SYN-GAS QUALITY EVALUATION FOR BIOMASS GASIFICATION WITH A DOWNDRAFT GASIFIER

The purpose of this study was to examine the operation of a commercially manufactured research-scale downdraft gasifier, the Renewable Fuel Gas Generator, Community Power Corporation, Littleton, Colorado. An experimental study of hardwood chip gasification was ran under various operating conditions to determine the effects oil the syn-gas (synthesis gas) produced in the process. The resulting syn-gas had an average LHV(low heating value) of 5.79 +/- 0.52 MJ Nm(-3) (Nm(3) stands for normal cubic meter; i.e., volume of a gas measured at standard temperature and pressure), tar concentration of 14.06 +/- 8.54 mg Nm(-3) and particulale concentration of 3.05 +/- 79 mg Nm(-3). Syn-gas at this level of quality is acceptable for use as a fuel for internal combustion engines and also for other purposes. The process was also very efficient, with a hardwood conversion rate of 2.37 +/- 0.24 Nm(3) kg(-1) and a carbon conversion rate of 98.01% +/- 0.53%. The gasifier's grate temperature had no evident effects oil syn-gas quality and conversion rate within a range of 740 degrees C to 817 degrees C. The particulate contents in pre-filter syn-gas significantly increased when the gas flow rate changed from 36 to 56 Nm(3) h(-1), but no other syn-gas attributes were significantly affected by gas flow rate. When the moisture content of hardwood chips increased, tar content of post-filter syn-gas significantly increased and CO content significantly decreased, but no other attributes were affected. Overall the system, which has extensive electronic controls based oil temperatures and pressures at numerous locations, produced a remarkably consistent high-quality syn-gas regardless of input parameters.