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Solution of the coal conveying programmed control system in the power plant

The coal conveying programmed control system isto transport coal in the coal yard to the coal warehouse or the coal silo,which mainly includes the coal unloading system, the coal piling system, thecoal loading system and the coal blending system, is an important system toensure stable and full transportation and an important supporting system forsafe and reliable operation of the machine set.

The coal conveying programmed control systemhas many and disperse composed equipments, strong interlock relation between equipments,severe operational environment of equipments and high requirements on securityand reliability, which applies PLC as the main monitoring system to control thewhole technological process; the system has high cost performance, convenientmaintenance and use, stable performance, greatly reducing operation andworkload of maintenance personnel, reducing occurrence of accidents and offeringgreat help to safe and high-efficiency operation to the power plant.

Control mode of the coal conveying programmedcontrol system are designed as site manual control of equipments on the scene,remote manual control and programmed automatic control with a level form highto low in sequence.

Control strategies: control of the coalconveying system is to transport coal in the coal yard to the coal warehouse orthe coal silo through monitoring equipments for transporting coal, which abidesby the following principles:

Coal loading principle

Flow re-starting: choose flow, startcorresponding re-starting device and make starting preparation;

Flow starting: after receiving permissionsignal of starting the flow, the master device of the system starts in delayedsequence and in opposite coal flow direction;

Flow stop: after the stop instruction isissued, the master device of the system stops in delayed sequence and in coalflow direction;

Breakdown interlocking stopping: when themaster device of the chosen flow breaks down, the master device in the upperstream (in coal flow direction) of the breakdown point should be interlocking stoppedimmediately;

Serious breakdown signal: instructions orsignals as dead-stop, digging rope, serious offtracking, serious blocking andslipping etc will lead to interlocking stoppage to the system.

Coal blending principle

Sequential coal blending: set a tail warehousefirst, start to blend coal from the first original coal warehouse, blend coal inthe coal scuttle in the same time (or according to the material location in thecoal warehouse) in sequence till all coal scuttles in and in front of the tailwarehouse issues high coal locating level signal. In sequential coal blending,if there is low coal locating level signal in the warehouse, stop sequentialcoal blending and give priority to blending for low coal locating level;

Preferential coal blending: when there is lowcoal locating level signal in the warehouse, stop the scuttle which is beingused to coal blending and memorize it. Fill up the warehouse of low coallocating level till it is full, and then fill them to high coal locating levelin sequence according to normal sequence of memorizing scuttle. When there islow coal locating level in several warehouses at the same time, take turns toblend coal to these warehouses from front to back till the low coal locatinglevel disappears;

Rest coal blending: when the stopped machineissues signal, allocate the rest coal on the belt to every warehouse till thebelt machine in the original coal warehouse stops.