潮湿煤炭变振幅等厚弹性深度筛分机理研究

发布时间：2018-04-22 19:38

本文选题：等厚筛分 + 弹性筛分　；参考：《中国矿业大学》2017年博士论文

【摘要】：煤炭是我国的主要一次能源,选煤是实现煤炭高效清洁利用和可持续发展的基础和前提,是洁净煤技术最经济有效的方法,筛分作业是选煤工艺的关键环节。采用传统等振幅刚性筛分方法进行潮湿煤炭干法深度分级时,入料端物料堆积、筛面堵孔严重、分级效果差、筛分作业难以顺利进行,难以满足现代大型选煤厂高效集约化的生产要求。为解决上述问题,本文将变振幅等厚筛分方法与多自由度弹性筛分方法相结合,提出变振幅等厚弹性筛分方法,优化筛上料群分布,提高筛面的利用率,强化粘湿煤炭的松散与分层,消除筛面的堵孔,从而实现潮湿煤炭的高效干法深度筛分。通过理论分析建立了大跨距变振幅等厚筛动力学模型,基于多自由度振动理论建立了质心运动的三自由度振动微分方程,得到了质心和筛体任意位置的位移方程式。通过振动测试分析了大跨距变振幅等厚筛不同运行阶段运动学特性及稳态运行时沿料流方向筛体不同区域的空间运动轨迹。振动筛启动和停机阶段出现较大振动和摆动;过渡运行阶段,出现拍振现象,振幅逐渐降低至工作振幅;稳态运行时筛体各区域的运动轨迹均为椭圆,自入料端至出料端,平行筛面方向振幅差异较小,垂直筛面方向振幅逐渐减小,椭圆长轴与平行筛面方向的夹角逐渐减小。采用大跨度不平衡激振方法可以实现沿料流方向筛面振幅的递减,且随激振力系数、激振梁相对跨距增大,筛体各区域平行筛面方向振幅均逐渐增大,垂直筛面方向入料端振幅逐渐增大,出料端振幅逐渐减小,且两者差异逐渐增大。基于高速摄像及图片分析技术研究了变振幅等厚筛筛面不同区域颗粒运动学特性及料群分布特性,揭示了变振幅等厚筛分形成机理:入料端振动强度大,强化了料群颗粒的松散和运移,料群在筛面上迅速铺展,出料端振动强度小,颗粒运移速度变慢,料群停留时间增长,因而使得筛上料层趋于等厚。提出了多段采样分析方法,分析了不同粒级物料在筛面各区域的透筛规律,揭示了变振幅等厚筛分强化料群分级机制。激振力系数、激振梁相对跨距的变化引起了料群筛分时间、运移速度及透筛分布的改变,促使了筛上料层分布的时空演变:入厚出薄→近似等厚→入薄出厚,进而影响了物料的筛分效果。基于上述研究,通过对变振幅刚性筛分颗粒运移速度及筛上料层分布进行调控,可以实现低水分煤炭的变振幅等厚高效深度筛分。设计了刚柔耦合弹性杆筛面,分析了简谐位移激励下刚柔耦合弹性杆运动学特性,给出了弹性管位移幅值表达式及料流方向筛孔尺寸值域。借助高速摄像捕捉分析了弹性筛分过程中刚柔耦合弹性杆运动行为、潮湿煤炭料群空间分布及行为特征,进而揭示了堵孔消除机制:刚性杆与侧板圆孔及弹性管的接触碰撞引起了弹性管加速度幅值统计平均值的增大,强化了料群的松散,使得粘附的细粒物料从粗颗粒表面脱除;弹性管的空间旋转对粘附成团颗粒及覆盖膜产生剪切作用;相邻弹性管空间位置的改变及其弹性变形,使得筛孔尺寸值产生类周期性波动,加之弹性管对与其接触的物料作用力方向随机,使得成团颗粒及覆盖膜破裂、卡堵颗粒从筛孔脱离。研究了工艺参数及入料特性对等振幅刚柔耦合弹性杆筛6 mm分级效果的影响规律,确定了操作参数的最佳取值范围。提出了变振幅等厚弹性筛分方法,采用单因素试验研究了激振力系数、激振梁相对跨距对变振幅等厚弹性筛分效果的影响并确定相应的最佳因素水平。通过分析选取了对变振幅等厚弹性筛分影响显著的试验因素,采用多因素响应面筛分试验分析了各因素对筛分效果的影响显著性及交互作用,建立了筛分效率与上述因素之间的关联模型。根据关联模型分析确定了最佳操作条件,对内蒙古鄂尔多斯潮湿煤炭进行了6 mm变振幅等厚弹性筛分试验,筛分效率为87.79%,总错配物含量为6.77%,筛分效率试验值与模型预测值接近,验证了关联模型预测结果的准确性,表明采用变振幅等厚弹性筛分技术可以实现潮湿煤炭的高效干法深度筛分。
[Abstract]:Coal is the primary energy of our country. Coal preparation is the basis and prerequisite for efficient clean utilization and sustainable development of coal. It is the most economical and effective method of clean coal technology. Screening operation is the key link of coal preparation process. In order to solve the problems mentioned above, the variable amplitude equal thickness sieving method and the multi degree of freedom elastic sieving method are combined to solve the above problems. The variable amplitude and equal thickness elastic screening method is proposed to optimize the distribution of the material on the sieve. In order to improve the utilization of the screen surface, strengthen the loosening and stratification of the sticky coal and eliminate the plugging of the sieve surface, the high efficient dry method of sieving the wet coal is realized. The dynamic model of the thick sieves with large span and variable amplitude is established by theoretical analysis. Based on the theory of multi degree of freedom vibration, the three degree of freedom vibration differential equation of the mass center motion is established. The displacement equations of the centroid and the sieves at any position are analyzed. By the vibration test, the kinematic characteristics of the different stages of the large span and variable amplitude sieves and the different regions of the sieves in the direction of the steady state are analyzed. The vibration and swing of the sieves in the starting and stopping stages of the vibrating screen are larger than that in the stage of the starting and stopping of the vibrating screen. The amplitude of the amplitude gradually decreases to the working amplitude, and the motion trajectory of the sieves in the steady state is ellipse, from the end to the discharge end, the amplitude of the parallel screen direction is smaller, the amplitude of the vertical screen direction decreases gradually, and the angle between the elliptical long axis and the direction of the parallel screen gradually decreases. The method of large span unbalance excitation can be realized. At present, the amplitude of the sieve surface is decreasing along the direction of the material flow, and with the excitation force coefficient, the relative span of the excitation beam increases, the amplitude of the parallel sieve surface in each area of the sieves increases gradually, the amplitude of the vertical sieve surface increases gradually, the amplitude of the discharge end decreases gradually, and the difference of the two sides gradually increases. The kinematic characteristics and distribution characteristics