Gasification of Inferior Coal with High Ash Content under CO₂ and O₂/H₂O Atmospheres

Abstract

The gasification reaction of Nantong inferior coal was investigated in a laboratory fixed-bed reactor under CO₂ and O₂/H₂O atmospheres. The effects of the bed temperature and inlet-gas concentration on the yields of CO, H₂, and CH₄ were studied. The effects of coal ash and particle size on the fixed-carbon conversion were also investigated, and kinetic analysis was conducted with a homogeneous model. The product-gas-heating value and fixed-carbon conversion increased when the temperature was increased from 950 °C to 1100 °C under CO₂ atmosphere. When the inlet-CO₂ concentration was increased from 50 to 100 vol.%, the low heating value of the product gas and carbon conversion ratio slightly increased. During the gasification of inferior coal under the O₂/H₂O atmosphere, the CO concentration increased rapidly with increasing temperature. The H₂ and CH₄ concentrations increased initially and then decreased. The maximum gas heating value of 7934 kJ/m³ was obtained under the O₂ concentration of 70 vol.% at a bed temperature of 1050 °C. The cold-gas efficiency increased with increasing temperature and became 40.6% and 86.4% at 1100 °C under the CO₂ and O₂/H₂O atmospheres, respectively. The gasification reaction of the Nantong inferior coal strongly depended on the content of inherent inorganic matter. The gasification rates for both the CO₂ and O₂/H₂O atmospheres were independent of the particle size. The activation energy for the CO₂ and O₂/H₂O gasification reactions were 137 and 81 kJ/mol, respectively. The gasification reactions of the Nantong coal, which was performed under two different atmospheres, were compared and the reaction activity of the gasification reaction under CO₂ atmosphere was found to be much lower than that under the O₂/H₂O atmosphere.

Keywords:

• Inferior coal
• Gasification
• CO₂ atmosphere
• O₂/H₂O atmosphere
• Low heating value
• Fixed-carbon conversion ratio

Additional information

Funding

The authors would like to thank the Natural Science Foundation of China with Project No. 51206200, the Fundamental Research Funds for the Central Universities with Project No. CDJZR12140031, and the Visiting Scholar Foundation of Key Laboratory of Low-grade Energy Utilization Technologies and Systems, MOE of China in Chongqing University (LLEUTS-201301) for the financial support.