煤在合成气、氢气和氮气气氛下的热解研究

第35卷第1期燃料化学学报ol. 35 No. 12007年2Journal of Fuel Chemistry and TechnologyFeb. 20Article ID:0253-2409(2007)010001404Coal pyrolysis under synthesis gas, hydrogen and nitrogenARIUNAA A", LI Bao-Qing, LI Wen', PUREVSUREN B, MUNKHJARGAL Sh2LIU Fen-rong', BAI Zong-qing, WANG Gang(1. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of SciencesTaiyuan 030001, China; 2. Mongolian Academy of Sciences, Ulaanbaatar 210351, Mongolia)Abstract: Chinese Xundian, Mongolian Shiveeovoo lignites and Khoot oil shale are pyrolyzed under synthesis gas(SG)at temperature range from 400c to 800 C for lignite and from 300 C to 600 C for oil shale with heating rate of10 C/min in a fixed bed reactor. The results were compared with those obtained by pyrolysis under hydrogen and nitro-gen. The results showed that unlike pyrolysis at high pressure, there are only slight different in the yields of char and taramong pyrolyses under various gases at room pressure for lignite, while higher liquid yield with lower yields of char andgas was obtained in pyrolysis of oil shale under SG and H, than under N,. It is found that the pyrite S can be easily re-moved to partially convert to organic S under various gaseous atmosphere and the total sulfur removal for oil shale ismuch less than lignite, which might be related to its high ash content. The higher total sulfur removal and less organic Scontent in the presence of SG in comparison with those under N, and even under H, in pyrolysis of Xundian lignite miglresult from the action of CO in SG. However, co does not show its function in pyrolysis of Khoot oil shale, whichmight also be related to the high ash content. The results reported show the possibility of using synthesis gas instead ofpure hydrogen as the reactive gas for coal hydropyrolysisKey words: pyrolysis; synthesis gas; desulfurizationCLC number: TQ530 2 Document code: AChina and Mongolia are the countries of lack of pyrolysis under Sg was less studied especially for oiloil source with relative rich in coal resource. How to shale. For increasing coal utilization efficiencyconvert coal into oil is a major project in both coun- and mitigate the pollution, multi-generation processtries, which will affect the national safety and the e- has been proposed as the future clean coal technoloconomic sustainable developmentgy, which is mainly based on coal gasification withHydropyrolysis( HyPy) is a pyrolysis process synthesis gas production6. Thus, it might be possiunder hydrogen. Compared with pyrolysis under inert ble to pyrolyze coal under SG as the Ist step in thegas,the quantity and quality of tar are improved, and multi-generation technologylow sulfur char is produced in HyPy due to that theThe purpose of this work is to study the possibilithermally released free radicals can be stabilized by ty of using SG instead of pure hydrogen as the reaccapturing hydrogen to produce tar with low molecular tive gas for pyrolysis of coal and oil shale. The resultsweight compounds and that most sulfur in coal can be will be compared with those obtained in pyrolysis unremoved as gaseous H,S.Thus, HyPy provides a der H2 and N2. The desulfurization in pyrolysis underroute for the production of liquid from coals and ex- SG is also investigatedtensive studies on HyPy have been reported. Howev- 1 Experimentaler, because of the high cost of pure hydrogen, HyPy 1.1 Samples Mongolian Shiveeovoo ligniteis not a feasible process and coal pyrolysis using cheaKhoot oil shale andper hydrogen rich gases such as coke-oven gas ticle size from 60 to 80 mesh were used in this studCOG)and synthesis gas( SG)in stead of pure hy- Their characteristics includi wvere used in this studydrogen has been proposed. Pyrolysis under CoG mental analyses, the sulfur form and ash compositionas investigated more detail in our lab, however, are shown in Tables 1-3Table 1 Proximate and ultimate analysis of samplesProximate analysis wShiveeovoo10.8916.1034.1654.954.701.550.5120.220015.9246.4253.390.993.4083.11中国煤化工*-by differenceCNMHGReceived date: 2006-06-13: Received in revised form: 2006-09-08Corresponding author: LI Bao-Qing, propessor, maijor: coal science. E-mail: libq@ sxicc accn.Authorintroduction:AlexAriunaa,female,Pho.student,majoringincoalchemistry,E-mail:a-a_ariunaa@yahoo.com燃料化学学报35卷Table 2 Sulfur forms of samples(wa/%)Synthesis gas was produced by methanol decom-position