Control Techniques for Nitrogen Oxides Emissions from Stationary Sources, Revised, 2nd Edition


                                     EPA-450/3-83-002
Control Techniques for Nitrogen  Oxides
  Emissions from Stationary Sources-
          Revised Second Edition
             Emission Standards and Engineering Division
             U.S. ENVIRONMENTAL PROTECTION AGENCY
                Office of Air, Noise, and Radiation
              Office of Air Quality Planning and Standards
             Research Triangle Park, North Carolina 27711

                     January 1983

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This report has been  reviewed by the Emission Standards and Engineering Division of the
Office of Air Quality Planning and Standards, EPA, and approved for publication. Mention of
trade names  or commercial  products  is not  intended to constitute  endorsement  or
recommendation for use. Copies of this report are available through the Library Services Office
(MD-35), U.S. Environmental Protection Agency, Research Triangle Park, N.C. 27711, or from
National Technical Information Services, 5285 Port Royal Road, Springfield, Virginia 22161.

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                                          TABLE OF CONTENTS


Section                                                                                        Page

          LIST OF FIGURES	,	     viii

          LIST OF TABLES	•	.  . .  .	     xi

          SUMMARY	     S-l

   1      INTRODUCTION.	. .	>	     1-1

   2      CHARACTERIZATION OF M0v EMISSIONS	.	     2-1
                                X

          2.1  Definitions and Formation Theory	     2-1
          2.2  Sampling and Analysis Methods	.  .     2-2
          2.3  Equipment Descriptions, Emissions Estimates, and Emiss'ion Factors
               by Application Sector	   2-3

          2.3.1  Stationary Fuel Combustiori Sources	     2-7

          2.3.1.1  Utility Boilers	     2-7
          2.3.1.2  Industrial Boilers 	 . 	     2-15
          2.3.1.3  Commercial and Residential  Space Heating	.  .  . .	     2-18
          2.3.1.4  Internal Combustion Sources.	     2-18

          2.3.1.4.1  Stationary Reciprocating Internal Combustion
                       Engines	     2-18
          2.3.1.4.2  Gas Turbines	  .     2-19

          2.3.2  Industrial Process Heating	     2-22

          2.3.2.1  Iron and Steel Industry	     2-26
          2.3.2.2  Glass Industry	     2-29
          2.3.2.3  Cement Manufacturing Industry	     2-29
          2.3.2.4  Petroleum Refinina Industry	  .     2-31
          2.3.2.5  Brick and Ceramic Kilns	  .     2-31
          2.3.2.6  Nonccmbustion and Otner Minor Industrial Sources 	     2-34

          2.3.3  Solid Waste Disposal Sources	.....*..	     2-34
          2.3.4  Other Miscellaneous NO,, Sources	     2-45
                                       /\

          REFERENCES FOR SECTION 2	     2-49

   3      CONTROL TECHNIQUES	     3-1

          3.1  Combustion Modifications i	     3-1

          3.1.1  General Concepts on NO  Formation and Control	    -3-1

          3.1.1.1  Thermal NOV.	     3-2
          3.1.1.2  Fuel NOX ,	     3-4
          3.1.1.3  Summary of Process Modification Concepts 	     3-12

          3.1.2  Modification of Operating Conditions .....  	     3-14

          3.1.2.1  Low Excess Air Combustion (LEA)	     3-14
          3.1.2.2  Off-Stoichiometric or Staged Combustion(OSC)  	     3-15
          3.1.2.3  Flue Gas Recirculation(FGR)	     3-19
          3.1.2.4  Reduced Air Preheat Operation(RAP) 	     3-20
          3.1.2.5  Reduced Firing Rate	     3-21
          3.1.2.6  Steam and Water Injection(HI). ,v	     3-22
          3.1.2.7  Combinations of Techniques . . 	 ...     3-22
                                                iii

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                                    TABLE OF CONTENTS (Continued)

Section                                                                                        Page
          3.1.3  Equipment Design Modification  	     3-24
          3.1.3.1  Burner Configuration 	     3-24
          3.1.3.2  Burner Spacing 	     3-28
          3.1.3.3  Advanced Burner/Furnace Designs  	  	  .  .  .     3-28
          3.1.4  Fuel Modification.  .	     3-30
          3.1.4.1  Fuel Switching	i  .  .  .  .     3-31
          3.1.4.2  Fuel Additives	     3-34
          3.1.4.3  Fuel Denitrification 	     3-34
          3.1.5  Alternate Processes	'.	     3-35
          3.1.5.1  Fluidized Bed Combustion 	     3-35
          3.1.5.2  Catalytic Combustion 	 ,  	     3-36
          3.1.5.3  Repowering	     3-37
          3.1.5.4  Combined Cycles	.'.....     3-33
          3.2  Combustion Flue Gas Treatment	     3-39
          3.2.1  Dry Flue Gas Treatment	     3-39
          3.2.1.1  Selective Catalytic Reduction(SCR) 	     3-40
          3.2.1.2  Selective Noncatalytic Reduction (SNR)	     3-42
          3.2.1.3  Other Dry FGT Processes	     3-43
          3.2.2  Wet Flue Gas Treatment	     3-44
          3.3  Noncombustion Gas Cleaning	     3-45
          3.3.1  Plant Design for NO  Pollution Abatement at New Nitric Acid Plants  ....     3-45
          3.3.1.1  Absorption Column Pressure Control	."	'	     3-46
          3.3.1.2  Strong Acid^Processes	     3-46
          3.3.2  Retrofit Desian for NOV Pollution Abatement at New or Existing
                 Nitric Acid Plants .	     3-47
          3.3.2.1  Chilled Absorption 	  ...     3-47
          3.3.2.2  Extended Absorption. . ;	1  ....     3-48
          3.3.2.3  Wet Chemical Scrubbing 	  ....     3-48
          3.3.2.4  Catalytic Reduction	'	     3-50
          3.3.2.5  Molecular Sieve Adsorption 	     3-53
          REFERENCES FOR SECTION 3	     3-54
   4      LARGE FOSSIL FUEL COMBUSTION PROCESSES	     4-1
          4.1  Utility Boilers	     4-1
          4.1.1  Control Techniques 	     4-3
          4.1.1.1  Combustion Modifications	     4-3
          4.1.1.2  Flue Gas Treatment	,	     4-25
          4.1.2  Costs	     4-33
          4.1.2.1  Combustion Modification	,	     4-33
          4.1.2.2  Flue Gas Treatment 	   •  4-38
                                                 iv

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                                    TABLE OF CONTENTS (Continued)

Section                                                     ,                             .      Page
          4.1.3  Energy and Environmental Impact	    4-44
          4.1.3.1  Energy Impact  	    4-44
          4.1.3.2  Environmental Impact 	 	    4-48
          4.2  Industrial Boilers	    4-55
          4.2.1  Control Techniques	    4-56
          4.2.1.1  Combustion Modification	    4-59
          4.2.1.2  Post Combustion Techniques	    4-76
          4.2.2' Cost Impact	  •  4-78
          4.2.2.1  'Combustion Modification Techniques 	    4-78
          4.2.2.2  Post Combustion Techniques . »  	    4-83
          4.2.3  Energy and Environmental Impact   	    4-84
          4.2.3.1  Energy Impact	    4-84
          4.2.3.2  Environmental Impact	 	    4-87
          4.3  Prime Movers ...... 	    4-88
          4.3.1  Reciprocating  Internal Combustion Engines. ... 		  .    4-88
          4.3.1.1  Control Techniques  ,	    4-88
          4.3.1.2  Costs	,	    4-96
          4.3.1.3  Energy and Environmental Impact,		    4-102
          4,3.2  Gas Turbines	    4-109
          4.3.2.1  Control Techniques	    4-114
          4.3.2.2  Costs	    4-118
          4.3.2.3  Energy and Environmental Impact	    4-122
          4.4  Summary	*	    4-124
          REFERENCES FOR SECTION 4	    4-127
   5      OTHER COMBUSTION PRCCESSES	    5-1
          5.1 " Space Keating	    5-1
          5.1.1  Emissions. -	    5-2
          5.1.2  Control Techniques ......'	  '5-4
          5.1.2.1  Tuning	".  . .	    5-4
          5.1.2.2  Equipment Replacement	    5-8
          5.1.3  Costs...	    5-14
          5.1.4  Energy  and Environmental Impact	    5-16
          5.1.4.1  Energy Impact. 	    5-16
          £.1.4.2  Environmental Impact 	 ..... 	    5-16
          5.2  Incineratjon and Open Burning	.,	    5-18
          5.2.1  Municipal and  Industrial Incineration.	    5-18
          5.2.1.1  Emissions	,	    5-19
          5.2.1.2  Control Techniques  	 	    5-19
          5.2.1.3  Costs	    5-22

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                                    TABLE OF CONTENTS (Continued)

Section                                                                                        Page
          5.2.2  Open Burning	     5-22
          5.2.2.1  Emissions	     5-22
          5.2.2.2  Control Techniques 	     5-23
          5.3  Industrial Process Heating 	     5-26
          5.3.1  Petroleum, Chemicals, and Natural Gas	     5-27
          5.3.1.1  Fired Heaters	     5-27
          5.3.1.1.1  Process Description	     5-27
          5.3.1.1.2  Emission and Control Techniques	     5-40
          5.3.1.2  Catalytic Crackers and CO Boilers	 .     5-68
          5.3.1.2.1  Process Description	     5-68
          5.3.1.2.2  Emissions and Control Technology 	     5-68
          5.3.2  Metallurigical Processes	     5-70
          5.3.2.1  Process Description and Control Techniques 	     5-70
          5.3.2.2  Emissions	     5-77
          5.3.3  Glass Manufacture	.,	     5-79
          5.3.3.1  Process Description	     5-79
          5.3.3.2  Emissions	     5-83
          5.3.3.3  Control Techniques 	 	     5-85
          5.3.4  Cenient Manufacture	.'...„	     5-85
          5.3.4.1  Process Description. ......... 	     5-85
          5.3.4.2  Emissions	     5-87
          5.3.4.3  Control Techniques 	     5-38
          5.3.5  Coal Preparation Plants	'.	     5-89
          REFERENCES FOR SECTION 5	,	     5-91
   6      NONCOMBUSTION PROCESSES 	     6-1
          6.1  Nitric Acid Manufacture	     6-2
          6.1.1  Dilute Nitric Acid Manufacturing Processes	•	     6-?.
          6.1.1.1  Single Pressure Processes	     6-4
          6.1.1.2  Dual Pressure Processes. 	     6-4
          6.1.1.3  Nitric Acid Concentration	, .     6-7
          6.1.1.4  Direct Strong Nitric Acid Processes	     6-7
          6.1.2  Emissions	     5-10
          6.1.3  Control Techniques for NOV Emissions from Nitric Acid Plants 	     6-11
                                          X
          6.1.3.1  Chilled Absorption 	     5-14
          6.1.3.2  Extended Absorption	I ....     6-16
          6.1.3.3  Wet Chemical Scrubbing 	     6-16
          6.1.3.4  Catalytic Reduction	     6-25
          6.1.3.5  Molecular Sieve Adsorption 	     6-29
          6.1.4  Costs	     6-33

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                                    TABLE OF CONTENTS (Continued)

Section                                                                                        Page
          6.2  Nitric Acid Uses	     6-36
          6.2.1  Ammonium Nitrate Manufacture 	  .....     6-36
          6.2.1.1  Process Description	     6-36
          6.2.1.2  Emissions	     6-38
          6.2.2  Organic Oxidations ..... 	     6-38
          6.2.2.1  Process Description	.	     6-38
          6.2.2.2  Emissions	'.	     6-39
          6.2.2.3  Control Techniques	     6-39
          6.2.2.4  Costs.	     6-40
          6.2.3  Organic Nitrations	     6-40
          6.2.3.1.  Process Description	     6-40
          6.2.3.2  Emissions	     6-46
          6.2.3.3  Control Techniques	     6-47
          6.2.3.4  Costs	,	     6-49
          6.2.4  Explosives:  Manufacture and Use 	     6-49
          6.2,4.1  Process Description	     6-49
          6.2.4.2  Emissions	     5-50
          6.2.4.3  Controls	     6-52
          6.2.4.4  Costs.	......;..     6-52
          6.2.5  Fertilizer Manufacture	,	  .     6-52
          6.2.6  Metals Pickling	     6-54
          REFERENCES FOR SECTION 6.	     6-55
          APPENDIX A - SELECTED TABLES IN ENGLISH UNITS .....  	  	     A-l
          APPENDIX B - PREFIXES FOR SI UNITS	     B-l
          APPENDIX C - GLOSSARY	     C-l
                                                vii

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LIST OF FIGURES
Figure
2-1
2-2
3-1
3-2
3-3

3-4
3-5

3-6

3-7
3-8
4-1
4-2

4-3

4-4
4-5

4-6
4-7
4-8
4-9
4-10
4-11
4-12
4-13
4-14
4-15
4-16


Stationary Sources Of NO Emissions 	
Load Reduction Coefficient As A Function Of Boiler Load 	
Nitrogen And Sulfur Content Of U.S. Coal Reserves 	 ,
Conversion Of Fuel N In Practical Combusters 	 • 	
Possible Fate of Fuel Njtrogen Contained in Coal Particles During
Combustion 	
Conversion Of Nitrogen In Coal To NO 	 , .
Typical Arrangements For (B) Overfire Air, (A) Burners Out Of Service, And
CC) Flue Gas Recirculation 	
Correlation Of NO Emissions With Water Injection Rate For Natural Gas
Fired Gas Turbifie (Houston L&P Wharton No. 43 Unit) 	
Flow Diagram For Typical NO -Only SCR Process 	 ; 	
Extended Absorption System On Existing Nitric Acid Plant 	
Baseline NO Emissions - Coal-Fired Utility Boilers 	
Effect Of Combustion Modification Methods On Total Nitrogen Oxides .
Emissions And Boiler Efficiency 	 , 	 	
Effects Of Flue Gas Oxygen On The Formation Of NO Emissions From
Gas- And Oil-Fired Boilers 	 x 	 	
FGR Test Results on 5.1 MW (17.5 x 106 Btu/hr) Packaged Watertube Boiler ....
Effects Of Air Preheat Temperature On NO Emissions From Gas- And
Oil-Fired Boilers 	 x 	
Effects Of Excess Air On NO,, Emissions From Stoker Coal-Fired Boilers 	
/\
Effects Of NOX Emissions Level On Fuel Penalty For Lightduty Trucks 	
Effect Of Derating On 1C Engine HC Emissions 	
Effect of Retarding Ignition Timing On 1C Engine KC Emissions 	
Effect Of Air-To-Fuel Ratio On 1C Enoine HC Emissions 	
Effect Of Decreased Manifold Air Temperature On 1C Engine HC Emissions 	
Effect Of Water Injection On 1C Engine HC Emissions 	
Smoke Levels Versus NO Level For Large Bore Diesel Engines 	 ....
NO Emissions From Large Gas Turbines Without NO Controls 	
X X
NO Emissions From Small Gas Turbines Without NO Controls 	
NOV Emissions From Gas Turbines Having NOV Controls And Operating
5n Liquid Fuels 	 x 	
_Page
2-4
2-14
3-6
3-8

3-9
3-11

3-17

3-23
3-41
3-49
4-2

4-60

4-64
4-68

4-70
4-73
4-103
4-106
4-106
4-107
4-108
4-108
4-110
4-112
4-113

4-117
     viii

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LIST OF FIGURES (Continued)
Figure
5-1

5-2

5-3

5-4
5-5
5-6

5-7

5-rS
5-9
5-10

5-11

5-12

5-13
5-14
5-15
5-16
5-17

5-18
5-19
6-1
6-2
6-3
6-4
6-5
6-6
6-7
6-8

General Trend Of Smoke, Gaseous Emissions, And Efficiency Versus
Stoichiometric Ratio For Residential Heaters. . 	 	
Effect of Excess Air On NO Emissions From A 45.3 Mg (50 Ton) Per Day
Batch-Feed Incinerator. . 	
Effect Of Underfire Air On HO Emissions From A 227 Mg (250 Ton) Per Oay
Continuous Feed Incinerator 	 . 	
Examples Of Fired Heater Designs 	 	 	
Typical Burners By Type Of Fuel Burned. . 	
MO Emissions From Standard Premix Burners 	
X
NO Emissions From A Refinery Gas-Fired Reforming Heater With Low Excess
Hir Burners 	 	 	 	
NOV Emissions From A Single Burner, Forced Draft Debutanizer Bottoms Reboiler . .
A
Forced Draft Crude Heater With Staaed Combustion Burners 	 	 	 '
NO Emissions From A Natural Draft Naptha Reformer With Staged Combustion
Air Burners 	 '....... 	 	
NOX Emissions From A Balanced Draft Crude Preheater With Staged Combustion
Air Burners, Combustion Air Preheater 485 To 500K ......; 	
NO Emissions As A Function Of Stack Oxygen For A Distillate Oil -Fired,
Natural Draft Process Heater. .... 	
Residual Oil -Fired Horizontal Heater With Staged Combustion Air Burners 	
Residual Oil-Fired Natural Draft Cylindrical Heater 	 , 	
Residual Oil/Refinery Gas-Fired Natural Draft Heater 	 	 .
NO Emissions From A Natural Draft Atmosphere Crude Heater With Staged
Combustion Air Burners, Oil And Gas Fuel Combustion 	 	
NO Emissions From A Natural Draft Vacuum Distillation Column Heater
with Staged Combustion Air Burners, Oil And Gas Firing 	
NO Emissions As A Function Of Time For An Open Hearth Furnace 	
The Effect Of Cement Kiln Temperature- On NOX Emissions 	 	 .
Single Pressure Nitric Acid Manufacturing Process 	 	
Dual Pressure Nitric Acid Plant Flow Diaarem 	 ,
Nitric Acid Concentrating Unit 	
Process Flow Diagram For Direct Production Of Highly Concentrated Nitric Acid . .
Schematic Diagram Of The CDL/VITOK NO Removal Process. . . 	
TVA Chilled Absorption Process 	
Grande Pariosse Extended Absorption Process For NO Treatment 	
Flow Diagram Of The MASAR Process 	 	 	 	
Page

5-3

5-20

5-21
5-34
5-39
5-42


5-46
547
. 5-49

5-51

5-52

5-54
5-55
5-56
5-58
5-60

5-61
5-81
5-90
6-5
6-6
6-8
6-9
6-15
6-17
6-18
6-20

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                           LIST OF FIGURES (Continued)
Process Flow Diagram For The Gcodpasture Process	    6-23
Nonselective Catalytic Reduction System ....  	  .  	    6-26
Molecular S*eve System	    6-30
Batch Process For The Manufacture Of Nitroglycerln  (N6)  	 	    6-42
Schmld-Heissner Continuous-Nitration Plant	    6-43
Biazzi Continuous-Nitration Plant 	    6-44
Recovery Of Spent Add	    6-45
Trinitrotoluene (Batch Process) Manufacturing Diagram  	    6-51

-------
LIST OF TABLES
Table,
S-l
S-2
S-3
S-4
S-5
2-1
2-2

2-3

2-4

2-5

2-6

2-7

2-8

2-9

2-10

2-11
2-12

2-13

2-14

2-15

2-16


2-17

2-18


Nationwide 1980 Nitrogen Oxide Emissions From Stationary Sources 	
Summary of NO Control Techniques 	 .............
Summary of Combustion Process Modification Concepts 	
Overall Evaluation of NOV Control Techniques for Combustion Sources 	
x s
NO Abatement Methods on New or Existing Nitric Acid Plants 	
National Estimates of Nitrogen Oxide Emissions 	 .......
i960 Nitrcgenoxide Emissions From Fuel Combustion In Stationary Sources
By Category for Major Fuels 	 	 	 ......
Nitrogen Oxide Emission Factors for Bituminous and Sub-Bituminous Coal
Combustion 	 	 	
Nitrogen Oxide Emission Factors for Anthracite Coal Combustion Without
Control Equipment 	 	 	 	
Nitrogen Oxide Emission Factors for Lignite Combustion Without Control
Equipment . . '. 	 	 	 , . .
Nitrogen Oxide Emission Factors for Fuel Oil Combustion Without Control
• Equipment 	 	 	 	 	
Nitrogen Oxide Emission Factors for Natural Gas Combustion Without
Control Equipment . : 	 	 	
Nitrogen Oxide Emission Factors for LPG Combustion Without Control
Equipment 	 	 	
Nitrogen Oxide Emission Factors for Wood/Bark Waste Combustion Without
Control Equipment 	
Nitrogen Oxide Emission Factors for Bagasse Combustion Without Control
Equipment 	 	 ..........
Nitrogen Oxide Emission Factors for Residential Fireplaces 	
Nitrogen Oxide Emission Factors for Heavy-Duty, Natural Gas-Fired Pipeline
Compressor Engines Without Control Equipment 	 	
Nitrogen Oxide Emission Factors for Stationary Large Bore Diesel and

