September 1, 2009

Combined-Cycle Carbon Capture: Options and Costs, Part I

Justin Zachary, PhD, Bechtel Power Corp.

Uncertainty about CO₂ emissions legislation is prompting power plant owners to consider the possibility of accommodating "add-on" CO₂ capture and sequestration solutions for coal-fired plants in the future. Those same plant owners may be overlooking the possibility that future natural gas – fired combined cycles will also be subject to CO₂ capture requirements. This month we examine the capture options. In a future issue, Part II will present the installation and operating costs of different carbon capture technologies.

Just when you thought that carbon capture and sequestration (CCS) only applied to coal-fired plants, European regulators are talking about extending the technology requirement to natural gas – fired plants. In fact, many utilities and equipment suppliers are now working on front-end engineering designs for capturing the CO₂ from gas plants.

At present, the timing and extent of regulations governing the process are unknown. Also, none of the current technologies has emerged as the dominant solution of choice, although many new and innovative alternatives are in various stages of research, development, or testing. For plants currently in the planning or design stage, owners; engineering, procurement, and construction contractors; and equipment suppliers are struggling to determine which features need to be included in new equipment designs today for future CCS systems.

In this context, the term "CO₂ capture ready" requires careful consideration. Beyond the technical challenges, the commercial investment in those specific features aimed at future CCS must be justified. There is a significant risk in selecting a specific CCS technology today because the technology is likely to become quickly obsolete, further complicating future retrofits.

This article focuses on "add-on" features that do not require substantial modification of existing equipment, thereby making those technologies available today. Because CO₂ capture is an energy-intensive process, this article examines the impact on plant performance of large steam extractions for CO₂ capture processes. Large quantities of electrical power for CO₂ compression will also be required. Part II of this article, slated for an upcoming issue of POWER, will evaluate the range of prices that should be expected if carbon capture is required from gas-fired combined-cycle plants.