Regarding the adjustment of the quench water flow in the gasifier?
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This post was last edited by Comrade Lao Li on 2009-8-15 at 15:33. When the furnace is operating at full capacity, the amount of water used for cooling is 380 cubic meters per hour! Yet when the furnace is operating at only 70% of its capacity, the cooling water volume already reaches 400 cubic meters per hour, and yet the liquid level in the furnace just won’t rise – it’s really frustrating! Since our factory is new and the workers have no experience in operating the equipment, we can only proceed by trial and error; therefore, we hope everyone can help out by offering some suggestions! Is it true that the more quench water used, the better? Is it related to the load? ?
Quench water is used to regulate the temperature of the syngas and the trays as well as to perform a preliminary washing of the syngas, and it is generally adjusted based on the outlet temperature. It varies with the magnitude of the load. The liquid level is regulated by a valve. They are two different concepts. Check it again. Check if there is a problem with the level control valve.
It is originally a dynamic level balance process; how is it possible for the liquid level not to rise? Check the adjustment status of the black water discharge control valve and the chilled water inlet control valve.
It’s probably not a valve issue; it is recommended to conduct a calculation of the water flow volume, as water contamination in the syngas is suspected.
Please check now whether your flow meter and liquid level are accurate, and examine the opening degrees of the emergency cooling water automatic control valve and the on-site valve. If the valve openings are the same and all are fully open, if pressure cannot be increased, it may be due to a high amount of black water being discharged from the gasification furnace. You can appropriately reduce the discharge of black water from the gasification furnace! Another point is whether the lockout valve ensures complete closure while in operation. The amount of quench water is used to maintain the liquid level in the quench chamber and the temperature at the syngas outlet; the minimum amount is required to ensure that the temperature of the syngas leaving the gasifier does not exceed the specified process parameters. The notion that more is always better is one-sided; with a larger volume of water and a constant pipe diameter, the flow velocity of the liquid increases, which in turn reduces sedimentation and scaling in the pipes. As a result, it becomes difficult to raise the temperature of the syngas at the outlet – this is what is referred to as the water vapor ratio. If limestone needs to be added to your coal slurry or coal powder, and the hardness of the quench water is high, it’s better to add more water to prevent scaling in the pipes, which could affect the amount of quench water available!
Many manufacturers experience this: as the load increases, the gas-phase load rises as well, the water volume carried increases, and it becomes impossible to raise the liquid level in the quench chamber. 1. As mentioned above, check whether all the parameters are normal, such as the temperature of the exhaust gas and the drainage volume, etc., and gradually adjust these parameters. 2. Check whether the cooling water flow meter is showing inaccurate readings. 3. Add fresh water to the system to replace the contents of the gasifier scrubber tower system; increase the drainage from the gasifier and scrubber tower as appropriate, so that the liquid level can rise.
As suggested by the colleagues above, first check the quench water control valve and flow meter to see if there is an excessive error. If there are no problems, then perform some water balance calculations to determine whether it is due to an excessive flow of black water or water carried in the process gas. The former is straightforward – just reduce the flow control valve for the black water. As for the latter, it needs to be considered on a case-by-case basis. Generally speaking, with 70% load, adding such an amount of quench water will not result in water being carried in the process gas; however, if the operating temperature is high (i.e., the oxygen-to-coal ratio is high), this issue can occur. At this point, first try to lower the furnace temperature if possible and increase the discharge of black water; this should resolve the issue.