OPERATING TEMPERATURE AND RETENTION TIME EFFECTS ON THE THERMOCHEMICAL CONVERSION PROCESS OF SWINE MANURE

A thermochemical conversion (TCC) reactor was developed to process swine manure for waste reduction and energy production. The operating temperature and retention time are the two key parameters affecting the process. Carbon monoxide (CO) was employed as the reductive reagent. The investigated ranges of the operating temperature and retention time were 275°C ~ 350°C (corresponding operating pressures were 7 ~ 18 MPa) and 5 ~ 120 min, respectively. The pH value of the fresh swine manure (pH= 6.1), CO to VS ratio (CO:VS = 0.07 by weight or CO initial pressure p ini = 690 kPa), and total solids content (TS = 20%) were kept constant for all the experiments in this study. No extra catalyst was added in the experiments because of the presence of plentiful minerals and carbonates. The operating temperature was the most important factor affecting the TCC process. No substantial oil product yield was achieved unless the temperature reached 285°C or above. Temperature higher than 335°C led to solid char formation. Retention time affected the completeness of the TCC process. The retention time for achieving high oil yield and quality was largely dependent upon the operating temperature levels. The suggested operating temperature and retention time for the TCC process are 295°C to 305°C and 15 to 30 min, respectively.