采用TG-FTIR聯(lián)用研究煙煤熱解及熱解動(dòng)力學(xué)參數的確定

第10卷第27期2010年9月科學(xué)技術(shù)與工程Vol 10 No 27 Sep. 20101671-1815(2010)27-664207Science Technology and Engineering⊙2010 Sci. Tech. Engng動(dòng)力技術(shù)采用TG-FTIR聯(lián)用硏究煙煤熱解及熱解動(dòng)力學(xué)參數的確定劉栗邱朋華吳少華張紀鋒秦裕琨(哈爾濱工業(yè)大學(xué)燃燒工程研究所,哈爾濱10001)摘要研究煤熱解時(shí)的組分析出規律對進(jìn)一步研究低NO燃燒或煤粉再燃時(shí)的均相NO,還原反應來(lái)說(shuō)都是非常重要的。釆用TG-FTIR實(shí)驗裝置對兩種中國煙煤在不同升溫速率(10,20,50和80℃/min)下的失重及氣體釋放規律進(jìn)行了研究,并將實(shí)驗數據與 FG-DVC軟件的模擬結果進(jìn)行了對比。通過(guò)對比發(fā)現,其中一種煙煤的模擬結果與實(shí)驗數據比較相符,但另一種煙煤的模擬結果與實(shí)驗數據偏差較大。偏差主要是由于FG-DVC模型中提供的有關(guān)動(dòng)力學(xué)參數不準確所導致?；?FG-DVC模型的假設,官能團熱解形成的輕氣體產(chǎn)物的釋放過(guò)程可以用一系列平行獨立的單方程模型描述,應用FTR的實(shí)驗結果對熱解氣體組分的動(dòng)力學(xué)參數進(jìn)行了修正。采用修正后的動(dòng)力學(xué)參數, FG-DVC能更準確的模擬該煤的熱解過(guò)程。關(guān)鍵詞煤熱解 TG-FTIR動(dòng)力學(xué)參數 FG-DVC中圖法分類(lèi)號TK16文獻標志碼AThe evolution of volatile species during pyrolysis and char. The DVC model is employed to deas a significant effect on coal combustion and forma- the amount and molecular weight of macromoleculartion and reduction of pollutant emissions". 2. Since fragments. The lightest of these fragments evolve as1970, some kinetic models such as single equation tar. Nine well-characterized coals were selected to formmodel, two-equation model, and Solomons general an FG-DVC data base. The minimum input to the FG.model etc have been presented in order to simulate the DVC model provided by the user is the ultimate analypyrolysis more reasonably. Solomonresearched the sis of coal on dry ash free basis. If the H/C and o/Cslow pyrolysis process for several American coals, ob- atomic ratios for the interested coal fall into the grid oftained some kinetic parameters for gas evolution param- FG-DVC coal data base a pre-processor subroutine willeters for gas evolution and developed a general model generate the FG-DVC needed input files for the interest-alled FG-DVC to simulate the pyrolysis process. This ed coal. Although the parameters used in FG-DVC codemodel takes account of the evolution of gases, tar, char were determined by slow pynand adsorbed molecular in detail. The FG-DvC model al have comparedeasured data with the FG-DvCcombines two models, one is the Functional Group model predictions anFG)model and the other one is the Depolymeriza- simulate the process of rapid pyrolysis under the condition, Vaporization, Cross-linking(DVC)model. The tion of American coal. 5. Because of the difference beFG model is used to simulate the gas evolution and the tween the American coals and the Chinese coals, the kielemental and functional group compositions of the tar netic parameters for many Chinese coals usualcan tbe derived directly from the interpolation scheme based2010年6月21日收到,7月1日修改國家基金研究計劃 on the data base. Instead, the kinetic parameters of the00c0203)和國家自然科學(xué)基金(50706011)資助most closed coal to the Chinese coal in the27期劉栗,等:采用 TG-FTIR聯(lián)用研究煙煤熱解及熱解動(dòng)力學(xué)參數的確定6643diagram ( a plot of H/C versus O/C atomic ratios)were CO,/, with known concentration was mixed with N2Ised to simulate and error will be observed. However, and then entered into the gas cell. The species con-quantitatively analysis of centration in the gas cenged by chathe gas evolution for domestic coals using TG-FTIR!.. mixing ratio( gas mixture to N,). A method was thenThe aim of this work is to quantitatively analyze the py- established through polynomial fitting the known con-rolysis process for two Chinese coals and to determine centrationthe kinetic parameters related to the main species for thecoal which cant be simulate reasonably by FG-Dvc 2 Kinetic Modelthe Fg-DⅤ C model,th1 Experimentalof each species is assumed to be independent fromthe other species and the evolution rate can be repre-1.1 Coal samplessented by a first-order rate with a Gaussian distribuTwo bituminotals. Zhtion of activation energies(8. The assumed first-orcoal, were dryinged at 50 C for(4-5)h and then der reaction rate for release of the ith functionalgrinding with camelia mortar before experiment. The(Xrecursor pool in the FGcoal analysis of samples was shown in table 1DvC input files ) can be expressed as followingTab. 