振动流化床中潮湿细粒煤聚团的解聚机理研究

Drying, coking, pyrolyzing, gasifying and liquefying are known as the four main ways of efficient utilization of clean coal. Vibration fluidized bed is widely used in the drying and separating process of fine coal. Due to high water content in raw coal, they aggregate together and form agglomeration before entering the fluidized bed. The disaggregation of wet coal agglomeration in vibration fluidized bed has affect the industrial drying and separating process profoundly. Therefore, it is extremely important and necessary to carry out the study of disaggregation mechanism for wet fine coal aggregation in vibration fluidized bed. This project aims at the wet fine coal group adhered by liquid bridge force. High-speed digital video imaging technique will be used to gain an insight into the disaggregation behavior of wet agglomeration under the independent and combined effect of vibration and hot gas. CFD - DEM coupling simulation will be applied to study the disaggregation of wet agglomeration. The behavior of disaggregation, the characteristic of wet agglomerates disaggregation, the rule of the liquid bridges rupture will be discovered under the different vibration and fluid condition. By means of experiment and theoretical calculation, the impact of temperature is transformed to an adjustable parameter in numerical simulation. Thus, the disaggregation mechanism of wet agglomeration in the co-existence of vibration field, flow field and temperature field can be explored. The effect of vibration, flow and temperature to the disaggregation will also be studied and the vibration and fluid requirement to achieved complete disaggregation will be determined. These research will be of great importance and provide guidance to the structure design, parameter adjustment in industrial application of vibration fluidized bed.

煤炭的干燥处理与热解、炼焦、气化和液化并称为煤炭清洁高效利用的四种主要途径，振动流化床广泛地应用于细粒煤的干燥和分选中。开采出的原煤由于水分较高，进入流化床前会粘结成团，深刻地影响着干燥过程和效果，对振动流化床中潮湿细粒煤聚团解聚机理的研究非常重要和必要。本项目针对以液桥力团聚的潮湿细粒煤聚团，利用高速动态摄像机拍摄湿煤聚团在振动、热态气流单独作用和共同作用下的解聚过程，结合CFD-DEM耦合技术模拟解聚过程中的细观状态，揭示湿煤聚团在不同振动、气力作用条件下的解聚行为、解聚模式和聚团内液桥断裂规律； 通过实验和理论计算，将温度对聚团的干燥作用转变为数值模拟中参数的变化，实现振动场、流场和温度场三者共同作用下解聚过程和解聚机理的研究，探究振动场、流场和温度场对潮湿细粒煤聚团的解聚作用，寻求最佳解聚效果的振动和气力作用条件，为振动流化床的结构设计、参数调节、工业应用提供重要指导。

在机械化综采的普及与煤田煤质趋于变差的大环境下，原煤碎煤量越来越大。采煤工作面采取的注水防尘措施使原煤外在水分达7%～14%。这些潮湿的细粒煤聚集成团，给后续的加工作业带来很大的问题。振动流化床广泛地应用于细粒煤的干燥和分选中。.本项目以振动流化床为背景，以湿煤聚团为对象，研究湿煤聚团在振动场、流场和温度场这三个物理场作用下的解聚过程和机理，寻求获得最佳解聚效果的振动、气力和温度作用条件，为振动流化床分选和干燥湿煤提供参考和指导。研究采用循序渐进的方法，先通过实验将温度场对聚团的干燥作用转化为聚团粘结强度的变化，应用到数值模拟中来反映出温度场对解聚的作用效果，随后研究了湿煤聚团在振动场和气力单独作用下解聚的细观过程和动力学机制，接着研究了振动和气力双重作用下湿煤聚团的解聚过程和机理，最后考察了振动、气力和温度共同作用下的解聚效果。.研究发现：①湿煤聚团的振动解聚是聚团内粘结破碎的积累效果，伴随着碰撞造成的裂隙的生长和发展。②聚团内粘结的破碎是碰撞力作用的结果，粘结的破碎率和聚团与底板相对速率有很强的相关性。要使湿聚团振动解聚，存在着最小的振幅条件。③相同激振强度时，“低频高振幅”的振动对湿煤聚团的破碎效果要好于“高频低振幅”。④当湿煤聚团的破碎率达到一定程度后再减小振幅，则对后续的解聚影响很小，采用适合的小振幅反而能提高破碎率。⑤气流的曳力作用在振动前期对聚团解聚的作用很小，曳力作用能减弱聚团与振动板的碰撞，当聚团振动破碎达到一定程度，曳力作用能显著提高破碎率。热气流的干燥作用对聚团破碎的效果要好于曳力作用。⑥在振动前期采用低频大振幅的振动作用和高温小流速的气流作用，当湿煤聚团破碎率达到一定程度（30%~45%）后，减小振动场、降低气流温度且增加流速，能在较低的能耗下获得较好的解聚效果。