Imperial College London

DrTomHills

Faculty of EngineeringDepartment of Chemical Engineering

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Summary

 

Publications

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20 results found

Vallejo L, Mazur C, Strapasson A, Cockerill T, Gambhir A, Hills T, Jennings M, Jones O, Kalas N, Keirstead J, Khor C, Napp T, Tong D, Woods J, Shah Net al., 2021, Halving Global CO2 Emissions by 2050: Technologies and Costs, International Energy Journal, Vol: 21, Pages: 147-158, ISSN: 1513-718X

This study provides a whole-systems simulation on how to halve global CO2 emissions by 2050, compared to 2010, with an emphasis on technologies and costs, in order to avoid a dangerous increase in the global mean surface temperature by end the of this century. There still remains uncertainty as to how much a low-carbon energy system costs compared to a high-carbon system. Integrated assessment models (IAMs) show a large range of costs of mitigation towards the 2°C target, with up to an order of magnitude difference between the highest and lowest cost, depending on a number of factors including model structure, technology availability and costs, and the degree of feedback with the wider macro-economy. A simpler analysis potentially serves to highlight where costs fall and to what degree. Here we show that the additional cost of a low-carbon energy system is less than 1% of global GDP more than a system resulting from low mitigation effort. The proposed approach aligns with some previous IAMs and other projections discussed in the paper, whilst also providing a clearer and more detailed view of the world. Achieving this system by 2050, with CO2 emissions of about 15GtCO2, depends heavily on decarbonisation of the electricity sector to around 100gCO2/kWh, as well as on maximising energy efficiency potential across all sectors. This scenario would require a major mitigation effort in all the assessed world regions. However, in order to keep the global mean surface temperature increase below 1.5°C, it would be necessary to achieve net-zero emission by 2050, requiring a much further mitigation effort.

Journal article

Lisbona P, Bailera M, Hills T, Sceats M, Diez L, Romeo LMet al., 2020, Energy consumption minimization for a solar lime calciner operating in a concentrated solar power plant for thermal energy storage, RENEWABLE ENERGY, Vol: 156, Pages: 1019-1027, ISSN: 0960-1481

Journal article

Hills TP, Sceats MG, Fennell PS, 2020, Chapter 10: Applications of CCS in the cement industry, RSC Energy and Environment Series, Pages: 315-352, ISBN: 9781788014700

Cement manufacture is responsible for around 7% of global anthropogenic CO2 emissions. The process is unique in that around two-Thirds of the direct CO2 emissions are unavoidable as they come from the process chemistry rather than from fuel combustion. This makes reducing them particularly difficult, and carbon capture and storage is currently the only option that can reduce emissions by the extent required to allow cement manufacture to continue beyond the transition to low CO2-emission economies. Post-combustion capture options, which are similar to those described in Chapter 4, are available. Equally, oxy-fuel combustion is possible. Pre-combustion capture can only deal with one-Third of emissions from combustion, and so is generally not considered. Other cement-specific options exist, such as direct separation, and the synergies between calcium looping and cement manufacture are noteworthy. High CO2 intensity coupled with the relatively low price of cement means that CCS is expensive per unit of cement manufactured. The lack of large-scale capture facilities means that the costs are rather uncertain, although several estimates are given in this chapter. A summary of existing pilot plants is provided, the challenges of rolling out carbon capture in the cement sector are discussed, and a way forward is suggested.

Book chapter

Lisbona P, Bailera M, Hills T, Sceats M, Díez LI, Romeo LMet al., 2019, Energy consumption minimization for a solar lime calciner operating in a concentrated solar power plant for thermal energy storage, Pages: 4091-4103

Calcium-looping systems can be coupled with concentrated solar power plants as an alternative for thermal energy storage. This storage concept is based in the high temperature reversible calcination-carbonation reactions, in which limestone and lime are alternatively converted. These reactions produce or consume a specific amount of CO2 and consume or release important quantities of thermal energy. Energy from CSP can be stored by limestone calcination (endothermic reaction) at high temperatures producing pure streams of CaO and CO2. This energy can be later released when demand increases by means of carbonation reaction (exothermic) at relatively high temperatures. In order to produce power, the energy released in the carbonation reaction has to be transferred to a Rankine cycle. Calciner reactor is a complex system where heterogeneous chemical reactions take place while absorbing heat from a solar concentrating equipment. It is a key element of the process. Depending on the design and distribution of heat along the calciner, the amount of heat required in this reactor to store the same amount of chemical energy in the form of lime varies and the temperature of the solids strongly varies. Optimal design and operating conditions will minimize average temperature in the calciner for a given flow of produced lime. In this work, the modelling of a multi-stage solar calciner is described in the frame of a new solar-based CSP plant. The reactor will consist in a number of downward entrained flow design reactors, and the model encompasses fluid dynamics, chemical kinetics and energy balance. The results, provided along a 1-D discretization, comprise conversion rates, gas temperatures and flow rates, and heat transfer rates.

