Polycyclic aromatic hydrocarbon formation under simulated coal seam pyrolysis conditions

Mining science and Technology( china)21(2011)605-610Contents lists available at Science Direct氵容Mining Science and Technology( China)ELSEVIERjournalhomepagewww.elsevier.com/locate/mstcPolycyclic aromatic hydrocarbon formation under simulated coal seamyrolysis conditionsLiu Shuqin", Wang Yuanyuan, Wang Caihong, Bao Pengcheng, Dang JinliSchool of Chemistry and EnvironEngineering China Untversity of Mining G Technology(Beifing). Beifing 100083, ChinasTate Key Laboratory of Coal-Based Carbon Energy, Langfang 065001,ChinaARTICLE INFOA BSTRACTArticle histoCoal seam pyrolysis occurs during coal seam fires and during underground coal gasification. This is arReceived 12 December 2010Received in revised form 8 January 2011important source of polycyclic aromatic hydrocarbon( PAh)emission in China. Pyrolysis in a coal seamAccepted 10 February 2011was simulated in a tubular fumace. The 16 US Environmental Protection Agency priority controlled PAHsAvailable online 26 July 2011were analyzed by HPlc. The effects of temperature, heating rate pyrolysis atmosphere, and coal sizewere investigated. the results indicate that the 3-ring PAHs AcP and AcPy are the main species in thepyrolysis gas. The 2-ring NaP and the 4-ring Pyr are also of concem. Increasing temperature causedthe total PAH yield to go through a minimum. the lowest value was obtained at the temperature of00C Higher heating rates promote PAH formation, especially formation of the lower molecular weightPAHs. The typical heating rate in a coal seam 5C/min results in intermediate yields of PAHs. The totalPAHs yielatmosphere of Nz is about 1.81 times that seen without added N2, which indicates thatan air filogh the coal seam accelerates the formation of PAHs. An increase in coal particle sizereducesPAHs emission but promotes the formation of 5-and 6-ring PAHs.o 2011 Published by Elsevier B.V. on behalf of China University of Mining Technology1 Introductionin a coal field fire produces about 10 mg of benzo apyrene(Bap).which is highly carcinogenic. Coal field fires not only waste energy.Polycyclic aromatic hydrocarbons(PAHs)are hydrocarbons but also destroy the local environment including the atmospherecontaining two or more fused benzene rings. they are environmen and the groundwatertal pollutants and are considered a health concern due to theirCoal seam gasification, or underground coal gasification, is thepotential carcinogenic, mutagenic, and toxic characteristics, as well process of controlled combustion and gasification of a virgin coalas for the possible synthesis of dioxins from them. therefore, PAHs seam. It has been regarded to be an important way to utilizehave been listed as priority controlled pollutants by most of low-rank and un-mineable coals [5-7countnesCoal seam pyrolysis is the main process that occurs duringe These compounds are typically introduced into the environ- both coal field fires and coal seam gasification. This differs fromnt through the burning of fossil fuels such as petroleum and surface coal combustion, or gasification, because the coal seamcoal [1, 2]. In China, PAHs are mainly produced by coal combustion is fixed underground and the fire face moves forward to enlargeeither naturally occurring, such as coal field fires, or man-made the area subject to pyrolysis. Since pyrolysis is located behindsuch as in a coal fired boiler [3].the actual combustion area any PAHs produced by pyrolysis willCoal field fires are major disasters that occur naturally. Statisti- enter the final stream of flue or fuel gas. Therefore, coal seamcal records prepared in 1994 by the Chinese government and the pyrolysis is one important source for PAHs formation andEuropean Union showed that 56 regions in northwest China discharge.suffered coal field fires having a total burning area of 17-20 kmIn recent years, PAHs formation during coal boiler combustionaccounting for a loss of 4. 