Gasification Daily Question: 2016-11-16 Process Analysis Question (5 points for participation, 10 points for a correct answer)

(1) During feeding, the coal slurry is not introduced into the furnace first; instead, oxygen enters the furnace first, or insufficient low-pressure nitrogen is used for displacement, resulting in the formation of explosive mixtures of oxygen and combustible gases inside the furnace； (2) When stopping, low-pressure nitrogen displacement is inadequate, there are flammable gases in the system, or the oxygen valve is leaking, allowing oxygen to enter the furnace ； (3) There is an error in the actuation time of the safety system valves.

1. Inaccurate assessment of process conditions 2. Unstable quality of the prepared water-coal slurry 3. Inaccurate readings from the electromagnetic flowmeter 4. Abnormal operation of the high-pressure coal slurry pump

1. Leakage in the drain valve at the outlet of the coal slurry pump, as well as in the flushing and circulation valves, led to an oxygen-rich explosion; 2. During material feeding, water entered the gasification furnace, resulting in an explosion caused by water; 3. Problems with the safety system caused the valves to malfunction, so the coal slurry did not enter the furnace while oxygen did, leading to an oxygen-rich explosion； 4. Operational errors increase oxygen flow rate ； 5. Before feeding the material, the gasification furnace and washing tower were not thoroughly purged, resulting in the formation of a mixture of oxygen and combustible gases inside the furnace after feeding** ； 6. Failure of the slurry pump results in low slurry flow, leading to overheating and explosion due to excess oxygen ； 7. Incomplete replacement during parking led to leakage from the oxygen valve; oxygen entered the gasification furnace, causing a peroxide explosion

The issue of some cylinders in the slurry pump not pumping or pumping at a low volume was not detected and corrected in a timely manner； Slurry pipeline leakage (at flanges) and improper opening of valves on the pipeline or severe internal leakage ； The flushing water for the slurry pipeline or slurry tank being turned on (or leaking internally) causes the slurry to become too dilute, among other issues. Secondly, the measurement errors of the coal slurry flow meter and the oxygen flow meter are relatively large, resulting in actual excess oxygen ； Another issue is that the oxygen control valve is not sensitive enough (with severe lag) or there are faults with the valve accessories. Strengthening maintenance, adhering to strict procedures and verifications, and paying attention to monitoring furnace temperature (methane) and carbon dioxide levels can help prevent and avoid such issues.

1. Water enters the slurry tank. 2. There is a leak in the slurry pipeline. 3. The pressure in the gasifier drops rapidly. 4. One cylinder of the slurry pump does not operate properly. 5. The slurry flow rate is determined by the speed of the slurry pump. 6. Fluid used to drive the slurry pump leaks. 7. The diaphragm of the slurry pump ruptures suddenly

①Leakage in the sewage valve at the coal slurry pump outlet, as well as in the flushing and discharge valves and circulation valves; oxygen excess was detected； ②During feeding, water is introduced into the gasification furnace, resulting in water ingress ； ③There was a problem with the safety system; the valves malfunctioned, and oxygen entered the gasifier before the coal slurry did, resulting in an oxygen excess ； ④The operator made mistakes while adjusting the speed of the slurry pump, the oxygen flow rate, and the control valves, which led to an excess amount of oxygen ； ⑤Before feeding the material, the gasification furnace and scrubber were not thoroughly purged ； ⑥There is a problem with the slurry pump, resulting in low slurry flow rate ； ⑦After parking, the system does not purge thoroughly, resulting in a leak in the oxygen valve

Peroxide can be analyzed from two aspects: First, there is an actual excess of oxygen: 1. Incomplete displacement by nitrogen; 2. False readings of the oxygen flow rate, resulting in an excessive amount of oxygen being added; 3. A sudden drop in pressure in the gasification furnace, leading to an excessive amount of oxygen being added at that moment. Second, an excess of oxygen can occur due to a lack of other substances: 1. Leaks in the coal slurry pipeline; 2. Problems with the coal slurry pump, resulting in less or no flow of coal slurry; 3. A sudden decrease in the concentration of the coal slurry

1. The flow meter is inaccurate. 2. The coal slurry pump does not operate properly. 3. The operators fail to make timely adjustments and lack a sense of responsibility. 4. The quality of the coal slurry is poor. 5. The control valves do not function properly. 6. There are fluctuations in oxygen pressure

1. Improper process execution, 2. Unstable quality of water-coal slurry, 3. Inaccurate readings from the electromagnetic flowmeter, 4. Abnormal operation of the high-pressure coal slurry pump, 5. Inaccurate setting of process parameters, 6. Excessively high oxygen content.

1. Human error, 2. Equipment issue