February 15, 2008

Alstom’s chilled ammonia CO2-capture process advances toward commercialization

Dr. Robert Peltier, PE

Taking the first step

Alstom’s first carbon capture pilot project is currently under construction at We Energies’ Pleasant Prairie Power Plant (P4) in Kenosha County, Wis. (Figure 2). Working closely with EPRI, Alstom is responsible for the design, construction, and operation of the $10 million pilot plant, which engineers hope will be able to extract 90% of the CO₂ from 1% of the flue gas produced by one of the plant’s two 617-MW coal-fired units. Project costs are spread among more than 30 project sponsors. The goal of the project is to capture about 15,000 tons of CO₂ per year (Figure 3).

  2. Beta version. This two-step, 5-MW (equivalent) pilot CO₂ capture process is being implemented at We Energies’ Pleasant Prairie Power Plant. Source: Alstom

 
3. Virtual design. This 3-D representation depicts the completed pilot plant at Pleasant Prairie. Courtesy: Alstom

Construction of the pilot plant began last September; the plant will be operational by press time. Alstom will then operate the plant for at least one year while EPRI evaluates the performance of the technology from several perspectives (Figure 4). Specifically, Alstom and EPRI will:

• Validate operation of the entire system on actual flue gas.
• Measure the actual heat of reaction and compare it to theoretical values.
• Develop and evaluate the process control logic and operating system.
• Operate the system in long-term tests to identify O&M issues and establish system reliability baselines.
• Conduct a techno-economic analysis of scaling up the system for commercial use (Figure 5). 

  4. Up and running. The chilled ammonia pilot plant began operation in January. Courtesy: Alstom 

  5. CAFE vs. CO₂ standards for plants. As with automotive fuel economy, the effect of overall power plant efficiency on CO₂ emissions can be significant. For example, a 47% efficient supercritical plant “naturally” has about 20% less CO₂ in its flue gas than a 37% efficient subcritical plant. Today’s U.S. coal-fired fleet has an average thermal efficiency of about 33%. The curves shown were derived from plants firing Pittsburgh #8 coal. Source: Alstom

“The development of cost-effective carbon capture technology is one of the most important environmental challenges facing the utility industry in the 21st century,” said Gale Klappa, chairman, president, and CEO of Wisconsin Energy, the parent company of We Energies. “This pilot is a crucial step in the research and development process necessary for achieving a long-term technology solution.”

This pilot project is just the latest in a long line of improvements at the Wisconsin plant. Last October, POWER designated P4 as one of its Top Plants of 2007 on the strength of several recently completed air emissions upgrade projects. We Energies has added a hot-side selective catalytic reduction (SCR) system to Unit 1 and a wet-limestone, forced-oxidation scrubber to both units. Unit 2 was retrofitted with a hot-side SCR system in 2003.