removal efficiency model
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Electrical Engineering, Measurement and Control Technology
Abstract A mathematical model has been developed to predict the theoretical limiting H2S removal efficiency of an electrochemical membrane separator (EMS) in the presence of overwhelming levels of H2O and CO2 (as would be found in syn-gas). Thermodynamic principles gave the minimum potential requirements for cell operation. Factors including electrokinetics, mass transfer, chemical equilibria and internal resistance, occuring with application of current, were incorporated into the prediction. Theoretical predictions, which represent a limiting value, show achievable current efficiencies close to 100% for high H2S levels (1000ppm) at 90% removal. At this same removal level with 100 or 10ppm inlet gas, the predicted maximum current efficiencies dropped, due to concentration effects, to 93% and 40%, respectively. This solidifies the economic importance of obtaining close to 100% current efficiencies at sour gas levels compared to polishing applications where the removal, not the current efficiency, is more important. Predicted cell potentials were consistently in the same range, −0.450 to −0.550V, for all concentration levels at 90% removal. Comparison with experimental data gave good agreement; actual current efficiencies were consistently within 15% of the maximum predicted values at coinciding removal levels. However, actual potentials were lower (less negative) because of hydrogen leakage through the cell membrane. While lower potentials require less power, sulfur production at the anode was reduced.
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