Evaluation of Syngas Storage Under Different Pressures and Temperatures

The objective of this research was to study the syngas storage characteristics in terms of any variation in composition of H2, CO, CH4, CO2, and N2 under two pressures (2758 and 8274 kPa) and three temperatures (-288K, 288K, and 318K). We also evaluated tar, particulate, and moisture content of the stored syngas. Syngas generated from a down-drift gasifier using 95% hardwood chips as the feedstock contained an average of 17.0% H2, 23.9% CO, 1.4% CH4, 11.0% CO2, and 46.7% N2. The compositional elements of the stored syngas under different pressures and temperatures were periodically determined for a three-week period of storage. The statistic model of a single-factor experiment with repeated measures on treatments was used to perform the data analysis with the SAS program. Statistic analysis revealed that the temperature range from -288 to 318K had no effects statistically on the major syngas composition at the tested pressures. Pressures up to 8274 kPa had no effects statistically on the major syngas composition at the tested temperatures. The variations of the syngas components measured were probably due to analysis and instrumental errors. At both pressures, the CO composition had a bigger variation than other components and, as the temperature varied, the CO composition varied more than the other components. Mechanisms of the relatively bigger variation of the CO concentration were not fully understood and may be partially contributed to the pressure and temperature variations. Tars were detected in the storage cylinders after washing with acetone solution, which indicated that the tars were deposited on the inside wall of each storage cylinder. The amount of tars was correlated with the temperature. The low storage temperature precipitated more tars under pressure during storage. Thus this study showed that syngas could be stored with no major adverse affects caused by temperatures of -15C to 45C. Also, pressures up to 8274 kPa had no effect on syngas composition at the tested temperatures. Additional studies should be conducted on deposition of tars at low temperatures during storage, condensation of heavy hydrogen carbons, quantification of tar deposited on the storage surface, and deterioration of the storage surface (especially when sulfur compounds exit in syngas).