22 billion tons of coal (4 These coal field has been investigated [8-16]. Research on PAHs formation andfires have resulted in the release of hundreds of thousands of tons emission during coal seam combustion and pyrolysis has not beenof pollutants, such as NO, CO, and So2, to the atmosphere, includ- reported In this paper, we describe a simulated coal seam pyrolysising large amounts of PAHs. It has been estimated that 1 kg of coal taking Wulanchabu lignite as a sample and examining the resultinggas produced. The aim is to obtain information related to PAHsformation and those factors that affect it. The results are expected4 Corresponding author Tel +86 10 62331897to provide scientifio data "sefil for control nf organic pollutantsE-mailaddresscumtlsq@sohu.com(s.Liju)from coal field中國煤化工attion1674-5264/s- see front matter e 2011 Published by Elsevier B V on behalf of China University of MiningCNMHGdo:101016/mstc20102027s Liu et al/ Mining Sdence and Technology( China)21(2011)605-6102. ExperimentalTable 1Proximate and ultimate analysis of the coal sample(air dried, dry and ash free)(%)2.1. Coal sample preparationUltimate analysisauf Caat Hdaf Odaf NdalWulanchabu lignite, from northwest China, was used for simu-239615.144470553073.3349817180973.55lating the coal seam pyrolysis. The proximate and ultimate analy-ses are listed in Table 1. Drilled cores 60 mm in diameter werecoal samples of different sizes. The samples were first dried etaken from local mines and then crushed and sieved to prepare3. Results and discussion105C for 1 h before the experiments.3. 1. Efect of temperature on PAH fc2.2.Simulated coal seam pyrolysis and collection of PAHsThe effect of pyrolysis temperature on the formation and distri-A laboratory-scale tubular furnace was used to simulate coal bution of PAHs was investigated. The results are shown in Fig 3seam pyrolysis, see Fig. 1. The furnace has a gas supply section, a The total PAH yield during coal seam pyrolysis passes through aheating section, and a sampling section. The heating section had minimum as the temperature increases: The lowest value isa programmable temperature control and could be adjusted from obtained at 600C. At temperatures above 600C the total PAHroom temperature to 1200C. The sampling section was a cooling content rises dramatically. The PAHs produced from the test coaldevice, a conical flask filled with dichloromethane solvent, and a at the various temperatures used were mainly 3-ring PAHs.Thesampling tube filled with XAD-2 resin.content of these PAHs was from 64.05% to 85. 59% As the temper-Forty grams of coal were accurately weighed into a quartz boat ature rises the yield of 3-ring PAHs changes in a way similar to thefor each trial. The PAHs in the gas produced by pyrolysis were total PAH yield, The minimum amount for this fraction iscooled and captured in the dichloromethane or the XAD-2 absorp- 64.20 mg/kg and occurs at 600%c.tion column. the XAD-2 resin was used to insure complete trap-Changes in the concentration of 4, 5, and 6-ring PAHs are notping of PAHs. The pyrolysis temperature was varied from 400 toso obvious and the maximum values were obtained over the tem800C at 100C intervals. The heating rate to temperature ranged perature range from 500 to 600 C The yield of 2-ring PAHsfrom 5 to 40C/min Preferred conditions are typical of coal seamincreases slightly with increasing temperature and has a maximumpyrolysis and consisted of a temperature of 600C with a slowvalue at 800heating rate of 5C/min. the pyrolysis atmosphere was either NThe distribution of the different PAh species versus temperatureis illustrated in Fig. 4. AcP and AcPy, the two 3-ring PAHs, are theor no N2, and the coal sizes included pulverized coal sized from main species produced by coal seam pyrolysis. These two com-75 to 150 um and lump coals sized about 1 and 2 cm.pounds account for 59. 10-83. 44% of the total PAH yield. The 2-ringNaP is the second most common. the yield of NaP increases with2.3. Sample pretreatmenttemperature also. the highest value(33 32 mg/kg)was observedat a pyrolysis temperature of 800C, which accounts for 19. 