Chemical Transformations of Nitrogen Oxides While Sampling ...

Chemical Transformations of Nitrogen OxidesWhile Sampling Combustion Products

G. S. Samuelsen and John N. Harman, IIIUniversity of California, Irvine, California

The present study reviews the sampling environments and chemical transformations of nitro-

gen oxides that may occur within probes and sample lines while sampling combustion products.

Experimental data are presented for NOX transformations in silica and 316 stainless steel tubing

when sampling simulated combustion products in the presence of oxygen, carbon monoxide,

and hydrogen. A temperature range of 25° to 400 °C is explored. In the absence of CO and H2,

316 stainless steel is observed to promote the reduction of nitrogen dioxide to nitric oxide at

temperatures in excess of 300°C, and silica is found to be passive to chemical transformation.

In the presence of CO, reduction of NO2 to NO is observed in 316 stainless steel at temperatures

in excess of 100°C, and reduction of NO2 to NO In silica is observed at 400°C. In the presence

of H2, NO2 is reduced to NO in 316 stainless steel at 200°C and NOX is removed at temperatures

exceeding 200°C. In silica, the presence of H 2 promotes the reduction of NO2 to NO at 300°C

and the removal of NO* above 300°C.

Measurement of the exhaust gas com-position from anthropogenic sourcessuch as automobile engines, diesel en-gines, utility and industrial boilers,furnaces, and gas turbine engines is re-quired to evaluate system efficiency andpollutant emission levels. Measurementgenerally proceeds by extracting andtransporting a sample to instrumenta-

Dr. Samuelsen is Associate Profes-sor of Mechanical and Environmen-tal Engineering, School of Engineer-ing, University of California, Irvine,CA 92717. Mr. Harman recently re-ceived the Master of Science degreein Engineering at UCI. He currentlyserves as a Senior Chemist at Beck-man Instruments, Inc., Fullerton, CA92634. The work was conducted atthe UCI Combustion Laboratory,School of Engineering, University ofCalifornia, Irvine, CA 92717.

tion for quantitative analysis. To obtainreliable data, it is necessary that theanalytical instrumentation receive asample that is chemically identical tothe composition existing at the point ofextraction.

Potential sample transformationsmay be minimized by careful selectionof materials for the probe and sampleline. However, careful selection requiresdata relevant to the application, anddata are presently not plentiful for twoproducts of combustion especially sus-ceptible to chemical transformation,nitric oxide (NO) and nitrogen dioxide(NO2). This paper summarizes theavailable information and presents re-sults from an experiment designed toassess the conditions for which chemicaltransformation of nitrogen oxides oc-curs.

Types of Transformation

Chemical transformation of nitrogenoxides in probes and sample lines maybe of three general types:

NO Oxidation: NO NO2

NO* conserved

NO2 Reduction: NO2

NOr conserved

NO* Removal: NO, NO2 — N2

NOX not conserved

An additional transformation path,formation, involves the oxidation of ni-trogen containing species such as am-monia (NH3). Because formation ofNO* in probes and sample lines is gen-erally limited to specialized conditions(e.g. sample extraction from flue gasesinto which ammonia has been injectedfor NOX control, or from flames intowhich nitrogen containing compoundshave been injected to study fuel boundNO* formation), formation reactions arenot separately identified.

The potential significance of thetransformation of nitrogen oxides restson the use of the emissions data. Forexample, emission standards for nitro-gen oxides are currently proposed or

648 Journal of the Air Pollution Control Association

Table I. Sampling conditions for nitrogen oxides.

