Co-production of high strength extruded activated carbon and hydrogen-rich syngas via K₂CO₃ catalytic incomplete gasification of coal

Coal gasification technology is an important technology for clean and efficient utilization of coal. However, the carbon conversion of coal gasification process cannot reach 100% and thus a large amount of waste slag containing carbon residue is produced. The high content of porous carbon residue in the fine slag is difficult to extract, which results in the difficult utilization of large accumulation of fine slag. In this paper, starting from the source of fine slag formation, the low ash cylindrical coal particles were incompletely gasified over K₂CO₃ catalyst(the gasification was terminated when the carbon conversion rate reached about 70%-80%)to produce hydrogen-rich syngas and K-doped activated carbon (AC-Kx)with high-performance. The components of gasification gas and the CO₂ adsorption performance of AC-Kx as well as the role of residual K in AC-Kx were also investigated. The results show that at the gasification final temperature of 950℃, the H₂/CO ratio and the hydrogen-carbon ratio f could reach 2.20-6.29 and 1.37-2.32, respectively, in the gas product from K₂CO₃ catalytic incomplete steam gasification. Compared with the sample without potassium doping, the f of gas products from the K-doped samples increased significantly. The volume fraction of CO and CO₂ in the gas produced in the later stage of gasification was high, indicating that the incomplete gasification and timely termination of gasification reaction could increase the hydrogen-carbon ratio of syngas and reduce the carbon emission of coal gasification process. When the addition amount of K₂CO₃ was up to the 5% of coal mass, the BET specific surface area, methylene blue adsorption value and the abrasive resistance of resultant AC-K5 reached 1 051 m²/g, 215 mg/g and 95.8%, respectively. At 200℃, the CO₂ adsorption capacity of AC-K5 was 1.63 times higher than that of AC-K0. It can be concluded that the incomplete gasification of coal particles catalyzed by K₂CO₃ can simultaneously produce hydrogen-rich syngas and the activated carbon with high abrasive resistance for CO₂ capture, improving the economy of coal catalytic gasification.