29% ofThe dichloromethane solvent and the XAD-2 resin adsorbent the total PAH yield. Also note that Pyr. the dominant 4-ring PAH,were both extracted for 8 h in a Soxhlet apparatus. After dehydra- has its maximum at 600 c and then changes only slightly at highertion by anhydrous sodium sulfate the extract was concentrated in a temperatures. Four 5-ring PAHs have an irregular variation overrotary evaporator followed by a Kuderna-Danish(K-D)vessel to a temperature. The 6-ring BghiP occurred in a yield of 0.50 mg/kg atfinal volume of 1 mL The condensate was purified with a silica col- lower temperatures but cannot be seen above 600oC.umn using 4: 6(v/v)n-pentane/dichloromethane as the eluent andPAH formation during coal seam pyrolysis is attributed to threea flow rate of 2 mL/min. The collected materials were re-concen. pathways (17: (1)The emission of free PAHs that were originallytrated by purging with ultra-pure nitrogen to a final volume of present in the raw coals; ( 2) The decomposition of aromatic com-I mL prior to analysis. All the experiments were repeated threepounds present in the coal macroscopic structure: (3) The combi-times. Finally, the samples were stored in brown vials and refriger- nation of free radicals that occurs at high temperatures. Theated at4°molecular structure of coal is a three-dimensional network of con-densed aromatic and hydro-aromatic units connected by weaker2.4. PAH analysisbonds. Upon heating some PAHs that are bound into the coal struc-ture by hydrogen bonds or Van der Waals forces are initially freedThe PaH analysis was performed using a Shimadzu LC-20AT into the gas phase. Then the coal structure undergoes major phys-HPLC system equipped with dual, high-pressure gradient elution ical and chemical changes that allow different types of aromaticsdevices and a special PAH specific chromatographic column cyclic hydrocarbons, and alkyl structures to be produced as vola(LC-PAH, 5 um x 4.6 mm x 250 mm). A 10 HL sample was injected tiles products, i.e. tar and coal gas. The maximum amount of taronto the column at 25% C and then eluted with an acetonitrile- and gas are usually obtained over a temperature range from 450water mobile phase at a flow rate of 1.5 mL/min. a UV detector to 550C 118]. Therefore, below 600C both the inherent PAHsat a wavelength of 254 nm was used to detect the separated com- and those in the tars generated during the thermal decompositionponents. The 16 US Environmental Protection Agency priority pol- contribute to the yield of PAHs. The PAHs produced during the lowlutant PAHs were identified. The detailed analytical conditions are er temperature decomposition consist mainly of smaller specieslisted in table 2since the lower metamorphic degree of the tested lignite is associ-PAH identification was accomplished by comparing the reten- ated with a small degree of aromatic condensation and short alkytion times of peaks in the samples with those of PAH standards side chains. As the temperature increases two competitive reacrun under the same conditions. The quantitative analyses were car- tions begin to dominate. These are the decomposition of aromaticried out using calibration data from PAH standards which were compounds bopurchased from Dikma Company, USA. The chromatogram of the nation of free中國煤化工cture and the combes the higher weightPAH standard and the designation of each peak is shown in Fig. 2 aromatics areCNMH Gm smaller fragments.and Table 3, respectively.resulting in the increase in 2- ana 3-nngea PAHs observed aboveS. Liu et aL/Mining Science and Technology ( China) 21(2011)605-610607FlownetBlowdown1. A sketch of the pyrolysis and absorption train. (1)Gas cylinder(N2):(2) Tubular fumace:(3)Absorption bottle: (4)Thermometer: (5)Flask containingng tube containing XAD-2 resin:(7)Silica geL.HPLC conditions for PAH analysis.ConditionItemTime(min) A/water(‰)ColumnSUPELCOSILTM. LC-PAHGradient elution programColumn temperature 25"CDetectorUV/is5Acetonitrile-water1.5 mL/min45Liquid sample volume 10 ul600C. However, these fragments, which are highly reactive free average yield of the 5-ring PAHs is less than 1.00 mg/kg and thisradicals having a very short average lifetime, tend to form stable yield drops with the increase in heating rate. among the 6-ringPAHs. Therefore, the distribution of PAH species varies as the result paHs the yield of bghiP is 3.71 times that of inP.of a competition between decomposition and free radical combinaThe heating rate has both positive and negative effects on PAHtion. In addition, the increase in total PAH yield above 600C is also formation during coal seam pyrolysis. Higher rates shorten therelated to the higher mole ratio of H/C in the tested lignitetime to reach the final pyrolysis temperature Effects from