Post-Combustion NOx Control for Fired Equipment in General Refinery Services API RECOMMENDED PRACTICE 536 SECOND EDITION, DECEMBER 2006 REAFFIRMED, SEPTEMBER 2013 `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale Post-Combustion NOx Control for Fired Equipment in General Refinery Services `,,```,,,,````-`-`,,`,,`,`,,` - Downstream Segment API RECOMMENDED PRACTICE 536 SECOND EDITION, DECEMBER 2006 REAFFIRMED, SEPTEMBER 2013 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale SPECIAL NOTES API publications necessarily address problems of a general nature With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights API publications may be used by anyone desiring to so Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict API publications are published to facilitate the broad availability of proven, sound engineering and operating practices These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard API does not represent, warrant, or guarantee that such products in fact conform to the applicable API standard All rights reserved No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C 20005 Copyright © 2006 American Petroleum Institute `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale FOREWORD Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent The following definitions apply: Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification Should: As used in a standard, “should” denotes a recommedation or that which is advised but not required in order to conform to the specification This document was produced under API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C 20005 Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years A one-time extension of up to two years may be added to this review cycle Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000 A catalog of API publications and materials is published annually and updated quarterly by API, 1220 L Street, N.W., Washington, D.C 20005 `,,```,,,,````-`-`,,`,,`,`,,` - Suggested revisions are invited and should be submitted to the Standards and Publications Department, API, 1220 L Street, NW, Washington, DC 20005, standards@api.org iii Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale CONTENTS Page SCOPE APPLICABLE ENVIRONMENTAL REGULATIONS AND REFERENCES 2.1 Environmental regulations .1 2.2 U.S Federal Regulations 2.3 Environmental Protection Agency (EPA) References 2.4 National Standards & Publications DEFINITIONS AND ABBREVIATIONS .2 3.1 Definitions 3.2 Abbreviations .3 3.3 Units of Emissions Measurements 4 PROCESSES DESCRIPTION, CONSIDERATIONS, AND APPLICATIONS 4.1 Selective Non-Catalytic Reduction (SNCR) .4 4.2 Selective Catalyctic Reduction 4.3 Process Considerations 4.4 Process Applications DESIGN CONSIDERATIONS 5.1 General 5.2 SNCR Systems Overview 12 5.3 SCR Systems Overview .13 5.4 Reactant Control and Dilution System Compoents 25 5.5 Reactant Injection System 26 5.6 Catalyst/Reactor .27 5.7 Structures and Appurtenances 27 5.8 Refractories and Insulation 28 5.9 Instrumentation and Electrical Systems 28 5.10 Induced Draft Fan (IDF) 28 5.11 Flue Gas Connections 28 OPERATIONAL CONSIDERATIONS .29 6.1 Selective Non-Catalytic Reduction 29 6.2 Selective Catalytic NOx Reduction 30 APPENDIX A APPENDIX B APPENDIX C APPENDIX D APPENDIX E `,,```,,,,````-`-`,,`,,`,`,,` - Figures Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS POST–COMBUSTION NOX CONTROL DATA SHEETS 35 CALCULATION METHOD FOR CORRECTING NOX MEASUREMENT 51 FLOW MODELING CONSIDERATIONS 53 SCR OPERATIONS AND MAINTENANCE CONSIDERATIONS 55 DESIGN CONDITIONS AFFECTED BY FLUE GAS QUALITY 57 Temperature Ranges for SCR Catalysts—Typical Examples SNCR System Schematics Aqueous Ammonia 15 SNCR System Schematics Anhydrous Ammonia 17 SNCR System Schematics Urea Injection 19 SCR System Schematics Aqueous Ammonia 21 v Not for Resale Page 10 Tables E.1 SCR System Schematics Anhdrous Ammonia Condensation Temperature of Ammonium Sulfate and Ammonium Bisulfate for Various Conceptrations of NH3 and SO3 Catalyst Activity Profile versus Time Effect of Space Velocity on NOx Reduction Efficiency Typical NOx Reduction Efficiency and Ammonia Slip 30 31 32 33 Comparison of Typical SNCR and SCR Systems SNCR Design Considerations—New Units and Retrofit Units 10 SCR Design Consideration—New Units and Retrofit Units 11 Catalyst Degradation Sources and Mechanisms 58 `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS 23 Not for Resale Post-Combustion NOx Control for Fired Equipment in General Refinery Services Scope 1.1 This recommended practice covers the mechanical description, operation, maintenance, and test procedures of post-combustion NOx control equipment for fired equipment in general refinery service It does not cover reduced NOx formation through combustion design techniques, such as flue gas recirculation (FGR) and staged combustion 1.2 This document covers two of the methods of post combustion NOx reduction: a Selective Non-Catalytic Reduction (SNCR) b Selective Catalytic Reduction (SCR) 1.3 SNCR is