【作者】 胡建军；

【导师】 沈胜强；

【作者基本信息】 大连理工大学 ， 动力机械及工程， 2008， 博士

【摘要】 本文以发展生物质能资源化利用技术为背景,研究农作物秸秆颗粒燃料冷态压缩成型规律,为生物质固体成型燃料作为可再生能源在替代煤炭燃料方面探索新的途径。本文研究工作属于国家“863”计划项目之子课题“农业废弃物流化床气化过程预处理技术研究”和河南省自然科学基金项目“农业废弃物颗粒燃料冷成型机理研究”的部分内容。主要研究包括:采用电子万能实验机,分别从压缩速度、物料含水率、原料种类、模具长径比、模具开口锥度等五个方面进行了秸秆颗粒冷态压缩成型的实验研究与分析;根据秸秆冷态压缩成型特点,采用大变形塑性理论作为秸秆材料非线性问题的有限元分析基础,利用ANSYS软件对秸秆冷态压缩成型过程进行了计算机模拟,得到了秸秆颗粒冷态压缩成型过程中的应力应变分布图、流动变化图和等效塑性应变图,并进行了不同模具长径比和模具开口锥度等结构参数对压缩成型过程的模拟分析;从生物构造、物理性质、化学性质和力学性质入手,探索出秸秆颗粒冷态压缩成型粘接机制,并通过扫描电子显微镜进行了不同成型条件下的秸秆压缩前后微观结构变化的实验研究;根据环模颗粒成型原理,设计了一套秸秆颗粒冷态压缩成型中试装置,进行了不同物料粒度、含水率、模孔长径比等压缩条件下的颗粒成型率及吨料电耗的试验研究。通过上述研究工作,得出的最佳压缩成型条件和工艺参数具有较好的一致性,为探索秸秆颗粒冷态压缩成型规律提供了科学依据。研究工作取得如下主要结论:(1)当压缩速度取40mm/min、含水率取16%、秸秆原料为小麦秸秆、模具长径比取5.2和模具开口锥度取45°时,压缩成型效果最佳;将压缩成型过程分为松散、过渡、压紧和推移四个阶段,其中松散阶段和压紧阶段的数学模型为线性方程;过渡阶段的数学模型为指数方程;推移阶段根据秸秆原料种类不同,可用单个或n阶Maxwell模型来表示其松弛特性。上述结论为压缩成型条件和工艺参数的选取提供了实验依据。(2)摩擦力和模具锥孔是靠近锥面处的秸秆出现变形滞后现象的主要原因,模具长径比和模具开口锥度的最佳取值与实验结果一致,说明数值模拟与实验研究能够较好地吻合,为模具参数的选取和秸秆成型颗粒燃料的性能控制提供了理论依据。(3)提出了秸秆冷态压缩成型的微观结合模式。在横截面方向上,秸秆组织受到严重破坏,以相互贴合的形式结合:在纵截面方向上,秸秆组织破坏较小,以相互嵌合的形式结合。为探索秸秆冷态压缩成型机理提供了参考依据。(4)当攫取角取45°,模辊直径比取0.585时压缩成型综合效果最好;小麦秸秆的压缩成型效果最好,其次是稻草,玉米秸秆最差;当物料粒度取6mm,含水率取16%,模孔长径比取5.2时,颗粒成型率较高,装置吨料电耗最低,压缩成型效果最好。该结论验证了实验研究、数值模拟和微观结构分析的正确性,表明本文得出的最佳成型条件和工艺参数具有普遍意义,可以用来指导工业化生产的环模颗粒成型机的优化设计。更多还原

【Abstract】 The pellet fuel cold molding discipline of different crops straws is studied detailed in this thesis,under the background of developing biomass utilization technology as a kind of energy resource.It starts a new way for biomass solid pellet fuel to be used as renewable energy substituting for coal.It is listed in a sub project of Chinese National ’863 Project’ "Agriculture Waste FB Gasifying Pretreatment Technology" and the project of the Natural Science Foundation of Henan Province project "Study of Agriculture Waste Cold Molding Mechanism".The main research contents are in the following,experiments are done from five aspects including pressing speed,moisture ratio,variety of the material,length diameter ratio of the die and split taper by universal stuff experimental equipment.According to the feature of straw pellet cold moling,using large deform elastic and plastic theory as the method for finite element computation,it adopts the software ANSYS to simulate the molding process.The stress and strain distribution chart,fluid deform chart and equivalent plastic strain in the molding process are obtained.And simulations on various ratios of length and diameter and split taper are done.Detailed influence on molding is analyzed from four aspects, biology structure,physical property,chemical property and dynamic property.The stick mechanism is obtained.And the micro structure changes are studied by SEM under different molding conditions.According to the molding mechanism,pilot pellet equipment is designed. And a series of experiments on molding rate and electricity consume rate are done under different pressing condition.From the study work above,the optimal molding conditions and technological parameters obtained by different means have good consistency.This provides scientific evidence for the exploration of molding discipline.The main conclusions are in the following:(1)At the condition of speed 40mm/min,moisture ratio 16%,ratio of length and diameter 5.2 and taper 45°with wheat straw,the best results can be obtained.The molding process can be divided into four stages,loose,interim,pressing and lapse.The loose and pressing stages fit linear equations.And the interim stage fits exponential equation.The lapse stage fit Maxwell Model.These conclusions provide evidence for the selection of pressing conditions and parameters.(2)The friction force and the taper are the main reasons why the deforming near the split is delayed.And optimal ratio of length and diameter and split taper are accordant with the experiment results.It’s proved that the simulation fits well with experiment study.This provides theoretical evidence for the selection of die parameter and control of the pellet equipment.(3)The micro connecting mode is put forward from straw cold molding by compression. In the cross section,the structure of the biomass is destroyed seriously and connected by joint form.And in the lengthwise section,little destroy appeared,so they connect by chimeric form. This provides evidence for the exploration of the common regulations on pellet molding.(4)The molding rate is sound under swoop angle 45~0 and ratio of die and roller diameter 0.585.The molding rate of wheat is better than rice straw,the worst is corn straw.The electricity consumption is the lowest under granularity 6mm,moisture ratio 16%,ratio of length and diameter of the die 5.2.This conclusion proves the correctness of the experiment study and computation simulation.And the best molding condition and parameter has universal significance,guiding the design of pellet mill for industry use.更多还原