Conveying length L=3005m
Conveyor belt width B=1200mm
2.2.2 Line parameter
East wing of the first mining area of the upper mountain of the main transport alley***3005 meters, can be simplified as shown in Figure 2.1 of the eight segments: the first section (1 point to 2 points) level transport, length 540 meters; the second section (2 points to 3 points) down transport, the horizontal length of 207 meters, lifting height -27.1 meters; the third section (3 points to 4 points) flat transport, the horizontal length of 62 meters; the fourth section (4 points to 5 points) down transport, the horizontal length of 518 meters, lifting height -82 meters; the fifth section ((5 points to 6 points) flat transport, length of 470 meters; the sixth section ((6:00 to 7:00) up transport, horizontal length 360 meters, lifting height 18.9 meters; the seventh section ((7:00 to 8:00) down transport, horizontal length 400 meters, lifting height -28.4 meters: the eighth section (8:00 to 9:00) down transport, horizontal length 435 meters, lifting height -56 meters; the whole machine horizontal length 2992 meters, transport length 3005 meters.
Figure 2.1 Conveying line parameter diagram
2.2.3 Material characteristics
Conveying material Raw coal
Material density ρ=900kg/m3
Material angle of repose 50°
2.2.4 Belt Conveyor working environment
Installation location: the main transportation lane of the uphill of the first mining area of the east wing of Dongtan Mine. The bottom plate is coal.
Ambient temperature: 0~35℃.
Due to the unevenness of the belt conveyor roadway, there are a lot of variable slope points, resulting in this belt conveyor operating conditions are quite complex, is currently the most complex operating conditions in domestic and even foreign coal mines, one of the most complex belt conveyor: from the other hand, the operation of the belt conveyor under the transportation of the safety and reliability of the requirements of the high, complex control system, and the theoretical study of the belt conveyor under the transportation of our country is relatively small, in particular, the long distance, large capacity under the transportation of the conveyor, and the control system is complex. Distance, large capacity under transport belt conveyor system of working condition analysis, dynamic analysis, starting, braking technology research is less, which is also this paper choose long distance, large capacity under transport belt conveyor for the purpose of research.
2.3 Research contents of this topic
2.3.1 Analysis and research on key technology of long-distance and large-capacity downstream belt conveyor
Through the analysis and comparison of various composition schemes of downstream belt conveyor drive, and the theoretical research on soft braking technology and soft starting technology in the drive scheme of conventional long-distance and large-capacity downstream conveyor, the researchers put forward the proposal of long-distance and large-capacity downstream belt conveyor drive.
2
Long distance and large capacity belt conveyor under transport belt conveyor common driving and braking methods, and analyze the advantages and problems of common driving and braking methods, and summarize the long distance and large capacity belt conveyor under transport belt conveyor key driving and braking methods to choose the basis.
2.3.2 Design of belt conveyor and analysis of driving and braking scheme
In view of the design parameters of the fixed downstream belt conveyor in the main transportation lane of the first mining area of the east wing of Dongtan Coal Mine of Charging Mine Group and its complicated working conditions caused by the special working environment, firstly, the design and calculation of the working conditions under normal operation are carried out, and then the calculation of the unloaded and the maximum positive and maximum negative working conditions are carried out, and the results of the calculation of the various working conditions are summarized. Then analyze and discuss the results of various working conditions, and finally determine a reasonable tensioning method and tensioning force size, and propose a reasonable selection of tensioning devices.
Through a variety of working conditions of the calculation, analysis and comparison, put forward a reasonable drive device, motor, reducer, soft starting device (speed hydraulic coupling) and soft braking device components selection program.
3 long distance, large capacity downstream belt conveyor key technology analysis
3.1 downstream belt conveyor basic composition
Belt conveyor composition as shown in Figure 3.1 [2], the main its: conveyor belts, drive devices (motor, reducer, soft starting device, brake, coupling, backstop), drive roller, reversing roller, roller group, tensioning device, unloading device, soft braking device. Group, tensioning device, unloader, frame, hopper, guide chute, safety protection devices and electrical control systems and other components.
