level ； C. Venturi pressure difference fluctuations ； D. Rise in the liquid level of the carbon scrubber tower (when the control valve is set to automatic mode, the opening of the make-up water control valve LV1308A decreases) ； E. The temperature at the syngas outlet of the carbon scrubber increases, and the syngas flow rate fluctuates. Reason: A. The operating temperature of the black water in the quench chamber is too high ； B. The system load is too high, resulting in an excessive amount of syngas ； C. The pressure in the rear system fluctuates and is low ； D. Damage or detachment of internal components in the quench chamber. Solution: A. Increase the amount of water used for quenching, and correspondingly increase the drainage volume ； B. The system load can be appropriately reduced ； C. When conditions permit, appropriately increase the system pressure; once stable, maintain that system pressure ； D. If the internal components of the quench chamber are damaged, the furnace must be shut down for repair; E. While ensuring that the pressure difference at the slag outlet of the gasification furnace is within normal limits, the operating temperature of the gasification furnace should be reduced appropriately. 9. The pressure difference indicator at the slag outlet of the gasification furnace shows a high reading; what are the reasons for the reduced amount of slag identified during on-site inspections, and what are the solutions? Answer: Reason: A. The operating temperature is below the melting point of the coal ash, resulting in severe slag adhesion to the walls, which causes the slag to solidify at the slag discharge port ； B. The analysis of coal variety changes is not timely; the liquid viscosity of coal ash is high, and the fluidity of slag is poor. Solution: A. Adjust the oxygen-coal ratio to increase the furnace temperature ； B. Immediately analyze the composition of the coal type and promptly notify the relevant personnel. 10. What are the reasons for the increased amount of slag at the outlet of the slag skimmer identified during on-site inspections, and what are the solutions? Answer: Reason: A. The operating temperature is below the melting point of coal ash; sampling analysis revealed an increase in combustible substances ； B. Analysis of coal variety changes is not timely ； C. The nozzle does not atomize properly, and the wear-resistant parts of the spray head cause severe misdirection of the spray. Solution: A. Adjust the oxygen-coal ratio to increase the furnace temperature ； B. Immediately analyze the composition of the coal type and promptly notify the relevant personnel ； C. Parking handling. 11. The slag sample contains a large amount of carbon black slurry; the proportion of ash in the glassy material decreases. Analytical data show a significant increase in the content of combustible materials. What are the reasons for the deterioration of the gas composition and what are the methods for dealing with it? Answer: Reason: A. Prolonged abrasion of the burner, misdirected spraying, and poor atomization effect ； B. Changes in the oxygen gap or slurry gap of the burner affect the atomization effect ； C. Improper adjustment of oxygen-to-coal ratio ； D. The furnace temperature is too low. Solution: Adjust the oxygen-coal ratio and increase the operating temperature appropriately ； If the burner’s operating cycle is too long, apply to shut down the system and replace the burner. 12. What are the reasons for the sharp increase in syngas indication, the instability of syngas temperature, and the increase in water vapor ratio, as well as the solutions? Answer: Reason: A. High liquid level in the carbon scrubber tower ； B. The carbon scrubber tower trays are damaged ； C. On the tray, the washing liquid in the wash tower is not distributed evenly or there is liquid retention ； D. The demister is clogged or damaged. Solution: A. Lower the liquid level ； B. Parking handling ； C. Adjust the wash solution flow rate. 13. What are the reasons for the decrease in differential pressure in the carbon scrubbing tower, the flipping of the tray plates, high temperature of the syngas, and excessive dust content, and what are the solutions? Answer: Reason: A. The tray is not firmly fixed ； B. The feed load is too high, causing severe stress on the tray plates ； C. The pressure relief rate during parking is too fast. Solution: A. Be careful during installation, and conduct a thorough inspection after it is installed ； B. The feeding load should not be too high; it should be kept at 50-60% of the normal load ； C. Strictly control the pressure release rate