Source

Internal com-bustion engine

Diesel engine

Residential oilburners

Boilers

Gas turbine

Flame research

TypicalNOX ppm

500-4000500-1000'

1000-7000

700-2500

20-100

200-1000

25-800

1000-8000

25-200

10-8000

• Sampling point

Combustion zoneEngine exhaust

Combustion zone

Engine exhaust

Flue gas

Combustion zone

Flue gas

Combustion zone

Engine exhaust

Within flame

Typical sampling

Temperature °C

1300-2400200-500

700-2500

200-500

100-300

100-1600

100-300

1300-2700

400-1500

700-2500

; environment

Atmosphere

ReducingReducing

Reducing andOxidizing

Oxidizing

Oxidizing


Oxidizing


Oxidizing


References

Examples ofNOX probing

42,433,5

44

4

45

7,8

1,46,47

11

25,48,49,50, 51

52, 53, 54,55, 56,57

Prior studiesrelevant to

possible NOXtransformations

14

14

14

15, 16, 17

14

11, 14

15, 16, 17

promulgated in terms of nitrogen oxides,NO*.1-5 As a result, the enforcement ofemission standards is not compromisedby the occurrence of NO oxidation orNO2 reduction reactions in the probe orsample line so long as total oxides of ni-trogen are conserved. However, emis-sions data biased by NOX removal re-actions are unacceptable as the basis forany emissions standard, control strate-gy, or enforcement action.

In addition to conserving NOX, theinfluence of NO oxidation and NO2 re-duction reactions in probes and samplelines warrants increased attention aswell. For example:1. Assessment of local air quality im-pactThe NO/NO2 emission ratio is impor-tant in assessing local air quality impactfrom major sources. Ambiguity regard-ing the NO/NO2 emission ratio fromcombustion sources presently precludesconsideration of the impacts of NO andNO2 emissions on areas in proximity tothe source.2. Assessment of plume visibility im-pactThe NO/NO2 emission ratio is impor-tant in the prediction of plume visibilityfrom power plants.6 The ambiguity re-garding the NO/NO2 emission ratiofrom power plants presently precludesa full assessment of air quality andplume visibility impact, and compro-mises attempts to validate visibilityimpact models.3. Regional oxidant modelingThe prediction of local formation andremoval rates for oxidant requires spa-tial and temporal emission inventoriesfor both NO and NO2. Ambiguity re-garding the NO/NO2 emission ratiofrom mobile and stationary sources

contributes to the limitations of regionaloxidant models and compromises effortsto validate these models.4. Flame studiesThe local concentrations of both NOand NO2 within flames are required toassess the chemical kinetic mechanismsresponsible for the formation of NOX.Questions attendant to transformationof NO and NO2 in sample probes pres-ently limit the utility of fundamentalstudies that address NO and NO2 for-mation in combustion flows.

Sampling Conditions

Table I is a summary of the conditionstypically encountered when measuringcombustion product composition. Notethe wide variation of temperature andspecies concentration. The tempera-tures encountered (at the point of sam-ple extraction) divide into three generalgroups:

TemperatureGroup

moderatehighvery high

TemperatureRange

25°-600°C600°-1200°C

1200°-2500°C

Moderate temperature probing(25°-600°C) is the most frequently en-countered. Examples include flue andexhaust gas sampling from stationaryand mobile sources. High temperatureprobing is experienced in combustionresearch, especially in studies of secon-dary (post flame) combustion processes.Very high temperature probing is com-mon in flame research. Although flameresearch has historically been conductedin laboratory systems (premixed flames,diffusion flames, shock tubes, stirred

reactors, and plug flow reactors), com-bustion zones in practical combustionsystems are now being probed aswell.7-8

The function of the sample probe is toextract and cool the sample to a finaltemperature. (For high and very hightemperature probing, rapid expansionof the sample at the probe tip is em-ployed to terminate active reactions.)The final temperature is typically con-trolled (150° to 200°C) to prevent con-densation of water and hydrocarbons.The function of the sample line is tomaintain the final temperature andtransport the sample to the analyticalinstrumentation.

Chemical transformations of nitrogenoxides in the temperature range 25° to600° C are of special interest since (1)moderate temperature probing (25° to600°C) is the most frequently encoun-tered, and (2) regardless of the temper-ature at the point of extraction, thesample will typically have an extendedresidence time (seconds) at the finaltemperature (150° to 200° C) whileundergoing transport to the analyticalinstrumentation.

