In the coal industry, mines with large water inflow account for a large proportion, and the safe and reliable operation of drainage system is directly related to the safe production of mines. At present, traditional coal mines still insist on using manual start-stop equipment and manual monitoring drainage system, which has low automation and poor emergency response ability, and there are great security risks. At the same time, in order to completely cover the underground drainage site, there are more workers and the labor efficiency is low. With the increasingly severe situation of overcapacity in the coal industry, safety in production has attracted more and more attention from the society. At present, science and technology are progressing rapidly. Under the background of industrialization and information integration, it is an important link to realize unattended automatic drainage. It is the development direction and inevitable trend of intelligent mine in the future to realize automatic drainage of unattended main drainage pump house, transfer sump and discrete puddle, monitor the running state of drainage equipment, analyze energy consumption, intelligently diagnose the health status of equipment, provide preventive maintenance scheme for equipment maintenance, improve the service life of equipment and reduce the failure rate [1-3].
Jinjie Coal Mine 1 Overview of Hydrological Conditions and Drainage System
The main aquifers in Jinjie Mine Field are loose pore phreatic water (sand water) and pore fissure confined aquifer (weathered magmatic water) of Zhiluo Formation. The former includes river valley alluvial diving and Salawusu Formation diving. There are holes, cracks and phreatic water in the burnt rocks in some areas. At present, the normal water inflow of the mine is about 3,700 m3/h, and the main components of the water inflow are as follows: each fully mechanized working face is about 700 m3/h, the mined-out area is about 1 1,500m3/h, the drainage of each standby working face is about 1 1,500m3, and the water inflow of each shaft roadway is small. There are 2 central main drainage pump houses, 4 panel drainage pump houses and 2 submersible drainage pump houses in the mine. According to the existing main drainage system and pipeline equipment, the current mine drainage capacity is 13300m3/h, which can meet the existing mine water inflow fortification requirements and has a large surplus.
2 underground automatic drainage system
2. 1 automatic drainage system of main drainage pump house The main drainage pump house is the core of underground drainage system of coal mine, which provides power for the whole mine drainage system. The equipment configuration in this paper is based on Jinjie Coal Mine. Each wear-resistant centrifugal pump in the main drainage pump room is equipped with high-power three-phase asynchronous motor, electric outlet gate valve, electric emptying ball valve, pressure sensor, vacuum sensor and other automation equipment. At the same time, in order to ensure the normal operation of centrifugal pumps, mines are equipped with exhaust equipment or have formulated special plans. Coal mine drainage integrated automation system mainly collects and detects analog data and digital data automatically. The data of analog quantity detection mainly include water level of water storage tank, working current of motor, shaft temperature of water pump, motor temperature, and three drainage flows. The data of digital quantity detection mainly include the status of vacuum circuit breaker and vacuum contactor of high-voltage starting cabinet of water pump, the working status and open-close position of electric valve, the working status of vacuum pump, the status of electromagnetic valve, the vacuum degree of water suction pipe of water pump and the pressure of water outlet of water pump.
The collection of the above data is mainly realized by PIC. The sensor transmits the analog data to PLC, and then the PLC calculates and processes the data accordingly, and judges the coal mine water inflow according to the related factors, so as to control the start and stop of the water pump. Most of the remaining simulation data is used to supervise the operation of the automatic control system, so as to feed back information in time when the system fails, so that the system can make relevant adjustments in time to avoid damaging the water pump and motor. After all kinds of data information are collected in PLC, they are used as the conditions and basis for related logic processing to control the operation of water pump. In the whole process, the specific processing method is to convert analog signals into digital signals under appropriate sampling rules, and then process them through PLC, so as to realize the automatic control of water pumps [4,5].
2. 1. 1 master control system The master control system of the main drainage pump house consists of PLC controller, I/O equipment and various sensors. The automatic drainage system has the following functions: ① the water level of the water tank is monitored in real time by the water level sensor, and the controller sends out the instruction to start and stop the pump according to the set high and low water levels, and adjusts the number of running pumps according to the rise and fall of the water level; (2) According to the principle of uniform equipment wear, switch the working pump and the standby pump to prevent the motor from being affected with damp due to long-term idleness of the pump; ③ The main drainage pump control system has one-button start-stop function, and can meet various control modes such as local one-button start-stop, remote one-button start-stop and maintenance. ④ The system has motor protection functions such as overload protection, short-circuit protection, open-phase protection, under-voltage release, over-torque protection and automatic phase sequence correction, and has pump flow and pressure protection functions [8, 9].
