Biomass fly-ash derived Li4SiO4 solid for pilot-scale CO2 capture, Part I: Modelling for a waste to capture CO2 process

Abstract

This work presents a new modelled system of a biomass-based lithium orthosilicate solid adsorbent derived from industrial biomass fly-ash used to capture CO₂ from power plant flue gas emissions. The model includes pre-treatment of biomass fly-ash, the synthesis of adsorbent, which utilizes fly-ash as the silicone source and a laboratory produced lithium source, the adsorption of CO₂ from flue gas, and regeneration of adsorbent. The study compares the results from pre-treated and non-pre-treated biomass fly-ash, with benchmark CO₂ capture rates of 87 % and 89.7 %, respectively and a maximum CO₂ capture rate of 93.23 %. Key insights from the scenarios considered in this work show that an increased CO₂ flue gas composition requires higher adsorbent mass and the most effective flue gas volume to adsorbent mass ratio between 3.7–4.1; additionally, higher regeneration temperatures result in improved CO₂ capture while pre-treatment of fly-ash does not impact regeneration kinetics. Energy analysis show that the pre-treated fly-ash adsorbent is more efficient than the non-pretreated adsorbent but is not superior to amine-based post-combustion carbon capture. If effective heat integration were to be incorporated for the pre-treated and non-pre-treated adsorption processes, energy consumption could be reduced by 54 % and 85 % compared to amine-based capture, respectively. Cost analysis indicated that by incorporating a recycle stream for pre-treatment wastewater and altering the acid to solid ratio during pre-treatment acid wash, process costs may be reduced over 20 % making this a feasible alternative carbon capture process.