Assessing the Changes Required by the Industrial Boiler MACT Regulations

Transcription

1 Technical Paper MS-17 Assessing the Changes Required by the Industrial Boiler MACT Regulations Authors: A.L. LeClair L.M. McDermitt Babcock & Wilcox Power Generation Group, Inc. Barberton, Ohio, U.S.A Date: March 2014 Location: Barberton, Ohio

2 Abstract Assessing the Changes Required by the Industrial Boiler MACT Regulations A.L. LeClair and L.M. McDermitt Babcock & Wilcox Power Generation Group, Inc. Barberton, Ohio, USA In December 2012, the U.S. Environmental Protection Agency (EPA) published final limits to control air pollutant emissions from existing and new industrial boilers (IB) and process heaters, commercial and industrial solid waste incinerators, and sewage sludge incinerators under the maximum achievable control technology (MACT) standards. This paper focuses on the IB MACT requirements and emissions control solutions for existing units firing solid fuels. Industrial Boiler MACT The maximum achievable control technology (MACT) standards were developed by the EPA to reduce the effects of hazardous air pollutants (HAPs). The MACT standards do not necessarily require large, costly equipment; processes, methods, or techniques to control to the specific emissions limits may be employed. The limits are based upon the performance of the emissions levels already achieved by the best-performing similar facilities. The final December 2012 published values can be found in Tables 1 (existing units) and 2 (new units). The MACT standards are regulated under the National Emission Standards for Hazardous Pollutants (NESHAP) that requires the control of 187 HAPs. Four (4) major HAPs, including three (3) surrogates, include carbon monoxide (surrogate for organics), particulate matter (surrogate for metals), hydrogen chloride (surrogate for acid gases) and mercury. The emission requirements apply to the following: Major sources that emit 10 tons per year of a single HAP or 25 tons per year of combined HAPs Coal/biomass/liquid/process gas-fired boilers and fired heaters Fossil fuel-fired boilers up to 25 MWe Utility boilers firing non-fossil fuel that is not a solid waste Subcategory Table MACT Emissions Limits for Existing Units CEMS 3% O 2 ) Particulate Matter Hydrogen Chloride Mercury (lb/10 12 Btu) Coal Stoker Coal Fluidized Bed Pulverized Coal Biomass Stoker Wet Biomass Stoker Kiln Dried Biomass Fluidized Bed Biomass Dutch Oven/Pile Biomass Suspension Burner Biomass Fuel Cells Hybrid Biomass Suspension/Grate Light Oil Heavy Oil Gas 2 (Other Process Gases)

3 Subcategory Table MACT Emissions Limits for New Units CEMS 3% O 2 ) Particulate Matter Hydrogen Chloride Mercury (lb/10 12 Btu) Coal Stoker Coal Fluidized Bed Pulverized Coal Biomass Stoker Wet Biomass Stoker Kiln Dried Biomass Fluidized Bed Biomass Dutch Oven/Pile Biomass Suspension Burner Biomass Fuel Cells Hybrid Biomass Suspension/Grate Light Oil Heavy Oil Gas 2 (Other Process Gases) Different fuels require different regulations. The annual percent heat input of a specific fuel will determine the subcategory for the emission requirements. Table 3 lists the percentages and which fuel sets the subcategory. Natural gas-fired units do not currently have to comply with MACT. Table 3 Fuel Regulation If fuel fired (on an annual heat input basis): Fuel Subcategory >10% Coal and <10% Biomass Coal >10% Biomass and <10% Coal Biomass >10% Liquid and <10% Solid Liquid >10% Gaseous and <10% Liquid or Solid Gaseous Emissions Control Technologies for Existing Units It is recommended that any approach to achieving MACT compliance use a system solution which includes consideration of the fuel, boiler, a range of air quality control system (AQCS) equipment, continuous emissions monitoring systems (CEMS), and reporting. The large volume of environmental legislation in the pipeline requires early planning. Fuel Switching By changing or adding fuel capabilities, emissions generation can be reduced. Low NO x (nitrogen oxides) natural gas burners can add the firing capability, while producing lower NO x and CO than biomass alone. This allows more emissions flexibility. By firing greater than 10% biomass fuel on an annual heat input basis, a coal unit can be classified as a biomass unit which has higher allowable emissions limits. 2

