Scrubber system improvement for sulfur containing gas streams

1. In a wet scrubbing process for treating gaseous industrial process streams which may contain one or more of SO 2 , SO 3 , H 2 SO 4 and mixtures thereof, wherein said wet scrubbing process is arranged to condition said gaseous process stream by at least quenching said gaseous process stream with a countercurrent flow of liquid derived from a circulating liquid stream with the result that SO 3 and H 2 SO 4 pass from the gaseous process stream into the circulating liquid stream, and wherein said circulating liquid stream includes (i) one or more purge streams configured to remove a portion of the circulating liquid having a concentration of H 2 SO 4 from the process, and (ii) at least one liquid make-up stream configured to replace the portion of the circulating liquid that has been removed from the circulating liquid stream, the improvement comprising:

1) controlling the flow of liquid make-up whereby the concentration of H 2 SO 4 in the purge stream is increased to a useful value; and

2) filtering the purge stream to remove unwanted contaminants to yield a clarified purge stream.

2. The improvement of claim 1 which includes an additional step of mixing the clarified purge stream with a sulfuric acid product stream.

3. The improvement of claim 1 or claim 2 wherein filtering is accomplished by passing the purge stream through a silicon carbide membrane.

4. The improvement of claim 3 wherein quenching said gaseous process stream with a countercurrent flow of liquid is accomplished by passing said gaseous process stream through a reverse jet scrubber.

5. The improvement of claim 4 wherein the circulating liquid is a weak aqueous sulfuric acid stream.

6. The improvement of claim 5 wherein the concentration of the weak aqueous sulfuric acid stream is less than 70 wt %.

7. In a spent sulfuric acid recovery process of the type having a gas cleaning section for treating a stream of gas, which may contain one or more of SO 2 , SO 3 , H 2 SO 4 and mixtures thereof, to remove H 2 SO 4 by contacting the stream of gas with a countercurrent flow of liquid derived from a circulating liquid stream with the result that SO 3 and H 2 SO 4 pass from the gas stream into the circulating liquid stream, and wherein said circulating liquid stream includes (i) one or more purge streams configured to remove a portion of the circulating liquid having a concentration of H 2 SO 4 from the process, and (ii) at least one liquid make-up stream configured to replace the portion of the circulating liquid that has been removed from the circulating liquid stream, the improvement comprising:

1) controlling the flow of liquid make-up whereby the concentration of H 2 SO 4 in the purge stream is increased to a useful value; and

2) filtering the purge stream to remove unwanted contaminants to yield a clarified purge stream.

8. The spent sulfuric acid recovery process of claim 7 wherein the flow of liquid make-up in step 1) is controlled with a control valve that is coupled to a strength analyzer and programmed to maintain the concentration of sulfuric acid in the circulating liquid stream.

9. The improvement of claim 7 which includes the additional step of mixing the clarified purge stream with a sulfuric acid product stream.

10. The improvement of claim 7 or claim 8 wherein filtering is accomplished by passing the purge stream through a silicon carbide membrane.

11. The improvement of claim 7 , claim 8 , or claim 9 wherein contacting said gas stream with a countercurrent flow of liquid is accomplished by passing said gas stream through a reverse jet scrubber.

12. The improvement of claim 11 wherein the circulating liquid is a weak aqueous sulfuric acid stream.