Causes of burnout in the Texaco gasification downcomer and troubleshooting?

It is mainly caused by blockages due to decline, as well as prolonged overheating.

The key issue is caused by blockage in the quench ring; I think it’s due to incomplete cleaning during maintenance – there are no other reasons

The quenching ring was clogged, and the water distribution in the downcomer was uneven; as a result, no water film of sufficient thickness could be formed on the inner side of the downcomer to protect it, leading to its damage. It is mainly because the furnace temperature is extremely high, causing blockage of the quenching ring. The high furnace temperature is mainly due to the following reasons: 1. An increase in the oxygen-coal ratio, that is, a unilateral increase in the oxygen supply. 2. Unstable coal quality leads to a decrease in the ash melting point ； Either the amount of flux added is insufficient or too low, resulting in a lower melting point of the ash. 3. Problems occurred in the various quench water supply channels, resulting in insufficient quench water volume. This post was last edited by GSP on 2007-12-6 16:25 ]

There are generally two reasons for the burn-through of the downcomer: one is a problem with the quench water system, where insufficient water volume prevents the formation of a protective water film, or partial blockages in the quench ring lead to an uneven water film； Secondly, changes in the type of coal lead to changes in its viscosity-temperature properties, which in turn causes slag accumulation on the downcomer.

I’m not very knowledgeable, but is an excessively high furnace temperature related to clogged quenching rings?

Same question: how does a decrease in ash melting point lead to the burnout of the downcomer? Also, what proportion does the water flow along the wall of the downcomer account for, compared to the water volume ejected from the quenching ring? Why?

The reasons for the burn-through of the downcomer include: 1. The flow rate of the quench water is below the specified values, or the quench water is not distributed evenly across the quenching ring, resulting in partial loss of water supply to the downcomer; 2. Quality issues with certain welding points; 3. An inappropriate selection of material for the downcomer; 4. Instability during production, with too low a liquid level control in the vaporizer, which leads to instability in the downcomer. Damage to the downcomer causes an increase in the syngas outlet temperature; the unit should be stopped immediately to repair the downcomer, and if the damage is severe, it should be replaced.

Is there any expert who has clear diagrams regarding the quench ring and downcomer sections?

Go inside the furnace and you’ll know everything...

The quenching ring was clogged, and the water distribution in the downcomer was uneven; as a result, no water film of sufficient thickness could be formed on the inner side of the downcomer to protect it, leading to its damage. I agree with this view; both the downcomer and the quench ring in our unit have been damaged by burning. Is the furnace temperature too high, causing blockage in the quench ring? ? ? ? ? ? ? ? ? I have a question: is there any relationship between these two?

The burnout of the downcomer occurs because slag accumulation in the downcomer leads to uneven water distribution and bulging; in severe cases, this can result in burnout. When the downcomer is severely clogged with slag, the process gas can also cause the downcomer to burn out. Slag accumulation in the downcomer is caused by improper temperature control of the gasifier.

Accident Report on Blockage of Slag in the Quench Chamber of the Gasification Furnace, Leading to Damage of the Downcomer. Course of events: At 22:48, the temperature reading in the lockhopper of the gasification furnace was abnormal; slag accumulated in the slag breaking frame, and at the same time, the readings for CO2 dropping and CO rising indicated severe slag blockage. The operator increased the temperature and tried various methods such as repeated backflushing and pressure relief, but there was still no improvement by 23:30. The duty personnel were notified, and the load was significantly reduced to 18 m3/hr; at this point, the pressure difference in the gasifier also increased markedly, indicating that the slag had reached the vicinity of the downcomer. After load reduction, processing continued under the guidance of the branch plant and workshop until 4:30 the next day, but without success, forcing a shutdown. Reason: 1. The burner of the gasification furnace has been experiencing severe uneven combustion recently; this issue persisted from 13:00 to 17:00, for nearly four hours. The local temperature in the furnace reached up to 1700°C. In order to reduce this temperature, the amount of oxygen and coal used was low, which may have resulted in large pieces of slag remaining inside the furnace. Once the furnace temperature is adequate, it may proceed to the quench chamber. And because it is too large, it cannot be crushed by the slag crusher. When multiple slag pieces accumulate on the slag breaker, bridging occurs. 2. The operator used the correct method when handling the bridging. However, it was not until 1 hour later that the amount was significantly reduced and the on-duty staff were contacted, which can be considered untimely; due to this delayed reduction, the best opportunity to deal with the slag may have been missed. 3. The processing time is too long, causing slag to accumulate in the downcomer and damaging it. Consequences: 1. The slag breaking machine developed a bridge, slag clogged up the quenching chamber, forcing a shutdown. 2. Slag clogs the downcomer, causing it to burn out. 3. Yield losses increase. Lessons and measures: 1. When the burner is experiencing misfiring for an extended period, the furnace should be shut down and the burner replaced. 2. When locking the tundish slag, contact the workshop promptly. If it cannot be processed within half an hour, the dosage should be quickly reduced to 15 m3/hr to continue the treatment. 3. If it cannot be resolved within 2 hours, shutting down the plant for handling should be considered. 4. Strengthen on-site observation of slag shape and amount.

Could you be more detailed: lol :lol

Personal opinion: The burnout of the downcomer is usually caused by slag accumulation on its walls, which leads to high local temperatures and subsequent burnout. There may also be a lack of a uniform protective water film, or the downcomer could be severely blocked. Solution: There’s nothing that can be done in such cases; it’s necessary to shut down the plant.

I have seen three burned-down downcomers within a year; through observation and analysis inside the furnace, as well as by making comprehensive comparisons using the parameters from operation, it was determined that the root cause is the formation of a dry zone. Firstly, the low amount of water in the quenching ring is the main contributing factor； Secondly, the excessive heat load of the gasifier destroys the water film in the downcomer, resulting in slag formation ； Thirdly, the burner sprays unevenly and the flame zone moves downward significantly, directly tearing apart the water film in the downcomer and resulting in slag accumulation ； Fourth, the properties of the ash are unstable.