Post-combustion NOx Control

for Fired Equipment in General Refinery and Petrochemical Services

API STANDARD 536

THIRD EDITION, SEPTEMBER 2017

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Copyright © 2017 American Petroleum Institute

Foreword

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iii

Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions, and Abbreviations 3

   1. Definitions 3

   2. Abbreviations 6

4. Proposals and Documentation 7

   1. Purchaser's Responsibilities 7

   2. Vendor's Responsibilities 8

   3. Documentation 9

   4. Performance Tests and Guarantees 11

   5. Final Records 12

5. Design Requirements 13

   1. Process Design 13

   2. System Design 13

   3. Mechanical Definition 15

   4. Post-combustion NOx Treatment System 15

   5. Ammonia Flow Control Unit (AFCU) 16

   6. Direct Reactant Injection System (DRIS) 17

   7. Reactant Injection System (RIS) 17

   8. Reactant Control System 17

   9. Piping and Skids 17

   10. Urea Handling and Preparation 17

   11. Ammonia Vaporizer/Mixer 18

   12. Reactant Storage 18

   13. SCR Catalyst and Reactor Housing 19

   14. Structures and Appurtenances 19

   15. Refractories and Insulation 20

   16. Instrumentation and Electrical Systems 21

   17. Induced Draft Fan and Dilution Air Blowers 21

   18. Flue Gas Connections 21

   19. NOx Analyzers 22

6. Fabrication and Shop Assembly 22

   1. General 22

   2. Structural-steel Fabrication 22

   3. Control Skids 23

   4. Refractory and Insulation 25

   5. Dilution Air Blowers 25

7. Inspection and Testing 25

   1. General 25

   2. Catalyst 26

   3. Mechanical Components 27

   4. Electrical Components 27

   5. Structural 28

   6. Piping 28

   7. Refractory 28

   8. Acceptance Testing 28

      v

      Contents

      Page

8. Storage, Handling, Identification, and Shipping 29

9. Field Installation and Erection 30

   1. General 30

   2. Catalyst 30

Annex A (informative) Post-Combustion NOx Control Process Selection and Application 31

Annex B (informative) Selective Non-catalytic Reduction (SNCR) 33

Annex C (informative) Selective Catalytic Reduction (SCR) 36

Annex D (informative) Reactant Storage, Distribution, Control, and Injection Systems 40

Annex E (informative) General Design Considerations 61

Annex F (informative) Post-combustion NOx Control Datasheets 63

Annex G (informative) Operational Considerations 78

Annex H (informative) Calculation Method for Correcting NOx Measurements 86

Annex I (informative) Flow Modeling Considerations 88

Annex J (informative) SCR Operations, Inspection, and Maintenance Considerations 92

Annex K (informative) Design Considerations Affected By Flue Gas Quality and Particulates 96

Annex L (informative) Units of Emission Measurement 99

Annex M (informative) Proposed Shop Assembly Conditions 100

Annex N (informative) Post-combustion NOx Control Checklist 102

Bibliography 107

Figures

1. Comparison of Typical SNCR and SCR Systems 34

2. SNCR Effect of Residence Time 34

C.1 Typical Operating Temperature Ranges for SCR Catalysts 37

1. SNCR Aqueous Ammonia System Schematic 54

2. SNCR Anhydrous Ammonia System Schematic 55

3. SNCR Urea System Schematic 56

4. SCR Aqueous Ammonia System Schematic 57

5. SCR Anhydrous Ammonia System Schematic 58

6. Aqueous Ammonia Storage System 59

7. Anhydrous Ammonia Storage System 60

1. Ammonium Sulfate and Ammonium Bisulfate Precipitation Temperature Downstream of SCR 79

2. Typical NOx Reduction Efficiency and Ammonia Slip 83

Tables

A.1 Comparison of Typical SNCR and SCR Systems 32

B.1 SNCR Design Considerations for New and Retrofit Units 35

C.1 SCR Design Considerations-New Units and Retrofit Units 39

G.1 Flue Gas Temperature Operation 82

K.1 Catalyst Degradation Sources and Mechanisms 97

N.1 Checklist for Post-combustion NOx Control Equipment 103

vi

Introduction

Post-combustion NOx control systems reduce levels of NOx emissions by converting the NOx formed during the combustion process to nitrogen (N2) gas. The chemical reactions required to convert the NOx to N2 for the systems described in this standard are applied downstream of the combustion zone. These techniques introduce a reactant into the flue gas stream to react with the NOx. The reaction may be completed with or without the use of catalyst.

