Integration of calcium looping technology in combined cycle power plants using co-gasification of torrefied biomass and coal blends

To comprehensively understand the impact of calcium looping (CaL) technology on a co-gasification of torrefied biomass and coal power plant, two kinds of proposed configurations (pre- and post-CaL), including a co-gasification system, a CaL system, and a combined heat and power system, are studied and compared with each other in the present work. In the CaL process, the kinetic modeling of the carbonation reaction and CaO sorption-enhanced water gas shift (SE-WGS) reaction are developed in a fast fluidized bed reactor (carbonator) to predict the performance of hydrogen production and CO₂ capture. The influences of torrefied biomass blending ratios (BRs) and CaO to fuel mass flow rate ratios (CaO/F) on various performance indicators such as hydrogen enhancement factor, hydrogen thermal efficiency (HTE), CO₂ capture efficiency, specific CO₂ emissions, and overall system efficiency are evaluated. A comparison of pre- and post-CaL schemes reveals that the SE-WGS reaction has a markedly profound effect on the former, causing the hydrogen production and HTE to be higher than those in the latter, whereas the latter is much more conducive to CO₂ capture and specific CO₂ emissions. Under optimal operating conditions (BR = 40 wt%, CaO/F = 3.5), the values of CO₂ capture efficiency and overall system efficiency of both schemes are higher than 90% and 50%, respectively. Overall, the pre-CaL case is suitable to design as a highly efficient co-generation of hydrogen production and electricity plant with low CO₂ emissions, whereas the post-CaL case is recommended for a co-gasification power plant with nearly zero CO₂ emissions.