Interlock for low quench water level in gasifier
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Ladies and gentlemen: The interlock for low level of the quench water in our company’s gasification furnace is implemented using three double-flange differential pressure transmitters; after ESD processing, a three-out-of-two interlock system is used. The set value for this interlock is 14.5%, below which the sequence control for the hopper is stopped, the slurry cut-off valve is closed, and the emergency quench water valve is opened, etc. Due to the consistently low level of the quench water (which cannot be increased; the specific reason has not been identified despite extensive research and numerous discussions on the process), this interlock function cannot be activated. Question: What type and manufacturer are the level transmitters used by various units, and are they reliable? What is the liquid level interlock value? Do other units face similar problems and what are the solutions?
The purpose of the interlock designed for a low level of quench water is to protect the downcomer from being damaged and to prevent process gas from escaping through the black water pipeline. The setting of this interlock value is related to the equipment design and the operational conditions of the process. I wonder what type of level transmitters are used in various units, and whether they are reliable? Is this interlock activated?
What kind of container is this coolant water in? Is it similar to a boiler drum? Is no on-site level gauge installed? If the parameters of the 3 level gauges are set correctly and they are installed in the appropriate locations, they should be able to accurately reflect the level of liquid. Shouldn’t the process team try adding water to them continuously to see if the level changes?
It is supposed to prevent the liquid level from dropping below the downcomer, while also serving as an air seal? Why is the liquid level always low? How low is it? Has it always been below the 14.5% interlock value? Differential pressure transmitters are generally used for measuring water levels. Should we look for the reason from a technical perspective?
This post was last edited by chensf123 on 2016-4-6 at 14:46. The liquid level is generally between 15% and 20%; the level transmitter is of the double-flange type, and when the cooling water flow is increased, the process gas carries away the water vapor. The high flow rate of the quench water indicates that the flow path is unobstructed; the flow rate of the black water is also low, and the lock hoppers and slag locking valves do not draw any flow away, otherwise it would be impossible to maintain pressure balance during slag discharge. Therefore, the quenching water can only be carried away by the process gas. The process gas temperature is also normal, and the load isn’t too high either. It might be related to the equipment; with a liquid level interlock set at 15%, even minor fluctuations can easily trigger an automatic shutdown. Moreover, the liquid level in the vaporizer is a key aspect for process operation and monitoring. To improve the system’s availability, I believe there is no need to implement such an interlock.
Double-flange level gauges are generally used for measuring liquid levels; the level can’t possibly be too high anyway, and there’s no interlock system in place