1-head funnel; 2-frame; 3-head sweeper; 4-drive roller 5-safety protection device; 6-conveyor belt; 7-carrying rollers; 8-buffer rollers; 9-guide chute; 10-reversing roller; 11-tensioning device 12-tail frame; 13-empty section sweeper; 14-return rollers; 15-intermediate frame; 16-motor; 17-liquid couplings; 18-brake; 19-reducer; 20-coupling
Figure 3.1 Schematic diagram of belt conveyor composition
3.2 Determination of drive program
The drive section of the belt conveyor is the key component of the whole machine composition. Whether the configuration of the drive section is appropriate or not, it directly affects the normal operation of the belt conveyor. Long distance, large capacity belt conveyor with down transport belt conveyor requirements than the general requirements of the belt conveyor, it requires the drive can provide smooth, smooth starting and stopping braking torque to ensure that the conveyor belt does not appear over-speed, skidding and conveyor belt on the material does not appear to roll and slippery material phenomenon. For this reason, the drive device is required to have a brake power can be adjusted at any time to ensure that the starting and stopping brake can be controlled, greatly reducing the impact on the material. At the same time, in the conveyor no-load start also need to ensure the smoothness of the start.
Downloading belt conveyor by the terrain conditions (such as undulation) and the impact of loading, the starting conditions are more complex, should be considered as follows:
(1) the load is small or unloaded, after the release of the belt conveyor can not self-start;
(2) the load is large, after the release of the belt conveyor can self-start, but the natural acceleration of the smaller;
( 3)The load is large, the belt conveyor can start itself after releasing the gate, and the natural acceleration is large.
Down transport belt conveyor in normal operation, the motor also exists in the power generation condition, electric condition intertwined operation, so in the design, generally less consideration of soft starting device. Belt conveyor configuration down transport belt conveyor in normal operation, the motor also exists in the power generation condition, electric power condition intertwined operation problem, so in the design, generally less consideration of soft starting device. Belt conveyor configuration soft starting device, can effectively reduce the starting and braking process of dynamic tension, extend the service life of the conveyor belt and joints, and even reduce the strength of the conveyor belt, has great economic significance. This "coal mine safety regulations" made corresponding provisions.
Since the downstream belt conveyor is generally working in the electric motor in the power generation condition, and the motor is working in the electric power condition in the no-load condition, the commonly used downstream belt conveyor is working in the power generation condition. Currently commonly used down conveyor belt conveyor drive department typical equipment configuration as shown in Table 3.1.
Table 3.1 Commonly used downstream belt conveyor drive department combination table
Combination
Equipment 1 2 3 4 5
Electric motor Single or multi-machine 1:1 (or 2:1) drive Single drive or multi-machine 1:1 (or 2:1) drive Multi-motor 1:1 (or 2:1) drive Multi-motor 1:1 (or 2:1) drive Multi-motor 1:1 (or 2:1) drive Multi-motor 1:1 (or 2:1) drive Multi-motor 1:1 (or 2:1) drive Multi-motor 1:1 (or 2:1) drive Multi-motor 1:1 (or 2:1) drive Not big
3.3 New type of downstream belt conveyor drive combination and its control process
Most downstream belt conveyors use the following drive combination:
(1)Motor-brake-reducer-roller
((2)Motor-restrictor-reducer-roller
() 2)Motor-torque-limiting fluid coupling-brake-reducer-roller
(3)Motor-torque-limiting fluid coupling-reducer-controllable actuator-roller Controllable braking device - drum
(4)Motor - soft start - reducer - hydraulic soft brake - disk brake device - drum
(5)Motor - soft start - reducer - hydraulic soft brake - disk brake device - drum
(5)Motor-soft start-reducer-hydraulic soft brake-disc brake unit-roller
(6)Motor-soft start -reducer-controllable disk brake-roller
(7) motor-soft start-reducer-hydraulic soft brake-roller
Which way (1) to (3) is mostly used for small (short distance, small inclination, small capacity, low belt speed) on the way down the conveyor; (4) to (7) is more suitable for large inclination angle down the conveyor. From the above program can be seen, the lower conveyor can be controlled to start the device is essential; and at present the lower conveyor electric conditions can be controlled to start the problem has been ignored. For long distance, large capacity down conveyor belt conveyor, controllable driving device is essential, while controllable starting device has become necessary.