1 The proximate and ultimate analysis of coal samples equation shown:Proximate analysis /wt%Ultimate analysis/wt%d i-k xZhunger coal 2. 75 21847.1577.415.0415.501.500.55And the rate constant k, in eq. (1)is given by anShenhua coal5.7110.5327,7556.0180.644.8512.501430.58rrhenius expression with a Gaussian distribution of1.2 TG-FTIR experimentk1=A,exp(-E1±)/RT)The pyrolysis of coal was performed at a thermo-Where A; is the pre-exponential factor, E, is thegravimetric analyzer(TGA/SDTA851)coupling with average active energy, a, is the width of the GaussianFTIR( Nicolet 5 700). The pyrolysis conditions were distribution and R is the gas constant. A non-isother-as follows coal sample weight, 50 mg: gas atmos- mal method is used to obtain the kinetic parame-phere,N2:pressure,0.1 MPa; total gas flow ters[9-13). As the coal sample is heated at a constantthrough the furnace, 150 mL/ min. After purging, the heating rate Hsample was heated from room temperature to 105 C(at 10 C/min)for 20 min to dry it and then to 900℃for20min(at10℃/min,20℃/min,50℃/ then the eq.(1) can be transformed to:min and 80t/min respectively ). At the same timekXthe volatile species were introduced to FTIR for qualitemperaturequantitative analysis, the gas cell must be calibrated species evolution reaches a maximum, the temperaturefor interested gas species. a gas mixture of CH,co/ derivative of evolution rate should equal to zero, i.e644科學(xué)技術(shù)與工程10卷dXdt≈0,atT=FG-DVCi 10.00一-DTGEq (5)canten to the following form by003substituting eq.( 1)and eq (2)into eq (5):EE0 at T=T(6)The equality holds if and only if the term in theZhunger coal at 50 C/minsquare brackets equals to zero, i.e.001()-(8月10(7)-FG-DVCIt can be found from eq.(7)that theliner variation witT-. After the evolution rates for-0.06007each species at different heating rates are measured00800100through experiment, the kinetic parameters then can beTemperature/Cdetermined from the slope and the intercept in eqFig. 2 TG/DTG und simulated weight loss curves of(7). After A, and E; are determined, o and Y, can beShenhua coal at 50C/minfitted to experimental data using a trial-and-error ap.Tab. 2 The characteristic parameters of coal samplesT/(℃)W。/(w%)W。/(w%)3 Results and Discussion-6.7632.6232.54Shenhua-31.13. 1 Thermogravimetrie characteristicThe TG/DTG curves and simulated weight loss byShenhua coal had higher R and lower T.ThisDVC code of Zhunger coal and Shenhua coal dur- meant that the active energy for Shenhua coal was smallpyrolysis were presented in figure I and figure 2. and the weak aliphatic chains were more than ZhungerThe weight loss was increased as temperature goes The final weight loss calculated by FG-DVC (WL)up. After pyrolysis finished, Zhunger coal had higher also contained in table 2. From figurel, figure 2 andWL than Shenhua coal as shown in table 2. This may table 2, it was found that the calculation error forbe caused by higher Vd in Zhunger coal. Meanwhile, Zhunger coal was very small, but the difference befrom the DtG curves, the R and T could between TG curve