【作者】 邹岸林；

【导师】 刘焕彬；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2011， 硕士

【摘要】 造纸行业是一个需要大量木材作为原料的传统产业。大量木料的使用给环境保护和可持续发展带来巨大的压力。因此废纸的二次利用成为适应当前经济发展的最佳方式。据统计废纸浆已经成为我国造纸的主要原材料,因此,使用好废纸浆,将其功效发挥到最大值对经济和社会的发展有着重要的意义,同时对环境的保护和资源的合理利用也有着举足轻重的意义。废纸浆的利用过程中,对于胶黏物的控制和处理一直以来是个难题,同时也是各个研究机构的重点探讨对象。现今阶段,处理胶黏物的有物理、化学和生物三种技术手段,其中最重要的处理方式便是热分散。热分散一直是科研的重点和热点,深入了解热分散的发生过程,胶黏物颗粒的分裂、分散过程和运动的轨迹,对于提高热分散的质量有重大促进作用。热分散机理的明朗化可以为热分散工艺的改进提供方向性的指导和技术上的支持。九十年代以来,CCD成像技术得到了飞速的发展。而高速摄像机则是在CCD成像技术上发展起来的高速连续采集图像的设备。近年来随着CCD技术和计算机技术的进一步成熟,各国研制的高速摄像机的速度也被不断的刷新。自八十年代高速摄像技术问世,速度达到2000fps,到二十世纪初,研究的成果是速度已经达到30000fps以上。到目前为止,国内有水下高速摄像系统在宜昌研制成功,最高拍摄速度达到每秒10万张图片。美国Phantom公司的高速摄像设备已经达到200万fps。高速摄像技术的发展为科研带来了巨大的促进与影响。本论文的核心就是采用高速摄像技术对废纸浆热分散过程进行可视化的研究,通过拍摄来获得热分散的直观实验数据,经过分析和处理,进一步指导理论发展和实践应用。主要的研究内容包括:(1)开发了一个适合可视化研究热分散过程的实验装置。该实验装置主要由高速摄像机、热分散机、透明有机玻璃膜片、变频器、光源等部分组成。(2)通过高速摄像机对有机磨片内部发生的变化进行拍摄记录,清楚观察到胶黏物颗粒由大到小的分裂过程,运动轨迹。(3)通过染色示踪法对胶黏物颗粒进行识别。把混在纸浆中的胶黏物颗粒进行染色,使之与浆料的颜色明亮程度有较大区别,从而与纸浆区分开来。有了示踪胶黏物,使得高速相机拍摄捕捉其运动轨迹成为可能。(4)以MATLAB为平台,对所拍摄的图片进行去噪、滤波等,从而实现实验图像的视觉优化。(5)对胶黏物颗粒在热分散过程中的运动轨迹进行描述。通过分析热分散过程中发生各种现象的原因,并通过对实验现象的提炼和综合得出胶黏物颗粒在盘片之间被撕裂分散的过程和运动轨迹。通过推理和实验现象的佐证得出胶黏物颗粒可能运动轨迹。通过图示的方式,描述了某胶黏物颗粒的整个被分散的过程和运动轨迹。通过本论文的工作,得到如下结论:(1)胶黏物颗粒被撕裂和分散的方式大概有三种情况:第一种是在飞速旋转的动齿与静止的静齿交错时被切断。在动静齿交错处,会出现层流剪切现象,由于动静交错处的几乎不可压缩使得浆料被高速剪切、摩擦,进而被压扁、撕裂;第二种是在两个盘片之间形成的纤维垫层内部发生内摩擦效应使胶黏物颗粒被撕裂和分散;第三种是在动盘齿和静盘齿间隙中的浆流在动盘飞速旋转后形成湍流和漩涡是胶黏物颗粒破裂进而分散。(2)静盘齿间隙会发生射流、回流等现象,进一步会形成全面的湍流现象。实验可以观察到在动齿飞速运动中,浆料流入静盘齿间隙的过程实际是一个快速的减速过程,不管是纤维团聚体还是胶黏物颗粒在飞射入静盘齿间隙时,都会迅速减速,这个减速的过程就必然形成射流现象。射流的继续进行会使静齿间隙处空出空穴进而形成卷吸,再带动已经在静齿间隙的浆料形成回流。最后整个静齿间隙会产生连续的全面湍流现象。(3)动静盘之间运行的浆料并不是一直充满着整个盘面,而是在不同的时间和不同的区域会形成大小不一的空穴,形成空穴现象。(4)胶黏物颗粒分散过程的运动轨迹是一组连续的有规律可循的发散的曲线。(5)通过MATLAB进行胶黏物颗粒的识别,并对其数目和面积进行统计,得出胶黏物颗粒的分布规律。从而用数字直观证明了热分散不仅可以细化胶黏物颗粒,还可以使其更加均匀的分散在浆料中。更多还原

