SOUR WATER STRIPPER

Contrary to Claus units in which sour water stripper gas (SWS) can create operational problems, processing SWS gas in a LO CAT® unit is actually beneficial. Reactions in a LO CAT® process occur in the liquid phase and are very rapid; however, the mass transfer of the H2S from the gas phase to the liquid phase is relatively slow, and is thus the rate limiting step in the process. One method of increasing the mass transfer rate is to increase the alkalinity or pH of the circulating liquid solution. This is usually accomplished by adding caustic in the form of NaOH or KOH to the system, which creates an operating expense; however, due to the ammonia, which is usually contained in the SWS gas, no caustic addition is required when processing SWS gas, thus the operating cost is reduced. The first application of the LO CAT® technology on a Sour Water Stripper Offgas stream was in 1981, which continues to be operated to this day. Presently the LO CAT® technology can be found processing SWS gas in almost a dozen facilities worldwide; with installations in China, India, and the USA.