Our Research
Microwave Treatment of Minerals and Ores
5% of global electrical energy generation is used to grind rocks to liberate the valuable mineral phases. This is because of the very large amount of material being processed, and the very poor efficiency of existing grinding processes, which is less than 1% in terms of creation of new surface. Microwave processing offers significant advantages in this area, as microwaves can induce micro-fractures within the rocks. Microwave pre-treatment has been shown to lead to order of magnitude reductions in the energy requirements and costs of grinding coupled with increases in recovery of the valuable mineral.
Generation of Supercritical Water
This project has delivered several portable, continuous supercritical water systems using microwaves. This opens up a whole range of novel applications ranging from rapid synthesis of chemicals to destruction of chemical weapons in the form of a portable, continuous, and energy efficient system.
There have been significant scientific and engineering challenges to achieving this goal and therefore a highly multidisciplinary approach has been taken. The critical point of water is 374°C and 221 bar and the materials of construction required to contain these temperatures and pressures are a severe limitation when designing a microwave heated system. Such a system needs to create high microwave power densities and generate ultra-rapid heating of a continuous stream of water at high pressure across the subcritical into the supercritical region.
There is potential to extend this technology to other highly polar or ionic fluids that also couple rapidly to microwave fields; these include propanol, ethanol and acetone, all of which have significantly lower critical points.
Materials Synthesis
In collaboration with the School of Chemistry at the University of Glasgow we are investigating the ultra-rapid synthesis of refractory transition metal carbides, such as the widely used tungsten carbide. The work is focussed on building an understanding of microwave heating of these materials as well as developing a novel synthesis techniques. To date a number of carbides have been synthesised on the sub-minute timescale and an understanding of how these materials interact with microwave energy has been developed.
Remediation of Contaminated Drill Cuttings
Environmental legislation prevents the direct discharge of drilling wastes from North Sea oil platforms, and the current practice is to ship the wastes to shore for treatment and landfill. A process has been developed which uses microwave technology to remove the contaminant oils from the waste cuttings, and combines the multidisciplinary expertise of the University of Nottingham, University of Stellenbosch and the University of Greenwich. The principle advantage of microwave technology is that the treatment times are of the order of seconds, so the waste can be treated using equipment with a small footprint, ideal for an offshore environment where space is at a premium. The recovered oil can be re-used and the inert solids discharged offshore, removing the need for transport and landfill of the waste cuttings. The current scale is approximately 1 tonne per hour.
Microwave Treatment of Contaminated Soils
Many of the brown-field sites in the UK, Europe and US are contaminated with hydrocarbons to the extent that the land cannot be used for development. We are involved in a multi-partner UK based consortia to produce a 1 tonne per hour pilot scale microwave treatment system. The use of microwaves leads to the energy efficient removal of both light and heavy hydrocarbon contaminants, including PAHs. The aim is to develop a portable microwave treatment system that can be transported to field locations, which will improve the economic viability of restoring many of the smaller and more remote contaminated sites. This will make the land available for re-use, reducing the pressure from development on green belt and other sensitive areas of land.
Sintering and Vitrification using Microwave Techniques
Up to 1/3 of all quarried products are landfilled because they do not meet the size criteria for use within the construction industry. Microwave heating can be used to provide an energy-efficient sintering and vitrification technique to make coarser materials which are suitable for use as aggregates, thus reducing the environmental impacts due to landfill. In collaboration with the Nottingham Transportation Engineering Centre we are investigating the sintering of mineral wastes and waste materials from electrical power generation to produce light-weight construction materials with a high value. The performance of the microwave-manufactured materials is currently being assessed against established aggregates for a range of different applications.
Pyrolysis of Municipal Waste
Recent government and EU directives have placed strict limits and set adventurous targets for the control and elimination of waste sent to landfill. One of the problem materials is biodegradable municipal waste, and the pyrolysis of these materials has been evaluated using microwave treatment systems. The waste can be converted into a high calorific-value char as a solid product, a small amount of organic liquid and a gas stream which can be used as an energy source. The char can be used as a renewable fuel source for co-firing at existing pulverised fuel power plants, and reduces the need for fossil fuels in power generation.
We have many other projects involving industry and government departments in the UK and overseas.
