DESIGN AND OPERATION OF SOUR NGL TREATING UPGRADE AT THE SEMINOLE GAS PROCESSING PLANT

摘要

By 2001, the operation of the Seminole Gas Processing Plant's SRU's (Sulfur Recovery Units) had deteriorated to the point that catalyst life had fallen to six months and the units could not meet emission requirements due to frequent upset conditions. The problem was not with the SRU's themselves, but with the feed gas, which was too high in both CO2 and hydrocarbons. The SRU feed gas was about 59% CO2 which made operation difficult and the C6+ was about 0.025%, which fouled the Claus catalyst of the SRU's. The CO2 and H2S were removed from a liquid NGL stream with amine in a liquid-liquid absorber, which contributed to high absorption of hydrocarbons into the amine. Three alternatives were considered to resolve the problem. These were: 1. Treat the SRU feed to remove much of the CO2 and hydrocarbons. 2. Eliminate the SRU's entirely by selectively absorbing the H2S into the plant's cooling tower blowdown water and inject the water into disposal wells. 3. The chosen option involved selective H2S absorption using MDEA in a gas-liquid absorber. This was followed by MDEA being used non-selectively in both gasliquid and liquid-liquid absorbers. Start up issues and actual system operating performance data are also included.