ULECES: Ultra low energy cement synthesis: A radical process change to achieve green and sustainable technologies

The proposed project is to investigate the synthesis of cement mineral powders using a molten salt process. The conventional method of cement production is to heat limestone and clay together in kilns at temoeratures equal to or greater than 1450 degC and then to grind the material to the required particle size. For each tonne of product a similar amount of CO2 is produced, leading to global emissions of 1,800 Mt CO2 per annum. Cement therefore has a high embodied energy (up to 6 GJ/tonne) in terms of heating and grinding. In addition, cement is a globally important product. It is used to produce 6000 Mm3 of concrete annually at a global sales value of 450,000M and concrete is the principal material used by the construction industry, a sector that accounts for 11% of global GDP (10% of UK GDP) and employs more than 100 million people worldwide (1.5M in the UK). Hence, there is no doubt of the global importance of cement, which comes at the price of significant environmental impacts.Since the market for cement is of very high volume but the value of the product itself is relatively low (50/tonne), the cement industry is slow to incorporate significant process changes to reduce its emissions. However, if we are serious about meeting the challenges of climate change, new methods of manufacturing such products must be developed to reduce the energy demand and, hence, the subsequent CO2 emission levels. This proposal seeks to do just that, by massively reducing the emissions of CO2 from cement production through the novel synthesis of anhydrous cement phases using a molten salt route, reducing the total energy required and the temperatures involved, thereby allowing renewable energy sources to be integrated with the process (i.e. lower temperatures can be provided by electric heating, rather than by fossil fuel firing). The work will apply equilibrium thermodynamic modelling of molten salt systems to guide experimental synthesis of the main tri-calcium silicate product and will also investigate the possibility of using similar routes to produce other principal cement clinker minerals (bespoke cements that are attractive to industry and are, hence, of higher value, up to 250/tonne). The energy requirements of each synthetic route will be determined alongside the chemical kinetics of formation of the compounds in the melts, whilst the crucial high-temperature separation stage will be investigated experimentally. The results of the research will go a long way to optimising the new process with respect to commercial exploitation.This proposal represents an innovative, radical approach to the development of green and sustainable technologies through the development of novel, complex chemistry and high-temperature (up to 800 degC) process engineering. The proposed work programme is multidisciplinary in nature, involving chemical engineers, material scientists, chemists and geochemists and incorporating a high level of expertise in the manufacture of cement, its chemical and physical properties and in molten salt systems.