Emission Measurements of Various Biofuels using a Commercial Swirl-Type Air-Assist Dual Fuel Injector
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A joint university-industry research program funded by Rolls-Royce Canada, NSERC and CRIAQ is actually pursued at Université Laval to characterize the combustion performance of liquid (biodiesel blends) and gaseous (syngas blends) biofuels in terms of emissions & smoke and lean blow out. The final objective of the proposed research is to characterize the most promising liquid and gaseous novel biofuels for use in industrial gas turbines in order to reduce greenhouse gases and potentially operation costs. These combustion tests allowed the characterization of standard diesel fuel as a baseline plus two biodiesel blends as well as standard methane as a baseline plus ten syngas blends (CH4, H2, CO and CO2) in order to evaluate the emissions of the main pollutants (CO, CO2, NOx, UHCs and smoke). Combustor exit and wall temperature measurements were also taken to characterize adequately the boundary conditions for future CFD simulations. The flame was contained in a quartz tube combustor operating at ambient outlet conditions and the fuel was delivered through a commercial swirl-type, airblast dual fuel atomizer. The air mass flow rate was kept constant for all fuels to maintain the same pressure drop (ΔP) across the fuel injector while the fuel flow was varied to cover equivalence ratios from 0.5 to 1. A probe connected to a FTIR/FID/O2 gas analyzer system and a smoke filter was fixed to a 3D-axis traverse in order to sample combustion products in a cross pattern at the combustor exit. This way, concentrations of various emissions were obtained at five radial positions. Burned gases and wall temperatures were measured with thermocouples along the test rig. This paper reports the findings of these experimental tests and presents the comparisons of the biofuels with baseline fuels to identify some benefits of these novel biofuels while maintaining an acceptable overall combustion performance.
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Emission Measurements of Various Biofuels using a Commercial Swirl-Type Air-Assist Dual Fuel Injector
- 1. Joachim Agou, Alain deChamplain, and Bernard Paquet Emission Measurements of Various Biofuels using a Commercial Swirl-Type Air-Assist Dual Fuel Injector CI/CS 2013 Spring Technical Meeting Université Laval, Quebec City May 13-16, 2013
- 3. Overview A joint university-industry research program Funded by Rolls-Royce Canada, CRIAQ, NSERQ, and MITACS Pursued at Université Laval Combustion Laboratory “Characterize the combustion performance” of liquid and gaseous biofuels on a generic combustor Baselines & Biofuels standard diesel as a baseline 3 biodiesel blends standard methane as baseline 10 syngas blends 5/15/20133 Test Program
- 4. Fuels Characteristics 5/15/20134 Test Program Liquid Fuels Diesel No.2 (% vol.) Bio-diesel (% vol.) Diesel (baseline) 100 0 B20 80 20 B50 50 50 B100 0 100 Gaseous Fuels H2/CO ratio CO (% vol.) H2 (% vol.) CH4 (% vol.) CO2 (% vol.) N2 (% vol.) Methane (baseline) 0 0 100 0 0 B1 - 0 0 60 40 0 S1 0.5 50 25 0 25 0 S2 1 37.5 37.5 0 25 0 S3 2 25 50 0 25 0 S4 0.5 50 25 5 20 0 S5 1 37.5 37.5 5 20 0 S6 2 25 50 5 20 0 S14 1 42.5 42.5 0 15 0 S5M50 1 18.75 18.75 52.5 10 0 S5M25 1 28.125 28.125 28.75 15 0
- 5. What has been measured ? 5/15/2013Test Program5 Gaseous emissions Smoke (SN) Temperatures Ignition Flame stability Lean blowouts (LBO)
- 6. Experimental Setup Test Rig and Instrumentation 5/15/20136
- 7. Custom Test Rig 5/15/2013Experimental Setup7
- 8. Instrumentation 5/15/2013Experimental Setup8 A probe connected to a gas analyzer system and a smoke sampler mounted on a 3D-axis traverse that allow displacement. Samples of combustion products are drawn in a cross pattern at the combustor exit. 5 different radial positions to get an emission profile at exit plane. Burned gas temperature was measured at the center of the exit plane Wall temperatures were measured at several locations along the test rig All measurements with type-K thermocouples.
