introductory

The coal preparation plant is designed to process 3 million tonnes of raw coal annually, and the main processes are lump coal heavy media tilting wheel sorting, mixed coal jigging, two-stage concentration of coal slurry water printing coarse coal slurry centrifuge recycling, and fine coal slurry filter press recycling. All the coal slurry is recycled in the plant, and the plant has maintained the closed circuit cycle of first-class washing water for many years. In recent years, after the reconstruction and expansion, the annual output of the mine has exceeded 7 million tonnes, and the raw coal washed in the coal preparation plant has also reached more than 5 million tonnes. The increase of the washing volume has increased the load of the coal slurry water treatment system, the original filter press can not meet the requirements, the coal slurry accumulation is serious, the concentration of the washing water continues to rise, once reached 200g/L, from time to time the phenomenon of production limitations, which seriously restricts the normal production of coal washing. In order to improve the capacity of coal slurry water treatment and meet the demand of coal washing production, fast-opening diaphragm filter press was installed, which greatly improved the recovery effect of fine coal slurry, and the concentration of washed water was stabilised at less than 100 g/L.

1 Raw Coal Mud Water Treatment Equipment

Status quo coal preparation plant original fine coal sludge treatment is not prepared for plate and frame filter press, the low level of automation of the equipment, poor water permeability of the filter cloth, filtration time is long, a single cycle of up to 50min or more, manual unloading efficiency is low, and labour intensity is high. The single machine handles about 6t/h of coal slurry, which cannot be recovered in time, limiting the production of coal washing.

2 fast-opening diaphragm filter press working principle and characteristics

The working cycle of fast-opening diaphragm filter press is divided into seven stages: locking of closing plate, pressing of filter plate, feeding filtration, blowing and pressing, blowing and cascading, unlocking of loosening plate, and unloading of pulling plate in groups, and the operation mode is divided into two types: manual and automatic, and can be freely switched. Quick-opening diaphragm filter press has the following features:

The head and tail plate are fed at both ends. Both ends of the feed feed fast, short filtration time, high production efficiency, coal slurry concentration of about 350g / L, a single cycle time question in 15rain or less, to deal with coal slurry 25t / h, more than three times as plate and frame filter press; feed uniformity, the filter plate inside the pressure difference is small, reducing wear and tear, and a long service life.

Multi-cylinder pressing. The movable head plate adopts five cylinders symmetrical top plate pressing, the filter plate is uniformly stressed, sealed tightly, and the filter cloth does not spray material.

Diaphragm blowing and pressing. The second pressing and dewatering of the filter cake has low moisture, good cake forming effect, shortens the filtration cycle and improves the efficiency of the equipment.

Grouped plate pulling. All the filter plate unloading is automatically pulled apart in three times, which is fast and efficient. Filter cake is automatically dislodged, reducing labour intensity.

Automatic control. Filter press adopts PLC programmable controller for programme control, the equipment is fully automated, without manual operation, safe and convenient.

Low failure rate. Filter presses are reasonably designed, reliable and have low maintenance.

(7) All pipeline control valves are all pneumatic valves, sensitive and reliable, energy saving and environmental protection.

3 Filter press applications

(1) Equipment installation.

①The installation of the two beams requires that their diagonal error, the relative height error of the centre line of the upper plane of the two beams, and the longitudinal flatness error of the beams should not exceed 5mm.

② two beams on both sides of the filter plate pulling mechanism to ensure synchronous operation, all rotating parts of the sprockets and rollers should rotate flexibly. ③ The diaphragm filter plate and chamber filter plate must be installed at intervals to ensure that no material is sprayed during feeding and filter pressing.

④ Install the unloading mechanism to ensure that its support is accurately positioned to ensure the level of the unloading beam and the parallelism of the beam.

⑤ The bolts of each part are complete and tight, and each outrigger is firmly supported with the beam.

Maintenance and use.

① Regularly check and tighten the high-pressure oil pipe joints, and replace the seals in time to prevent the hydraulic oil from leaking.

② Ensure that the filter plate roller is well lubricated to avoid the filter plate pulling inclined.

