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Combustion group

Research Group Activities

Group_phot0_2018_copyThe Research Group undertakes research in:

  • design of new processes, utilising solid biomass and fossil fuels for electricity production with efficient capture of CO2,
  • use of chemical looping for gas-phase, selective oxidation reactions,
  • physics of granular flows, and
  • sustainable processes and processing.

1)     New processes utilising solid biomass or fossil fuels for electricity production with efficient capture of CO2. 

The focus is primarily on fluidised bed reactors, since they are important in novel cycles using solid fuels for power generation, designed to capture and sequester the CO2. Fluidised combustors are very important in power generation using biomass fuels, since they give advantages over other combustors in (i) tolerance to changes in fuel, (ii) the catalysis of reactions or capture of pollutants by the bed material, (iii) high heat transfer, and (iv) economic operation at relatively small scales. A particular interest is Chemical Looping (CL). In basic CL, gaseous fuel is oxidised by a solid metal oxide (or oxygen carrier), MeO, in one reactor. The exit gas yields almost pure CO2 after the steam is condensed. The reduced metal oxide, Me, is transferred to an oxidation reactor and regenerated. Thus, the fuel is combusted, but the CO2 is separated from the nitrogen in air. CL with solid fuels is more difficult because fuel and carrier are not easy to separate during carrier regeneration. Ensuring durability of the MeO over many redox cycles is an important problem being studied by the Group. We also work on the use of iron and other oxides to produce clean hydrogen from biomass, uncontaminated with COx and suitable for fuel cells. Multi-institutional collaborations, elucidating the materials-science of looping-materials, are used to relate process performance to structure.

Gasifying solid fuels to CO and H2 allows the enhanced watergas-shift (WGS) process, using solid CaO to remove the carbon content as CaCO3, to produce hydrogen for fuel. Subsequent heating of CaCO3 releases the CO2 for sequestration. The absorption capacity of CaO from natural minerals falls markedly with number of forward and reverse steps, but we have discovered ways of reducing this fall. The Group has also created synthetic sorbents which decay in capacity much less than natural sorbents. Other research has examined (i) the kinetics of fuel devolatilisation, (ii) theory and experiment on mass transfer around combusting, or gasifying particles in fluidised beds of oxygen carrier, (iii) the reaction between SO2 and calcium-based sorbents and (iv) attrition and break-up of oxygen carriers in fluidised beds.

2)     Chemical looping for gas-phase, selective oxidation reactions. In a new departure for the CL area, we are examining (in collaboration with Johnson Matthey plc) whether structured particles, containing mixtures of catalyst and oxygen donor, can be used to effect selective oxidation reactions, e.g. the industrially-important reactions of oxidative dehydrogenation of alkanes to alkenes and the epoxidation of ethylene and propylene. The critical point is that the organic does not have to be mixed with low levels of air – the oxygen is provided in lattice form from the MeO. The significance is that success would enable these reactions to be run more safely, more intensively and with greater selectivity than is currently possible. Cambridge Enterprise has invested in a patent application for epoxidation (Chan et al. 2017) and proof of principle is currently being demonstrated with the target being to exceed selectivity and conversion seen in industrial reactors using the conventional process.