- 9. Smoke & Emission Equipment 5/15/2013Experimental Setup9 Smoke Measurement • A designed smoke sampler. • Smoke Number (SN) determination via SAE procedure found in ARP 1179. • Soot samples collected by passing a predetermined volume of exhaust sample through paper filter via heated lines to prevent condensation. • Reflectometer is used to measure reflectance of clean & stained filter to calculate smoke number (SN).
- 10. Smoke & Emission Equipment 5/15/2013Experimental Setup10 Gasmet™ CEMS – Gas Analyser • Continuous Emission Monitoring System (CEMS) • Fourier Transform InfraRed (FTIR) technology • Simultaneous analysis up to 35 gaseous substances (extensible library) • H2O, CO2, CO, SO2, NO, NO2, N2O, HF, NH3, O2, O3, many HC volatiles … • No diatomic molecules (O2 and noble gases) FID – UHC Analyzer • Flame Ionization Detector (FID) • Total hydrocarbon analyzer • High accuracy with Hydrocarbons ZrO2 – Oxygen Analyzer • Only O2
- 13. Results & Discussion Emissions vs. Equivalent ratio 5/15/201313
- 14. Water Vapor & Carbon Dioxide 5/15/2013Results and Discussion14 Concentrations increase with equivalent ratio. Good agreement with theoretical trends. H2 & CH4-composed fuels generate greater amount of water vapor. 0 5 10 15 20 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 vol-%(wet) Phi 0 5 10 15 20 25 30 35 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 vol-%(dry) Phi CH4 B1 S1 S2 S3 S4 S5 S6 S14 S5M25 S5M50 Diesel B20 B50 CH4 Gas Eq Heptane Gas Eq
- 15. Oxygen O2 (Zr-O2) 5/15/2013Results and Discussion15 Concentration decrease to 0% with equivalent ratio reaching stoichiometric φ. Gaseous fuels follow closely theoretical trends. Liquids fuels give slightly higher concentrations Suggest local excess air O2 calculated, not measured Carbon/O2 balance add uncertainty 0 5 10 15 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 vol-%(dry) Phi CH4 B1 S1 S2 S3 S4 S5 S6 S14 S5M25 S5M50 Diesel B20 B50 CH4 Gas Eq Heptane Gas Eq
- 16. Nitrogen Oxides (NOx) 5/15/2013Results and Discussion16 NOx=NO+NO2 T>>1500ºC Thermal NO formed in large quantities NO is found to peak to close to fuel-lean side of stoechiometric φ NO production declines very rapidly as temperatures are reduced at low φ CO2 reduces peak flame temperature Liquid fuels drops : potential for near- stoichiometric combustion temperature 0 200 400 600 800 1000 1200 1400 0 10 20 30 40 50 60 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 GasEq ppmv(corrected15%-O2,dry) Phi NOx CH4 B1 S1 S2 S3 S4 S5 S6 S14 S5M25 S5M50 Diesel B20 B50 CH4 Gas Eq Heptane Gas Eq
- 17. Carbon Monoxides (CO) 5/15/2013Results and Discussion17 CO = Inefficient mixing and/or incomplete combustion. Significant amount of CO due to dissociation of CO2 close to stoichiometric φ. CO arises from incomplete combustion at low φ inadequate burning rate and/or unsufficient residence time. Liquid fuels emissions increase while φ increase Mean drop size affects evaporation high volume occupied by evaporation = less available volume for chemical reaction. 1 10 100 1000 10000 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 ppmv(corrected15%-O2,dry) Phi CH4 B1 S1 S2 S3 S4 S5 S6 S14 S5M25 S5M50 Diesel B20 B50 CH4 Gas Eq Heptane Gas Eq
- 18. Unburned Carbons (UHC) and Soot 5/15/2013Results and Discussion18 UHC = unburned fuel (drops or vapor) UHCs Poor atomization and/or inadequate burning rate. Relatively low UHC for all gaseous fuels high swirl capabilities = Good air/fuel mixing. Liquid Fuels limitations: droplets impingements on combustor wall interfered combustion = High soot generation ! Soot = Solid carbon 0 10 20 30 40 50 60 0.1 1 10 100 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Smokenumber(SN) ppmv(corrected15%-O2,dry) Phi CH4 B1 S1 S2 S3 S4 S5 S6 S14 S5M25 S5M50 Diesel B20 B50 Smoke Diesel Smoke B20 Smoke B50
- 19. Conclusions and Recommendations Experimental issues Wobbe index 5/15/201319 Almost there !
