生物质与煤混烧灰相互作用的模拟研究
发布时间：2019-02-25 10:27
【摘要】：我国面临着能源危机和环境污染双重挑战,因此开发新能源部分替代煤是我国能源改革优化的重要方向。我国属于农业大国,生物质能源作为一种丰富清洁的可再生能源可代替部分煤,同时由于燃煤排放至大气中的细颗粒物过多,导致我国现阶段作为严重的雾霾等问题,细颗粒的排放对人类的生存环境造成巨大的威胁,因此研究生物质与煤混烧灰的细颗粒物在电除尘器内部的相互作用从而实现尾部细颗粒的减排是燃煤电站开发新能源过程中必不可少的,这对于探求可代替煤的最佳生物质能源是十分重要的。本文选取的燃料分别为常见的生物质燃料玉米秸秆与无烟煤两种燃料,首先将玉米秸秆破碎后分别按照0、10%、15%、20%、100%的比例与无烟煤混掺后,经燃烧形成一系列混烧灰。首先通过实验对这一系列混烧灰的理化特性(真密度、粒径分布)等进行了实验研究,为后续混烧灰在电除尘器内部的相互作用情况做准备。实验结果表明随着生物质玉米秸秆与无烟煤混烧比例的增加,混烧灰的真密度呈现逐渐下降的趋势。同时由于玉米秸秆与无烟煤的混合燃烧,使得其粒径分布较纯无烟煤灰或纯玉米秸秆灰发生了一定变化,但变化不是很明显,其粒径分布的峰值相同或接近。其次,本文主要对电除尘器内部三种团聚机理(热团聚、湍流团聚、电团聚)进行了模拟研究,首先根据颗粒粒径确定了不同团聚机理下的团聚核函数。由三种团聚核函数可知,热团聚效果与发生团聚的两颗粒粒径的差值相关,差值越大,热团聚核函数愈大,并且热团聚作用对亚微米级颗粒的团聚效果优于微米级颗粒。湍流团聚效果与颗粒粒径相关,颗粒粒径越大,团聚效果愈佳,湍流团聚对微米级颗粒聚并作用优于亚微米级颗粒。电团聚效果愈颗粒粒径相关,颗粒粒径越大,其所带荷电量越多,电团聚效果越明显,电团聚对于微米级颗粒以及亚微米级颗粒的团聚效果均很明显。最后在确定了团聚核函数后,利用Fluent软件对生物质与煤混烧灰在电除尘器内部的相互作用情况进行了模拟研究。首先通过自带的自定义函数功能(UDF)将不同的团聚核函数程序导入软件中,接着利用颗粒群平衡模型(PBM)与欧拉-欧拉双流体模型耦合,采用Sectional分区算法进行求解。研究结果表明:当流场流速为1.0m/s,颗粒体积分数为1.4%时热团聚效果最佳,并且在玉米秸秆与无烟煤混掺比为10%时热团聚效果最好;当流场流速为1.5m/s,颗粒体积分数为1.4%时湍流团聚效果最佳;当流场流速为1.0m/s,颗粒体积分数为1.4%时电团聚效果最佳,并且在玉米秸秆与无烟煤混掺比为10%时电团聚效果最佳。电除尘器中颗粒团聚主要以电团聚为主,热团聚和湍流团聚为辅,三者共同为微米级颗粒的团聚起到十分重要的促进作用。因此发展超细颗粒物团聚减排新技术,应特别重视电团聚技术、热团聚技术以及湍流团聚技术。电除尘器最佳运行工况为流场流速1.0m/s,颗粒数密度体积分数为1.4%,玉米秸秆/无烟煤混烧比为10%,对后续的电除尘器改造及燃料选型具有十分重要的意义。
[Abstract]:China is faced with the dual challenge of energy crisis and environmental pollution, so it is an important way to develop new energy part instead of coal as the optimization of our country's energy reform. China belongs to the big agricultural power, and the biomass energy source is used as a rich and clean renewable energy source to replace some coal, and at the same time, due to the excessive fine particles discharged from the coal to the atmosphere, the present stage of our country, as a serious haze, The emission of fine particles poses a great threat to the living environment of human beings, so the interaction of the fine particles of the graduate material and the coal mixed ash in the electric dust collector to realize the emission reduction of the tail fine particles is essential in the development of a new energy source for the coal-fired power station, This is very important for exploring the optimal biomass energy sources that can be used in place of coal. The fuel selected in this paper is the common biomass fuel, corn straw and anthracite, and first, the corn straw is crushed and then mixed with anthracite according to the ratio of 0, 10%, 15%, 20% and 100%, respectively, and then the mixture is burnt to form a series of mixed ash. The physical and chemical properties (such as the true density and the particle size distribution) of this series of ash mixed ash were studied by the experiment, and the interaction of the mixed ash in the dust collector was prepared. The experimental results show that with the increase of the mixing ratio of the biomass corn straw and the anthracite, the true density of the mixed ash shows a decreasing tendency. At the same time, due to the mixed combustion of the corn straw and the anthracite, the grain size distribution of the corn straw is changed with the pure anthracite ash or the pure corn straw ash, but the change is not obvious, and the peak value of the particle size distribution is the same or close. Secondly, in this paper, three kinds of agglomeration mechanism (thermal agglomeration, turbulent agglomeration and electroreunification) inside the electric dust collector were simulated, and the aggregation kernel function under different agglomeration mechanism was first determined according to the particle size. It is known from the three aggregate core functions that the thermal agglomeration effect is related to the difference of the particle size of the two particles, the greater the difference, the greater the thermal agglomeration nuclear function, and the effect of the thermal agglomeration on the sub-micron particles is superior to that of the micron-sized particles. The effect of turbulent agglomeration is related to the particle size of the particles, the larger the