Composite Nitrogen' Oxide Emission Factors for the 1971 Population of
Electric Utility Turbines Without Control Equipment 	 . 	
Nitrogen Oxide Emission Factors for Keavy-Duty, Natural Gas-Fired Pipeline
Compressor Gas Turbine Engines Without Control Equipment. , 	
Nationwide Nitrogen Oxide Emissions Estimates From Major Industrial Process
Sources, 1970 - 1980 	 	
1
Nitrogen Oxide Emission Factors for Coke Manufacture Without Control
Equipment 	 . 	 	
Nitrogen Oxide Emission Factors for Gray Iron Furnaces Without Control
Equipment 	 	 	 	 	 	
Page
. . S-2
. . S-4
. . S-5
. . S-8
. . S-13
'. . 2-5

. . 2-6

. . 2-10

. . 2-11

. . 2-11

. . 2-12

. . 2-13

. . 2-16

. . 2-16

. . 2-17
. . 2-17

. . 2-20

. . 2-21

. . 2-23

. . 2-24

. . 2-25


, , 2-27

2-27
     xi

-------
LIST OF TABLES (Continued)
Table
2-19

2-20

2-21

2-22

2-23
2-24

2-25
2-26
2-27
2-28
2-29

2-30
2-31
2-32

2-33

2-34
2-35
3-1
3-2
3-3
4-1
4-2
4-3
4-4

4-5
4-6
4-7

Nitrogen Oxide Emission Factors for Steel Foundries Without Control
Equipment 	
Nitrogen Oxide Emission Factors for Glass Manufacturing Melt Furnaces
Without Control Equipment 	
Nitrogen Oxide Emission Factors for Glass Fiber Manufacturing Without
Control Equioment 	 	 	
Nitroaen Oxide Emission ^Factors for Cement Manufacturing Without Control
Equipment 	 	
Nitrogen Oxide Emission Factors for Petroleum Refineries. . . . r 	
Nitrogen Oxide Emission Factors for Brick Manufacturing Without Control
Equipment 	 	
Nitrogen Oxide Emission Factors for Nitric Acid Production 	
Nitrogen Oxide Emission Factors for Adiptic Acid Manufacture 	
Nitnjgen Oxide Emission Factors for Explosive Manufacturing 	
Nitrogen Oxide Emission Factors for Miscellaneous Industrial Processes 	
Nitrogen Oxide Emission Factors for Refuse Incinerators Without Control
Equipment 	
Nitrogen Oxide Emission Factors for Sewage Sludae Incinerators 	
Nitrogen Oxide Emission Factors for Auto Body Incinerators. . . . 	
Nitrogen Oxide Emission Factors for Waste Incineration in Conical Burners
Without Control Equipment 	
Nitrogen Oxide Emission Factors for Open Burning of Nonagri cultural
Materials 	
Nitrogen Oxide Emission Factors for Forest Wildfires 	 	
Nitrogen Oxide Emission Factors for the Dentonation of Explosives 	
Factors Controlling the Formation of Thermal NO 	
Summary of Combustion Process Modification Concepts 	
NO Formation Potential of Some Alternate Fuels 	
Average NO Reduction With Low Excess Air Firing. ... 	
Average NO Reduction With Burner Out of Service 	
X
Average NQX Reduction With Overfire Air 	
Average NOX Reduction With Flue Gas Recirculation 	 	 . .

Average NOX Reduction With Reduced Firing Rate 	 * 	
Average NO Reduction With Off Stoichicmetric Combustion and Flue Gas
Secirculatlon ..... 	 	
Average NO Reduction With Reduced Firing Rate and Off Stoichiometric
Combustion 	
Page

2-28

2-28

2-30

2-32
2-33

2-35
2-36
2-37
2-38
2-39

2-43
2-44
2-44

2-46

2-46
2-47
2-48
3-5
3-13
3-32
4-5
4-6
4-7
4-8

4-9
4-10
4-11
           xii

-------
LIST OF TABLES (Continued)
Table.
4-8

4-9
4-10
4-11
4-12
4-13
4-14
4-15
4-16
4-17
4-18



4-20

4-21-

4-22

4-23

4-24

4-25
4-26
4-27
4-28

4-29

4-30
4-31
4-32
4-33

4-34

Average NO Reduction With Load Reduction, Off Stoichiometric Combustion
and Flue Gas Recirculation. . 	
Effect of Low NO Operation on Coal -Fired Boilers 	
Effect of Low NO Operation on Oil-Fired Boilers. 	 	
Effect of Low NO Operation on Gas-Fired Boilers 	 	
X
Summary of Utility Boiler Combustion Modification Control Costs 	
Projected Retrofit Control Requirements for Alternate NO Emission Levels ....
NO FGT Processes Selected for Evaluation By TVA in 1980 Study 	
Capital Investment Developed By TVA for Alternative FGT Systems . . . 	 	
Annual Revenue Requirements Developed by TVA for Alternative FGT Systems. ....
Summary of Capital Investments Developed in 1981 TVA Study 	
Sunmarv of Annual Revenue Reciri rements Developed in 1981 TVA Study. .......
a. Estimated Total Capital Requirement of Post Combustion NO Y Control Processes

b. Estimated Levelized Cost Reauirement of Post Combustion N0» Control Processes
Partial Summary of EPA/Acurex Combustion Modification Environmental Assessment
Field Testing 	 	 	 	
Measured Change in the Concentrations of Selected Pollutants Across the"
EPA Pilot Plant SCR Reactors 	
Installed Capacity of U.S. Watertube Industrial Boilers By Unit Size and
Fuel Type (in 1977) 	
Installed Capacity of U.S. Industrial Fire-Tube Boilers By Unit Size and
Fuel Type (1977) 	 	
NO Emission Control Techniques for Gas-Fired and Oil-Fired Industrial
Boilers 	 	 	
NO Emission Control Techniques for Coal-Fired Stoker Industrial Boilers. ....
Safe Operating Levels for LEA 	 . 	
Estimated Cost of Low Excess Air Operation for New Boilers (.1978 Dollars) ....
Estimated Cost of Staged Combustion Operation for New Boilers (1978
Dollars) 	 	 	
Estimated Cost of Flue Gas Recirculation Operation for New Boilers
(1978 Dollars^ 	 	 	 . .
Annual Cost of NO Control Systems Applied to Coal -Fired Boilers 	
Annual Cost of NO Control Systems Applied to Oil-Fired Boilers . . . 	 	
Annual Cost of NO Control Systems Applied to Natural Gas-Fired Boilers ......
A
Summary of NOV Emission Control Techniques for Reciprocating Internal
Combustion Engines 	
Effect of NO Controls on Large-Bore Internal Combustion Engines 	
Page.

4-12
4-14
4-20
4-23
4-35
4-36
4-40
4-42
4-42
4-43
4-43




4-49

4-54

4-57

4-58

4-61
4-62
4-65
4-80

4-81

4-82
4-85
4-85
4-85

4-89
4-91
        xiii

-------
LIST OF TABLES (Continued)
Table
4-35

4-36
4-37
4-38
4-39
4-40
4-41

4-42

4-43

4-44
4-45
4-46
4-47
4-48
4.49

4-50
5-1
5-2
5-3
5-4

5-5

5-6
5-7

5-8
5-9
5-10
5-11

Control Techniques for Truck Size Diesel Engines [^375 kW (500 HP)] to Meet
1975 California 13.4 G/KWHR (10 6/HP-HR) Combined NOX and HC' Level 	
1975 Vehicle Emission Limits 	
Emission Control Techniques for Automotive Gasoline Engines 	
Emission Control Systems for Conventional Gasoline Internal Combustion Engines. .
Cost Impacts of NO Controls for Large-Bore Engines 	
Typical 1974 Baseline Costs for (Large>75 kW/cylinder) Engines • • • 	
Typical Control Costs for Diesel-Fueled Engines Used in Heavy-Duty Vehicles
(>2700 kg or 3 tons). ... 	
Estimates of Sticker Prices for Emissions Hardware from 1966 Uncontrolled
Vehicles to 1976 Dual -Catalyst Systems 	 ...... 	
Representative Effects of NO Control on CO Emissions from Internal Combustion
Engines 	 	 	
Relationship Between Smoke, EGR, and Retard 	
Gas Turbine - Summary of Existing Technology - Combustion Modifications .....
Impact of NO Emission Control on the Installed Capital Cost of Gas Turbines . .
Water Injection Costs, Mills/kWh . . 	 	
Representative Effects of NO Controls on CO Emissions from Gas Turbines ....
Summary of the Effects of NO Controls on Vapor Phase Hydrocarbon Emissions from
Gas Turbines 	 	
Summary of NO Controls Technology 	 ...
X
Emission Factors for Residential and Commercial Heating Systems .........
Uncontrolled NOX Emissions from Residential Space Heating Systems 	
Comparison of Hean Emissions for Cyclic Runs on Residential Oil -Fired Units . . .
Performance Summary of Low-NO Control Equipment for Natural Gas-Fired
Residential Heaters 	 	
Performance Summary of Low-NO Control Equipment for Distillate Oil-Fired
Residential Heaters 	 	
Cost Impact of NO Control Alternatives 	
Effects of Low-NO Operation on Incremental Emissions and System Performance
for Residential Wlrm Air Furnaces 	
Annual Emissions of Nitrogen Oxides from Open Burning 	
Major Refinery Processes Requiring a Fired Heater 	
Typical Fired Heater Applications in the Chemical Industry 	
Basic Fired Heater Applications 	
Page

4-93
4-94
4-94
4-95
4-98
4-98

4-99

4-100

4-104
4-111
4-115
4-119
4-120
4-123

4-123
4-125
5-5
5-6
5-7

5-9

5-10
5-15

5-17
5-23
5-28
5-31
5-32
                    xiv

-------
                                     LIST OF TABLES (Continued)

Table                                                                                          Page
 5-12     Summary of NO  Test Data on a Standard Duel Fuel Burner	    5-44
 5-13     Retrofit Costs for Low-NO  Burners	    5-66
 5-14     NO  Emissions from Petroleum Refinery CO Boilers. 	    5-69
 5-15     Estimated HOX Emissions from Steel Hill Processes and Equipment 	    5-78
 5-16     Effects of NO  Controls on Steel Industry NO  Emissions 	    5-80
 5-17     NO  Emissions from Glass Melting Furnaces 	    5-84
 5-18     Recommended Programs for Reducing Emissions and Energy Consumption in the
          Glass Industry	    5-86
 6-1      NO,. Abatement Methods on Nevf or Existing Nitric Acid Plants	    6-12
            A
 6-2      Performance of Hercules Purasiv N Unit During Three Day Pun 	    6-31
 6-3   •   Performance of U-. S. Army-Holston Purasiv N Unit During Three-Day Run	    6-32
 6-4      Capital and Operating Costs for Different NO  Abatement Systems in a 270 Mg/d
          Nitric Acid Plant		    6-34
 6-5      Annual Energy Requirements (TJ) for NO  Abatement Systems for a 270 Mg/d
          Nitric Acid Plant . .		    6-35
 6-6      Basis for Tables 6-4 and 6-5	    6-35
 6-7      Annual Nitric Acid Consumption in the United States, 1974	    6-37
 6-8      Estimated NOX Emissions from Organic Nitrations in 1970*	    6-48
 6-9      Emission Factors for Manufacture of Explosives	    6-53
 A6-4     Capital and Operating Costs for Different NO  Abatement Systems in a 300 TPD
          Nitric Acid Plant	    A-2
                                        9
 A.6-5     Annual Energy Requirements (10  Btu) for NO  Abatement Systems for a 300 TPD
          Nitric Acid Plant	x	    A-3
                                                 xv

-------

-------
SUMMARY
CHARACTERIZATION OF NOV EMISSIONS
A
Manmade oxides of nitrogen are currently emitted at a rate of about 20 Tg (22 million
tons/yr) in the United States. Stationary sources account for approximately 60 percent of these
emissions, of which 97 percent are due to combustion sources. Combustion generated NOX is derived
from two separate formative mechanisms, thermal NO and fuel NO . Thermal NO results from the
thermal fixation of molecular nitrogen and oxygen in the combustion air. This is the dominant
mechanism with the firing of clean fuels such as natural gas and distillate oil. Fuel NO results
from the oxidation of organically bound fuel njtrogen compounds. This can be the dominant mechani-sm
with the firing of coal and high nitrogen residual oils. The rate of formation of both thermal NO
X
and fuel NO is strongly dependent on the combustion process conditions. The emissions due to both
mechanisms are increased by intense combustion resulting from rapid mixing of the air and fuel
streams. Additionally, the emissions due to. thermal NOV are sharply increased by increased local
A ,
combustion temperatures.

Since equipment process, conditions and fuel type are so important in determining NO
emissions, the characterization of emissions and the evaluation of control potential requires
detailed classification of stationary sources according to factors known to influence NOX formation.
Over 100 combinations of equipment type and fuel type are identified as having significantly
different potential for NO emissions and/or NO control. The emission compilation for these
X X
sources for the year 1974 shows, however, that the 30 most significant equipment/fuel combinations
are responsible for .over 80 percent of stationary source emissions.

The total 1980 nationwide NO emissions from stationary sources, grouped according to appli-
cation sector, are shown in Table S-l, On an uncontrolled basis, utility boilers accounted for
about 58 percent of stationary source emissions. These boilers fired 61 percent coal, 18 percent
oil, and 21 percent gas. For all stationary sources, the firing of coal yielded about 51 percent of
total NOX, the firing of oil yielded about 8 percent, and the firing of natural gas yielded
30 percent. Wood, kerosene, LPG, and coke generated the majority of the remaining NO emissions.
S-l

-------
                   TABLE S-l.  NATIONWIDE 1980 NITROGEN OXIDE EMISSIONS
                               FROM STATIONARY SOURCES
Stationary Source Category
Fuel Combustion
Electric Utilities
Industrial
Commercial -Institutional
Residential
Fuel Combustion Total
NO Emissions,
Tgx(10° tons)

, 6.4 (7.0)
3.0 (3.3)
0.3 (0.33) , '
0.3 (0.33)
10.0
Percent of Total
Emissions

58
27
2.7
2.7
(11)


91
Industrial Processes                              0.7 (0.77)                6.3

Solid Waste Disposal

     Incineration                    0.0 (0)       .              0
     Open Burning                    0.1 (0.11)                   0.9
     Solid Waste Total                            0.1 (0.11) .               0.9

Miscellaneous

     Forest Fires                    0.2 (0.22)                   1.8
     Other Burning                   0.0 (0)                      0
     Hisc. Organic Solvent           0.0 (0)                      0_
     Miscellaneous Total0.2 (0.22)                1.8

Total of All Categories                          11.0 (12.1)              100
                                 S-2

-------
CONTROL TECHNIQUES
• Current and advanced methods for stationary source NOV control operate either through
A
suppression of NOV formation in the process or through physical or chemical removal of NO from the
X X
stack gases. Both processes are effective with combustion sources, though most domestic experience
has involved suppression of NO formation. Candidate NO suppression approaches include combustion
process modification through alteration of operating conditions on existing systems or alternate
design of new units; fuel modification through fuel switching, fuel denitrification, or fuel
additives; and use of alternate combustion concepts such as catalytic combustion and fluidized bed
combustion. Stack gas NO removal systems, principally, using selective catalytic or noncatalytic
reduction, have been extensively applied to combustion systems in Japan. However, experience in the
United States has primarily been limited to a few pilot scale demonstrations of catalytic systems
and some industrial applications of noncatalytic systems. Removal of NO from stack gases is also
effective with noncombustion sources of NO , chiefly chemical manufacturing. Candidate approaches
for this application include catalytic reduction, wet chemical scrubbing, extended and chilled
absorption, and adsorption with molecular sieves. A summary of general stationary source NO
control techniques is given on Table S-2.

Combustion process modifications have been extensively implemented on existing coal-, oil-,
and gas-fired boilers to comply with local emission standards. Combinations of external control
techniques such as low excess air firing, flue gas recirculation and staged combustion have yielded
emission reductions of up to 60 percent compared to the uncontrolled, baseline emissions of units
designed prior to the 1970s. Staged combustion techniques include biased burner firing, burners out
of service, and overfire air injection. A summary of combustion modification concepts is given in
Table S-3.

