第24卷第4期煤炭轉(zhuǎn)化Vol.24 No.42001年10月COAL CONV ERSIONOct.2001煤炭氣化氣流床氣化爐的數(shù)學(xué)模擬步學(xué)朋)彭萬旺’ 徐 振剛2)商要簡(jiǎn)要介紹了煤炭氣流床氣化的原理,總結(jié)了到目前為止煤炭氣化氣流床氣化爐數(shù)學(xué)模擬情況，包括簡(jiǎn)單平衡模型和動(dòng)力學(xué)模型(一維或多維),給出了這些數(shù)學(xué)模型模擬的主要內(nèi)容(對(duì)氣化過程流體力學(xué)、熱力學(xué)、化學(xué)反應(yīng)和質(zhì)量、能量及動(dòng)量平衡考慮情況)和模型的主要結(jié)論，以及典型氣流床氣化爐的模擬煤氣組成和煤炭轉(zhuǎn)化率數(shù)值與實(shí)驗(yàn)值或?qū)嶋H操作值的比較情況,結(jié)果顯示主要組分模擬誤差較小.關(guān)鍵詞煤炭氣化,氣流床氣化， 數(shù)學(xué)模擬中圖分類號(hào)TQ529造,而我國(guó)第一座IGCC示范電廠也已立項(xiàng),其氣化0引言島也將采用氣流床氣化工藝.因此應(yīng)重視對(duì)氣流床氣化工藝的研究及開發(fā)工作.煤炭氣化是煤潔凈利用的關(guān)鍵技術(shù)之一,它以對(duì)氣化爐氣化過程數(shù)學(xué)模擬的研究不僅有利于提高碳轉(zhuǎn)化率、冷煤氣效率,降低氣化過程的氧耗及深入了解氣化過程規(guī)律,而且可以用于指導(dǎo)氣化爐煤耗為目標(biāo),并向加壓及液態(tài)排渣、大型化等方向發(fā)設(shè)計(jì)及生產(chǎn)過程優(yōu)化控制.對(duì)氣流床氣化爐的數(shù)學(xué)展,從而達(dá)到改善環(huán)境及降低產(chǎn)品成本的目的.加壓模擬主要始于20世紀(jì)70年代，國(guó)內(nèi)外對(duì)此進(jìn)行了氣流床氣化技術(shù)是國(guó)內(nèi)外優(yōu)先發(fā)展方向之,氣流床大量研究,取得了許多成果.氣化技術(shù)有如下特點(diǎn):①能夠氣化任何變質(zhì)程度的煤及煤的加氫殘?jiān)?、石油焦?②氣化強(qiáng)度很高，碳1氣流床氣化原理轉(zhuǎn)化率高;③產(chǎn)品煤氣中不含焦油和酚類物質(zhì),環(huán)境友好;④其缺點(diǎn)是氧耗高、需設(shè)置磨粉、顯熱回收1.1 氣流床氣化過程描述及除塵等較龐大的輔助裝置.已工業(yè)化或正在示范從氣流床氣化工藝分析看.煤粉(或水煤漿)與的加壓氣流床氣化技術(shù)包括濕法加料的Texaco,氣化劑(O2/H2O)經(jīng)噴嘴噴入氣化爐的燃燒區(qū),由于Destec和干法加料的Shell, Prenflo 及GSP等,并氣化爐該處溫度高達(dá)1 500 C~2 000 C,因此煤粉在世界范圍內(nèi)得到廣泛應(yīng)用.受熱升溫速度很快(>10+C/s),可認(rèn)為煤粉中的我國(guó)20世紀(jì)70年代先后進(jìn)行過熔渣爐氣化及.殘余水分快速(瞬間)蒸發(fā),同時(shí)由于熱分解反應(yīng)速K-T氣化研究,也建立過工業(yè)化裝置,后因耐火材度大大高于煤粉的燃燒及氣化反應(yīng)速度,所以細(xì)小料等問題而停止.20世紀(jì)80年代后在魯南化肥廠、的煤粉顆粒開始發(fā)生快速熱分解，即脫揮發(fā)分,生成上海焦化有限公司、渭河化肥廠、淮南化肥廠等引進(jìn)半 焦和氣體產(chǎn)物.在富含氧氣及高溫條件下,揮發(fā)分.了Texaco氣化爐用于生產(chǎn)合成氨及甲醇,通過多 中的活性可燃成分如CO,H2,CH,及焦油與O2發(fā)年的實(shí)踐積累了豐富的經(jīng)驗(yàn),已達(dá)到了長(zhǎng)周期、高負(fù)生氣相燃燒反應(yīng),生成CO2和H2O.并放出大量熱荷、安全和穩(wěn)定運(yùn)行的要求,且在噴嘴、耐火磚及水量 供煤粉繼續(xù)熱解及氣化反應(yīng)的進(jìn)行.由于氣相燃煤漿泵等設(shè)備國(guó)產(chǎn)化方面取得了突破性進(jìn)展.目前，燒反應(yīng)速度很快，因此-般認(rèn)為在氧氣存在的情況利用干法加料的Shell氣化工藝正用于某化肥廠改下,上述氣相燃燒反應(yīng)達(dá)到完全,亦即在氧氣存在8煤炭轉(zhuǎn)化2001年時(shí),氣相中不含CO,H,CH,及焦油.煤中的揮發(fā)分反應(yīng)平衡時(shí)的煤氣組成及平衡溫度.項(xiàng)友謙[]用能析出后,發(fā)生半焦燃燒及氣化反應(yīng),與水蒸氣及CO2量最小原理,建立了加壓氣化平衡模型,并用4種方反應(yīng).如此時(shí)仍有氧氣存在，則在氣相中仍發(fā)生CO法對(duì)微分方程求解.模擬結(jié)果顯示平衡模型對(duì)氣流和H2燃燒反應(yīng).氣化爐中的氧氣反應(yīng)完后,半焦與床的模擬效果要好于固定床. Watkinson[1°]提出平水蒸氣、CO2和H2等繼續(xù)發(fā)生氣化反應(yīng),同時(shí)氣相衡模型,通過質(zhì)量和能量平衡及反應(yīng)平衡方程式關(guān)中還有水煤氣變換反應(yīng)和甲烷裂解反應(yīng)等.對(duì)氣流聯(lián),可以得到產(chǎn)品煤氣組成、產(chǎn)率和最佳適宜溫度，床氣化,一般將變換反應(yīng)和甲烷化反應(yīng)視為平衡反并對(duì)9種氣化爐型的工業(yè)化和半工業(yè)化氣化數(shù)據(jù)進(jìn)行了比較.對(duì)產(chǎn)品煤氣中的CO和H2含量誤差在土從如上分析可以認(rèn)為在對(duì)氣流床模擬時(shí),考慮0.1%之內(nèi),H2S和COS濃度可以準(zhǔn)確的預(yù)測(cè)，但氣化爐中氣固相的組成分別為氣相:O,H2O,CO,，CO2預(yù)測(cè)值的準(zhǔn)確性要差一些.結(jié)果還表明該模型CO, H2,CH,N2(或NHs)，H2S(+ COS), Tar;固對(duì)氣流床氣化爐模擬效果最好,流化床次之，而固定相:C,H,O,N, s, Ash, Moisture.