4 (CO) Strategies Reducing CO emissions requires extensive knowledge of and experience with biomass and auxiliary fuel combustion systems. Managing air and fuel flow to make the system work is important to the performance of the system. Babcock & Wilcox Power Generation Group, Inc. s (B&W PGG) approach focuses on integrating the components. Table 4 shows one strategy for CO compliance depending on combustion type of the boiler. Table 4 CO Compliance Strategy for Existing Units Existing Technology Grate Fired Pulverized Coal Fired Bubbling Fluid Bed (BFB) Modifications Upgrade air system Convert to vibrating grate Convert to BFB Pulverizer upgrades and maintenance Install high energy burners NO x increase Add SNCR or SCR to maintain NO x compliance Upgrade air system Operate with higher O 2 Process Gas Fired Operate with higher O 2 High energy burners B&W PGG s air system controls CO by automatically adjusting air port dampers according to fuel supply rates, thus allowing for more complete combustion. By using B&W PGG s COMO SM numerical modeling system, a general-purpose flow and combustion code, the overfire air and combustion patterns are modeled and optimized to maintain the most complete combustion possible, reducing the generated emissions. Particulate Matter (PM) Strategies B&W PGG offers a number of proven particulate control technologies for a variety of industrial processes, including Pulseflo fabric filter (FF) baghouses, and wet or dry electrostatic precipitators (ESP). All of these particulate control equipment options utilize the latest technology advancements. Table 5 shows a strategy for PM compliance depending on the existing control equipment. Table 5 PM Compliance Strategy for Existing Units Existing Technology Multiclone Particle Separators Only Wet Particulate Scrubber Electrostatic Precipitator Modifications Add dry ESP or PulsefloFF Internal replacement Add wet ESP downstream of wet scrubber Replace with dry ESP or Pulseflo FF Change fuel if difficult ash Enhance ESP performance o Add flue gas conditioning o Modify ESP Replace ESP with Pulseflo FF Add series Pulseflo FF downstream of ESP 3

5 Acid Gas Strategies Integrating a Pulseflo fabric filter with dry sorbent injection (DSI) and wet flue gas desulfurization (FGD) technologies also provides low HAP emissions in a variety of applications. A wet ESP provides the lowest overall emissions of fine particulate and acid mist. Table 6 shows a strategy, depending on the existing control equipment, for acid gas compliance, using HCl as the surrogate. Table 6 HCl Compliance Strategy for Existing Units Existing Technology Multiclone Particle Separators Only Wet Particulate Scrubber Electrostatic Precipitator Modifications Change fuel Add DSI o Add dry ESP or Pulseflo FF May be suitable o Add caustic to washwater if needed Add DSI o ESP performance may deteriorate Enhance ESP performance o Add flue gas conditioning o Modify ESP Replace ESP with Pulseflo FF Mercury (Hg) Strategies The easiest way to decrease Hg is to change to a fuel with lower mercury content. If this is not possible, there are several systems that could be added to the boiler or onto the AQCS, such as a powdered activated carbon (PAC) injection system, a chemical halogen injection (CHI) system, or B&W PGG s Absorption Plus (Hg) wet FGD re-emission additive. Conclusion There are no universal solutions to meet the IB MACT emissions standards. Each plant is unique with its own existing AQCS configuration, available space and age of equipment. There may also be state and local regulations that are more stringent than the federal MACT compliance limits. The main goal is to achieve the desired performance limits and minimize overall cost or, if possible, obtain the greatest return on the initial capital expenditure. B&W PGG can offer specialized compliance strategies and provide the necessary blend of regulatory and expertise to engineer, procure, and erect all elements of your boiler MACT compliance project objectives in the most cost-effective approach. B&W PGG will work closely with the customer to select the best option. Copyright 2014 by Babcock & Wilcox Power Generation Group, Inc. All rights reserved. No part of this work may be published, translated or reproduced in any form or by any means, or incorporated into any information retrieval system, without the written permission of the copyright holder. Permission 4

6 requests should be addressed to: Marketing Communications, Babcock & Wilcox Power Generation Group, P.O. Box 351, Barberton, Ohio, U.S.A Or, contact us from our Web site at Disclaimer Although the information presented in this work is believed to be reliable, this work is published with the understanding that Babcock & Wilcox Power Generation Group, Inc. (B&W PGG) and the authors and contributors to this work are supplying general information and are not attempting to render or provide engineering or professional services. Neither B&W PGG nor any of its employees make any warranty, guarantee or representation, whether expressed or implied, with respect to the accuracy, completeness or usefulness of any information, product, process, method or apparatus discussed in this work, including warranties of merchantability and fitness for a particular or intended purpose. Neither B&W PGG nor any of its officers, directors or employees shall be liable for any losses or damages with respect to or resulting from the use of, or the inability to use, any information, product, process, method or apparatus discussed in this work. Works Cited Erlewine, T. (2011). Unit Heat Balance Test Final Report. Brush: Xcel Energy. Kosik, M. (2012). Baseline Test Report. Barberton: B&W. 5