평판형 광생물반응기를 이용한 미세조류 배양제어시스템 개발

Abstract

In recent years, as the indiscriminate use of the fossil fuel has caused serious environmental pollution such as the shortage of energy and global warming, new renewable energy has been studied. New renewable energy made by microalgae makes carbon dioxide reduce effectively as well as produces biofuel. It makes also all kind of functional materials as a by-product. In this thesis, microalgae cultivation control system was developed to cultivate massively and the flat panel photobioreactor for 200L was designed. Dunaliella salina with high lipid contents was selected for biodiesel production. Growth curve was approximated by Gompertz model, Logistic model, and Baranyi model, which is microbial growth prediction model to cultivate continuously. Gompertz model was suitable to predict the growth curve of Dunaliella salina since it has the highest R-squared coefficient. The open loop system was simulated using the Gompertz model for development of continuous culture system. The experimental culture data was suitable to the simulation data. Next, on-off control system was simulated in the above value of parameter to compare with the experimental data. D. salina was cultivated by on-off controller at the peristaltic pump speed of 12.2RPM which the dilution rate is 1.0day-1 for turbidostat. This dilution rate was the maximum specific growth rate which was estimated by Gompertz regression model. The resulted dilution rate during the operation was actually 0.567day-1 and the biomass productivity was 1.08g/L/day. In case of a peristaltic pump speed of 6.1RPM which dilution rate is 0.5day-1, the resulted dilution rate was actually 0.411day-1. These differences between the two resulted dilution rate according to the pump speed were caused by sensor sensitivity. PI control system was also simulated by the Ziegler-Nichols which was a heuristic method of tuning the PID controller. After finding start point of tuning, the proportional and integral gain were found by the trial and error method. To scale up the flat panel photobioreactor, the material with high optical transmittance was investigated for the case of PBR and the bending deformation induced by hydrostatic pressure was predicted by the finite element method. The rib was added sequentially in the position of the maximum bending moment until the maximum deformation was less than 0.1% of length. The number and position of the rib were evaluated and thickness of the rib was also studied. The simulative results show that rib with a thickness of 9mm has to install 6EA in order to prevent bending deformation.