- 20. Summary and Conclusions 5/15/2013Conclusion and Recommendations20 • Emissions & smoke measurement. • Operability indicators. Characterize alternate liquid & gaseous fuels on a generic combustor • Massive droplet impingements. • Intermediate size quartz tube ? • High accumulations of black soot along the quartz tube wall. Test rig not fully adequate for liquid fuel combustion • Only the primary zone was simulated. • Missing feed holes in the liner that promote mixing and prevent droplets from reaching combustor wall. Working conditions far from real conditions in gas turbine
- 21. Summary and Conclusions 5/15/2013Conclusion and Recommendations21 • Much simpler combustion process. • Almost no soot. • S3 and S6 seem the most promising fuel regarding: • Relatively low NOx, CO and UHCs emissions generated. • Very competitive Wobbe Index compared to baseline. Gaseous fuel emissions 1 10 100 1000 10000 100000 Center Center Center Center Center Center Center Center Center Center Center Center Center Center1 1 1 1 1 1 1 1 1 1 1 1 1 1 B1 B20 B50 CH4 Diesel S1 S14 S2 S3 S4 S5 S5M25S5M50 S6 ppmv(log) NOx ppm dry Carbon Monoxide CO ppm dry UHC (FID) ppmC dry 1 10 100 1000 Center Center Center Center Center Center Center Center Center Center Center Center Center 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 B1 B20 CH4 Diesel S1 S14 S2 S3 S4 S5 S5M25S5M50 S6 ppmv(log) NOx ppm dry Carbon Monoxide CO ppm dry UHC (FID) ppmC dry 1 10 100 Center Center Center Center Center Center Center Center Center Center Center 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 B1 CH4 S1 S14 S2 S3 S4 S5 S5M25 S5M50 S6 ppmv(log) NOx ppm dry Carbon Monoxide CO ppm dry UHC (FID) ppmC dry 0 20 40 60 80 100 WobbeIndex (MJ/Nm3) Biofuels Baseline
- 22. Thank you for your attention. 5/15/2013Finally !22 Any questions ? Contact me at j@agou.ca
- 23. 5/15/201323
- 24. Back up slides
- 25. Sulfur Species (SO2) 5/15/2013Results and Discussion25 Primary sulfur component in syngas is hydrogen sulfide. Biofuels nearly sulfur-free relatively low sulfurous emissions. Sulfur species are oxidized primarily to SO2. Some of SO2 undergoes further oxidation to SO3. Partitionning between SO2 and SO3 and reduced species depends on the combustor performance and gas mixing . 0 2 4 6 8 10 12 14 16 18 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 ppmv(corrected15%-O2,dry) Phi CH4 B1 S1 S2 S3 S4 S5 S6 S14 S5M25 S5M50 Diesel B20 B50
Editor's Notes
- Good morningladies and gentlemen. Thankyouverymuch for chosingthisside of the conference. Mynameis Joachim and I amdelighted to beheretoday to talk to you aboutemissionsMeasurements of variousbiofuelsusing a commercial swirl type air assist dual fuel injector.
- My talk isdivided in 2 parts. I'llstart by definemyexperimentalproject and the equipmentusedduring the tests then I will look atmyresults and finalllyI willbeglad to answerany questions thatyoumay have at the end.First of all, test program
- The goal of thisstudyis to characterize the combustion performance of alternateliquid and gaseous fuels on a genericcombustorThis effort waspursued in response to growinginterest to addflexibility in burningbiofuelsconsideringverylimited information availableregarding the effects of biofuels on pollutantemissions.This jointuniversity-industryresearch program wasfunded by industrialspnsorssuch as Rolls-Royce Canada and pursuedat Laval University Combustion Lab.The biofuelsusedduring the tests are 3 biodiesels blendswith standard diesel as a baselineAnd 10 syngasblendswith standard methane as baseline.
