Study On Denitrification And Carbon Fixation From Flue Gas Via Microalgae

Industrial flue gas emissions lead to air pollution and greenhouse effect that has been a serious threat to survival and development of the human.Purification of flue gas using microalgae with low cost,easy to operate and environment protection,becomes the current research hotspot.However,this method exists some problems,such as low carbon sequestration rate,microalgae is susceptible to deactivation,the process product and accumulate wastewater,and so on.Based on these problems,this paper focuses on the pretreatment process,microalgae absorption process,algae culture recycling process.The main results are as follows:(1)When the flue gas contained 500ppm NO with 0.1 vvm flow rate,using pH=10?11 alkali solution to absorb,the traditional process that alkaline solution absorbs NO only got absorption rate about 29%.As for NO pretreatment of ozone oxidation,More than 90%NO absorption rate can be achieved when the molar ratio ofO3/NOis 1.5-2.(2)Absorption of flue gas using alkaline waste liquid(Spirulina culture medium after harvest),the C?32'/HC?3 buffer system was able to maintain the pH value of algae culture in the appropriate alkaline range,and get rid of the acidification of algae.The ability of environmental adaptation and biological activity of Spirulina was significantly improved.The cells maintained the ideal growth and carbon sequestration rate under the concentration of 10%?20%C02and 0.5-1 vvm flow rate of flue gas.(3)The denitrification and carbon sequestration via microalgaes in different growth environments were studied,which indicated that the differences of pH range and the ability of absorption and transformation of nitric oxide and carbon dioxide in algae significantly affected the efficiency of denitrification and carbon sequestration.(4)The intermittent aeration process significantly enhanced the biological activity and denitrification carbon sequestration rate.The maximum biomass of 12h flue gas:12h air intermittent ventilation was 9%higher than that of continuous ventilation when flue gas with 20%C02,500ppm NO and 0.3vvm flow rate flew into the bubble column reactor.The denitrification rate and the carbon sequestration rate of continuous aeration was about 90%and 2.8%,respectively.The denitrification rate and the carbon sequestration rate of intermittent aeration was about 93%,6.7%,respectively.(5)Circulating absorption of flue gas using Spirulina waste liquid,this process not only can save water,but also the deep treatment of the wastewater.The concentration of inorganic carbon ions,TN and TP in the wastewater was reduced to 18%,27%,and 30%of the original concentration,respectively.The average biomass could reach 3.5g/L,and in the third cycle batch had the highest biomass 3.8g/L.The average biomass of the normal culture was 3.8g/L.(6)A multi-layer reactor was designed,the denitrification rate and the carbon sequestration rate of flue gas(20%CO2,500ppm NO,0.3wm)is up to 97%and 10%,respectively,in which the biological nitrogen fixation rate was 90%and the biological carbon sequestration rate was 9%.