孔莊煤礦2.4Mta新井設(shè)計含5張CAD圖-采礦工程.zip

孔莊煤礦2.4Mta新井設(shè)計含5張CAD圖-采礦工程.zip,煤礦,2.4,Mta,設(shè)計,CAD,采礦工程 英文原文Numerical Simulation of Coal and Natural Gas Cocombustion in a Rotary Lime Kiln with Different Types of CoalJunlin Xie, Yumei Li, Shuxia Mei Zhengwen ZhangKey Laboratory of Silicate Materials Science and Wulongquan Limestone MineEngineering Wuhan Iron & Steel Group Corp.Wuhan University of Technology Wuhan, Hubei, ChinaWuhan, Hubei, China Zzw19660508163.comxjlclxy126.comAbstractIn order to improve the coal combustion condition, this essay based on an active lime rotary kiln in Wulongquan Limestone Mine of WISCO, focuses on the multifuel combustion of the coal together with natural gas by means of numerical simulation. To discuss the relationship of the flames with the coal composition, the cases with four different qualities of coal were compared. The gas phase is expressed with - two-equation turbulence model; the discrete phase with particle track model; the combustion with non-premixed model; and the radiation with P1 radiation model. The results show that the volatile fraction content of coal has important impact on the early stage of the coal combustion; the natural gas burns out quickly to heat the coal and the gas flow.Keywords-rotary kiln; multifuel combustion; coal; natural gas; numerical simulation; coal qualities; volatile fractionI. INTRODUCTIONIn the production line of active lime, the rotary kiln plays an important part, which serves as the reactor of raw slurry and the furnace supplying and conducting heat. To implement these functions, appropriate and uniform temperature distribution is demanded strictly. Actually, many producers take the natural gas or the coal gas as fuel just because the flames of them are more convenient to be controlled 1 than the coals regardless of the high cost. In order to cut down the cost and explore the inferior coal, we need to control the production processes, and find a new way for coal combustion. Wulongquan Limestone Mine of WISCO adopts a new technology of coal and natural gas co-combustion. On this basis, controlling of the quality of coal can bring about obvious effects 2. However, the majority of coal in our country belongs to the inferior, which is difficult to meet the demand 3. So, this paper is meant to study the combustion of inferior coal.Generally, coal combustion process include three parts, that is volatile fraction giving off, then the gas burning, and finally the char burning 4. The qualities of coal vary with the compositions (volatile fraction, ash content, and so on) and properties (particle size, density, porosity and so on) 5. These properties in real production line can be controlled by the fuel treatment, so under the same boundary conditions, this paper chooses four kinds of coal with different compositions, and mainly discusses the