Optimal Strategic Deployment and Novel Biomass Fly-ash Derived Solid Adsorbent Modelling for Carbon Capture Applications

Abstract

This thesis aims to advance the fight against global warming by developing modelling tools aimed to determine the optimal location of capture plants, and through the development of new process flowsheets that make use of biomass waste as sorbents for CO2 capture and utilization. The first approach explores different strategies of decarbonization through optimal deployment planning and development of alternative carbon capture technologies. Initially a new framework for national optimal deployment of strategic carbon capture implementation is presented. This framework considers external environmental and social considerations often missing from implementation frameworks, which will aid policy makers in more well-rounded deployment decisions. The Canadian case study utilizing the proposed optimal planning strategy shows that implementation of 58 post-combustion carbon capture (PCC) plants located in seven provinces (Alberta, British Columbia, New Brunswick, Nova Scotia, Ontario, Quebec, and Saskatchewan) would result in Canada meeting the national targets. Through a sensitivity analysis on these targets, it was determined that plant distribution is heavily dependent on provincial energy and CO2 transport prices. Additionally, if Alberta were to reduce their GHG emissions by 50% through alternative sustainable methods, only 35 PCC plants would be required to meet national targets. In the second approach, 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 is presented. 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 model results from pre-treated and non-pre-treated biomass fly-ash, with benchmark CO2 capture rates of 87% and 89.7%, respectively. Results display a maximum CO2 capture rate of 93.23%. Key insights show an increased CO2 flue gas composition requires a higher adsorbent mass and the most effective flue gas volume to adsorbent mass ratio exists between 3.7 – 4.1. Additionally, higher regeneration temperatures result in improved CO2 capture while pre-treatment of fly-ash does not impact the kinetics of regeneration. Energy analysis show that the pre-treated fly-ash adsorbent is more efficient than the non-pretreated adsorbent, and both could be an improvement over amine-based post-combustion carbon capture with the incorporation of heat integration. However, the cost and water consumption of the pre-treatment process were high compared to that of the industry standard. As such, this model was improved and further examined by incorporating additional wastewater treatment units to recycle used water back to the pre-treatment water washing step and elemental extraction as a waste management tactic for the water treatment waste stream. The enhanced system recycles 85% of the used water and the benchmark results show a 4.2% cost reduction compared to the original process. Additionally, results determine that the cost of resource consumption (CRC) can be reduced by 14.5 % compared to the existing benchmark system. The key insights show that the amount of DI water and acid have the largest impact on process cost and CRC and that both straw and grass show potential as a silicone source for Li4SiO4 synthesis. Furthermore, an analysis on further utilization of CO2 and waste streams through elemental extraction of iron (III) hydroxide and calcium carbonate extraction were considered using different flowsheet configurations. Results from these tests showed that selling captured CO2 and waste streams to cement production is a suitable and sustainable alternative. A cost analysis from this strategy resulted in a 1.35% decrease in process costs from the baseline results and a 1.61% decrease in the CRC from the benchmark results thus promoting a circular carbon economy.