The Development of a Combustion System for BW's Advanced Coal-Fired Low-Emission Boiler System

摘要

Advanced high efficiency, low emission coal-fired technologies are currently being applied in countries, such as Germany, Denmark, and Japan, where emission restrictions or high fuel costs have made them warranted. Most of the market growth, however, is expected to be in Asia and the Pacific Rim, where reliable, economical, and easily operated technologies are preferred. Emission limits in these markets are currently unchallenging, however, pressure from the world community is rapidly forcing stricter regulations, making advanced coal-fired technologies more desirable. In these foreign markets, the cost associated with these technologies is offset by government subsidy and higher cost-of-electricity, advantages not available to the U.S. supplier. Domestic spending on advanced technologies is declining, while legislative restrictions are increasing. Furthermore, the emission limits must be met without an increase in the cost-of-electricity.Though present emissions limits, domestic fuel costs, and legislation do not currently justify high efficiency or extremely low emissions technologies domestically, this is likely to change. To address the tighter regulations legislation is placing on boiler emissions, Babcock & Wilcox, under contract to the U.S. Department of Energy (DOE), has been leading a team in the development of an advanced coal-fired low-emission boiler system (LEBS). The project objective is to design a new pulverized coal (PC) powered generating system equipped with improved combustion and heat transfer subsystems and advanced environmental control technologies capable of achieving emissions of NO_X, SO_X, and particulates far below current New Source Performance Standards (NSPS).The objectives of the program are to achieve continuous NO_X emissions below 0.2 lb NOx/MBtu with a specified design coal, through combustion techniques only, with a further target of 0.1 lb NO_x/MBtu using supplementary advanced flue gas cleanup technologies if necessary. The SO_2 limit for the project has been set at 0.1 lb SO_2/MBtu, with a paniculate emission limit of 0.01 lb particulate/MBtu. The net plant efficiency is specified to be at least 42% (HHV), while overall the cost of electricity must not increase relative to a conventional plant meeting current NSPS. The B&W LEBS plant uses conventional state-of-the-art equipment along with developing new technologies to meet the program goals. To meet this goal, B&W has coupled advanced environmental control technologies capable of achieving emission of NO*, SO_x, and paniculate far below current NSPS with an advanced boiler equipped with improved combustion and heat transfer subsystems.Phase I of the LEBS program began with a thorough review and assessment of potential advanced technologies and techniques. Through engineering analysis, pilot-scale testing, and numerical modeling in Phases I and IL a near full-scale 100 MBtu/hr advanced NO_x emissions control system was designed, fabricated, and tested. Further experimental testing and numerical modeling has continued to refine the LEBS concept. This information has been incorporated into the design of a proof-of-concept (POC)demonstration facility and a commercial generating unit (CGU). The results of the development activities for the combustion system are presented in this paper.