Available Information

A few general reviews of NO* sam-pling problems are available to assist inthe design of sampling systems.9"13

Additional information is available froma limited number of specialized com-bustion-related studies,14^17 fromstudies conducted to evaluate convertermaterials for chemiluminescent oxidesof nitrogen analyzers,18"20 and fromstudies conducted to explore the cata-lytic oxidation of CO in automobile ex-haust by O2 and NO.21-23

July 1977 Volume 27, No. 7 649

Table II. Homogeneous reactions.

Reference*1

Transformation Reaction COMB CONV OTHER

NO Oxidation (1) 2 NO + 0 2 2 NO2 9 ,14 58

NO2 Reduction (2) 2 NO2 *• 2 NO + O2 19 59

(3) NO2 + O »-NO + O2 17

NOx Removal (4)b NO + CH >-CHO + N 31,32

aCOMB: Combustion Related StudyCONV: Converter Related Study

bCH: Hydrocarbon

Summaries of the transformation re-actions that may be active in probes andsample lines are presented in Tables II,III, and IV for homogeneous, heteroge-neous, and catalytic reactions, respec-tively. (Catalytic reactions may be eitherhomogeneous or heterogeneous but areseparately grouped here for convenienceof presentation.) A review of the reac-tions is available.24

The work of Halstead, Nation, andTurner14 is the most definitive study ofchemical transformations of NO* whensampling combustion products. Com-bustion products were sampled from a"Tunnel Mixing Burner" operating onnatural gas and air. Two probe materials(stainless steel, 210 cm long X 6 mm I.D.,and silica tubing, 210 cm long X 4 mmI.D.) were evaluated for lean and richburn conditions. The temperature at theprobe inlet, measured with suction py-rometry, varied between 800° and1700°C. The temperature of the sampleat the outlet was near ambient. Thesample probe residence time was esti-mated to be 4 seconds. Lean fire condi-tions produced no change in NOX con-centrations for either the stainless steelor silica tubing. Changes were observed

for rich fire with the stainless steelprobe. In particular, the NOX concen-tration decreased in excess of 90%. Noeffect was observed for the silica. Al-though the results suggest that impor-tant chemical transformation occurswhen sampling fuel rich combustionproducts with stainless steel, importantquestions remain unanswered. For ex-ample, the extent to which the variousreducing species (e.g. CO, H2, and hy-drocarbons) participate in the reductionand removal reactions cannot be as-sessed. In addition, the temperaturegradient along the probe length preventsassessment of the sample conditions atwhich the reduction and removal reac-tions were activated.

A second study of note is reported byFew, Bryson, and McGregor.25 Nitricoxide was measured at the exhaust planeof a gas turbine combustor using twomethods—conventional probing and anoptical technique. The NO concentra-tions measured optically ranged from 3to 6 fold higher than those measured byconventional probing. Although im-portant questions remain unanswered(e.g. the concentration of NO2 and re-ducing species at the exhaust plane,

validation of the measurement oftransmissivity, and the inlet pressureconditions and sensitivity of the chem-iluminescent analyzer), the results re-inforce the probability that NO* may beremoved within probes and sample linesunder conditions encountered in prac-tice.

Experimental

An adequate accounting of NO*transformations requires that experi-ments be conducted to identify (1) theconditions for which chemical trans-formations occur, and (2) the extent towhich they occur.

An experimental study has been ini-tiated to assess NO* transformationsthat may be encountered when samplingexhaust gas from practical combustiondevices that operate air-rich (e.g. boilers,diesel engines, and gas turbine engines)and fuel-rich (e.g. automobile engines).A schematic of the experimental systemis shown in Figure 1. The experimentalsystem is designed to simulate the actualconditions experienced in samplinggaseous combustion products from thevariety of sources shown in Table I. Testparameters include carrier gas compo-sition, concentration and composition ofthe dopant gases, temperature, andprobe material.

