旋轉(zhuǎn)石灰窯中以不同類型的煤進行的煤和天然氣燃燒的數(shù)字模擬外文文獻翻譯、中英文翻譯

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 ZAbstractIn 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 材料科學與工程重點實驗室 武漢鋼鐵集團 烏龍泉石灰礦 Z摘要：為了改善煤燃燒的環(huán)境，這篇文章以武漢鋼鐵集團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)的四種煤進行了比較。氣相通過-兩平衡動蕩模型進行了表達；分離相則通過粒子軌道模型；燃燒以非預混模型；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)窯起著原漿的反應器、熔爐供應以及傳熱等作用。為了加強這些功能，合適的以及統(tǒng)一的溫度分布被嚴格要求著。實際上，許多產(chǎn)品采用天然氣或者煤氣作為燃料僅僅是因為跟煤相比，它們的火焰更加的便于控制【1】，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，包括兩條進料通道（分別用于天然氣流和煤）和三條進氣通道（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。整個數(shù)學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。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-兩平衡動蕩模型進行表達，這一點被廣泛應用于燃燒工程中。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。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)量分數(shù)，mFG是連續(xù)相的質(zhì)量分數(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?？刂品匠倘缦拢浩渲惺俏找蜃?，S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混模型作為模型，主要涉及一個或兩個守恒標量（混合分數(shù)f）的傳遞方程的求解。物系濃度從預測的混合分數(shù)場中獲得。震蕩和化學之間相互關(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）混合分數(shù)方程為：其中Sm是