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ISSI's iron oxide production begins when waste acid is pumped to a venturi scrubber where it is preheated and concentrated by contacting the hot gases from the spray roaster. Concentrated waste acid undergoes the following chemical reaction to produce iron oxide and hydrochloric acid:
Iron oxide is discharged from the bottom of the spray roaster while the hot gases leave from the top. Iron oxide is cooled and conveyed pneumatically from the bottom of the spray roaster to the storage bin. The hot gases from the top of the spray roaster, after passing through the venturi scrubber, flow to the absorber. The HCL is then absorbed preferentially in recirculated water from the scrubber to produce regenerated hydrochloric acid. The acid is pumped back to the pickle line for reuse. Exhaust gases are scrubbed either in a single-stage water scrubber or two-stage water and caustic scrubber before being discharged to the stack by the exhaust fan. |
