Case Study Technology & Innovation – Atmospheric Fluidised Bed Combustion Technology in the United States


The first of the innovation and technology case studies looks at atmospheric fluidized bed combustion technology in the United States. For more detail, take a look at the key references shown at the end of the post.

Atmospheric fluidized bed combustion (AFBC) originated in the chemical industry and was transferred to the power sector in the 1980s. At present AFBC is a commercially available electricity generation technology at capacities of up to 300 MW. The principal users of the technology are co-generators and independent power producers. It is estimated that more than 600 boilers (about 30 GW of installed capacity) are operating in North America, with a similar capacity operating in Europe, and more than 2,000 small “bubbling” AFBC boilers in China.


AFBC development and deployment has been supported by a portfolio of policy measures.

Research and development – AFBC technologies had been utilized in the chemical industry since the 1920’s. Preceded by early research into the power generation applications of AFBC in the United Kingdom, the US Federal Government instigated significant R&D into AFBC in the mid 1960’s with the goal of picking a winning coal technology that was both lower cost than traditional pulverized-coal boilers and could minimize the SOx and NOx emissions.

The early stage R&D focused on specific cost-reduction goals: namely, reducing fouling, corrosion and erosion of handling systems; temperature control systems (turn down systems); reliability of auxiliary systems, especially fuel feeding systems; and scale-up of the technology. These early efforts, did not result in a utility-scale boiler, however they were sufficiently successful to convince both government and industry that they were pursuing reasonable technological goals.

Development of the technology continued with the newly formed US Department of Energy (DoE) taking the lead in moving the focus from in house research to demonstration plants. These demonstration plants were used to test specific innovations such as feeding systems, the use of alternative fuels, methods for sulphur retention, and most importantly scale-up. The scaling up from pilot to commercial size was a critical issue for AFBC technology and the successful demonstration of utility-sale plant was key to the technology’s future commercial acceptance.

The demonstration program had two separate foci: (1) industrial demonstrations that were sponsored by DoE, and (2) utility scale demonstrations that were sponsored not only by DoE but also by the Tennessee Valley Authority (TVA) and Electric Power Research Institute (EPRI). The DoE demonstrations typically followed a “bubbling” technical route while TVA and EPRI trialled an alternative “circulating” technical route. Of these technical options the “circulating” route became the most viable option and is the most commonly used commercial technology.

Favorable Regulatory Environment – By the mid-1980s AFBC technology had been successfully demonstrated and was commercially available at utility scale capacities. It was well poised to take advantage of the opportunities created by the Public Utilities Regulatory Act (PURPA) of 1978. PURPA was a first step in the deregulation of the vertically integrated electricity industry in the United States and it mandated utilities to purchase electricity from particular types of small-scale power producers which included AFBC industrial co-generators. Because of PURPA, AFBC was able to capture a niche in the co-generation market, particularly where there was ready access to lower-grade fuels. Despite being an original driver for commercial interest in AFBC technologies, environmental concerns and the introduction of the 1990 Clean Air Act Amendments did not create a strong market for AFBC technologies, because for the purpose of SO2 compliance, AFBC has comparable environmental performance to conventional pulverized coal boilers equipped with scrubbers or fuel switching to low-sulphur coal. Ultimately, power companies chose the latter two methods as they were more cost-effective and less capital intensive. Had the CAA also included caps on NOx, AFBC would have had a comparative advantage over both these options.

In spite continued private investment, the opportunities created by PURPA, and the growing maturity of AFBC as an electricity generation technology, AFBC remains a niche technology with limited penetration of the electricity generation market in the U.S. and it has not been able to develop economic advantages over gas turbines and pulverized-coal boilers.


  • Early international cooperation and the sharing of experience, particularly between UK and US researchers and industries, was an important starting point for later, more detailed research.

  • Early government R&D support was instrumental in transferring AFBC technology to the power sector, but its attempt to pick a ‘winner’ in the bubbling design technology failed. The alternative circulating design technologies have proven far more effective and more popular in the US.

  • Applied R&D was very focused upon achieving technology breakthroughs that would drive down the operating cost of the technology.

  • Public-private funding of demonstration plants to test specific technology innovations and to scale up the technology to commercial capacity was crucial to its subsequent commercial adoption.

  • The support that PURPA offered smaller-scale cogeneration plant provided AFBC technology with a niche market that it was able to exploit.

  • Environmental regulations did not prove to be the that many originally thought they would be. In practice alternative technologies proved more cost-effective in addressing these environmental constraints.

  • Subsequent development of AFBC technology was not sufficient to achieve any competitive advantage over competing gas turbine and pulverised-coal technologies and AFBC remains a niche participant in the US market.

[1] Norberg-Bohm, V. & Bañales-López, S. (2002) ‘Public policy for energy technology innovation: A historical analysis of fluidized bed combustion development in the USA’, Energy Policy, 30(13): 1173-1180.

[2] Stratos Tavoulareas, E. and Charpentier, J-P. (1995) Clean Coal Technologies for Developing Countries, World Bank Technical Paper No. 286, World Bank, Washington.


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