3)    Physics of granular flows. Processes in (1) depend on efficient gas-solid reactions and solids flow. A primary interest is fluidisation, investigated using innovative combinations of new (e.g. Magnetic Resonance Imaging, MRI) and existing (e.g. Particle Image Velocimetry, Electrical Capacitance Tomography) experimental techniques, underpinned by theoretical approaches (e.g. Discrete Element Modelling, DEM).Granular systems are visually opaque, making observations difficult inside three-dimensional (3D) systems. Accordingly, most previous experimental studies have been restricted to so-called two-dimensional (2D) fluidised beds, but the fluid dynamics are influenced by the walls and the findings cannot be confidently generalised to 3D beds. Until recently, only two experimental techniques have existed for the investigation of opaque, two-phase granular systems in 3D; X-radiography and electrical capacitance tomography (ECT), both of which present significant problems. In collaboration with Prof. Gladden, we have developed magnetic resonance (MR) imaging to observe fluidised beds internally. The significant advantage of MR over other techniques is that it can image the distribution of solids as well as their velocities and can image the gas. Research has shown the unique capability of ultra-fast (viz. acquisition times of 1-25 ms) MR measurements to give detailed, quantitative information on complex phenomena occurring in 3D gas-fluidised beds. As a result, a number of areas of long-standing controversy have finally been settled. For example, on whether gas issues from the holes in the distributor as a stream of bubbles or as a permanent jet. This is important, practically, because the distributor region can markedly affect overall performance in industrial units. For scale-up, we have conducted the first comparison of MRI with Electrical Capacitance Tomography, ECT (with Prof. L-S. Fan, Ohio State) on fast-fluidisation. We have also cross-validated MRI with X-ray imaging (Prof. P. Lettieri, UCL) and also with PEPT (Dr D. Parker, Birmingham U.). For fluidised beds, vibrating beds and other granular flow reactors, Discrete Element Modelling (DEM) has been used and involves coupling the equations of motion of each individual particle with the equations describing the fluid mechanics of the gas and solving the whole simultaneously for incremental steps in time, allowing for the mechanics of deformation of the particles as they collide. The purpose is to understand, e.g. the movement of reacting fuel particles, which is only possible with a realistic description of both gas and solid phases present. A very important facet is to validate the theoretical predictions with experimental results from MR and PIV, an aspect neglected by other modellers because of the inaccessibility of 3D systems to direct observation. One recent PhD student (see papers by Boyce et al., below) has used special MR techniques to track both gas and solids simultaneously – a major achievement.

4)      Sustainable processes and processing. We have undertaken reaction engineering studies of the Fischer-Tropsch (FT) synthesis and methanation using CO and CO2. The research is largely concerned with understanding the fundamental interactions between mass transfer and intrinsic chemical kinetics, particularly as liquid are formed in FT.

In a recent project, we have been examining solar-driven water splitting, focusing on Au/TiO2 systems, which have been previously reported to be active under visible light. The aim is to produce hydrogen. We have examined the efficiency of water splitting on disordered titanate nanotubes and titania surfaces activated with gold nanoparticles; of interest here is developing an understanding of how the combination of properties of the gold nanoparticles and nanotubes will affect the efficiency of water splitting under visible light. We have also experimented with structured nanotube systems and special perovskite materials and investigated how their properties can be altered by the structure and modification with other components. Our target is to construct proof of principle devices to demonstrate the feasibility of using both the disordered and ordered systems for photocatalytic water splitting.

The group has undertaken system-level, life-cycle studies of, e.g. proposed routes for converting biomass to fuel or products. A recent PhD project studied the opportunities for making the production of polyethylene terephthalate (PET, used in making bottles for drinks and in fibres) more sustainable by sourcing one or more of the raw materials from crop-derived materials.

Other research is focusing on the evaluation at both pilot scale and bench scale of continuous ion exchange chromatography to remove particular products from a process stream derived from a fermentation. Based on this, the collaborating company will be able to decide whether or not the technology will be suitable for an envisaged, large-scale process. Further research in this separations area has examined a novel solvent-extraction approach for isolating butanol, resulting in a patentable discovery (Hodgson & Dennis 2018).

We publish regularly in these fields, including attendance at major international conferences, and have significant links with researchers around the world.

Note to Applicants

  1. Applicants for a PhD will require a good, First-Class (or equivalent), 4-year degree in chemical engineering, engineering, chemistry or physics. Research in the group will often call on a good understanding of transport processes, mathematics, reaction engineering and thermodynamics, so candidates must be willing to develop proficiency in these areas.
  2. High standards of written and spoken English are required. Short-listed applicants will be interviewed.
  3. Funded vacancies for post-doctoral positions in the Group will be advertised on
  4. We do NOT offer undergraduate internships.