particle size, the better the agglomeration effect, the agglomeration of the turbulent flow to the micron-sized particles, and the effect is better than the sub-micron-sized particles. The larger the particle size of the particles, the more the particle size of the particles, the more the charged amount of the particles, the more the electrical agglomeration, the more obvious the agglomeration of the micron-sized particles and the sub-micron-sized particles. Finally, the interaction between the biomass and the coal ash in the electrostatic precipitator was simulated by Fluent software after the function of the aggregation kernel was determined. First, different cluster kernel function programs are introduced into the software by the self-contained custom function function (UDF), and then the particle swarm optimization model (PBM) is used to couple with the Euler-Euler double fluid model, and the traditional partition algorithm is used for solving the problem. The results show that when the flow velocity of the flow field is 1. 0m/ s, the volume fraction of the particles is 1. 4%, the thermal agglomeration effect is the best, and the effect of the thermal agglomeration is the best when the mixing ratio of the corn straw and the anthracite is 10%; when the flow velocity of the flow field is 1. 5m/ s, the volume fraction of the particles is 1. 4%, the turbulent agglomeration effect is the best; When the flow velocity of the flow field is 1. 0m/ s, the volume fraction of the particles is 1. 4%, the effect of the electric agglomeration is the best, and the effect of the electric agglomeration is the best when the mixing ratio of the corn straw and the anthracite is 10%. The agglomeration of the particles in the electric dust collector is mainly composed of the electric agglomeration, the thermal agglomeration and the turbulent re-agglomeration as the auxiliary, which play a very important role in the agglomeration of the micron-sized particles. Therefore, the new technology of agglomeration and emission reduction of ultra-fine particles should be developed with special attention to the technology of electric agglomeration, heat-agglomeration and the technology of turbulent agglomeration. The optimum operating condition of the electric dust collector is the flow field flow rate of 1. 0m/ s, the volume fraction of the particle number density is 1.4%, and the mixed burning ratio of the corn straw/ anthracite is 10%, which is of great significance for the subsequent improvement of the electric dust collector and the selection of the fuel.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701
[Abstract]:China is faced with the dual challenge of energy crisis and environmental pollution, so it is an important way to develop new energy part instead of coal as the optimization of our country's energy reform. China belongs to the big agricultural power, and the biomass energy source is used as a rich and clean renewable energy source to replace some coal, and at the same time, due to the excessive fine particles discharged from the coal to the atmosphere, the present stage of our country, as a serious haze, The emission of fine particles poses a great threat to the living environment of human beings, so the interaction of the fine particles of the graduate material and the coal mixed ash in the electric dust collector to realize the emission reduction of the tail fine particles is essential in the development of a new energy source for the coal-fired power station, This is very important for exploring the optimal biomass energy sources that can be used in place of coal. The fuel selected in this paper is the common biomass fuel, corn straw and anthracite, and first, the corn straw is crushed and then mixed with anthracite according to the ratio of 0, 10%, 15%, 20% and 100%, respectively, and then the mixture is burnt to form a series of mixed ash. The physical and chemical properties (such as the true density and the particle size distribution) of this series of ash mixed ash were studied by the