另外考慮氣固相床由于一些不確定因素如揮發(fā)分含量組成等的存溫度Tg, T..數(shù)學(xué)模擬的目的就是求出氣化爐內(nèi)每在,模擬誤差較大.Ruprecht等DI建立了平衡模型,并用于評(píng)價(jià)試驗(yàn)數(shù)據(jù)分析.平衡模型可用于對(duì)出口-質(zhì)點(diǎn)處的上述參數(shù)的值.組成及溫度進(jìn)行簡(jiǎn)單預(yù)測(cè).由于其假定的條件較理1.2 氣化反應(yīng)動(dòng)力學(xué)想，如假定所有反應(yīng)都達(dá)到平衡,在實(shí)際過程是不可煤粉熱解反應(yīng)速度很快,主要根據(jù)經(jīng)驗(yàn)式對(duì)熱能的，因此其用途受到-定限制,對(duì)過程控制及氣化解速度和產(chǎn)物進(jìn)行估算,大致有Wen等[1+4給出的爐設(shè)計(jì)參考價(jià)值較少.幾種表達(dá)形式.氣固非均相反應(yīng),由于氣化爐內(nèi)反應(yīng)2.2考慮氣化過程動(dòng)力學(xué)的模型溫度很高，最高溫度可達(dá)2000 C以上,所以半焦與為了更準(zhǔn)確的用數(shù)學(xué)模型對(duì)氣化及燃燒過程進(jìn)O2,H2O,COz的反應(yīng)速度由氣膜擴(kuò)散及灰層擴(kuò)散控行模擬，需考慮氣化過程三傳一反及動(dòng)力學(xué)行為.許制,而半焦與H2的反應(yīng)較慢,它由化學(xué)反應(yīng)控制.多研究者對(duì)此進(jìn)行了研究,建立了一維、二維及多維從非均相反應(yīng)動(dòng)力學(xué)模型看,分為未反應(yīng)核收縮模模型. Field等對(duì)1967年以前的工作進(jìn)行了歸納,模型及灰層剝離模型,文獻(xiàn)[5]認(rèn)為灰層在反應(yīng)過程中型屬活塞流. Ubhayakar等$忽略了表面反應(yīng),但考剝離,因此反應(yīng)受氣膜擴(kuò)散和化學(xué)反應(yīng)動(dòng)力學(xué)控制;慮了軸向混合、揮發(fā)分的氣相反應(yīng)及熱解反應(yīng).而文獻(xiàn)[1,6]認(rèn)為,由于氣流床氣化爐中煤粉顆粒所Smith等[8,123 先后建立了一維及二維煤粉氣流床燃占體積很小(<1%),且停留時(shí)間只有2 s~3 s,因燒及氣化模型,模型中考慮了煤粉顆粒大小分布對(duì)此煤粉顆粒碰撞幾率較小，在煤粉顆粒表面因反應(yīng)反應(yīng)速度的影響. Wen等[給出一維模型來描述形成的灰層可認(rèn)為仍保留而不剝離,所以反應(yīng)速度Texaco氣化爐中的混合情況,每-微元被處理成氣可由未反應(yīng)核收縮模型得到反應(yīng)速度.其它學(xué)者也相是完全混合,固相以活塞流通過整個(gè)反應(yīng)器,固相研究了氣化反應(yīng)動(dòng)力學(xué)問題,基本一致的觀點(diǎn)是要粒子的速度用Stokes方程近似描述.模擬了中試裝同時(shí)考慮化學(xué)反應(yīng)控制及擴(kuò)散控制.使用比較多的置使用煤及加氫殘?jiān)鼩饣闆r,操作參數(shù)的變化對(duì)如對(duì)加氫氣化過程模擬時(shí),采用了Johnosn]的加煤氣組成的影響等. Govind等明對(duì)上述模型進(jìn)行了氫熱解動(dòng)力學(xué)模型;Wen等[1]3提出的未反應(yīng)核收縮修正,加入了動(dòng)量平衡.考查了煤氣組成與進(jìn)料速模型也使用較多，Smith等0]也采用了獨(dú)特的動(dòng)力度、氧/煤比及汽/煤比的關(guān)系. Sprouse等13.14] 模擬學(xué)表達(dá)式.加氫氣化反應(yīng),前者使用了經(jīng)驗(yàn)關(guān)聯(lián)式,但不適合次煙煤,后者盡管較通用和完善,但因其復(fù)雜性導(dǎo)致其2氣流床氣化數(shù)學(xué)模型綜述應(yīng)用困難.Brown等0研究了4種煤沿氣化爐的軸向及徑向氣相組成分布,討論了氧碳比及蒸汽量等對(duì)模擬結(jié)果的影響. Vamvukal[5]建立了一維穩(wěn)態(tài)模2.1平 衡模型型,發(fā)現(xiàn)氣固相最大溫度位于氧氣耗盡處,考察了關(guān)第4期步學(xué)朋等煤炭氣化氣流床氣化爐的數(shù)學(xué)模擬數(shù)學(xué)模擬的攻關(guān)課題,取得了豐碩成果.現(xiàn)將最近的任何模型模擬的目的是能反映氣化爐內(nèi)物料運(yùn)研究成果及文獻(xiàn)[6,12]對(duì)以前的煤粉氣流床氣化及動(dòng)及化學(xué)反應(yīng)情況,并獲得出口處煤氣組成及溫度、燃燒模擬情況的總結(jié)一并列于表1中.碳轉(zhuǎn)化率、氣化效率等參數(shù).氣流床氣化爐數(shù)學(xué)模擬與實(shí)際(或?qū)嶒?yàn))結(jié)果的對(duì)比情況見表2,可見對(duì)幾.3模擬煤氣組成與實(shí)際(或?qū)嶒?yàn))結(jié)果種不同爐型煤氣中的主要組分,模擬誤差小，說明模擬基本上是成功的.對(duì)比表1氣流床 氣化數(shù)學(xué)模擬匯總Table 1 Reviews of models for coal entrained-bed gasifiersAuther(s)ReferencesYearMain Contents/DescriptionMajor ResultsMehta1976Phenomenological model combination of plug flow Describes the outlet conditions for aand perfectly-stirred calculations, gas phase chemi- three -stage entrained flow gasifier.cal equilibrium. overall char gasification with Ar-rhenius- type rates.Sprouse* ,131979One- dimensional