Burners for Fired Heaters in General Refinery Services

API RECOMMENDED PRACTICE 535 THIRD EDITION, MAY 2014

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iii

Contents

Page

1. Scope 1

2. Normative References 1

3. Terms and Definitions 1

4. Mechanical Components for Burners 9

   1. General 9

   2. Pilots and Igniters 9

   3. Major Burner Components 16

5. Environmental Considerations 22

   1. General 22

   2. Noise 22

   3. Flue Gas Emissions 22

6. Burner Selection 26

   1. General 26

   2. Draft 26

   3. Flame Stability 28

   4. Design Excess Air 28

   5. Combustion Air Preheat 29

   6. Turbine Exhaust Gas 29

   7. Combustion Air Adjustment. 29

7. Gas Firing 30

   1. Raw Gas Firing (Nozzle Mix) 30

   2. Premix Firing 32

8. Liquid Fuel Firing. 33

   1. Types of Fuel Oil 33

   2. Atomization 34

   3. Fuel Physical Properties 36

   4. Liquid Fuel Turndown 38

   5. Design Excess Air Recommendations 39

   6. Flame Characteristics 39

   7. Burner Heat Release 39

   8. Combination Firing 39

9. Low NOx Burners 40

   1. General 40

   2. NOx Formation Chemistry 40

   3. Approximate Method to Convert NOx Measurement in ppmvd to lb/MBtu (HHV) 40

   4. Low NOx Burner Development 41

   5. Staged Air Burners 42

   6. Staged Fuel Burners 43

   7. Flue Gas Recirculation 44

   8. Alternate Methods for Reducing Combustion Generated NOx 45

   9. Other Design Considerations 46

      v

      Contents

      Page

   10. Fuel Treatment 49

   11. Retrofit Considerations. 49

10. Burner Operation 52

    1. General 52

    2. Excess Air Controls 52

11. Maintenance 56

    1. Shipping 56

    2. Burner Parts Inspection 56

    3. Installation and Initial Setup 56

    4. Post-installation Checkout 57

    5. Maintenance Program 57

12. Testing 59

    1. General 59

    2. Test Requirements 59

    3. Test Fuels 60

    4. Air Supply 61

    5. Pilot and Igniters 61

    6. Main Burner Test 62

    7. Test Instrumentation 66

    8. Measurements 66

13. Troubleshooting 67

    1. Burner Plugging 67

    2. Troubleshooting Gas Fired Low NOx Burners 70

    3. Burner Operation Troubleshooting Table 70

14. Considerations for Safe Operation 70

    1. General 70

    2. Flooding 73

    3. Afterburning 75

    4. Insufficient Draft 75

    5. Fuel Leak in Burner Riser 76

    6. Liquid in Fuel Gas Line to Burners 76

    7. Debris in Fuel Gas Lines 76

    8. Oil Atomization Issues 76

Annex A (informative) Burner Datasheets 77

Bibliography 84

Figures

1. Raw Gas Burner 10

2. Premix Gas Burner 11

3. Radiant Wall Burner 12

4. Combination Oil and Gas Burner 13

5. Low NOx Staged Air Combination Oil and Gas Burner 14

   vi

   Contents

   Page

6. Low NOx Staged Fuel Gas Burner 15

7. Effect of Excess Air on NOx Emissions 23

8. Effect of Combustion Air Temperature on NOx Emissions 23

9. Effect of the Firebox Temperature on NOx Production 24

10. Effect of Hydrogen Content of Fuel Gas on NOx Emission 25

11. Effect of Fuel Nitrogen Content on NOx Emission 25

12. Inside Mix Atomizer 35

13. Port Mix or Steam Assist Atomizer 36

14. Approximate Conversion Factor from Btu × 106/hr to ppmv (3 % O2, Dry Basis), Based on

    Typical Refinery Fuel Gas 41

15. Staged Air Burner (Typical) 43

16. Staged Fuel Burner (Typical) 44

17. Example of One Type of Internal Flue Gas Recirculation Burner 45

18. Burner-to-furnace Interaction 47

19. Natural Draft Heater Adjustment Flow Chart 53

20. Typical Draft Profile in a Natural Draft Heater 55

21. Typical Burner Test Setup 68

Tables

1. Clarification Table Comparing Definitions in API 560 and API 535 9

2. Air Register Characteristic 17

3. Fuel Gas Burner Components 19

4. Fuel Oil Burner Components 19

5. Burning Housing 20

6. Burner Tile 20

7. Effects of Reduced Excess Air on Burner Emissions 29

8. Typical Excess Air on Raw Gas Burners 31

9. Typical Excess Air on Premix Burners 33

10. Recommended Viscosity for Typical Fuel Oil Atomizers 37

11. Typical Turndown of Liquid Fuel Atomizers 38

12. Typical Excess Air for Liquid Fuels 39

13. Typical NOx Emissions for Gas Firing 42

14. Typical NOx Emissions for Oil Firing 42

15. Optimum Excess Air Levels 53

16. Minimum Recommended Test Procedure to Verify Burner Operating Envelope and Emissions

    for Burners 64

17. Pilot Testing Procedure (Optional) 65

18. Gas Burners 71

19. Additional Considerations for Oil Burners 74

20. Additional Considerations for Low NOx Burners 75

vii

Burners for Fired Heaters in General Refinery Services

1. Scope

   This recommended practice (RP) provides guidelines for the selection and/or evaluation of burners installed in fired heaters in general refinery services. Details of fired heater and related equipment designs are considered only where they interact with the burner selection. This RP does not provide rules for design but indicates areas that need attention. It offers information and descriptions of burner types available to the designer/user for purposes of selecting the appropriate burner for a given application.

   
   

   The burner types discussed are those currently in industry use. It is not intended to imply that other burner types are not available or recommended. Many of the individual features described in these guidelines will be applicable to most burner types.

   
   

   In addition to specification of burners, this RP has been updated to include practical guidelines for troubleshooting in service burners as well as including considerations for safe operation.

   
   

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. Changes in referenced standards, codes, and specifications shall be mutually agreed to by the owner and the vendor.

   
   

   API Standard 560, Fired Heaters for General Refinery Services

   
   

3. Terms and Definitions

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

3.1

adiabatic flame temperature

Temperature that results from a complete combustion process without any heat transfer or changes in kinetic or potential energy.

3.2

aerosols

A suspension of fine solid or liquid particles in gas (smoke, fog, and mist are aerosols).

3.3

air/fuel ratio

The ratio of the combustion air flow rate to the fuel flow rate. This may either be in mass or volume units and needs to be specified.

3.4

air register

That part of a burner that can admit combustion air through openings around the burner assembly.

3.5

atomization

The breaking of a liquid into tiny droplets to improve fuel–air mixing, thereby improving combustion efficiency. Steam, air, and fuel gas can be used as atomizing media. Steam is the most common in the refining industry. Atomization may also be accomplished by mechanical means.

1