TREATMENT OF BENFIELD PROCESS CONDENSATE FOR REMOVAL OF DISSOLVED CHEMICALS LIKE CO2 AND NH3 FOR REUSE

Abstract

CO2 Removal from Syngas is an important step before ammonia production to enhance the life of iron catalysts in ammonia reactor. At FFBL, hot potassium carbonate (Benfield) solution is used to dissolve CO2 from syngas. This solution is regenerated through steam and the overhead of carbonate regenerator is separated into CO2 rich vapor stream and Benfield process condensate PC. About 84000 kg/h of condensate is produced, 1/4th of which is dumped into the Indus River. According to environmental and economic aspects, it is beneficial to reuse this water as boiler feed instead of discharging it as an industrial effluent. Although free of major impurities like total dissolved solids TDS and total suspended solids TSS, Benfield PC contains two dissolved gases CO2 and NH3 which render it unfit for boilers. Several biological, chemical, and physical processes were reviewed including nitrification-denitrification, ion-exchange resins, membrane separation, steam stripping, and flash distillation. Steam stripping was found to be a commercial and proven technology for water degassing even at very low concentrations. In this project, a cost-effective stripping system with economized feed preheating has been optimally designed to bring Benfield PC within boiler feed specifications