选煤方法主要有跳汰法、重介质法和浮选法，由于重介质法分选精度高、工艺简单、操作方便、易于实现自动化，所以张家峁洗煤厂采用重介浅槽选煤方法。在重介质选煤过程中，重介悬浮液密度的稳定性是决定选煤厂的精煤洗出率、产品质量（灰分含量）的重要因素，其对企业效益有着十分重要的意义。 张家峁洗煤厂原有控制系统只能实现起停车的集中顺序控制，在重介悬浮液循环过程中，影响悬浮液密度的配料、加介、分流以及密度调节均采用人工的方式进行，主观因素较大，且在运行过程中很难保持悬浮液密度的稳定，密度低时会影响分选效果，造成煤炭浪费，如矸石中含煤现象发生，密度高时，会造成介质浪费情况，还会产生煤中含矸现象出现，影响产品品质，因此重介悬浮液密度控制的研究是十分必要的。 本文首先介绍了张家峁洗煤厂的设备布局与重介洗煤工艺，并分析了影响重介悬浮液密度的主要因素与关键环节，由此将合介密度、煤泥含量以及合介桶的液位等作为主要控制对象，确定系统的主要监测点、控制对象与方式，并根据有关参量的影响关系以及控制任务给出了系统控制的原理框图。 根据课题的研究目标，在原有ControlLogix/1756 系列PLC框架的基础上，作出系统硬件、PLC模块、检测传感器及执行机构的设备选型，提出系统的最终控制目标，然后根据控制目标和悬浮液循环过程中各参量耦合的复杂性选择Fuzzy-PID控制原理作为其主要控制器的设计依据，设计出该系统的控制软件与控制算法。 根据控制系统的硬件与软件设计，在原有系统的基础上完成了系统的硬件的安装与调试，在Logix5000软件平台上完成了系统的组态和控制软件程序设计与调试，达到了设计要求，使重介悬浮液的密度稳定在（1.6±0.05）g/cm3的范围内。系统运行以来精煤洗出率提高了3%，灰分含量下降了2.3%，达到了预期的目标。

Coal preparation methods mainly include jigging， dense medium and flotation method， due to the heavy medium separation of high precision， simple technology， convenient operation， easy to realize automation， so the method of the dense medium coal preparation is adopted in Zhang JiaMao coal washery. In dense medium coal preparation process， the stability of heavy medium suspension density is decided to coal preparation plant to wash out rate (ash content)， product quality and enterprise benefit has very important significance. The original control system of the Parking Zhang Mao coal washery can only achieve the sequence control. In the process of dense medium suspension liquid loop， effects of slurry density， ingredients， add interfaces and density adjustment adopts artificial manner， it is difficult to maintain the stability of suspension liquid density in the process of running， so dense medium suspension density control research is very necessary. This article first introduced the Zhang Mao coal preparation equipment layout and dense medium coal washing process， and analyzes the main factors influencing dense medium suspension density and the key link， the suspension liquid density， content of coal slime and liquid level of qualified medium bucket are the the major point controlled objects. The monitoring stations and control mode are determined， and the principle diagram is presented according to the influence of the relevant parameters and control tasks. According to the research target， on the basis of the original AB ControlLogix PLC， the system hardware， PLC module， detection sensor and actuator are designed and selection; The main controller is designed based on fuzzy-PID control principle according to the complexity of the process. On the basis of the hardware and software design of control system， this is accomplished the installation and debugging of the hardware of the system， on Logix5000 software platform to complete the system configuration and control software programming and debugging， and the design requirements have been reached， the density of heavy medium suspension stability in (1.6 + 0.05) g/cm3. The cleans washout rate increased by 3%since the system is running， ash content decreased by 2.3%， achieved the desired goal.