【作者】 杨旭亮；

【导师】 赵跃民；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2013， 博士

【摘要】 我国煤炭资源与水资源呈逆向分布，水资源短缺问题制约着传统湿法分选技术在干旱缺水地区的应用，大量煤炭未经深度分选直接进入市场造成了严重的资源浪费，这种现状凸显了发展干法选煤技术的重要性和紧迫性。相比已工业化的粗粒煤干法分选技术，细粒煤干法分选尚未有成熟的解决方案。鉴于此，首次将气固流态化领域的密度离析现象引入到细粒煤干法分选研究中，并结合细粒煤颗粒流化特性和分选效果预期，针对性地提出了采用振动流化床促进细粒煤床层形成强化密度离析的流化环境，进而实现细粒煤有效分选。振动能量以布风板强制运动和空气压力波两种主要形式传递给Geldart D类细粒煤气固流态化体系，借助于先进的高速动态图像分析系统研究振动对流化性能的优化机制，发现振动能量的引入有效地破坏了颗粒力链网络，消除了流化死区和气流短路通道，改善了颗粒系统力学特性。同时，振动与气流等引入能量的协同作用促使过剩流化气体在空气压力波的激励下形成规律化的团涌行为，建立了团涌毗邻区气泡追赶兼并的动力学方程和团涌生长机理模型。具有适宜特征尺寸的团涌扰动区为颗粒系统密度离析提供以流体曳力为主导的干扰沉降环境。建立了团涌扰动区高度及团涌上升速度关联式，同时指出团涌发生频率与流化气速无关，频率范围为[3.47Hz,3.85Hz]。强化颗粒密度离析的流化环境要满足两个条件：具有适宜流体力学环境的稀相区，能够实现不同密度颗粒间的有序滑移；稳定的稀相区发生机制，避免已离析的颗粒层间的返混。通过综合分析振动流态化体系的流体力学环境和强化密度离析的流化环境的构成要素，揭示了基于密度离析分离机制的细粒煤振动流态化分选机理。从系统势能变化的角度考察了分选过程，理论计算结果显示分选后颗粒系统总势能较分选前减小约9.3%，说明基于密度离析分离机制的细粒煤振动流态化分选过程具有较强的自发性。根据上述分选机理，在因素试验环节提出灰分离析度的概念来评价表观流化气速、振动强度、床高和流化时间等因素对分选效果的影响。在单因素试验确定了各因素最佳取值范围的基础上，采用Box-Behnken响应曲面法研究了因素间的交互作用，确定了-6+3mm和-3+1mm粒级细粒煤的最佳分选条件，建立了两种煤样灰分离析度的二阶多项式预测模型。分选结果显示间歇式振动流化床分选系统分选-6+3mm和-3+1mm两种粒级细粒煤可能偏差E值分别为0.19~0.225和0.175~0.195。根据实验室研究结果自行设计和建立了连续式振动流化床分选系统，通过引入表征床层输送特性的系数建立了连续式振动流化床分选机的床高分布模型，指出为了保证良好的分选效果，要尽量延长床面近似水平区段的长度。建立了连续式振动流化床分选机的平均输送速度模型，确定振动角最佳取值范围为63°~67°。分选结果显示-3+1mm粒级细粒煤在连续式振动流化床分选系统中分选的可能偏差E值为0.225，并提出采用二段式分选工艺流程提高分选效果。该论文有图101幅，表59个，参考文献156篇。更多还原

【Abstract】 China’s coal resource and water resource has a reverse distribution. The problemof water shortages restricts the applications of wet coal beneficiation technologies indrought regions. A great amount of coal without deep cleaning enters directly to themarket, leading to serious waste of coal resources. The present situation describedabove highlights the significance and urgency of developing dry beneficiationtechnologies of coal. Thus, for the first time, the density segregation phenomenon inthe field of gas-solid fluidization is introduced into the research on fine coal drybeneficiation. In consideration of the fluidization characteristics of fine coal and theanticipation of separation performance, a vibrated fluidized bed is adopted particularlyto foster the formation of fluidization environment that intensifies density segregationwithin the bed of fine coal, leading to an effective fine coal beneficiation performance.The transfer of vibration energy to gas-solid fluidization systems of GeldartD-type fine coal has two main forms: forcible movement of air distributor and airpressure waves. The optimization mechanism of fluidization behavior due to vibrationis studied by using an advanced high-speed dynamic image analysis system and theresults show that the introduction of vibration energy can effectively destroy theparticulate force chains net, eliminate the disfluidized zones and the short-circuitchannel of air flow and improve the mechanical properties of particles system.Meanwhile, the synergistic functions of vibration and fluidizing air promote the excessfluidizing air to form regular slugging behavior under the excitation of air pressurewaves. The dynamical equation of coalescence due to bubble acceleration in theadjacent region of a slug and the mechanism model of slug growth are established. Theslug-disturbed regions with appropriate feature size provide a hindered settlingenvironment determined by the fluid drag force for the density segregation of particlessystem. Correlations of slug-disturbed region height and slug rising velocity areestablished and the occurence frequency of slugs varies between3.47Hz and3.85Hz,which is independent of fluidizing air velocity.Fluidization environment that intensify density segregation should satisfy thefollowing two conditions: having dilute regions with an appropriate environment ofhydromechanics that ensure the slip of particles with different densities and having astable occurrence mechanism of dilute regions that prevent the back-mixing of the segregated particles layers. The mechanism of fine coal beneficiation usingvibrofluidization based on density segregation is revealed by the comprehensiveanalysis of the hydromechanics environment of vibrated fluidized beds and theelements of fluidization environment that intensify density segregation. The separationprocess is studied from the perspective of the system potential energy changes and theresult of theoretical calculations indicates that the total potential energy of theseparated particles system is reduced by approximately9.3%comparing with that ofthe particles system before separation, which indicates that fine coal beneficiationprocess using vibrofludization based on density segregation has strong spontaneity.The concept of ash content segregation degree is proposed during the factorexperiments to evaluate the effects of factors including superficial air velocity,vibration intensity, bed height and fluidizing time on separation performance. Based onthe determination of optimal range of each factor owing to the single factor experiment,the Box-Behnken response surface method is used to study the interactions betweenfactors and determine the optimal separation conditions of-6+3mm and-3+1mm finecoal respectively. In addition, second-order polynomial predictive models areestablished. The separation results show that the probable error E values of-6+3mmand-3+1mm fine coal separated in an intermittent separation system using a vibratedfluidized bed are0.19~0.225and0.175~0.195, respectively.A continuous separation system using a vibrated fluidized bed is designed andestablished by ourselves based on the results of laboratory study. The bed distributionmodel of a continuous vibrated fluidized bed separator is established by introducingcoefficients that identify the bed transport properties and it is pointed out that thesection having an approximately horizontal bed surface should be prolonged to thegreatest extent in order to ensure a good separation performance. The averagetransmission speed of a continuous vibrated fluidized bed separator is also establishedand the optimal region of vibration angle is63°~67°. The separation results show thatthe probable error E value of-3+1mm fine coal separated in an continuous separationsystem using a vibrated fluidized bed is0.225and the two-stage separation process isrecommend for the purpose of improving separation performance.更多还原