It may be necessary to combine more than one method of post-combustion control to achieve the desired level of NOx reduction.

The application of any NOx reduction technique and control technology is most often in compliance with an environmental regulation requirement, which include both instantaneous and time averaged performance criteria. Reliable and effective performance of the NOx control systems and related mechanical systems and components are critical in meeting regulatory requirements and environmentally responsible operation.

The fundamental elements that are required in order to provide the expected reliability and performance requirements for post-combustion NOx control systems specified and supplied through the use of this standard include the following:

• process definition;

  
  

• process performance expectations;

  
  

• system design selection;

  
  

• mechanical definition of systems and components.

The selected post-combustion NOx control systems and equipment should be capable of the specified performance for a design period for the run length specified in the data sheets without the need for an unplanned outage of the post-combustion NOx treatment control systems and equipment or the associated combustion equipment.

For new designs, the type of post-combustion NOx control system design selections and mechanical definition can be advanced using the requirements, guidance and recognized good industry practice that are identified in this document.

Users of this Standard should be aware that further or differing requirements may be needed for individual applications. This Standard is not intended to inhibit a vendor from offering, or the purchaser from accepting, alternative equipment or engineering solutions for the individual application. This may be particularly applicable where there is innovative or developing technology. Where an alternative is offered, the vendor should identify any variations from this standard and provide details.

In this Standard, the SI system of units is used. Where practical in this Standard, U.S. Customary units are included in brackets for information.

A bullet () at the beginning of a clause or sub-clause indicates that either a decision is required or further information is to be provided by the purchaser. This information should be indicated on data sheets (see examples in Annex N) or stated in the inquiry or purchase order.

Post-combustion NOx Control for Fired Equipment in General Refinery and Petrochemical Services

1. Scope

   
   

   This standard specifies requirements and provides guidance for the selection, design specification, mechanical description, operation, maintenance, and test procedures for post-combustion NOx control equipment and related mechanical systems and components used for fired equipment in petrochemical and general refinery service.

   
   

   This document covers the following methods of post-combustion NOx reduction for both new and retrofit applications:

   
   

   • Selective Non-catalytic Reduction (SNCR), and

     
     

   • Selective Catalytic Reduction (SCR).

     
     

     This standard is primarily intended for direct application to fired process heaters, reformers, and industrial and power boilers used in petrochemical and general refinery services. The same fundamental NOx control technologies and systems may also be applied to Fluid Catalytic Cracking Units (FCCUs), incinerators, gas turbine exhaust, and other exhaust gas process systems; however, SCRs may require additional considerations beyond the scope of this standard to address unique aspects, such as high particulate content and corrosive chemicals, in the flue gas stream.

     
     

     This document does not cover:

     
     

   • reduced NOx formation through combustion controls and design techniques such as low-NOx burners, flue gas recirculation (FGR), and staged combustion; or

     
     

   • non-selective catalytic reduction (NSCR) for the control of NOx and other pollutant emissions.

   
   

   For further guidance on post-combustion NOx control process selection and the application of SNCR and SCR systems, refer to Annex A.

   
   

   For further guidance on the process description of SNCR and SCR technologies and systems, refer to Annex B and Annex C, respectively.

   
   

   For further guidance on reactant storage, distribution, control, and injection systems, and general design considerations, including purchaser decisions for SNCR and SCR systems, refer to Annex D and Annex E, respectively.