A carrier gas simulating the primarycombustion products is selected fromone of three prepared sources of 0,1, and5% O2, 12% CO2, and balance N2. Thecarrier gas flow, 4 1/min, is doped withNO and NO2 metered from high con-centration source cylinders by means ofporous sintered metal flow restrictors.Additional species are introduced in anidentical manner. After doping, thecarrier gas enters a silica preheat oventhat raises the gas temperature to thedesired probe test temperature. From

Table III. Heterogeneous reaction.

Transformation Reaction COMB

Referencea

CONV OTHER

NO Oxidation

NO2 Reduction

NOV Removal

(5 )NO+O

(6) NO2+ metal

(7)NO2 + C

(8) NO2

wallNO,

wall•*- metal oxide + NO

wall-+- CO + NO

wall

(9)

(10)NO + C

NO,condensate

absorbedadsorbed

absorbed

1 x,

17

34

33

9, 12, 1434

12,37

wall(11)NO+ metal-

(12) NO2 +metalwall

wall

metal oxide + -„ N

metal oxide + -r N

20

20,60

20

29

29

35,36

a COMB: Combustion Related StudyCONV: Converter Related Study


Table IV. Catalytic reactions.

Transformation

A'O Oxidation

NO2 Reduction

NOx Removal

Reaction

(13)N0+ | 0 2 •-

\ i ' i j 1MVJ2 •»

(15) NO + CO *•

(16) 5 H 2 + 2 NO — -

NO2

NO + A O2

CO2 + -i N2

2NH3 + 2 H2O

COMB

9

10

9, 14

Referencea

CONV

18, 19,20,34,38

CAT

21,22,23

30, 39,40,41

a COMB: Combustion Related StudyCONV: Converter Related StudyCAT: Catalyst Study

this point, the doped carrier gas entersthe test probe. A test probe oven is usedto maintain the temperature of thedoped carrier gas at the test tempera-ture.

Test probe materials tested include4.6 mm I.D. 316 stainless steel and silicaglass (Vycor, Corning Glass Works). Thelength of each test probe is 2 m. Theresidence time of the doped carrier gasin the test probe is approximately \sec.

The gas temperature within the testprobe is incrementally varied from 25°to 400°C. Temperatures of the gasstream (T2 and T3) are measured withinsulated platinum resistance ther-mometers centered in the probe bore atthe inlet and outlet of the test probe.The oven temperature is also recordedby a thermocouple located adjacent tothe outer diameter of the test probe.

The NO and NO2 input levels to thetest probe (sample point 2) are chosen tobe 500 ppm and 75 ppm respectively.These levels simulate a NO concentra-tion selected as representative fromTable I, and a NO2 concentration whichmay be encountered in combustionsource effluents.

The present paper reports on chemi-cal transformations that occur in thepresence and absence of O2, CO, and H2.Oxygen levels are taken to be 0, 1, and5%; CO levels are taken to be 0, 100,1000, and 2500 ppm; and hydrogen lev-els are taken to be 0, 0.5, and 3.0%.

Gas composition is measured atsample points 2 and 3 to assess the ex-tent of NO and NO2 transformationwithin the 2 m test probe. Gas compo-sition is also measured at sample point1 to assess whether chemical transfor-mation occurs in the preheat oven.Sample lines leading from points 1, 2,and 3 are short, equidistant, and madeof 6.4 mm (V4 in.) O.D. TFE Teflon.Screening tests using varying lengths ofthe TFE Teflon were conducted to as-

sure that NO2 adsorption was not a sig-nificant factor in the present experi-ment.