experiment, and the interaction of the mixed ash in the dust collector was prepared. The experimental results show that with the increase of the mixing ratio of the biomass corn straw and the anthracite, the true density of the mixed ash shows a decreasing tendency. At the same time, due to the mixed combustion of the corn straw and the anthracite, the grain size distribution of the corn straw is changed with the pure anthracite ash or the pure corn straw ash, but the change is not obvious, and the peak value of the particle size distribution is the same or close. Secondly, in this paper, three kinds of agglomeration mechanism (thermal agglomeration, turbulent agglomeration and electroreunification) inside the electric dust collector were simulated, and the aggregation kernel function under different agglomeration mechanism was first determined according to the particle size. It is known from the three aggregate core functions that the thermal agglomeration effect is related to the difference of the particle size of the two particles, the greater the difference, the greater the thermal agglomeration nuclear function, and the effect of the thermal agglomeration on the sub-micron particles is superior to that of the micron-sized particles. The effect of turbulent agglomeration is related to the particle size of the particles, the larger the particle size, the better the agglomeration effect, the agglomeration of the turbulent flow to the micron-sized particles, and the effect is better than the sub-micron-sized particles. The larger the particle size of the particles, the more the particle size of the particles, the more the charged amount of the particles, the more the electrical agglomeration, the more obvious the agglomeration of the micron-sized particles and the sub-micron-sized particles. Finally, the interaction between the biomass and the coal ash in the electrostatic precipitator was simulated by Fluent software after the function of the aggregation kernel was determined. First, different cluster kernel function programs are introduced into the software by the self-contained custom function function (UDF), and then the particle swarm optimization model (PBM) is used to couple with the Euler-Euler double fluid model, and the traditional partition algorithm is used for solving the problem. The results show that when the flow velocity of the flow field is 1. 0m/ s, the volume fraction of the particles is 1. 4%, the thermal agglomeration effect is the best, and the effect of the thermal agglomeration is the best when the mixing ratio of the corn straw and the anthracite is 10%; when the flow velocity of the flow field is 1. 5m/ s, the volume fraction of the particles is 1. 4%, the turbulent agglomeration effect is the best; When the flow velocity of the flow field is 1. 0m/ s, the volume fraction of the particles is 1. 4%, the effect of the electric agglomeration is the best, and the effect of the electric agglomeration is the best when the mixing ratio of the corn straw and the anthracite is 10%. The agglomeration of the particles in the electric dust collector is mainly composed of the electric agglomeration, the thermal agglomeration and the turbulent re-agglomeration as the auxiliary, which play a very important role in the agglomeration of the micron-sized particles. Therefore, the new technology of agglomeration and emission reduction of ultra-fine particles should be developed with special attention to the technology of electric agglomeration, heat-agglomeration and the technology of turbulent agglomeration. The optimum operating condition of the electric dust collector is the flow field flow rate of 1. 0m/ s, the volume fraction of the particle number density is 1.4%, and the mixed burning ratio of the corn straw/ anthracite is 10%, which is of great significance for the subsequent improvement of the electric dust collector and the selection of the fuel.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701
【参考文献】
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