introductory

The central coal processing plant of Shuangyashan Mining Group has been technologically reformed several times, and the annual washed raw coal can reach 2.3 million tonnes. The filter press system was added, and XMZ500/1500 type chamber automatic filter press was selected to recover the flotation tailings. The chamber filter press has played a key role in the recovery of coal slurry, the closed-circuit recycling of washing water and the realisation of environmental protection, but it also has the problem of poor adaptability to the changes in the nature of the treated materials. Foreign data and production practice has proved that the fine particle content, especially the mud content (high ash) filtering time is long. This can be seen from the cake dewatering process: filter press just started dewatering, because the filter cloth near the formation of a layer of dynamic thin cake, filtrate black (containing coal particles), to be the initial formation of the cake, the filtrate becomes clear. Dewatering is to rely on this dynamic layer of filter cake, under a certain pressure, the water through the layer of filter cake discharged. If the fine-grained content of more, especially the mud content (high ash), the dynamic layer of the cake gap is small, the effect is not good, viscosity and then large, the water through the layer of cake is more difficult, the requirements of the filtering time is long; when dealing with the material size coarse, viscous, pressure is not a cake, unloading the cake is very difficult. In order to solve the former problem and take measures to improve the feed pressure, the results lead to the filter plate, filter cloth easy to damage, high operating costs. In order to solve the latter problem, a process of intercepting coarse particles in the feed material with high-frequency sieve is added before the process of recovering coal sludge by filter press, which leads to various problems such as complexity of the production process. In order to solve this problem and to improve the working efficiency of the filter press, a new generation of filter presses has been developed---Diaphragm Filter Press.

2Analysis of the working principle of chamber filter press and diaphragm filter press

(1)Chamber Filter PressHow it works

When the filter press works, all the filter plates are pressed tightly between the movable head plate and the fixed tail plate, so that the neighbouring filter plates form a sealed filter chamber around them, and the slurry is fed into by the feeding hole of the fixed tail plate. After all the chambers are filled with slurry, the filtration process begins, and the slurry is separated from the solids and liquids by the pressure of the feed pump. Solid particles remain in the filter chamber due to the blockage of the wave cloth.

Complete the dewatering process. At this time, the feeding can be stopped, the head plate is returned to its original position, and the filter plate moving device pulls the filter plates apart one after another. The filter cake is dislodged by its own weight. At this point, the filter press process is completed.

(2) The working principle of diaphragm filter presses

The main difference between diaphragm filter press and ordinary chamber filter press is that an elastic membrane is installed between the filter plate and the filter cloth. In the process of operation, when the end of the feed, high-pressure fluid medium can be injected between the filter plate and the diaphragm, at which time the whole diaphragm will bulge and press the filter cake, thus realising further dewatering of the cake, that is, press filtration.

(3) Comparison of two models of filter press process

Usually when dealing with fine particle size and viscous materials, the filtration resistance is large, and the ordinary filter plate'sfilter pressThe required constant pressure feeding filtration time is longer. The diaphragm filter press, at this time, can be appropriate to end the constant pressure into the material, switch to press filtration, with a very short press filtration time instead of the ordinary filter press longer constant pressure into the material filtration time.

When the filter press feed coarse particle size, no viscosity, filtration resistance is small, a short period of time will be basically not out of the filtrate and terminate the feed. The next operation of ordinary filter press is to pull open the head plate and filter plate to start unloading, the rate of filter cake falling off is very low, even if most of the manually poked can not fall off the whole piece, the moisture of the cake is high, and the unloading of the cake is very difficult, and even need to rinse the filter cloth before proceeding to the next cycle, which results in high manual labour intensity and long unloading time. Diaphragm-type filter press in the termination of the feed into a short period of time into the press filtration process, so that the diaphragm bulging compression of the cake for further dewatering; diaphragm bulging compaction of the cake, in the process of unloading, the cake can be basically clean, so that a short period of time to complete. Unloading process.

These are the main differences between the diaphragm-type filter press and the ordinary filter press work. These differences make the diaphragm-type filter press in the unit area processing capacity, reduce the moisture of the cake, the adaptability of the nature of the material to be processed and so on have shown remarkable results, has been widely used in the existence of solid-liquid separation of various fields. Now, the diaphragm-type filter press has been regarded as the replacement and upgrading equipment of the ordinary chamber-type filter press.

3 Technical method for the conversion of chamber filter presses into diaphragm filter presses

The filtrate through the filter cloth along the filter plate on the drainage of the early use of chamber filter press manufacturers to consider the choice of diaphragm filter press to replace the use of the chamber filter press, but one is a large investment, the second is to replace the chamber filter press will result in a loss of resources, and upgraded to replace the process of solid-liquid separation system will affect the normal operation of a series of problems.

Analysing the diaphragm-type filter press, it is only a layer of elastic membrane installed between the filter plate and the filter cloth, and injected with high-pressure fluid medium to achieve the pressing and filtering process in the operation. Then, we might as well adapt the unique technology of the diaphragm filter press to the existing chamber filter press.

There can be several technical methods of transformation: ① replace the existing ordinary filter press plate with diaphragm filter press plate, plus air supply system; ② technical modification of the existing chamber filter press plate, add diaphragm and air supply system; ③ replace the existing chamber filter press plate spacing with diaphragm filter plate.

The first method only uses the existing frame and hydraulic system, all the filter plate can not be used again, resulting in a waste of resources, and the replacement of all the filter plate investment is also large; the second method of implementation of the transformation of the cycle is long, and troublesome; the third method, only half of the filter plate into a diaphragm type filter plate, and the replacement of the filter plate as a spare part, so the investment is small, no waste of resources, it is one of the most economical and effective technology method for transforming the chamber filter press into a diaphragm type filter press. It is the most economic and effective technical method to transform the chamber filter press into diaphragm filter press. The implementation steps are: ① according to the proposed transformation of chamber filter press plate dimensions and feed holes, filtrate holes, handles, filter cloth, select the appropriate side with inflatable holes on both sides of the filtration with diaphragm filter plate, and install the filter cloth, standby; ② preparation of compressed air length of the proposed transformation of the filter press long main pipe, and in accordance with the pipe on the thickness of the two filter plates on the distance from the branch pipe; ③ intervals between lifting out of the chamber filter press on the filter plate, lifting into the above spare filter plate; ③ the filter plate, lifting into the filter plate, lifting into the filter plate, lifting into the filter plate, and then into the filter plate, and then into the filter plate, and then into the filter plate. Install the above compressed air main pipe on the side of the filter plate with inflation holes; ⑤ Connect the inflation holes on each diaphragm filter plate to the branch pipe on the compressed air main pipe with a high-pressure hose.

This completes the process of transforming the chamber filter press into a diaphragm filter press. The investment is less than half of replacing a diaphragm filter press with the same filtration area; and it can make use of the intermittent time of filter press operation and maintenance time to replace the filter plate, which can even be done without affecting the production. This technology is suitable for the early use of chamber filter press manufacturers like Shuangyashan, can bring considerable economic and social benefits for the coal plant.

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