composition that affects the combustion process of coal and natural gas co-combustion by numerical simulation.II. GEOMETRIC MODELFig.1 (a) shows the structural of the rotary kiln, with 50m in length and 4.45m in radial. Fig.1 (b) gives the structure of the burner the production line utilizing. From Fig.1 (b) we know that the burner has five channels, which contain of two fuel inlets (for natural gas flow and coal, respectively) and three air inlets (for central air, swirling air, and axial air, respectively). Fig. 2 shows the meshes. Structural hexahedral grid was used in the whole computational domain with mesh refined around the burners.III. MATHEMATICAL MODELThe case includes the fluid flow, heat transfer, and combustion phenomena inside the rotary kiln as well as the reaction of raw slurry. The whole model of numerical simulation takes all of these into consideration except the decomposition reaction of carbonas in order to simplify the case, which is reasonable with the equilibrium assumption. Consequently, some sub models are needed to deal with turbulence, thermal convection, combustion, and radiation.A. The gas phase modelThe gas phase is expressed with the - two-equation turbulence model, which is widely used in engineering of combustion. The general form of the governing equations for the gas phase is given as follows: (1)Where is the fluid density, V is the velocity of the fluid, the general different variable, the effective viscosity, S the source term of the gas phase.B. The discrete phase modelThe discrete phase model is expressed with Discrete Phase Model (DPM), the injection with the particle track model, which considers the particles as the dispersion slipping with the fluid going through the tracks. The governing equations of such model consist four basic ones, including position equation (2), momentum one (3), massive one (4), and energy one (5). (2)Where is the position, t is the time, C the velocity. (3)Where m is the mass of the particle, F the force applied. (4)Where mC is the mass of particle content, mF the mass percent of the particles and mFG is of the continuum phase. (5)Where is the coefficient of thermal conductivity, TG the temperature of fluid, T is the temperature of particles.C. The radiation modelThe radiation model chosen in this case is P-1 model which considers the radiation recuperation between the particles and the fluid. The governing equation goes as follows: (6)Where is the coefficient of absorption, S the coefficient of scatter, G the radiation input, C the linear-anisotropic phase function.D. The combustion modelThe combustion is modeled by the non-premixed modeling, which involves the solution of transport equations for one or two conserved scalars (the mixture fractions f). The species concentrations are derived from the predicted mixture fraction fields. Interaction of