Conference paper

Hodgson P, Sceats M, Majumder K, Hills T, Song Q, Fennel P, Gao R, Tan R, MacFarlane D, Forsyth M, Howlett Pet al., 2018, Nano-active electrode materials, Pages: 373-374

Conference paper

Hills TP, Sceats M, Rennie D, Fennell Pet al., 2017, LEILAC: Low cost CO2 capture for the cement and lime industries, 13th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: Elsevier, Pages: 6166-6170, ISSN: 1876-6102

The LEILAC project will apply a revolutionary carbon capture technology to the cement and lime industries. It aims to enable the capture of unavoidable process CO2 from limestone calcination for no energy cost and no extra capital cost (apart from compression). It is being developed by a consortium in a €21M five-year Horizon 2020 project. A 240 t/d pilot will be built atHeidelbergCement’s plant in Lixhe, Belgium, demonstrating that 95% of a plant’s process CO2 emissions could be captured (around 60% of a plant’s total direct CO2 emissions), and on-going R&D activities are reducing the uncertainties and risks involved.

Conference paper

Hills T, 2016, Highlights from Carbon Capture and Storage: Faraday Discussion, Sheffield, UK, July 2016, Chemical Communications, Vol: 52, Pages: 13323-13326, ISSN: 1359-7345

Journal article

Lee JM, Rochelle G, Styring P, Fennell P, Wilson G, Trusler M, Clough P, Blamey J, Dunstan M, MacDowell N, Lyth S, Yao J, Hills T, Gazzani M, Brandl P, Anantharaman R, Brandani S, Stolaroff J, Mazzotti M, Maitland G, Müller C, Dowson G, Gibbins J, Ocone R, Sedransk Campbell K, Erans M, Zheng L, Sutter D, Armutlulu A, Smit Bet al., 2016, CCS - A technology for now: general discussion., Faraday Discuss, Vol: 192, Pages: 125-151, ISSN: 1359-6640

Journal article

Smit B, Graham R, Styring P, Yao J, Clough P, Lee J-SM, MacDowell N, Lyth S, Rochelle G, Hills T, Wilson G, Petit C, Kemper J, Cuellar-Franca R, Dowson G, Gazzani M, Fennell P, Sutter D, Scholes C, Azapagic A, Bell R, Gibbins J, Mazzotti M, Maitland G, Brandani S, Ocone R, Mota-Martinez M, Dunstan M, Liang P, Anantharaman R, Joss L, Stolaroff Jet al., 2016, CCS - A technology for the future: general discussion, Faraday Discussions, Vol: 192, Pages: 303-335, ISSN: 1359-6640

Journal article

Zheng L, Hills TP, Fennell P, 2016, Phase evolution, characterisation, and performance of cement prepared in an oxy-fuel atmosphere, Faraday Discussions, Vol: 192, Pages: 113-124, ISSN: 1364-5498

Cement manufacture is one of the major contributors (7-10%) to global anthropogenic CO2 emissions. Carbon capture and storage (CCS) has been identified as a vital technology for decarbonising the sector. Oxy-fuel combustion, involving burning fuel in a mixture of recycled CO2 and pure O2 instead of air, makes CO2 capture much easier. Since it combines a theoretically lower energy penalty with an increase in production, it is attractive as a CCS technology in cement plants. However, it is necessary to demonstrate that changes in the clinkering atmosphere do not reduce the quality of the clinker produced. Clinkers were successfully produced in an oxy-fuel atmosphere using only pure oxides as raw materials as well as a mixture of oxides and clay. Then, CEM I cements were prepared by the addition of 5 wt% gypsum to the clinkers. Quantitative XRD and XRF were used to obtain the phase and elemental compositions of the clinkers. The particle size distribution and compressive strength of the cements at 3, 7, 14, and 28 days' ages were tested, and the effect of the particle size distribution on the compressive strength was investigated. Additionally, the compressive strength of the cements produced in oxy-fuel atmospheres was compared with those of the cement produced in air and commercially available CEMEX CEM I. The results show that good-quality cement can be successfully produced in an oxy-fuel atmosphere and it has similar phase and chemical compositions to CEM I. Additionally, it has a comparable compressive strength to the cement produced in air and to commercially available CEMEX CEM I.