2. 1.2 monitoring system The automatic drainage monitoring system is the central command of the main drainage pump house, which realizes data uploading and ground remote monitoring of the main drainage pump through the mine ring network, thus realizing data sharing. In order to realize unattended pump house, according to the actual effect and engineering experience of the monitoring system of the main drainage pump house in Jinjie Coal Mine, the monitoring system of the pump house should have the following functions [6,7]: ① Monitor the real-time water level of the water tank online, with the required error not exceeding 01m; ; ② On-line monitoring of various parameters during the operation of the main drainage pump, such as the running state of the pump, the working voltage and current of the motor, the opening state of the electric gate valve and electric ball valve, the real-time pressure of the outlet pipe, etc. (3) installing a flowmeter in the drainage pipeline to monitor the instantaneous flow and cumulative flow of the pipeline, which can monitor the utilization of the drainage pipeline; (4) It has the function of historical data query, and the real-time monitoring data in the operation process can be stored in the historical database to realize the functions of historical echo and historical trend analysis; ⑤ It has the alarm function of analog quantity exceeding the limit, and the fault information is stored in the historical data of alarm record; At the same time, fault information can be pushed to relevant personnel;
⑥ Self-diagnosis function of system fault; ⑦ The monitoring software has the characteristics of friendly man-machine interface, simple and intuitive operation, on-demand management of authority and intuitive display of dynamic pictures. ⑧ Ensure that the system runs reliably, with low failure rate, convenient maintenance and simple configuration modification. Coal mine drainage integrated automation system mainly collects and detects analog data and digital data automatically. The data of analog quantity detection mainly include water level of water storage tank, working current of motor, shaft temperature of water pump, motor temperature, and three drainage flows. The data of digital quantity detection mainly include the status of vacuum circuit breaker and vacuum contactor of high-voltage starting cabinet of water pump, the working status and open-close position of electric valve, the working status of vacuum pump, the status of electromagnetic valve, the vacuum degree of water suction pipe of water pump and the pressure of water outlet of water pump. The collection of the above data is mainly realized by PIC. The sensor transmits the analog data to PLC, and then the PLC calculates and processes the data accordingly, and judges the coal mine water inflow according to the related factors, so as to control the start and stop of the water pump. Most of the remaining simulation data is used to supervise the operation of the automatic control system, so as to feed back information in time when the system fails, so that the system can make relevant adjustments in time to avoid damaging the water pump and motor. After all kinds of data information are collected in PLC, they are used as the conditions and basis for related logic processing to control the operation of water pump.
2. 1.3 Analysis of equipment health status Intelligent mine is the inevitable trend of modern mine development, and intelligent diagnosis of drainage equipment is the key link of intelligent drainage equipment. Understanding the real-time operation of the equipment and the health status of the equipment itself is the premise of unattended pump room. Multi-dimensional intelligent sensors are installed on the water pump and motor, and the vibration and temperature (stator temperature and shaft temperature) of the water pump and motor are monitored in real time by wireless signal transmission, and the frequency spectrum analysis of vibration, sound and temperature of important parts of the motor and equipment is established, and fault judgment features are extracted, and classified alarms are given according to the size of the features, so as to detect and warn the potential mechanical damage of the motor and predict the development trend of the equipment state. The sensor integrated substation can be connected with the handheld terminal of the maintenance personnel through wireless communication modes such as Bluetooth, and the maintenance personnel can read the running status and health status of the equipment when they are close to the equipment. At the same time, the substation can directly push the alarm, early warning, maintenance and replacement information of the equipment to the maintenance personnel.
