and cold gas cleanup systems. Only limited use of first-generation PFBC and IGCC systems is expected in the United States. Demonstration programs for these technologies are under way both in the United States and abroad, and the main incentive to continue the domestic activity is to develop a foundation for second- and third-generation systems. On the other hand, the LEBS technology program outlined by DOE (1993a) does not appear to offer opportunities for development of a substantially more efficient, lower-emission system. Only if LEBS achieves a significantly lower cost than existing systems with comparable performance would its development be justified for near-term markets.

Assuming that Group I performance and cost objectives can be met, the market for Group 1 technologies will probably be limited to near-term installations where there is no economic penalty for carbon dioxide (CO2) emissions. Although the committee's baseline scenarios assume no such penalties for the near-term (1995-2005), it envisions new regulations or penalties aimed at forcing CO2 reductions during the mid-term period (2006-2020). Technologies in Group 1, with their limited efficiency improvements over existing plants, would be at a disadvantage relative to the newer Group 2 systems emerging in the mid-term period. The ''less demanding" scenario discussed in Chapter 4 assumes that economic penalties on CO2 emissions might not be imposed for the foreseeable future. This might well be the case in developing countries such as China, and Group 1 technologies might therefore be of potential export interest.

Group 2 and 3 Systems

In contrast to Group 1 systems, technologies in groups 2 and 3 are judged by the committee to have greater potential to meet future power generation and associated environmental requirements: all technologies in these two groups make use of advanced components to achieve higher efficiencies and lower emissions. Major questions of system integration and reliability will need to be addressed, and early pioneer installations could serve as a basis for improved systems.

The riskiest components appear to be the high-temperature heat exchanger and furnace required for the indirectly fired systems, and the hot gas cleanup systems for the advanced PFBC and gasification-based systems. It is not established that high-temperature gas turbines can tolerate the chlorine and alkali metals that may be present in FBC (fluidized-bed combustion) products or the sulfur and particulates in the gasifier products of IGCC systems. Although hot gas cleanup is a component of advanced IGCC systems, cold gas cleanup could still allow the technology to succeed, if at a lower efficiency. In this sense, IGCC is a somewhat less risky technology than PFBC.

The 1370 °C to 1425 °C (2500 °F to 2600 °F) gas turbine required for Group 3 systems is within the state of the art for aviation systems but is still under development for electric power generation systems and will require demonstration and testing. The IGCC-2 and IGAC systems with an advanced gas turbine

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