Syn-Gas Quality Evaluation for Biomass Gasification with a Downdraft Gasifier

摘要

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 run under various operating conditions to determine the effects on 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 particulate concentration of 3.05 ± 1.79 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 on syn-gas quality and conversion rate within a range of 740°C to 817°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 on temperatures and pressures at numerous locations, produced a remarkably consistent high-quality syn-gas regardless of input parameters