Currently, the most commonly applied low NOX technique for coal-fired utility boilers is
staged combustion through the introduction of overfire air. This technique has been used in both
new and retrofit applications, achieving NOX reductions of 30 to 50 percent compared to older
baseline levels, or controlled emissions of 210 to 300 ng/J (0.5 to 0.7 lb/106 Btu). More recently,
first generation low NO burners have been installed on some units and found to be at least as
effective as overfire air. In fact, new wall-fired units subject to the 1979 new source performance
standards will generally rely on low NOX burners, enlarged furnace designs, and overfire air
combustion. Corner fired units will rely on overfire and low excess air. The combination of
overfire air with low NOX burners has resulted in 40 to 60 percent NO reductions compared to older
S-3

-------
TABLE S-2.  SUMMARY OF HOX CONTROL TECHNIQUES
Ttchntqut
Ccwfcustlon
Modification
Flut 6«s/
Noncombustlon
Tail Gas
Treatment
Fuel
Switching
Fuel
Additives
Fuel
Oenltriflcitlon
Catalytic
Combustion ';
Fluldtied Bed
Cotfcustlon
Principle of Operation
Suppress thermal NO. through re-
duced flame temperature, reduced
02 level ; suppress fuel HOX
through delaying fuel/air nix-
ing or reduced 0; level In pri-
mary Dane zone
Additional absorption of NOX to
HK03J conversion of NO. to
NtyNOj; reduction of NOX to N?
by catalytic treatment
Simultaneous SOX and NO, con-
trol by conversion to clean
fuels; synthetic gas or oil
from coal; SRC; methanol;
hydrogen
Reduce or suppress NO by
catalytic action of fuel
additives
Rasovil of fuel nitrogen com-
pounds by pretreatment
Heterogeneously catalyzed
reactions yield low combus-
tion temperature, ION ther-
nal NOX
Coal cMbusttofl 1n solid bed
yields low teoperature, loa
»«
Status of Development
Operational for point
sources; pilot-scale and
full scale studies on com-
bined Modifications, opera-
tional problems and ad-
vanced design concepts for
area sources
Operational for existing
and new nitric acid plants
meeting NSPS; pilot Stale
feasibility studies for
conventional combustion
systems in U.S., but
operational in Japan
Synthetic fuel plants In
pilot-scale stage; cora-
nercial plants due by
mid-1 980 's
Inactive; preliminary
screening studies indi-
cated poor effective-
ness
Oii desulfurization
yields partial deni-
trification
Pilot-scale test beds for
catalyst screening,
feasibility studies
Pilot-scale study of at-
mospheric and pressurized
systems; focus on sulfur
retention devices


Degree of control
United by opera-
tional problems
Catalytic processes
gaining experience
with high parti cu-
late applications;
tests with additional
coal types needed.
Fuel cost differentia]
nuy exceed NOX, SOX,
control costs with
coal
Large make-up rate of
additive for signifi-
cant effect; presence
of additive as pollu-
tant
Effectiveness for coal
doubtful ; no effect on
thermal NOX
Halted retrofit appli-
cations; requires clean
fuels
Fuel nitrogen conversion
nay require control
(staging); may require
large nuke-up of lime-
stone sulfur absorbent
Applications
Near-Tern
Retrofit utility.
ndiistrial toilers,
gas turbines; im-
iroved designs;
low utility
Killers
Noncombustlon
sources (nitric
acid plants)
Negligible use
Negligible use
Negligible use
Seal' space
heaters
Negligible use
Long-Term
Optimized design trei.
point sources
Possible supplement to
combustion modifications;
simultaneous SOX/NOX
removal
New point sources,
(combined cycle)
Convert area sources
(residential)
Not pi-wising
Supplement to cottustion
modification
Possible use for resi-
dential heating, snail
boilers, gas turbines
Utility. Industrial boil-
ers beginning 1960's;
possible coablneil cycle.
waste fuel application

-------
TABLE S-3. SUMMARY OF COMBUSTION PKOCESS MODIFICATION CONCEPTS
Combustion
Conditions
Decrease
primary
flame zone
02 level
Decrease
peak
flame
temperature
Control
Concept
Decrease overall
0; level
Delayed mixing
of fuel and air
Increased fuel/
air mixing
Primary fuel-
rlch flame
zone
Decrease
ad 1 alia tic flame
temperature
Decrease com-
bustion
Intensity
Increased flame
zone cooling/
reduce resi-
dence time
Applicable
Equipment
Boilers, furnaces
Boiler, furnaces
Gas turbines
Boilers.
furnaces, 1C
Boilers, fur-
naces. 1C,
gas turbines
Boilers, furnaces
Boilers, furnaces
Effect on
Thermal NOX
Reduces 02-rich,
Mgh-IHL pockets
In the flame
- Flame cooling am!
dilution during
delayed mix re-
. duccs peak temp.
Reduces local hot
stokliiotnetric
regions in over-
all fuel lean
combustion
Flame cooling In
low-02, low-temp.
primary zone re-
duces peak temp.
Direct supres-
slon of thermal
NOx mechanism
increased flame
zone cooling
yields lower
peak temp.
Increased flame
zone cooling
yields lower
peak temp.
Effort nn
Fuel HOX
Reduces exposure
of fuel nitrogen
Intermediaries '
to 02
Volatile fuel N
reduces to llj in
the absence of
oxygen
Increases
Volatile fuel H
reduces to Hj in
the absence of
oxygen
Ineffective
Minor direct
effect! indirect
effect on mixing
Ineffective
Primary Applicable Controls
Operational
Adjustments
Low excess air
firing
Curner
adjustments

Burners out of
service; biased
burner firi.tg
Reduced air
preheat
Load reduction
Durner tilt
Hardware
Modification
Flue gas reclrcu-
lation (FGR)
Low HO x burners

Overflre air
ports, stratified
charge
Hater injection.
FGR

Major
Redesign

Optimum burner/
firebox design
Hew can design;
premlx, prevap.
Burner/firebox
design for two-
stage combustion

Enlarged firebox
increased burner
spacing
Redesign heat
transfer sur-
faces, firebox
aerodynamics
I
01

-------
baseline levels, or controlled emissions of 170 to 260 ng/J (0.4 to 0.6 lb/10 Btu). Similar
control levels should also be achievable on large pulverized coal industrial boilers.
Current testing activities are attempting to identify and quantify potential operating
problems with combustion modifications, such as increased water-wall tube corrosion under reducing
conditions. Such problems are expected to be most prevalent for retrofit applications where the
boiler was not designed for low'NOv operation. However, the results of most short term corrosion
X
tests to date have not indicated this to be a major problem.

Retrofit combustion process modifications have also been extensively applied to gas turbines.
Water injection has been sucessfully implemented to achieve emission levels of 75 ppm at 15 percent
excess oxygen. Current activity is focusing on development of dry controls using premixing,
prevaporizatio"n and controlled mixing for application to new combustor can designs.

There has been only limited field implementation of combustion process modifications for
other stationary combustion equipment e.g., small industrial and commercial boilers, residential and
commercial space heating equipment, reciprocating internal combustion engines and industrial process
furnaces. The following sequence is being pursued for NO control development for these sources:
control from operational fine tuning (e.g., low excess air firing, burner tuning), minor retrofit
modifications (e.g., biased burner firing), extensive hardware changes (e.g., new burners) and major
new equipment redesign (e.g., optimized heat transfer surfaces and burner aerodynamics).

Fuel switching for NOX control is not currently practiced due to the supply shortage of clean
fuels. A number of alternate fuels such as methanol and low-heating-value gas have low NO -
forming potential and may be utilized in the 1980's. The economic incentive for alternate fuel use
usually depends on factors other than NO control, e.g., desulfurization cost tradeoffs, system
efficiency.

Fuel oil denitrification, usually as an adjunct to oil desulfurization, shows promise for
reducing fuel NOV. This concept may be effective for augmenting combustion modifications for NO,,
A X
control with the firing of residual oil but is expensive when applied for NO reduction alone. Fuel
additives are not directly effective for suppressing NOV emissions. Their use to suppress fouling
X
and smoke emissions, however, may permit more extensive use of combustion control methods than would
otherwise be practical.
S-6

-------
Alternate combustion concepts under development include catalytic combustion and fluidized
bed combustion (FBC). Lab-scale tests of catalytic combustion have demonstrated extremely low NO
emissions with clean fuels (1-5 ppm). This concept may see application in the 1980's to stationary
gas turbines and space heating systems. Fluidized bed combustion-pilot plants have demonstrated NO
X
emissions of the same order as conventional coal-fired power plants using process modifications for
NO control (170 ng/J, or, 0.4 Ib N02/10 Btu). The potential for replacement of conventional
utility and industrial boilers by FBC depends on a number of other factors such as SO control cost
tradeoffs and operational flexibility, e.g., load following.

Stack gas treatment for NO removal has been implemented in the U.S. primarily on noncombus-
tion sources. Here, an additional incentive is the recovery of NO- as a feedstock material. The
most widely tested technique is catalytic reduction with selective or nonselective reducing agents.
The short supply of reducing agents (methane, ammonia) coupled with the loss of tail gas HO- as a
potential feedstock is causing interest to shift to alternate processes such as molecular sieve
absorption and extended absorption.

Flue gas treatment (FGT) of combustion sources has been at a low level of development in the
U.S. due largely to the lack of regulatory incentive. The developmental activity has recently
accelerated, however, as a result of increased emphasis on stationary source NO controls in the
X
national NOV abatement program. Flue gas treatment could be effective in the 1980's to augment
X
combustion process modifications on large sources if stringent emission control is required, for
example, to comply with a potential short-term NOj ai'r quality standard. Current developmental
activity includes transferring FGT technology from Japan where stringent NO controls are enforced
X
and demonstrating this technology on pilot and full scale systems in the U.S. The most advanced
processes include selective catalytic reduction and selective noncatalytic reduction. Other
techniques under development include electron beam irradiation and wet scrubbing. However, the dry
techniques currently appear to be the most cost effective, even when used in combination with wet
flue gas desulfuriration systems.
A summary evaluation of NO control techniques for combustion sources is given in Table S-4.

LARGE FOSSIL FUEL COMBUSTION PROCESSES

The three largest stationary emitters of NO are electric power plant boilers (58 percent of
the total), industrial boilers (10 percent) and prime movers, such as gas turbines and I.C. engines
(17 percent). The most widely applied NOX reduction technique is modification of operating
S-7

-------
                                  TABLE S-4.   OVEltALL EVALUATION Of  NOX  CONTI-OL TECHNIQUES FU'< CWil'STUih SCtPr.fS
Control
Technique
Low excess air
(LEA)
Flue gas reclrcu-
latlon (FGR)
Off-stokhlometrlc
combustion (OSC)
Incl. OFA, BOOS.
B8F
load reduction
Burner
modifications
Existing
Applications
Retrofit and new
utility boilers;
iome use In Indus-
trial boilers
Retrofit use on many
gas- and oil-fired
utility boilers;
demonstrated on some
types of industrial
boilers
New and retrofit use
on many utility
boilers; demonstrated
on some types of
industrial boilers
Some retrofit use
on gas and oil
utility boilers;
enlarged fireboxes
on new coal units
New and retrofit
use on utility
boilers; demon-
strated on resi-
dential furnaces
Effectiveness
10X to 30X for
thermal and fuel
N0x .
20X to SOX for
thermal ML; no
effect on fuel
N0x
20% to SOX for
thermal and fuel
NOX
Of to 40X for
thermal N0x
30X to 60X for
thermal and fuel
N0x
Operational
ImpJCt
Increase In effi-
ciency; amount lim-
ited by smoke or
CO at very low EA
Possible flame In-
stability; In-
creased vibration
No major impact
with new design;
potential for flame
instability, effi-
ciency decrease,
increased corrosion
(coal-fired) with
retrofit
Decrease in effi-
ciency and power
output; limited by
spare capacity and
smoke formation
No major impact
with new design;
retrofit use con-
strained by firebox
characteristics
Projected
Applications
Widespread use for
efficiency In-
crease; Incorpor-
ate into advanced
designs all sources
Possible use in new
Industrial boiler
designs
Widespread use in
large boilers; In-
corporate Into ad-
vanced designs
Enlarged fireboxes
used In new unit
design; limited use
for retrofit
Incorporate Into
advanced designs
utility, Industrial
boilers, residen-
tial , process fur-
naces, GT; combine
with OSC
Control
Evaluation
Primary emphasis near-
term and far-tern appli-
cations (all sources);
combined with OSC & bur-
ner mods for far-ten.i appl.
Primary emphasis near-terra
applications larg^ boilers;
possible far-term Industrial
boiler application
Primary titphasls near-
ter.n i.nd far-t£rM appli-
cations all sources
Secondary emphasis near-
term applications (boilers);
combined with OSC or burner
mods for far-term appl.
Primary emphasis near- and
far- term applications all
sources
LO
00

-------
                               TABLE S-4.
OVERALL EVALUATION OF NOX CONTROL TECHNIQUES FOR COMBUSTION SOURCES
Control
Technique
Water, s learn
Injection
Reducrd air
preheat (RAP)
Aramnia injection
Fuel
denltriffcatlon
Fuel additives
Alternate and
mined fuels
Existing
Appl ic.it ions
Widely used for gas
turbines
Widespread use ir.
large turbocharged
1C engines
Demonstrated on
oil* and gas-fired
Industrial boilers
Oil denUrificatlcm
accompanies rfesul-
furlwtlon for some
large boilers
Fuel additives for
HOX not used
Combustion of low
nitrogen alternate
fuels being
demonstrated
Effectiveness
301 tr. 90S for
thermal NO^
101 to 401 for
thermal N0x
40S to 70S for
thermal and fuel
N0x
10X to 40f for
fuel N0x
Generally In-
effective for dir-
ect HOX reduction
Varies
Operational
Impact
Slight decrease in
efficiency; limited
by CO formation;
power output
increases
S11(|lit decrease In
efficiency, In-
crease power output
Retrofit use lim-
ited; possible ad-
verse environmental
impact
No adverse effects
Byproduct emissions
formed
Varies
Projected
Applications
Use in new gas tur-
bines; possible use
in process furnaces
Continued use in 1C
engines, applicable
to some industrial
arid utility boilers .
Use In large
boilers In some
areas (19BO's)
Use of oil de-
nitrification in
large boilers AS
supplement^ CM
tech.
Additives for cor-
rosion, fouling,
participate, smoke,
etc. can provide
increased fl«»1-
billty with CM tech.
on large boilers
Combined cycles and
residential ami
ccnmerctal heating
sys terns
Control
Evaluation
Primary emphasis near-term
applications, gas turbines;
possible far-term indus-
trial process application
Secondary emphasis
»
Primary emphasis far-
term application to large
boilers; evaluate impact
with coal firing
Secondary emphasis; eval-
uate as alternate fuel
Secondary emphasis; con-
sider impact of additives
Secondary emphasis far- term
application; evaluate dif-
ferential impact of fuel
switching; transfer results
of other E/A's .
in
vo

-------
                              TABLE S-4.
OVERALL EVALUATION OF N0x CONTROL TECHNIQUES  FOR COMBUSTION  SOURCES  (Continued)
Control
Technique
Catalytic
combustion
Fluidized bed
coffimstion
Flue gas
treatment (FGT)
Existing
Applications -
Only tested In
experimental
combustors
Tested in pilot/
prototype
combustors
Used in Japan on
large boilers
Effectiveness
>90X for thermal
N0x
20X to 50X for
fuel NOX (pres-
surized FBC)
40X to >90t for
fuel and
thermal NO
X
Operational
Impact
Requires clean
fuel; combustors
1 imited by cata-
lyst bed temp.
capability
Requires sulfur
acceptor
Requires temp, con-
trols, catalyst,
scrubbing soTn. ,
or oxidizing agent;
possible adverse
envlronn^riUl Impact
Projected
Applications
Gas turbines and
residential and
commercial heating
sys terns
Combined cycle,
utility boilers,
industrial boilers
(1980's)
Possible supple-
ment to CM for
utility and large
industrial boilers
(1980's)
Control
Evaluation
Primary emphasis far-term
applications; compare im-
pact to burner mods, al-
ternate fuels
Transfer results from
FBC E/A; compare impact
to combustion modifications,
conventional combustion
Secondary emphasis; trans-
fer results of other
studies to compare impact
to combustion mods
I
o

-------
conditions. For utility boilers and large industrial boilers, techniques such as lowering excess
air, off-stoichiometric or staged combustion, and, for gas- and oil-fired units, flue gas recircula-
tion have resulted in NOV reductions of up to 60 percent making it possible for them to meet •
A
emissions regulations at costs typically ranging from $0.60 to $6 per kW (electric output, 1978$).
The incremental costs of new burner and enlarged furnace designs installed on new units also fall
within this range. Ongoing performance tests are investigating potential side effects of the
modifications, such as increased corrosion and particulate emissions with coal firing.

Although less well developed for most industrial boilers, some combustion modifications for
these sources are able to decrease NO by up to 50 percent with no efficiency impairment or increase
in particulate formation. The most successful techniques are.lowering excess air, staged combus-
tion, and flue gas recirculation.

The energy impacts of applying combustion modification NO controls to utility and industrial
A
boilers occur largely through the effects on unit fuel-to-steam efficiency. This is usually
expressed as an increase or decrease in fuel consumption for a constant output. Generally, low
excess air, flue gas, recirculation and off-stoichiometric combustion have very little effect on
efficiency. Low excess air controls actually improve fuel efficiency in many cases. In some cases,
taking burners out of service may result in reduced capacity. Reduced air preheat has a slight
impact, usually less than 1.5 percent increase in fuel use; although, significant reductions in air
preheat (^150-200K) can have a much greater impact (^3-4 percent increase in fuel use). New designs
should significantly reduce any adverse efficiency impacts.

Emissions of other pollutants, CO, HC, particulates, sulfates, and organics, can be altered
by the use of NOX control. Generally, these changes have been acceptable. In some cases specific
consideration of other emissions has been given in the design or method of application of the NO
control technique.

•Prime movers include stationary reciprocating internal combustion engines and gas turbines.
For the former, "dry" methods such as spark retard, air/fuel ratio change, and derating work well,
providing NOX reductions of 10 to 40 percent while fuel consumption increases 2 to 15 percent.
Water injection ("wet" control) is currently the most effective technique for gas turbines, reducing
NOX up to 90 percent at costs of 0.4 to 14 mills/kWh (1975 costs), depending on the turbine's
application. "Dry" control techniques show potential, but it will be a number of years before their
development will be complete and they will be ready to be applied to large production turbines.
S-ll

-------
The energy impacts of applying NOV control to internal combustion engines and gas turbines
X
are manifested almost exclusively through corresponding increases in fuel consumption. Since both
types fire mainly clean fuels, the impact on other emissions is confined primarily to HC, CO, and
particulates.

OTHER COMBUSTION PROCESSES
Space heating, incineration and open burning, and industrial process heating are additional
combustion sources of NO . Residential and commercial space heating contributes 5 percent of the
nation's stationary NO emissions. Emissions of CO and particulates from the major equipment types,
residential and commercial warm air furnaces, can be controlled by burner maintenance and tuning.
These techniques are not very effective for NOX reduction, however. The most promising prospect for
HO control in space heating systems is for new equipment applications. New low NO systems are
A A
available at a cost of 10 percent or more above conventional systems. These systems are capable of
reducing NO emissions by more than 50 percent, while increasing operating efficiency by more than
5 percent.

There has been negligible application of combustion modification to incineration and open
burning.

NONCOMBUSTION PROCESSES

Noncombustion-generated NO , only 1.7 percent of stationary emissions, is produced mainly
during nitric acid manufacture. NOX control methods include extended absorption, wet scrubbing, and
catalytic reduction. Catalytic reduction was initially practiced but because of catalyst costs,
fuel costs and changes in the operating conditions of nitric acid plants, greater use of the
extended absorption and wet. scrubbing processes have been employed more recently. Other minor
noncombustlon sources are mainly those that use nitric acid as a feedstock. Control methods are
similar to those used for nitric acid manufacturing, fable S-5 gives a summary of tail gas
abatement processes and applications.
S-12

-------
                                        TABLE S-5.   NOX ABATEMlNT METHODS ON NEW OR EXISTING NITRIC ACID PLANTS
Process
Chilled
Absorption
Extended
Absorption
«
Wet Chemical
Scrubbing
Method
Increased solu-
bility of NOX In
chilled water
Increased absorp-
tion of NOX by
additional ab-
sorption equip-
ment
Scrubbing tall
gases with urea
solution or
ammonia to
recover NO
Comments
Usually cannot meet
NSPS without other add-
on technology or low-
ered acid product
concentration
Inlet pressure of 760
kPa required (addi-
tional compressors
may be required)
Requires additional
compressor

Performs better at high
pressure but operable at
lower pressures. Recovers
ah.-noniuni nitrate and urea
solution. Requires re-
frigeration.
May require an evaporator
to produce a concentrated
ammonium nitrate by prod-
uct. No refrigeration
required.
Licensors
COL-VITOK
TVA
J. F. Prltchard
(Grande Paroisse)
P. M. Weatherly
Chemlco
Uhde
C&l Glrdler
CoFAZ
MASAR (urea
scrubbing)
Norsk Hydro
(urea scrubbing)
Goodpasture
(ammonia
scrubbing)
Examples
2-318 Mg/d (350 tons/day) (with Gulf cata-
lytic reduction add-on). Nltrant, Tampa. Fla.
2-50 Mg/d (55 tons/day) plants at Muscle
Shoals, (1972)
327 Mg/d (360 tons/day) plant, Miss.
Chemicals, Yazoo City, Miss. 1973.
272 Mg/d (300 tons/day) Holston Army
Ammunition Plant, Klngsport, Tenn.
Comlnco Plant, Beatrice Neb.
Kaiser. Tampa. Fia. pnq Bainbridae. Ohio
9 U.S. plants, 1 Japan plant (employs
chilled absorption process)
900 Mg/d (1000 tons/day) Monsanto,
Pensacola, Fla. 1977.
250 Mg/d (275 tons/day) plant, Allied
Chemical, Oman, Neb. 1975
None built to date
111. Nitrogen PH., Marsalles, 111.
Air Products & Chem. , Pace, Fla.
Norsk Hydro, Proggunn, Norway
90 Mg/d (100 tons/day) Goodpasture pit.,
1974. Dlnmitt, Texas
Chevron 011 Co., Richmond, Calif. 1976
C.F. Industries, Fremont, N.D.
2 scrubbers for 7 plants totalling 544
mg/d (000 tons/day),. Cyanamid, Welland, Ont.
I
_4

oj

-------
TABLE S-5. HOX ABATEMENT METHODS W HEH OR EXISTING NITRIC ACID PLANTS (Concluded)
Process
Catalytic
Nonselectlve
Catalytic
Selective
Heterogeneous
Catalysis
Chemical
Absorption
Holecul-ar
Sieve
Method
Burns NOX and 02
with Cfy or Kg to
form N2. H20, C02
Burns NO* with
ammonia to form
Ng and H20; 02
not affected '
Oxidation of NO +
N02 catalyzed by
heterogeneous ca-
talysis before
absorption
Oxidation with
KMnO^ (KMn04
electrolytlcally
reclaimed
Absorption by
molecular sieve,
regeneration of
the sieve by
thermal cycling
Conrnents
• Consumes natural gas,
uneconomical If high
NOX or 02 content
(also reacts with 02)
• May be used In con-
junction with extended
absorption
• Energy recovery
possible
• Works at low or high
pressure
• Uses ammonia, can be
expensive to operate
• Often used with ex-
tended absorption
• Works at low or high
pressure
a Energy recovery
usually not possible
* Can achieve very low
emission If desired
Limited success
Uneconomical not pres-
ently offered
o High eneryy and capi-
tal dem.tn.ls
a Hard to fit cycl Ing
of sieve Into con-
tinuous plant opera-
tion
Licensors
CM Glrdler
D. M. Weatherly
Chemlco
Gulf
Uhde (BASF cata-
lysts)
Mitsubishi
CDL/VITOK
Carus Chemical
Purasiv N
(Union Carbide)
Examples
Ol1n» Lake Charles, La. (also, Heatherby
plants)
IMC Corp., Strellngton, La. (1976) (with
extended absorption). 817 Mg/d (900 tons/
day), 1977. Columbia Nitrogen, Augusta,
Ga.
Location not available
Nltram plants 1n Tampa, Fla., Installed
after CDL/VITOK process.
10 plants 1n U.S.
Plants 1n Europe and Jap'an
Under development
2 plants 1n Jaoan, not currently offered
1n U.S.
50 mg/d (55 tons/day) Hercules, Inc.
Berseimrr, Ala. 1971
50 mg/d (6'j tons/day) U.S. Army, Hols ton, '
Kingston, Tenn. (Inoperable, disiiuntleil)
i
1
I
.£.