Publications in the period since 2014

Hodgson, P. & Dennis, J. S. (2018). Butanol recovery method and application. International Patent Application PCT/GB2018/000057 (Cambridge Enterprise). Filing date: 4/04/2018.

Chan, M. S., Marek, E., Scott, S. A. & Dennis J. S. (2017). Epoxidation of alkenes using a chemical looping method. Patent GB1713951.0, CE Reference: Mar-3508-17 (Filing date expected December 2018).

Harding, K. G., Dennis, J. S., & Harrison, S. T. L. (2018). Generic flowsheeting approach to generating first estimate material and energy balance data for Life Cycle Assessment (LCA) of Penicillin V production. Sustainable Production and Consumption, 15, 89-95. doi:10.1016/j.spc.2018.05.004

Schnellmann, M. A., Heuberger, C. F., Scott, S. A., Dennis, J. S., & Mac Dowell, N. (2018). Quantifying the role and value of chemical looping combustion in future electricity systems via a retrosynthetic approach. International Journal of Greenhouse Gas Control, 73, 1-15. doi:10.1016/j.ijggc.2018.03.016

Görke, R. H., Hu, W., Dunstan, M. T., Dennis, J. S., & Scott, S. A. (2018). Exploration of the material property space for chemical looping air separation applied to carbon capture and storage. Applied Energy, 212, 478-488. doi:10.1016/j.apenergy.2017.11.083

Schnellmann, M. A., Donat, F., Scott, S. A., Williams, G. & Dennis, J. S. (2018). The effect of different particle residence time distributions on the chemical looping process. Applied Energg, 216, 358-366. doi: 10.1016/j.apenergy.2018.02.046

Chan. M. S. C., Baldovi, H. G. & Dennis, J. S. (2018). Enhancing the capacity of oxygen carriers for selective oxidations through phase cooperation: bismuth oxide and ceria-zirconia.. Catalysis Science & Technology, 8, 887-897. doi: 10.1039/c7cy01992k.

Chan. M. S. C., Marek, E., Scott, S. A. & Dennis, J. S. (2018). Chemical looping epoxidation. J. Catalysis, 359, 1-7. doi: 10.1016/j.jcat.2017.12.030.

Hu, W., Marek, E., Donat, F., Dennis, J. S., & Scott, S. A. (2018). A thermogravimetric method for the measurement of CO/CO2 ratio at the surface of carbon during combustion. Proceedings of the Combustion Institute. doi:10.1016/j.proci.2018.05.040

Van Uytvanck, P. P., Haire, G., Marshall, P. J., & Dennis, J. S. (2017). Impact on the Polyester Value Chain of Using p-Xylene Derived from Biomass. ACS Sustainable Chemistry and Engineering, 5(5), 4119-4126. doi:10.1021/acssuschemeng.7b00105

Bhave, A., Taylor, R. H. S., Fennell, P., Livingston, W. R., Shah, N., Dowell, N. M., . . . Akroyd, J. (2017). Screening and techno-economic assessment of biomass-based power generation with CCS technologies to meet 2050 CO2 targets. Applied Energy, 190, 481-489. doi:10.1016/j.apenergy.2016.12.120

Li, P., Liu, W., Dennis, J. S., & Zeng, H. C. (2017). Synthetic Architecture of MgO/C Nanocomposite from Hierarchical-Structured Coordination Polymer toward Enhanced CO2 Capture.. ACS Appl Mater Interfaces, 9(11), 9592-9602. doi:10.1021/acsami.6b14960

Tagliaferri, C., Görke, R., Scott, S., Dennis, J., & Lettieri, P. (2018). Life cycle assessment of optimised chemical looping air separation systems for electricity production. Chemical Engineering Research and Design, 131, 686-698. doi:10.1016/j.cherd.2017.11.010

