W型煤粉—流化床炉内的两相流动数值模拟
发布时间：2018-08-07 12:40
【摘要】：煤炭资源一直在我国的工业发展中扮演很重要的角色,无烟煤以及贫煤在煤炭总量中所占比例很大,因此近些年我国电厂陆续采用W型火焰燃烧技术的相关锅炉,专门用于燃烧无烟煤。W型火焰锅炉虽然有燃烧效率高等一系列优点,但是暴露出的结构复杂、NO_x排放量高、燃烧稳定性差等问题一直制约和影响W型火焰锅炉的发展。引入复合燃烧技术以及复合锅炉改造技术的方案是改进W型火焰锅炉的不错的选择。本文针对某厂350MW亚临界W型火焰锅炉进行复合锅炉技术改造,采用调整冷灰斗倾角,在下方续接鼓泡流化床的方案,充分利用流化床的稳定燃烧、脱硫效率高、负荷调节范围大等优势弥补W型火焰锅炉不足。由于时间和资金问题,现阶段只针对复合锅炉进行数值模拟计算,研究分析W型煤粉-流化床复合锅炉的流场特性以及异相反应的燃烧特性。本文使用欧拉-欧拉双流体等模型,在原W型火焰锅炉配风不变的情况下,模拟选取3个不同流化速度,研究流化床中不同大小流化速度对W型煤粉-流化床复合炉的流场特性的影响。通过分析不同工况的中心截面的流场和浓度场分布,流化速度可以影响到“W”型气流的形成、空间位置的高低以及流场的对称性。通过观察三次风口横截面空气、小颗粒的速度云图,可以更直观地分析“W”型气流的位置变化;通过在不同高度截线分析,研究空气、不同粒径的颗粒的浓度分布和速度分布,从而推出合理工况以及不同流化速度对整个流场的影响;在流场合理的工况中,截选多个横截面,观察分析整个复合炉的流场特性。选取流化床流化速度为1.3m/s的工况,保持配风风率不变,只改变三次风下倾角度,模拟选择下倾角度为0°、15°、30°、45°和60°一共五个工况,研究分析三次风倾角对复合炉流场的影响。通过对比五个工况中心截面上的浓度、速度分布,得出流场分布左右对称的三次风倾角。通过分析下行速度衰减曲线以及不同高度截线上的速度分布,进一步研究三次风倾角对复合炉流场的影响。针对W型煤粉-流化床复合炉内燃烧模拟计算,先是对燃烧反应模型的简化和设计,简化之后的燃烧过程主要是碳颗粒与氧气、二氧化碳进行的异相反应,并编写UDF控制化学反应速率。选用流化速度为1.3m/s的工况,设置合理的边界条件进行燃烧模拟计算。选取炉膛中心截面研究分析流场、温度场和浓度场的分布。三次风中心截面上的速度和温度分布反映出三次风口的流场分布和燃烧状况。选取三个不同截面上的中轴线上点的数据分析炉内温度、速度和浓度分布。同时又在复合炉三个不同区域选取不同高度的截线,分别研究W型火焰锅炉、流化床以及两者之间的过渡区域内的速度和温度分布。
[Abstract]:Coal resources have been playing a very important role in the industrial development of our country, anthracite and lean coal account for a large proportion of the total coal, so in recent years, power plants in China have adopted W-type flame combustion technology of related boilers. Although it has a series of advantages, such as high combustion efficiency and so on, the problems such as high NOx emission and poor combustion stability have been restricted and affected the development of W-type flame boiler. It is a good choice to improve W type flame boiler by introducing compound combustion technology and retrofitting technology of composite boiler. In this paper, the 350MW subcritical W type flame boiler of a certain factory is reformed with composite boiler technology. The scheme of adjusting the inclination of the cold ash bucket and connecting the bubbling fluidized bed below is adopted to make full use of the steady combustion of the fluidized bed and the desulfurization efficiency is high. The wide range of load regulation makes up for the shortage of W-type flame boiler. Due to the problem of time and fund, numerical simulation is carried out only for the composite boiler at this stage, and the characteristics of the flow field and the combustion characteristics of the heterogeneous reaction of the W-type coal-fluidized bed composite boiler are studied and analyzed. In this paper, Euler-Euler two-fluid model is used to simulate three different fluidization velocities under the condition that the distribution of air for the original W-type flame boiler is invariable. The effect of different fluidization rates on the flow field characteristics of W-type coal-fluidized bed composite furnace was studied. By analyzing the distribution of the flow field and concentration field of the central section under different working conditions, the fluidization velocity can affect the formation of "W" type airflow, the height of the space position and the symmetry of the flow field. By observing the velocity cloud diagram of the cross section of the third tuyere and the small particles, the position change of the "W" type airflow can be analyzed more intuitively, and the air can be studied by the section analysis at different heights. The distribution of concentration and velocity of particles with different particle sizes is used to deduce the influence of reasonable working conditions and different fluidization rates on the whole flow field, and in the reasonable working condition of the flow field, several cross-sections are intercepted and the flow field characteristics of the whole composite furnace are observed and analyzed. The fluidized bed fluidization velocity is selected as 1.3m/s condition, the air distribution rate is kept constant, and the downdip angle of the tertiary air is changed only. The downdip angle of 0 掳15 掳30 掳30 掳45 掳and 60 掳is selected in the simulation. The influence of the third air inclination angle on the flow field of the composite furnace is studied and analyzed. By comparing the concentration and velocity distribution on the central section of the five working conditions, the symmetrical distribution of the flow field and the third wind inclination angle are obtained. By analyzing the downlink velocity attenuation curve and the velocity distribution on different height sections, the influence of the third air inclination angle on the flow field of the composite furnace is further studied. In view of the combustion simulation calculation in W-type coal-fluidized bed composite furnace, the combustion reaction model is simplified and designed, and the combustion process after simplification is mainly the heterogeneous reaction of carbon particles with oxygen and carbon dioxide. The chemical reaction rate was controlled by UDF. The fluidization velocity is selected as 1.3m/s, and reasonable boundary conditions are set to simulate combustion. The distribution of flow field, temperature field and concentration field is analyzed by selecting the central section of furnace. The velocity and temperature distribution on the section of the tertiary air center reflects the distribution of the flow field and the combustion state of the tertiary air outlet. The temperature, velocity and concentration distribution in the furnace were analyzed by selecting the data of three points on the axis of three different sections. At the same time, the velocity and temperature distribution in the W-type flame boiler, fluidized bed and the transition zone between them were studied by selecting different section lines in three different regions of the compound furnace.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621.2