-------
SECTION 1
INTRODUCTION

The first edition of "Control Techniques for Nitrogen Oxide from Stationary Sources" (AP-67)
was published in March 1970 as provided by the Air Quality Act of 1967. This first edition was used
to support the National Ambient Air Quality Standards (NAAQS) for Nitrogen Dioxide as required .by
Sections 108 and 109 of the Clean Air Amendments of 1970. The first control techniques document was
updated in January 1978 to include later developments in regulatory control of NOX and emission
control techniques for stationary sources. Since the second edition, still further developments
have occurred. These developments have been largely in the field of control of NO emissions from
combustion. Consequently, the current revisions have been limited to the combustion sections
leaving the other parts of the text unchanged except for the addition of text to show the dates of
the various cost data.
The NO control technology development to support the implementation of the 1971 NAAQS
X
standards has shown widespread advancement since the publication of the original AP-67 document.
Efforts have proceeded on methods which suppress NO formation through combustion process
modification and on methods which remove NO from the flue or tail gases through stack gas
treatment. Work is continuing in these areas.
Combustion process modification is the commonly used method for control of stationary
combustion sources,accounting for 98 percent of stationary source NO control. Process
modifications have been extensively applied to retrofit of-existing utility and industrial boilers
and gas turbines firing gas and oil. The significant role of fuel-bound nitrogen in NO formation
with the firing of coal and heavy oils was shown early in the control, development effort. Current
activity is concentrating on refinement of fuel NO control methods for application to advanced
designs of coal-fired combustion equipment. Progress has also been made in the design of low-NO
residential and commercial space heating systems.
Stack gas treatment is the commonly used method for control of NO emissions from stationary
noncombustion sources. These sources, primarily nitric acid plants, contribute less than 2 percent
of nationwide stationary sources NO emissions but can present a serious local hazard. Several
control techniques, including extended absorption, catalytic reduction, wet scrubbing, and molecular
1-1

-------
sieve absorption, have been developed and implemented on existing and new equipment.   Reductions  in



NOV in excess of 95 percent have been demonstrated.
  X




       The purpose of this report is to update and revise the control techniques document issued  in



1978 by incorporating improved emissions estimates and NO  control  technology developments since



that time.  Emphasis is placed on identifying the significant stationary sources of NO  emissions,



based on the most recent EPA emissions data (Section 2); summarizing the developmental  status  of



candidate NO  control techniques (Section 3); and reviewing the effectiveness, cost and user



experience with the implementation of NOV controls on large combustion sources (Section 4), other
                                        A


combustion sources (Section 5), and noncombustion sources (Section 6).  Also included in these



sections is information on the energy and environmental impacts of the various control  techniques as



required by Section 108.(b)(l) of the Clean Air Act as amended in 1977.
       This report is concerned only with the quantifying and controlling stationary source NOV
                                                                                              A


emissions.  The effects upon health and welfare of nitrogen oxides and their secondary atmospheric



reaction products are considered in two related documents, "Air Quality Criteria for Ozone and Other



Photochemical Oxidants," (EPA-600/8-78-004) and AP-84, "Air Quality Criteria for Nitrogen Oxides."



The foregoing documents are being revised with publication scheduled within the next few months.
                                         1-2

-------
SECTION 2
CHARACTERIZATION OF NOX EMISSIONS

This section presents a nationwide inventory of emissions of oxides of nitrogen. Section 2.1
defines NO and summarizes the basis of its occurrence in stationary source combustion. Section 2.2
describes the standard EPA methosd for analysis, of source and ambient NO concentrations.
X
Section 2.3 describes specific stationary source equipment types and presents nationwide NO
emissions estimates and NO emissions factors for each source equipment type.
X

2.1 DEFINITIONS AND FORMATION THEORY

Seven oxides of nitrogen are known to occur: NO, NOg, NO,, NgO, NpO,, N-O. and NgOg. Of
these, nitric oxide (NO) and nitrogen dioxide (NO,) are emitted in sufficient quantities in fuel
<— >
combustion and chemical manufacturing to be significant in atmospheric pollution. In this document,
"NOX" refers to either or both of these two gaseous oxides of nitrogen. Nitrogen dioxide is
deleterious to human respiratory functions and is a key participant in the formation of photo-
chemical smog. Nitric oxide, taken alone, is relatively less harmful but is important as the main
precursor to NO- formation in the atmosphere.
Approximately 95 percent of oxides of nitrogen from stationary combustion sources are emitted
as nitric oxide. Two separate mechanisms, thermal NOX formation and fuel NO formation, have
been identified as generating NO during fossil fuel combustion.
Thermal NOX results from the thermal fixation of molecular nitrogen and oxygen in the combus-
tion air. ' Its rate of formation is extremely sensitive to local flame temperature and somewhat less
so to local oxygen concentrations. Virtually all thermal NO is formed at the region of the flame
which is at the highest temperature. The NO concentration is subsequently "frozen" at the level
prevailing in the high temperature region fay the thermal quenching of the combustion gases. The
flue gas NOX concentrations are therefore between the equilibrium level characteristic of the peak
flame temperature and the equilibrium 'level at the flue gas temperature. This kinetically
controlled behavior means that thermal NO emissions are dominated by local combustion conditions.
2-1

-------
Fuel NO derives from the oxidation of organically bound nitrogen in certain fuels such as
coal and heavy oil. Its formation rate is strongly affected by the rate of mixing of the fuel and
airstream in general and by the local oxygen concentration in particular. The flue gas NO concen-
tration due to fuel nitrogen is typically only a fraction (e.g.i 20 to 60 percent) of the level
which would result from complete oxidation of all nitrogen in the fuel. Thus, fuel NO formation,
like thermal NO formation, is dominated by the local combustion conditions. Additionally, fuel NO
X A
emissions are dependent on the nitrogen content of the fuel. The NO emissions characterization
detailed in this section, therefore, takes account of variations in equipment operating conditions
and 1n fuel type which influences the emissions as well as the potential for control. Additional
discussion on thermal and fuel NO formation mechanisms is given in Section 3.1.

Oxides of nitrogen emitted in the byproduct streams of chemical manufacturing (nitric acid,
explosives) are predominantly in the form of NO-. The NO- concentration in the process vents is
typically at the equilibrium level characteristic of the chemical compositions and. temperatures
required in the manufacturing process. The NO emissions from noncombustion sources are then much
X
less sensitive to minor process modifications than are combustion generated NO emissions.

2.2 SAMPLING AND ANALYSIS METHODS

The standard EPA method for compliance testing of NO from stationary sources is the phenol-
disulfonic acid (PDS) method. This method was developed for the measurement of nitrate i-n solution
by Chamot around 1910 (Reference 2-1). The specifications for the PDS method are given in
Reference 2-2. Briefly, the method requires that a grab sample be collected in an evacuated flask
containing a dilute sulfuric acid-hydrogen peroxide solution which absorbs the nitrogen oxides,
except nitrous oxide (NgO). The sample is then processed following the procedures of Reference 2-2.
The absorbence of 420 nm wavelength light by the treated samples is then measured. A calibrated
relationship between absorbence and NO, concentration is used to relate the measurement to the
sample NOg concentration.

The advantages of the PDS method include the wide concentration range, minimum number of
sample handling steps, and lack of interference with sulfur dioxide in the flue gases. The
disadvantages are the long time elapsed between samples, a possible interference from halides, and
the Inherent problems with grab sampling.
2-2

-------
Continuous type instrument methods are also used to measure NOX concentrations. The most
common type of instrument method is the chemiluminescence method. This method is described in
Reference 2-3. Performance specifications and specification test procedures for monitors of NO
A
emissions are given in Performance Specification 2, Appendix B, Part 60, Title 40, Code of Federal
Regulations.

2.3 EQUIPMENT DESCRIPTIONS, EMISSIONS ESTIMATES, AND EMISSION FACTORS BY APPLICATION SECTOR

An overview of stationary sources of NOV emissions is provided in Figure 2-1. The first
A
division is by application and the second by use sector. The six applications encompass all major
sources and the cited sectors include all those of importance within each sector. Steam generation
is by far the largest application on a capacity basis for both utility and industrial equipment
while space heating is the largest application by number of installations. Internal combustion
engines (both reciprocating and gas turbines) in the petroleum and related products industries have
generally been limited to pipeline pumping and gas compressor applications. Process heating data
are not as readily available, but the main sources appear to be process heaters in petroleum
refineries, the metallurgical industry, and the drying and curing ovens in the broad-ranging
ceramics industry. Incineration by both the municipal and industrial sectors is a small but
noticeable source, primarily in urban areas. Noncombustion sources are largely within the area of
chemical manufacture, more specifically nitric and adipic acids and explosives. The final descrip-
tion level in Figure 2-1 gives the important equipment types. Although these equipment categories
do not include all the possible variations or hybrid units, the bulk of the equipment is included in
the breakdown. ,
Table 2-1 summarizes annual nationwide emissions of nitrogen oxides from all sources for the •
period 1970 to 1980 (Reference 2-4). As shown, transportation (or mobile sources), stationary
source fuel combustion, and industrial processes are the major NO emission sources. In the
following sections, equipment descriptions, nationwide NO emissions estimates, and NOV emission
A A
factors will be presented for sources in the stationary fuel combustion and industrial processes
categories. Transportation NOX sources are not addressed in this document. .„

Particular emphasis is placed in this report on stationary fuel combustion sources because of
their large contribution to stationary source NO emissions. Table 2-2 presents a breakdown of
«
estimated 1980 nationwide NO emissions from stationary fuel combustion sources by fuel type and
consuming sector (Reference 2-4). The coal-fired electric utility sector and the gas-fired
2-3

-------
                   APPLICATION
          SECTOR
              EQUIPMENT TYPES
               -PRIME HOVER
STATIONARY
SOURCES OF
NO-
                  ,   STEAM
                   GENERATION
                                         ELEC POWER
                                         GENERATION
                                         INDUSTRIAL
                                       PROCESS STEAM
                    SPACE
                  'HEATING
 ELEC POWER GEN.
 OIL AND GAS
 PIPE LINE PUMPING
 HAT GAS PROCESSING
                                    —  RESIDENTIAL
                                   1—  COMMERCIAL

                                      -  MUNICIPAL
               — INCINERATION
L_  INDUSTRIAL.

     PETROLEUM
  "*  REFINING
                     PROCESS
                     HEATING
   METALLURGICAL
               I—NONCOMBUSTIQN
                                         CERAMICS
                                    I	  CHEMICALS
                                           GLASS
                                          BRICKS
                                          CEMENT
     CHEMICAL
   MANUFACTURING
                             FIELD ERECTED
                           WATEHTU8E BOILERS
                                              r FIS-B ERECTED
                           WATERTU8E BOILERS H
                                              L PACKAGED
                                                                  PACKAGED
                                                              FIRETUBE BOILERS
                                                              RECIPROCATING
                                                                1C ENGINES
                                                              •GAS TURBINES

                                                              . FURNACES
                         .CAST IRON BOILERS

                        ,—   BOILERS



                        —  FURNACES
                          -HATERTUBf

                            FIRETUBE

                          L.CA5T IRON
-r
PROCESS HEATERS

FLUID CATALYTIC CRACKERS
    -KEATING AND ANNEALING OVENS

    —   COKE OVEN UNOERFIRE

    —   OPEN HEARTH FURNACE

    _    S UTTERING OVENS
      .  FURTMCES

    r— MITKIC ACID

      • AOIPIC ACID

    L. EXPLOSIVES
         Figure  2-1.   Stationary sources  of NO  emissions.
                                                       *\
                                             2-4

-------
              TABLE 2-1.   NATIONAL ESTIMATES OF NITROGEN OXIDE EMISSIONS, Tg (106 Tons)/yr (Reference 2-4)
Source Category 1970
Transportation
High Vehicles 5.5(6.1)
Aircraft 0.1 0.11
Railroads 0.6 0.66
Vessels 0.1(0.11
Other Off-Highway 0.8(0.88
Vehicles
Transportation Total 7.1(7.8)
1971 1972

5.9 6.5) 6.5(7.2)
0.1 0.11) 0.1(0.11
0.6 0.66) 0.7(0.77
i 0.1 0.11) 0.1(0.11
0.8 0.88) 0.9(0.99

7.5(8.3) 8.3(9.1)
1973

6.8 7.5)
0.1 0.11
0.7 0.77
0.1 0.11
0.90.99

8.6(9.5)
1974 1975 1976 1977

6.5(7.2) 6.6 7.3) 6.9 7.6) 7.0 7.7)
0.1(0.11) 0.1 0.11) 0.1 0.11) 0.1 0.11
0.7(0.77) 0.7 0.77) 0.7 0.77) 0.7 0.77
0.1(0.11) 0.1 0.11) 0.1 0.11) 0.1 0.11
0.9(0.99) 0.9 0.99) 1.0 1.1) 0.1 1.1)

8.3(9.1) 8.4(9.2) 8.8(9.7) 8.9(9.8)
1978

7.1
0.1
0.7
0.2
1.1


7.8)
0.11
0.77
0.22
1.2)

1979 1980

6.8(7.5) 6.7
0.1(0.11) 0.1
0.8(0.88) 0.8

7.4)
0.11)
'0.88)
0.2 0.22) 0.1(0.11)
1.1(1.2) 1.0(1.1)


9.2(10.1) 9.0(9.9) 8.7(9.6)
Stationary Source Fuel Combustion
Electric Utilities 4.5(5.0)
Industrial 3.9 4.3)
4.7(5.2) 5.0(5.5)
3.8 4.2) 3.9(4.3)
5.3(5.6)
3.9(4.3)
5.3(5.8) 5.2 5.7) 5.6(6.2) 6.0 6.6)
3.7(4.1) 3.4 3.7) 3.7 4.1) 3.7 4,1)
5.9(6.5}
3.7(4.1)
6.2(6.8) 6.4
3.5(3.9) 3.0
Comnercial- 0.3 0.33) 0.3 0.33) 0.3(0.33) 0.3(0.33) 0.3(0.33) 0.3 0.33) 0.3 0.33) 0.3 0.33) 0.3(0.33) 0.3(0.33) 0.3
Institutional

Residential 0.4(0.44) 0.4(0.44) 0.4(0.44
Fuel Combustion Total 9.1(10)
9.2(10.1) 9.6(10.6





7.0)
3.3)
0.33)

0.4(0.44) 0.4(0.44) 0.4(0.44) 0.4(0.44) 0.4(0.44) 0.4(0.44) 0.4(0.44) 0.3(0.33)
' 9.9(10.9) 9.7(10.7) 9.3(10.2) 10.4(11.4) 10.0(11 .0)
10.3(11.3) 10.4(11.4) 10.0(11)
Industrial Processes 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77) 0.7(0.77)
Solid Haste Disposal
Incineration 0.1 0.11
Open Burning 0.3 0.33
Solid Haste Total 0.4 0.44
liscellaneous
Forest Fires 0.2 0.22
Other Burning 0.1 0.11
Misc. Organic 0.0 0)
Solvent

0.1(0.11) 0.1(0.11
0.20.22) 0.1(0.11
0.3 0.33) 0.2(0.22


0.0(0)
0.1 0.11
0.1 0.11


0.0(0) 0.0(0) 0.0 0) 0.0 0)
0.1(0.11) 0.1 0.11) 0.1 0.11) 0.1 0.11
0.1(0.11) 0.1 0.11) 0.1 0.11) 0.1 0.11



0.0(0)


0.0(0) 0.0(0)
0.1(0.11) 0.1(0.11) 0.1(0.11)
0.1(0.11) 0.1(0.11) 0.1(0.11)




0.2(0.22) 0.2(0.22) 0.1(0.11) 0.2(0.22) 0.1(0.11) 0.2(0.22) 0.2(0.22) 0.2(0.22) 0.2(0.22) 0.2(0.22)
0.1(0.11) 0.1(0.11) 0.0 0)
0.0 0) 0.0(0) 0.0 0)


0.0(0) 0.0(0) 0.0(0) 0.0 0)
0.0(0) 0.0(0) 0.0(0) 0.0 0)

0.0(0)
0.0(0)


0.0(0) 0.0(0)
0.0(0) 0.0(0)


Miscellaneous Total 0.3(0.33) 0.3(0.33) 0.3(0.33) 0.1(0.11) 0.2(0.22) 0.1(0.11) 0.2(0.22) 0.2(0.22) 0.2(0.22) 0.0(0.22) 0.2(0.22)
Total of All 17.6(19.4) 18.0(19.8) 19.1(21.0) 19.4(21.3) 19.0(20.9) 18.6(20.5) 19.8(21.8) 20.3(22.3) 20.5(22.6) 20.4(22.4) 19.7(21.7)
Categories







ro
i

-------
               TABLE 2-2.  1980 NITROGENOXIDE EMISSIONS  FROM FUEL COMBUSTION IN STATIONARY SOURCES
                                BY CATEGORY FOR MAJOR FUELS, 103 tons  ) (Reference 2-4)
Fuel Type

Anthracite Coal
Bituminous Coal
Residual Oil
Distillate Oil
Natural Gas
Wood
Kerosene
LPG
Coke
Coke-Oven Gas
Bagasse
TOTAL
Electric
Utility

8.6 (9.5)
5149.4 (5664)
405.5 (446)
38.2 (42)
775.3 (853)
0.0 (0)
0.0 (0)
0.0 (0)
0.0 (0)
0.0 (0)
0.0 (0)
6377.0 (7015)
Industrial

4.8 (5.3),
398.6 (438)
162.3 (179)
57.4 (63)
2239.7 (2464 )a
35.1 (39)
11*4 (12.5)
32.6 (36)
16.5 (18.2)
5.0 (5.5)
5.2 (5.7)
2968.6 (3265)
Commercial-
Institutional

2.2 (2.4)
14.8 (16.3)
103.9 (114)
37.1 (41)
118.4 (130)
0.0 (0)
0.0 (0)
0,0 (0)
O.Q (0)
0.0 (0)
0.0 (0)
276.4 (304)
Residential

1.5 (1.7)
3.0 (3.3)
0.0 (0)
77.0 (85)
215.5 (237)
6.8 (7.5)
9.6 (10.6)
17.5 (19.3)
Q.O (0)
0.0 (0)
0.0 (0)
330.9 (364)
Total

17.1 (18.8)
5565.8 (6122)
671.7 (739)
209.7 (231)
3348.9 (3684)
41.9 (46)
21.0 (23)
50.1 (55)
16.5 (18.2)
5.0 (5.5)
5.2 (5.7)
9952.9 (10,948)
..                  33
 Includes 1884 x 10  Mg (2072 xv!0  tons) from  stationary internal  combustion engines and gas turbines.