and FG-DVC curve for Shenhua wasown in table 2obvious and the error was around 10%. The coordi-nates of the two coals in the van Krevelen diagram wereshown in fiIt can be seen from the figure 3 that27期劉栗,等:采用T-FTR聯(lián)用研究煙煤熱解及熱解動(dòng)力學(xué)參數的確定6645the Zhunger coal coordinates in the van Krevelen dia- with higher heating rates. This was caused by the moregram fall into the grid of library-coal data, while the difference between coal sample and thermocouple withShenhua coal coordinates are far from the grid. So the higher heating rate. The width of temperature related toFG-DVC input files for the Zhunger coal can be gener- CO, evolution also became bigger with the heating rateated by means of an interpolation scheme which is increased. This was caused by deeper overlapping de-based on the three surrounding coals database. And gree with higher heating ratethe input files for Shenhua coal are generated based onThe evolution curves of CH, at different heatingthe library coal most closely located in the van Krey- rate were shown in figure 5. Formation of CH, startedelen diagram. As the parameters in the input files are at about 340C and reached the maximum evolution atnot accuracy, the calculation error for Shenhua coal about525℃,556℃and577℃for20℃/minwas bigger. The following section will focus on the evo- C/min and 80 C/min respectively. The formation oflution of gases for Shenhua coal in order to modify the CH, finished at the end of the liner heating step and nokinetic parameters in the input files and improve the obvious formation of CH, was found during temperaturesimulation results eventuallyLow-Rank002050℃min00150.80coals000000Temperature℃C0.150200Fig. 4 Evolution rate curves of CO, during pyrolysis forFig 3 The van Krevelen diagram for two bituminiousShenhua coal sample at different heating ratescoals and the library coals of the FG-DVC code00153.2 Evolution characteristic of gases10C/min20℃minThe variation of gas evolution with temperature atdifferent heating rates could be seen from figure 4 to80°minfigure 6. For 10 C/min, evolution of CO, started at a0.005bout 180C. and reached the first maximum at about457C and then reached the second maximum around0000716C. The first peak appeared due to the decomposi200400tion of carboxyl functional group. The second peak athigher temperature was caused by more stable functiongroup such as ether. It was also found that the secondFig. 5 Evolution rate curves of CH, during pyrolysis forpeak was more important than the first peak exceptShenhua coal sample at different heating rates80/min curve. The Tma for both peaks at differentheating rate were shown in table 3. The Tma, was higher科學(xué)技術(shù)與工程10卷in the input for-0035mat of the FG-DVC model. Y, is the initial fraction of a10℃/minparticular function group with the modified kinetic pa0520℃/min-50℃minin the input files, the weight loss and0020學(xué)80℃/minyield of gases during pyrolysis were recalculated at 800015gases0000Precursor pool A/s -x10(Eo/R )K(o/R)/K2004003080010001-CO,-loo1323020000.0777903-CO2- tight0.122295200.530000Fig. 6 Evolution rate curves of Co during pyrolysis for0.811687818000.025215Shenhua coal sample at different heating rates13-C0-looe0.0251811710000.002989holding step. As shown in table 3, the T-a also shifted10-C0- tight0.101938830000.031924to higher value for higher heating rate. The CH, wasmainly formed by the reaction in which the methylOriginal FG-DVCModified-FG-DvCchain and aliphatic bridges of a larger molecule werebroThe evolution curves of Co during pyrolysis wereshown in figure 6. Evolution of Co started at about280C. For 20C/min, evolution curves reached thefirst peak at about 626.C and then decreased a littleCo also had two shoulder peaks. The second and max2004001000imum peak was around 727C. The Co was releasedform the ether 0 group in the original coal. As shownFig. 