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Some aspects of extreme control in coal concentrates production |
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Some aspects of extreme control in coal concentrates production Authors: S. Cierpisz, J. Pielot
Stabilization of coal quality parameters is an important technological problem especially in the presence of variable raw coal characteristics such as coal size distribution and its washability. Local control systems for gravitational preparation processes have been introduced (the control of the density of separation in heavy media vessels and the refuse discharge in jigs) to compensate the influence of various disturbances on the performance of technology. The controlled parameters are in coal flotation: the amount of air, levels of slurry, the concentration of solids in the feed and the dosage of reagents added to the process. The main task of these local control systems is to stabilize technological chosen parameters on the desired level, which makes it easier to keep the quality of coal within the limits of declared price and allows to control final products parameters according to the terms of the contract. Concentrates of steam or coking coal are often produced in a system of parallel processes of coal separation in heavy media vessels, jigs and flotation. In such a system there usually exists an optimal point of work (global extremum) for which the maximum amount of the final concentrate with desired ash content can be obtained. The amount of concentrate for this point is usually greater by 3-8% of the concentrate yield obtained for practically applied parameters of technological circuits. This fact encourages research works that can lead to practical solution and implementation of control systems which enable the operation of the technological system close to the optimal point. The paper describes the methods of control that maximise the amount of the final product with desired ash content. They the apply algorithms of the search for the optimal point of operation by systematic changes of separation densities in the parallel processes of gravitational coal separation in heavy media and jigs. The density of separation in jigs can be changed indirectly, for instance by the adjustment of the float position linked with refuse removal gate. For the technological system of the separation of coking coals, which also employs a flotation process the controlled parameters are the amount of air, the dosage of reagents and the levels of froth in chambers. The concept of control in this case is the same.
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2011