-------
industrial sector are the major emission sources in the fuel combustion category. In Section 2.2.1
the operations of the boiler sources in the fuel combustion category are described and NO emission
factors are presented for the various equipment types within each use sector.

In Section 2.3.2 the operations of the sources that constitute the industrial processes
category are briefly discussed. Nationwide NO emissions estimates for 1980 and NO emission
factors are presented for each major Industrial source. Section 2.3.3 presents nationwide emissions
estimates and emission factors where available for the minor industrial process sources of nitrogen
oxides. The nationwide NOX emissions estimates are. derived from unpublished data collected by the
Monitoring and Data Analysis Division (MDAD) of EPA. The NO emission factors were obtained from
the EPA publication AP-42 (Reference 2-5) and its six supplements (References 2-6 to 2-11).

2.3.1 Stationary Fuel Combustion Sources

2.3.1.1 Utility Boilers

Most of the nation's electricity is generated in large fossil fueled central station power
plants, which primarily consist of high-pressure field-erected watertube boilers in the 100 to
1300 MW range serving turbine generators. On a thermal input basis, these boilers range in
capacity from about 300 to 3700 MW (1,000 to 13,000 x 10 Btu/hr). Industrial electric generating
boilers will generally be smaller than the sizes identified in this range as indicated in the next
subsection. Field-erected watertube boilers operate at steam temperatures up to 570°C (1050°F) and
steam pressures up to 26 MPa (3800 psi). Depending upon manufacturer, units greater than about
2250 MW (7700 x 10 8tu/hr) thermal input operate at supercritical steam pressures above 24 MPa
(3500 psi) (Reference 2-12). In general, utility boiler thermal efficiencies range up to 90 percent
of the heat liberated during fuel combustion. Approximately half of this heat energy is absorbed by
radiant heat transfer to the furnace walls. However, because of the various thermodynamic cycle and
mechanical losses, total power plant fuel-to- electric efficiencies are considerably lower, around
34 to 38 percent.

Although there are some differences among utility boiler designs in such factors as furnace
volume, operating pressure, and configuration of internal heat transfer surface, the principle
distinction is firing mode. This includes the type of firing equipment, the fuel handling system,
and the placement of the burners on the furnace walls. The major firing modes are: single- or
opposed-wall-fired, tangentially-fired, turbo-fired, and cyclone-fired. Vertically-fired units and
2-7

-------
stoker units are used to a small extent in older steam generating stations. All of the major firing
types can be designed to burn fossil fuels - gas, oil and coal, either singly or in combination.
However, the cyclone unit is primarily designed to fire coal as the principal fuel. All of the
coal-fired units use pulverized coal except for the cyclone units which use crushed coal and the
stokers which accept' lumps of coal.

In addition to differences in firing mode, coal, depending on its ash characteristics, is
burned in either a dry-bottom or wet-bottom (slag tap) furnace. Dry-bottom units operate at
temperatures below the ash-fusion temperature, and ash is removed as a solid. For wet-bottom
furnaces the ash is removed as a molten slag through a bottom tap. Although wet bottom units were
once used extensively in burning low ash-fusion temperature coals, they are less frequently used due
to operational problems with low sulfur coals and because their high combustion temperatures promote
HOV formation.
A
In single-wall firing (front-wall) burners are mounted normal to a single furnace wall.
Furnace wall area generally limits the capacity of these units to about 1200 MW (4100 x 10 Btu/hr)
thermal input. When greater capacity is required, horizontally opposed-wall firing furnaces are
normally used. In these units burners are mounted on opposite furnace*walls. Generally, capacities
for these units exceed 1200 MW thermal input (Reference 2-12). Burners on the single-wall and
opposed-wall firing designs are usually register type where fuel and combustion air are combined in
the burner throat.

Turbo-fired units are similar to the horizontally opposed-wall-fired units except that
burners are mounted on opposed, downward inclined furnace walls. Fuel and combustion air are
introduced into the combustion zone where rapid mixing occurs.
In tangential firing, arrays of fuel and air nozzles are located at each of the four corners
of the combustion chamber. Each nozzle is directed tangentially to a small firing circle in the
center of the chamber. The resulting spin of the four "flames" creates sufficient turbulence for
thorough mixing of fuel and air in the combustion zone.

In the cyclone furnace design fuel and air are introduced circumferentially into a water-
cooled, cylindrical combustion chamber to produce a highly swirling, high temperature flame. The
cyclone was originally developed as a slagging furnace to burn low ash-fusion temperature coals, but
has recently been used successfully on lignite. Relatively high levels of thermal NOX formation
accompany the high temperatures of slagging operation. Due to the inability of this design to
readily adapt to low NO operation, this type of furnace is no longer being constructed.
2-8

-------
Vertical-firing furnaces were developed for pulverized fuels prior to the advent of water-:
walled chambers. These units provide a long-residence time combustion which efficiently burns
low-volatile fuels such as anthracite. Vertical-fired boilers are no longer sold, and relatively
few of these units are found in the field.

Stoker-fired units are designed for solid fuel firing. Unlike liquid, gaseous or pulverized
fuels which are burned in suspension, the stoker employs a fuel bed. This bed is either a
stationary grate through which ash falls or a moving grate which dumps the ash into a hopper. The
main types of stokers are overfeed and underfeed designs. Spreader stokers are overfeed designs and
distribute the fuel by pneumatically or mechanically projecting the fuel into the furnace where it
falls evenly over the fuel bed. Other overfeed stokers generally deposit fuel on a continuously
moving grate. Underfeed designs introduce fuel beneath the fuel bed. Ash is pushed aside by the
newly introduced fuel.

Tangential firing, single-wall and horizontally opposed-wall firing, and turbofurnace firing
accounted for about 40 and 36 and 14 percent of the fuel consumed by utility boilers in the
mid-1970s (Reference 2-13). t In terms of numbers of units, their distribution was estimated at 19,
59 and 8 percent, respectively. Cyclone, vertical and stoker designs make up the remainder of
utility units.

Recent trends indicate a continued strong movement toward pulverized coal-fired boilers.
Many previously ordered oil-fired units are being converted to coal firing during the design phase.
Historically, the trend was toward increasing unit capacities. However, this appears to have slowed
in recent years with many utilities electing to install two small boilers rather than a single
larger unit (Reference 2-12).

Nationwide NOX emissions estimates for 1980 from electric utility boilers are shown in
Table 2-2 according to the type of fuel consumed (Reference 2-4). Tables 2-3 to 2-7 present NO
• X
emission factors that are applicable to utility boilers burning coal, oil, and gas
(Reference 2-11). For utility boilers Figure 2-2 should be used in conjunction with Table 2-7 to
determine NOX emissions from natural gas combustion at reduced boiler loads.
2-9

-------
      TABLE 2-3.  NITROGEN OXIDE EMISSION FACTORS FOR BITUMINOUS AND
                  SUB-BITUMINOUS COAL COMBUSTION3, (Reference 2-11)
     Firing Configuration
        NOX Emission Factors
                                        kg/Mg of
                                      coal burned
                       (Ib/ton of
                        coal  burned)
Pulverized Coal Fired

     Dry bottom
     Wet bottom
Cyclone Furnace6
Spreader Stoker

    "Uncontrolled
     With flyash reinjection
     No flyash reinjection


Overfeed Stdkerd'f

     Uncontrolled
     After multiple cyclone


Underfeed Stoker9

     Uncontrolled
     After multiple cyclone


Handfired Units
 10.5 [7.5]c
 17
18.5
  7
  7
  7
  3.25
  3.25
  4.75
  4.75
  1.5
 21)  ([15])
181
 37
(14)
(14)
(14)
(7.5)
(7.5)
(9.5)
(9.5)
(3)
 Factors represent uncontrolled emissions unless otherwise specified.

 Total nitrogen oxides expressed as N02.  To express these factors as NO,
 multiply by a factor of 0.66.  All factors represent emissions at 60 to
 110% load conditions.

cBracketed value is for tangentially fired units.

 Includes traveling grate, vibrating grate, and chain grate stokers.

eUsed primarily in utility and large industrial applications.

 Used primarily in large commercial and general industrial applications.

9Used primarily in commercial and domestic applications.
                                     2-10

-------
         TABLE 2-4.   NITROGEN OXIDE EMISSION FACTORS FOR ANTHRACITE
                     COAL COMBUSTION WITHOUT CONTROL EQUIPMENT,
                     (Reference 2-11)
Type of Boiler
NOV Emission
A
kg/Mg of
coal burned
Factors
(Ib/ton of
coal burned)

Pulverized Coal Fired
Traveling Grate Stoker
Handfired Units
9
5
1.5
(18)
(10)
(3)
          TABLE 2-5.   NITROGEN OXIDE EMISSION FACTORS FOR LIGNITE
                      COMBUSTION WITHOUT CONTROL EQUIPMENT,
                      (Reference 2-11)
Type of Boiler


NOV Emission
A
kg/Mg of
fuel burned
Factors9
(Ib/ton of
fuel burned).

Pulverized Coal Fired
Dry Bottom
Front Wall or Horizontally
Opposed Wall
Tangential
Cyclone Furnace
Spreader Stoker
Other Stokers
6b

7
~
(4)
8.5
3
3
(12)b

(14)

(8)
(17)
( 6)
(6)
 Total  nitrogen oxides expressed as N09.
h
 Nitrogen oxide emissions may be reduced  by 20 to 40 percent with low
 excess air firing and/or staged combustion in. front fired and opposed  wall
 fired units and cyclones.
                                    2-n

-------
         TABLE 2-6.  NITROGEN OXIDE EMISSION FACTORS FOR FUEL OIL
                     COMBUSTION WITHOUT CONTROL EQUIPMENT,
                     (Reference 2-11)
          Boiler Type
   NO.. Emission Factors
                                        kg/10-3 liters
                                        of oil burned
                  (lb/103 gal of
                   oil burned)
UTILITY BOILERS - Residual Oil1

     Tangentially fired
     Vertical fired
     All others

INDUSTRIAL BOILERS

     Residual Oil
     Distillate Oil
                                          5
                                         12.6
                                          8
                                          6.61
                                          2.4
                     (42)
                    (105)
                     (67)
                     (55)c
                     (20)
COMMERCIAL BOILERS

     Residual Oil
     Distillate Oil
6.6
2.4
                                                                (55)
                                                                (20)
RESIDENTIAL FURNACES

     Distillate Oil
2.2
                                                               (18)
aTotal nitrogen oxides expressed as N02.
bFactors are for boilers at full load and normal ( 15%) excess air.  Several
 combustion mod.ifications can be employed for NO  reduction: (1) limited
 excess air can reduce NO  emissions 5-20%, (2) Staged combustion 20-40%,
 (3) using low NO  burners 20-50%, and  (4) ammonia injection can reduce NO
 emissions 40-70% but may increase emissions of ammonia.  Combinations of
 these modifications have been employed for further reductions in certain
 boilers.
GNitrogen oxides emissions from residual oil combustion in industrial and
 commercial boilers are strongly related to fuel nitrogen content, estimated
 more accurately by the empirical relationship:   ,                  ?
     kg N0?/103 liters = 2.75 + 50 (Mr [lb NO?/10J gal = 22 + 400(NT]
     where N is the weight % of nitrogen in the oil.  For residual oils
     having high ( Q.5 weight %) nitrogen content, use 15 kg N02/10  liter
     (120 Ib N02/10d gal) as an emission factor.
                                    2-12

-------
          TABLE 2-7.   NITROGEN OXIDE EMISSION FACTORS FOR NATURAL
                      GAS COMBUSTION WITHOUT CONTROL EQUIPMENT,
                      (Reference 2-11)
Furnace Type
NO Emission
kg/106 m3 of
gas burned
Factors3
(lb/106 ft3 of
gas burned)

Utility Boilers
Industrial Boilers
Domestic and Commercial Boilers
8800b
2240
1600
(550)b
(140)
(100)
 Total nitrogen oxides expressed as N02.  Test results indicate that 95 wt.
 percent of NO  is NO.

bUse 4400 kg/106 m3 (275 lb/106 ft3) for tangentially fired units.  At
 reduced loads, multiply this factor by the load reduction coefficient given
 in Figure 2-2.
                                    2-13

-------
   u
   1.0
UJ

g

u.
UJ
o
u
0.8






0.6





0.4






0.2
5
§
o
     40
               60
        80


LOAD, percent
100
110
    Figure 2-2.   Load reduction coefficient as  a

                  function  of boiler  load.

                  (Reference 2-11).
                             2-14

-------
2.3.1.2 Industrial Boilers

This equipment category is comprised of industrial boilers ranging in capacity up to 250 MM
thermal input (850 x 10 Btu/hr). Industrial boilers are either field-erected or packaged units.
The field-erected units are typically the units larger than 45 MW (150 x 10 Btu/hr) and are quite
similar in design and size to small utility boilers. Field erected boilers are typically of the
watertube design. Packaged boilers, which are equipped and shipped from the factory complete with
fuel burning equipment, are mainly watertube and firetube designs. Other designs such as cast iron,
and shell type are also used in packaged designs. Each of these designs has a fairly distinct
capacity range. Packaged boilers far out-number field- erected units, but their combined fuel
consumption is less than that of field-erected boilers.

In watertube boilers, hot gases pass over tubes which are water or steam filled. The tubes
line the combustion chamber walls and gain heat mainly by radiative heat transfer from the flame.
Downstream the combustion chamber heat is absorbed convectively with tubes mounted across the hot
gas flow. Almost all package boilers greater than about 8.8 MW (30 x 10 Btu/hr) are watertube
boilers.

Population statistics for 1977 indicate that 74 percent of the industrial boiler capacity was
composed of watertube boilers and the remaining 26 percent were predominantly firetube boilers. Of
the watertube boilers burning fossil fuels, 43 percent were predominately natural gas-fired,
32 percent were predominately oil-fired, 15 percent were stoker coal-fired, and 10 percent were
pulverized coal-fired. Less than 5 percent of the industrial boiler capacity is supplied by
non-fossil fuel-fired boilers.
In firetube boilers hot gases are directed from the combustion chamber through tubes which
are submerged in water. Firetube boilers generally burn fuel oil and natural gas because the design
is particularly sensitive to fouling with ash-containing fuels. Natural gas and distillate oil are
the main fuels for the smaller watertube units. All fossil fuels are represented in the large
watertube industrial boiler category., Recent sales statistics indicate that the firetube has
diminished in sales in the past few years (Reference 2-14).
/
Nationwide NO emissions estimates for 1980 from industrial boilers are shown in Table 2-2
according to the type of fuel consumed (Reference 2-4). Tables 2-3, 2-4, and 2-5 present NO
emissions factors that are applicable to industrial boilers burning coal. Tables 2-6, 2-7, and 2-8
present NO emissions factors for industrial boilers burning oil, gas, and liquefied petroleum gas
(LPG), respectively. Emission factors for NO from industrial boilers burning wood waste and
bagasse are presented in Tables 2-9 and 2-10 (References 2-5 and 2-11).
2-15

-------
            TABLE 2-8.  NITROGEN OXIDE EMISSION FACTORS FOR LPG
                        COMBUSTION WITHOUT CONTROL EQUIPMENT*,
                        (Reference 2-11)
          Type of Source                     NOX Emission Factors

           and Fuel                     kg/103 liter of     (lb/103 gal of
                                        LPG burned           LPG burned)
Industrial Process Furnaces

     Butane                             '    1.58                (13.2)
     Propane                                1.49                (12.4)


Domestic and Commercial Furnaces

     Butane                 >                1.13                ( 9.4)
     Propane                                1.05                ( 8.8)
aLPG emission factors calculated assuming emissions are the same, on a heat
 input basis, as for natural gas combustion.

 Nitrogen oxides expressed as NOg.


         TABLE 2-9.  NITROGEN OXIDE EMISSION FACTORS FOR WOOD/BARK
                     WASTE COMBUSTION WITHOUT CONTROL EQUIPMENT,
                     (Reference 2-11)
Type of Source NOX Emission
kg/Mg of
fuel burned
Factors3
(Ib/ton of
fuel burned)

Industrial Boilers 0.7
(1.5)
aNitrogen oxides expressed as N02-
                                     2-76

-------
   TABLE 2-10.  NITROGEN OXIDE  EMISSION  FACTORS  FOR  BAGASSE  COMBUSTION
                WITHOUT CONTROL EQUIPMENT,  (Reference  2-11)
         Type of Source                     NOV Emission Factors
                                                  ,3
                                       g/kg (Ib/KHb) of  kg/Mg  (Ib/ton).
                                       steam generated     of fuel  burned
         Bagasse Boiler                  0.3 (0.3)           0.6  (1.2)
Emission factors are expressed in terms of the amount of steam produced.
These factors should be applied only to that fraction of steam resulting
from bagasse combustion.
Emissions are expressed in terms of wet bagasse, containing approximately
50 percent moisture, by weight.  About 2 kg (4.4 Ib) of steam are produced
from 1 kg (2.2 Ib) of wet bagasse.
                TABLE 2-11.  NITROGEN OXIDE EMISSION FACTORS
                             FOR RESIDENTIAL FIREPLACES,
                             (Reference 2-5)
               Fuel Type                      NO   Emission  Factors

                                        kg/Mg of            (Ib/ton of
                                        fuel  burned           fuel  burned)
              Wood                        0.5                    (1)


              Coal                        1.5                    (3)
                                    2-17

-------
2.3.1.3 Commercial and Residential Space Heating
This category is made up of commercial and residential warm air furnaces and boilers. Warm
air furnaces are subdivided into space heaters, where the unit is located in the room which it
heats, and central heaters which use ducts to transport and discharge warm air into the heated
space. Space heaters comprise less than 10 percent of the nation's heaters. Central heaters make up
the remainder of the warm air heater equipment sector. Combustion products pass through flue gas
passages of the heat exchanger and exit through a flue to the atmosphere. Boilers used for
residential space heating are generally cast iron desigps. Residential warm air furnaces and cast
iron boilers are available in sizes up to 0.12 MW (4 x 10 Btu/hr). Larger units are mainly
confined to the commercial and institutional sector.

Commercial and institutional systems are used for space heating and hot water generation.
The equipment consists mainly of gas- and oil-fired warm air furnaces and firetube boilers. The
rated heat input, or fuel consumption, of this equipment ranges from 0.12 MW (4 x 10 Btu/hr) to
3.6 MW (12.5 x 106 Btu/hr).
Fuels burned for residential and cnmmercial space heating are primarily natural gas and
distillate oil and much smaller amounts of coal, residual oil, LPG, and wood. Nationwide NO
emissions estimates for 1980 from commercial and residential combustion sources are given in
Table 2-2 according to the type of fuel burned (Reference 2-4). Emission factor data for NO
emissions from commercial and residential sources are presented in Tables 2-3, 2-4, 2-6 to 2-8, and
2-11.
2.3.1.4 Internal Combustion Sources
*
This stationary fuel combustion subcategory consists of stationary reciprocating internal
combustion engines and gas turbines. Nationwide NOV emissions for these two sources in 1980 were
i\
"3 3
estimated to be 1884 x 10 Mg (2072 x 10 tons) as shown in Table 2-2. Equipment descriptions and
N(L emission factors for the internal combustion engine and gas turbine sources are presented in the
following sections.

2.3.1.4.1 Stationary Reciprocating Internal Combustion Engines. Reciprocating 1C engines
for stationary applications range in capacity from 15 kW (20 hp) to 37 MW (50,000 hp). These
engines are either compression ignition (CI) units fueled by diesel oil or a combination of natural
gas and diesel oil (dual), or spark ignition (SI) fueled by natural gas or gasoline.
2-18

-------
Stationary reciprocating 1C engines use two methods to ignite the fuel-air mixture in the
combustion chamber. In CI engines, air is first compression heated in the cylinder, and the diesel
fuel is injected into the hot air where ignition is spontaneous. In SI engines, combustion is spark
initiated with the natural gas or gasoline being introduced either by injection or premixed with the
combustion air in a carburetted system. Either 2- or 4-stroke power cycle designs with various
combinations of fuel charging, air charging, and chamber design are available.
* •
Because reciprocating 1C engine installations characteristically have a low physical profile
(low buildings, short stacks, and little visible emissions), they are frequently located in or
adjacent to urban centers where power demands are greatest and pollution problems most acute. These
units are used in a variety of applications because of their relatively short construction and
installation time and the fact that they can be operated remotely. Applications range from shaft
power forjarge electrical generators to small air compressors and welders.

Table 2-12 presents NOV emission factors for a heavy-duty, stationary reciprocating internal
/\
combustion engine that is firing natural gas. These types of engines are generally used to power
pipeline compressors. Emission factors are presented in terms of gas flow and in terms of energy
produced (Reference 2-5). NOX emission factors for large bore diesel and dual fuel engines are
given in Table 2-13 (Reference 2-11).

2.3.1.4.2 Gas turbines. Gas turbines are rotary internal combustion engines fueled by
natural gas, diesel or distillate fuel oils, and occasionally residual or crude oils. These units
range in capacity from 30 kW (40 tip) to over 74 MW (100,000 hp) and may be installed in groups for •
larger power output. The basic gas turbine consists of a compressor, combustion chambers, and a
turbine. The compressor delivers pressurized combustion air to the combustors at compression ratios
of up to 20 to 1. Injectors introduce fuel into the combustors and the mixture is burned with exit
temperatures up to 1090°C (2000°F). The hot combustion gases are rapidly quenched by secondary
dilution air and then expanded through the turbine which drives the compressor and provides'shaft
power. In some applications, exhaust gases are also expanded through a power turbine.
•
While simple-cycle gas turbines have only the three components described above, regenerative-
cycle gas turbines also use hot exhaust gases (430 to 590°C, 800 to 1100°F) to preheat the inlet air
between the compressor and the combustor. This makes it passible to recover some of the thermal
energy in the exhaust gases and to increase thermal efficiency. A third type of turbine is the
combined-cycle gas turbine. The combined-cycle turbine is basically a simple- cycle unit which
2-19

-------
        TABLE 2-12.  NITROGEN OXIDE EMISSION FACTORS FOR HEAVY-DUTY,
                     NATURAL GAS-FIRED PIPELINE COMPRESSOR ENGINES
                     WITHOUT CONTROL EQUIPMENT, (Reference 2-5)
          Source                        NO  Emission Factors3

                              g/kWh (lb/10* hph)     kg/106 sera (lb/106 scf)c
Reciprocating Internal
Combustion Engine                  Ib (24)               55,400 (3,400)
aTotal nitrogen oxides expressed as NO?.
u                                     £
 These factors are for compressor engines operated at rated load.  In
 aeneral, NO  emissions will increase with  increasing load and intake
 (manifold) air temperature and decrease with increasing air-fuel ratios
 (excess air rates) and absolute humidity.

cThese factors calculated from the energy-based factors for reciprocating
 engines assuming a hea.ting value of 41 MJ/scm  (1100 Btu/scf) for natural
 gas and an average fuel consumption 10.6 MJ/kWh (7500 Btu/hph).
                                      2-20

-------
            TABLE 2-13.  NITROGEN OXIDE EMISSION FACTORS FOR
                         STATIONARY LARGE BORE DIESEL AND DUAL
                         FUEL ENGINES WITHOUT CONTROL EQUIPMENT,
                         (Reference 2-11)
          Engine Type
                         NO  Emission Factors3
                           A
Diesel

g/hph
(lb/103 hph)
(lb/103 gal)h

Dual Fuel

g/hph
(lb/103 hph)
                                             11

                                            (24)

                                             60

                                           (500)




                                              8

                                            (18)
 Total  nitrogen oxides expressed as N02.   Factors are for engines
 operated at rated load and speed.

JThese  factors  calculated from the  above  factors assuming a heating
 value  of 40 MJ/liter (145,000 Btu/gal)  for oil, 41 MJ/scm (1100 Btu/scf)
 for natural  gas,  and an average fuel  consumption of 9.9 MJ/kWh
 (7000  Btu/hph).
                                    2-21

-------
exhausts to a waste heat boiler to recover thermal energy from the exhaust gases. In some cases,
the waste heat boiler is also designed to burn additional fuels to supplement steam production, a
process which is referred to as supplementary firing.

Gas turbines have been extremely popular in the past decade because of the relatively short
construction lead times, low cost, ease and speed of installation, and low physical profile (Idw
buildings, short stacks, little visible emissions). In addition, features like remote operation,
low maintenance, high power-to-weight ratio, and short startup time have added to their popularity.
Primary applications of gas turbines include electricity generation (peaking and caseload), pumping,
gas compression, standby electricity generation, and miscellaneous Industrial uses.

National NOV emissions estimates for gas turbines and internal combustion engines combined
X - .
are presented in Table 2-2.- NOX emission factors for two uses of gas turbines are presented in
Tables 2-14 and 2-15. Table 2-14 presents NO emission factors for electric utility turbines, while
X
Table 2-15 gives factors for NO emissions from gas turbines used to power pipeline compressors
(Reference 2-6).

2.3.2 Industrial Process Heating

Significant quantities of fuel are consumed by industrial process heating equipment in a wide
variety of industries, including iron and steel production, glass manufacture, petroleum refining,
chemical manufacturing, cement manufacture, and brick and ceramics manufacture. In addition, there
are dozens of industrial processes that burn smaller amounts of fuel, such as coffee roasting, drum
cleaning, painting curing ovens, and metal ore smelting, to name only a few. Brief process
descriptions for some of the more significant NO emission sources are given in the following
paragraphs. Where available, national NO emissions estimates and NOV emission factors are
X X
presented for the process heating categories. NO emissions from the industrial process equipment
sector are the most difficult to quantify of all stationary sources. This is largely due to the
extreme diversity of equipment types currently in use. Nationwide NO emissions estimates for the
X
more significant industrial processes over the period 1970 to 1980 are presented in Table 2-16
(Reference 2-4).
2-22

-------
        TABLE 2-14.  COMPOSITE NITROGEN OXIDE  EMISSION  FACTORS  FOR
                     THE  1971 POPULATION OF  ELECTRIC UTILITY TUR-    .
                     BINES  WITHOUT  CONTROL EQUIPMENT,  (Reference  2-6)
Emission Factor Basis                       -NO  Emission Factor
Time Basis
     Entire population
       kg (lb)/hr rated loada                   4.01  (8.84)

     Gas-fired only
       .kg (lb)/hr rated load*                   3.54  (7.81)

     Oil-fired only
       kg (lb)/hr rated load*                   4.35  (9.60)
Fuel Basis
     Gas-fired only

       kg/105 m3 (lb/106 ft3) gas               6615  (413)

     Oil-fired only

       kg/103 liter (lb/103 gal) oil            8.13 (67.8)
aRated load expressed in megawatts.
                                      2-23

-------
       TABLE 2-15.  NITROGEN OXIDE  EMISSION  FACTORS FOR HEAVY-DUTY,
                    NATURAL GAS-FIRED PIPELINE COMPRESSOR GAS
                    TURBINE ENGINES WITHOUT  CONTROL EQUIPMENT,
                    (Reference 2-6)
                                   NO  Emission Factors3
Source                      g/fcWh (lb/103 hph)    kg/106 son (lb/106 scf)c
Gas Turbines                  1.7   (2.9)            4,700     (300)
aTotal nitrogen oxides expressed as N09.
L                                     f-
 These factors are for compressor engines operated at rated load.  In >
 general, NO  emissions will increase with increasing load and intake
 (mantifold) air temperature and decrease with increasing air-fuel ratios
 (excess air rates) and absolute humidity.

°These factors are calculated from the energy-based factors for gas
 turbines by assuming a heating value of 41 MJ/scm (1100 Btu/scf) of
 natural gas and an average fuel consumption of 14.1 MJ/kWh (10,000 Btu/hph)
                                    2-24

-------
                      TABLE 2-16.   NATIONWIDE NITROGEN OXIDE EMISSIONS ESTIMATES  FROM MAJOR

                                   INDUSTRIAL PROCESS SOURCES, 1970-1980, (Reference 2-4)
Source Category

Pulp Mills
Organic
Chemicals
Manufacturing
Ammonia
Production
Nitric Acid
Production
Petroleum
Refining
Glass
Manufacturing
Cement
Manufacturing
Iron & Steel
TOTAL
NOV Emissions, Gg (103 tons)/yr
1970 1972 1974 1975 x 1976 1977 1978 1979 1980

20(22)
60(66)
40(44)
150(165)
220(242)
40(44) '
90(99)
70(77)
690(759)

30(33)
60(66)
40(44)
140(154
230(253)
50(55)
100(110)
70(77)
720(792)

30(33)
60(66)
40(44)
130(143)
240(264)
50(55)
100(110)
80(88)
730(803)

20(22)
60(66)
40(44)
110(121)
240(264)
50(55)
80(88)
70(77)
670(737)

30(33)
50(55)
40(44)
110(121)
240(264)
50(55)
90(99)
70(77)
680(748)

30(33)
50(55)
50(55)
100(110)
260(286)
60(66)
100(110)
80(88)
720(792)

30(33)
50(55)
40(44)
100(110)
260(286)
60(66)
100(110)
80(88)
720(792)

30(33)
60(66)
50(55)
100(110)
250(275)
60(66)
100(110)
70(77).

30(33)
40(44)
50(55)
100(110)
240(264)
50(55)
90(99)
60(66)
1
720(792) 1 660(726)
ro
i
IVJ
01

-------
2.3.2.1 Iron and Steel Industry
The iron and steel industry is one of the major contributors to combustion-related process ,
NO emissions. The most important combustion processes are sinter lines, coke ovens, open hearth
A
furnaces, soaking pits and reheat furnaces. The remaining combustion-related processes
(palletizing, heat treating, and finishing) are less important because they use relatively small"
amounts of fuel (Reference 2-15).

Sintering machines are used to agglomerate ore fines, flue dust, and coke breeze for charging
of a blast furnace. The use of this operation is presently declining because of its inability to
accommodate rolling mill scale which is contaminated with rolling oil.

Coke ovens produce metallurgical coke from coal by the distillation of volatile matter,
thereby producing coke oven gas. The fuels commonly used in this process are coke oven gas and
blast furnace gas. Although NO emissions are minimized by slow mixing in combustion chambers, they
X
are nonetheless substantial because of the very large quantity of fuel consumed in this process.

Open hearth furnaces are now being replaced in the U.S. steel industry by the basic oxygen
furnace, however, they are still an important source of NO emissions because of the very high
combustion air preheat temperature, the high operating temperatures, and the practice of oxygen
lancing.
Soaking pits and reheat furnaces are used to .heat steel billets and ingots to correct working
temperatures prior to forming. Current trends are toward continuous casting of molten metal, and
the need for the soaking and reheat units is being reduced. At present, however, soaking pits and
reheating furnaces still consume more fuel than any other single process in the steel industry. In
spite of the fact that soaking pits and reheat furnaces are being phased out, consumption of process
fuel continues to increase in the iron and steel industry as a whole.

Tables 2-17 to 2-19 present NOV emission factors for the various emission sources within the
A
Iron and steel industry. Table 2-17 presents emission factors for the coking process. Table 2-18
gives NO emission factors that are applicable to gray iron furnaces. NOV emission factors for steel
A A
foundry operations are presented in Table 2-19. All NO emission factors for iron and steel
processes were obtained from Reference 2-9.
2-2fr

-------
      TABLE  2-17.   NITROGEN OXIDE EMISSION FACTORS FOR COKE MANUFACTURE
                   WITHOUT CONTROL EQUIPMENT, (Reference 2-9)
     Type of Operation                 'NO  Emission Factors3
                                   kg/Mg of            (1b/ton of
                                   coal charged         coal charged)
     Coal Charging                    0.015               (0.03)


     Door Leaks                       0.005               (0.01)
aTotal nitrogen oxides expressed as N07.
u
 No data available for NO  emissions from other coke manufacturing sources
 including coal preheaters, coke pushing, quenching, and combustion stacks.
        TABLE 2-18.   NITROGEN OXIDE EMISSION FACTORS FOR GRAY IRON
                   ... FURNACES WITHOUT CONTROL 'EQUIPMENT, (Reference 2-9)
          Furnace Type3                      NO  Emission Factors
                                               A
                                        kg/Mg of gray       (Ib/ton of gray
                                        iron produced        iron produced)
          Electric Arc                   0.02 - 0.3         (0.04 - 0.6)
3No data available for NO  emissions from other types of furnaces including
 cupola, electric induction, and reverberatory.
                                    2-27

-------
           TABLE  2-19.   NITROGEN  OXIDE EMISSION  FACTORS  FOR  STEEL
                        FOUNDRIES WITHOUT CONTROL  EQUIPMENT3,
                        (Reference 2-9)
      Furnace Type                        NO  Emission  Factors
                                          /\
                                    kg/Mg of metal            (Ib/ton of metal
                                    processed                 processed)
      Electric Arc                       0.1                       (0.2)


      Open Hearth                        0.005                     (0.01)
a
 The  streams measured  for  NO  emissions  had  controls  for  particulates,
 however,  these would  not  hatfe  any  effect  on reducing NO  .
h
 No NO  emissions  data were available  for  open  hearth oxygen  lanced  and
 electric  induction  furnaces.
   TABLE 2-20.  NITROGEN OXIDE EMISSION FACTORS FOR GLASS MANUFACTURING
                MELT FURNACES WITHOUT CONTROL EQUIPMENT, (References 2-6)
                                                            a
          Type of Glass                 NOX Emission Factors
                                   kg/Mg of            (Ib/ton of
                                   glass produced       glass produced)
          Container                  1.6 - 4.5,        (3.3 - 9.1,
                                     avg. 3.1           avg. 6.2)

          Flat                       2.8 - 5.2,        (5.6 - 10.5,
                                     avg. 4             avg. 8)

          Pressed and Blown          0.4 - 10.0,       (0.8 - 20.0,
                                     avg. 4.3           avg. 8.5)
a
 NO  emissions from forming and finishing in all three glass categories
 an* negligible.
                                     2-28

-------
2.3.2.2 Glass Industry
In the glass industry, melting furnaces and annealing lehrs are the two fuel combustion
processes of greatest importance. Melters in the glass industry are continuous reverbatory furnaces
fueled by natural gas and oil. Coal is not suitable for these furnaces because of its inherent
impurities. Annealing lehrs control the cooling of the formed glass to prevent stains from
occurring. Some lehrs are direct-fired by atmospheric, premix, or excess-air burners. About
80 percent of the total industry fuel consumption goes for melting, while annealing lehrs consume
about 15 percent. There is a current trend in the glass industry towards electric melters, or at
least electrically assisted conventional melters. But until it becomes clearer which fuels are
going to be available in the future, no definite trends will emerge. Present trends toward fuel oil
in place of natural gas have begun as a result of natural gas shortages and price increases.

'As shown in Table 2-16, nationwide NO emissions from the glass industry were estimated to be
50 Gg (55 x 10 tons) in 1980. Nitrogen oxide emission factors for basic glass manufacturing are
presented in Table 2-20. Table 2-21 presents NO emission factors specifically for glass fiber
manufacturing, a subcategory of the glass manufacturing industry. Emission factors for both tables
were obtained from Reference 2-6.

2.3.2.3 Cement Manufacturing Industry
Cement kilns are the major combustion processes in the cement industry. These kilns are
rotary cylindrical devices up to 230 m (750 feet) in length which contain a feedstock combination of
calcium, silicon, aluminum, iron, and various other trace metals. This mixture of elements in. the
form of various combinations of clay, shale, slate, blast furnace slag, iron ore, silica sand,
limestone, and chalk slowly moves through the kiln as products of fossil fuel combustion move in an
opposite direction. Temperatures of the material during the process may reach 1480°C (2700°F).

Coal, fuel oil, and natural gas are the main fuels used in cement kilns. As of 1977 natural
gas accounted for 45 percent of the fuel consumed, coal for 40 percent, and fuel oil for 15 percent.
The major effluent stream for this process is the exhaust gas which passes through the entire length
of the kiln and may entrain additional particulate or trace metals from the kiln feedstock. Cement
industry figures for the past 20 years show that the industry has grown at an average rate of
1.9 percent annually (Reference 2-16).
2-29

-------
       TABLE 2-21.  NITROGEN OXIDE EMISSION FACTORS FOR GLASS FIBER
                    MANUFACTURING WITHOUT CONTROL EQUIPMENT,
                    (Reference 2-6)
          Source
          NO  Emission Factors
kg/Mg of material        . (Ib/ton of material
  processed                 processed)
Glass Furnace - Wood
     Electric
     Gas-Regenerative
     Gas-Recuperative
     Gas-Unit Melter
Glass Furnace - Textile
     Regenerative
     Recuperative
     Unit Melter
Oven Curing - Wool
     Rotary Spun
     Flame Attenuation
Rotary Spun Cooling - Wool
    0.14
    2.5
    0.85
    0.15
   10
   10
   10
    0.55
    1.0
    0.15
Oven Curing and Curing - Textile  1.3
 (0.27)
     ,
  1.7)
 (0.3)
(20)
(20.)
(20)
 (1.1)
 (2)
 (0.3)


 (2.6)
                                    2-30

-------
Nationwide NO emissions estimates from cement manufacturing are given in Table 2-16.
Table 2-22 gives NO emission factors for both wet and dry process cement manufacturing. All
X
emission factors were obtained from Reference 2-5.
2.3.2.4 Petroleum Refining Industry

A wide variety of process combustion takes place in the petroleum refining industry,
including catalyst regenerating in the catalytic cracker, catalytic reforming, delayed coking, and
hydro-treating and flaring of waste gases. Catalytic cracking is required for a large portion of
gasoline production. Fuel is consumed in this operation in the catalyst regeneration procedure
which removes coke and tars from the catalyst surface. Temperatures during this process are
moderate, ranging from 570 to 650°C (1050 to 1200°F), but fuel requirements are on the order of
829 kJ/ (125,000 Btu/Bbl) feedstock. Future growth of catalytic cracking will depend on the
national energy and environmental policies, and particularly on the demand for low sulfur fuel oil.