Analysis of NO and NOX is conductedwith a Beckman Model 951H chemilu-minescent oxides of nitrogen analyzer.NO2 is determined by the differencebetween the measured NOX and NOconcentrations. The (carbon) converterefficiency is tested following the proce-dure outlined in the Federal Register.3

Carbon monoxide and H2 concentra-tions are measured using a BeckmanModel 315BL nondispersive infraredanalyzer, and a Beckman Model 7Cthermal conductivity analyzer respec-tively.

Results

The results are presented in Figure 2for oxidizing mixtures. Results for mix-tures with CO are presented in Figure 3.Results for mixtures with H2 are pre-sented in Figure 4. The percent changeof NO and NO2 represents the percentchange in concentration between sample

points 2 and 3 except where otherwisenoted. In the figures, points above thehorizontal temperature scale identifythose cases for which total NOX is con-served. In such cases, changes in NOconcentration are proportional tochanges in NO2 concentration. Pointsbelow the horizontal temperature scaleidentify those cases for which NO* is notconserved. The temperature shown isthe gas temperature (maintained uni-form) at sample points 2 and 3. The re-sults reported are summarized fromearlier presentations.24-26-27

Oxygen

The results for silica are presented inFigure 2a. No significant transformationis observed over the temperature rangeand the residence time studied.

316 stainless steel (Figure 2b) cata-lytically reduces NO2 to NO at gastemperatures in excess of 300° C. Theconversion of NO2 to NO at elevatedtemperatures is consistent with the re-sults of a variety of chemiluminescentanalyzer converter studies (Table IV).At temperatures below the catalyticallyactive temperature, no significantchange is observed.

Carbon Monoxide

The results for silica are presented inFigure 3a. No significant transformationis observed at temperatures up to andincluding 300°C. At 400°C, reduction ofNO2 to NO occurs.

The results for 316 stainless steel arepresented in Figure 3b. NO2 reductionis observed at 200°C and above. Thereduction is more pronounced at theelevated levels of CO concentration.

The exposure history of the stainlesssteel test probe is observed to alter thedegree of NO* transformation. Tem-perature cycling and prolonged exposureto one condition stabilizes the repro-

Resistancethermometers—

TestSample probe/

Rotameter

Sample

Carrier

U12% CO 2

0,1,5%02bal N2

NO/NOxanalyzer

Figure 1. Experimental system.

Three-wayvalves


15

14

13

12

11

SlO+i^ 9

a> °

1 7

o< 5

432

1

Test probe

Silica, 2 m

N0 x conserved -

25 100-& -

100

90

80

70 c£-H

60 ^g"o

50 -gcu

40 ^

3 0 ^

20

10

200Temperature,°C

300 400

Set point concentrations

NO: 500 ppmN02: 75 ppmC02: 12%02: 0,1,5%CO.OH2 :0N2: Balance

2 0 _CO

s40 I6 0 ^

o80 <i

100

15

1413

12

11

^10

* 9

Test probe" 316 Stainless, 2 m-

-

-

-

100


NO: 500 ppmN02: 75 ppmCO2: 12%02: 0,1,5%C0:0H2 :0N2: Bajance

200Temperature,°C

300 400

20-J5

40 |

60

80

100

Figure 2. Results with oxidizing mixtures:24 a) silica test probe; b) 316 stainless steel testprobe.

ducibility of the results. The effect ofprobe history may, in part, be attributedto the condition of the inner wall. Re-ducing atmospheres degrade the pro-tective oxide layer lining the inner wallof stainless tubes. Oxidizing atmo-spheres will renew the oxide layer. Otherevidence of probe history effects havebeen reported in the literature,11-28 but

a full assessment has yet to be made. Acontrolled experiment is presently inprogress to explore the effect of thestainless steel condition on nitrogenoxides transformation.

Of special note is the reduction of NO2observed in the silica preheat oven at theset point temperature of 400° C in thepresence of CO. (For such cases, the NO2

concentration must be increased and theNO concentration decreased at samplepoint 1 to maintain the set point condi-tion—500 ppm NO, 75 ppm NO2—atsample point 2.) The silica preheat tubeis identical to the silica test probe in-cluding the length (2 m). An importantdistinction, however, must be kept inmind when interpreting the data.Namely, the temperature of the samplein the preheat oven is not uniform, butundergoes an excursion from the ambi-ent to the set temperature.