7 Comparison of modified FG-DVC simulation onin table 3, the Tm also shifted to higher value foreight loss with experimental result and original FG-DvCsimulation on weight loss at 80 C/minhigher heating rate.Tab. 3 The Tu for gas at different heating ratesOriginal FG-DVC20℃/m50℃/min80℃/minModified FG-DVC456.68℃488.00℃510.94℃71606℃,757.90℃773.76℃525.49℃556.06℃576.64℃26.06℃663.71℃686.15℃726.64℃771.36℃795.66℃Weight loss CO3. 3 Modified FG-DVC ModelFig. 8 Comparison of modified FG-DVC simulation withThe kinetic parameters for gas, as shown in tableperimental result and original FG-DvC simulation at 80C/min4, were determined by employed the value in table 3 to27期劉粟,等采用 TG-FTIR聯(lián)用研究煙煤熱解及熱解動(dòng)力學(xué)參數的確定As shown in figure 7 and figure 8, the simulationReferenceshad a great improvement. Especially, the simulationyield of CO2 and CO fitted the experimental data very I Qiu P H, Wu H, Sun SZ,e al. Industrial test on coal re-buming atwell. It also can be found the simulated weight loss600 MW utility boiler and No, reduction. Korean Joumal of ChemicalEngineering,2007;24(4):683-687was still a little more was still a little more TG resultsIt was because that the kinetic parameters were deter. L zQ, JingJP, Chen Z C, et al. Combustion characteristics and NOxemissions o two kinds of swir bumer in a 300-MWe wall-fired pul-mined only for CO,, CH, and CO and the kinetic paverized-coal utility boiler. Combustion Science and Technologyrameters for other species such as Tar, H, and H, 0 2008: 180(7):1370-135were not available. This may be improved in later 3 Solomon P R, Hamblen D G, Carangelo R M, et al. General model fcoal devolatilization. Energy Fuels, 1988; 2(4): 405-422work4 Dutton K. Functional-group, depolymerization, vaporization, cross linkingmodAdvaneedFuelReseachIne.http://www.afrine.com4 Conclusions5 Li Xiaoli, Sun Rui, Zhang Xiao-hui, et al. Simulation study on NO.The pyrolysis experiment and numerical simulatioreduction by volatiles from coal devolatiliation. Proceedings of thcSEE,200828(11):3035( in Chinese)of two types of Chinese bituminous coal at different6 Yang Jingbiao, Cai Ningheng. A TG-FTIR study on catalytic pyroly.heating rates were performed using TG-FTIR analysis sis of coal. Joumal of Fuel Chemistry and Technology, 2006: 34(6)and FG-DⅤ C modelely. The weight loss and650-654( in Chinese)the evolution rate of CH, CO and CO, during pyrolysis 7 Zhou Junhu, Ping Chuanjuan, Yang Weijuan, et al. Experimentwere meeasured. The thermogravimetric characteristicJoumal of Fuel Chemistryand Technology, 2004, 32(6): 658-662(ingases were obtainedfrom the experiment data.8 Solomon P R. Hamblen D G. Serio M A. e a. A characterizationnergy and method and model for predicting coal comversion behaviour.Fuelmore weak aliphatic chains than Zhunger coal1993,72(4):469-488(2)CO2 and Co had two shoulder peaks during9 de Jong W, Pirone A, Wojtowicz M A. Pyrolysis of Miscanthus Gigan-evolution process while CH, had only one peak aroundsod pellets: TG-FTR analysis and reaction kinetics, Fuel550C.The T shifted to higher value for higher heat- 10 de Jong W, Di N G, Venneker B C H, et al. TG-FTIR pyrolysis oing rate. The width of temperature related to gas evolucoal and secondary biomass fuels: Determination of pyrolysis kinetiction also became bigger with higher heating rate.parameten