Journal article

Smit B, Styring P, Wilson G, Rochelle G, Donat F, Yao J, Trusler M, Adjiman C, Lyth S, Lee J-SM, Hills T, Brandl P, Gazzani M, Cuellar-Franca R, Fennell P, Sutter D, Bui M, Scholes C, Dowson G, Gibbins J, Joss L, Maitland G, Brandani S, Garcia-Gutierrez P, Zhang Y, Muller C, Jackson G, Ocone R, Joos L, Bell R, Graham Ret al., 2016, Modelling - from molecules to megascale: general discussion, Faraday Discussions, Vol: 192, Pages: 493-509, ISSN: 1359-6640

Journal article

Hills, Florin N, Fennell PS, 2016, Decarbonising the cement sector: a bottom-up model for optimising carbon capture application in the UK, Journal of Cleaner Production, Vol: 139, Pages: 1351-1361, ISSN: 0959-6526

Industrial processes such as Portland cement manufacture produce a large proportion of anthropogenic carbon dioxide and significantly reducing their emissions could be difficult or expensive without carbon capture and storage. This paper explores the idea of synchronising shutdowns for carbon capture and storage installation with major shutdowns required to refurbish major process units at industrial sites. It develops a detailed bottom-up model for the first time and applies it to the United Kingdom’s cement industry. This research demonstrates that several policy and technology risks are not identified by the top-down models and it highlights the importance of reducing shut-down times for capture plant construction. Failure to do so could increase installation costs by around 10 per cent. This type of approach, which is complementary to top-down modelling, and the lessons learned from it can be applied to other capital- and energy-intensive industries such as primary steel production. It provides important information about what actions should be prioritised to ensure that carbon capture and storage can be applied without extra unnecessary shutdowns which would increase the overall cost of carbon dioxide mitigation and could delay action, increasing cumulative emissions as well.

Journal article

Fennell PS, Zhang Z, Hills T, Scott Set al., 2016, Spouted Bed Reactor for kinetic Measurements of Reduction of Fe2O3 in a CO2/CO Atmosphere Part I - Atmospheric Pressure Measurements and Equipment Commissioning, Chemical Engineering Research & Design, Vol: 114, Pages: 307-320, ISSN: 1744-3563

A high pressure and high temperature spouted bed reactor, operating in fluidisation mode, has been designed and validated at low pressure for the study of gas-solid reaction kinetics. Measurements suggested the bed exhibited a fast rate of gas interchange between the bubble and particulate phases. Pressurised injection of the particles to the bottom of the bed allowed the introduction of solid reactants in a simple and controlled manner. The suitability of the reactor for the purpose of kinetic studies was demonstrated by investigation of the intrinsic kinetics of the initial stage of the reduction of Fe2O3 with CO over multiple cycles for chemical looping.Changes of pore structure over the initial cycles were found to affect the observed kinetics of the reduction. The initial intrinsic rate constant of the reduction reaction (ki) was measured by using a kinetic model which incorporated an effectiveness factor. The uncertainty arising from the measurement of particle porosity in the model was compensated for by the tortuosity factor. The average activation energy obtained for cycles three to five was 61 ± 8 kJ/mol, which is comparable with previous studies using both fluidised beds and thermogravimetry.