Hydrogen

The results for H2 are presented inFigure 4. Chemical transformations fortwo H2 concentrations, 0.5% and 3%, areevaluated.

No significant chemical transforma-tion in silica is observed up to and in-cluding 300°C (Figure 4a). At 400°C, thechanges are dramatic and depend on H2concentration. At the lower H2 concen-tration of 0.5%, the NO2 is totally re-duced in the silica preheat oven. At theelevated H2 concentration of 3%, theNOX is totally removed in the silicapreheat oven. (Note that the set pointconcentration of 500 ppm NO, 75 ppmNO2 at sample point 2 was not attainedat 400° C. The concentrations of NO andNO2 were increased at Sample Point 1to offset the NO2 reduction and NO*removal in the silica preheat oven, butwere limited in the present experimentto a maximum of 125 ppm NO2, 890ppm NO.)

The formation of CO was observed at400°C with both test probes and 300°Cwith the stainless steel test probe. TheCO concentrations increased with H2percent, and reached levels approaching3500 ppm. The production of CO pre-sumably results from the reduction ofCO2 by H2. The presence of CO at theelevated temperatures likely contributesto the reduction of NO2 and removal ofNOJC observed.

Conclusions

• NOX is conserved in silica and 316stainless sample probes for thetemperature range 25°-200°C andresidence time of \ sec in the pres-ence of either CO, H2, or O2.

• NOX is removed in 316 stainless steelprobes at temperatures exceeding200°C and in silica probes at tem-peratures exceeding 300° C in thepresence of H2.

• The removal of NOX observed byHalstead, Nation, and Turner,14 andthe difference between optical andprobe measurements of NO ob-served by Few, Bryson, and McGre-gor25 may be caused by the attack onNO by reducing species such as H2within the probe and sample line.


• Additional information is needed toguide the selection of probe andsample line materials in order tominimize the occurrence of trans-formations and to estimate the ex-tent of transformations. In particu-lar, the effect of residence time,sample pressure, surface to volumeratio, probe history, alternativematerials, and the presence of hy-drocarbon species and particulatematter need to be assessed.

Acknowledgments

This study was performed at the UCICombustion Laboratory and sponsoredin part by a grant from the Air ForceOffice of Scientific Research, underGrant No. AFOSR-74-2710, and by theInstitute of Transportation Studies(ITS) Transit Management Programand the State of California. The U. S.Government is authorized to reproduceand distribute reprints for Governmentpurposes notwithstanding any copyrightnotation hereon.

The authors wish to extend their ap-preciation to Daniel E. Bleeker andRonald Benson (collection of data), andDewey Baker and John Taylor (designof the experimental system and main-tenance of the instrumentation).

References

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2. "Control of air pollution from aircraftand aircraft engines," Federal Register38 (136): 19088 (17 July, 1973).

3. "Control of air pollution from new vehi-cles and new motor vehicle engines,"Federal Register 39 (101):18075 (23 May,1974).

4. "Light-duty diesel powered trucks,"Federal Register 39 (205):37610 (23 May,1974).

5. "Emission regulation for new gasoline-fueled heavy duty engines," FederalRegister 40 (40):8482 (27 Feb., 1975).

6. D. Latimer and G. S. Samuelsen, "PlumeVisibility from Major Point Sources,"Report No. UCI-ARTR-75-4, UCI AirQuality Laboratory, University of Cali-fornia, Irvine, Sept., 1975.

7. L. J. Muzio and R. P. Wilson, "Experi-mental Combustor for the Developmentof Package Boiler Emission ControlTechniques," Report No. R2-73-292a,Environmental Protection Agency, July1973.

