ARE MEMBRANES THE ANSWER TO ODOR?

A microporous hollow fibre membrane operating in non-wetted mode has been applied to the removal of hydrogen sulphide from gas streams. The case studies under investigation were (i) H2S absorption within single passage through the membrane and (ii) H2S absorption with recycle. Counter-current flow configuration was considered with the test contaminant passing through the shell-side of the membrane while liquid absorbent was flowing inside the fibre lumens. The chemistry and the kinetics of H2S in an alkaline environment were studied and their impact on the design of scrubbing systems has been investigated. H2S absorption was simulated for each case with a numerical model describing the transfer of mass from the gas phase to the liquid either as physical transport or reactive absorption of species. For flow in the tube-side, a fully developed parabolic velocity profile was assumed, while Happel's free surface model was applied to characterise the shell-side flow. Experimental and theoretical studies describing H2S absorption were conducted within a liquid pH range of 7 to 13. In most cases, the model predictions correlated closely with the experimental observations with a maximum deviation of ∼1%. Overall, the gas phase velocity and the liquid pH were crucial in determining the system's performance. Correlation of the mass transfer data revealed that the hydrodynamic parameter (Gz) increases as a function of pH indicating the strong impact of the gas velocity on the transport process.