Reasons for soda ash turning gray after H2S levels exceed the limit
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When the H2S level in CO2 reaches 150 mg/m3, the color of soda ash turns gray. Could anyone tell me what the reason for this is?
High H2S content leads to the formation of large amounts of black FeS and gray Fe(SH)2, resulting in blackening
An excessive amount of sodium sulfide leads to lime alkalinity. A low amount of sodium sulfide leads to red alkali. Adjust the amount of sodium sulfide added.
Hydrogen sulfide enters the alkali production process, and during carbonization it forms insoluble iron-sulfur compounds (mainly ferrous sulfide), causing the heavy alkali to turn black. 150 is also too high; it’s better to keep it below 50.
When iron sulfides enter the alkali production section, two additional issues need to be checked； 1. Iron ions. It is often due to severe corrosion of the equipment and pipelines. 2. Clarification tank. The sediment was not removed in a timely manner. In general, iron ions are a prerequisite for the formation of colored bases, while hydrogen sulfide determines the color intensity of these colored bases.