8. K. R. Krumwiede, D. M. Norton, G. W.Johnson, R. E. Thompson, B. P. Breen,and V. Quan, "A Probing Study of NOFormation in the Flame Zone of a 175MW Gas Fired Utility Boiler," Paper No.75-23.4, 68th Annual Meeting of the AirPollution Control Association, June,1975.

9. C. J. Halstead and A. J. E. Munro, "TheSampling, Analysis and Study of theNitrogen Oxides found in Natural Gas/Air Flames," I.G.T/A.G.A. Conference onNational Gas Research and Technology,Chicago, IL, 1971.

10. C. J. Halstead, "Sampling and Analysisof Combustion Products for Nitrogen

Oxides," Report No. SIG 71/8, Shell In-ternational Gas Limited, 1971.

11. J. H. Tuttle, R. A. Shisler, and A. M.Mellor, "Nitrogen Dioxide Formation inGas Turbine Engines: Measurementsand Measurement Methods," ReportPURDU-CL-73-06, Grant R-801284,Environmental Protection Agency, Dec,1973.

12. J. D. Allen, "A review of methods ofanalysis for oxides of nitrogen," J. last.Fuel 46 (384):123 (1973).

13. J. D. Allen, J. Billingsley, and J. T. Shaw,"Evaluation of the measurement of ox-ides of nitrogen in combustion productsby the chemiluminescence method," J.Inst. Fuel 47 (393):275 (1974).

14. C. J. Halstead, G. H. Nation, and L.

CD Q -

Test probeSilica, 2 m

-

•* N0 x conserved-

--

-

_

m m i-rv

25 100 200Temperature,°C


NO: 500 ppmN02: 75 ppmC02: 12%0 2 : 0CO: 100, 1000,2500 ppmH2: 0N2: Balance

-

-

-

•

-

-

-

o2500 ppm CO, ' '

, ' 1000 ppm CO

•' ^ -- " 100 ppm CO"

ttP~-~~~ >

300 400

100

90

80

70?-H

6 0 1o

5 0 1

4 0 ^o

3 0 ^

20

10

-40 «

60 xo

80-="

100

100


200 300Temperature,°C

400

NO: 500 ppmN02: 75 ppmC02: 12%02: 0CO: 100,1000,2500 ppmH2: 0N2: Balance

Figure 3. Results with carbon monoxide:26 a) silica test probe; b) 316 stainlessprobe.

20,5

40

8 0 ^

100

steel test


Turner, "The determination of nitricoxide and nitrogen dioxide in flue gas,"Analyst 97:55 (1972).

15. E. England, J. Houseman, and D. P.Teixeira, "Sampling nitric oxide fromcombustion gases," Combust. Flame20:439 (1973).

16. R. VV. Schefer, R, D. Matthews, N. P.Cernansky, and R. F. Sawyer, "Mea-surement of NO and NO2 in CombustionSystems," Paper No. WSS/CI 73-31,1973 Fall Meeting of the Western StatesSection/The Combustion Institute, ElSegundo, CA, Oct., 1973.

17. J. D. Allen, "Probe sampling of oxides ofnitrogen from flames," Combust. Flame24:133 (1975).

18. J. A. Hodgeson, J. P. Bell, K. A. Rehme,K. J. Krost, and R. K. Stevens, "Appli-cation of a Chemiluminescence Detectorfor the Measurement of Total Oxides ofNitrogen and Ammonia in the Atmo-sphere," Paper No. 71-1067, presented at64th Annual Meeting of APCA, 1971.

19. J. E. Sigsby, F. M. Black, T. A. Bellar,and D. L. Klosterman, "Chemilumines-cent method for analysis of nitrogencompounds in mobile source emissions(NO, NO2, and NH-,)," Environ. Sci.Technol. 7 (1):51 (1973).

20. L. P. Breitenbach and M. Shelef, "De-velopment of a method for the analysisof NO2 and NH3 by NO-measuring in-struments," J. Air Poll. Control Assoc. 23(2):128(1973).