   
   

2. Normative References

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API Standard 560, Fired Heaters for General Refinery Service

API Standard 620, Design and Construction of Large, Welded, Low-pressure Storage Tanks

1

2 API STANDARD 536

AISC Steel Construction Manual1

AMCA 801:20012, Industrial Process/Power Generation Fans — Specifications and Guidelines

ANSI/ISA-5.13; Instrumentation Symbols and Identification

ANSI/ISA-77.82.01; Selective Catalytic Reduction (SCR) Control Systems

ASME Boiler and Pressure Vessel Code (BPVC), Section VIII: Rules for Construction of Pressure Vessels; Division 14

ASME B31.3, Process Piping

ASTM A1235, Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products

ASTM A143, Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement

ASTM A153, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware

ASTM A384, Standard Practice for Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies

ASTM B633, Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel

AWS D1.1/D1.1M6, Structural Welding Code — Steel

AWS D14.6/D14.6M, Specification for Welding of Rotating Elements of Equipment

CGA G-2.1/ANSI K61.17, American National Standard Safety Requirements for the Storage and Handling of Anhydrous Ammonia

EN 134808 (all parts), Metallic industrial piping

International Building Code (IBC)9

1. American Institute of Steel Construction, One East Wacker Drive, Suite 700, Chicago, Illinois 60601-1802, www.aisc.org.

2. Air Movement and Control Association International, Inc., 30 W. University Drive, Arlington Heights, Illinois 60004, www.amca.org.

3. The International Society of Automation 67 T.W. Alexander Drive, P.O. Box 12277, Research Triangle Park, North Carolina 27709, www.isa.org.

4. ASME International, 2 Park Avenue, New York, New York 10016-5990, www.asme.org.

5. ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org.

6. American Welding Society, 8669 NW 36 Street, #130, Miami, Florida 33166-6672, www.aws.org.

7. Compressed Gas Association, 14501 George Carter Way #103, Chantilly, Virginia 20151, www.cganet.com.

8. European Committee for Standardization, Avenue Marnix 17, B-1000 Brussels, Belgium, www.cen.eu.

9. International Code Council, 500 New Jersey Avenue, NW, 6th Floor, Washington, D.C. 20001, www.iccsafe.org.

POST-COMBUSTION NOX CONTROL FOR FIRED EQUIPMENT IN GENERAL REFINERY AND PETROCHEMICAL SERVICES 3

ISO 1461 10 Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods

ISO 8501-1, Preparation of steel substrates before application of paints and related products — Visual assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous coatings

ISO 10684, Fasteners — Hot dip galvanized coatings National Board Inspection Code Data Reports11 NFPA 7012, National Electrical Code

SSPC SP 613/NACE No. 3, Joint Surface Preparation Standard: Commercial Blast Cleaning

40 CFR Part 60 14 ; United States Code of Federal Regulations – Standards of Performance for New Stationary Sources

UL15, Underwriters Laboratories, Inc.

3 Terms, Definitions, and Abbreviations

3.1 Definitions

For the purposes of this document, the following terms and definitions apply.

3.1.1

ammonium bisulfate ammonium sulfate

Compounds formed when ammonia from ammonia or urea injection into a flue gas stream combine with sulfur trioxide. These compounds may foul heat transfer surface, deactivate the catalyst, and increase particulate emissions.

3.1.2

ammonia breakthrough

The point at which increasing the NH3/NOx molar ratio does not significantly reduce the amount of NOx.

3.1.3

ammonia flow control unit (AFCU)

A unit, typically skid mounted, that is used to vaporize ammonia, pump air, and mix the ammonia and air prior to being sent to the ammonia injection grid (AIG). The AFCU is also known as the reactant control and dilution system (RCDS).

3.1.4

Ammonia/NOx ratio

The molar ratio of injected ammonia to the inlet NOx in the flue gas stream.

1. International Organization for Standardization, 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, www.iso.org.

2. The National Board of Boiler and Pressure Vessel Inspectors, 1055 Crupper Avenue, Columbus, OH 43229, www.nationalboard.org.

3. National Fire Protection Association, 1 Batterymarch Park, Quincy, Massachusetts, 02169-7471, www.nfpa.org.

4. The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, Pennsylvania 15222, www.sspc.org.

5. U.S. National Archives and Records Administration, 700 Pennsylvania Avenue, NW, Washington, DC 20408, www.archives.gov.

6. UL LLC, 333 Pfingsten Road, Northbrook, Ilinois 60062 USA. www.ul.com.