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Abstract

Contents

Introduction

Currently, the problem of closing coal mines is very acute – both economically ineffective and those that have exhausted all coal reserves. However, it is not always possible to start the liquidation of a mine immediately with its physical closure. Groundwater from the abandoned mine, after its flooding, can migrate to neighboring mines (if they are associated with the abandoned mining operations), or come out to the surface. The drainage complexes existing at the neighboring operating mines, as a rule, are not able to accept the significantly increased inflow of water. In order not to flood the existing mines, it is necessary to reconstruct their drainage complexes or build new drainages.

The operation of drainage complexes of closing mines has its own characteristics and differences that must be taken into account when automating this technological process.

Thus, the purpose of development is – increasing the efficiency of the submersible drainage system through the development of an automatic control system, which will extend the service life of technological equipment, improve reliability and safety, and also reduce operating costs for the process of drainage of liquidated coal mines.

Achieving this goal is possible due to a deep study of this control object, the development and implementation of the necessary control algorithms using a modern element base – programmable logic controllers and specialized telecommunication networks for the interaction of ACS elements.

1. Relevance of the topic

1.1 Hydraulic characteristics of closed mines in Donetsk

Former mine No.9 «Capital» located on the territory of the Proletarsky district of the city of Donetsk, currently the mine has been liquidated.

Unit is located on the former main industrial site of the mine No.9 «Capital». The nearest industrial facilities are the mines of the former «Krasnaya Zvezda» mine administration.

The average inflow of water according to the study and survey of mines in Budenovskiy and Proletarskiy districts of Donetsk amounted to mine No.6 «Krasnaya Zvezda» – 260 m³/h, No.9 «Capital» – 340 m³/h.

On the basis of a hydro–forecast regarding the possible activation of the process of displacement of rocks and the earth's surface, the following option was adopted to ensure the hydrogeological and ecological safety of the surface.

1.2 General characteristics of a submersible drainage system

Expected mine water production No.9 «Capital» – 340m³/h. Geodetic discharge head – 176.5 m. Technological scheme of a submersible drainage system of a mine No.9 «Capital» is shown in Fig. 1.

The mark of the upper working level +10 m, the lower working level +9 m, the mark of the critical emergency level +30 m, the minimum water level in the catchment area is 6 m (based on the conditions of stable non–cavitation operation of submersible pumping units ANPSH 375–240 [1]).

According to the requirements «Safety rules in coal mines» [2] to pump out the above inflow, three submersible pumping units of the ANPSH type are installed in the skip shaft 375–240: two units – workers, one – standby, pumping is carried out through 3m pressure pipelines with a diameter of 273 x 11.4 suspended in the shaft (Fig.1).

Technological scheme of the submersible drainage system of the mine

Picture 1 – Technological scheme of the submersible drainage system of the mine

The pump is started and stopped in accordance with the operating instructions for the submersible pump unit of the plant.–manufacturer. In working position, the pump unit is completely submerged in water. To protect the pump unit from cavitation in the event of an unacceptable decrease in the water level, the minimum water level in the sump is set at +6 m.Thus, taking into account all the features and restrictions, the level mark +10 m corresponds to the upper level, upon reaching which the submersible is started pumping unit; elevation +9 m – the lower level, upon reaching which the submersible pumping unit stops; +30 m – emergency, critical level, upon reaching which the second submersible pumping unit is launched; elevation +6 m – the minimum permissible lower water level in the sump required for stable, cavitation–free operation of ANPSh submersible pumping units 375–240 (Fig.1)

2. Formalization of the control object

The efficiency of submersible drainage is influenced by a number of parameters of a submersible pumping unit, which determine its current state. [3–4]: Q(t) – submersible pumping unit feed; H(t) – head (pressure) of a submersible pumping unit; HВ(t) – vacuum suction head (back pressure at the inlet to the pump unit); HГ – geodetic discharge head; η – efficiency of the pumping unit; n – pump shaft speed; dВ – suction pipe diameter; dН – diameter of the discharge line; lВ – suction pipe length; lН – delivery line length; aВ – hydraulic resistance of the suction pipeline; aН – hydraulic resistance of the discharge pipeline; hУ(t) – water level in a catchment; QП(t) – hourly inflow into mines.

The above variables and parameters of a submersible pumping unit are interconnected through the equations of the pressure characteristics of the pump and the discharge pipeline [3–4]. The equation of the pressure characteristic of a submersible centrifugal pumping unit is written in the following form: [5–6]:

Equation of the pressure characteristic of a submersible centrifugal pumping unit

Where H0 – pump head created when the valve is closed; Q – supply (capacity) of the pump; A, B, – constant coefficients for the selected type of pump (determined by reference).

The equation of the pressure characteristic of the injection pipeline, as a rule, can be represented as [3–4]:

Equation of the pressure characteristic of the discharge pipeline

Where HГ – the geometrical height of water rise (for the object under consideration is equal to the geodetic injection height – 176.5 m); ΔHФ – actual head loss in the pipeline.

The operating mode of a submersible pumping unit is determined by the joint operation of the pumping unit and the discharge pipeline, and it can be determined by an analytical or graphical solution to the system of equations for the pressure characteristic of the pumping unit and the pressure characteristic of the discharge pipeline. The point of intersection of characteristics (point A) (Fig. 2) determines the operating mode of the submersible pumping unit. It also shows the curve of the pump efficiency and the permissible vacuum head suction НВ.

Characteristics of a submersible pumping unit

Figure 2 – Characteristics of a submersible pumping unit

Рthe operating mode of the centrifugal pumping unit must satisfy the condition of cavitation–free operation HB < HBp. In the submersible drainage system under consideration, the stable, cavitation–free operation of the pumping unit depends solely on the value of the water level in the drainage tank hУ and is provided by its (level) required maintenance.

For the considered control object – a submersible drainage system, the main disturbance that maximally affects and determines the mode of its operation is the hourly inflow of the mine QП. Taking into account the above analysis of the features of a submersible drainage system, its generalized diagram as a control object was obtained (Fig. 3)

Generalized scheme of a submersible drainage system as a control object

Figure 3 – Generalized diagram of a submersible drainage system as a control object (animation: 30 frames, 70 kilobytes)

3. Purpose and functions of ACS

Цspruce of the developed ACS – increasing the efficiency of a submersible drainage system by developing an automatic control system, which will extend the service life of technological equipment, increase reliability and safety, and also reduce operating costs for the process of drainage of liquidated coal mines.

To achieve this goal, you must:

The developed automatic control system for a submersible drainage system of a coal mine should perform the following functions: