【作者】 王春华；

【导师】 陈海耿； 陈文仲；

【作者基本信息】 东北大学 ， 热能工程， 2009， 博士

【摘要】 炭素煅烧回转窑是对炭素材料(主要是石油焦)进行煅烧的回转窑圆筒设备,其产品用以满足铝电解槽用阳极成型前的要求。炭素回转窑的应用,在我国起步较晚,距今仅有近30年的生产历史,与国外同类设备相比,无论在产能、能耗指标,还是煅烧焦质量及设备使用寿命等方面都存在一定的差距。因此,加快其生产工艺的研究和技术改造步伐,改善煅后焦质量,提高回转窑产能成为科技工作者急需解决的问题。本文即以该主题为中心展开研究。以河南某生产回转窑的热工测试结果和煅烧原料石油焦的物性参数测试结果为依据,本文编制了物料平衡表和热平衡表,了解了该窑的物料烧损和能量利用状况。同时利用模拟软件Fluent和Matlab分别对回转窑内气体空间和料层进行了数值模拟,详细阐述了回转窑内流场、温度场和组分浓度场的分布,着重研究了二、三次风管供风口位置与风量和窑内衬增设的翻料装置结构对窑内热工状况的影响。本文运用力矩守恒原理和物料运动学规律推导出适于炭素回转窑工业生产优先选择的物料运动形式——滚落发生的条件。由导出条件可知,通过改变物料与窑内壁的摩擦系数和回转窑转速的方法可以实现物料的滚落运动。对生产回转窑和自行设计制造的实验回转窑而言,当窑内壁摩擦系数满足滚落发生条件时,回转窑转速分别在1.1～3.7rpm和1.0～8.0 rpm范围内,可以实现并维持物料的滚落运动。以此运动形式为基础,借助前人建立的直筒窑料层厚度的数学模型,导出了直筒窑内物料停留时间的计算式。改变直筒窑料层厚度数学模型形式,导出了变径窑内物料停留时间的计算式。计算式中综合考虑了窑内径、窑长、窑头挡料圈高度、窑倾角、窑转速、物料体积流率、物料安息角、物料颗粒粒径等多种因素,具有一定的实用性。本文对自行设计建立的回转窑实验装置进行了热态实验,研究了回转窑在干燥期、烘烤期和煅烧期中,窑内的温度分布,及其与加热时间之间的关系。实验结果表明：窑内温度随着加热时间的延长而增加,窑头、窑尾两端附近温度变化剧烈,窑体中部区域温度变化平缓。文中还对实验装置进行了冷态实验,研究了回转窑转速、倾角、内径、内衬结构、窑尾挡料圈等参数对窑产能和物料停留时间的影响。实验结果表明：物料在窑内的停留时间分布近似正态分布。随着窑转速、窑倾角的增加,回转窑的产能增加,物料停留时间缩短。窑尾安装挡料圈可以有效提高窑产能,但其对物料停留时间的影响较为复杂,当转速低于2.0 rpm时,物料停留时间随着窑尾挡料圈高度的增加而延长；当转速超过2.0rpm时,物料停留时间随着窑尾挡料圈高度的增加反而缩短。当回转窑倾角固定时,物料停留时间与物料质量流率(即窑产能)的乘积与单位转速内物料质量流率近似成线性关系。将导出的直筒窑和变径窑内物料停留时间的计算值与实验窑的测试值分别进行了比较。结果表明,两者计算值与实验值比较吻合,而且计算中不需要引入修正系数。本文最后综合实验测试与数值模拟结果,提出了建议与大家商讨,以达到稳定窑况、改善煅后焦质量、增产节能降耗的目的。更多还原

【Abstract】 The carbon rotary kiln is a kind of rotary cylindrical equipment for aluminum industrial calcination of carbon product such as petroleum coke. It has been used to calcinate petroleum coke only for nearly 30 years in China. As a result, there are wide differences between home and abroad in kiln output, energy consumption, calcining quality and kiln working life. Therefore, how to improve calcining quality and increase kiln output are becoming more urgent questions for the researchers. Then the paper is around these questions to study.In the paper, thermal measurements are carried out on a carbon rotary kiln in Henan province and physical parameters about petroleum coke are tested. Then, we calculate the material balance and the thermal balance. From the calculated results, we can know the carbon burning loss and utilization of energy. Meanwhile, the numerical simulations are conducted on gas and solid areas of the kiln using Fluent and Matlab softwares. It illustrates explicitly the flow field, temperature filed and compositional concentration field. And then the paper focuses on the impacts of the supply rate and positions of the secondary air and tertiary air and the kiln lining with turn-down rig structure on the kiln working condition.In the paper, solids movements are further researched. For practical engineering, the rolling motion is often chosen as an ideal design work condition. Here, characteristics of rolling motion are made simple analysis and its necessary conditions to occur are deduced. From the induced conditions, rolling motion happens by adjusting the kiln inner wall friction and the rotation speed. As the rotation speed ranges from 1.1 to 3.7 rpm for practical kiln and from 1.0 to 8.0 rpm for our experimental kiln, the solids mode of motion is rolling. According to the previous numerical model for predicting the depth of the solid bed, formula about the particle mean residence time of the straight kiln is deduced. Changing the numerical model for the solid bed depth of the straight kiln, formula about the particle mean residence time of the variable diameter kiln is got.The formulae calculate the residence time as a function of the kiln radius, kiln length, discharge dam height, kiln inclination, rotation speed, material volumetric flow rate, angle of repose of the solids and particle mean diameter.A laboratory rotary kiln is set up and hot experiments are carried on it in this work. The experimental results show that, kiln temperature increases with the calcination time. Kiln temperature changes significantly at around the kiln inlet and outlet and gently at the middle part of the kiln. The influences of operational and structural parameters on the mean residence time of solids (MRT) and the kiln output are also presented on the experimental rotary kiln. Experimental results show that the increase of rotation speed and kiln slope reduces MRT and increases kiln output. Also, kiln output increases with increasing charge dam height. MRT increases when the rotation speed is lower than 2.0 rpm but decreases when the rotation speed is higher than 2.0 rpm with increasing dam height. The product of MRT and mass flow rate (i.e. kiln output) increases approximately linearly with the mass flow rate per kiln rotation at the same kiln slope. Results of formulae about MRT calculation are compared with measurements. The comparison shows that, calculated results of the residence time of solids agree well with measurements. No fitting parameter is necessary.Finally, the paper summarizes the experiment results and simulated results and makes some recommendations so as to accomplish the aim of calcining quality improvement, kiln output increment and energy reduction.更多还原