21. R. A. Baker and R. C. Doerr, "Catalyzednitric oxide reduction with carbon mon-oxide," Ind. Eng. Chem., Process DesignDevelop. 4 (2):189 (1965).

22. M. Shelef, K. Otto, and H. Gandhi, "Theoxidation of CO by O2 and by NO onsupported chromium oxide and othermetal oxide catalysts," Catalysis 12:361(1968).

23. J. R. Ayen and Y. Ng, "Catalytic reduc-tion of nitric oxide by carbon monoxide,"Int. J. Air Water Poll. 10 (1):1 (1966).

24. G. S. Samuelsen and J. Harman,"Transformation in Oxides of NitrogenConcentration While Sampling Com-bustion Products," Presented at the 1stInternational Chemical Congress,Western Hemisphere, American Chem-ical Society, Mexico City 1975.

25. J. D. Few, R. J. Bryson, and W. K.McGregor, "Evaluation of Probe Sam-pling Versus Optical In Situ Measure-ments of Nitric Oxide Concentrations ina Jet Engine Combustor Exhaust," Re-port AEDC-TR-76-180, Arnold Engi-neering Development Center, Jan.,1977.

26. R. Benson, G. S. Samuelsen, and R. E.Peck, "Oxides of Nitrogen Transforma-tion While Sampling Combustion Prod-ucts Containing Carbon Monoxide,"WSS/CI Paper 76-11, 1976 SpringMeeting of the Western States Section/The Combustion Institute, Salt LakeCity, UT, 1976.

27. R. Benson and G. S. Samuelsen, "Oxidesof Nitrogen Transformation WhileSampling Combustion Products Con-taining Carbon Monoxide and Hydro-gen," WSS/CI Paper 76-39, 1976 FallMeeting of the Western States Section/The Combustion Institute, La Jolla, CA,1976.

28. E. E. Peterson, J. Landau, and E. Squc-edo, "Micro and Macro Changes in aStainless Steel Catalyst During Reduc-tion of NO," in R. L. Klimisch and J. G.Larson (eds.), The Catalytic Chemistryof Nitrogen Oxides, Plenum Press, NewYork, 1975, pp 119-131.

29. Robert M. Siewert, "Hydrogen interfer-ence in chemiluminescent NOX analysis,"Combust. Flame 25:273 (1975).

30. A. Lamb and E. L. Tollefson, "Catalytic

reduction of nitric oxide in the presenceof oxygen in low concentration high ve-locity gas streams," Can. J. Chem. Eng.53(1 ):68 (1975).

31. A. L. Myerson, "The Reduction of NitricOxide in Simulated Combustion Ef-fluents by Hydrocarbon-Oxygen Mix-

Test probe

Silica, 2 m

ture," Fifteenth Symposium (Interna-tional) on Combustion, The CombustionInstitute, 1975 pp 1085-1092.

32. A. L. Myerson and D. W. Blair, "Reduc-tion of nitric oxide in automobile engineexhaust by ethane-air injection," Envi-ron. Sci. Technol. 10 (5):461 (1976).

All N02 reducedin silica

preheat oven

-NOY conserved

25 100


NO: 500 ppmN02: 75 ppmC02: 12%02 : 0CO:0H2: .5,37oN2: Balance

200Temperature,°C

300 400

-N0 x removed-\—

NAil N0xremoved.* in silicav .^preheat oven

20 „g

40 I

60 xoz

80 <

100

100 200Temperature,°C


NO: 500 ppmNO2: 75 ppmCO?: 12%0./. 0CO: 0H2: .5,3%No: Balance

300 400

NOX removed -

All NOX removedin silica preheatoven (3% H2)~

2 0 1o

40 I60 *

o

80 <

100All N02 reducedin silica preheatoven (.5% H2)

Figure 4. Results with hydrogen:27 a) silica test probe; b) 316 stainless steel test probe.


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