本文编号：2170053
[Abstract]:Coal resources have been playing a very important role in the industrial development of our country, anthracite and lean coal account for a large proportion of the total coal, so in recent years, power plants in China have adopted W-type flame combustion technology of related boilers. Although it has a series of advantages, such as high combustion efficiency and so on, the problems such as high NOx emission and poor combustion stability have been restricted and affected the development of W-type flame boiler. It is a good choice to improve W type flame boiler by introducing compound combustion technology and retrofitting technology of composite boiler. In this paper, the 350MW subcritical W type flame boiler of a certain factory is reformed with composite boiler technology. The scheme of adjusting the inclination of the cold ash bucket and connecting the bubbling fluidized bed below is adopted to make full use of the steady combustion of the fluidized bed and the desulfurization efficiency is high. The wide range of load regulation makes up for the shortage of W-type flame boiler. Due to the problem of time and fund, numerical simulation is carried out only for the composite boiler at this stage, and the characteristics of the flow field and the combustion characteristics of the heterogeneous reaction of the W-type coal-fluidized bed composite boiler are studied and analyzed. In this paper, Euler-Euler two-fluid model is used to simulate three different fluidization velocities under the condition that the distribution of air for the original W-type flame boiler is invariable. The effect of different fluidization rates on the flow field characteristics of W-type coal-fluidized bed composite furnace was studied. By analyzing the distribution of the flow field and concentration field of the central section under different working conditions, the fluidization velocity can affect the formation of "W" type airflow, the height of the space position and the symmetry of the flow field. By observing the velocity cloud diagram of the cross section of the third tuyere and the small particles, the position change of the "W" type airflow can be analyzed more intuitively, and the air can be studied by the section analysis at different heights. The distribution of concentration and velocity of particles with different particle sizes is used to deduce the influence of reasonable working conditions and different fluidization rates on the whole flow field, and in the reasonable working condition of the flow field, several cross-sections are intercepted and the flow field characteristics of the whole composite furnace are observed and analyzed. The fluidized bed fluidization velocity is selected as 1.3m/s condition, the air distribution rate is kept constant, and the downdip angle of the tertiary air is changed only. The downdip angle of 0 掳15 掳30 掳30 掳45 掳and 60 掳is selected in the simulation. The influence of the third air inclination angle on the flow field of the composite furnace is studied and analyzed. By comparing the concentration and velocity distribution on the central section of the five working conditions, the symmetrical distribution of the flow field and the third wind inclination angle are obtained. By analyzing the downlink velocity attenuation curve and the velocity distribution on different height sections, the influence of the third air inclination angle on the flow field of the composite furnace is further studied. In view of the combustion simulation calculation in W-type coal-fluidized bed composite furnace, the combustion reaction model is simplified and designed, and the combustion process after simplification is mainly the heterogeneous reaction of carbon particles with oxygen and carbon dioxide. The chemical reaction rate was controlled by UDF. The fluidization velocity is selected as 1.3m/s, and reasonable boundary conditions are set to simulate combustion. The distribution of flow field, temperature field and concentration field is analyzed by selecting the central section of furnace. The velocity and temperature distribution on the section of the tertiary air center reflects the distribution of the flow field and the combustion state of the tertiary air outlet. The temperature, velocity and concentration distribution in the furnace were analyzed by selecting the data of three points on the axis of three different sections. At the same time, the velocity and temperature distribution in the W-type flame boiler, fluidized bed and the transition zone between them were studied by selecting different section lines in three different regions of the compound furnace.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621.2
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