What problems have arisen with the alkali washing facilities after the addition of the sulfur recovery unit?
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During 2017–2018, in order to address the issue of ensuring that the exhaust gases from the incinerators in sulfur recovery units met regulatory standards, a considerable number of such units were equipped with additional post-treatment alkaline washing facilities. What problems arose as a result of the installation of these additional alkaline washing facilities? How to solve it?
What kind of alkali is used? Generally, it is for the treatment of waste salts as well as to prevent equipment corrosion and blockages
We have also added a post-alkaline washing system. About one and a half years have passed since work began, and there was an issue of high pressure difference in the alkali scrubber, caused by the dirty quality of the water used for flushing; the problem was resolved by switching to deoxygenated water for flushing. No other problems have been found; they may not have come to light yet. Feel free to communicate.
Alkali washing is used to absorb sulfur dioxide and hydrogen sulfide; care must be taken to address issues of corrosion and blockages, as sulfur tends to crystallize at low temperatures and can clog relevant pipelines along with other impurities. Additionally, corrosion is also common due to hydrogen sulfide and sulfur dioxide. Another thing to note is the issue of spontaneous combustion.
For sulfur plants, there is no hydrogen sulfide issue in the post-alkaline washing; otherwise, there is a problem with the operation of the incinerator. It is recommended that the equipment pipelines in the alkali washing system be made of stainless steel.
1. The issue of alkaline wash water discharge. Initially, the design called for wastewater stripping, but this approach proved ineffective; the sulfide levels in the purified water were over several hundred. It was later found that the sulfides generated as a result of the reaction between the alkali wash water and sulfur exhaust gases could not be removed by stripping at all! 2. The problem of blockages in the trays and pipelines is likely due to high concentrations of salts formed as a result of the reaction, which facilitate crystallization; therefore, we add large amounts of demineralized water while simultaneously draining the liquid
Could you share the parameters for alkali washing? Thank you.
For the heat exchangers in several previous renovation projects related to the alkaline scrubbing process for sulfur recovery units, 316L material was required. Now, another environmental protection company is asking for 304 material – is that acceptable? It is speculated that the 304 unit is currently handling saturated wet flue gas that has been treated with alkali; the levels of sulfides and hydrogen sulfide are low, but there is still concern. Has this been done on a large scale before?
At present, this facility is not yet in operation, but from a process perspective, attention should be paid to dew point corrosion in the pipeline that leads from the exhaust furnace to the tower. Also, the nozzle needs to be chosen carefully. For operation, it is best to use 20% liquid caustic soda.
1. Alkali is consumed, salt precipitation increases, and it cannot be processed