2. 1.4 energy consumption analysis of drainage system. The main drainage pump houses in the mine are all equipped with panel substations to realize data interaction between automatic drainage system and substation. Through intelligent analysis, the principle of "peak clipping and valley filling" is adopted to reasonably arrange the running time of the pump, so as to make the pump run under low load as much as possible, reduce the fluctuation of daily load curve, reduce the active loss and reactive loss of power lines and save electricity bills. See table 1 for the pump operation table of the second central pump house in Jinjie Coal Mine. After long-term use, the drainage pipe will scale on the pipe wall, increase the pipe resistance and indirectly reduce the pipe flow. Through the flowmeter installed on the inlet and outlet pipelines of the main drainage pump house, the flow of the drainage pipeline can be monitored in real time, and the data can be analyzed in the background to understand the specific situation of pipeline scaling, which is of guiding significance for removing pipeline scaling in time and improving pipeline operation efficiency. Jinjie Coal Mine cleaned up the pipeline scaling in time through pipeline flow monitoring combined with data analysis, as shown in Table 2. After the improvement of pipeline fouling, the efficiency of the pump is improved and the energy consumption per ton of water is increased by about 5%. After long-term use, the drainage pipe will scale on the pipe wall, increase the pipe resistance and indirectly reduce the pipe flow. Through the flowmeter installed on the inlet and outlet pipelines of the main drainage pump house, the flow of the drainage pipeline can be monitored in real time, and the data can be analyzed in the background to understand the specific situation of pipeline scaling, which is of guiding significance for removing pipeline scaling in time and improving pipeline operation efficiency.
2.2 Automatic drainage of transfer sump and dispersed sump
Underground transfer sump is responsible for drainage transition and supplementary drainage power along the line. In traditional coal mines, post workers are still set up to operate the water pump of the transfer sump on the spot, which has low labor efficiency. Due to the influence of roadway height, the application effect of automatic drainage device of negative pressure suction tank is poor. At present, the automatic drainage of transfer water tank is usually equipped with automatic equipment such as centrifugal pump, electric gate valve, water injection and exhaust solenoid valve. In the initial design, the pipeline should be adapted to the pump to improve the operating efficiency of the pump working point. From the practical application effect, the water injection solenoid valve is frequently started and its service life is short, which directly affects the normal operation of the pump. Therefore, it is necessary to set the high and low water levels of the pump to avoid frequent starting of the pump. The underground distributed small water pump is mainly controlled by the magnetic starter, and the water level probe of the magnetic starter is on and off. Because there are many scattered puddles in the underground, the configuration screen cannot be updated in time due to frequent equipment updates. Jinjie Coal Mine makes electronic labels according to the purpose and location of the equipment, so that the equipment can be displayed immediately.
3 underground water regime monitoring and analysis system
Water disaster prevention and control has always been the focus of mine water prevention and control. At present, the mine drainage system can not directly reflect the actual situation of underground water regime change. As shown in figure 1, water level and flow sensors are added at the water level, inlet and outlet of mine goaf, and flow meters are installed at the outlet pipes of underground return air lane and drainage lane to monitor mine water regime in real time. The system provides the trend analysis of mine water regime, realizes intelligent combined drainage of mine through advanced Internet of Things technology, and provides decision-making reference for water prevention and control. The water regime monitoring system can not only collect information such as water level, pressure and pump status at each monitoring point, but also need relay output function, which can control the switch to start and stop the pump and give an alarm and early warning to realize dynamic, real-time and interactive water regime monitoring. The functional structure of water regime monitoring system is shown in Figure 2. The water regime monitoring system can draw real-time and historical trend curves of water regime, and automatically generate various reports.
4 conclusion
On the basis of introducing the characteristics of automatic drainage system in coal mine, this paper studies the working principle of each part of automatic drainage system, expounds the working principle of automatic drainage system in coal mine, and highlights the advantages and significance of applying automatic drainage system in coal mine, thus explaining the importance and necessity of implementing automatic drainage in coal mine. By improving the underground automatic drainage monitoring system, Jinjie Coal Mine has realized the unattended operation of the main drainage pump house, transfer sump and small sump. On the basis of unattended operation, the mine water regime monitoring is carried out, and the mine combined drainage scheme is put forward. At the same time, the energy consumption per ton of water can be reduced by about 5% by monitoring the drainage situation of the pipeline, reasonably arranging the operation time of the pump, improving the operation efficiency of the pump, timely dealing with the scaling phenomenon of the water pipe and improving the operation efficiency of the pipeline.
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