hydrogasification; free-stream e Extensive study of boundary layerquilibrium chemistry; one-step devolatilization and around the particles of Rockwell Inthydrogasification model.FHP gasifier, compared well with out-let measurements for coal gasifierFinsonet al1978Steady, one-dimensional model，with gaseous ki- Predictions compared with laboratorynetics; kinetics from data for coal pyrolysis; het- gasification measurements of axial tem-erogeneous oxidation; considered the char struc- perature and gas composition.ture and reactivity.Ubhayakar,￥,31977One-dimensional steady-state ;two-steple- Applied to gasification combustion andStickler &. Cannonvolatilization; combined diffusion &. surface reachydropyrolysis with good agreement..ntion rates; no radiation; equilibrium gas phase re-actions.Blake et al1977-1979 Three- dimensional，transient， mixed finite-ele- Study the effect of particle size， thement, finite- difference scheme with separate Eule- conservation of mass, momentum andrian particle equations; two equation gaseous tur- energy, studied the locus or velocitybulence; separate turbulent kinetics energy for par- vectorsticles.Barnhart et alCombination of plug-ments; gas phase in equilibrium with two equation composition， temperature; reportedkinetics for pyrolysis. char oxidation and CO oxi- fair to good comparison between exper-dation.iment 8. theory for cyclone gasifier.Smith &. Smoo￥.81979- 1981 One dimensional steady-state, two-step de- Good agreement with one- dimensionalvolatilization, combined diffusion &. surface reac- combustor data。 poor agreement withtion rates. one- dimensional zonal radiation， equi- gasifier measurements.librium gas phase reactions.Smith, Fletcher, * .121979- 1981 Two dimensional, axisymmetric， with recircula-Gas -phase components reported andSmoottion, k-ε turbulence model. Lagrangian particles. compared with experiment data.two-step devolailization, diffusion and kinetic het-erogeneous rates, four-flux radiation with scatter-ing.Wen & Chuang興,10Divided gasifier into three zones; one -step de- Predieted temperature and gas compo-volatilization, gas phase combustion completely or sition data for Texaco gasifier com-equilibrium gas phase reactions, consider diffusion pared with pilot plant gasified coal andand kinetic rates for char reaction.H-coal residue, with good agreement.Goyal141980One-dimensional steady-state model， Johnson's Modeling bench- scale hydrogasifier ofhydropyrolysis model. continuity equations for Citys Service R &. DCo.both phases, mixture momentum balance and ther-mal energy balance considered.Govind and Shan61984Refined the Wen &. Chuang model, considered the The gas composition and carbon con-momentum balance,version depends on three. essential pa-rameters: the fuel rate. the oxygen tofuel ratio and the steam fuel ratio; theoptimum steam-fuel ratio is between0.8-0.9 to achieve 98%-99% conver-sinnt the: steam fu.l ratinsicnifirantly10煤炭轉(zhuǎn)化2001年.