Let’s discuss the issues in low-temperature methanol washing operations
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What causes the ammonia level in the system to exceed the limit during the operation of the Linde low-temperature methanol washing unit? What are the preventive or corrective measures?
1. The amount of washing water in the ammonia scrubber is insufficient, resulting in not all of the ammonia in the process gas being captured. 2. Is the ammonia cooler at the top of the methanol thermal regeneration tower frequently clogged? 3. Regularly open the ammonia release valve to remove excess ammonia from the system
Answer to the original poster’s question: One reason is that the ammonia content in the feed gas exceeds 3 ppm; when absorbed by low-temperature methanol, ammonium sulfide is formed, and its decomposition during regeneration leads to excessive sulfur levels.
First, analyze the ammonia content in the feed gas; ammonia accumulates within the system and cannot be removed – only the excess ammonia can be discharged through the ammonia vent line
The source of ammonia is definitely the pre-system; it is likely that the ammonia washing tower at the converter outlet or at the low methane inlet is not operating properly, and the amount of water used for ammonia washing can be increased accordingly； When the ammonia content in the system accumulates to a high level, the ammonia cooler at the top of the thermal regeneration unit can easily become clogged, which increases the resistance to the discharge of acidic gases. It is possible to periodically open the bypass for heat exchange of the acidic gases, or to raise the outlet temperature of the ammonia cooler to around -25 degrees Celsius for a while in order to remove excess ammonia ；