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.