turbulence and chemistry is accounted for with an assumed-shape Probability Density Function (PDF). The mean (density-averaged) mixture fraction equation is: (7)Where Sm is the source term which represent the transfer mass into the gas phase from the particles, and S is the second fuel stream. IV. BOUNDARY CONDITIONS AND NUMERICAL SOLUTIONThe industrial analysis and the elementary analysis of the four kinds of coal are listed in the Table . The heating effect of each coal is set to be the same, and all velocities and temperature were specified at the inlet, as Table lists. The outlet is set with negative pressure outlet of -130 Pascal. The no-slip wall is divided into four sectors, each of which is set at different temperature.V. RESULTS AND DISCUSSIONSFig.3 and Fig.4 show the temperature contour maps at the cross middle slices of the rotary kiln. The shapes of flames are fit well for the production looking like a mallet, and about 18m in length. Besides, comparing the four kinds, the flame approximately are the same. This just conveys the rotary kiln is insensitive to the quality of the coal, thanks to the natural gas. The same conclusion can be made in the Fig.4, which presents the partial enlarged drawing of the flames.However, there indeed are some tiny differences among them, if being carefully observed. Focus on the partial drawings locating at 7.5m longitudinally, we can find the diameters of the red part (high temperature area) decrease and the central hollow cores disappear gradually from 0# to 3#. These are mainly because of the volatile fraction and ash content.Fig.5, Fig.6 and Fig.7 give us the scatter picture of average mole fraction of the volatile fraction, CH4 and CO in the cross middle slice of the kiln.In Fig.6, the CH4 decreases sharply within 0.5m longitudinally, which says that the natural gas is mainly contributed to heat the coal in the early stage of the combustion, in order to speed up the coal burning. As the same CH4 gives almost equal amount of heat, the changing of releasing speed of volatile fraction is independent of CH4 in the Fig.6. The releasing speed of volatile fraction increases with its percentage rising from 0# to 3#. But in the Fig.7，there is an abnormality. It can be explained as that the coal quality of 0# one is better than the rest three ones, so the diffusion of the gas including CH4 and CO, even including the volatile fraction part, is quicker than the others in the axial direction, and that s just why the flame diameter of 0# is larger.In Fig.7, the change tendency of CO is anastomotic with the contour of the flame. So we can define the frame of the flame according to the concentration of CO, just as Fig.8, the coordination surface of CO with the 0.007 mole fraction shows. These two pictures prove that the combustion begin with the reaction of CO and O2 drastically