Sour-water absorber/stripper

One of my favorite tricks on hydro-desulfurizer recycle gas HjS absorbers or sour water strippers, or any tower that has far too many trays, is to double the tray spacing. This permits me to increase tower capacity by 40 to 50 percent. Recycle gas H S absorbers, especially, have typically four times the number of trays required (see my book. Process Engineering for a Small Planet, WUey, 2010). 

PC Science and Technology Figure 1. Sour-water absorber/stripper VLE (4)... 

Fig. 5.6. PHOSAM-W-process. (a) Sour water stripper, (b) absorber, (c) 1-7 condenser/heat exchanger, (d) stripper, (e) fractionator... 

Systems subject to low surface tension (de-ethanizers, refrigerated absorbers) or particulates (amine regenerators, sour water strippers) are known to flood prematurely due to foaming. However, many other relatively clean, higher surface tension systems also appear to cause premature flooding. 

Vapor leaving the top of the absorber is next passed through an after-condenso- where a small portion of the water vapor is condensed. The resulting small stream of sour water is recycled to the sour water stripper. Rich solution from the absorber is recycled around the bottom of the absorber to maximize its loading with anunonia. The net rich solution product is fed to the regeneration stage which is similar to that of the Phosam process. 

The wet solvent from the centrifuge is combined with the overflow stream from the surge tank and is pumped to a solvent stripper, where the water (3.5 wt%) is stripped from the solvent to maintain the water balance in the system. The water-vapor flow in the stripper removes unreacted H2S and most of the other gases, such as CO2, co-absotbed in the solvent. Most of the lean solvent exiting the bottom of the solvent stripper is used in the SO2 scrubber to absorb the SO2 from >he combustion gas leaving the furnace. The overhead vapor is condensed in a partial condenser. Approximately 65% of the condensate is fed to a sour-water... 

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