No abstract

A myoglobin assay for measuring concentrations of dissolved carbon monoxide (CO) from an artificial synthesis gas blend (20% CO, 18% CO2, 52% N2, and 10% H2) was utilized to determine volumetric CO−water mass-transfer rates in a 0.211-m-diameter stirred-tank reactor (STR). The data are well correlated using the power density and superficial gas velocity, but this correlation is valid only for this STR size. A gas−liquid scale-up model developed for dissolved oxygen mass-transfer rates using air was used to develop a CO−liquid scale-up model for syngas fermentation. The model is applicable in the STR hydrodynamic range associated with after-large-cavity (ALC) formation and assumed to hold for other STR sizes. A myoglobin assay for measuring concentrations of dissolved carbon monoxide (CO) from an artificial synthesis gas blend (20% CO, 18% CO 2 , 52% N 2 , and 10% H 2 ) was utilized to determine volumetric CO-water masstransfer rates in a 0.211-m-diameter stirred-tank reactor (STR). The data are well correlated using the power density and superficial gas velocity, but this correlation is valid only for this STR size. A gas-liquid scaleup model developed for dissolved oxygen mass-transfer rates using air was used to develop a CO-liquid scale-up model for syngas fermentation. The model is applicable in the STR hydrodynamic range associated with after-large-cavity (ALC) formation and assumed to hold for other STR sizes.

A general scale-up correlation is developed for the volumetric gas-liquid mass transfer coefficient (kLa) in stirred-tank reactors (STRs) for oxygen transport using results from the literature and the current study. Power data for the dispersion of air in water by a six-bladed Rushton impeller are obtained by measuring electrical power, and a gassed power correlation is proposed. A correlation for gas-liquid mass transfer based on the energy input criteria of the form kL a = cl (Pg Iv) Cl u: fit the data well, but, in general, is dependant on flow regime and the vessel size. The volumetric mass transfer coefficient (kLa) is correlated on the basis of the relative dispersion parameter (NIN co) for similar impeller hydrodynamics and operating regimes. A stirred-tank reactor scale-up technique from bench-scale (T = 0.211 m and D/T = 0.35) to industrial-scale (up to T = 2.7 m) is proposed using a normalized hydrodynamic flow regime map and shown to be useful in understanding the range of operational conditions for the successful scale-up of stirred tank reactors. The experiments show that the scale-up model can be applied for a single and or multi-gas component mass transport to liquids if the STR is operated in the same hydrodynamic regime. A method for determining dissolved carbon monoxide concentrations from artificial syngas is developed and the volumetric gas-liquid mass transfer rates are determined. The gas-liquid scale-up model is used in carbon monoxide mass transfer scale-up for syngas fermentation in a STR. Carbon monoxide mass transfer rates obtained in this work are predicted from those of air correlated from literature. A STR scale-up model is extended to other reactor types such as air lift reactors and bubble columns in mixing applications, and the corresponding gas-liquid scale-up model is suggested.