Catalytic reforming is a process where paraffinic hydrocarbons are converted into aromatic
compounds. Delayed coking is an energy extensive process which uses severe cracking to convert
residual pitch and tar to gas, naptha, heating oil and other more valuable products. Hydrotreating
is a process designed to remove impurities such as sulfur, nitrogen, and metals to prepare cracking
or reformer feedstock.
Process heating fuels used by the refinery industry are primarily natural gas and refining
gas, along with some residual oils and petroleum coke. Projections are for a 2.9 percent annual
increase in process heating to 1985 (Reference 2-16). The fuel mix expected for the future is
highly dependent on both availability and costs of the preferred fuels, and is therefore very
difficult to project until national energy priorities are established and the question of natural
gas price regulations is settled.
Nationwide NO emissions estimates from petroleum refineries, are presented in Table 2-16
(Reference 2-4). References 2-4 and 2-5 were used to obtain NOX emission factors for petroleum
refinery sources. Table 2-23 presents the petroleum refinery emission factor data.
2.3.2.5 Brick and Ceramic Kilns

Brick and ceramic kilns for curing clay products are another major user of process heating
fuels. Products of these kilns include structural bricks, structural and facing tile, vitrified
2-31

-------
          TABLE 2-22.  NITROGEN OXIDE EMISSION FACTORS FOR CEMENT
                       MANUFACTURING WITHOUT CONTROL EQUIPMENT,
                       (Reference 2-5)
     Process Source                NO  Emission Factors
                              kg/Mg of             (Ib/ton of
                              cement produced      cement produced)
     Dry Process Kilns             1.3                   (2.6)


     Wet Process Kilns             1.3                   (2.6)
a
 These emission factors include emissions from fuel combustion, which should
 not be calculated separately.
                                    2-32

-------
TABLE  2-23.    NITROGEN  OXIDE  EMISSION  FACTORS  FOR PETROLEUM  REFINERIES,
                   (References 2-4,  2-5)
                    Refinery Process8
                                      NOX Emission  Factor
FLUID CATALYTIC CRACKING UNITS

     Uncontrol lad
          kg/10J,liters fresh feed
          (1&71Q  bbl fresh feed)

     ESP and CO,Boilerc
         ' kg/10J..liters fresh feed
          (lb/10J bbl fresh feed)


MOVING-BED CATALYTIC CRACKING UNITS

     kg/103,1iters fresh feed
     (lb/10° bbl fresh feed)


COMPRESSOR ENGINES

     Reciprocating-Engines
          kg/10%nr gas burned
          Mk/inJ ft3 gas tupped)
     Gas
                        Turbines ,
                         kg/10 ,nT  gas burned
                         (lb/103
                SLOWDOWN SYSTEMS

                    Uncontrolled
                         kg/10 ..liters  refinery feed
                         (lb/10J bbl  refinery feed)

                    Vapor Recovery System and Flaring
                         kg/10J,Hters  refinery feed
                                 bbl  refinery feed)
                VACUUM DISTILLATION AND COLUMN
                CONDENSERS

                     Uncontrolled
                         kg/lQ3,liters vacuum feed
                         (lb/10J bbl  vacuum feed)
                     Controlled
                FLARES
                PROCESS HEATERS

                     Oil
                     Gas
                                                      0.107 - 0.416, avg.  » 0.204
                                                      (37.1 - 145, avg. -  71)
                                                      0.107 - 0.416, avg. « 0.204°
                                                      (37.1 - 145, avg. * 71)
                                                               0.014
                                                                (5)
                                                             55.4
                                                             (3.4)
                                               4.7
                                              (0.3)
                                             Negligible
                                            (Negligible)
                                               0.054
                                             (18.9)
                                             Negligible
                                            (Negligible)

                                             Negligible


                                      0.054 kg/103  liters (0.01916 lb/bbl)e
                                      6.57 kg/103  liters (2.30 lb/bbl)e
                                      2.2 kg/nT {0.14 Ib/ff3)6
                 NOX emission factor data fof fluid coking  units were not available.
                bTotal nitrogen oxides  expressed as N02-
                °ESP » electrostatic precipitator, CO « carbon monoxide.
                 Hay be higher due to the combustion of ammonia.
                eTotal nitrogen oxides  and not N02-
                                           2-33

-------
clay pipe, and other related items. Typically, a kiln is operated in conjunction with a drier which
recovers part of the heat contained in the exhaust gases. Kilns are fueled by coal,.oil, or gas
(depending on the availability of fuel and the product being cured) for batch runs of 50 to
100 hours at temperatures around 1090°C (2000°F). Combustion products are ducted from the kiln to a
drfer, where wet clay products undergo an initial drying process. Occasionally, when higher
temperatures are needed for drying, a secondary combustion process is used in the drier itself. NO
emission factors for brick manufacturing were obtained from Reference 2-5 and are presented in
Table 2-24.

2.3.2.6 Noncombustion and Other Minor Industrial Sources
Noncombustion-based NO emissions from the chemical industry dominate this category. Oxides
of nitrogen are chemically released during the production of nitric acid, adipic acid, terephthalic
acid, acrylonitrile, adiponitrile, and explosives. Tables 2-25 to 2-27 present NO emission factors
for nitric acid, adipic acid, and explosives manufacturing, respectively. Uncontrolled NO
emissions from a terephthalic acid reactor are 6.5 kg/Mg (13 Ib/ton) of• acid produced (Reference
2-5). Uncontrolled NOX emissions from acrylonltrile and adiponitrile production are 4.9 kg/Mg
(9.8 Ib/ton) and 70.6 kg/Mg (140 Ib/ton), respectively (Reference 2-4).
Other Industrial processes such as primary copper smelting, coffee roasting, lime production,
nitrate fertilizer production, and ammonia production also generate oxides of nitrogen in lesser
amounts. NO emission factors for these minor industrial sources are presented in Table 2-28
(References 2-5 to 2-10). Nationwide 1980 NO emissions estimates for some of the minor categories
including ammonia, explosives, organic chemicals, and pulp mills are presented in Table 2-16.
2.3.3 Solid Waste Disposal Sources

This category of NO emissions includes such sources as refuse and sewage sludge incinera-
X
tors, auto body incinerators, conical burners, and open burning. The 1980 nationwide HO emissions
from solid waste disposal are presented in Table 2-1. Each of the solid waste disposal NO sources
are briefly described in the following paragraphs. NO emission factors are presented for each
category of incineration.

The most common type of refuse incincerator consists of a refractory-lined chamber with a
grate upon which refuse is burned. Combustion products are formed by heating and burning of refuse
on the grate. Specific operating conditions, refuse composition, and basic incineration design have
2-34

-------
           TABLE 2-24.   NITROGEN OXIDE EMISSION FACTORS FOR BRICK
                        MANUFACTURING WITHOUT CONTROL EQUIPMENT,
                        (Reference 2-5)
     PROCESS SOURCE
     N0x EMISSION FACTOR
                              kg/Mg of brick
                                 produced
                   /lb/ton of brick]
                        produced   /
CURING AND FIRING
     Tunnel  Kilns
          Gas-fired
          Oil-fired
          Coal-fired

     Periodic Kilns
          Gas-fired
          Oil-fired
          Coal-fired
0.08
0.55
0.45
0.21
0.85
0.70
(0.15)
(1.1)
(0.9)
(0.42)
(1.7)
(1.4)
                                     •2-35

-------
              TABLE 2-25.  NITROGEN OXIDE EMISSION FACTORS FOR
                           NITRIC ACID PRODUCTION3, (Reference 2-9)
          SOURCE
        NOV EMISSION FACTOR
          X
                                   kg/Mg acid
                                    produced
                      Mb/ton acid\
                      y  produced /
WEAK ACID PLANT TAIL GAS
     Uncontrolled
     Catalytic Reduction
       Natural gas
       Hydrogen
       Natural gas/hydrogen
        (25%/75%)c
     Extended Absorption
HIGH STRENGTH ACID PLANF
7-43, avg. 22

0.03-0.6, avg. 0.2
0-0.8, avg. 0.4
0.4-0.6, avg. 0.5

0.4-1.4, avg. 0.9
(14-86,  avg.  43)

(0.05-1.2, avg.  0.4)
(0-1.5,  avg.  0.8)
(0.8-1.1, avg.  1.0)

(0.8-2.7, avg.  1.8)

       (10)
  Based on 100% acid.  Production rates are in terms of total  weight of
  product (water and acid).  A plant producing 454 Mg (500 tons)/day
  of 55 wt. % nitric acid is calculated as producing 250 Mg (275 tons)/day
  of 100% acid.
  Based on data from two plants with these process conditions:  production
  rate, 118 Mg (130 tons)/day at 100% rated capacity; absorber exit
  temperature, 32°C ,(90°F); absorber exit pressure, 600 kPa (87 psig);
  acid strength, 57%.
c Based on data from two plants with these process conditions:  production
  rate, 188 Mg (208 tons)/day at 100% rated capacity; abosrber exit
  temperature, 32°C (90°F); absorber exit pressure, 550 kPa (80 psig);
  acid strength, 57%.
d Based on a unit that produces 6615 kg/hr (3000 Ib/hr) at 100% rated
  capacity, of 98% nitric acid.
                                   2-36

-------
   TABLE  2-26.
NITROGEN OXIDE  EMISSION  FACTORS FOR
ADIPIC  ACID  MANUFACTURE,  (Reference 2-5)
PROCESS SOURCE

RAW MATERIAL STORAGE ,
Uncontrolled
CYCLOHEXANE OXIDATION
Uncontrolled
w/boiler
w/thermal incinerator
w/f Taring
w/carbon adsorber
w/scrubber plus boiler
NITRIC ACID REACTION
Uncontrolled0
w/scrubber
w/thermal reduction6
w/flaring or combustion*
ADIPIC ACID REFINING
Uncontrolled
ADIPIC ACID DRYING, LOADING,
AND STORAGE
Uncontrolled
NOX EMISSION FACTORS3
kg/Mg of acid
produced


0
0
0
0
0
0
0

27
8
0.5
8

0.3

0
/lb/ton of acid\
\ produced j


(0)
(0)
(0)
(0)
(0)
(0)
(0)

(53)
(16)
(1)
(16)

(0.6)

(0)
  NO*  is  in the form of NO and NCfc.  Although large quantities of N20 are
  also produced, N?0 is not considered a criteria pollutant and is not,
  therefore, included in these factors.

  Uncontrolled emission factors are after scrubber processing since
  hydrocarbon recovery using scrubbers is an integral part of adipic acid
  manufacturing.

c Uncontrolled emission factors are after NOX absorber since nitric acid
  recovery is an integral part of adipic acid manufacturing.

  Based on estimated 70% control.

e Based on estimated 97.5% control.
                                    2-37

-------
   TABLE  2-27.
NITROGEN OXIDE  EMISSION FACTORS FOR
EXPLOSIVE MANUFACTURING,  (Reference 2-5)
     PROCESS SOURCE
                        NO  EMISSION  FACTORS
                                   kg/Mg produced
                                     (Ib/ton produced)
TNT - BATCH PROCESS-
     Nitration Reactors
          Fume recovery
          Add recovery
     Nitric Acid  Concentrators
     Sulfuric Acid  Concentrators
          ESP exit
          ESP w/scrubbera
     Red Water Incinerator
          Uncontrolled
          Wet scrubber
TNT - CONTINUOUS PROCESS
     Nitration Reactors
          Fume recovery
          Acid recovery
     Red Water Incinerator


NITROCELLULOSE
     Nitration Reactorsd  .
     Nitric Acid Concentrator
     Boiling Tubs
               3-19, avg. 12.5
               0.5-68, avg.  27.5
               8-36, avg. 18.5

               1-40, avg. 20
               1-40,. avg. 20

               0.75-50, avg. 13
               .  2.5
               3.35-5.0, avg.  4
               0.5-2.25, avg.  1.5
               3-4.2, avg. 3.5
               1.85-17, avg. 7
               5-9, avg. 7
                       1
(6-38, .avg. 25)
(1-136,  avg. 55)
(16-72,  avg. 37)

(2-80, avg. 40)
(2-80, avg. 40)

(1.5-101,  avg. 26)
(5.0)
(6.7-10,  avg. 8)
(1-4.5,  avg. 3)
(6.1-8.4, avg. 7)
(3.7-34,  avg.  14)
(10-18, avg.  14)
       (2)
a No data available  for NOX emissions after the scrubber.  It is assumed
  that NO  emissions are unaffected by the scrubber.
  Use low end of range for modern, efficient units  and high end for older,
  less efficient units.
  Apparent reductions in NOX after control may not  be significant because
  these values are based on only one test result.
  For product with low nitrogen content (12 percent), use high end of range.
  For products with  higher nitrogen content, use lower end of range.
                                      2-38

-------
                                   TABLE 2-28.   NITROGEN  OXIDE  EMISSION  FACTORS  FOR
                                                MISCELLANEOUS  INDUSTRIAL-PROCESSES,
                                                (References  2-5 to  2-10)
            INDUSTRY
     SOURCE
          NOV EMISSION FACTOR0
            A *
I
to
u>
       AMMONIA PRODUCTION
       CARBON BLACK
        PRODUCTION
       COFFEE ROASTING
       GRANULAR NITRATE
        FERTILIZER MFG.
Primary Reformer
  Natural gas
  Fuel oil
Oil Furnace Process
  Main process vent
  Flare
  CO boiler &
   i nci nerator
  Dryer vent
    bag filter

    scrubber
  Solid waste
   incinerator
Thermal Process
Roaster
  Di rect-fi red
  indirect-fired
Grandulator
Dryers & Coolers
2.9 kg/Mg (5.8 Ib/ton) of ammonia produced
2.7 kg/Mg (5.4 Ib/ton) of ammonia produced

0.28 kg/Mg (0.56 Ib/ton) of carbon black produced
Not Available

4.65 kg/Mg (9.3 Ib/ton) of carbon black produced
                                                         0.12-0.61  kg/Mg,  avg.  0.36
                                                           (0.24-1.22  Ib/ton,  avg. 0.73)
                                                         1.1  kg/Mg  (2.2  Ib/ton)  of carbon  black  produced

                                                         0.04 kg/Mg (0.08  Ib/ton) of  carbon  black  produced
                                                         Unknown0
0.05 kg/Mg (0.10 Ib/ton) of coffee produced
0.05 kg/Mg (0.10 Ib/ton) of coffee produced
0.45 kg/Mg (0.9 Ib/ton) of fertilizer produced
1.5 kg/Mg (3.0 Ib/ton) of fertilizer produced

-------
TABLE 2-28.  NITROGEN OXIDE EMISSION FACTORS FOR MISCELLANEOUS INDUSTRIAL PROCESSES (CONTINUED)
ORCHARD HEATERS
ASPHALTIC CONCRETE
 PRODUCTION
PRIMARY COPPER
 SMELTING6
LIME PRODUCTION9
 GAS  SWEETENING PLANTS1
 PULP MILLS
Type of Heater
  Pipeline
  Lazy flame
  Return stack
  Cone
  •Solid fuel
Rotary Drum

Reverb Furnace
 Followed by Converters
  Reverb furnace

  Converters
Crushers, Screens,
 Conveyors, Storage
 Piles
                         Rotary Kilns
                         Vertical Kilns
                                         .h
Calcimatic Kilns
Fluidized-Bed Kilns
Product 'Coolers
Hydrators
Amine
Kraft Pulp Process
Negligible0
Negligible
Negligible
Negligible
Negligible
18 g/Mg (0.036 Ib/ton) of concrete produced6'
                                                  0.045 kg/Mg (0.09 Ib/ton) of ore
                                                   concentrate processed
                                                  0.025 kg/Mg (0.05 Ib/ton) of ore
                                                   concentrate processed
Negligible
1.5 kg/Mg (3 Ib/ton) of lime produced
Data Not Available
0.1 kg/Mg (0.2 Ib/ton) of lime produced
Data Not Available
Negligible
Negligible
Negligible
0.90 kg/Mg (1.79 Ib/ton) of pulp produced

-------
FOOTNOTES FOR TABLE 2-28.
a All emission factors are for uncontrolled emissions unless otherwise specified.
  Average values are based on the results  of six sampling runs conducted*at a representative
  plant with the industry mean production  rate of 5.1 x 10  Mg (5.6 x 10  tons)/yr.
c Emissions data are not available, but all  emissions are believed to be negligible.
  Little nitrogen oxide is formed because  of the relatively low combustion temperatures.
e Total nitrogen oxides expressed as N02 .
  Based on limited test data from a single asphaltic concrete plant.
^ All emission factors for kilns and coolers are per unit of lime produced.  Divide  by two to
  obtain factors per unit of limestone feed to the kiln.   Factors for hydrators are  per unit
  of hydrated lime produced.  Mul.tiply by  1.25 to obtain factors per unit of lime  feed to
  the hydrator.
  Calcimatic kilns generally employ stone  preheaters.  All  factors represent emissions after
  the kiln exhaust passes through a preheater.
1 Emission factors are presented only for  smokeless flares and tail gas incinerators  on the
  amine gas sweetening process.   These factors represent emissions after smokeless flares
  (with fuel gas and steam injection) or tail  gas incinerators.

-------
a pronounced effect on emissions. Nitrogen oxide emissions increase'with an increase in the
temperature of the combustion zone, an increase in the residence time iri the combustion zone before
quenching, and an increase in the excess air rates to the point where dilution cooling overcomes the
effect of increased oxygen concentration (References 2-5 to 2-6). Refuse incinerators have been
labeled as municipal, industrial/commercial, trench, domestic, flue-fed, pathological, and
controlled-air depending on the specific use sector or use function. NO emission factors for
refuse incinerators are given in Table 2-29 (References 2-5 to 2-6).
Incineration is being used to dispose of sewage sludge because it destroys the organic matter
present in sludge, leaving only an odorless, sterile ash, and also reduces the solid mass by about
90 percent. The most prevalent types of sewage sludge incinerators are multiple hearth and
fluldized bed units. In multiple hearth units the sludge enters the top of the furnace where it is
first dried by contact with the hot, rising-, combustion gases, and then burned as it moves slowly
down through the lower hearths. At the bottom hearth any residual ash is then removed. In
fluidized bed reactors, the combustion takes place in a hot,, suspended bed of sand with much of the
ash residue being swept out with the flue gas. Temperatures in a multiple hearth furnace are 320°C
(600°F) in the lower, ash cooling hearth; 760 to IIOO'C (1400 to 2000°F) in the central combustion
*
hearths, and 540 to 650°C (1000 to 1200°F) in the upper, drying hearths. Temperatures in a
fluidized bed reactor are fairly uniform, from 680 to 820°C (1250 to 1500°F). In both types of
furnace an auxiliary fuel may be required either during startup or when the moisture content of the
sludge is too high to support combustion.
NO emission factors for sewage sludge incinerators were obtained from Reference 2-5 and are
X
presented in Table 2-30.

Auto incinerators consist of a single primary combustion chamber in which one or several
partially stripped cars are burned. Approximately 30 to 40 minutes is required to burn two bodies
simultaneously. As many as 50 cars per day can be burned in this batch-type operation, depending on
the capacity of the incinerator. Continuous operations in which cars are placed on a conveyor belt
and passed through a tunnel-type incinerator have capacities of more than 50 cars per 8-hour day.
Both the degree of combustion as determined by the incinerator design and the amount of combustible
material left on the car greatly affect emissions. Temperatures on the order of 650°C (1200°F) are
reached during auto body incineration. Some auto incinerators are designed for two stage combus-
tion, using afterburner control devices; Afterburners result in a reduction of both NO emissions
and the emissions of the other criteria pollutants.
. 2-42"

-------
           TABLE 2-29.  NITROGEN OXIDE EMISSION FACTORS FOR REFUSE
                        INCINERATORS WITHOUT CONTROL EQUIPMENT,
                        (References 2-5, 2-6)
     INCINERATOR TYPE
  NO  EMISSION FACTORS0
                                   kg/Mg of refuse
                                       burned
               Ib/ton of refuse\
                    burned
MUNICIPAL
     Multiple Chamber
INDUSTRIAL/COMMERCIAL
     Multiple Chamber
     Single Chamber
     Trench
          Wood
          Rubber tires
          Municipal refuse
     Control!ed-air
FLUE-FED SINGLE CHAMBER
FLUE-FED (MODIFIED)5
DOMESTIC SINGLE CHAMBER
     w/o Primary Burner
     w/Primary Burner
PATHOLOGICAL
.1.5

1.5
1
(3)

(3)
(2)
2                     (4)
   Data not.avail able
   Data not available
5                    (10)
1.5                   (3)
5                    (10.)
0.5
1
1.5
(1)
(2)-
(3)
  Total nitrogen oxides expressed as N02«
  W.ith afterburners and draft controls.
                                    2-43

-------
                 TABLE  2-30.   NITROGEN OXIDE EMISSION FACTORS
                              FOR SEWAGE SLUDGE INCINERATORS,
                              (Reference 2-5)
CONTROL STATUS



Uncontrolled
After Scrubber Control
NO EMISSION
X
kg/Mg
FACTORS9 fb

' (Ib/ton)

3
Z.b
(6)
(5)
a Unit weights in terms of dried sludge
  Total nitrogen oxides expressed as
                  TABLE  2-31.   NITROGEN OXIDE  EMISSION  FACTOR
                               FOR AUTO BODY  INCINERATORS,
                               (Reference 2-5)
CONTROL STATUS

Uncontrolled
With Afterburner
N0x
kg/car
EMISSION FACTORSa'b
(Ib/car)

0.05
0.01
(0.1)
(0.02)
  Based on 113 kg (250 Ib) of combustible material on stripped car body.
  Total nitrogen oxides expressed as N02.
                                     2-44

-------
NO emission factors for auto body Incinerators are presented In Table 2-31 (Reference 2-5).