and continuously. This implies that the char and volatile fraction should break up CO firstly, and the concentration of CO and O2 must meet the requirement of chemical kinetics, and then the continuous combustion begins.Besides, Fig.8 shows that apart from 0#, the rest ones didnt burnout completely according to the top “rings” around the flames suggesting the existence of char. This also leads to increase the flame length. So it is necessary to further improve the production processes to avoid such case.VI. CONCLUSIONSIn this paper, by means of numerical simulation, we gain such conclusions: the natural gas in the multifuel combustion serves as a heater for coal and gas flow in the rotary kiln, which can broaden the range of the coal; and the whole combustion process begins with CH4 burnout, while the inflammation with CO burning drastically and continuously; the richer the volatile fraction, the larger diameter the flame is; the more difficult the char burns out, the longer the flame will be.ACKNOWLEDGMENTThe authors owe much thanks to the supports of Wulongquan Limestone Mine for their funding the project and providing experimental dates.REFERENCES1 Jintao Sun, “The thermotechnical foundation of metasilicate industry,” Wuhan, Wuhan University of Technology Press, 2006. 222236.2 Shuxia Mei, “Numerical simulations of gas-solid flow field and coal combustion in precalciners of cement industry for optimization,” D, Wuhan University of Technology, 2008. 912.3 Chaoqun Wang, “the combustion of inferior coal and the design of burnor,” J. New centry cements introduction, 4th ed., vol.5, pp. 69, 1999.4 Haitao Li, “Technologies and Machines of the New Dry Cement Production,” Beijing, Chemical Industry Press, 2006. 188192.5 L. Douglas Smoot, Philip J. Smith, “Coal Combustion and Gasification,” (Weibiao Fu, Jingbin Wei, and Yanping Zhang interpreter). Beijing: Science Press, 1992. 3880.中文譯文旋轉(zhuǎn)石灰窯中以不同類型的煤進(jìn)行的煤和天然氣燃燒的數(shù)字模擬 謝峻林 李玉梅 梅書霞 張正文 中國 湖北 武漢 中國 湖北 武漢 武漢理工大學(xué) 材料科學(xué)與工程重點(diǎn)實(shí)驗(yàn)室 武漢鋼鐵集團(tuán) 烏龍泉石灰礦 xjlclxy126.com Zzw19660508163.com摘要：為了改善煤燃燒的環(huán)境，這篇文章以武漢鋼鐵集團(tuán)公司烏龍泉石灰礦活性石灰旋轉(zhuǎn)窯為依據(jù)，以數(shù)字模擬的方式集中探究了煤和天然氣的多燃料燃燒。為了討論火焰和煤組成的關(guān)系，我們對不同品質(zhì)的四種煤進(jìn)行了比較。氣相通過-兩平衡動蕩模型進(jìn)行了表達(dá)；分離相則通過粒子軌道模型；燃燒以非預(yù)混模型；而輻射則以P1輻射模型。結(jié)果顯示煤中易揮發(fā)組分比例對煤的早期燃燒有很大的影響；天然氣很快的燃燒來加熱煤和氣流。關(guān)鍵詞：旋轉(zhuǎn)窯；多燃料燃燒；煤；天然氣；數(shù)字模擬；煤品質(zhì)；揮發(fā)組分.簡介在活性石灰的生產(chǎn)線上，旋轉(zhuǎn)窯起著原漿的反應(yīng)器、熔爐供應(yīng)以及傳熱等作用。為了加強(qiáng)這些功能，合適的以及統(tǒng)一的溫度分布被嚴(yán)格要求著。實(shí)際上，許多產(chǎn)品采用天然氣或者煤氣作為燃料僅僅是因?yàn)楦合啾龋鼈兊幕鹧娓拥谋阌诳刂啤?】，盡管成本較高。為了降低成本和探究劣等的煤，我們需要控制生產(chǎn)過程，并且找到一種新的煤燃燒的方式。武漢鋼鐵集團(tuán)公司烏龍泉石灰礦采用一種新的技術(shù)-煤與天然氣共燃技術(shù)。在此基礎(chǔ)上，通過控制煤的品質(zhì)能帶來明顯的效果【2】。然而，我國大多數(shù)煤屬于劣等煤，很難達(dá)到要求【3】。因此，這篇論文意在探究劣等煤的燃燒。通常，煤的燃燒過程包括三個部分，即易揮發(fā)組分的釋放，然后是氣體的燃燒，最后是焦炭的燃燒【4】。煤的品質(zhì)根據(jù)其組成（揮發(fā)組分，灰分含量等等）和性質(zhì)（顆粒大小，密度，孔隙率等等）的不同而不同【5】。