在"碳中和"国家战略背景下,微藻减排烟气CO2技术以其经济可持续的特点广受关注.微藻减排烟气CO2高效、低成本和规模化发展过程中,为了提高螺旋藻过滤采收后循环液中NaHCO3质量浓度,提高螺旋藻固定煤化工厂烟气CO2速率,研制一种编制网式曝气器产生微米级CO2气泡,延长烟气CO2与循环液中Na2CO3的反应时间,促进高效生成NaHCO3;通过双指示剂法测试藻液中Na2CO3和NaHCO3质量浓度,通过显微镜测试了螺旋藻生长过程中藻丝螺距和长度变化规律,通过植物效率分析仪测试螺旋藻细胞的叶绿素OJIP荧光诱导动力学曲线.研究结果表明:烟气CO2通过编制网式曝气器反应后,跑道池中藻液的NaHCO3质量浓度比相同条件下通过传统曝气条的NaHCO3质量浓度提高43％;采用该循环液作为新鲜培养基,在跑道池中培养螺旋藻72 h后,螺旋藻的藻丝螺距和长度分别提高16％和12％,螺旋藻细胞暗适应下PSII最大量子产率和单位反应中心吸收光能分别提高21％和28％,最终导致螺旋藻生物质密度比未补充烟气CO2前提高15％.烟气CO2通过编制网式曝气器可转化为更多NaHCO3,从而促进了螺旋藻的生长固碳速率,为微藻固碳技术的高效、低成本规模化应用提供了技术设备选择.

A staggered woven mesh (SWM) aerator equipped with three variable-micropore layers was developed to enhance the CO2 conversion into HCO3- in a recycling water pipeline for promoting CO2 utilization efficiency and Arthrospira growth in large-scale raceway ponds. The input CO2 gas was broken into smaller bubbles (0.78- 2.43 mm) through the first-stage shear with axial rectangles, second-stage shear with radial rectangles (equivalent pore diameter = 150 μm), and third-stage shear with uniform micropores. A high-speed camera (MotionXtra HG-100K CMOS) and an Image J image processing software were employed to capture the bubble pictures. Compared to the traditional steel pipe (TSP) aerator, the bubble generation diameter and time in the SWM aerator reduced by 72.3% and 48.6%, respectively. The optimized structure (ε = 14, pore = 23 μm) of the SWM aerator promoted the carbonization efficiency and HCO3- conversion efficiency into biomass by 78.6% and 64.6% than the TSP aerator. Further, the chlorophyll fluorescence and biomass measurements showed an increase in the actual photochemical efficiency (analyzed by Hansatech FMS1 chlorophyll fluorescence instrument) and biomass yield by 1.8 times and 80.1%.

In order to solve problems associated with a short residence time and low conversion efficiency when CO2 gas is aerated directly into raceway ponds, a novel porous nickel-foam filled CO2 absorptive photobioreactor system was developed to promote CO2 conversion to NaHCO3 in a short time to improve photosynthesis of microalgal cells. Numerical simulation showed that the porous nickel-foam promoted the Na2CO3 solution radial velocity and CO2 volume fraction in the CO2 absorption reactor, which enhanced the reaction rate of CO2 gas and soluble Na2CO3. The conversion efficiency of CO2 gas to soluble NaHCO3 gradually increased with an increasing nickel-foam pore diameter and a decreasing CO2 gas outflow rate, while it first increased and then decreased with an increasing relative nickel-foam height in the CO2 absorption reactor. The conversion efficiency from soluble NaHCO3 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 CO2 gas outflow rate (peaking at 2 L/min). The chlorophyll fluorescence measurements showed that a sufficient HCO3- 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. (C) 2020 Elsevier B.V. All rights reserved.