續(xù)表1Auther(s)ReferencesYearMain Contents/ DescriptionMajor ResultsGong Sunling et al11987Image the gasifier being composed of several paral- Axial gas/solid temperature and conlel reactors of which each has respective. homoge- version profiles were got. the initial re-neous particle size and also its own material and action rate very fast, and then slowheat balances ; one-dimensional equations similar to down significantly; the wall tempera-Smith's; the finite element method was used to cal-ture has influence on reaction.culate. the wall temperature. distribution and heat should be taken as an important param-loss.eter. :Brownet al51988Refined the Smith two dimensional model, gave Modeling the radial and axial gas phaseout a heat loss calculation method.profiles of four coals : investigated theeffect of full/ partial equilibrium. coalvolatiles。stoichiometric coefficients.heterogeneous. reaction rates. and heatloss on prediction results; the effect ofO/C and steam on gas composition andgasification efficiency.Ruprecht et alConsidered only three reaction, the gas composi- The agreement between prediction andtion inelude CO.H2.CO2. no CH4; equilibrium gas measured data is very good. the dis-phase reactions, carbon conversion controlled by crepancy normally amounts to 1% orO/C; mass and energy balance.less; it has been used for the evaluationof tests or process data.Vamvuka et al1:1995One- dimensional steady-state. plug-flow. ash did The boundary between combustionnot remain on the reacting particle surface. com- zone and gasification zones distinct, itsbined diffusion and chemical reaction kinetics, used location depend: on the gasifier pres-TGA data, equilibrium gas phase reactions, the sure; peak temperature of gas and solidmomentum balance neglected.near the boundary; coal conversion is. Lhutnot sensitive to the pyrolysis rate，sensitive to pressure; the effect of op-eration conditions was discussed.Ni &. Williams :A multivariable model was set up on the basis of e- The oxygen to coal ratio is the mostquilibrium. mass balance and energy balance. the important control variable for the. gasi-Shell gasifier as a typical model; the gas composi- fier operation; the cold gas efficieneytion are good agreement with realistic data.increases with the increasing tempera-ture of inlet flow. steam to coal ratiohas influence on the efficiency.LiuG Set al181999 !One-dimensional steady -state. plug- flow，the gas The predicted carbon conversion agreeturbulence is