To this end, we propose an economical and practical combination of long-distance, high-volume, high-power downstream belt conveyor drive program. The program drive section mainly consists of the following equipment: motor, coupling, speed-regulating hydraulic coupling, reducer, controllable driving device, drive roller and other components, as shown in Figure 3.2 [3].
Figure 3.2 Schematic diagram of the driving part of the combined program
The starting and stopping process of the downstream belt conveyor using the above driving combination is as follows:
(1)Start-up preparation: firstly, send power to the electrical system of the soft starting device and the hydraulic system, so that the master and slave friction plate is closed, and the controllable driving device can be controlled to gradually loosen the gate, and if it is a heavy load, the heavy vehicle will be gradually and automatically started by the heavy car according to the starting requirements. Start the belt conveyor.
(2) when the conveyor belt in the case of loaded materials to start the belt conveyor, can not be directly on the motor to send power, otherwise start too fast, the material is prone to sliding or rolling material, so in this case but by the sliding force of the coal to start the conveyor, when the brake is gradually released, the conveyor belt drives the motor to rotate, through the speed sensor to detect the rotational speed, when the speed reaches near the motor synchronous operation speed When the speed reaches the synchronous running speed of the motor, the PLC controls the motor to send power to start automatically, so that the motor runs in the normal state of power generation, which can greatly reduce the impact on the electrical and mechanical when the motor starts. Moreover, the larger the downward conveying angle is, the larger the starting acceleration is. In order to ensure smooth starting, the braking force applied by the brake is changed through speed feedback, and the acceleration is controlled within 0.3m/s2 according to different braking forces to ensure the smoothness of the starting process.
(3) direct motor start control, when the conveyor is no load or light load, gradually release the brake, the conveyor can not automatically start, according to the speed measurement device to detect the conveyor is in zero speed state or start too slow, need to use speed-regulating hydraulic coupling to controlled start belt conveyor, this time, the controlled start process is exactly the same as on the starting process of the belt conveyor.
(4)During normal operation, the opening degree of the speed-regulating hydraulic coupling is maximum, and the transmission efficiency reaches the maximum.
(5) when the multi-motor drive, there is a motor overload, need to balance the power, according to the motor's current feedback to the speed-regulating type hydraulic coupling input and output speed adjustment (see the electrical part), to carry out the multi-motor power balance between the adjustment. Generally as long as the belt conveyor system design is reasonable, can ensure that the system of multi-machine power balance.
(6) when stopping, according to the predetermined deceleration requirements for closed-loop change of the braking torque of the movable system, so that the belt conveyor decelerates according to the predetermined deceleration, to realize the controllable stopping.
(7)When the conveyor stops with the load, the motor can not be cut off directly, otherwise it is easy to fly phenomenon, resulting in serious accidents. For this reason, when stopping, first apply braking force to the conveyor, when detecting the motor rotation speed down to its synchronous speed, and then cut off the power to the motor, so that when applying braking force to reduce the speed, you can make full use of the braking force of the motor, so that the stopping of the smoother. When the speed of the conveyor drops to the synchronous speed of the motor, the speed-regulating hydraulic coupling spoon tube is inserted all the way in to ensure the synchronous excision of the motor and the conveyor system, which ensures that the controllable system can be further decelerated and parked as required.
(8) If the stopping time, the belt conveyor is unloaded (i.e., the main motor is in the electric state), it can be the same as the stopping process of the upper transport belt conveyor combined with the controllable moving device for the joint parking brake.
(9) when the fixed car, can control the braking device, the main motor shutdown, speed control type hydraulic coupling hydraulic and electrical system blackout.
