Impact of ammonia content on low-temperature methanol washing and treatment methods
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In the low-temperature methanol washing system, what is the impact of ammonia levels on the hot-zone system, and what are the countermeasures?
High ammonia levels in the system can lead to an increase in the concentration of acidic gases in the system. The temperature of the reflux stream at the top of the regeneration tower should not be too low, as low temperatures can cause blockages, while high temperatures increase solution loss
High ammonia levels increase the risk of ammonium salt crystallization in the acidic gas pipelines of the thermal regeneration tower, leading to pipeline blockages. At the same time, a high ammonia content hinders the regeneration of methanol-poor streams, affecting the absorption of methanol by the process gas and resulting in substandard purified gas. At the same time, sulfurammonium crystals are formed; upon reheating, these crystals decompose, resulting in an excessive level of sulfur in the purified gas.
Add an ammonia scrubbing tower before entering the low-temperature methanol scrubber
A high ammonia content affects methanol’s absorption of sulfur and leads to the formation of ammonium salts that can clog the pipes. To address this issue, it is necessary to wash the tower with water before introducing low-methanol fluid, or to remove part of the methanol in the heat regeneration stream from the system
An excessive ammonia content in methanol can first lead to the clogging of the heat exchanger tubes at the top of the heat zone tower; very high levels may cause hydrogen sulfide to react with ammonia in the heat zone to form ammonium sulfide. As the methanol-rich mixture reaches the top of the scrubber tower, the low-temperature ammonium sulfide decomposes into hydrogen sulfide and ammonia, resulting in elevated hydrogen sulfide levels at the top of the scrubber tower.
Ammonia content may cause carbon-ammonium crystallization; too high a level can result in an excessive sulfur content in the purified gas； It is generally discharged through the regenerator vent
If the previous system is not well controlled, ammonia will inevitably be present; the thermal regeneration tower is equipped with pipelines to prevent carbon-ammonia crystallization, and these pipelines are used for regular discharge