Unknown irritating solid in flash vapor condensate
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A mixed aqueous solution of sulfuric acid, soft water, and m-phenylenediamine is subjected to high temperature and pressure followed by flash evaporation for cooling. The vapor resulting from flash evaporation has an irritating odor; solids crystallize out of the condensed vapor – these solids are light yellow in color, combustible, and possess a strong irritating smell of sulfur dioxide. I would appreciate it if experts could help determine what these solids might be and explain the principle behind their formation
Based on the description, the solid that may form is the m-phenylenediamine sulfate salt. The principle is that under high temperature and pressure conditions, sulfuric acid reacts with m-phenylenediamine to form salt compounds, which are then flashed out along with the steam. During the condensation process, as the concentration of the solution increases, salts become difficult to dissolve, and thus crystallize out to form a solid. These saline substances can burn, and sulfur dioxide gas is produced during combustion, giving off a strongly irritating smell. .