| Summary: | 碩士 === 國立臺中教育大學 === 科學應用與推廣學系環境教育及管理碩士班 === 102 === Emissions form factory’s combustion fossil fuels are regarded as the main culprit of (CO2) emissions, Microalgae is shown good conversion efficiency for CO2 absorption, yet the problem is whether or not the chlorella vulgaris can survive in the environment of flue gas where it is constantly filled with high concentration CO2 and SOx with low pH. What are the optimal conditions for the growth of Chlorella vulgaris? In this study the Chlorella vulgaris will be cultivated under various simulated operating conditions in flue gas environment in order to understand the range of tolerable and optimal conditions for the growth of Chlorella vulgaris.
The main test items in this study include: carbon source, concentration, pH, temperature, illumination ratio, and the Na2SO3 concentration variation test under different pH in order to simulate the conditions in flue gas. It can then be divided into batch cultivation (with the addition of carbon source and two times aerations, one in the morning and the other in the night) and continuous aeration cultivation.
Under batch cultivation, the carbon source most suitable for the growth of Chlorella vulgaris is CO2, and the CO2 concentration of 15% has led to the best growth rate of 25.5 mg/L/day. It is followed by NaHCO3, where the concentration of 40 mmol has led to the best growth rate of 13.1mg/L/day. Na2CO3 is the worst carbon source, where the concentration of 40mmol has led to the best growth rate of 11.5mg/L/day. The Chlorella vulgaris that underwent one aeration in the morning and the other aeration in the night can withstand up to 35% of CO2, and pH 6 is the most suitable environment for the growth of Chlorella vulgaris. The growth rate of Chlorella vulgaris with higher or lower pH will be gradually reduced, and begin to be inhibited once it reaches pH 4 and 9. A temperature of 25℃ is the most suitable for the growth of Chlorella vulgaris. The growth rate will be gradually reduced when the temperature rises and declines, and Chlorella vulgaris will be inhibited once the temperature reaches 15 and 35℃. Full-day illuminated exposure will lead to the best cultivation production and production rate of Chlorella vulgaris, yet in terms of the Chlorella vulgaris production rate per unit time of illumination (mg/L/day/time of illumination), it is the highest and most economic with an illumination ratio of 1:1. As pH 6, the Chlorella vulgaris can withstand 50mmol of Na2SO3. As pH 5, Chlorella vulgaris can withstand 20mmol of Na2SO3, and as pH 4, Chlorella vulgaris can only withstand 10mmol of Na2SO3.
The continuous aeration cultivation of Chlorella vulgaris are shown identical results of pH, temperature, and illumination ratio to the batch cultivation, while it can withstand CO2 concentration of 30%, which is lower than that of the cultivation with one aeration in the morning and the other aeration in the night. The best growth rate of Chlorella vulgaris is 31.4mg/L/day as CO2 concentration of 15%. Chlorella vulgaris of pH 6 can withstand 40mmol of Na2SO3, which is lower than the cultivation test with one aeration in the morning and the other aeration in the night.
Operation conditions regression of Chlorella vulgaris :
x＝0.98∣24- a∣(5.88* S /(91.3 + S + S 2/ 7.16) g) ×c∣pH-6∣×d∣T-25∣
x: Cell Density (g/L)
a : Illumination time (≥12h)
s:CO2%(≤35%)
c: pH ≥6，c=0.90；pH <6，c=0.82(pH 4~10)
d: temperature ≥25℃，d=0.96；<25℃，d=0.94(15℃~35℃)
V＝0.96∣24- a∣(0.161*S/(0.656 +S+S2/1.16)) ×c∣ pH-6∣×d∣T-25∣
V: growth rate (mg/L/day)
a : Illumination time (≥12小時)
s:CO2(mg/L；濃度≤35%)
c: pH ≥6，c=0.94；pH <6，c=0.87(pH 4~10)
d: temperature ≥25℃，d=0.96；<25℃，d=0.95(15℃~35℃)
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