The Research And Application Of Huaibei Coal Preparation Plant (North)’s Suspension Density Control System

Coal as an important energy source occupies an extremely important position in primary energy consumption structure in China. With the coal being used largely, more and more attention are paid to energy saving and environmental protection, which contributes to the research and development of coal washing and processing technology. One of the most prominent examples is that the successful application of the dense medium coal preparation has led to the converting of coal jigging into the dense medium coal preparation so popularly that the maximization of coal preparation plant large and the high efficiency of coal preparation can be realized more easily as the coal quality gets worse day by day. In the meantime density control of heavy medium suspension as a core part of dense medium coal preparation has also gotten rapid development. For instance the precise control of the addition of water befor the pump in the use of PID has been achieved to insure the stability of the density of suspension.Huaibei Coal Preparation Plant (North) has a set of density control system, but the automatic control can not be used, so the workers can only control density manually. But manual control of the density would bring about many problems such as larger workload, the low accuracy and the instability of coal products quality due to the serious subjective error from the operator. Therefore the system can not meet the production requirements, technological innovation is urgently required to convert manual control of density system to automatic control which would be intergrated into a centralized control system of the whole plant.This article uses the Quantum series PLC to carry through density control. The general method is that the configured analog input module gather measuring parameters (density, liquid-level, pressure, magnetic material content) from measuring instruments in the work-shop, then the measured density signal would be turned into the digital output after the operation of PLC internal program to control execution institutions, meanwhile the slime content of the heavy medium suspension can be figured out after the measured magnetic content is inputed into the PLC program, then be showed in the host computer. Finally the operator can manually control shunt flow volume of qualified heavy medium according to the slime content. The paper introduces the development of density control of heavy medium suspension at home and abroad and the medium flow process in Huaibei Coal Preparation Plant (North), as well as PLC wiring, communications, programming, and the editing of PC screen. It also includes some simple analysis of control process of the density control system, the methods to meet the control requirements and to operate host computer. Finally it analyzes the reliability of the density control system depending on the date obtained during use.