Experimental and demonstration plants

Summary

Currently, fluidized bed combustion (FBC) research and development (R&D) focuses on pressurized FBC (PFBC) work on first and second generation systems, and support research for both atmospheric and pressurized applications (Botros, 1990). This recent shift in focus has occurred because utility-sized atmospheric FBC have become nearly commercial; a significant number of mid-sized units, producing 50 000–100 000 kg/h of steam, are now in use.

First generation, combined cycle PFBC is in the demonstration stage at Tidd, Escatrón and Värtan. Other demonstrations are planned at Wakamatsu, DAWID-Saar and probably also at a Polish site. A (300 MWe) utility demonstration by American Electric Power (AEP) is at an advanced stage of design/negotiations. A more advanced 70 MWe demonstration of a scaleup of Pyropower/Ahlstrom’s 10 MW pilot unit is being designed/negotiated for a De Moines (Iowa, USA) site. Deutsche Babcock and M.W. Kellogg are also at early stages of design/negotiation for demonstrating their technologies.

Experimental units continue to produce invaluable data, e.g. Grimethorpe’s data on coal slurry feed systems (functioned well down to 23% water and the slurry use has reduced tube erosion). New York University (NYU) has tested particle control devices on its system. Cross-flow and granular-bed filters met environmental standards and turbine requirements. High-pressure operation prevented delamination in the cross-flow filter. In technical support of PFBC, Morgantown Energy Technology Center (METC) is building a pressurized warm 0.6 m bed for fluidization research. AEP tested several hot gas filters on the Clean Coal Technology (CCT) Project at Tidd plant.

Component and pilot testing of a second generation, advanced cycle PFBC system are being performed by Foster Wheeler (FW). A design analysis predicts that the FW system can reduce the cost of electricity by 20% over conventional coal-fired systems, exceed 45% fuel efficiency, produce emissions at half the US New Source Performance Standards (NSPS), operate economically on a range of coals and sorbents, be made in modules up to 225 MWe, and be shop-fabricated and barge-shipped. M.W. Kellogg has completed a competing conceptual system design based on the alternative of transport reactors and is seeking demonstration opportunities.

Some of the issues that need to be resolved in order to scale up to utility-sized plants are understanding the mixing process in the combustor and to gain better understanding of erosion (being studied for steam tubing in pressurized systems as well as atmospheric systems).