(10) In the process of starting and stopping faults, such as conveyor belt deflection, tearing the belt, oil temperature is too high, etc., the speed-regulating hydraulic coupling and controllable control system of the electrical control system of the movable device will be automatically controlled according to the requirements of the shutdown.
4 Long distance and large capacity under transport belt conveyor design
Charge Mining Group Dongtan Coal Mine, the east wing of a mining area of the main transport aisle stationary belt conveyor, distance 3005 meters, capacity 1800 tons / hour, lifting height - 175.5 meters, the ambient temperature of 0 ~ 35 ℃, is a typical coal mine long distance, large capacity under transport belt conveyor. Belt conveyor. Due to the unevenness of the belt conveyor roadway and the large number of variable slope points, the operating conditions of this belt conveyor are quite complicated. In addition, this machine requires high safety and reliability, and the control system is complicated, so it is a belt conveyor with more complicated operating conditions in domestic and even foreign coal mines. This chapter takes this under transportation belt conveyor as an example to illustrate its design process.
4.1 Original parameters of the belt conveyor
Belt conveyor is the main conveyor equipment for underground coal at present, and the advanced degree of automation of its design, structural arrangement, use of safety, reliability, continuity and efficient operation will directly affect the production cost of the mine. Using belt conveyor to transport materials has a series of superiority and high efficiency compared with other methods, and its high degree of automation represents the development direction of modern logistics technology. This topic requires the design of the parameters of the belt conveyor as shown in Table 4.1.
Table 4.1 Original parameters of the conveyor
Capacity Q 1800t/h
Distance L 540 207 62 518 470 360 400 435
Drop height 0 -27.1 0 -82 0 18 -28.4 -56
Total drop height - 175m
Total distance L 3005m<
Average inclination angle β -4°
Maximum lump size 300mm
Coal capacity γ 0.9t/m3
Coal angle of repose 50°
4.2 Belt Conveyor Design and Calculation
4.2.1 Selection of Conveyor Belt Running Speed
Conveyor belt running speed is an important parameter in the calculation of the design of conveyor. The running speed of conveyor belt is an important parameter for the calculation of conveyor design. When the conveying capacity is certain, the belt width can be reduced by increasing the belt speed appropriately. For the horizontal installation of the conveyor, a higher belt speed can be selected, the larger the conveyor inclination, the lower the belt speed should be, the higher the belt speed can be when conveying upwards, and the lower the belt speed should be when conveying downwards. At present, the recommended belt speed of DTII series belt conveyor is 1.25~4m/s. For the downstream belt conveyor, considering the difficulty of management, the belt speed is generally determined to be 2~3.5m/s. According to the specification of the belt conveyor in the downstream groove of the working face (bandwidth of 1.2m, belt speed of 3.15m/s), the actual production capacity of the working face, and the unevenness of the coal flow, etc., and considering the condition of the coal bunker at the working face without buffer effect (about 1.2m), the belt speed of DTII series belt conveyor should be lower than that of DTII series belt conveyor. The belt speed is 3.15m/s.
4.2.2 Calculation of belt width
1)Determine the belt width according to the conveying capacity
The relationship between the conveying capacity of the belt conveyor, the belt width and the belt speed is:
Q=KB2vγc t/h
The formula in which the belt width is 1.2m and the belt speed is 3.15m/s, is the same as that in the working face. /p>
In the formula K-cargo section coefficient, K-value and the load on the conveyor belt stacking angle (check the standard MT/T467-1996 in Table III)
B-conveyor belt width, m
V-conveyor speed, m / s
γ-Transportation of the bulk weight of the load, t/m3
C-conveyor inclination on the conveyor volume of the influence of the coefficient.
When the conveying capacity is known can be obtained according to the following formula to meet the production capacity of the required bandwidth B1:
B1 = = = 1.2
2) According to the lumpiness of the material conveyed to determine the bandwidth of B2
Because of the belt conveyor conveying raw coal, and amax = 300mm so there are:
B2 ≥ 2?amax + 200 = 2 × 200 + 200 = 800mm
B2 ≥ 2?amax +200 = 2 × 200 + 200 = 800mm
B2 ≥ 2? 200+200=800mm
The actual determination of the width B=max{1000B1, B2}, so you can choose 1200mm width conveyor belt.
