Sour Water Stripping Unit Simulation and Design

Why 2 columns? When the existing Sulfur Recovery Unit is limited by the amount of NH3 When is necessary to recover only HN3 When Refinery shall process a crude oil with large amount of nitrogen. Key parameter: operating pressure of H2S Stripper – remember that if the pressure is increasing and heat is introduced to system the solubility of H2S is decreasing but NH3 solubility is increasing! Recommended value is 9-10 barg to keep NH3 in water for H2S Stripper (first column who remove H2S) and classical 0.7-1.3 barg for HN3 Stripper. H2S Stripper 10 theoretical trays / 30 real and NH3 Stripper 12 theoretical stages / 36 real, do not use in simulation more than 15 theoretical trays and avoid using direct (live) stripping steam instead of reboiler. Recycle back the sour water from KO drum to feed, upstream degassing vessel, size it with minimum 20 minutes as holdup time to allow separation of hydrocarbons from degassing drum, provide a buffer tank Downstream degassing drum to avoid composition spikes to strippers, add top pumparround using an air cooler and provision shall be foreseen for chemical injection. Remember that for H2S/NH3 strippers system factor shall be set to 0.65, use the flooding factor of maximum 80% and tray spacing 600 mm – foaming system. If NH3 could not be released from water add NaOH to change pH from acid in slightly basic, not exceed pH of 10 to avoid possible issues in downstream units, recommended pH is 9 – the concentration of NaOH around 5-8 wt.% / add 3-4 ppm wt. of NaOH for each ppm of NH3 above specification in stripped water. Keep top operating temperature for NH3 stripper higher than 90°C to avoid NH4HS formation, if top pumparround is present pay attention at tubes metal wall temperature to not go below 70°C. Enjoy! PS: Phenols could not be completely removed by SWS unit - by steam stripping maximum 60-70% of phenols could be stripped from sour water! #innovation #sustainability #research #energy #training #technology #business #engineering #design #future