Removal of NH 3 from Biomass Gasification Producer Gas by Water Condensing in an Organic Solvent Scrubber

Producer gas from biomass gasification contains NH 3, H 2 S, and high molecular weight organic compounds (tars), which must be removed prior to the gas utilization step. A highly effective approach toward the removal of tars is absorption into organic solvents. As a secondary effect, condensation of water takes place in the scrubber, allowing removal of gaseous trace components such as NH 3 and H 2 S from the gas stream. The present work focuses on the coabsorption of NH 3 and CO 2 into condensing water. The general aim is to decrease the clean gas NH 3 concentration by appropriate adjustment of the operating parameters without additional gas-cleaning steps. A mathematical model of a countercurrent column, which covers mass and energy balances, gas−liquid equilibrium, and electrolyte dissociation, is presented. The scrubber geometry does not enter the model; therefore, it promises universal applicability. Property data on electrolyte dissociation and Henry's law constants are taken from the literature. A computer code has been developed in order to study the sensitivity of NH 3 removal toward certain process parameters. The results agree well with data measured at the 2000 Nm 3 /h (gas load) scrubber at the biomass gasification plant in Guessing, Austria.