thermo-decomposition of the coal structure are strengthened by this.3_2. Efect of heating rate on PAH formationThe breakdown of condensed aromatic and hydro-aromatic unitsconnected by alkyl bridges, and other functional groups in the coalHeating rate is one of the primary factors affecting PAH forma- is thereby enhanced, which promotes the formation of PAHs. Howtion during coal seam pyrolysis. the effect of heating rate on the ever, the increase in heating rate also enlarges the temperature dif-total PAH yield and the PaHs distribution by ring number is shown ference between the extemal and internal parts of the coal andin Fig. 5. The total PaH yield first decreases and then rises. the lowdelays heat and mass transfer This affects pyrolysis rate, whichest PAH yield is 62.87 mg/kg with a heating rate of 15C/min. The hinders the formation of PAHs. The results observed during thistypical slow heating rate expected in a coal seam of about 5 c/min investigation depend on a combination of these positive and negagives to moderate yield of PAHs. When the heating rate is tive effectsincreased from 15 to 40C min the total PAH yield increases byDuring coal seam pyrolysis the increase in heating rate accelenearly 2.23 times. Thus, higher heating rates seem to give higher ates the removal of free radicals and volatiles from the coal surfacetotal PAH yields. the distribution of PaHs by ring number indicates and inhibits secondary reactions such as combination of free radithat the major component consists of the 3-ring PAHs, which cals. This reduces the probability that high molecular weight PAHsaccount for 62.76-76.53% of the total PAH yield. Increasing the will form. Actual coal field fires occur by a percolation combustionheating rate causes the yield of 3-ring PAHs to show a similar trend process where heat is transferred from the large coal surface intoas the total yield in PAHs. the yield of other PAH components are the bulk of the coal seam. Under these conditions the heating rateless influenced by heating rate. The yield of 2-ring PAHs rises and pyrolysis rate are both slow. This in turn favors the recombinaslightly at faster heating rates Faster heating favors the formation tion of free radicals and leads to the formation of higher molecularof lower molecular weight PAHs. Changing the heating rate from weight PAHs, compared to the experimental conditions.15 to 40C/min causes the total yield of 4, 5,and 6-ring PAHsto drop from 19.82% to 8.96%The distribution of PAH species produced from coal seam pyro- mvlysis at different heating rates is shown in fig. 6. Note that NaP, 1000AcPy, AcP, and Pyr are the most abundant PAHs whatever the heat-ing rate. Also note that the sum of these four components accountsfor from 78. 48% to 88. 16% of the total PAH content. However. theindividual yields of these four species differ. Higher heating ratesfavor NaP formation. Formation of AcPy shows the opposite trend.Heating at 15C/min causes the yields of AcP and Pyr to be at their中國煤化工minimum values of 19.38 and 2.95 mg/kg, respectively. Chr is the4-ring compound with the smallest concentration and it has aCNMHGmaximum value of 4.30 mg/kg at the rate of 30C/min. TheFig 2 Chromatogram of PAH standard (100 g/mL)s Liu et al/ Mining Science and Technology(China)21 (2011)605-610Peak numberPAHSAbbreviation formulaStructural formulaChSFluorenePhenanthrenePhAc14H10AnthraceneAnTFluAChryseneC18H:2Benzo k) fluorantheneBenzo(a pyreneCnoH?Dibenzo(a, anthraceneIndeno( 1,23-cd)pyreneCpH100umg00℃2-1區700℃600℃s500℃∑PAHs400500600700800900FluA Pyr BaA Chr BbF BLF BaFig 3. Effect of temperature on total PAH yield, parametrized by number of ringsFlg. 4. Effect of temperature on the distribution of PAH species(coal particle size3.3. Efect of atmosphere on PAH formationThe effect of an air blast during underground pyrolysis was tested the 3-rings still dominate the product mixture under both atmo-by using two atmospheres for the laboratory pyrolysis. One con- are formed, 20.42% of the total, and the product has 3-and 4-ringtained nitrogen and the other was without nitrogen. The results PAHs that account for 70. 24% and 12. 