The problem of sulfur ammonium salt crystal blockage in wastewater stripping units without side streams
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For sewage stripping units that do not have side lines, ammonia and hydrogen sulfide tend to crystallize at low temperatures to form ammonium sulfide, which can clog pipelines and heat exchange equipment. Let’s discuss where crystallization usually occurs, and how to prevent the formation of ammonium sulfide crystals during startup and normal operation. During the start-up process, after establishing the cold cycle, how can blockages in the acidic gas pipelines at the top of the tower and in the air-cooled crystallizers be prevented during the heating phase? What are the methods for dealing with such crystallization-related blockages?
If ammonium salt crystals form and block the system, it can be flushed with demineralized water.
Those who use the single-tower process, please share your experience.
At the top of the tower, the pressure tapping pipes on the reflux tank are prone to crystallization; steam backwashing should be applied； The acid gas lines at the top of the tower and the air-cooled crystallizer are flushed with demineralized water.
If part of the air-cooled tube bundle is blocked by crystallization, and after desalinated water is injected it flows through the unobstructed pipelines, how can the crystallized tube bundle be flushed clear?
It can be soaked in demineralized water for a while; the crystals dissolve more easily in water, especially in hot water.
A heat tracing line must be installed on the amine gas line; for areas prone to blockage, a steam back-purge line or a jacket should be added. Desalinated water or deoxygenated water is added to the inlet of the air cooler to prevent blockages.
I’ll tell you a good and simple way to raise the tower top temperature to 110 degrees
Why a cold cycle? Wouldn’t it be possible to first raise the temperature of the tower before treating the wastewater? The temperature after air cooling shouldn’t drop below 90 degrees, which can help reduce salt formation; moreover, heating elements can be used. I’m a novice – please give me some guidance
At present, our system is capable of maintaining a temperature after cooling above 95 degrees; there is heat tracing along the entire pipeline, and the temperature of the sulfur reaches over 80 degrees as well – no crystallization has occurred yet
For the issues related to the tower top and air-cooled crystallization, it is possible to use purified water from the bottom of the tower for flushing; this purified water, pumped out by the pump located at the bottom of the tower, has a good temperature profile
All pipeline instruments downstream of the tower top require heat tracing