- Here is a detailled list which shows the proportions of compounds which constite the different biofuels used during the testB20, B50, B100. The number indicates the percentage of biodiesel in the total blendRegarding the syngas, they are composed of different proportions of CO, H2, CH4 and CO2. All these blends has been made here at laval university by mixing the different gases with MFC generously lent by Matthew Johnson From Carleton University.You can notice that S1 has the highest ratio of CO while S3 the highest ratio of H2, B1 the the highest ratio of CO2It should be expected that each of these syngas will burn in a unique way and generate a range of combustion products of varying composition
- This leads me to mynext point, whichis…
- Regarding the custom test rig: Basically, it consists of a stainless steel platform which host an injector. To represent the primary zone of a gas turbine combustor, the combustion chamber is confined in a quartz tube with almost unrestricted optical access. The base plate with manifold is adapted to mount the swirl-type air-assist fuel injector. This injector is coming from a commercial Trent 60 WLE Dual Fuel gas turbine; generously provided by Rolls Royce Canada. This atomizer has high swirl as well as dual fuel capabilities.Finally, a stainless steel cone which serves as restriction at the exit to simulate the pressure drop generated by a turbine stage is mounted atop the quartz tube.In these pictures, you can see an overview of the experimental setup in liquid fuel configuration with Test rig burning dieselLiquid fuel tankThe air supplied from university compressor== all of this control by high precision coriolis flow meterThe gas analysersA traverse which support a probe and the smoke sampler
- Now, I’d like to look at the instrumentation:Basically, a stainless steel probe ( in others words , a ¼ inch tube) connected to a gas analyser system and a smoke filter mounted on a 3d axis traverse that allows displacement of the probe at the exit Read slideInstrumentation allows monitoring of the air and fuel mass flows , inlet air tenmperatures and pressure, combustor wall and exit temperatures, and exhaust gas composition.
- A designed smoke sampler is used to determinate the smoke number (SN) following the SAE procedure found in Aerospace Recommended Practice ARP1179. The soot samples are collected by passing a predetermined volume of exhaust sample at a certain flow rate through a specific type of paper Filters (PICTURE) A reflectometer is used to measure the absolute reflectance of the clean filter paper as well as the stained filter to calculate the smoke number (SN).
- Regarding the gasanalysers modules (PICTURE) , I wont go to much in the details … molecular vibration , infraredspectrums, beer’slaw, how itworks, and so on…However, I’ll drop few words about whodoeswhat.Most of the emissionswerequantifiedusingthisdeviceRead slide
- Lights off … we are ready to startexperimental tests.Whatyousee right nowis the typicalatmosphere of tests…. Relativelystrong vibrations, a lot of noise, high temperaturesit’svery hot …. 1300 degreeat the combustor exit 2 persones: 1 cheching the mass flow rates and temperatues and me taking care of the emmisionsmeasurements.
- Inthisslide, I justwanted to show you the range of flames I gotduringmy tests withdifferent test rig configurations. I wouldsay 95 % of the time, I gotniceartistic combustion with few exemples of SYNGAS and BIODIESELS. 4% of time, itwas a lot of sootgeneratedespeciallyatstoichiometricequivalence ratio due to spray dropletsimpingements on the combustorwalls. I’llexplainlater how it affects the emmision. And 1% of the time, it’srandomexperimental surprises …. likethis REDISH FLAME due to a corruptedPraxairgascylinderwithIronPentaCarbonyl or Righthere … probably a leak or something.Finally, ittookseveralmonths to completethewholeexperimental program to adapt the differentexperimentalconfigurations required for each fuel and the several issues and challenges for the handling of compressedgases.
- Right, let's move on to RESULTSI’veonlyselected few results as wedon’t have have a lot of timeOnly the main pollutants are presentedatdifferentscales – wet, dry, or corrected to 15% O2on a dry basis – depending on their relevance.The numerousemissionresults are compared to equilibrium values thatwerecalculatedusing a commercial software (GASEQ) atadiabaticflametemperature for the twobaselines: methane for gaseous fuels and diesel for liquid fuels in order to ensure data validation. In addition, the resultsdisplayed in thisstudywereaveraged and summarized in a compact format formaximum information.
