1、翻译部分英文原文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 T
2、echnology Wuhan, Hubei, ChinaWuhan, Hubei, China Zzw19660508xjlclxyAbstractIn 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 nu
3、merical 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 mode
4、l; 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;
5、 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 temper
6、ature 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 co
7、ntrol 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
8、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
9、 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 d
10、ifferent 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
11、 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 h
12、exahedral 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
13、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
14、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 ef
15、fective 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.