Journal article

Hills T, Leeson D, Florin N, Fennell Pet al., 2016, Carbon capture in the cement industry: technologies, progress, and retrofitting, Environmental Science & Technology, Vol: 50, Pages: 368-377, ISSN: 0013-936X

Several different carbon-capture technologies have been proposed for use in the cement industry. This paper reviews their attributes, the progress that has been made toward their commercialization, and the major challenges facing their retrofitting to existing cement plants. A technology readiness level (TRL) scale for carbon capture in the cement industry is developed. For application at cement plants, partial oxy-fuel combustion, amine scrubbing, and calcium looping are the most developed (TRL 6 being the pilot system demonstrated in relevant environment), followed by direct capture (TRL 4–5 being the component and system validation at lab-scale in a relevant environment) and full oxy-fuel combustion (TRL 4 being the component and system validation at lab-scale in a lab environment). Our review suggests that advancing to TRL 7 (demonstration in plant environment) seems to be a challenge for the industry, representing a major step up from TRL 6. The important attributes that a cement plant must have to be “carbon-capture ready” for each capture technology selection is evaluated. Common requirements are space around the preheater and precalciner section, access to CO2 transport infrastructure, and a retrofittable preheater tower. Evidence from the electricity generation sector suggests that carbon capture readiness is not always cost-effective. The similar durations of cement-plant renovation and capture-plant construction suggests that synchronizing these two actions may save considerable time and money.

Journal article

Hills TP, Gordon F, Florin NH, Fennell PSet al., 2015, Statistical analysis of the carbonation rate of concrete, CEMENT AND CONCRETE RESEARCH, Vol: 72, Pages: 98-107, ISSN: 0008-8846

Journal article

Hills T, Gambhir A, Fennell PS, 2014, The suitability of different types of industry for inter-site heat integration, Pages: 423-434, ISSN: 2001-7979

Several studies have shown that some highly-intensive processes are suitable for heat integration with each other (inter-site heat integration). This paper shows the results of an integration of the waste heat sources and potential sinks across several industries which have not yet received much attention for inter-site heat integration. The purpose of this paper is not to suggest that any particular configuration is currently possible, it is to demonstrate the significant theoretical savings and stimulate discussion of the where future research (e.g. into high temperature heat exchangers or solid to gas heat exchangers). By building two theoretical heat exchange networks, one to maximise heat recovery and one to maximise electricity generation, the characteristics of different process streams which are conducive or obstructive to successful, profitable integration can be identified. Heat recovery is slightly more profitable than electricity generation on first examination, but there are several major issues which are difficult to quantify and will add significant cost. In general, processes involving large quantities of liquids and condensing and evaporating gases, such as refineries, offer significant potential. Processes with incondensable, low-pressure gases and solid streams, such as cement plants, generally gain less profit from inter-site heat integration. All costs are in 2013 Euros.

Conference paper

Napp TA, Gambhir A, Hills TP, Florin N, Fennell PSet al., 2013, A review of the technologies, economics and policy instruments for decarbonising energy-intensive manufacturing industries, Renewable & Sustainable Energy Reviews

Industrial processes account for one-third of global energy demand. The iron and steel, cement and refining sectors are particularly energy-intensive, together making up over 30% of total industrial energy consumption and producing millions of tonnes of CO2 per year. The aim of this paper is to provide a comprehensive overview of the technologies for reducing emissions from industrial processes by collating information from a wide range of sources. The paper begins with a summary of energy consumption and emissions in the industrial sector. This is followed by a detailed description of process improvements in the three sectors mentioned above, as well as cross-cutting technologies that are relevant to many industries. Lastly, a discussion of the effectiveness of government policies to facilitate the adoption of those technologies is presented. Whilst there has been significant improvement in energy efficiency in recent years, cost-effective energy efficient options still remain. Key energy efficiency measures include upgrading process units to Best Practice, installing new electrical equipment such as pumps and even replacing the process completely. However, these are insufficient to achieve the deep carbon reductions required if we are to avoid dangerous climate change. The paper concludes with recommendations for action to achieve further decarbonisation.

Journal article

Dean C, Hills T, Florin N, Dugwell D, Fennell PSet al., 2013, Integrating Calcium Looping CO2 Capture with the Manufacture of Cement, GHGT-11, Vol: 37, Pages: 7078-7090, ISSN: 1876-6102

Journal article

Shah N, Vallejo L, Cockerill T, Gambhir A, Hills T, Jennings M, Jones O, Kalas N, Keirstead J, Khor C, Mazur C, Napp T, Strapasson A, Tong D, Woods Jet al., 2013, Halving Global CO2 Emissions: Technologies and Costs, Publisher: Imperial College London

Report

Fennell PS, Florin N, Napp T, Hills Tet al., 2012, CCS from industrial sources, Sustainable Technologies, Systems & Policies, Pages: 17-17, ISSN: 2220-2765

Journal article

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