In-situ monitoring of agglomeration and defluidisation in a biomass FB combustor (Scientific Council Collaboration Fund)


UKCCSRC Scientific Council Collaboration Award winners, Hao Liu (University of Nottingham) and Gang Lu (University of Kent), have completed the visualisation and characterisation of agglomeration and defluidisation in a biomass FB combustor.

Given the UK 2050 targets, and the significant roles that bioenergy and CCS are expected to make, it is vital that the UK quickly develops its bioenergy technologies with CCS (BECCS). In fluidised bed boilers burning biomass, whether under conventional air combustion or oxy-combustion conditions, agglomeration and defluidisation is a particular concern. Biomass fuels often contain high levels of alkali and alkaline metals (AAMs) which can interact with bed materials to form low melting point potassium-rich silicates, that can adhere to the bed material particles.

Under the UKCCSRC Scientific Council Collaboration Award, research teams at the University of Nottingham and the University of Kent conducted an experimental study on a 20kWth biomass-fired BFB (bubbling fluidised bed) combustor to investigate the fluid dynamic characteristics of biomass fuels and bed materials, as well as the formation process of agglomerates through digital imaging and signal/image processing. The Kent’s flame imaging system was modified and installed on the Nottingham’s BFB combustor for visualising burning biomass particles on the bed surface. Rig operation data, including pressure drops and furnace temperature, were collected under a range of operation conditions.

Kent’s flame imaging system installed on Nottingham’s fluidised bed biomass combustion test facility

The results obtained suggested that there is a strong correlation between the defluidisation/agglomeration and the pressure drop across the combustion bed zone. In particular, the rate of the pressure drop change can potentially be a better indicator for severe agglomeration/defluidisation in the combustor. It has also been proven that digital imaging is a promising technique for visualising the combustion behaviours of biomass particles and bed materials inside the BFB combustor. The findings of the research have led to an improved understanding of the fundamental aspects of biomass combustion in BFB combustors, and thus the energy conversion, agglomeration formation and defluidisation process.

Despite being severely disrupted by the COVID-19 pandemic and several unavoidable non-cost extensions to the completion date, the results obtained indicate clearly that the project teams have achieved the proposed research objectives and measurable outputs. More comprehensive data processing is in progress in order to quantify the combustion behaviours of different biomass materials (e.g. colour, and spectral intensities of biomass flames) under different operating conditions. A technical paper has been planned to report the research results with a reputable journal such as Fuel, Biomass and Bioenergy in the near future.


Prof Hao Liu, Faculty of Engineering, University of Nottingham, email:

Dr Gang Lu, School of Engineering, University of Kent, email:

Chenggong Sun, University of Nottingham, was awarded funding in our Scientific Council Collaboration Fund 2019 to look at “CO2 utilisation for photo-catalytic mass production of glycerol carbonate from crude glycerol as a versatile chemical building block in chemical industry”.

Glycerol, also known as glycerine, is a major primary byproduct of biofuel production, with the rapidly expanding global biodiesel production alone generating over five million tons per annum at present. As a result, there has been a great surge of interest in using glycerol as an abundant renewable feedstock to produce more advanced biofuels and biochemicals, whilst improving the economic performance and resource efficiency of biofuel production. Here, we describe, for the first time, the selective catalytic conversion of glycerol to 2,5-hexanedione (2,5-HD) and other more advanced C6-C12 cycloalkanes and/or polyketones by making use of water hydrogen under relatively mild conditions. 2,5-HD is recognised as being a vital gateway chemical for the synthesis of pesticides, resin materials and high-density aviation biofuels.

A type of copper-carbon nanocomposite catalyst was prepared on a small lab scale by using a metal–organic framework (MOF) precursor through an integrated pyrolysis and activation methodology. The catalyst was found to exhibit rarely seen catalytic activity for the desirable selective conversion of glycerol to 2,5-HD and other more advanced C8-C12 cyclo-alkanes/oxygenates, and no externally supplied hydrogen was needed as the hydrogen required can be generated in situ from simultaneous aqueous glycerol reforming reactions, which were also catalysed by this catalyst. The selectivity could reach 43.4% for the formation of 2,5-hexanedione and over 70% for total C8-C12 cyclo-alkanes/poly-oxygenates under the experimental conditions examined. It is believed that the catalytic conversion can potentially be tuned to facilitate the production of either 2,5-HD or more advanced polycyclic alkanes and/or ketones as the major products. Characterizations show that the remarkable catalytic capability of the MOF-derived catalyst arose not only from the highly dispersion of copper in the carbon substrate but also from the unique chemical states of the distributed copper species, a novel physicochemical feature that cannot be achieved with conventional catalyst preparation methodologies. Although the research is still at its preliminary stage, the results augur very well for the production of high-density aviation fuels from glycerol refinery.

As a part of this Collaboration award, we were delighted to collaborate with Prof Xianfeng Fan at the University of Edinburgh.

Research paper – Directed glycerol conversion to 2,5-hexanedione and more advanced poly-oxygenates as platform chemicals and high energy–density fuel additives