The novel energy generation technology for paper mills based on staged coal gasification and fuel cell coupling

Currently, large-scale paper mills typically rely on coal-fired self-owned power plants to meet their combined heat and power demands. However, the inefficient mode of coal utilization and the mismatch between energy quality and process requirements in papermaking lines are major barriers to improving overall energy efficiency. This necessitates the development of novel coal utilization strategies that enable energy conservation and carbon reduction without compromising production capacity. Staged coal gasification has been proven to be a clean coal utilization technology suitable for power generation and possesses further potential for improving energy efficiency. In this context, the study proposes a novel power generation technology for paper mills, based on the coupling of staged coal gasification and fuel cell. By using CO₂ as the gasifying agent, the staged gasification process alters the elemental flow pathways compared to conventional gasification, promoting the orderly transformation of carbon and hydrogen components. Carbon-neutral biomass is introduced as an external combustion heat source for staged gasification, enhancing the system's potential to achieve negative carbon emissions. Fuel cells are employed as a parallel replacement for steam turbines, serving as the core power generation unit of the paper mill, thereby enabling the stepwise release of the chemical energy of syngas. The entire system is simulated using Aspen Plus software, with key parameters and modules validated against experimental and literature data. The system's power generation potential and overall electricity-heat efficiency are systematically analyzed. Results indicate that the synergistic effect of staged coal gasification and fuel cells significantly improves energy performance and emission reduction characteristics. When the fuel cell operates at 400 °C, with a water to carbon ratio of 2 and a hydrogen separation ratio of 0.545, the net energy efficiency of the novel system reaches a maximum of 81.21%. Compared to conventional systems, the new system achieves improvements of 24.65% in net power generation, 13.66% in total heat production, and 38.31% in net energy generation. The proposed system captures CO₂ at a rate of 486.5 mol/s, offsetting the CO₂ from coal (457.6 mol/s) and achieving negative carbon emissions. This novel power generation system based on staged coal gasification and fuel cell coupling can substantially enhance the capacity efficiency of self-owned power plants in paper mills while realizing negative-carbon coal utilization.