Thermodynamic assessment and techno-economic analysis of a liquid indium-based chemical looping system for biomass gasification

A detailed thermochemical analysis is carried out to assess the energetic performance of a proposed process based on liquid metal slurry in a chemical looping gasification process. The system is designed to produce synthetic gas and generate electricity from low-grade (waste) solid carbon black collected from a thermal plasma plant. Indium oxide-indium slurry mixture was used as an oxygen carrier. The thermodynamic models showed that oxygen availability in the fuel reactor is the determining parameter that controls the operating mode of the system. The molar ratio of liquid metal to feedstock (LMO/C) and the steam to feedstock (S/C) are identified the key factors that regulate the level of exergy partitioned in the gas products. Generating steam by heat-recovery from the vitiated air (exhausted from the air reactor), is a proof that the process is partially self-sustained – capable of generating electricity to drive the pumps and the air compressors in the process. At LMO/C = 0.1 and S/C = 1.5, the largest exergy is partitioned in the synthetic gas and a syngas quality (molar ratio of H(2): CO) of ~1.55 is achieved. The highest syngas quality was achievable, however, at the cost of unreacted steam, which increased the exergy destruction of the plant. The peak performance of the system is achieved when the (fuel and air) reactors operated at near-isothermal conditions. At these conditions, the exergy destruction between reactors is minimised and the power production in the power block is maximised. Based on indicative available price indexes, a techno-economic analysis evaluated the economic viability and the levelised cost of energy for a different price for various scenarios. It showed that the proposed system offers a competitive LCOE against several existing energy and hydrogen production systems.