DOE - Fossil Energy Techline - Issued on:  October 16, 2001

DOE Launches Project to Improve Materials for Supercritical Coal Plants

New Research Effort Intended to Boost Global Competitiveness of U.S. Boiler Manufacturers

Pittsburgh, PA - In a move largely designed to help American companies compete with their European and Japanese counterparts in producing stronger materials for ultra-high temperature coal-fired power plants, the Department of Energy is preparing to fund a new research initiative with a consortium of boiler manufacturers and the Electric Power Research Institute (EPRI).

The Energy Department, through its National Energy Technology Laboratory, will provide $10.5 million over the next five years to The Energy Industries of Ohio, Inc.

Headquartered in Independence, OH, the organization is leading a consortium of four major U.S. boiler manufacturers (Alstom, McDermott Technologies with its affiliate Babcock and Wilcox, Foster Wheeler, and Babcock Borsig), the Electric Power Research Institute, the Ohio Coal Development Office, and the Oak Ridge National Laboratory.

The consortium will provide an additional $4.8 million.

The National Energy Technology Laboratory will manage the effort, act as a liaison between the consortium and the utility industry, and advise the consortium on environmental and systems issues.

At the end of five years, a family of pipes and components made of advanced steel capable of withstanding operating temperatures up to 1,400^o F is to be produced. The project also contains provisions for developing advanced alloys suited to 1,600^o F if needed. Foreign boiler makers' products are typically designed to operate at temperatures approaching 1,300^o F.

Higher operating temperatures in coal-fired plants can lead to higher efficiencies - meaning that more electricity can be generated from a given amount of coal.

Today's power plants are typically 35 percent efficient. By developing better materials that can withstand higher temperatures, the Energy Department hopes to boost efficiencies to 52 to 55 percent. These efficiency gains, alone, would cut the release of carbon dioxide and other emissions by nearly 30 percent.

The project centers around five main goals:

• Identifying materials that limit operating temperatures and thermal efficiency of coal-fired plants,

• Defining and implementing ways of producing improved alloys, fabrication processes and coating methods that allow boilers to operate at 1,400^o F,

• Participating in the certification process of the American Society of Mechanical Engineers and generating data to lay the groundwork for ASME-code-approved alloys,

• Defining issues affecting the design and operation of ultrasupercritical plants operating at 1,600^o F, and

• Working with alloy makers, equipment vendors and utilities to develop cost targets and promote the commercialization of alloys and processes expected to emerge from this effort.

Background

The new effort could help American boiler manufacturers regain an important competitive edge in an area they had pioneered almost half a century ago.

In the early 1950s, American manufacturers began developing ultra-supercritical steam generators designed for 1,200^o F, and pressures reaching 5,000 pounds per square inch. When they encountered unexpected problems, such as superheater corrosion and creep cracking - which occurs when pipes are stretched out of shape and are weakened because of excessive temperatures and pressures - manufacturers began building plants to operate under less-severe conditions.

These, too, went through a "teething" stage, encouraging U.S. utilities to restrict steam temperatures used in fossil-fuel plants to 1,000^o F and limiting pressures to 2,400 psi. Known as sub-critical boilers, they became the workhorse of American utility generation.

With coal abundant in the United States and because of other economic factors, U.S. boiler manufacturers had little incentive over the last 20-30 years to design or build ultra-supercritical steam cycle coal plants.

On the other side of the Atlantic, however, Europeans and the Japanese began building a new generation of coal plants within the last decade. With a limited supply of coal available to them, they had to extract as much energy from the fuel as possible. Efficiency and environmental performance, therefore, became salient features and foreign interest resurfaced in ultra-supercritical power plants.

U.S. boiler manufactures stayed abreast of foreign developments, largely through teaming arrangements with Japanese and European boiler manufactures. Joint studies showed that with minor changes in boiler materials, steam plants operating at 1,100^o F and 4,500 psi could be built.

Overall, manufacturers learned that 1) high-strength ferritic stainless steels for heavier components would avoid heat-related failures, 2) high-chromium creep-resistant stainless steel for superheater and reheater tubes resists corrosion, and 3) higher-strength low-alloy steels make better waterwalls.

Power Plant Issues Today

Today, the stakes are decidedly different as the U.S. faces an unprecedented growing demand to produce more and more electricity. Increasing demands for electricity are occurring just as environmental standards are becoming tougher, demanding cleaner, more reliable and more affordable power generation.

The goal of American utilities is to continue to burn coal under strict environmental regulations, a goal that is shared by Europe and Japan, both of which are experimenting with advanced ferritic steels capable of operating at 1,200^o F. Japan, for example, is building a new line of supercritical steam generators with steam temperatures that would reach 1,148^o F.

This goal would be achieved differently in the United States because so many aging coal plants have to be revitalized. Retrofitting existing plants with ultra-supercritical steam cycles is most definitely an option. But temperatures of 1,200o F would enhance efficiency by a marginal amount, so the push is to create a class of pipes and tubing that would hold up under 1,400^o F, and possibly 1,600^o F.

Amid this environment, DOE has begun developing the Vision 21 concept for an ultra-high efficiency, virtually pollution-free power plant of the future. DOE's new project to advance boiler materials could become part of the Vision 21 effort.

-End of TechLine -

Technical contact: Udaya S. Rao, DOE National Energy Technology Laboratory, 412/386-4743, e-mail rao@netl.doe.gov.