Clean coal technologies for power generation

There has been a significant change in the perception of the future for coal fired power generation in Britain, Europe and indeed globally. There has been widespread recognition, reinforced by the predictions of international bodies such as the International Energy Agency and the European Commission, that coal will continue to be used in increasing, not diminishing, quantities for power generation, particularly in parts of the world including the USA, China, India and Europe, which have large resources of the fuel. In parallel, it has become increasingly urgent to reduce emissions of carbon dioxide because of its impact as a greenhouse gas on climate change. Whereas previously it might have been thought in the UK, and indeed in Europe more widely, that coal generation could be dispensed with and replaced by gas fired generation and renewables, it is now widely recognised, for example in The Stern Review, that coal fired generation needs to be cleaned up by the use of clean coal technology and carbon dioxide capture and storage (CCS) rather than substituted. During 2006, the shortage of gas, the disruption of supplies via the Ukraine in the winter and the price hikes in March and July resulted in a loss of confidence in gas supplies and confirmed that long term dependence on gas imports is inadvisable. There is also recognition now that gas fired generation will also need to be much cleaner if global CO2 targets are to be met. Replacement of coal by gas will not be sufficient for climate change mitigation. Carbon dioxide capture and storage will be needed on gas fired as well as coal fired power stations. EU and UK politicians and officials are now discussing the whole power generation mix and not just the part which renewables may play. The UK 2007 Energy White Paper and the EU Energy Package each point to the need for a diverse portfolio of energy sources for power generation to achieve security of supplies. Both emphasise the vital importance of coal in the generation mix and recognise cleaner coal has an essential role alongside energy efficiency, renewables, and nuclear in reducing emissions. The UK government has set up the Coal Forum with the objective ‘to help find solutions to secure the long-term future of coal-fired power generation and UK coal production’. The predicted reduction in the use of coal is no longer as steep as was envisaged. In 2006, 34% of the UK’s electricity was generated by coal, approximately the same as in 2003. Indeed for three months in the winter of 2006 half of the UK’s electricity was generated from coal. About 75% by capacity of the UK’s coal fired power stations have opted in to the large combustion plant directive (LCPD) and, with flue gas desulphurisation fitted, most will remain open to 2015 and beyond, contributing to security of supplies (see Fig. 1). Clean coal technologies were previously considered synonymous with gasification (IGCC) but now are seen to include a number of conversion technologies (including advanced supercritical boilers, fluidised beds and gasification) and a number of CO2 capture technologies (including postcombustion solvent absorption, oxyfuel firing and precombustion), all of which are likely to play a role in the plant mix since clean coal technologies are needed for existing plant (including recent plant in China, USA and Europe) as well as future plant. It is now widely anticipated that any new plant in Europe will be required to be capture ready. Alongside capture ready plant, a number of first of class CCS projects (often referred to as demonstration projects) are envisaged. The EU Directorates for Transport and Energy, Environment and Research are each backing an industry strategy, published by the European Technology Platform ‘Zero-emissions Power Plant’ (ETP ZEP), for 10 to 12 such demonstrations around Europe, to be operational by 2015. DG Environment and DEFRA/DTI in the UK are pushing ahead with the necessary regulations for CCS and clarification of the London Convention (now implemented) and OSPAR to allow storage beneath the ocean floor. Following consultation in 2005, in February 2006, the House of Commons Select Committee on Science and Technology published its findings on CCS, recommending early action on demonstration projects. The Treasury carried out a consultation on incentives for CCS and has announced a competition for Demonstration project(s) in the autumn 2007. Relatively recently it seemed that all of the new power plant required in the UK would be renewables (mostly wind) and gas (including CHP) and that there was plenty of time to build these plants. Now, the risks to future power supplies have become much clearer. The emergence of a gap by the end of 2015, caused by closures of Magnox nuclear stations (2.3 GW), opted out coal and oil stations (11 GW) and growth of demand (7 GW at 1% per year) is now recognised. The gap will be greater by 5 GW if the AGRs at Hunterston, Hinkley Point B, Hartlepool and Heysham do not achieve life extension (see Fig. 2). It has become accepted that there are limitations to the amount of renewables that can be incorporated on the grid, that it is becoming too late for new nuclear to make a significant contribution before 2016 and that the generation gap, which is now widely recognised as being 20–29 GW, will need to be filled Doosan Babcock Energy Limited, Renfrew, UK