【Abstract】 Paper industry is one of traditional industries which needs a lot of wood as raw material. The usage of large amount shows enormous pressure to the environmental protection and sustainable development . Therefore, secondary use of waste paper is the best way to adapt to current economic development. According to statistics, China’s paper pulp has become the main raw material, therefore, making good use of waste paper pulp will be significant to economy and social development , meanwhile, it will be a big contribution for the environment protection and rational use of resources . In the process of using waste paper pulp, controlling stickies has always been a problem, however, it is also a focus of various research institutions. Now, there are three kinds of methods to control stickies. They are physical way, chemical way and biological way. The most important treatment is heat dispersion. Heat dispersion has been the focus of scientific research as a hot spot. To have a perfect understanding of the dispersion process and the movement trajectory of stickies is significant. Clarified the mechanism of heat dispersion can improve heat dispersion technology and provide directional guidance and technical support.Since the nineties, CCD imaging technology has been developed rapidly. The high-speed camera is a technology developed from the high-speed continuous image acquisition devices. Recent years,the CCD technology and computer technology is much more advanced, and the speed of the high-speed camera was constantly refreshed. Since eighties, the speed of high-speed video camera is 2000fps. But in the early twentieth century, the speed had reached 30,000fps or more. Up to now, there are underwater high-speed camera system which was successfully developed in Yichang and the maximum recording speed is about100 000 fps. U.S. Phantom’s high-speed camera has reached 1.4 million fps. The development of high-speed photography technology has brought tremendous promotion and impact to scientific research.The core of this thesis is to use the high-speed camera to record the process of heat dispersion. And then, after get the experimental data and a series of analysis, the results can be the guidance of further theoretical development and practical application. The main contents include: (1) Developed a set of experimental apparatus which can be used to do some visual research on heat dispersion. The experimental apparatus includes: high-speed cameras, disperser, transparent plexiglass discs, transducer, light source and other components.(2) The changes in the organic discs are recorded by the high-speed. It is clear to see the process of stickies been devided from big to small particles. (3) The stickies were indentified by different color compared with the pulp. Dye the stickies with black pigment. It is easy to distinguish the black stickies from white pulp. In this way, recording the trajectory of stickies became possible.(4) Use MATLAB to optimize the visual quality of the images taken in the experiment. Especially, use the denoising, filtering founction to do the optimization.(5) Described the trajectory of a small piece of stickes in the heat dispersion system. By analyzing the heat dispersion phenomena and according to the theoretical basis, it is easy to get the common trajectory of stickies. Described the trajectory of stickies in the heat dispersion process by way of icons.Through the work of this paper, the following are conclusions:(1) Stickies are torn and scattered in three main ways: The first is being cut off by the rapid rotation of the moving teeth and the static gear teeth. Staggered at the tooth movement, there will be laminar shear phenomenon. Due to the gap beteewn the teeth is quite narrow, the pulp in the gap is incompressible and there is a series of high shear, friction, and crushing, tearing. The second is the internal friction effect happened in the fiber cushion between static and dynamic teeth. The internal friction effect can tear apart the stickies. The third is the rotating vortex in the static and dynamic teeth gap which can disperse stickies into small particles.(2) The jet and Cyclotron flow occur in the static and dynamic teeth gap. In the experiment , it can be observed that the rapid moving stickies hit the static teeth and then is in a process of rapid deceleration. Regardless of fiber aggregates or particles, this kind of phenomenon happens in the static and dynamic teeth gap. Finally, the backlash will produce a continuous full pulp turbulence in the static and dynamic teeth gap. (3) Between static and dynamic disks, the pulp is not always filled with the gap. And in different areas there will form a series of holes of different sizes, called cavitation.(4) The trajectory of particle dispersion process is a pattern of continuous divergence curves.(5) It is easy to get the statistic numbers of the size and amount of the stickies by MATLAB recognition system. The statistic data can prove not only the stickies can be refined but also it will disperse in the pulp homogeneous.更多还原