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Open Access Publications from the University of California

Development of a Sorption Enhanced Steam Hydrogasification Process for In-situ Carbon Dioxide (CO2) Removal and Enhanced Synthetic Fuel Production

  • Author(s): Liu, Zhongzhe
  • Advisor(s): Norbeck, Joseph M
  • et al.

Energy security and climate change are two common challenges in the coming decades. The demand for energy is increasing. The CO2 in the atmosphere has increased to almost 400ppm, and it is mainly from energy usage. How to deal with energy-related CO2 emissions with the increasing demand for energy is becoming more crucial.

Carbon capture and sequestration during energy production is an efficient way to guarantee enough energy supply with a smaller carbon footprint. One unique technique is using in-situ CO2 capture technology, which uses a sorbent to capture CO2 directly in the reactor. CO2 is removed quickly as it forms by the sorbent, which can change the equilibrium to promote more energetic production. This technology has great potential to lower CO2 emissions and get higher energy production simultaneously.

A new concept of sorption enhanced steam hydrogasification reaction (SE-SHR) is the topic of this thesis. It combines sorption enhanced principles with the steam hydrogasification reaction (SHR). It was found that the addition of sorbent enhanced the CO2 removal and increased the production of H2 and CH4. Particularly, the amount of H2 was increased dramatically. It was found that the increase in H2 was enough to recycle when the CaO/C molar ratio was over 0.29. The sorption enhanced performance was also evaluated by varying other parameters including H2/C and Steam/C molar ratio, gasification temperature and sorbent particle size.

A study of the kinetics of the system showed that higher gasification temperature favored faster formation rates of CO2, CO and CH4 during both SHR and SE-SHR. The formation rates of CO2 and CO at 650°C, 700°C and 750°C were much lower during SE-SHR.

Several configurations based on SE-SHR for the production of Fischer Tropsch fuel and synthetic natural gas were developed and evaluated. The optimum gasification condition (H2/C-Steam/C) for Fischer Tropsch fuel production using SE-SHR based process was found to be 1.59-2.78. This process had lower total CO2 emissions with higher fuel yield compared to the optimum SHR based process. SE-SHR-Methanation based process for SNG production with the optimum gasification condition (H2/C-Steam/C) of 1.08-2.22 had the highest CH4% and near zero CO2% in the final gas product.

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