4.2.3 Initial selection of conveyor belts
Currently, China produces the following types of conveyor belts: nylon layered conveyor belts, plastic conveyor belts, integral core flame retardant belts, steel wire rope core belts and so on.
The following factors should be considered in the determination of the type of conveyor belt:
1)In order to prolong the service life of the conveyor belt and reduce material wear, try to use rubber veneer, followed by rubber-plastic veneer and plastic veneer conveyor belt;
2)Under the same conditions, priority is given to the selection of the delamination of the belt, followed by the overall core and wire rope core belt;
3)Priority is given to the selection of nylon, Vinylon canvas ply belt. Because in the same tensile strength, the above materials than cotton canvas belt body light, thin, soft, into the groove of good, water and corrosion resistance;
4) cover the thickness of the rubber depends mainly on the type of material being transported and the characteristics of the size of the impact of the feed, the belt speed and the length of the machine, the conveyor charcoalite and other ores, you can be thickened by 2mm surface layer of rubber, in order to prolong the service life.
Comprehensive machine characteristics of all kinds of parameters and technical characteristics, taking into account the larger conveying capacity, longer transport distance, and for the fixed conveyor, the initial selection of conveyor belts using steel wire rope core conveyor belt, which has both good strength, but also has good anti-tear performance, is the preferred belt type of belt conveyor in the underground at present. The preliminary selection of conveyor belt is as follows:
Conveyor belt model: ST2500 conveyor belt
Belt width: 1200mm
Belt quality: qd=35.3kg/m2
4.3 Conveyor layout and determination of basic parameters
4.3.1 Conveyor belt layout
For long distance, large capacity belt conveyor with not too big angle, the belt will be used as the first choice of conveyor belt. For long-distance and large capacity belt conveyor system, the power ratio of 1:1 or 2:1 for double drums can be adopted in general, which can realize the time-sharing start of the motor (the capacity of the underground transformer substation in the coal mine is limited), and at the same time reduce the strength of the conveyor belt. In order to reduce the strength of the conveyor belt, this drive system adopts the head double roller drive, and puts the tensioning device at the back of the tightly following drive roller, which is favorable for automatic tensioning at the time of starting, and at the same time reduces the length of the electric power line laying, and ensures the control response in time. The location of the drive section arrangement has a greater impact on the strength of the conveyor belt, but for this conveyor system, after analyzing, it is concluded that the drive section is arranged in the upper part of the effect is more ideal. At the same time, following the principle of minimizing the construction workload, simplifying the equipment and reducing the production cost, its specific arrangement schematic is shown in the conveyor general assembly diagram. Considering the coal conveying quality is large, this machine all kinds of roller group spacing:
Bearing roller spacing lt'=1.2m
Return roller spacing lt"=3m
Buffer roller spacing lth=0.6m
Bearing roller diameter dt=φ133mm Gt'=34.92Kg
Return roller diameter dt'=φ133mm Gt'=34.92Kg
Return roller diameter dt'=φ133mm Gt'=34.92Kg
Return roller diameter dt'=φ133mm Gt'=34.92Kg
This machine has the following advantages. dt'=φ133mm Gt"=30.63Kg
4.3.2 Determination of basic parameters of the conveyor
1) Mass of conveyor belt qd
From the above conveyor belt selection results, it can be seen that qd=35.3kg/m2×1.2m=42.36kg/m
2) Mass of material line q
When the design conveying capacity and belt speed are known, it can be seen that qd = 35.3kg/m2×1.2m=42.36kg/m
When the When the design conveying capacity and belt speed are known, the line mass of the material is obtained by the following formula:
q= = =159kg/m
where Q-volume of transportation per hour, t/h;
v-transportation speed of the conveyor belt, m/s
3) The line mass of the rotating part of the rollers, qt′. qt″
By the aforementioned selection of the roller group can be seen
qt′= Gt'/ lt'=29.1kg/m
qt″= Gt"/ lt"=10.21 kg/m