這些性質(zhì)在實(shí)際生產(chǎn)線上可以通過燃料處理來控制，因此在相同的臨界條件下，這篇文章選取了四種不同組成的煤，并且通過數(shù)字模擬的方法主要討論了煤-天然氣共燃體系中組成對燃燒過程的影響。. 幾何模型圖1（a）展示了的旋轉(zhuǎn)窯的結(jié)構(gòu)，長50米，半徑4.45米。圖1（b）給出了生產(chǎn)線使用的爐腔結(jié)構(gòu)。從圖1（b）我們得知爐腔有五條通道，包括兩條進(jìn)料通道（分別用于天然氣流和煤）和三條進(jìn)氣通道（分別用于中心氣、漩渦氣和軸向氣）。圖2展示了篩網(wǎng)。六邊形結(jié)構(gòu)的格柵被用于整個計算區(qū)域，篩網(wǎng)包裹在爐腔周圍。.數(shù)學(xué)模型需要考慮的因素包括流體流動、熱量傳遞、旋轉(zhuǎn)窯中的燃燒現(xiàn)象以及原漿的反應(yīng)。整個數(shù)學(xué)模擬模型所有這些都納入考慮，除了碳酸鹽的分解以外，這么做是為了簡化案例，這么做是合理的根據(jù)平衡假設(shè)。因此，需要一些亞模型來探討動蕩、熱對流、燃燒和輻射。A.氣相模型氣相以-兩平衡動蕩模型進(jìn)行表達(dá)，這一點(diǎn)被廣泛應(yīng)用于燃燒工程中。氣相的控制方程一般表述形式如下： 其中是流體密度，V是流體速度，是通用微分變量，是有效黏度，S是氣相源項(xiàng)。B分離相模型分離相以分離相模型表述（DPM），粒子軌道模型的引入，把顆?？醋鲭S著流體穿過軌道時的分散滑動。這個模型的控制方程包括四個基本方程，包括位置方程（2），動量方程（3），質(zhì)量方程（4）和能量方程（5）其中是位置，t是時間，C是速度其中m是顆粒質(zhì)量，F(xiàn)是作用力其中mc是顆粒成分質(zhì)量，mF成分是顆粒的質(zhì)量分?jǐn)?shù)，mFG是連續(xù)相的質(zhì)量分?jǐn)?shù)其中是熱對流因子，TG是流體溫度，T是顆粒溫度C輻射模型該案例中選用的輻射模型為P-1模型，考慮顆粒和流體之間的輻射恢復(fù)?？刂品匠倘缦拢浩渲惺俏找蜃樱琒是分散因子，G是輻射輸入，C是線性-各向異性方程。D燃燒模型燃燒過程以非預(yù)混模型作為模型，主要涉及一個或兩個守恒標(biāo)量（混合分?jǐn)?shù)f）的傳遞方程的求解。物系濃度從預(yù)測的混合分?jǐn)?shù)場中獲得。震蕩和化學(xué)之間相互關(guān)系以假定形狀的概率密度函數(shù)（PDF）來解釋。平均（密度平均）混合分?jǐn)?shù)方程為：其中Sm是源項(xiàng)，代表顆粒轉(zhuǎn)換進(jìn)入氣相的質(zhì)量，S是第二個燃料流股。.邊界條件和數(shù)學(xué)解四種煤的工業(yè)分析和元素分析列在表中。每一種煤的加熱效果設(shè)定相同，所有的速度和溫度都在進(jìn)口處被規(guī)定，如表所示。出口處設(shè)定為負(fù)壓130Pa. 非滑動性的壁面被分成四部分，每一部分設(shè)定不同的溫度。.結(jié)果和討論圖3圖4顯示了旋轉(zhuǎn)窯中央切面的溫度分布輪廓圖。火焰的形狀非常適合生產(chǎn)，看起來像一個木槌，并且18米長。除此之外，通過比較這四種煤，火焰大致相同。這恰恰證明了由于天然氣的作用，旋轉(zhuǎn)窯對煤的品質(zhì)差別不敏感。通過圖4火焰的局部放大圖可以得到相同的結(jié)論。然而，如果仔細(xì)觀察的話，它們還是有微小的區(qū)別的。仔細(xì)觀察局部放大處長度7.5米的地方，我們能夠發(fā)現(xiàn)紅色部分（高溫區(qū)）的直徑減小了，并且中心空核逐漸從0#到3#消失。這主要是由于易揮發(fā)組分和灰分的緣故。圖5圖6圖7給我們展示了易揮發(fā)組分的平均摩爾百分比、在窯的中心截面處甲烷和一氧化碳的摩爾百分比。圖6中，甲烷在0.5米的范圍內(nèi)急劇減少，這一點(diǎn)說明為了加速煤的燃燒，天然氣在燃燒的早期過程中對煤的加熱起主要作用。由于同樣的甲烷給出幾乎相同的熱量，圖6中揮發(fā)組分釋放速度的改變與甲烷無關(guān)。揮發(fā)組分的釋放速度隨著它的比例由0#增加到3#而增加。但是在圖7中有一個異常。這能夠這樣解釋：0#的煤的品質(zhì)比其他三個好，因此甲烷和一氧化碳，甚至包括易揮發(fā)性組分，它們的擴(kuò)散比其他的在軸向上的擴(kuò)散要快，這就是為什么0#的火焰直徑要大。圖7中，一氧化碳的變化趨勢與火焰的輪廓相吻合，因此我們可以根據(jù)一氧化碳的濃度來定義火焰的形狀，就像圖8中摩爾分?jǐn)?shù)為0.007的一氧化碳的等同面所示的那樣。這兩張圖片證明了燃燒從一氧化碳和氧氣的劇烈的不斷的反應(yīng)開始。這揭示了炭和揮發(fā)性組分應(yīng)當(dāng)首先分解出一氧化碳，并且一氧化碳和氧氣的濃度必須到達(dá)化學(xué)動力學(xué)的要求，然后持續(xù)的燃燒開始了。除此之外，圖8還表明除了0#，其它的煤并沒有充分燃燒，根據(jù)火焰周圍的頂部“環(huán)”可以判斷，這意味這炭的存在。這也導(dǎo)致了火焰長度的增加。因此進(jìn)一步改進(jìn)生產(chǎn)過程避免這種情況是十分必要的。.結(jié)論這篇文章中，通過數(shù)字模擬，我們獲得了這樣的結(jié)論：天然氣在多燃料燃燒中起對旋轉(zhuǎn)窯中的煤和氣流的加熱作用，這一點(diǎn)可以拓寬煤的范圍；并且整個燃燒過程從甲烷的燃燒開始，然后是一氧化碳的急劇和持續(xù)的燃燒；易揮發(fā)組分越豐富，火焰的直徑越大；炭越難燃盡，火焰越長。致謝作者在此對烏龍泉石灰礦對該項(xiàng)目的資金援助和實(shí)驗(yàn)數(shù)據(jù)支持表示感謝參考文獻(xiàn)（1）孫錦濤 硅酸鹽業(yè)的熱工基礎(chǔ) 武漢：武漢理工大學(xué)出版社2006 222-236 （2）梅書霞 氣固兩相流場的數(shù)字模擬和硅酸鹽工業(yè)中煤炭燃燒的優(yōu)化 武漢理工大學(xué) 2008 9-12（3）王朝群 劣質(zhì)煤的燃燒和燃燒爐的設(shè)計 新型粘合劑簡介4th ed vo1.5 pp6-9 1999（4）李海濤 新型干燥劑生產(chǎn)的工藝與設(shè)備 北京化工出版社 2006 188-192（5）L.Douglas Smoot,Philip J.Smith 煤炭的燃燒與氣化（Weibiao Fu, Jingbin Wei, and Yanping Zhang翻譯）北京科技出版社 1992 38-80