We’re pleased to present a blog output from one of our 2018 Scientific Council Collaboration Fund award winners, Prof Hao Liu, University of Nottingham, and Prof Steven Milne, University of Leeds, on their research project ‘Evaluation of additives to prevent/alleviate sintering during chemical looping combustion of biomass’:
According to the World Energy Outlook 2020 of the International Energy Agency, reaching net zero carbon emissions globally by 2050 demands accelerated implementation of a suite of low carbon energy solutions in the next decade and beyond. Carbon Capture and Storage (CCS) is an integral component of these solutions.
Chemical Looping Combustion (CLC) is considered as a very promising CCS technology for power plants and industrial combustion processes. The CLC process involves the use of a solid oxygen carrier (OC), which acts as the bed material and transfers oxygen from air to the fuel avoiding the direct contact between them and thus reducing the energy penalty associated to CO2 capture. Research on biomass CLC has been on the increase in recent years due to its potential to achieve negative CO2 emissions. However, the use of biomass in a CLC process introduces new challenges related to biomass ash which usually contains a high level of alkali and alkaline metals that can cause operational problems such as bed agglomeration in CLC reactors. Various countermeasures to bed agglomeration including additives to the bed material have been investigated with conventional biomass fluidised bed combustion processes where silica sand is usually the bed material. However, no one has investigated the agglomeration issues and countermeasures in biomass CLC reactors where the bed materials are largely oxygen carriers (OCs) instead of silica sand.
The UKCCSRC Scientific Council Collaboration Fund was awarded to Professor Hao Liu, University of Nottingham, and Professor Steve Milne, University of Leeds, to investigate the agglomeration phenomena of OC particles mixed with biomass ash and to evaluate the anti-agglomeration ability of additives with biomass CLC processes using different OC materials.
The results of the research have led to an improved understanding on the agglomeration behaviours of the CLC bed materials which are composed of OC particles and biomass ash, and new knowledge on the effectiveness of the selected additives in reducing agglomeration in biomass CLC processes. The research has generated a tremendous amount of data on the characterisation of agglomerates formed by the mixtures of OC particles and biomass ash heated at CLC process temperatures, with and without the addition of anti-agglomeration additives. Other researchers can use the data to validate their modelling on the phase behaviours of CLC bed materials. In the long term, the outcomes of this project and the modelling projects conducted by other researchers can lead to solutions for the operational issues of biomass CLC plants, promoting the commercial deployment of CLC technology in power generation and other industries and consequently benefitting the environment by providing net-neutral, or even negative CO2 emissions.
Despite being severely disrupted by the Covid-19 pandemic and several unavoidable non-cost extensions to the completion date, the project achieved all of the proposed research objectives and measurable outputs. A technical paper has been planned to report the research results with a reputable journal in the near future.