Hu, W., Donat, F., Scott, S. A., & Dennis, J. S. (2016). The interaction between CuO and Al2O3 and the reactivity of copper aluminates below 1000 °C and their implication on the use of the Cu-Al-O system for oxygen storage and production. RSC Advances, 6(114), 113016-113024. doi:10.1039/c6ra22712k

Dai, P., González, B., & Dennis, J. S. (2016). Using an experimentally-determined model of the evolution of pore structure for the calcination of cycled limestones. Chemical Engineering Journal, 304, 175-185. doi:10.1016/j.cej.2016.06.068

Boyce, C. M., Rice, N. P., Ozel, A., Davidson, J. F., Sederman, A. J., Gladden, L. F., Holland, D. J. (2016). Magnetic resonance characterization of coupled gas and particle dynamics in a bubbling fluidized bed. Physical Review Fluids, 1(7). doi:10.1103/PhysRevFluids.1.074201

Lim, J. Y., McGregor, J., Sederman, A. J., & Dennis, J. S. (2016). The role of the Boudouard and water–gas shift reactions in the methanation of CO or CO2 over Ni/γ-Al2O3 catalyst. Chemical Engineering Science, 152, 754-766. doi:10.1016/j.ces.2016.06.042

Schnellmann, M. A., Scott, S. A., Williams, G., & Dennis, J. S. (2016). Sensitivity of chemical-looping combustion to particle reaction kinetics. Chemical Engineering Science, 152, 21-25. doi:10.1016/j.ces.2016.05.028

Donat, F., Hu, W., Scott, S. A., & Dennis, J. S. (2016). Use of a Chemical-Looping Reaction to Determine the Residence Time Distribution of Solids in a Circulating Fluidized Bed. Energy Technology, 4(10), 1230-1236. doi:10.1002/ente.201600140

Hubble, R. A., Lim, J. Y., & Dennis, J. S. (2016). Kinetic studies of CO2 methanation over a Ni/γ-Al2O3 catalyst.. Faraday Discuss, 192, 529-544. doi:10.1039/c6fd00043f

Dunstan, M. T., Maugeri, S. A., Liu, W., Tucker, M. G., Taiwo, O. O., Gonzalez, B., . . . Grey, C. P. (2016). In situ studies of materials for high temperature CO2 capture and storage.. Faraday Discuss, 192, 217-240. doi:10.1039/c6fd00047a

Chan, M. S. C., Liu, W., Ismail, M., Yang, Y., Scott, S. A., & Dennis, J. S. (2016). Improving hydrogen yields, and hydrogen: Steam ratio in the chemical looping production of hydrogen using Ca2Fe2O5. Chemical Engineering Journal, 296, 406-411. doi:10.1016/j.cej.2016.03.132

Boyce, C. M., Rice, N. P., Davidson, J. F., Sederman, A. J., Gladden, L.F., Sundaresan, S., Dennis, J. S., & Holland, D. J. (2016). Magnetic resonance characterisation of coupled gas and particle dynamics in a bubbling fluidised bed. Physical Review Fluids, Acceptance LQ15636F, 3rd October.

Boyce, C. M., Rice, N. P., Davidson, J. F., Sederman, A. J., Dennis, J. S., & Holland, D. J. (2016). Magnetic resonance imaging of gas dynamics in the freeboard of fixed beds and bubbling fluidized beds. Chemical Engineering Science, 147, 13-20. doi:10.1016/j.ces.2016.03.005

Lim, J. Y., McGregor, J., Sederman, A. J., & Dennis, J. S. (2016). Kinetic studies of the methanation of CO over a Ni/γ-Al2O3 catalyst using a batch reactor. Chemical Engineering Science, 146, 316-336. doi:10.1016/j.ces.2016.02.001

Dai, P., Dennis, J. S., & Scott, S. A. (2016). Using an experimentally-determined model of the evolution of pore structure for the gasification of chars by CO2. Fuel, 171, 29-43. doi:10.1016/j.fuel.2015.12.041

