Comparison of Different Loop Bioreactors Based on Hydrodynamic Characteristics, Mass Transfer, Energy Consumption and Biomass Production from Natural Gas

The performance of a forced-liquid Vertical Tubular Loop Bioreactor (VTLB), a forced-liquid Horizontal Tubular Loop Bioreactor (HTLB) and a gas-induced External Airlift Loop Bioreactor (EALB) were compared for production of biomass from natural gas. Hydrodynamic characteristics and mass transfer coefficients were determined as functions of design parameters, physical properties of gases as well as operational parameters. Moreover, energy consumption for different gas and liquid flow rates was studied. In the EALB, kinematic viscosity (υg) showed its significant role on mixing time, gas hold-up and kLa and the diffusion coefficient of gas in water (Dg) had a remarkable effect on kLa. It was observed from experimental results that the performance of the VTLB was the best for biomass production. Furthermore, the volumetric mass transfer coefficients for air and methane were determined at different geometrical and operational factors. New correlations for mixing time, gas hold-up and kLa were obtained and expressed separately. Also, the different ratios of methane and air were measured and compared for optimum growth in the VTLB, HTLB and EALB.