for main species and NOr precursors, Fuel, 2007: 863)FG-DVC model can simulate the pyrolysis(15):2367-237611 Braun R L, Bumham A K. Analysis of chemical reaction kinetics u-very well forfor Zhunger coal, but the difference between experimental data and FG-DVC curve for Shen&Fuel,1987;1(2):153-161hua was obvious12 Solomon P R, Serio M A, Carangelo R M, et al. Analysis of the Ar(4)The kinetic parameters for CH,, Co and Co2 gonne premium coal samples by thermogravimetric Fourier transformwere obtained from experiment data. The FG-DVCinfrared spectroscopy. Energy Fuels, 1990: 4 (3): 319-333model was modified with the calculated kinetic parame13 Wang Hui, Jiang Xiumin, Yuan Dequan, ef a. Pyrolysis o coalwater shurry volatile matter by using FG-DvC mod model. theChemical Industry and Engineering, 2006: 57(10): 2428--2432(innumerical simulation fitted the experimental resultsmore reasonably for Shenhua coal(下轉第6652頁(yè))6652科學(xué)技術(shù)與工程10卷3 Kazimiercpk M K. Transfer function of current modulator in PWM4阮新波嚴仰光直液開(kāi)關(guān)電源的軟開(kāi)關(guān)技術(shù).北京:科學(xué)出版社,200mental Theory and Applications, IEEE Transactions on, Volume:475譚陽(yáng)紅蔣文科何怡剛基于 OrCAD10.5的電子電路分析與設lsue:9,Sept,2000:1407-1412計北京國防工業(yè)出版社,20The Simulation Research of Buck-Boost ConverterLI XueIiWeifang Oil Transportation Station, Pipeline Storage and Transportation Corporation, SINOPEC, Binzhou 256600, P. R. China)Abstract] PSpice is a powerful simulation software, simulation results are very close to the true state of the circuit.The overall working stages of Buck-Boost converter is simulated and analyzed by PSpice. The working processof the Buck-Boost circuit includes the transient process of start-up circuit and the steady working process. All thestages of stored energy elements of Buck-Boost converter are also introduced. The large number of visual simulationwaveforms are given. Thus the understanding of Buck-Boost converter is deepenedKey words Buck-Boost converter Pspice transient analysis steady-state(上接第647頁(yè)Experiment Research on Bituminous Coal Pyrolysis byTG-FTIR and Determination of Pyrolysis Kinetic ParametersLIU Li, QIU Peng-hua, WU Shao-hua, ZHANG Ji-feng, QIN Yu-kunCombustion Engineering Research Institute, Harbin Institute of Technology, Harbin 150001, P. R. China)Abstract] It is significant to study the components and the relevant concentration of volatile matters released dur-ing pulverized coal pyrolysis, which is fundamental for the further study of low NO, combustion and NO, reductionduring coal reburning process. The devolatilisation experiments of two types of Chinese bituminous coal were per-formed using TG-FTIR(Thermogravimetry combined with Fourier Transform Infrared Spectroscopy )analysis. Fourheating rates(10, 20, 50 and 80C/min)were adopted to research the weight loss and gases evolution. The numeri-cal simulations were performed by using FG-DVC(Functional Group and Depolymerization, Vaporization, Cross-link-ing)model on the experimental coals. It was indicated that the simulation results were well fitted for one of the two typesof coal but not very well for another. The emor was caused by the inaccuracy of the kinetic parameters of the main spe-cies provided by FG-DVC model. The kinetic parameters are then corrected by introducing FTIR results to a series offirst-order formulation by assuming that the light gases evolution are parallel and independent in FG-DVC model. Byadopting the comected kinetic parameters the simulation results are agreed with experiments data much betterI Key words] coal pyrolysis TG-FTIR kinetic parameters FG-DVC