a process where the addition of ammonia or urea into the flue gas stream causes the oxides of nitrogen to convert to nitrogen and water vapor The basis for the selection and limitations of the SNCR systems are described in 4.1 1.4 SCR is a process where the addition of ammonia into the flue gas stream in the presence of a suitable catalyst causes the oxides of nitrogen to convert to nitrogen and water vapor The basis for the selection of the various catalyst types are described in 4.2 1.5 Table indicates the typical operating performance and limitations of both types of NOx reduction systems The reduction efficiency of SNCR is limited because of the flue gas temperature range and difficulty in achieving proper mixing of the reactants, but is often suitable for retrofitting existing equipment for low or moderate NOx reduction SCR systems operate at high reduction efficiency at a lower temperature window than an SNCR system and are usually selected for lowest NOx emission Design Criteria NOx Reduction Efficiency Temperature Window Reactant Reactor Waste Disposal Thermal Efficiency Debit Energy Consumption Capital Investment Costs Plot Requirements Maintenance Ammonia/NOx (Molar Ratio) Urea/NOx (Molar Ratio) Ammonia Slip—corrected to appropriate reference O2 value Retrofit Additional Mechanical Draft SNCR 40% – 75% 870ºC – 1370ºC (1600ºF – 2500ºF) Ammonia or urea None None 0% – 0.3% Low Low Low Low 1.0 – 1.5 0.5 – 0.75 – 20 ppmvd SCR 60% – 95% 125ºC – 580ºC (260ºF – 1075ºF) Ammonia Catalytic Spent catalyst 0% Higher if fan is used High Higher in most cases Medium to high – years (typical guaranteed catalyst life) 0.8 – 1.2 Not applicable – ppmvd Less complicated Not required May be complicated Required in most cases Applicable Environmental Regulations and References 2.1 ENVIRONMENTAL REGULATIONS a Local b State c Federal Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Table 1—Comparison of Typical SNCR and SCR Systems API RECOMMENDED PRACTICE 536 2.2 U.S FEDERAL REGULATIONS a Clean Air Act b Code of Federal Regulations (CFR) 2.3 ENVIRONMENTAL PROTECTION AGENCY (EPA) REFERENCES a New Source Performance Standards 40 CFR 60 Subpart Db, Industrial Commercial—Institutional Steam Generating Units b Alternative Control Techniques Documents 1993 NOx Emissions from Process Heaters c National Ambient Air Quality Standards 2.4 NATIONAL STANDARDS & PUBLICATIONS API Std 560 Publ 534 Publ 535 Fired Heaters for General Refinery Service Heat Recovery Steam Generators Burners for Fired Heaters in General Refinery Services ANSI1 K61.1 Safety Requirements for the Storage and Handling of Anhydrous Ammonia ASME2 Section VIII B 31.3 Boiler & Pressure Vessel Code Chemical Plant & Petroleum Refinery Piping Definitions and Abbreviations 3.1 DEFINITIONS 3.1.1 ammonia breakthrough: The point at which increasing the NH3/NOx molar ratio does not significantly reduce the amount of NOx 3.1.2 ammonia/NOx ratio: The molar ratio of injected ammonia to the inlet NOx in the flue gas stream 3.1.4 ammonium bisulfate and ammonium sulfate: Compounds formed when ammonia or urea injected into a flue gas stream combine with sulfur trioxide These compounds may foul heat transfer surface and increase particulate emissions 3.1.5 catalyst activity: Measurement of the NOx reduction performance 3.1.6 catalyst handling facilities: Device used for loading and unloading of catalyst modules, usually a monorail and hoist 3.1.7 catalyst matrix or substrate: Substance that is coated or impregnated by the active ingredients of the catalyst The catalyst matrix can be made from ceramic honeycomb, pellets, metal plates or mesh 3.1.8 catalyst module: Catalyst elements that are shop assembled for installation into an SCR catalyst housing Module consists of a steel frame with suitable lifting lugs for installation and removal of the modules into SCR catalyst housing A catalyst layer consists of catalyst modules that cover the entire cross-section flow area 3.1.9 catalyst poisoning: Degradation of NOx reduction activity when flue gas component is adsorbed on the active surfaces of the catalyst and renders it inactive 3.1.10 catalyst space velocity: The quantity of flue gas (at standard conditions) flowing per volume of catalyst per hour 3.1.11 catalyst support: Structure within the reactor housing to support the catalyst modules 3.1.12 catalyst type: Category of catalyst denoted by the active ingredient, namely vanadium oxide, titanium oxide, platinum, or zeolite 1American National Standards Institute, 25 West 43rd Street, 4th floor, New York, New York, 10036, www.ansi.org 2ASME International, 9636 Kinsman Road, Materials Park, Ohio, 44073, www.asminternational.org Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - 3.1.3 ammonia slip: The amount of unreacted ammonia in the flue gas stream after the reduction of the NOx, measured in ppmvd corrected to the standard oxygen level POST-COMBUSTION NOX CONTROL FOR FIRED EQUIPMENT IN GENERAL REFINERY SERVICES -2%12 3267&20%867,2112[&21752/ $3,53 6(/(&7,9(121&$7$/