【作者】 黄灿军；

【导师】 瞿金平；

【作者基本信息】 华南理工大学 ， 机械设计及理论， 2013， 博士

【摘要】 利用废弃生物质中的植物纤维与塑料制备复合材料时，通常会对植物纤维进行预处理。在植物纤维各种预处理方法中，由于蒸汽爆破预处理不会对环境造成任何破坏，且生产率高，在各种方法中具有突出的优势。目前国内对植物纤维改性多采用间歇式蒸汽爆破技术，而间歇式蒸汽爆破技术的产量低，且需要附加蒸汽设备，使整机体积庞大，成本较高，从而限制了其广泛应用，因此有必要对连续式闪爆设备及其理论展开研究。单螺杆连续式闪爆设备的物料输送过程与传统单螺杆挤出机的固体输送极为相似，但单螺杆连续式闪爆设备的压缩比比单螺杆挤出机压缩比大很多。因此对于单螺杆连续式闪爆设备而言，物料不再是不可压缩，螺槽也不是展开成传统的平直螺槽，而是考虑物料的密度和速度均为变化的基础上，建立楔形螺槽的物理模型，再借鉴传统单螺杆挤出机的固体输送理论，对单螺杆连续式闪爆设备中固体生物质材料进行运动分析和受力分析，建立数学模型，进一步分析物料在单螺杆连续式闪爆设备中建压和温度升高的过程。口模的设计尺寸对闪爆效果也有较大影响，同样建立了口模的环形物料输送物理模型，并对环形物料进行运动分析和受力分析，建立压力数学模型，进一步分析口模水平段长度对闪爆压力的影响规律。另外通过摩擦力做功的原理建立了物料沿螺槽方向的温度数学模型，分析了喂料量、主轴转速等对闪爆温度的影响规律。在理论分析基础上，自行设计了单螺杆连续式闪爆设备，并在该设备上附加背压和温度测试模块，利用背压和旋转轴上靠近口模处温度近似观察闪爆压力和温度的变化规律。在自行设计的单螺杆连续式闪爆设备上开展了各种实验研究，由于直接测量口模处压力非常困难，实验中利用螺杆背压近似代替闪爆压力，以观察闪爆压力的变化规律。虽然通过螺杆背压可以近似反映闪爆压力的变化，但背压测量装置结构复杂，也并非闪爆设备所必需的附加装置，因此研究了主机电流与螺杆背压之间的关系，发现二者有很好一致性，则可以通过主机电流来反映闪爆压力的变化。实验中还研究了闪爆温度与物料闪爆前后含水率差值之间的关系，发现二者有很好一致性，则可以用含水率差值来反映闪爆温度的变化。通过更换具有不同直径和水平段长度的口模，测试不同尺寸条件下的闪爆压力，找出了口模尺寸对闪爆压力的影响规律。最后通过实验研究了喂料量和主轴转速等工艺参数对闪爆压力和温度的影响。由于单螺杆连续式闪爆设备物料的输送能力差、产量低、混合能力差、自清洁性不好等缺点，有必要进一步开展输送能力强、产量高、混合能力强、自清洁性好的三螺杆连续式闪爆设备的研究。根据三螺杆连续式闪爆设备输送能力强的特点，建立了机筒内物料的正位移输送模型，计算出混合段、输送段、增压段等各段的―C‖形小室的体积，利用体积压缩建立压力数学模型，分析了物料在三螺杆连续式闪爆设备中建压的过程，并进一步求得该闪爆设备的产量理论计算公式。自行设计了三螺杆连续式闪爆设备，并专门设计了进料连续、均匀、喂料量可控的生物质材料计量进料装置和在线快速补水装置。在自行设计的三螺杆连续式闪爆设备上开展一系列实验，首先研究了闪爆温度与物料闪爆前后的含水率差值之间的关系，同样发现闪爆温度与含水率差值有很好的一致性；接着研究了喂料量、物料初始含水率和粒径大小等工艺参数对闪爆压力和温度的影响。在前章闪爆设备产量的理论分析基础上，进行了产量的实验测试，找出了产量与主轴转速间的关系。由于在连续式闪爆设备的压力和温度理论分析中应用到压力与密度关系的经验公式，其中涉及到一个重要参数，即物料参数，因此在最后通过实验求得了物料在常温及160℃时的物料参数，为进一步深入开展三螺杆连续式闪爆设备的理论和实验研究打下基础。通过对自行设计的单螺杆式、三螺杆式连续闪爆设备的研究，首次建立了连续闪爆设备内物料的压力和温度数学模型，揭示了连续闪爆过程机理及其闪爆效果，并预测了该过程中压力与温度的建立规律，与实验结果有较好的一致性。通过实验发现闪爆压力与主机电流、闪爆温度与物料闪爆前后的含水率差值有很好的一致性；口模直径减小和水平段长度增加均会增加闪爆压力，喂料量增加也可以增加闪爆压力，但会降低闪爆温度，主轴转速增加可以闪爆温度升高，但会降低闪爆压力；物料初始含水率越低，以及物料粒径越小，闪爆温度均越高。更多还原

