Hydrothermal processing of swine manure to oil using a continuous reactor system: Effects of operating parameters on oil yield and quality

A continuous-mode hydrothermal process (CHTP) reactor was developed to convert swine manure into oil. The effects of operating parameters on oil yield and quality were investigated to determine the optimal condition for the continuous-mode process. Operating temperature, pressure, residence time, and the use of carbon monoxide as a process gas were all found to affect oil yield. Results showed an interaction between the operating temperature and pressure. Oil yield increased with hydraulic residence time, but a diminishing benefit was observed beyond 60 min. A slight decrease in yield was found when carbon monoxide was used. The highest oil yield of 70% (of volatile solids) was in the region where temperature was about 300°C and pressure was 10 MPa. Increasing the temperature from 285°C to 305°C was found to increase the carbon content, heating value, and benzene solubility of the oil. However, increasing the pressure negatively affected both the carbon content and heating value of the oil. The addition of carbon monoxide was found to be beneficial in increasing the carbon content of the oil by 7.4% and improving its solubility to benzene. The hydrogen, nitrogen, and sulfur content of the oil were relatively constant for all test cases, with values of 9.6 ± 0.4%, 3.9 ± 0.3%, and 0.3 ± 0.1%, respectively.