84% of the total, respectivelyare shown in Fig. 7. It is clear that atmosphere has a dramatic effect Therefore, it中國煤化工 sis in the presence ofon PAHs formation. a nitrogen atmosphere is favorable for the nitrogen tends-The formation of theseCN Gof the precursor PAHsformation of PAHs and the yield of PAHs was 1.81 times higher in smaller PAHs Mace. which is shortened by the injection of nitro-the presence of nitrogen. The distribution of PAHs was such that in the tubularS Lu et aL/Mining Sence and Technology( Cina)21(2011)605-610z without N?0Heating rate(C/min)hEifect of heating rate on total PAH yield(particle size 2 am, N atmospherePAHs speciestemperature 600.C)P Effect of atmosphere on the distribution of PAH species(coal partide size2 cm, he240區40℃/min1.58 and 0.56 mg/ kg are obtained. These compounds cannot be de-30℃mintected during pyrolysis without nitrogen flows5℃/min5℃hin3. 4. Eject of particle size on PAH formation120The effect of particle size on the total PAH yield and distributionis illustrated in Fig 9. It is clear that increasing the size of the coalcaused the total Pah yield to decline from 204. 41(pulverized coal)to 120.25 mg/kg(2 cm sized particles). The yield of the main prodap AcPy AcP Flu PhA AnT FluA Pyr BaA Chr BbF BKF BaP DbABguct, 3-ring PAHs, changes in the same was as the total PAH yield InPAHs speciecontrast, the other PAHs show only a slight fluctuation in yield.Flg& Effect of heating rate on the distribution of PAH species (particle size 2 cm. Yields of 5- and 6-ring PAHs increased by 2.15 and 11.57 times,N2 atmosphere, final temperature 600.C).coal(2 cm). The yields of 2- and 4-ring PAHs is almost constant forevery size coaL.160The thermal conductivity of the coal is low. Increasing the coalN2 pyrolysis atmospheresize slows heat and mass transfer due to the limited specific sur-face areas. The temperature difference between the surface andWithout Nthe inside of the coal particles is greater for the larger particlesLower temperatures inside the coal particle are not favorable forthe decomposition of the molecular structure. This leads to adecrease in PAHs formation. On the other hand, larger sized coalshave a longer residence time for the initial decomposition products. This may increase the possibility of pyro-synthesis of aryl rad-icals and raise the yield of higher molecular weight PAHs. Inaddition, a long residence time is disfavors the removal of the PAHsofrom the pyrolysis area and, in turn, reduces the PAHs yiel3-ring 4-ring 5-ring 6-ring EPAHFig- 10 shows the distribution of PAHs as a function of particleEPA-PAHssize. Notice that particle size changes the yield of PAH speciesF-7. Effect of atmosphere on total PAHs yield (coal partide size 2 cm, heating rateand that Nap, AcP, AcPy, and Pyr are still the dominant species5Cmin, final temperature 600C)for every particle size. The yield of AcPy increases from 13.91 to17.93 mg/kg when the particle sized increases from smallest tolargest. The yield of AcP decreases from 142.46 to 55. 98 mg/gen. this is beneficial for the removal of PAHs and accelerates thformation reaction by decomposition On the other hand, a shortesidence time reduces the chance of condensation between aromaticradicals and this leads to a decline in the amount of high molecularweight PAHs. The nitrogen flow also speeds up heat and mass trans-fer and makes the pyrolysis more complete. Thus, the total PAHyield2-ringis raised under these conditions4-nngThe distribution of PAH species during pyrolysis in different5-ringatmospheres is shown in Fig. 8. Observe that NaP, AcPy, AcP, andPyr are the most abundant species and that the yields of these一∑PAHsspecies are distinctly affected by the pyrolysis atmosphere. theyields of NaP, AcP, and Pyr increase by 1.52, 246, and 1.62 times,respectively, when the pyrolysis atmosphere is enriched with中國煤化工甲cnitrogen. The concentration of AcPy shows a contrary trend andthe maximum yield2390 mg/kg, occurs without added nitrogen.匙ms微 CNMHGLikewise, in the nitrogen atmosphere DbA and BghiP yields of 600C heating ratS Liu et aL/Mining Science and Technology( China)21(2011)605-610(5)An increase in coal size reduces total PAH formation while區交交2 cm lump coalhe formation of 5-and 6-ring PAHs increases. the yield ofS I cm lump coalAcPy increases from 13.91 to 17.93 mg/kg when the coal sizeincreases. The amounts of AcP and Bap formed drop to thez Pulverized coalminimum values of 55.98 and 0. 