【Abstract】 The plant fiber of waste biomass should be pretreated regularly when it is processed withplastics to make composites. Among variety means of pretreatments, the steam explosion willnot damage anything to the environment, and the pretreatment productivity was high, whichare special advantages among all methods. The plant fiber modification usually adoptedintermittent steam explosion technology in domestic currently, however, the productivity ofwhich is low, and a steam equipment is needed for production. It makes the machine volumehuge, increases the production cost. Accordingly, the application is limited extremely, thus,the exploration on continuous steam explosion equipment and theory is of great significance.It was extremely similar that the solids conveying of single-screw extruder and thematerials conveying of single-screw continuous steam explosion equipment. However, thecompression ratio of the latter was much higher than that of the former. Thereby, for single-screw continuous steam explosion equipment, materials were no longer incompressible, andthe spiral grooves were not the traditional flat ones. Considering the basis that both thedensity and the velocity of materials were varying, a physical model of wedge-shaped spiralgrooves was established; on the other aspect, depending on the solids conveying theory oftraditional single-screw extruder, the movement and the force condition of solid biomassmaterials that processed in the continuous steam explosion equipment were analyzed. Then amathematical model was established, which made it possible to analyze the process ofpressure building and temperature increasing for the materials in the single-screw continuoussteam explosion equipment.It was a huge impact on the steam explosion effect with different designing diedimension. Thereby a physical model was built for the annular materials conveying of the die,and the movement and the force condition was analyzed for the annular materials, a pressuremathematical model was built. Moreover, the influence principle was analyzed for the diehorizontal section length to the steam explosion pressure. Furthermore, a temperaturemathematical model for the materials along the spiral groove direction was built according tothe principle of frictional force acting.Variety of experiments were carried out in the own designed equipment, since it wasrather difficult to measure the die pressure directly, then the steam explosion pressure wassubstituted by the screw backpressure, so that the variation principle for steam explosionpressure can be observed. The relationship between screw backpressure and main electriccurrent was studied, it was found that there was a consistency between them, which meant itcould be used to reflect the variety of the former. Furthermore, the relationship between the steam explosion temperature and the moisture content difference in materials that before andafter steam explosion. It was also found that there was a consistency between them, themoisture content difference could be used to represent the former. Through changing dieswith different diameters and horizontal lengths, different steam explosion pressures weremeasured, the principle was found that how the die sizes effected on steam explosionpressures. Some experiments were carried out to investigate how the parameters of materialvolume and main axis speed influenced the steam explosion pressure and temperature.Disadvantages for single-screw continuous steam explosion equipment performed as:low production, poor self-cleaning property, weak material conveying and mixing capacity. Itwas necessary to study triple-screw continuous steam explosion equipment which wouldovercome those disadvantages above. According to its powerful material conveying capacity,a positive displacement conveying model for the materials in the barrel was established. Itcontained calculating volumes of―C‖type chambers in mixing section, conveying section,pressurized section separately. After that, a mathematical model was built through volumecompression, which was used to analyze the pressure building process in the triple-screwcontinuous steam explosion equipment for the materials, furthermore, the theoreticalcalculating equation for the production of the equipment could be obtained. The triple-screwcontinuous steam explosion equipment was designed by our own. In addition, the online rapidreplenishment device, and the biomass materials metering feeding device, which could feedcontinuously, uniformly, controllable were designed specially.A series of experiments were carried out in the own designed triple-screw continuoussteam explosion equipment, Firstly, the relationship between steam explosion temperature andthe moisture content difference in materials that before and after steam explosion, it wasfound that there was a consistency between them; Moreover, the influence of technologicalparameters on steam explosion pressure and temperature, which contained feeding volume,original moisture content and particle size. Based on the theoretical analysis of equipmentproduction, a real production experiment was carried out, and the relationship that betweenthe production and the main axis speed was found. As the empirical equation related withpressure and density was applied in the theoretical analysis of pressure and temperature in thecontinuous steam explosion equipment, an important parameter was referred to, namely thematerial parameter, it was obtained when the temperature was at25oC and160oC separatelythrough experiments, which was laid a solid foundation for intensive research on theories andexperiments of triple-screw steam explosion equipment. Through the above theoretical analysis, the mathematical model for the pressure andtemperature in the continuous spiral pressurized steam explosion, the approximate analyticalsolution were obtained which contained the pressure, velocity, density and temperature of thematerials along the directions of spiral groove and die; The theoretical calculation formula ofthe production and the approximate analytical solution of the pressure along the direction,which revealed how the equipment do effect to the materials: The pressure and temperature ofthe materials were accumulated to a certain, which were then released through the die. It wascalled the mechanism of steam explosion effect, which provided theoretical guidance for thedesigning of continuous spiral pressurized equipment. It was found in the experiments thatthere was a coincidence in the steam explosion pressure and the main engine current; steamexplosion temperature and the moisture content difference in materials that before and aftersteam explosion. One varying patterns reflected the other; both the diameter decreasing of dieand the length increasing of horizontal section elevated the steam explosion pressure, theincreasing materials feeding volume also elevated the steam explosion pressure, however, itreduced steam explosion temperature, the speed increasing of main axis elevated the steamexplosion temperature, however, it decreased the steam explosion pressure; the lower of theoriginal moisture content, the higher of the steam explosion temperature.更多还原