Application of deep groove belt conveyor in large inclination conveying of hydropower engineering

Belt conveyors can achieve continuous transportation of bulk materials and have advantages in energy consumption, safety, and other aspects compared to automobile and railway transportation. They are very important continuous transportation equipment. At present, there are multiple models that can adapt to the large inclination angle conveying of bulk materials. The maximum conveying inclination angle of the universal belt conveyor is 18 °~20 °, the deep groove belt conveyor is 35 ° (for conveying coal), the circular pipe belt conveyor is about 30 °, the transverse partition belt conveyor is 40 °, and the pressure belt conveyor and the wavy edge belt conveyor can reach 70 °~90 °. Due to the similarity in structure and conveyor belt between deep groove belt conveyors and general-purpose belt conveyors, if the conveying inclination angle can be met, deep groove belt conveyors are usually preferred for large inclination angle conveying. The author conducted research on the design and application of the deep groove belt conveyor for the No. 3 sand and gravel processing system of the Yebatan Hydropower Station dam project, which can provide reference for similar projects.

Application status of deep groove belt conveyors at home and abroad

It is generally believed that when transporting bulk materials, deep groove belt conveyors can achieve a larger inclination angle than conventional belt conveyors. This is because the deep groove conveyor belt exerts pressure on the material on the conveyor line, thereby increasing the friction between the material and the conveyor belt, as well as the internal friction between the materials. The Soviet Union and Japan developed this type of product earlier, and its early application in China was developed by Beijing Iron and Steel Design Institute and Northeast Electric Power Design Institute. During the "Seventh Five Year Plan" period, the Shanghai Research Institute of the Coal Science Research Institute undertook a national research project to study large angle up and down transport conveyors and carry out the series design of large angle up transport belt conveyors. At present, there are several domestic enterprises producing this type of belt conveyor. In practical applications, it is commonly used for transportation in coal mine inclined shafts. When using ordinary smooth conveyor belts, the inclination angle has reached 28 °, and when using patterned conveyor belts, it has increased to 35 °. The inclination angle of the lower transport conveyor has reached -29 °. In addition, Shenyang Crane Transport Machinery Factory and Northeastern University have developed the BY type deep groove belt conveyor series products.

There are various types of roller group structures for deep groove belt conveyors, as shown in Figure 1. The differences in the structure of the roller group are mainly reflected in the number of rollers, roller length, and groove angle. The 3-roller structure shown in Figure 1 (a) is mainly used for small bandwidth applications; The U-shaped structure in Figure 1 (b) can achieve smaller curve radii; The semi-circular roller group structure shown in Figures 1 (d), (e), and (f) is more suitable for the grooving of conveyor belts, but the maximum applicable inclination angle is smaller than the structural forms shown in Figures 1 (b) and 1 (c). These structures can be used not only for large angle conveyors, but also in flat turning belt conveyors. Figure 1 (g) shows the recommended roller group structure in the "Main Dimensions for the Layout of Roller Groups in Four roll Deep groove Belt Conveyors for Coal Mines" (unpublished), which not only avoids the problem of interference between roller arrangements, but also allows the use of roller series from general belt conveyors.

Figure 1 Structure of Deep Groove Roller Group

Deep groove belt conveyors are mainly used in coal mines. The belt conveyor of the main inclined shaft in Shiquan, Shanxi has a conveying capacity of 457 t/h, an inclination angle of 25 °, a lifting height of 516.947 m, a horizontal length of 110.219 m, a coal particle size of 0-300 mm, a belt width of 1200 mm, a belt speed of 3.15 m/s, an electric motor power of 3 × 500 kW, and uses a patterned steel wire rope core flame retardant conveyor belt ST4000; The main shaft belt conveyor of Jinling Coal Mine in Dengfeng Dengcao Group has a conveying capacity of 300 t/h, a maximum inclination angle of 31.5 °, a lifting height of 562 m, a horizontal length of 1100 m, a belt width of 1200 m, a belt speed of 2.5 m/s, and groove angle inclinations of 25 ° and 50 ° for the two middle and outer rollers, respectively. The motor power is 2 × 500 kW, and a flame retardant conveyor belt ST4000 with a patterned steel wire rope core is used.

In terms of other material transportation, the No. 1 main belt conveyor in the north block of the sand dam soil section of Kaiyang Phosphate Mine has a conveying capacity of 600 t/h, an inclination angle of 14.00 °~25.33 °, a lifting height of 292.165 m, a horizontal length of 631.912 m, ore particle size of 0-350 mm, a belt width of 1000 mm, a belt speed of 2.5 m/s, an electric motor power of 2 × 500 kW, and uses a convex patterned steel wire rope core flame-retardant conveyor belt ST2500.

In 2016, Hengyang Transport Machinery Co., Ltd. and Northeastern University jointly conducted in-depth research on the feasibility of applying deep groove belt conveyors to the problem of large inclination angle transportation of gold ores. The developed experimental prototype is shown in Figure 2, and various working conditions such as different belt speeds, different moisture contents, and different conveying capacities were tested and studied to verify that deep groove belt conveyors can achieve large inclination angle transportation of 28 ° on the premise of reaching the design conveying capacity.

Figure 2 Prototype of deep groove belt conveyor

Song Weigang and others used DEM simulation method to quantitatively analyze the maximum inclination angle of deep groove belt conveyor, and the simulation results were consistent with the actual application situation, verifying that DEM simulation method can be used to verify the large inclination angle transportation of materials.