and provided, by the Institute of Coal Chemis1.000.630.01try with the following composition( vol%): H264.82%;CO,31.60%;CH4,2.43%;CO2,Khoot oil shale 1.40 1.14 0.20 0.060.64%andN2,0.51%Table 3 Ash composition of the Khoot oil shale( w/%)K,OP,OMgO13.61.222.580.061.2 Pyrolysis Pyrolysis test was performed in a measured gravimetrically, and then the residue wasquartz tube reactor containing 5 g coal samples or 10g further extracted with HNO, to determine pyrolytic SMongolian Khoot oil shale samples at temperature The content of organic S was calculated by subtractionranging from 400 c to 800 C for coal and from of the inorganic S from the total S300℃to600℃ for oil shale with a heating rate of2 Results and discussion10 C/min and a flow rate of 150 mL/min under SG, 2.1 Pyrolysis under SG, H, and N2 Figure IH2 and N2 atmospheres at the atmosphere pressureThe liquid containing tar and water was collected in a show the product yields in pyrolysis of Mongoliancold trap. The gases were sampled regularly and ana- Shiveeovoo and Chinese Xundian lignites at differentzed by gC. After reaction the char was weighttemperature under H2, SG and n2. It seems that unand collected The sulfur removal(SR) was calculike pyrolysis at high pressure, there are only slighted according to the following equationdifferent in the yields of char and tar among pyrolysesunder various gases at atmosphere pressure for bothx100%Slignites, indicating that gaseous hydrogen shows itswhere,S, coal total sulfur in raw coal; S, char total notable hydrogenation ability only at high pressure.Itsulfur in char Y: yield of charis also found that water yield is higher for both ligThe Eschka analytical procedure was used to denites due to their high oxygen content. Comparedtermine the total sulfur in coal and chars. The sulfur with Shiveeovoo lignite, tar yield is higher for Xundi-forms in coal and char was analyzed according toignite, which should be related to its higher con15-82. Briefly, sulfate S was extracted with HCltent of volatile matter5050505050wtar under SG: Ogas under SG; tar under H2; ogas under H2 atar under N2:*gas under,1 kFigure 1 Product yields in pyrolysis of Shiveeovoo( left)and Xundian( right) lignites under SG, H, and■ char under sg; water under SG;· char under h2; Water under H2;▲ char under N2;★ water under N2Product yields in pyrolysis of Khoot oil shale un- tained in pyrolysis under SG and H, than under Nder H, SG and N, at 600C is shown in Table 4. Table 1 indicates that the molecular ratio of H/C inDue to high ash content in Khoot oil shale, the a-中国煤化工, while only aboutmount of liquid after pyrolysis was not enough to sep- 1.0arate the water and tar. In comparison with lignite aliphaCNMH Gale mainly containsthermally decom-from Figure 1, marked difference in product yield is posed to form free radicals and then be hydrogenatedfound in pyrolysis under various gases, i. e., higher easily by gaseous hydrogen at even normal pressureliquid yield with lower yields of char and gas was ob- The conversion of oil shale during pyrolysis is much期A. Ariunaa et al.: Coal pyrolysis under synthesis gas, hydrogen and nitrogenhigher than that of lignite as shown in Figure 2. It is less content of organic S in lignite char obtained byalso found that there is no significant difference be- pyrolysis under SG in comparison with those under H2tween the product yields in both pyrolyses under SG and N2 may also prove the action of CO in SG. How-and H2, implying that SG can replace H2 in pyrolysis ever, Co does not show its function in pyrolysis ofof oil shale and ligniteKhoot oil shale, which may also be resulted from theTable 4 Product yields in pyrolysis of Khoothigh ash content, especially its high content of Caooil shale under Ha, SG and N, at 600Cas shown in Table 3. It was reported that the additionProduct distribution w /%oof Cao had remarkable effect on reducing H,s andAtmosphereCOS throughout the whole pyrolysis temperature [9)The minerals in coal may catalyze the decomposition25.66.5or inhibit the formation of cos 10, 11J15.29080503020300350400450500550600650700750800850550600650700750800850Temperature 1/℃Figure 3 Desulfurization of total sulfurFigure 2 Comparision of conversion in pyrolysisin pyrolysis of Shoot oil shale andXundian lignite under SG, H, and N,■ Khoot in SG;● Khoo in I2;▲ Khoot in N2■ Khoot in SG;● Khoo in H2;XUndian in SG;. Xundian in H2;