27 mg/kg, respectivelyunder the same conditions120司Acknowledge°圖象一照一Financial support for this work provided by the National Natu-Nap AcPy AcP Flw PhA AnT HuA Pyr BaA Chr BbF BkF BaP DbABral Science Foundation of China(no. 50876112), the FundamentalPAHs speciesResearch Funds for the Central Universities(No. 2009QH13), andthe International Scientific and Technological CeFlg 10. Effect of coal size on the distribution of PAHs(N2 atmosphere, finaltemperature 600"C heating rate 5C/min).(No. 2010DFR60610)is gratefully acknowledgedReferenceunder the same circumstances. The yield of BaP, which contributesthe most to the toxicity equivalent(TEQ) value, drops to a mini- 111Y2Y, Zhang Z, Su YQ, Researchof polycyclic aromaticChem Technol 2005mum value of 0. 27 mg/kg when the particle size is 1 cm.TG, Wu DP, Wang J. A study of poActual coal fired fires have a wide range of conditions During cojing aerosols, J China Univ Mol2008:37(1):72-8〔inseam gasification pyrolysis occurs under a slow heating rate, a widehineserange of temperatures, and with insufficient air for complete com- 1 Gu dM, Liu ZH, L YY. Advances in studies of harmful substarheir impact on the environment. Adv Earth Sci 2001: 17(6): 840-7(in Chinese).n Northconditions due to the large specific surface areas and the slow flot[5] Liu SQ Chen S, ui JG, Yu L Deep coal seam underground gasification andapplication outlook. Coal Conv 2007: 30(3): 79-81( in Chrates. All these factors promote the pyro-synthesis of PAHs in the 16) Yang LH, Zhang X, Liu sQ Yu L Zhang WL Field test of large-scale hydrogenhigh temperature regions and the re-synthesis of PAHs in the lowng from underground coal gasification (UCG). Int J Hydrogertemperature areas. therefore, differing PAH emissions from coEncg2008:33:1275-85.fired equipment and underground coal gasification should be pa[7 Liu SQ, Wang YT. Yu L Oakey ]. Thermodynamic equilibrium study ofon during underground coal gasification. Fuel Processmore attentionTechnol2006;:87:209-15.[8] Liang HD, Yu CH, Zhou Q u YF TOF SMS study on PAHs in inrom a power station J China Univ Min Technol 2001: 11(2): 1 50-4(in4. Conclusions19] Shao LY, He TE, Li H, Shi ZB, u J. Characteristics of extractable organic matter( 1)The 3-ring PAHs AcP and AcPy are the dominant species ofin PM1o of urban area-case study of northwestern Beijing. J China UnivMinTechnol 2003: 32(4): 383-7(in Chinese).PAHs produced via coal seam pyrolysis under various condi- 110) Zhou HC. Jin BS, Zhong ZP, Xiao R. Hang Y]. Effect of air/coal ratio on PAHstions. also, 2-ring Nap and 4-ring Pyr are the main speciesthat need consideration(2)Increasing the pyrolysis temperature causes a minimum in [11) You XF, Li XD, Yan JH, Ning Mj. Cen KF PAHs emissions from fluidized bedds of plastics. Combust Sci Technolhe total PAH yield, and in the 3-ring PAHs yield, that occurs2003:9(4):376-80( in Chineseat a temperature of 600. Conversely, yields of 4-, 5,and [12 uXD, Yao Y, Yan JH XuX Chi Y, Cen KF Distribution of organic compounds in6-ring PAHs have no obvious trend and the maximum valuesare obtained over the temperature range of 500-600C The [13]u XD, Cao ZY.Q MF, You XF, Yan jH, Cen KF Influence of copper and cupricand has a maximum at 800C.2003:31(6):548-52( in Chinese)[14] Chen Js. Yuan DX Hong Yw. Guo ). Effect of catalytic De-NOx device on the(3)Generally, the formation of PAHs is accelerated by higheremission characteristics ofyclic aromatic hydrocarbon in flue gas, J Fuelheating rates. This is especially true of the lower molecularhem Technol 2007: 35(6): 722-6(in Chinese).weight PAHs. When the heating rate changes from 15 to 15 Ledesma EB, Kalish MA. Nelson PF, Wornat Mj. Mackie JC.Formation and fate40 C/min the total PAH yield increases by nearly 2.23 time01-14.The amount of product having more than 4-rings drops from [161 Mastral AM, Callen M, Murillo R Assessment of PAH emissions as a function of19.82% to 8.96% over this range. The typical heating rate in a (17)Mastral AM, Callen M. a review on polycyclicdrocarboncoal seam leads to the intermediate yields of PAHs.emissions from energy generation. Environ Sd Te0:3415):30(4)The existence of nitrogen favors PAH formation and the [18 Cheng Z Study on the emission characterobserved PAH yield was 1.81 times that seen withoutTechnology: 2010(in Chinesnitrogen.中國煤化工CNMHG