A Fossil Fuel Flickering Fast

But coal gasification, the greenest and most efficient method of coal-based power production, has been marginalised since then to the extent that it represents only a fraction of one per cent of the energy generation market.

Meanwhile, attempts to devise more environmentally friendly methods of burning coal could founder because they are still perceived as too dirty the smoke pollution in south-east Asia is a frightening reminder, of the profound effect that any kind of combustion has on the atmosphere.

Yet in 1988, clean coal seemed to be about to break through as a mainstream method of power generation. Cool Water, a 120 mw integrated gasification combined cycle (IGCC) power station in California, had just finished a five-year demonstration programme to rave reviews from its sponsors, who said it had proved the commercial viability of IGCC.

 

The electricity generating turbines in an IGCC plant are driven by burning a fuel gas which contains carbon monoxide, hydrogen and methane. The gas is produced by coal reacting with steam and oxygen.

An IGCC plant is about 20 per cent more efficient than a standard coal-burning power station at converting the energy from carbon into electricity.

Cool Water was sponsored by a group of Japanese and US engineering and electricity companies. But the problems for IGCC began because electricity generators did not support the emerging technology, according to Walt Patterson, a senior research fellow at the Royal Institute of International Affairs.

Because the coal people themselves have put such minimal effort behind advanced technologies, they have left it up to the engineering companies to make the running, he says. If they themselves had got behind advanced technologies, it would undoubtedly have had much more impact. The fault is with the coal producers for not recognising how important this was going to be to the future of their industry.

Mr Patterson says there is now little enthusiasm for IGCC in Europe, with backers of existing projects showing no interest in developing further plants.

The UKs National Power, which has a small stake in a 300 mw IGCC plant at Puertollano in Spain, says the capital costs of IGCC stations are so high that the electricity they produce has to be massively subsidised. The industry consensus puts the cost of IGCC-generated electricity at about one-and-a-half times that of electricity produced by gas-fired power stations.

Earlier this year, National Power, RJB Mining and Texaco launched a project to look at the feasibility of building a 400 mw plant in Yorkshire. If the study proves successful, National Power says the partners might seek a government subsidy.

But National Power does not see IGCC as a way to provide a long-term future for coal-fired electricity generation. We thought that it looked to be a very sound prospect for large-scale electricity generation and that it had advantages over other clean coal technologies including pressurised fluidised beds, it says.

All of the new plant that has come in has displaced coal. If you bring in more coal itll only displace coal; it wont displace gas.

Tomas Wangberg, president of ABB Carbons Swedish division, is less pessimistic about the prospects for coal. But he admits clean coal technologies remain marginal.

ABB Carbon has concentrated its research on methods of cleaner combustion rather than gasification. The company is the world leader in technology for pressurised fluidised bed combustion (PFBC).

PFBC involves burning crushed coal on a bed of inert particles, such as ash, sand or powdered limestone. A stream of air is passed through the bed and the combustion chamber is maintained at a pressure of between five and 20 atmospheres.

The process reduces emissions of gases that cause acid rain. The temperature of combustion is lower than in a conventional coal burner, meaning that fewer nitrogen oxides are formed. Calcium containing compounds in the bed trap out sulphur from the coal, reducing emissions of sulphur dioxide.

ABB Carbon currently runs five PFBC plans. The 400 mw capacity power station it is building in Japan will be the biggest in the world. As far as the operation and the complexity of the PFBC plant goes we have come a long way, says Mr Wangberg. But now we need to build a lot more to get the first capital cost down.

ABB sees PFBC as a compromise solution. It is less polluting and more efficient than simply burning pulverised coal, while it is cheaper than IGCC. Mr Wangberg says : We have somewhat less efficiency than the best IGCC plants but the problem is that IGCC plants are very complex and the first generation of these are being started up.

They are now learning how to operate them and they are getting pretty good. But the problem then is the capital cost is so high because the plant is so complex.

But Dennis Borwn, European research and development manager for Air Products and Chemicals, thinks companies will find it difficult to promote PFBC if the current pressure for global environmental regulation continues. What they are not saying is that they can sell the PFBC in places like China and India where environmental regulations are not that stringent, says Mr Brown.

Mr Patterson says there are other problems for companies looking to sell PFBC into newly industrialising countries.

The real growth areas would seem to be places like China but there are huge questions about technology transfer and the licensing conditions are so lax, he says. They may be able to build one plant but then see it cloned with no further royalties being paid.

With problems facing both PFBC and IGCC, some companies are looking to devise variations on the standard clean coal technologies in an attempt to try to reduce the cost of electricity produced using the techniques.

Air Products has just completed trails of a new method of gasification which it says can reduce the capital cost of building new plant by a quarter.

It achieves this by using waste streams from the gasification process to synthesise methanol, which can be stored and used to generate extra electricity at times of peak demand. Gasification is not cheap, says Mr Brown. This is one particular way you can reduce the capital cost by taking advantage of the slow periods in electricity demand.