| With the problems of global energy, greenhouse effect, the environmental pollution are becoming increasingly serious, it is necessary to develop of efficient renewable energy, develop controlling technology of nitrogen and phosphorus, and CO2 emission reduction technology. While the construction of biogas project is one of the effective means to solve this problem. At present, China’s biogas industry has made great achievements, but duing to lower quality and biogas slurry in the process of producing biogas is difficult to deal with, making a large number of biogas devices idle, resulting in a huge waste of energy and economic losses.Chlorella is a monadic microalgae by the first artificial cultivation. As an ecological widespread and easily cultured microalgae, Chlorella can absorpt of nitrogen, phosphorus stronger in waste water. Chlorella has a rapid growth rate, So abundant CO? can be fixed during photosynthesis, also cultured in the heterotrophic culture using organic carbon sources for growth and reproduction conditions, and combined with CO2 fixation and purification of biogas.This offers the possibility to remove nitrogen/phosphorus of biogas slurry and biogas purification.On the basis of Chlorella cultivation by the culture medium of biogas slurry as the research object in this study, mainly explored chlorella which is applied to profound treatment of biogas slurry and purification of biogas for the basic application research. The research studies three following aspects.First, the influence of biogas slurry conditions on the growth of chlorella. Experimental results show that slurry concentration and acidity to chlorella growth will have some impact, when the concentration of slurry is 50% and the slurry pH of 6.5 up to the best chlorella growth conditions. Therefore, the use of biogas chlorella processing time can be as close to this condition.Second, different growth conditions for its removal of Chlorella slurry of nutrients, reached the following conclusions:(1) Different microalgae inoculum, light intensity, light quality, and pass into the air and CO2 under different conditions, and chlorella growth conditions are very different to the removal of slurry nutrients. When you select the initial inoculation of algae dry weight (mg/L) for the 200, for the removal of TN and TP has a better effect. (2) Light intensity on nitrogen and phosphorus removal effect of Chlorella sequence is the same:high light intensity> moderate light intensity> low light intensity, but when the light intensity reaching saturation continues to increase light will inhibit the growth of Chlorella, thus their efficiency When the light intensity was 6000 lux, cultured for 7 days, chlorella TN and TP removal efficiency is maximized, the preliminary draw optimum light intensity in the growth of Chlorella biogas purification 6000 lux. (3)Different light quality, when mixed wavelength selected Red:Blue=5:5 and 7:3 TN removal similar relatively high, reaching about 75%; mixing wavelength red:blue=5:5 and 3:7 TP removal rate is about 77% about the same. Integrated nitrogen and phosphorus removal efficiency, hybrid optical quality red:blue= 5:5 nitrogen and phosphorus removal chlorella have reached the maximum; (4) For CO2 and air nitrogen and phosphorus removal effect on chlorella, the results showed through the air and through the removal of CO2 slurry of TN and TP are presented in an increasing trend, but pass on the same day in the amount of total nitrogen residual slurry 1.5% CO2 is significantly-lower than the marsh and culture through the air liquid; biogas chlorella treatment after reaching 89.99% chemical oxygen demand removal.Third, chlorella different growth conditions on the impact of biogas purification. Experimental results show:(1) Chlorella has a high concentration of CO2 is well tolerated; Chlorella in 1.5% CO2 under the best growth in high concentrations of CO2 20% also have good growth; (2) Chlorella of biomass of performance for the CO2 removal increased with chlorella biomass rapidly increased. When cultured for 3 days. Chlorella algae dry weight up to 624 mg/L, CO2 removal rate reached a maximum of 68%, followed by biomass with increasing chlorella gradually reduced; (3) When the slurry concentration is 100%, and most conducive chlorella fixed CO2; (4) different light intensity, light quality, CH4 concentration on Chlorella CO? removal efficiency experiments show that light intensity 6000 lux conditions. mixing red and blue light quality ratio of 5:5, and at a lower concentration of CH4 (45% CH4) conditions. the removal of CO2 up to the maximum. At the time of the experiment were compared before and after the biogas purification rate found under the experimental conditions CH4 content in biogas upgrading from the original 60% to 92.6%. |
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