- Water Vapor, CarbonDioxide. Water vapor :concentrations increasealmostlinearlywithequivalent ratio (ϕ) These 2 indicators are in good agreement with the theoretical trends weshouldget for emissions. It canalsobeobservedthat the gaseous fuels generate the greateramount of water vapor for thosemixtures composedwith the largest proportion of hydrogen and methane. In our case, S3 and S6 are composed of 50% hydrogen and generate the most water vapor
- Oxygen concentrationdecreases to 0% at an equivalent ratio of 1 when all the air isconsumed by the fuel. Regarding the amount of oxygenleftfollowing combustion, the gaseous fuels seem to followclosely the theoreticalvalues. On the other hand, the experimentalmeasurements for liquid fuels giveslightlyhigher O2 concentrations, suggesting local excess air at the measured points. It shouldbealsonotedthatthese O2values werecalculatedbasedon a carbon/oxygen balance since the Zr-O2 analyzercould not beactivated for safety issues; thiscanadduncertaintyto these values.
- The primary NOX component of interestduring the combustion of syngasis NO, especially for itsstrongcontribution.(Thermal )NO isformed in appreciablequantitiesatelevated combustion temperaturesaround ~1 500°C whichis more thanourcase.Indeed, NO formation isfound to peak close to the fuel-leanside of stoichiometricϕ. This is a consequence of the competitionbetween fuel and nitrogen for the availableoxygen. Although the combustion temperatureishigher on the slightlyrichside of stoichiometricϕ, the availableoxygenisthenconsumedpreferentially by the fuel.NOx production declinesveryrapidly as temperatures are reducedatlowequivalence ratio (ϕ ≅ 0.6). Thermal NO isdominated by temperatureeffectconsequently fuel composition caninfluence temperatureespeciallywhen the gaseous mixture has a large proportion of CO2 like B1, S1, S2, S3;thereby the lowestNOxemissions. CO2 does not participate in the combustion process. Consequently CO2 reducepeakflametemperature by diluting and absorbingheatfrom the combustion product.Combustorresidence time canalso influence NOxemissionswhichcanincreasewith a longer residence time, except for verylean mixtures (ϕ ≅ 0.4), for which the rate of formation issolowthatitbecomesfairlyinsensitive to time. Fromourexperimentalresults, thiseffect on NO formation seems to berelated to the amount of hydrocarbon content in the fuel mixture. In fact, fuels generating the largestamount of NOx are the diesel/biodiesel blends, CH4 and S5M50. As hydrocarbon-content fuels are introduced, theirhigherflametemperaturepromoteadditional prompt NO formation.
- Carbonmonoxides in syngas combustion products has twoprimary sources: unburnedsyngas CO, resultingfrom inefficient mixingthatyieldsequivalenceratios outside the ignition range, and incomplete combustion of hydrocarbonspecies in the syngas. When the combustion zone isstoichiometric or becomingmoderatelyfuel-lean, significantamounts of CO ispresent due to the chemical dissociation of CO2. In practice, CO emissions are found to bemuchhigherthanpredictedfromequilibriumcalculations and to behighestatlow-power conditions, whereburning rates and peaktemperatures are relativelylow. This is in conflictwith the predictions of equilibriumtheory and itsuggeststhatmuch of the CO arises fromincomplete combustion of the fuel, probablycaused by an inadequateburning rate in the quartz tube due to a fuel/air ratio thatistoolow and/or insufficientresidence time.Fromourexperimentalresults,CO emissionsdiminishwith an increase in the equivalence ratio, reaching minimum values aroundϕ ≅0.5~0.6 depending on the fuel, anyfurtherincrease in the equivalence ratio causes CO emissions to rise. These trends are typical of thoseobserved for other types of combustion systems.
- UHCs are normallyassociatedwithpooratomization, inadequateburningrates, or anycombinedeffects. Regardingunburnedhydrocarbonlevels, the measuresrecorded by the FID as well as the FTIR show relativelylow UHC emissionsfor all gaseous fuels. In fact, UHCsneverreallyexceeded more than 10 ppm. These good results are likely due to the high swirlcapabilities of the fuel injector to ensure excellent mixing of the fuel with air.However, limitationhave been reachedwithliquid fuels. Indeed, high spray dropletsimpingements on the combustorwalls have certainlyinterfered in the combustion process and affected the emissions in thisway (pictures). Therefore, the amount of sootgenerated by diesel and bio-dieselisquite impressive especiallyatstoichiometricϕ. As shown on the graph, the smokenumberincreasesveryfast as wegetcloser to stoichiometricϕ.
- That brings me to the end of mypresentation
- Thankyou all for listening, itwas a pleasurebeingheretoday.If you have any questions, pleasedon'thesitate to askIf you have anyfurther questions, I willbe happy to talk to youat the end.