Yang Lim, J., McGregor, J., Sederman, A. J., & Dennis, J. S. (2016). Kinetic studies of CO2 methanation over a Ni/γ-Al2O3 catalyst using a batch reactor. Chemical Engineering Science, 141, 28-45. doi:10.1016/j.ces.2015.10.026

Boyce, C. M., Rice, N. P., Sederman, A. J., Dennis, J. S., & Holland, D. J. (2016). 11-interval PFG pulse sequence for improved measurement of fast velocities of fluids with high diffusivity in systems with short T2(∗).. J Magn Reson, 265, 67-76. doi:10.1016/j.jmr.2016.01.023

González, B., Liu, W., Sultan, D. S., & Dennis, J. S. (2016). The effect of steam on a synthetic Ca-based sorbent for carbon capture. Chemical Engineering Journal, 285, 378-383. doi:10.1016/j.cej.2015.09.107

Liu, W., González, B., Dunstan, M. T., Sultan, D. S., Pavan, A., Ling, C. D., Dennis, J. S. (2016). Structural evolution in synthetic, Ca-based sorbents for carbon capture. Chemical Engineering Science, 139, 15-26. doi:10.1016/j.ces.2015.09.016

Hu, W., Donat, F., Scott, S. A., & Dennis, J. S. (2016). Kinetics of oxygen uncoupling of a copper based oxygen carrier. Applied Energy, 161, 92-100. doi:10.1016/j.apenergy.2015.10.006

Boyce, C. M., Holland, D. J., Scott, S. A., & Dennis, J. S. (2015). Limitations on Fluid Grid Sizing for Using Volume-Averaged Fluid Equations in Discrete Element Models of Fluidized Beds. Industrial and Engineering Chemistry Research, 54(43), 10684-10697. doi:10.1021/acs.iecr.5b03186

Donat, F., Hu, W., Scott, S. A., & Dennis, J. S. (2015). Characteristics of Copper-based Oxygen Carriers Supported on Calcium Aluminates for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU). Industrial and Engineering Chemistry Research, 54(26), 6713-6723. doi:10.1021/acs.iecr.5b01172

Chandrasekera, T. C., Li, Y., Moody, D., Schnellmann, M. A., Dennis, J. S., & Holland, D. J. (2015). Measurement of bubble sizes in fluidised beds using electrical capacitance tomography. Chemical Engineering Science, 126, 679-687. doi:10.1016/j.ces.2015.01.011

Saucedo, M. A., Butel, M., Scott, S. A., Collings, N., & Dennis, J. S. (2015). Significance of gasification during oxy-fuel combustion of a lignite char in a fluidised bed using a fast UEGO sensor. Fuel, 144, 423-438. doi:10.1016/j.fuel.2014.10.029

Pore, M., Ong, G. H., Boyce, C. M., Materazzi, M., Gargiuli, J., Leadbeater, T., Parker, D. J. (2015). A comparison of magnetic resonance, X-ray and positron emission particle tracking measurements of a single jet of gas entering a bed of particles. Chemical Engineering Science, 122, 210-218. doi:10.1016/j.ces.2014.09.029

Saucedo, M. A., Dennis, J. S., & Scott, S. A. (2015). Modelling rates of gasification of a char particle in chemical looping combustion. In Proceedings of the Combustion Institute Vol. 35 (pp. 2785-2792). doi:10.1016/j.proci.2014.-07.005

Azadi, P., Brownbridge, G., Kemp, I., Mosbach, S., Dennis, J. S., & Kraft, M. (2015). Microkinetic modeling of the Fischer-Tropsch synthesis over cobalt catalysts. ChemCatChem, 7(1), 137-143. doi:10.1002/cctc.201402662

