Does your chill water pump experience cavitation during the large-scale circulation before feeding?
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Our chill water pumps often experience cavitation during the large-scale circulation before material feeding. I’d like to discuss this with everyone to see if you’re also facing such an issue Once, during a maintenance task, the impellers of the water pumps all cracked. But it’s not necessarily cracked during the high-cycle period; it can be confirmed that this pump experienced mild cavitation during that time.
We did not experience cavitation. After establishing a large circulation during operation, it’s not advisable to raise the temperature of the deaerator too quickly; instead, increase the water temperature gradually before adding materials. This approach can help reduce cavitation. In my opinion, in the process of gasification, it is important to distribute heat sources properly. As long as the heat balance is maintained, there should be no problems with the entire gasification, washing, and flashing process. Some operators fail to manage the heat balance properly, blaming either the equipment or the design. From the answers the original poster has given to various questions, it seems they have considerable experience, so I think this shouldn’t be a challenge for them.
There is no pressure in the system; why raise the water temperature so high? Pay attention to controlling the water temperature, and if necessary, replace it. It usually happens when parking; it rarely occurs before driving!
Cavitation is a normal phenomenon and is easy to resolve; it has nothing to do with the equipment or design, nor with thermal balance. When a gasification furnace is operating normally, it’s not possible to cool down the deaerator. Therefore, when the water temperature exceeds 93 degrees, the steady state of the scrubber tower is disrupted, and the cooling water pump is prone to cavitation. Design measures exist to address this issue: by reducing the pressure of the high-pressure gray water at the inlet of the cooling water pump and controlling the liquid level in the scrubber tower, the problem can be easily resolved.
He said that cavitation mostly occurs when the deaerator is in a hot state, with high temperatures of the high-pressure ash water. The system already has a furnace running.
Based on operational experience, it is common to establish a large circulation before feeding material; pump cavitation rarely occurs after venting. A large cycle is established while a furnace is in operation; due to the low amount of flash steam, the temperature rarely reaches 100. Of course, it is possible for some manufacturers to use low-pressure steam instead to keep the temperature around 100. In either case, since the deaerator operates at a slight positive pressure, the temperature is basically around 100 degrees. Before starting the cooling water pump, the liquid level in the carbon scrubber is usually above 60%, and due to the static head generated by the pressure difference within the carbon scrubber itself, cavitation in the pump rarely occurs. If cavitation occurs due to an overly rapid pressure release during the shutdown phase of the gasifier, it can only be prevented by using the cavitation prevention valve at the inlet of the cooling water pump.
The deaerator system is shared among several series, and it is essential to maintain an appropriate temperature in the deaerator. We often encounter this issue when parking; the system pressure drops, which can easily lead to cavitation. However, there are emergency procedures in place to handle such situations promptly. We cool the deaerator graywater two hours before starting up the preheating burner and shutting it down