of the particles in different regions of the sieves and sieves are revealed. The vibration intensity of the variable amplitude is large, and the loosening and migration of the particles are strengthened. The material group is spread rapidly on the sieve surface, the vibration intensity of the discharge end is small, the speed of the grain migration is slow, and the residence time of the material group is increased, thus the residence time of the material group is increased. A multi section sampling analysis method was put forward, and the screening law of different grain grade materials in each area of the screen was analyzed. The classification mechanism of the variable amplitude and equal thickness sieving reinforcement group was revealed. The excitation coefficient, the change of the relative span of the excited beam caused the change of the screening time, the movement speed and the distribution of the screen. The space-time evolution of the distribution of the material layer on the screen: the thickness of the thick, approximately equal thickness and thinning out of the thickness, and then the screening effect of the material. Based on the above research, the variable amplitude and high efficiency depth sieving of the variable amplitude and equal thickness of the low moisture coal can be realized by adjusting the velocity of the particle movement of the variable amplitude rigid screen and the distribution of the material layer on the sieve. The kinematic characteristics of rigid flexible coupling elastic rod under simple harmonic displacement are analyzed, and the displacement amplitude expression of elastic tube and the size range of sieve hole size in the direction of material flow are given. The motion behavior of rigid flexible coupling elastic rod in the process of elastic screening, the spatial distribution and behavior characteristics of damp coal material group are analyzed with the help of high speed camera. The mechanism of plugging removal is revealed: the contact collision between the rigid rod and the circular hole and the elastic tube causes the increase of the statistical average of the acceleration amplitude of the elastic tube, the loosening of the material group and the removal of the adhesive particles from the surface of the coarse particles; the space rotation of the elastic tube produces the shear effect on the adherent particles and the covering film; the adjacent projectile is adjacent to the elastic tube. The change of the space position of the tube and its elastic deformation make the size of the sieve size fluctuate periodically, and the force direction of the material that the elastic tube is exposed to is random, which makes the pellets and the covering film broken and the plugging particles are separated from the sieve hole. The 6 mm points of the process parameters and the feeding characteristics are studied. The optimal range of the effect of the level effect is determined. The variable amplitude equal thickness elastic sieving method is put forward. The effect of the excitation force coefficient, the relative span of the excited beam on the variable amplitude equal thickness elastic sieving effect and the corresponding optimum factor level are studied by single factor test. The variable amplitude equal thickness is selected by analysis. The effect of multiple factor response surface screening test was used to analyze the impact significance and interaction of various factors on the screening effect. The correlation model between the screening efficiency and the factors mentioned above was established. The optimum operating strip was determined according to the correlation model, and 6 wet coal in Ordos, Inner Mongolia, was carried out. The MM variable amplitude and equal thickness elastic screening test, the screening efficiency is 87.79%, the total mismatch content is 6.77%, the sieving efficiency test value is close to the model prediction value, which verifies the accuracy of the prediction results of the correlation model. It shows that the variable amplitude and equal thickness elastic sieving technology can be used to achieve the efficient dry method of sieving wet coal carbon.

【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TD94

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