Conical burners are generally a truncated metal cone with a screened top vent. The charge 1s
placed on a raised grate by either conveyor or bulldozer; however, the use of a conveyor results 1n
more efficient burning. No supplemental fuel 1s used, but combustion air 1s often supplemented by
underflre air blown Into the chamber below the grate and by overflre air Introduced through
peripheral openings 1n the shell. The quantities and types of pollutants released from conical
burners are dependent on the composition and moisture content of the charged material, control of
combustion air, type of charging system used, and the condition In which the Incinerator 1s
maintained. The most critical of these factors seems to be the level of maintenance on t!,e
Incinerators. It 1s not uncommon for conical burners to have missing doors and numerous holes 1n
the shell, resulting 1n excessive combustion air, low temperatures, and therefore, Mgh emission
rates of combustible pollutants. NO emission factors for conical burners handling municipal and
wood refuse are presented 1n Table 2-32 (Reference 2-5).

Open burning can be done In open drums or baskets, 1n fields and yards, and 1n large open
dumps or pits. Materials commonly disposed of In this manner are municipal waste, auto body
components, landscape refuse, agricultural field refuse, wood refuse, bulky Industrial refuse, and
leaves. Ground-level open burning 1s affected by many variables Including wind, ambient tempera-
ture, composition and moisture content of the refuse burned, and compactness of the pile. In
general, the relatively low temperatures associated with open burning suppress the emission of
nitrogen oxides. Estimates of nationwide NO emissions from open burn1 ig are given in Table 2-1.
NO emission factors for the open burning of nonagr1cultural materials are presented 1n Table 2-33
(Reference 2-6).
2.3.4 Other Miscellaneous NO Sources
Forest fires, structural fires, and explosives detonation are some of the NO sources
Included 1n this category. Nationwide NO emissions estimates for miscellaneous sources such as
th?s*j are given in Table 2-1. Available NOX emission factors for forest fires and explosives
detonation are presented in Tables 2-34 and 2-35 (References 2-5 and 2-8).
2-45

-------
     TABLE 2-32.  NITROGEN OXIDE EMISSION FACTORS FOR WASTE INCINERATION
                  IN CONICAL BURNERS WITHOUT CONTROL EQUIPMENT,
                  (Reference 2-5)
TYPE OF WASTE

Municipal Refuse
Wood Refuse3
NOV EMISSION
A
kg/Mg of refuse
burned
FACTORS
Mb/ton of refuse]
\ burned /

2.5
0.5
(5)
t1)
  Moisture content as fired is approximately 50 percent for wood waste.
            TABLE 2-33.  NITROGEN OXIDE EMISSION FACTORS FOR OPEN
                         BURNING OF NONAGRICULTURAL MATERIALS,
                         (Reference 2-6)
     TYPE OF WASTE
NOV EMISSION FACTORS
  J\
                              kg/Mg of refuse
                                  burned
              Mb/ton of refuse\
              \     burned     /
Municipal Refuse
Automobile Components'
                      (6)
                      (4)
  Upholstery, belts, hoses, and tires burned in common.
                                     2-46

-------
            TABLE 2-34.  NITROGEN OXIDE EMISSION FACTORS
                         FOR FOREST WILDFIRES, (Reference 2-5)
GEOGRAPHIC AREAb

Rocky Mountain Group
Northern - Region 1
Rocky Mountain - Region 2
Southwestern - Region 3
Intermountain - Region 4
Pacific Group
California - Region 5
Pacific Northwest - Region 6
Alaska - Region 10
Southern Group
Southern - .Region 8
North Central Group
Eastern - Region 9
Eastern Group (with Region 9)
TOTAL United States
NOV EMISSION
X
kg/hectare of
forest burned
FACTORS
/ Ib/acre of \
^forest burned 1

166
269
135
45
36
85
81
269 ,
72
40
40
49
49
49
76
(148)
(239)
(120)
(40)
(32)
(76)
(72)
(239)
(64)
(35.6)
. (35.6)
(43.6)
(43.6)
(43.6)
(67.6)
Areas consumed by fire and NO* emissions are for 1971.
Geographic areas are specifically defined in Reference 2-5.
                                  2-47

-------
                TABLE 2-35.  NITROGEN OXIDE EMISSION FACTORS
                             FOR THE DETONATION OF EXPLOSIVES,
                             (Reference 2-8)
EXPLOSIVE3
    COMPOSITION
      NOV EMISSION FACTOR
        J\            	
                                               kg/Mg
                                               (Ib/ton)
Dynamite,
  Gelatin
ANFO
20-100% nitroglycerine
ammonium nitrate with
  5.8-8% fuel oil
4-59, avg. 26   (8-119, avg. 53)
      8
(17)
  Emission factors for black powder, smokeless powder, dynamite-strai'ght,
  dynamite-ammonia, TNT, RDX, and PETN were not available.
                                   2-48

-------
                                    2.4  REFERENCES FOR SECTION 2
2-1  Chamot, E.M., D.S. Pratt, and H.W. Redfield.  "Journal  of the American Chemical  Society,"  33,
     366, 1911.
2-2  Code of Federal Regulations, Title 40, Part 60, Appendix A, Method 7.  See Also:  Hamil,  H.  and
     R. Thomas.  "Collaborative Study of Method for the Determination of Nitrogen Oxide Emissions
   '  from Stationary Sources," SwRI-EPA Contract 68-02-0626.  May 1974.
2-3  Federal Register, Volume 41, No. 232.  December 1, 1976.
2-4  Unpublished Data of the Monitoring and Data Analysis Division of the Office of Air Quality
     Planning and Standards, U.S. Environmental Protection Agency.  Research Triangle Park,
     North Carolina.  July 1982.\
2-5  "Compilation of Air Pollution Emission Factors (Third Edition)," Publication No. AP-42.  U.S.
     Environmental Protection Agency, Research Triangle Park, North Carolina.  August 1977.
2-6  Supplement No. 8 of Reference 2-5, May 1978.
2-7  Supplement No. 9 of Reference 2-5, July 1979.
2-8  Supplement No. 10 of Reference 2-5, February 1980.
2-9  Supplement No. 11 of Reference 2-5, October 1980.
2-10 Supplement No. 12 of Reference 2-5, April 1981.
2-11 Draft Supplement No. 13 of Reference 2-5, August 1982.
2-12 Personal communication with H.J. Melosh III, Foster Wheeler Corporation.
2-13 Surprenant, N.F. et. a!.  "Preliminary Emissions Assessment of Conventional Stationary  •
     Combustion SystemsT"" GCA Corporation, EPA Report No. 600/2-76-046b. March 1976.
2-14 Devitte, T., et. al., "The Population and Characteristics of Industrial/Commercial Boilers,"
     EPA-600/7-79-T78a, August 1979.
2-15 Cato, G.A., H.J. Buening, C.C.- DeVivo, B.C. Morton, and J.M. Robinson. "Field Testing:
     Application of Combustion Modification to Control Pollutant Emissions  from Industrial  Boilers  -
     Phase 1," KVB Engineering Inc., EPA-650/2-74-078a, Research Triangle Park, North Carolina.
     October 1974.
2-16 Foley, 6.  "Industrial Growth Forecasts," Stanford Research Institute, Contract No. 68-02-1320.
     September 1974.
                                                 2-49

-------

-------
SECTION 3

CONTROL TECHNIQUES

This section presents a survey of the general principles and developmental status of
potential techniques for NO ' control for stationary sources. It is intended to provide a broad
perspective on the various suggested concepts for NO control by combustion process modification and
flue gas treatment for combustion sources and by tail gas cleanup for noncombustion sources. A more
detailed review of the status of development, effectiveness, and cost of control implementation on
specific equipment types is given in Sections 4, 5, and 6.

3.1 COMBUSTION MODIFICATIONS

Modifying the combustion process is the most widely used technique for reducing combustion
generated oxides of nitrogen. This section describes the four most popular methods: modification
of the operating conditions, equipment design modification, fuel modification, and use of alternate
combustion processes. The section begins by describing general concepts on NO formation and
control during combustion. Much of the material in Section 3.1 was taken directly from
Reference 3-1 and the reader is referred back to this document for further discussion of combustion
modifications, especially as applied to utility boilers.
3.1.1 General Concepts on NO.. Formation and Control
"""' ' -• "-™1™""-111"—"••"•' ------ - — X ••— --•- —: --.-.-.-.-
Oxides of nitrogen formed in combustion' processes are due either to the thermal fixation of
atmospheric nitrogen in the combustion air, which produces "thermal NO ," or to the conversion of
chemically bound nitrogen in the fuel, which produces "fuel NOV." For natural gas and light
A . '
distillate oil firing, nearly all NO emissions result from thermal fixation. With residual oil,
X
crude oil, and coal, the contribution from fuel bound nitrogen can be significant and, in certain
cases, predominant.
' \
A third potential mechanism of NOX formation arises in processes such as glass manufacturing,
where the raw materials in contact with the combustion products contain nitrogen compounds. Little
is known about the extent of conversion to NO of these nitrogen compounds, or of the effects of
combustion modifications on this mechanism.
3-1

-------
3.1.1.1  Thermal NOX
       During combustion, nitrogen oxides are formed by the high temperature,  thermal  fixation  of
N«.  Nitric oxide (NO) is the major product, even though N02 is-thermodynamically favored at lower
temperatures.  The residence time in most stationary combustion processes is too short for signifi-
cant NO to be oxidized to NCL.

     The detailed chemical mechanism for thermal NO  formation is not fully understood.   However, it
is widely accepted that thermal fixation in the postcomfaustion zone occurs according to the extended
form of the Zeldovich chain mechanism (Reference 3-2):
                                        N2 + 0  * NO  + N                          '       (3-1)
                                        N  + 02 * NO  + 0 '                                (3-2)
                                        N  + OH * NO  + H                                 (3-3)
assuming that the combustion reactions have reached equilibrium.   Reaction (3-1)  has  a  large
activation energy (317 kJ/mol) and is generally believed to be rate determining.   Oxygen  atom
concentrations are assumed to have reached equilibrium according  to:

                                        02+M*0+0+M                            (3-4)

where H denotes any third substance (usually N2).

       In the flame zone itself, the Zeldovich mechanism with the equilibrium oxygen  assumption  is
not adequate to account for experimentally observed NO formation  rates.   Several  investigators have
observed the production of significant amounts of "prompt" NO, which  is  formed very rapidly in the
flame front (References 3-3 through 3-11), but there is not general agreement on  how  it is produced.
Prompt NO is believed to stem from the existence of "superequilibrium" radical concentrations
(References 3-11, 3-12, and 3-13) within the flame zone which result  from hydrocarbon chemistry
and/or nitrogen specie reactions, such as suggested by Fenimore (Reference 3-14),  To date, prompt
NO has only been explicitly measured in carefully controlled laminar  flames, but  the  mechanism
almost certainly exists in typical combustion flames as well.  Of course, in an actual  combustor,
both the hydrocarbon and NO  kinetics are directly coupled to turbulent  mixing in the flame zone.

       Recent experiments at atmospheric pressure indicate that under certain conditions  the  amount
of NO formed in heated N2, 02, and Ar mixtures can be expressed as (Reference 3-15):
                                               3-2

-------
                                   [NO] = kj exp(-k2/T)[N2][02J4t                         (3-5)
     where     [  ]    = mole fraction
               k., k2  = constants
               T       = temperature
               t       = time

Although this expression certainly will not adequately describe NO formation in a turbulent flame,
it does point out several features of thermal NO  formation.  It reflects the strong dependence of
NO formation on temperature.  It also shows that NO formation is directly proportional  to NX concen-
tration and to residence time, and proportional to the square root of oxygen concentration.

       Based on the above relations, thermal NO  can theoretically be reduced using four tactics:
     j                    "                 '     A          '

               1)  Reduce local nitrogen concentrations at peak temperature;
               2)  Reduce local oxygen concentrations at peak temperature;
               3)  Reduce the residence time at peak temperature; and
               4)  Reduce peak temperature.

Since reducing N2 levels is quite difficult, efforts in the field have focused on reducing oxygen
levels, peak temperatures,  and time of exposure in the NO  producing regions of the combustion
chamber.
       On a macroscopic scale, techniques such as lowered excess air and off stoichiometric (or
staged) combustion have been used to lower local 02 concentrations in boilers.  Also, staged combus-
tion in the form of stratified charge cylinder design has been used successfully in 1C engines.
Since gas turbines typically operate at excess air levels far greater than stoichiometric, lowering
excess air levels in this -equipment class does not control thermal NO .
                                                                     X
       Flue gas recirculation and reduced air preheat have been used in boilers to control thermal
NO  by lowering peak flame temperatures.  Flue gas recirculation also reduces combustion gas
residence time, but its primary effect as a thermal NO  control is through temperature reduction.
                                                      X
Analogously, exhaust gas recirculation (EGR), reduced manifold air temperature (1C engines) and
reduced air preheat (regenerative gas turbines) have been applied to 1C engines and gas turbines.
Other techniques designed to lower peak temperatures in prime movers include water injection and
altered air/fuel ratios.  Techniques for prime movers which specifically reduce exposure time at
                                           3-3

-------
high temperatures include ignition retard for 1C engines and early quench with secondary air for gas
turbines.

It is important to recognize that the above-mentioned techniques for thermal NOX reduction
alter combustion conditions on a rnacroscopic scale. Although these macroscopic techniques have all
been relatively successful in reducing thermal NO , local microscopic combustion conditions
ultimately determine the amount of thermal NO formed. These conditions are in turn intimately
related to such variables as local combustion intensity, heat removal rates, and internal mixing
effects. Modifying these secondary combustion variables at microscopic levels requires fundamental
changes in combustion equipment design..

For example, recent studies on the formation of thermal NOV 1n gaseous flames have confirmed
X
that internal mixing can have large effects on the total amount of NO formed (References 3-16,
3-17). Burner swirl, combustion air velocity, fuel injection angle and velocity, quarl angle, and
*
confinement ratio all affect the mixing between fuel, combustion air, and recirculated products.
Mixing, in turn, alters the local temperatures and specie concentrations which control the rate of
NO formation.

Unfortunately, generalizing these effects is difficult, because the interactions are complex.
Increasing swirl, for example, may both increase entrainment of cooled combustion products (hence
lowering peak temperatures) and increase fuel/air mixing (raising local combustion intensity). The
net effect of increasing swirl'can be to either raise or lower NOX emissions, depending on other
system parameters.

In summary, a hierarchy of effects depicted in Table 3-1 produces local combustion conditions
which promote thermal NOX formation. Although combustion modification technology seeks to affect
the fundamental parameters of combustion, modifications must be made by changing the primary equip-
ment and fuel parameters. Control of thermal NOX, which began by altering inlet conditions and
external mass addition, has moved to more fundamental changes in combustion equipment design.
3.1.1.2 Fuel NOX

The role of fuel bound nitrogen as a source of NO emissions from combustion sources has been
recognized since 1968 (Reference 3-18). Although the relative contribution of fuel and thermal NO
to total NOX emissions from sources firing nitrogen containing fuels has not been definitively
established, recent estimates indicate that fuel NOV is significant and may even predominate. In
A
3-4

-------
one laboratory study (Reference 3-19), residual oil and pulverized coal were burned in an
argon/oxygen mixture to eliminate thermal N0v effects. Results show that fuel NOV can account for
A A
over 50 percent of total NO production from residual oil firing and approximately 80 percent of
X
coal-fired utility boiler,
confirm this prediction (Reference 3-20). Flue gas recirculation, which controls primarily thermal
total NOX from coal firing. Tests on a full scale system, a 560
NO , was a relatively ineffective NO control measure for the coal-fired boiler tested.
X . X
TABLE 3-1. FACTORS CONTROLLING THE FORMATION OF THERMAL NOX (Reference 3-1)
Primary Equipment
and Fuel Parameters
Secondary
Combustion Parameters
Fundamental
Parameters
Inlet temperature,
velocity
Firebox design
Fuel composition
Injection pattern
of fuel and air
Size of droplets
or particles
Burner swirl
External mass
addition
Combustion intensity
Heat removal rate
Mixing of combustion
products into flame
Local fuel/air ratio
Turbulent distortion
of flame zone
Oxygen level
Peak temperature
Exposure time at
peak temperature
Thermal
NO.,
Fuel bound nitrogen occurs in coal and petroleum fuels. However, the nitrogen containing
compounds in petroleum tend to concentrate in the heavy resin and asphalt fractions upon
distillation (Reference 3-21). Therefore, fuel NO is of importance primarily in residual oil and
coal firing. The nitrogen compounds found in petroleum include pyrroles, indoles, isoquinolines,
acridines, and porphyrins. Although the structure of coal has not been defined with certainty, it
is believed that coal-bound nitrogen also occurs in aromatic ring structures such as pyridine,
picoline, quinoline, and nicotine (Reference 3-21).

The nitrogen content of most residual oils varies from 0.1 to 0.5 percent. Nitrogen content
of most U.S. coals lies in the 0.5 to 2 percent range (Reference 3-22); anthracite coals contain the
least and bituminous coals the most nitrogen. Figure 3-1 illustrates the nitrogen content of
various U.S. coals, expressed as ng N02 produced per joule for 100 percent conversion of the fuel •
nitrogen (Reference 3-23). The figure clearly shows that if all coal bound nitrogen .were converted
3-5

-------
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-------
to NO , emissions for all coals would exceed even the 1971 Standards of Performance for Large Steam
X
Generators (NSPS). Fortunately, only a fraction of the fuel nitrogen is converted to NO for both
oil and coal firing, as shown in Figure 3-2 (Reference 3-24). Furthermore, the figure indicates
that fuel nitrogen conversion decreases as nitrogen content increases. Thus, although fuel NO
emissions undoubtedly increase with increasing fuel nitrogen content, the emissions increase is not •
proportional. In fact, recent data indicate only a small increase in NO emissions as fuel nitrogen
increases (Reference 3-25). From observations such as these, the effectiveness of partial fuel
denitrification as a NO control method seems doubtful.

Although the precise mechanism by which fuel nitrogen is converted to NO is not understood,
certain aspects are clear, particularly for coal combustion. In a large pulverized coal-fired
utility boiler, the coal particles are conveyed by an airstream into the hot combustion chamber,
n •
where they are heated at a rate in excess of 10 °K/s. Almost immediately volatile species,
containing some of the coal bound nitrogen, vaporize and burn homogeneously, rapidly (<300 ms).

Figure 3-3 summarizes what may happen to fuel nitrogen during this process (Reference 3-26).
In general, nitrogen evolution parallels evolution of the total volatiles, except during the initial
10 to 15 percent volatilization in which little nitrogen is released (Reference 3-27). Both total
mass volatilized and total nitrogen volatilized increase with higher pyrolysis temperature; the
nitrogen volatilization increases more rapidly than that of the total mass. Total mass volatilized
appears to be a stronger function of coal composition than total nitrogen volatilized
(Reference 3-28). This supports the relatively small dependence of fuel NO on coal composition
observed in small scale testing (References 3-19 and 3-29).

Although there is not absolute agreement on how the volatiles separate into species, it
appears that about half the total volatiles and 85 percent of the nitrogeneous species evolved react
to form other reduced species before being oxidized. Prior to oxidation, the devolatilized nitrogen
may be converted to a small number of common, reduced intermediates, such as HCN and NH,, in the
fuel-rich regions of the flames. The existence of a set of common reduced intermediates would
explain the observations that the form of the original fuel nitrogen compound does not influence its
conversion to NO (e.g., References 3-21, 3-30). More recent experiments suggest that HCN is the
predominant reduced intermediate (Reference 3-31). The reduced intermediates are then either
oxidized to NO, or converted to Np in the postcombustion zone. Although the mechanism for these
conversions is not presently known, one proposed mechanism postulates a role for NCO
(Reference 3-32).