Design of 2-Yebatan Dam Deep Groove Belt Conveyor

The excavation of the material yard for the No. 3 sand and gravel processing system of the Yebatan Hydropower Station dam project adopts the method of "vertical shaft+belt conveyor". The raw materials are vertically transported through vertical shafts and enter the coarse crushing workshop. The semi-finished aggregates after coarse crushing are transported by belt conveyors and pass through a 160 meter high slag yard slope to the semi-finished material pile of the sand and gravel system. In the initial design, the transportation from the bottom of the material yard at an elevation of 2855 to the sand and gravel system at an elevation of 3010 will use seven belt conveyors in a zigzag shape (see Figure 3), with a large number and complex operation and management.

Figure 3: Initial Design of Aggregate Belt Conveyor with "Z" Shaped Route

After consulting with experts and conducting on-site research, it was ultimately decided to use one large angle deep groove belt conveyor instead of seven universal belt conveyors. The use of a large angle deep groove belt conveyor for the transportation of semi-finished aggregates is the first of its kind in hydropower construction. To ensure the reliability of practical application, Northeastern University was commissioned to conduct DEM simulation of large angle aggregate transportation. Through expert verification, the main parameters of the aggregate Z2 belt conveyor have been determined: horizontal length of 265.6 m, lifting height of 114.4 m, inclination angle of 24.53 °, belt width of 1400 mm, and belt speed of 2.5 m/s; The density of the transported material is 1.8 t/m3, and the maximum particle size is 280 mm. According to GB/T 36698-2018 "Design and Calculation Methods for Belt Conveyors", the belt conveyor has been designed and calculated.

2.1 DEM simulation of large inclination conveying aggregates

For the problem of conveying large inclined aggregates, DEM is used for simulation, and the established simulation models correspond to belt speeds of 2.0 and 2.5 m/s. Change the feeding angle from 10 ° small to 24.53 ° large, and feed directly to the large angle. There are two situations: with and without vibration. Figure 4 shows the simulation process of small angle feeding EDEM, Figure 5 shows the simulation process of large angle feeding EDEM, and Table 1 lists the simulation results of material operating speed. Through simulation, it can be seen that all operating conditions can ensure the high angle conveying of materials, and the belt speed can be adjusted from the preliminary design of 2.0 m/s to 2.5 m/s.

Figure 4 EDEM simulation process of small inclination feeding

Figure 5: EDEM simulation process for high inclination feeding

Table 1 Simulation results of material running speed

2.2 Design calculation according to national standards

For a long time, the domestic belt conveyor industry has mostly used the calculation method of ISO 5048-1989 when designing and calculating belt conveyors. However, as this calculation method does not involve the use of a set starting acceleration or time calculation method, most of them use a set starting coefficient to calculate the tension of the conveyor belt. Therefore, designers blindly choose a starting coefficient of 1.3-1.5, resulting in excessive tension and high strength levels of the conveyor belt. The main components of the conveyor are subjected to excessive force during operation, thereby reducing its lifespan. Reference [7] specifies the calculation method for starting a belt conveyor according to motion control. The tension is calculated based on the set starting acceleration or time, and the starting coefficient is the output value. The calculated result is closer to the actual working conditions of the equipment. The tension curve of the conveyor belt under various working conditions is shown in Figure 6. Among them, 1 is the tension curve of the start-up process condition, 2 and 3 are the tension curves of the control shutdown and stable operation conditions, and 4 is the tension curve of the free shutdown condition. Table 2 compares the calculation results of different belt speed schemes. It can be seen that the total drive shaft power is basically the same under two different belt speeds; But when the belt speed is fast, the maximum tension of the conveyor belt is significantly smaller, which is beneficial for the operation of the conveyor, and the actual starting coefficient is close to 1.

Figure 6 Tension Curve of Belt Conveyor under Various Operating Conditions

Table 2 Comparison of Calculation Results for Different Belt Speed Plans

Application of 3-Yebatan Dam Deep Groove Belt Conveyor

The aggregate belt conveyor system Z2-Z8 has been adjusted to one large angle belt conveyor, saving a total of 148 tons of steel structure and 350 cubic meters of concrete, and reducing construction and installation investment by 1.26 million yuan; Compared with the bidding plan, the power has been reduced from 1716 kW to 1210 kW, resulting in a decrease of 506 kW (including the power of other equipment in the system) and a reduction of operating costs by 1.985 million yuan; The length of the belt conveyor has been shortened by 640 meters, and the equipment investment has been reduced by 1.94 million yuan. The total economic benefit of the project is about 5.185 million yuan, and the system will be debugged in June 2022. Figure 7 shows the overall system and the transportation of semi-finished aggregates after completion.

Figure 7: On site situation of the completed system

The application prospects of deep groove belt conveyors in the hydropower industry

At present, hydropower development in the middle and lower reaches of rivers such as Yunnan, Sichuan and Guizhou has been basically completed. In the next 20 years, most hydropower development will be in the upper reaches of rivers such as Xizang and Qinghai. These areas have steep mountains, inconvenient transportation, and relatively small construction sites. The use of deep groove belt conveyors for high angle transportation can achieve material climbing, mountain climbing, and crossing slag yards, greatly reducing the length of the line and minimizing site occupation. The deep groove belt conveyor is suitable for large particle materials, which can significantly reduce equipment investment and construction engineering. It can also be applied to the transportation of raw materials in multiple industries such as mining, hydropower, and cement, with a large application space and good application prospects.