DrTomHills

Summary

I am an Academic Visitor in the Department of Chemical Engineering at Imperial College London, collaborating on research projects such as LEILAC, a €21M, 5-year Horizon 2020 project.

My areas of expertise are the technologies, economics and policies required to decarbonise industrial processes, with a particular focus on carbon capture and storage (CCS) in the cement sector.

I am interested in developing and working on projects which involve reducing the carbon dioxide emissions of a range of energy-intensive industries such as cement, lime, paper, and iron and steel.

I currently work for Calix, a company developing materials to solve global challenges through new solids processing technologies. We make very high surface area powders which are used in a wide range of applications. We are rapidly expanding into other industrial sectors such as low-carbon cement and lime manufacture via projects such as LEILAC and ANICA. Our research in this area focuses on applying our Direct Separation technology to capture process-derived CO2 emissions, i.e. those from calcining mineral carbonates.

As well as publishing academic papers on CCS in cement, I have contributed to various projects with Imperial Consultants.

I graduated with a PhD from Imperial College in August 2016 on the topic of carbon capture in the cement industry (see below). I was funded by the Grantham Institute, Climate-KIC and Cemex Research Group AG. Before this, I received a First Class Masters of Engineering (Hons) in Chemical and Nuclear Engineering from Imperial College in 2011.

I took a break from my PhD in 2013 to work at the Grantham Institute - Climate Change and the Environment to work as a Research Assistant on industrial decarbonisation policy. This role led to presentation of results at a European energy efficiency conference.

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Phd research

My PhD research centred around two main topics: the quantification of CO₂ uptake by concrete over its lifetime, and the detemrination of the suitability of the  calcium looping CO₂ capture process with cement manufacture. My supervisors were Prof Paul Fennell and Dr Nick Florin.

Absorption of CO₂ by concrete

Limestone (calcium carbonate) is the main feedstock for cement production. Cement is used to make concrete (mainly calcium hydroxide), which absorbs CO₂ from the atmosphere over time, reverting to calcium carbonate. The determination of this rate is of great importance: millions of tonnes of CO₂ are absorbed every year. I undertook an exhaustive review of the data in the literature and has applied statistical methods to estimate the rate at which the absorption happens. I then coupled this rate with cement production and used data to estimate the amount of CO₂ absorbed by all the concrete in the world, over a 125-year period.

Integrating cement manufacture and calcium looping CCS

Post-combustion carbon capture processes remove CO₂ from the gases emanating from the combustion of fuels in air. Calcium looping (CaL) is one such process, but has a major drawback: the calcium oxide (CaO) sorbent which separates the CO₂ from the flue gas loses its CO₂ carrying capacity over time and so must be removed and replaced by fresh limestone. This produces a waste stream of low surface-area, ‘spent’ calcium oxide. Calcium looping becomes more financially viable if this waste stream can be used as a feedstock in cement manufacture, especially if the calcium looping process captures the cement plant's CO₂ in the first place. Therefore, the validation of this coupling of CO₂ capture and cement production is imperative. I investigated the effects on the performance of cement made with this ‘spent’ calcium oxide.

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