This project aims to provide the technological base that will enable Wales to create a new industry in UCG, which will make a significant contribution to Wales’ quest to become self sufficient in energy
Underground Coal Gasification (UCG) is the process by which coal is converted in-situ into a gas product that can be combusted for power generation or used as a chemical feedstock. UCG exploits coal resources that are either uneconomical to mine with conventional mining methods or are inaccessible due to depth, geology or other mining and safety considerations.
Coal seams are accessed from the surface via boreholes. An injection borehole introduces oxygen or air to the coal seam in order to combust a proportion of the coal in-situ. In addition, water is added to the system and drives the gasification of the remaining coal, producing a versatile synthetic gas product (known as ‘syngas’) that is extracted via a second borehole. This syngas can be combusted directly for energy generation and can also be converted into a variety of high-value products, such as transport fuels, fertilisers for food production, plastics, methanol, waxes and detergents.
By developing the knowledge and know-how, not only will Wales reap the short term benefits of secure energy supplies and job creation, but Wales will also position itself at the forefront of this emerging worldwide technology. The ability to export Welsh knowledge and technology will be an associated aim of the project. The specific project aims are to:
Every UCG project is planned for an end user, which is usually a power plant. The size of the power plant depends on the amount of electricity required per day (MWh/day) in that area for a period of time (normally over a number of years). The Seren project has developed a tool to assess the resource required to meet this demand. This tool is known as a Coal Assessment Tool.
The project has two main research theme areas.These are the scientific / technical research area; and the environmental research area.
Seren’s work in the scientific / technical research area investigates the optimisation of the UCG process by understanding the impact of its operation parameters. The UCG process is not well understood, with widespread scientific and technical gaps. Further work is required to access the practicality and commercial viability of the UCG process by achieving stable gasification conditions.
The environmental research area is concerned with groundwater and surface water contamination, subsurface and surface disturbance (subsidence) and the air pollution impact of UCG.
In order for the project to achieve its aims, Seren is addressing the following main issues:
Seren has developed a bespoke high pressure high temperature rig. The rig can be used to test different coal in order to determine how it will react with various gases at pressures of up to 50 bar and temperatures of up to 900°C. The rig can be run in two different ways and provide gasification data or environmental data which will help the commercial assessment of coals throughout Wales.The gasification of coal chars with a combination of oxidants at different pressures and temperatures will determine the effect of several operation variables, namely temperature, pressure and gasifying agent composition. Additionally, information on other process parameters, such as gas yield, carbon conversion, cold gas efficiency, heating value of the gas, pressure and temperature operation limits, together with the re-activities of the coal, can be provided.The environmental data is produced by the devolatilisation of coal at different pressures and temperatures in order to quantify and analyse the resulting contaminants.Research and experimental work is currently being carried out on different types of Welsh coal.
The UCG model that is being developed will provide all the initial information required by investors who are deciding whether or not to proceed with a UCG project at a specific site. This model can provide information for desk top studies and pre-feasibility or feasibility studies for a UCG project at a specific site, including economic evaluation. It will establish a knowledge base for the assessment of the entire UCG process.The model will provide guidelines on assessment for UCG, including three different software tools. These are an energy model, a coal resource assessment tool and a chemical model.
A methodology for environmental impact assessment will be developed. This will be recognised by the agencies associated with licensing UCG applications.
This work will involve the identification of the contaminants resulting from laboratory experiments testing coals of various rank under varying gasification and pyrolysis conditions, thereby determining the controls on the solubility and mobility of the potential contaminants in groundwater. Finally, this data will be combined with hydro-geochemical and geotechnical models to feed into the existing Environmental Risk Assessment Framework. This will enable the implementation of a UCG commercial operation in Wales that complies with current legislation.