Ammonia solution level indication deviation
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The measurement and control of the liquid level in the medium-pressure ammonia absorption tower for urea production are carried out using differential pressure level transmitters. Steam heating is applied to the negative pressure conduit to prevent it from becoming empty. In the initial stage of operation, these transmitters were extremely unstable; after each calibration they could only function for 1–2 hours, after which significant deviations in indication occurred, rendering them ineffective for control purposes.
The problem lies with the negative pipe; although steam is used for heating to ensure the evaporation of ammonia inside it, water gradually accumulates within this pipe. With the liquid level remaining constant, the accumulation of water in the negative pipe causes the measurement values to decrease steadily until they reach 0. It is possible to consider adding an isolation tank to the negative pipe and filling it with an isolation fluid.
If that doesn’t work, try using a different pair of magic boxes; it’s difficult to control the level of condensate in the pressure guide tube when using heat tracing
The level of the isolation fluid also changes over time, which makes it very difficult to handle
Condensate has formed in the negative pressure section. It is recommended to use double flanges
Use double flanges for level migration; calculate the lower range
For liquid ammonia, should a magnetic flap level gauge be used?