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In working coal deposits, it has become important to control the quality, especially in extracting coking coals. As a rule, coking coals have inhomogeneous petrographic composition, variable ash content, and very variable technical properties. This is clearly seen in Fig. 1, which is a plot of the main indices of the quality of coking coals -the ash content A c and the plastic layer thickness Y -of the extraction blocks along the extraction front of the Moshchnii seam of the Neryungrinskii deposit.The value of the commercial product is primarily determined by the values of Y and A c in the coal concentrate. However, during concentration the plastic properties of the coals remain almost unaltered, and therefore improvement and stabilization of the coal quality according to this index must be wholly effected during extraction and preparation of the coal.Quality control of won coal aims at obtaining mean values of the quality indices within the permissible ranges, at stabilizing the mean values over the periods of operation of the extraction subsystem, and at smoothing the variations of the particular values of the index relative to the mean.The first two methods of quality control are mainly effected during extraction operations by using the following forms of organization of the technical processes : iii) Compiling a timetable of arrivals of transport units from the face at the discharge stations.In this connection, planning of the operational indices of the extraction subsystem can be regarded as a search for the optimal values of the parameters of the forms of organization enabling us to attain the highest coal quality level in the successive stages of the coal extraction technology. Let us consider the solution of these problems, taking as an example the following organization of the extraction and blending technology.A pit contains n extraction faces. The coal from each face arrives in the form of a discrete flowformed by the coal trucks with carrying capacity q. The won coal arrives at the receiving pits of the technical coal preparation complex for processing; the following processes are involved: crushing, screening, and storage in three silo-type bunkers. The capacity of each bunker is equal to the output of the mine in one shift. The construction of the bunkers involves forced bulk flow of coal through hoppers uniformly distributed over the base.The technical scheme will be used as an example to make a mathematical analysis of the transformation of the magnitudes of the quality indices during the processes of extraction and coal preparation, taking one of the quality indices as an example.Let Yij be a random variate characterizing the index being monitored in the j-th coal truck from the i-th face. -We will ass _u~ne that for each value of i, the series Yij, J =1, 2 .... , is a stationary random process with expectation value Yi and dispersion ~i 2 =a2(Yi ), and also that low-frequency harmonics predominate in the spectral expansion of the correlation function of each initial random process. When we intro...

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Efficient mining of mineral reserves of a complex composition (copper and iron ore or coal) is secured by separate processing of different classes or grades of ores and coals occurring at the same location and extracted in a stable volume flow. An example is the Neryungrin coking coal deposit. During the first years of operation, coking coal will be extracted in an area where transitional and unoxidized zones are contiguous. The contact has a sinuous shape, with a frequent interpenetration of the areas of coking and steam coal. It would be impossible to separate excavation stopes to work exclusively the zones of either steam or coking coal. Figure i, based on actual data, shows that each stope contains a succession of areas of coals of the two classes.The reserves planned for mining within a calendar quarter are selected so as to ensure the required outputs of each of the two coal grades. This does not guarantee the proper ratio of the two grades within shorter periods of time because of the variability of coal classes in a stope and the type of excavators used. This poses the planning problem of optimizing the operation of the excavation work systems (EWS) assuming separate working of the two types of coal. The goal is to obtain a time-stabilized flow of coking coal. Models describing the EWS behavior under these conditions belong to the class of dynamic models with discrete time. In contrast to static models, they account for coal variability within a stope as well as the composition of the loading plant during the plan interval. The strategy involves breaking the plan interval (0, T) into a set of unit periods (j = i, 2, .... J) whose length is determined by the possibility of describing the system's behavior in the unit period j by a static model.The conditions introducing the dynamic properties into this system are the periodic maintenance stoppages of the excavators and the switching of excavators to the working of new mlnlng-englneerlng blocks (k, i) according to prescribed sequences. The situation change step is the length of the most frequent type of preventive maintenance inspection (MI), which, for example for the exacvators EKG-12.5 and EKG-81, is taken at 3 days. This interval on average is equal to the working time of a mlning-engineering block. Two alternative models are used which differ in the degree to which they incorporate the relations between the system operation during different unit periods of a plan interval. The models of a dynamic system, including that of EWS, which consider only how the system operates in a given period j as affected by the result of its operation in the preceding periods and the system state within time j, or systems with direct dynamic relations, are referred to as conditionally dynamic models (CDMs). The models that, in addition to direct dynamic relations, incorporate also so-called reverse dynamic relations, which reflect the impact of the future conditions of system operation and incorporate their operation in the current period, are called full dynamic models (...