Determination of KLa Values Using CO2 Mass Balance Technique in a Coal Desulfurization Bioreactor

Abstract

Techniques based on O[sub 2] measurements such as gassing out or oxygen balance techniques which are generally used in determining K[sub L]a values are hardly applicable when a solid phase is present in the medium or during a fermentation process. In this study a new technique was used in achieving K[sub L]a values. This technique is based on the continuous response measurement of the outlet gas phase to a CO[sub 2] step change in the inlet. This method was applied to determine K[sub L]a values in a bubble column where a microbiological coal desulfurization process takes place using Thiobacillus ferrooxidans. To check the results obtained by using the CO[sub 2] mass balance technique, a series of runs were carried out to find the K[sub L]a value in an air/water system. The results were compared with previous ones already reported by other authors, and they were seen to be in good agreement. Other K[sub L]a values were achieved by using an inorganic salt solution as a growth medium for the bacterium and also as a liquid medium in the desulfurization experiments. It was found that K[sub L]a increased as the salt concentration increased. When a solid phase was introduced into themore » reactor K[sub L]a decreased as the amount of the solid present increased; however, K[sub L]a increased when the superficial gas velocity increased. Finally, other K[sub L]a values were obtained during various coal desulfurization runs. It was found that K[sub L]a remained constant throughout the reaction time, because T. ferrooxidans does not produce any substances that can alter the medium viscosity. It was also found that this method of determining K[sub L]a can be used during bacterial treatment without interfering with the microorganism action.« less