POWER
Much of the world’s 3.1 million installed MW power generation capacity is over thirty years old, particularly in the industrialized countries. Typically, the average efficiency of coal-fired power stations is 30-35%. For gas-fired power stations the efficiency varies from 35-43% for open cycles and 50-58% for combined cycles. Although the efficiency of coal-fired units with modern combustion technology is above 40%, this state of affairs has (rightly) caused considerable concern, both in terms of conservation of resources and of C02 emissions (van der Burgt, Cantle, and Boutkan 1992). Over the last 20 years a vast amount of work has gone into improving existing combustion technologies as well as investigating alternatives. Of the potential alternatives the use of gasification to produce a suitable fuel for highly efficient gas turbines, the IGCC has continually proved to be a leading contender.
The power industry is worldwide the largest man-made emitter of C02 with 33% of the total. (The transport sector is the next largest with 25%.) The increasing use of natural gas as a feedstock for gas turbines (the “dash-to-gas”) has allowed the power sector to reduce emissions on new capacity substantially, even though much of the motivation lies in the reduced investment and shorter construction times associated with gas turbine technology. However, the medium-term picture has to take account of the limits in natural gas supply. By 2030 Europe will be reliant on gas imports for some 70% of its supply (European Commission 2001). So alternatives to this simple solution are required.
Typical efficiencies of the current generation of steam cycle power plant, including flue gas desulfurization and NOx abatement are 40-42%. Ultra-supercritical cycles in operation have 43%, and IGCCs 38-43%. Serious assessments project between 46% and 50% as being possible with these technologies in the next 10 years. Looking at these figures, one should bear in mind that a four-point increase in efficiency represents about 10% less C02 production per unit of power produced.
Already there is a capacity of some 3800MW in installed IGCCs plus 3500 MW in projects currently under development or construction. Much of this is built in association with oil refineries, where synergies in the residue or petroleum coke disposal as well as in hydrogen production have encouraged their development. Coal-based projects are following.