Novel calcium-looping-based biomass-integrated gasification combined cycle: thermodynamic modeling and experimental study

The current work focuses on the development of a novel calcium-looping-based biomass-integrated gasification combined cycle (CL-BIGCC) process. The process is expected to improve the energy density of synthesis gas by capturing CO₂ in a carbonator. Also, at the same time, the carbonator is expected to act as an ex situ tar removal unit, where tar cracking is expected to occur via catalytic reactions with CaO. The current work evaluates the feasibility of the proposed CL-BIGCC concept via thermodynamic analysis using Aspen Plus. Moreover, the tar cracking ability of CaO is demonstrated using thermogravimetric analyzer coupled to Fourier transform infrared spectrometer (TGA-FTIR) experiments. As part of the thermodynamic analysis, sensitivity analyses of the key process parameters, such as the calcium/biomass (Ca/B) ratio, steam/biomass (S/B) ratio, carbonator temperature, and calciner temperature, and their effects on net thermal-to-electricity efficiency have been studied in detail. The optimal values of key process parameters, such as a compression ratio of 5.1, an air/fuel mass ratio of 15, a Ca/B ratio of 0.53, a S/B ratio of 0.17, and carbonator and calciner temperatures of 650 and 800 °C, respectively, have been obtained. Furthermore, the CL-BIGCC process simulated in the current work was found to have a net thermal-to-electricity efficiency of ∼25% based on the above optimal parameters, which is the highest among other conventional steam-based BIGCC processes. The biomass gasification (i.e., partial oxidation) experiments in a TGA-FTIR with a CaO/biomass ratio of 1:1 at different temperatures showed that CaO effectively catalyzed tar-cracking reactions.