negleeted, kinetic data from PTGA with those measured in the gasifier of 8tests; considered the pore structure and reactivity coals; the better prediction results canof char; the heat balance between the wall, gas, be got by considered char structure;and particles.modeled the CSIRO atmosphere. gasifi-er and 2.4 MPa Texaco gasifier.Bu Xuepeng,￥2000One-dimensional steady- state, divided gasifier into The 48 t/d and 2 600 t/d Prenflo gasi-Peng Wanwang,three zones; the devolatilization composition by fiers were modeled， axial gas-solidXu Zhengangcalculated, gas phase combustion completely, oth- temperature and composition were got，er gas reactions equilibrium; considered diffusion main gas composition agree with realand kinetic rates for gas-char reactions.data; the effect of oxygen to coal ratio,steam- coal ratio and gasification inten-sity on gasifier. operation results wdiscussed.Yu Zunhong,Based on cold model experiment, divided gasifier Based on Texaco gasifier realistic oper-Wang Fuchen.into three zones. ; the reactions different in each ation data, predicted the feature. tem-Gong Xin et aulzone; the mixed time and reaction time are consid- perature and gas composition at threeered as main variables, chemical reactions equilibri- different load, they are agreement withumrealistic data.Li Zheng,Divided gasifier into lots of zones along axial direc- Predicted axial gas-solid temperatureHan Zhiming ,tion, in order to consider the effect of gasifier and composition of Texaco gasifier;Wang Tianjiao et alstructure and size; gas phase and solid phase reac- and the effect of pressure, water slurrytion kinetics; retention time involved.composition, coal kinds on operationresults.Gao Juzhong.Equilibrium model, only thermodynamics was con- Predicted the gas composition and gasi-Wang Ningbo,sidered; took therelation between carbon conver- fication indexes of two coals gasified inZhang Yarusion and O/C ratio, reaction extent as boundary Shell gasifiers in pilot plant and demon-第4期步學(xué)朋等煤炭氣化氣流 床氣化爐的數(shù)學(xué)模擬I1表2模擬結(jié)果與實(shí)際結(jié)果的對(duì)比Table 2 1 Comparison of computational results from the models with experimental/ operation resultsAuthor(s)/Gas composition/%1SourceCarbon conversion/%GasifiersHCOCO2CH; H2S+COS N2+Ar H2OWenC YI1Experiment35.79 50.71 13. 140.090.030.2492.70 .TexacoModel37.30 47.86 14. 450.050.070.2694.87Watkinson[1024.30 47.10 13.20 0. 092.20.0.4012.723.70 47.20 13.30 0. 33:2.210.3013.0Watkinson30.60 61.501.600.001.304.70Shell30.30 61.501.400. 081.33; 5.3834.60 55. 407.00 0.001.951.01K-T34.90 55. 406. 700.001.931.03Qizhi Ni[17]Aetual)29.80 65. 401.70 0.000.941.9099.70 .29.7165.651.360.012.33:99. 70.Yu ZunbongOperation !37.47 45.84 16. 290.100.41Texcao38.31 44.84 15.010.110.910.82896. 