Lu, X., Boyce, C. M., Scott, S. A., Dennis, J. S., & Holland, D. J. (2015). Investigation of two-fluid models of fluidisation using magnetic resonance and discrete element simulations. In Procedia Engineering Vol. 102 (pp. 1436-1445). doi:10.1016/j.proeng.2015.01.277

Liu, W., Ismail, M., Dunstan, M. T., Hu, W., Zhang, Z., Fennell, P. S., Dennis, J. S. (2015). Inhibiting the interaction between FeO and Al2O3 during chemical looping production of hydrogen. RSC Advances, 5(3), 1759-1771. doi:10.1039/c4ra11891j

Liu, W., Lim, J. Y., Saucedo, M. A., Hayhurst, A. N., Scott, S. A., & Dennis, J. S. (2014). Kinetics of the reduction of wüstite by hydrogen and carbon monoxide for the chemical looping production of hydrogen. Chemical Engineering Science, 120, 149-166. doi:10.1016/j.ces.2014.08.010

Bajželj, B., Richards, K. S., Allwood, J. M., Smith, P., Dennis, J. S., Curmi, E., & Gilligan, C. A. (2014). Importance of food-demand management for climate mitigation. Nature Climate Change, 4(10), 924-929. doi:10.1038/nclimate2353

Yang, Y., Dennis, J. S., Saeys, M., & Wang, Y. (2014). Catalytic Materials And Catalysis For Low Carbon Technology Preface. CATALYSIS TODAY, 233, 1. doi:10.1016/j.cattod.2014.05.001

Lea-Smith, D. J., Bombelli, P., Dennis, J. S., Scott, S. A., Smith, A. G., & Howe, C. J. (2014). Phycobilisome-Deficient Strains of Synechocystis sp. PCC 6803 Have Reduced Size and Require Carbon-Limiting Conditions to Exhibit Enhanced Productivity.. Plant Physiol, 165(2), 705-714. doi:10.1104/pp.114.237206

Boyce, C. M., Davidson, J. F., Holland, D. J., Scott, S. A., & Dennis, J. S. (2014). The origin of pressure oscillations in slugging fluidized beds: Comparison of experimental results from magnetic resonance imaging with a discrete element model. Chemical Engineering Science, 116, 611-622. doi:10.1016/j.ces.2014.05.041

Boyce, C. M., Holland, D. J., Scott, S. A., & Dennis, J. S. (2014). Novel fluid grid and voidage calculation techniques for a discrete element model of a 3D cylindrical fluidized bed. Computers and Chemical Engineering, 65, 18-27. doi:10.1016/j.compchemeng.2014.02.019

Saucedo, M. A., Dennis, J. S., & Scott, S. A. (2015). Modelling rates of gasification of a char particle in chemical looping combustion. Proceedings of the Combustion Institute, 35(3), 2785-2792. doi:10.1016/j.proci.2014.07.005

Gladden, L. F., Sederman, A. J., & Dennis, J. S. (2014). Magnetic resonance imaging of single- and two-phase flows. CFB-11: Proceedings of the 11th International Conference on Fluidized Bed Technology, 47-53.

Van Uytvanck, P. P., Hallmark, B., Haire, G., Marshall, P. J., & Dennis, J. S. (2014). Impact of biomass on industry: Using ethylene derived from bioethanol within the polyester value chain. ACS Sustainable Chemistry and Engineering, 2(5), 1098-1105. doi:10.1021/sc5000804

Saucedo, M. A., Lim, J. Y., Dennis, J. S., & Scott, S. A. (2014). CO2-gasification of a lignite coal in the presence of an iron-based oxygen carrier for chemical-looping combustion. Fuel, 127, 186-201. doi:10.1016/j.fuel.2013.07.045

Pott, R. W., Howe, C. J., & Dennis, J. S. (2014). The purification of crude glycerol derived from biodiesel manufacture and its use as a substrate by Rhodopseudomonas palustris to produce hydrogen.. Bioresour Technol, 152, 464-470. doi:10.1016/j.biortech.2013.10.094