The challenges of designing grass root sulphur recovery units with a wide range of H2S concentration from natural gas

RATE was recently awarded a contract to license a new grass roots sulphur recovery project including design of the Acid Gas Removal and the Sulphur Recovery Unit, Tail Gas Treating, water dew point control unit, Thermal Oxidizer (incineration system) and the Liquid Sulphur Degassing Units for a Sour Gas Field Development (SGFD) in Asia. allenge in this project was to deal with a wide range of feed gas compositions of H2S and CO2 while also dealing with a lot of impurities such as carbonyl sulfide (COS), heavy hydrocarbons, mercaptans, and benzene, toluene, xylene (known as BTEX) where the operation of the SRUʹs with the lean gas and impurities are difficult. ed Gas Composition to the Acid Gas Removal Unit (AGRU) consists of number of cases. The design had to be able to operate in all of these cases while achieving a stable operation and meeting the performance guarantees and environmental regulations. S concentration to the AGRU varies from 2.3% to 5%, the CO2 concentration varies from 3% to 6%, benzene from 40 ppmv to 90 ppmv, toluene from 45 ppmv to 220 ppmv, xylene from 20 ppmv to 150 ppmv, carbonyl sulfide (COS) from 25 ppmv to 70 ppmv, and heavy hydrocarbons up to C50+, mercaptans from 15 ppmv to 50 ppmv plus many pseudo components according to the gas analysis from more than 100 wells. The H2S concentration to the sulphur Recovery unit varies from 30% to 47% and CO2 ranges varies from 58% to 43% respectively. The gas pressure was around 100 barg at 50 °C. les gas has to meet the following performance guarantees.•  ppmv ss than 1.7% max ppm wt maximum, c sulphur 50 ppm- wt maximum, total sulphur 60 ppm wt maximum  ppmv ss than 1.7% max ppm wt maximum, c sulphur 50 ppm- wt maximum, total sulphur 60 ppm wt maximum lphur Recovery, Tail Gas Treating, Thermal Oxidizer, and Liquid Sulphur Degassing have to meet the following performance guarantees.• r Recovery minimum 96%, l SRU + TGU less than 50 ppmv of SO2 at stack sulphur Degassing, less than 10 ppmw of H2S r Recovery minimum 96%, l SRU + TGU less than 50 ppmv of SO2 at stack sulphur Degassing, less than 10 ppmw of H2S s paper, we will discuss the design features of the units and reasons why they were selected. We will discuss the options that we considered to design this unit, including the solvent evaluation & selection, the impact of H2S/CO2 ratio on the AGRU and the SRU design, and the selected optimum scheme of the Sulphur Recovery Units, and the TGU to meet the performance guarantees for all 10 cases including the operating and the capital costs comparison.