Non-reloading coal transportation in the eastern inclined shaft of “Raspadskaya” mine

The planned increase in the mine output from 6.5 to 13.6 million tons per year has set the task of reconstructing a conveyor transport in the eastern inclined shaft of the Raspadskaya mine. The roadway length is 4100 m; the reduced inclination angle is +7°40 ́. An attempt was made to combine all the positive global practices in one project: the distribution of drive power along the length of a conveyor belt, minimizing the capital cost of implementation. Within the framework of this article, an approach to choosing the speed of a conveyor belt is discussed, a comparative analysis of the two most common types of intermediate “tripper-type” and “belt-to-belt” drives is given; calculation of a belt conveyor with intermediate “belt-to-belt” drives providing non-reloading conveying in the eastern inclined shaft. Pull force calculations showed that a conveyor belt with four intermediate “belt-to-belt” drives can be implemented as follows: belt width – 1400 mm, belt speed – 4.0 m/s, mono-material load-carrying belt – PVG-4000, mono-material drive belt – PVG-1400, 2-pulley drive units when mounted on one side: head drive power – 2×1000 = 2000 kW, intermediate drive power – 2×1600 = 3200 kW. Thus, the use of a conveyor belt with four intermediate “belt-to-belt” drives in the inclined shaft will give the following results: non-reloading transportation over the entire length of the shaft, reducing the additional degradation of transported coal due to the exclusion of reloading points, minimizing costs through the use of less durable belts, minimizing costs of sinking an inclined shaft of a smaller cross-section.


Introduction
The task arose due to the planned increase in the mine output from 6.5 to 13.6 million tons per year. The length of the reconstructed eastern inclined shaft will be 4100 m; the reduced inclination angle is +7°40´.
The increase in the mine performance is associated with an increase in the daily output to 38,000 tons, which in turn requires the re-equipment of conveyor transport in the inclined shaft.

Results and discussion
The largest average load flow per minute [1] occurs when the time spent directly on coal mining is no more than 18 hours in 4 shifts, and the feed rate of load to be conveyed is not lower than 0.75 V л and the feed rate variation factor k1 . When choosing the optimal conveyors for transporting material over long distances, the determining factors are reliability, capital and operating costs, which are determined by such technical characteristics as belt width, strength and speed [2,3].
Comparison of the operating conveyor load with the peak conveyor performance, which is determined by the conveyor capacity, allows making the choice of parameters such as the belt width and speed (Table 1). It is quite understandable that existing conveyors with a belt width of 1200 mm and a speed of 3.15 m/s will not provide the required performance under conditions of the new shift schedule. During the reconstruction of transport, it is tempting to minimize costs: without increasing the belt width and without increasing the cross-section of the mine, increase the conveyor performance by increasing the speed to 6.3 m/s. But the use of high speeds taking into account a service life of inland rollers of 10,000 hours [4] will drastically reduce the reliability of the conveyor belt. The use of new hot-formed rollers with a service life of 50,000 hours [5] manufactured by Promtyazhmash JSC in Taganrog will help to resolve this problem. Thus, taking into account all the facts considered (Table 1), it is proposed to adopt the following parameters of the conveyor belt: belt width -1400 mm, belt speed -4.0 m/s. The second issue that needs to be discussed is conveyor length and drive power consumption. One of the main priorities of a long belt conveyor is non-reloading transportation, which excludes the additional coal degradation and belt wear. The calculation of conveyor pull for the entire length of the inclined shaft showed that the total drive power is 10520 kW. Modern inland manufacturers do not produce drive units of the required power. In addition, the most durable steel-reinforced rubber belts do not provide the necessary factor of safety.
When designing long belt conveyors, the principle of distributing drive power along the length of the flight is increasingly used in world practice [6,7]. The implementation of this principle is carried out by the use of intermediate drives -boosters. Among others, "trippertype" and "belt-to-belt" boosters found the greatest application.
The first design has three significant drawbacks. They consist in the fact that additional reloading points appear, leading to the additional degradation of transported coal and belt wear. In addition, a reloading point requires an increase in the height of the shaft, which will lead to an increase in its cross section and to an increase in the cost of its sinking.
The second design is devoid of these drawbacks, but requires a highly professional attitude to the selection and configuration of drive control equipment, which ensures the sequential start-up of intermediate drives and prevents the drive belt slippage relative to the load-carrying one. It should be noted that the widespread use of frequency control of asynchronous electric motors completely solves this problem. As a retrospective review shows, the experience of operating an intermediate "belt-tobelt" drive is known both abroad [8] and in Russia [9,10,11].
Thus, in order to ensure non-reloading transportation in the eastern inclined shaft, a belt conveyor with intermediate "belt-to-belt" drives is recommended (Fig. 1).
A closed loop drive belt driven by two independent pulleys is adopted as an intermediate "belt-to-belt" drive (Fig. 2). For these conditions, the number of intermediate drives is assumed to be four. When using less durable load-carrying mono-material PVG-4000 belt, the total drive power will be 10000 kW. It is advisable to divide the entire length of the conveyor into five sections of 820 meters (Fig. 1)    In addition, the drive units must be equipped with Flender bevel-helical gearboxes, which will allow them to be placed along the conveyor to reduce the required shaft width.
As can be seen in Fig. 3 (Fig. 3), which will allow the use of less durable belts, while ensuring the necessary factor of safety.
Pull calculations showed that a conveyor belt with four intermediate "belt-to-belt" drives can be designed as follows: belt width -1400 mm, belt speed -4.0 m/s,

Conclusion
The use of a conveyor belt with four intermediate "belt-to-belt" drives to ensure coal transportation in the eastern inclined shaft will allow: -load conveying without reloading, excluding the additional degradation of transported coal and belt wear, -minimizing costs of sinking an inclined shaft of a smaller cross-section, -minimizing costs through the use of less durable load-carrying and drive belts.