旋转石灰窑中以不同类型的煤进行的煤和天然气燃烧的数字模拟外文文献翻译、中英文翻译

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.中文译文旋转石灰窑中以不同类型的煤进行的煤和天然气燃烧的数字模拟 谢峻林 李玉梅 梅书霞 张正文 中国 湖北 武汉 中国 湖北 武汉 武汉理工大学 材料科学与工程重点实验室 武汉钢铁集团 乌龙泉石灰矿 Z摘要：为了改善煤燃烧的环境，这篇文章以武汉钢铁集团公司乌龙泉石灰矿活性石灰旋转窑为依据，以数字模拟的方式集中探究了煤和天然气的多燃料燃烧。为了讨论火焰和煤组成的关系，我们对不同品质的四种煤进行了比较。气相通过-两平衡动荡模型进行了表达；分离相则通过粒子轨道模型；燃烧以非预混模型；而辐射则以P1辐射模型。结果显示煤中易挥发组分比例对煤的早期燃烧有很大的影响；天然气很快的燃烧来加热煤和气流。关键词：旋转窑；多燃料燃烧；煤；天然气；数字模拟；煤品质；挥发组分.简介在活性石灰的生产线上，旋转窑起着原浆的反应器、熔炉供应以及传热等作用。为了加强这些功能，合适的以及统一的温度分布被严格要求着。实际上，许多产品采用天然气或者煤气作为燃料仅仅是因为跟煤相比，它们的火焰更加的便于控制【1】，尽管成本较高。为了降低成本和探究劣等的煤，我们需要控制生产过程，并且找到一种新的煤燃烧的方式。武汉钢铁集团公司乌龙泉石灰矿采用一种新的技术-煤与天然气共燃技术。在此基础上，通过控制煤的品质能带来明显的效果【2】。然而，我国大多数煤属于劣等煤，很难达到要求【3】。因此，这篇论文意在探究劣等煤的燃烧。通常，煤的燃烧过程包括三个部分，即易挥发组分的释放，然后是气体的燃烧，最后是焦炭的燃烧【4】。煤的品质根据其组成（挥发组分，灰分含量等等）和性质（颗粒大小，密度，孔隙率等等）的不同而不同【5】。这些性质在实际生产线上可以通过燃料处理来控制，因此在相同的临界条件下，这篇文章选取了四种不同组成的煤，并且通过数字模拟的方法主要讨论了煤-天然气共燃体系中组成对燃烧过程的影响。. 几何模型图1（a）展示了的旋转窑的结构，长50米，半径4.45米。图1（b）给出了生产线使用的炉腔结构。从图1（b）我们得知炉腔有五条通道，包括两条进料通道（分别用于天然气流和煤）和三条进气通道（分别用于中心气、漩涡气和轴向气）。图2展示了筛网。六边形结构的格栅被用于整个计算区域，筛网包裹在炉腔周围。.数学模型需要考虑的因素包括流体流动、热量传递、旋转窑中的燃烧现象以及原浆的反应。整个数学模拟模型所有这些都纳入考虑，除了碳酸盐的分解以外，这么做是为了简化案例，这么做是合理的根据平衡假设。因此，需要一些亚模型来探讨动荡、热对流、燃烧和辐射。A.气相模型气相以-两平衡动荡模型进行表达，这一点被广泛应用于燃烧工程中。气相的控制方程一般表述形式如下： 其中是流体密度，V是流体速度，是通用微分变量，是有效黏度，S是气相源项。B分离相模型分离相以分离相模型表述（DPM），粒子轨道模型的引入，把颗粒看做随着流体穿过轨道时的分散滑动。这个模型的控制方程包括四个基本方程，包括位置方程（2），动量方程（3），质量方程（4）和能量方程（5）其中是位置，t是时间，C是速度其中m是颗粒质量，F是作用力其中mc是颗粒成分质量，mF成分是颗粒的质量分数，mFG是连续相的质量分数其中是热对流因子，TG是流体温度，T是颗粒温度C辐射模型该案例中选用的辐射模型为P-1模型，考虑颗粒和流体之间的辐射恢复。控制方程如下：其中是吸收因子，S是分散因子，G是辐射输入，C是线性-各向异性方程。D燃烧模型燃烧过程以非预混模型作为模型，主要涉及一个或两个守恒标量（混合分数f）的传递方程的求解。物系浓度从预测的混合分数场中获得。震荡和化学之间相互关系以假定形状的概率密度函数（PDF）来解释。平均（密度平均）混合分数方程为：其中Sm是