How to deal with blockages in acidic gas pipelines of low-temperature methanol washing caused by carbon ammonium crystals

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This post was last edited by liaifeng on 2018-9-1 at 12:19. The acidic gas line at the top of the methanol regeneration tower in the low-temperature methanol washing process often gets blocked; once blocked, the sulfur recovery system is shut down and the line is cleared. It’s very troublesome. Performance and reasons: 1. The ammonia level at the inlet of the ammonia washing tower was 15 PPM, while it was 5 PPM at the outlet. 2. The ammonia concentration in the lean methanol stream kept rising, reaching up to 140 PPM; the ammonia content in the fourth reflux tank reached 1.6%. After crystallization caused blockages, the pressure in that tower increased, while the pressure of the acidic gas dropped to 0.15 MPa. 3. A carbon ammonium crystal pipeline was installed, but when this pipeline was activated, large amounts of methanol entered the sulfur recovery unit, making it difficult to control the air supply there and also increasing the risk of catalyst coking due to blockages. Solution: Redirect the acidic gas to the flare, shut down the deep cooler, and raise the temperature to 65–70°C to eliminate crystallization. However, sulfur recovery is considered an environmental protection facility, and shutdowns or restarts require approval and registration with the environmental protection authorities. Question: 1. Is the ammonia washing tower not meeting the requirements, resulting in high ammonia levels at the outlet? 2. Is there any way to reduce or prevent blockages in acidic pipelines? 3. How to determine the air supply amount and avoid coking when acidic gases are not sent to the flare but directly fed into the sulfur recovery unit? 4. What should be done in case of high levels of methanol and ammonia?