At present, the coal preparation technology of China's coal preparation plant has entered a period of rapid development. No matter from the technical innovation and research and development of coal preparation equipment, the separation process is mainly refined. According to the operation conditions of different coal preparation plants, the research and development of mature separation technology is targeted, such as coarse coal dense medium cyclone separation, slime flotation technology, etc. However, the selection direction of equipment is different from that of several different separation technologies. Although the above separation technologies are quite mature, due to high energy consumption and high cost, the use effect and frequency are not high. The introduction of interference bed separator in TBS coarse slime separation technology shows great advantages in coarse coal separation technology.
Particle Size Analysis of Raw Coal
In the first half of 2019, the coal preparation plant has completed 104% of the planned clean coal output, which has played an important role in the application of advanced TBS coarse slime separation technology. The particle size composition of raw coal in the coal preparation plant is shown in Table 1 below.
It can be seen from the data in Table 1 that the yield of raw coal is 17.96% when the particle size of raw coal is - 3mm, and the powder coal content of raw coal is 7.74% when the particle size is - 0.5mm. Therefore, it can be analyzed that the raw coal composition of a coal preparation plant is in positive proportion to its particle size. With the decrease of particle size, the raw coal composition gradually decreases, indicating that the coal in this plant is brittle and fragile.
According to the problems existing in the slurry water system of a coal preparation plant, it is mainly reflected in the following aspects: firstly, the treatment capacity of the flotation system is insufficient, the existing slime flotation effect is relatively poor, and the hydraulic classification system has the phenomenon of coarse. Among them, the specific reasons for the poor flotation effect of existing slime are mainly due to the poor coal quality of the plant in recent years, which leads to the increase of slime content. In addition, the direct use of underflow and large discharge and direct flotation without overflow are the main reasons. See balance table 2 for details.
However, in the actual process of flotation operation, due to the small particle size of raw coal, it will lead to the larger particle size of coal into the preparation, and then lead to the excessive amount of slurry, making the ash content of flotation too high, which will affect the production of clean coal in serious cases.
Application of TBS Coarse Slime Separation Technology in a Coal Preparation Plant
Working Principle of TBS Slime Separator
TBS Slime Separator is developed based on the two research results of "interference sedimentation principle and secondary flow classification principle" based on the different density of materials, combining with the relevant theories of physics. It makes the water flow rise, and can form turbulence in the separation tank. In this way, the interference settlement can be used to form the separation equipment. Due to the difference of feed density and other coefficients added to the separation equipment, the formed upward flow creates a good operation condition for the separation of particles. When the falling speed of the feed particles is equal to that of the ascending water flow, the separation bed can be formed in the lower structure of the separation equipment. When the feeding speed is less than the speed in the rising process of water flow, the particles are carried to the overflow device by the water flow, and then flow out to form the concentrate; when the feeding speed is greater than the speed in the rising process of water flow, the particles go down, and then pass through the separation bed to form tailings, which flows out from the bottom structure of the equipment, so as to achieve the efficient separation of concentrate and tailings.
Main Structure and Working Process of TBS Separation Bed
From the structural point of view, as shown in Figure 1. The structure of TBS separation bed equipment mainly includes the following parts: feed well, actuator, PID controller, overflow tank, feeding port, rising water pipe, overflow port, sensor, disturbance board, washing water distribution chamber, underflow discharge tank, etc. It can automatically adjust the density of separation and realize low-density separation. At the same time, the equipment occupies less space and has low cost.
With the help of pressure, the water flow in the separation bed generates upward water flow and enters into the pressure water tank, which can make the structure of the disturbance plate evenly distributed at the bottom of the TBS plate. When the coal material enters the separation equipment, under the dynamic action generated in the rising process of the water flow, the phenomenon of stratification begins to appear, the result of stratification is that the coarse-grained materials are concentrated in the bottom structure of the tank body, The fine particles or light particles are mainly concentrated in the upper tank. The continuous entry of materials makes the materials that meet the overflow conditions gradually flow out of the tank, and then form the concentrate; for the coarse density materials, the PID closed-loop control structure will be used to discharge from the outlet of the discharge valve, and the density sensor will be immersed in the corresponding turbulent layer, corresponding to a certain height, continuous detection will be carried out under the effect of bed density. There is mutual induction between bed density and PID closed-loop controller. When the bed density exceeds the set value, the underflow discharge valve will be passively opened to remove high-density materials, and then tailings can be obtained.
In the above work process, it is mainly affected by two factors. The first is the density of the feed. For the range of the feed particle size, it is mainly between 3 ~ 0.15mm, and the best size range is 1 ~ 0.25mm, that is, the optimal ratio of upper and lower limits of feed is 4:1. If the ratio is too large, that is, the density is too wide, it will cause tailings to pollute the clean coal, and then lose the purity of the clean coal; second, the feed concentration will also affect the separation effect of the interference bed (TBS), the influence of different feed concentration on the separation effect of TBS is shown in Table 3.
Secondly, the flow rate and flow rate will also affect the separation efficiency of the separation bed. For example, the selected water should be special water. When the concentration of the upper water is too high, it should be added appropriately and diluted with clear water. The concentration of water should be controlled at 25g / L during the rising process.
In view of the main structure and working process of TBS separator, the main process flow is "dense medium cyclone + TBS separator + flotation combined process". In this process, generally selected materials with particle size of 1 mm desliming, + 1 mm material, - 1 mm after classification treatment and underflow of 1 ~ 0.25 mm enter the TBS separator system as materials. Compared with the traditional desliming process, this process has obvious advantages, mainly reflected in reducing the amount of flotation feed, reducing the cost in the process of use, and effectively improving the efficiency of flotation, saving the use of resources, and can achieve energy saving and consumption reduction, and improve the recovery efficiency of medium in the intermediate operation process.
Benefit Analysis of TBS Separator in Application
1) For the separation of fine coal, TBS separator can realize the separation of 0.3 ~ 2mm coarse slime, and the clean coal yield can be increased by more than 0.2%. After the main structure and working process of TBS separator, the amount of clean coal selected by TBS separator can reach 1500t. Calculated by the market unit price of clean coal of 704 yuan t, the annual economic income of fine coal can reach 1.05 million yuan. From this data, it can be seen that using TBS separator to carry out clean coal separation operation can maximize the economic benefits of coal preparation plant.
2) At the same time, on the basis of increasing economic benefits, the cost can also be saved. By reducing the concentration of material flotation, 11.7g/L, the overall oil consumption can be reduced by 0.2kg/t, which can fully reduce the whole dense medium consumption by 0.8kg/t, thus effectively saving 3.35million yuan per year.
The coal preparation plant after the process transformation, pre washing mud and TBS transformation, the efficiency and effect of coal preparation have been improved, and through TBS separation, 0.3 ~ 2mm coarse slime can be recovered, thus improving the production of clean coal, and creating more economic benefits. Therefore, in the actual application process, the use of TBS separator equipment can not only save costs and improve work efficiency, but also improve the output of clean coal in the whole system, so as to increase the income.
To sum up, the coarse slime treatment process has been paid attention to in China's relevant coal preparation plants and other scientific research institutions. According to the existing coal preparation technology, combined with the use of TBS separator equipment, the system can be optimized and improved. On the basis of energy saving and consumption reduction, the overall structure and process technology can be scientifically and rationally applied, and more economic benefits can be obtained. The ultimate goal is to improve the working efficiency of the major coal preparation plants.
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