A novel porous nickel-foam filled CO absorptive photobioreactor system to promote CO conversion by microalgal biomass.

In order to solve problems associated with a short residence time and low conversion efficiency when CO gas is aerated directly into raceway ponds, a novel porous nickel-foam filled CO absorptive photobioreactor system was developed to promote CO conversion to NaHCO in a short time to improve photosynthesis of microalgal cells. Numerical simulation showed that the porous nickel-foam promoted the NaCO solution radial velocity and CO volume fraction in the CO absorption reactor, which enhanced the reaction rate of CO gas and soluble NaCO. The conversion efficiency of CO gas to soluble NaHCO gradually increased with an increasing nickel-foam pore diameter and a decreasing CO gas outflow rate, while it first increased and then decreased with an increasing relative nickel-foam height in the CO absorption reactor. The conversion efficiency from soluble NaHCO to microalgal biomass first increased and then decreased with an increasing nickel-foam pore diameter (peaking at 2 mm) and relative height (peaking at 0.24); and CO gas outflow rate (peaking at 2 L/min). The chlorophyll fluorescence measurements showed that a sufficient HCO supply promoted the quantum ratio used for electron transfer (from 0.19 to 0.23) and the maximum photochemical efficiency (from 0.48 to 0.52), resulting in an increased biomass growth rate (by 1.1 times) when the nickel-foam pore diameter increased from 0.1 to 2 mm.