20Li ZhengDocument29.80 41.05 10.20 0. 301. 100.8017.10Texeao30.55 40. 8010. 270.131.080.9616.20Gao JuzhongOperation25.60 65.100. 800.478.0399.0025.89 63. 790.00.357. 981.1999. 10Bu Xuepeng26.00 59. 593.73.0.729.96Prenflo25.93 60.212.660. 020.7710.4199.05Note:1) Percent of volume;2) Include NH;3) Others 0. 21.礎(chǔ)上,建立二維及多維動(dòng)態(tài)模型,并充分考慮顆粒大4結(jié)束語小分布、氣化爐內(nèi)氣固相流體力學(xué)行為等.另外為適應(yīng)氣化爐使用中國(guó)煤種的操作，需要研究適宜中國(guó)國(guó)外對(duì)氣流床氣化爐的數(shù)學(xué)模擬研究起步較煤粉的高溫高壓快速熱解反應(yīng)動(dòng)力學(xué)以確定其熱解早,經(jīng)過最近幾年的努力,我國(guó)對(duì)氣流床氣化爐的數(shù)速度及熱解煤氣組成，研究適宜煤種的氣化反應(yīng)動(dòng)學(xué)模擬也取得了初步成功，但正如專家們指出的那力學(xué)，為數(shù)學(xué)模擬提供基礎(chǔ)數(shù)據(jù).最后對(duì)建立的數(shù)學(xué)樣，目前離真正應(yīng)用還有-定距離.根據(jù)在模型建立模型還要到生產(chǎn)實(shí)際中進(jìn)行檢驗(yàn)，對(duì)某些參數(shù)進(jìn)行及求解過程的經(jīng)驗(yàn)，筆者認(rèn)為下一步應(yīng)繼續(xù)進(jìn)行氣修正,以求能較準(zhǔn)確反應(yīng)氣化爐內(nèi)氣化行為并用于流床氣化爐的數(shù)學(xué)模擬工作.在目前-維穩(wěn)態(tài)的基指導(dǎo)氣化爐設(shè)計(jì)及生產(chǎn)操作.參考文獻(xiàn)[1] WenC Y, Chuang T 2. 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In: Prospects for Coal Sciencein the 21st Century. Taiyuan : Shanxi Science & Technology Press. 1999. 579-582MATHEMATICAL MODELING OF COAL ENTRAINED-BED GASIFIERSBu Xuepeng Peng W anwang and Xu Zhengang(Beijing Research Institute of Coal Chemistry, China Coal Research Institute. 100013 Beijing)ABSTRACT The coal entrained bed gasification principle was briefly introduced in this pa-per. Based on relative documents, the mathematical modeling of coal entrained-bed gasifiers werereviewed. These include simple equilibrium models and kinetic models (one- dimensional or two/three- dimensional). The main contents-about hydromechanics, thermodynamics, chemical reac-tion kinetics, and mass balance, energy balance, momentum balance, of the models were givenout. The major results of models were also given. Finally. the comparison of computational re-sults from the models with experimental or operational results were given. It can be seen that theerrors of the main gas composition are very low.KEY WORDS coal gasification ,entrained-bed gasification , mathematical modeling(上接第6頁)DEVELOPMENT OF COAL STRUCTURECheng Jun Zhou Anning and Li Jianwei(Department of Material Engineering, Xi' an Unirversity ofScience and Technology, 710054,Xi' an)ABSTRACT The coal aggregative structure is discussed, including the origin, structure andswelling behavior of several macerals. Coal chemical structure models, physical structure modelsand synthesized models are analyzed and discussed. The development of coal structure research israised. At last, the utilization of coal structure research in new material field is summarized,which reveals the importance of coal structure research in further.