Guide to Low-Emission Boiler and Combustion Equipment Selection PDF Print E-mail
Written by C. B. Oland   
Tuesday, 08 June 2010 14:51

Guide to Low-Emission Boiler and Combustion Equipment Selection

C. B. Oland

NOTE: This is a summary of information provided in the 172-page document available from the USDOE.


Boiler owners and operators who need additional generating capacity face a number of legal, political, environmental, economic, and technical challenges. Their key to success requires selection of an adequately sized low-emission boiler and combustion equipment that can be operated in compliance with emission standards established by state and federal regulatory agencies.

Recognizing that many issues are involved in making informed selection decisions, the U.S. Department of Energy (DOE), Office of Industrial Technologies (OIT) sponsored efforts at the Oak Ridge National Laboratory (ORNL) to develop a guide for use in choosing low-emission boilers and combustion equipment. To ensure that the guide covers a broad range of technical and regulatory issues of particular interest to the commercial boiler industry, the guide was developed in cooperation with the American Boiler Manufacturers Association (ABMA), the Council of Industrial Boiler Owners (CIBO), and the U.S. Environmental Protection Agency (EPA).

The guide presents topics pertaining to industrial, commercial, and institutional (ICI) boilers. Background information about various types of commercially available boilers is provided along with discussions about the fuels that they burn and the emissions that they produce. Also included are discussions about emissions standards and compliance issues, technical details related to emissions control techniques, and other important selection considerations. Although information in the guide is primarily applicable to new ICI boilers, it may also apply to existing boiler installations.

Use of the guide is primarily intended for those involved in either expanding current steam or hot water generating capacity or developing new capacity. Potential users include owners, operators, plant managers, and design engineers who are involved in selecting low-emission boilers and combustion equipment that comply with established emissions requirements. Regulatory authorities who deal with emission issues and boiler permit applications may also find useful information in the guide.

The guide is organized into topics that address many of the fundamental concerns encountered in planning a new steam or hot water boiler system. An overview of boilers, fuel feed systems, fuels, and emissions, which are fundamental considerations in the planning process, is presented in the first part of the guide. Discussions about firetube, watertube, cast iron, and tubeless boilers that burn fossil or non- fossil fuels are presented in Chap. 2. Technical terms and emission control techniques introduced in the overview provide a foundation for following discussions.

Issues pertaining to solid, liquid, and gaseous fuels commonly fired in ICI boilers are presented in the first part of Chap. 3. Characteristics of fossil and nonfossil fuels are included with emphasis on coal, oil, natural gas, biomass, and refuse-derived fuels (RDFs). For completeness, other materials such as heavy residuals from petroleum-cracking processes, coal tar pitch, and pulp mill sludge, which are sometimes used as boiler fuel, are briefly described. Following the fuel discussions, emphasis shifts to solid and gaseous emissions that are regulated under the Clean Air Act (CAA). The four principle emissions from combustion boilers that are regulated under this act include nitrogen oxides (NOx), sulfur dioxide (SO2), particulate matter (PM), and carbon monoxide (CO). Mechanisms by which these emissions are formed are briefly described as an aid in understanding the various control techniques for reducing emissions.

The legal basis for regulating emissions from combustion boilers is contained in the CAA. This piece of environmental legislation addresses concerns about ground-level ozone, the accumulation of fine particles in the atmosphere, and acid rain. It also authorizes EPA to establish performance-based emissions standards for certain air pollutants including NOx, SO2, PM, and CO. A summary of emission limitations that are applicable to combustion boilers is presented in Appendix A. These limitations are specified as (1) maximum emission rates or (2) required reductions in potential combustion concentrations. Although the mandated emission limitations are a function of boiler type and size, the amount of each emission that may be released is strongly influenced by the type of fuel or fuel mixture being burned, the method of combustion, and the geographical location of the installation. In addition to discussions about the CAA, other topics covered in Chap. 4 include information sources, permitting issues, and lessons learned.

Techniques that are effective in reducing NOx, SO2, and PM emissions are subdivided into three general categories, depending on which stage in the combustion process they are applied. The categories include precombustion, combustion, and postcombustion emission control techniques. Table ES.1 shows the various techniques that may be applied to reduce these emissions. Descriptions of each technique are presented in Chap. 5.

As an aid in boiler and combustion equipment selection, emission control options for 14 of the most popular boiler and fuel combinations are identified and discussed in Chap. 6. These options reflect combustion of coal, fuel oil, natural gas, biomass, and RDF in watertube and firetube boilers. Figure ES.1 presents the general format used to identify the various emission control options that are available for a particular boiler and fuel combination. Use of information presented in the tables will help ensure that the best available control technologies are identified.

Although many factors must be considered when selecting a low-emission boiler and combustion equipment, the final choice should not be made until the performance of the complete system is evaluated and understood. Evaluations of different emission control equipment arranged in various configurations are technically complex. However, results of these evaluations are now an essential element of the permitting process. Details of the evaluations often establish the technical basis for permit applications submitted to regulatory authorities as part of the permitting process. Unless these evaluations are accurate and complete and unless currently accepted techniques for controlling emissions are adequately taken into consideration, it is unlikely that the regulatory authority will act favorably on the application. Information presented in this guide is intended to help owners and operators prepare permit applications that address the principal concerns and legal requirements of the regulatory authority.

Prepared for the U.S. Department of Energy Office of Industrial Technologies

Prepared by OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee 37831 managed by UT-BATTELLE, LLC for the U.S. DEPARTMENT OF ENERGY under contract DE-AC05-00OR22725


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