Recently, we went to the coal preparation plant and found that black coal was accumulated in the tailings tank of TBS, and the ash content was less than 30% by visual inspection, and TBS hardly played a role. As a coking coal plant, the separation effect of coarse slime is very poor, and the loss of clean coal is shocking!
Although the separation accuracy of TBS is not high, it is not so bad. Therefore, the main points of TBS are elaborated. I hope that the friends who grasp the production can make good use of it and recycle the coal from underground as much as possible.
Under the condition that TBS separation is normal and meets the requirement of clean coal ash content (generally less than 10.5%), the ash content of tail coal is more than 50%, and that of better indexes can exceed 60% and that of especially good coal can exceed 70%. We can compare with these indicators to judge whether our own TBS is normal.
There are 4 reasons for the poor separation effect of TBS：
1. The depth and position of the densimeter inserted into the barrel are not correct
A lot of people don't pay attention to this problem. The densimeter of TBS is actually a pressure sensor, and the probe of the sensor should be at the appropriate depth of TBS. When the ash content in the lower part of the TBS is smaller than that in the lower part of the TBS, the pressure gradient of the lower part of the TBS is different. On the premise of ensuring the thickness of the bottom gangue layer (400-500mm), the probe of pressure sensor is more suitable at the position from the bottom (500-800mm).
To ensure the thickness of the gangue layer is to prevent the underflow coal from escaping, and the gangue layer also plays a role in water distribution. In addition, when the pressure sensor is in the above position, it can more sensitively monitor the change of the thickness of the gangue layer, so as to judge whether to discharge. This is also the reason for intermittent discharge.
On the contrary, the probe of some pressure sensors is too high from the bottom, which will lead to the accumulation of gangue at the bottom. When the tailings are not discharged, only the lower water supply and the upper discharge is a pipe. At the same time, the excessive thickness of gangue layer will compress the effective separation zone of TBS, resulting in too short effective separation area in TBS. In addition, with the influence of turbulence at the feeding point, the separation effect will be greatly reduced.
Some densitometers are too close to the side of TBS, and the measured pressure can not reflect the whole bed state, especially when the TBS has only one discharge port. During discharging, the one near the center of TBS is easy to be discharged, while the one on the edge is not easy to be discharged, which is similar to the discharging process of bin. When the densitometer can not detect these changes sensitively, the automatic control of TBS is relatively slow and can not provide guidance for sorting.
Based on the above analysis, we can see that the installation height and position of TBS densitometer are very important.
2. The ascending current velocity is not correct
The ascending velocity of TBS is generally between 0.003 m / s and 0.008 m / s. For coarse (0.5-1 mm) anthracite separation, the ascending water flow velocity is larger. The water velocity of coking coal with fine particle size (0.15-0.5mm) is smaller. Generally speaking, it is near 0.005m/s.
On the contrary, it is found that the ash content of TBS tail coal is low, and the coal can be washed up by increasing the ascending water flow velocity. When the water velocity exceeds the appeal range, the clean coal will run to the bottom because the bed is too thin.
Note: the coarse particles of clean coal in overflow are not washed up by the upward flow, but interfere with the exchange position of high and low density particles in the cylinder body under the condition of settlement, and the upward flow cannot be increased at will.
When the content of tail ash is too low and the water velocity is within the above range, the density setting of TBS should be preferentially adjusted.
Brief introduction to TBS principle: as shown in the above figure, the stratification of light and heavy particles is ideal when the water speed is appropriate (left picture). When the water speed is high (middle picture), the light and light particles are completely mixed. When the water speed is too high (right picture), the light particles are at the bottom.
3. Feed concentration too low
The reason why the feed of TBS needs to be classified by hydrocyclone has two functions: one is that TBS can not effectively separate the particles below 0.15mm. After these particles enter the TBS link, they will be flotation at last. The flow path is too long, which is not conducive to separation and energy saving. Second, this is the desliming of TBS before separation. Removing this part of slime is conducive to ensuring the ash content of clean coal. Too low feed concentration weakens the above two effects. This situation can be solved by adjusting the pressure of staged cyclone before TBS feeding, or changing the underflow port.
4. Overflow desliming not done well
Since the hydrocyclone can only remove about 60-70% of the fine slime, some high ash fine slime will inevitably enter the TBS, and because of its small settling speed, almost 100% of the fine slime will enter the overflow. If the sludge cannot be removed, the ash content of clean coal will exceed the standard. The overflow ash content of TBS in some coal preparation plants reaches 18%. After desliming by hydrocyclone, stack screen and Slime Centrifuge, the ash content of clean coal can reach 10.5%. Therefore, the overflow desliming of TBS should be done well.
① There are many high ash fine particles in the overflow of TBS. In order to ensure the qualified content of coarse and fine coal ash, the removal of high ash fine mud is the key.
② The TBS process should be investigated one by one along the concentrate line, instead of adjusting the rising water flow and density setting of TBS.
③ In order to understand TBS process, it is necessary to find out whether it is separation or desliming.
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