(67d) Coal Power Generation with High Efficiency and near-Zero Emissions

Recent advances in coal gasification technologies have opened the door for new, environmentally friendly electricity generation processes. For example, integrated gasification combined cycle (IGCC) processes typically achieve higher electrical efficiencies than traditional pulverized coal power plants. Using absorption techniques, IGCC processes can be enabled to achieve 90% carbon capture at the expense of a significant energy penalty [1]. Alternative techniques such as oxycombustion [2] and chemical looping [3] can be employed to perform combustion using an oxygen source undiluted by nitrogen. This permits up to 100% post-combustion capture of CO₂ without the need for an absorption-based process, but at a significantly higher energy penalty.

A new design paradigm is required to achieve both high efficiency and 100% CO₂ capture. In this paper, a novel electricity generation process using integrated gasification and solid oxide fuel cells is presented. By replacing the combustion step with SOFC stacks, electricity can be generated without the need for high purity oxygen while preventing nitrogen from entering the fuel exhaust. This enables 100% downstream capture of CO₂ and avoids the need for energy-intensive pressure-swing absorption?essentially eliminating the energy penalty for CO₂ capture. As a result, the thermal efficiency of the SOFC-based process is higher than IGCC processes by about 10 absolute percentage points (%HHV).

In addition to 100% CO₂ capture, the process has zero atmospheric emissions. Any H₂S, SO_X, unreacted hydrocarbons, or any other pollutants are sequestered along with the CO₂. For a 750 MW power plant, this prevents up to 400 tonne/yr of SO₂ emissions. Fresh water consumption is 25% lower than IGCC and 50% lower than traditional pulverized coal. If waterless cooling systems are employed (such as air-cooling), a surplus of high-purity water is generated by the process, rather than consumed. Thus, the fuel-cell enabled process has significant environmental and efficiency advantages over the current alternatives.

References

[1] Woods MC, Capicotto PJ, Haslbeck JL, Kuehn NJ, Matuszewski M, Pinkerton LL, Rutkowski MD, Schoff RL, Vaysman V. Cost and Performance Baseline for Fossil Energy Plants. Volume 1: Bituminous Coal and Natural Gas to Electricity Final Report. DOE/NETL‐2007/1281, Revision 1, August 2007.

[2] Duan L, Lin R, Deng S, Jin H, Cai R. A novel IGCC system with steam injected H₂/O₂ cycle and CO₂ recovery. Energy Convers Manage 45:797‐809 (2004).

[3] Li F, Fan L-S. Clean coal conversion processes ? progress and challenges. Eng Environ Sci 1:248-267 (2008).