③ Hydraulic system according to the requirements of regular filtration, replacement of hydraulic oil, to ensure its clean performance.

④Electronic control system regularly check the line, test each control element to eliminate malfunction.

⑤ Rinse the filter cloth once a week to keep it clean, replace the broken filter cloth in time, and clean the filter plate filter cloth adjacent to the broken filter cloth thoroughly. ⑥ During the working period of the filter press, implement a good inspection system, and stop the machine in time when it finds faults to prevent the problem from expanding.

(7) Coal slurry concentration is controlled between 300g/L and 400g/L to ensure the efficiency of the filter press.

⑧ filter press feed pump selection slurry pump, head 60-65m, flow rate 90m3/h-120m3/h.

4 Problems and treatment

The application of fast-opening diaphragm filter press in coal preparation plant has solved the problem of low coal slurry recovery capacity to a certain extent, but there are still deficiencies in the design of individual parts of the equipment, and the efficacy of the equipment has not been brought into full play.

4.1 Filter control filter press automatic operating system original design adopts electric contact pressure gauge according to the change of feeding pressure to control the filtration time, the electric contact pressure gauge were set to the low point, high point pressure, when the feeding pressure rises to the set high point pressure, the pressure gauge to the control system signals, the feeding pump to stop, the filtration is over. Because the feeding pressure rises to the high point of the set pressure within a short time after the feeding pump starts, the coal slurry in the filter chamber is not good enough to form cakes and cannot be discharged, so it needs to be switched to manual operation and manually observe the filtrate water flow to control the filtration time. Filter press can not achieve full automation, single cycle cycle is long, artificial labour intensity increases. In order to achieve automatic operation of the filter press, it was decided to control the feed pump by detecting the change of filtrate water flow in the filter press. First, the filtrate water is gathered into the filtrate water tank, and two electrode sensors are installed in the water tank at high level and low level respectively. When the filtrate water volume is large in the early filtration stage of the filter press, the filtrate water level reaches the high set position, the electrode sensors send the detection signals to the control system of the filter press, and the PLC control system of the filter press starts the control procedure of the feeding pump; when the filtration of the filter press is near to the end, and the filtrate water volume is small, the filtrate water level reaches the When the filter press filtration is near the end and the filtrate water volume is small, the filtrate water level reaches the low setting position, the PLC control system of the filter press stops feeding pump control.

4.2 The original scheme of blowback cascade for filter press is that the high-pressure wind enters into the filter chamber through the feeding pipe of the movable head plate, the coal slurry retained in the centre hole of the filter plate is further filtered, and the filtrate water is discharged through the filtrate water pipe. Because most of the high-pressure wind has been discharged from the filtrate pipe of the filter plate in the first half of the filter chamber, the wind pressure in the second half of the filter chamber is small, and the cascade time is extended to 180s, and the coal slurry in the centre hole can not be completely discharged. This causes the filter press cycle to be long, and when unloading, the coal slurry in the centre hole falls onto the belt conveyor, causing the coal slurry to slip on the tape, and transport accidents can easily occur. Modification programme for the high-pressure wind from the movable head plate into the filter chamber blowing stream into the tail plate into the blowing stream, in front of the feed control valve in the feed pipe feeding a series of steel pipe to the filter press into the cylinder, and in the pipeline installed control valves, the valve works with the control of blowing stream of high-pressure wind control valves ~ ~ the same. When blowing cascade, the coal slurry in the centre hole of the material chamber enters into the cylinder through the connected steel pipe. When the reverse flow is changed to positive flow, the process is shortened from 180s to 10s, and the coal slurry in the centre hole is completely discharged, which eliminates the phenomenon of slurry sliding on the tape and ensures the transportation safety of the coal slurry belt conveyor. Through the above transformation, the fast-opening diaphragm filter press completely realises automatic operation, the safety performance is obviously improved, the single cycle time is shortened from 15min to 8~10min, and more than 30t of coal slurry is processed per hour, and the efficiency of the equipment is greatly improved.5 Effective Evaluation

The application of fast-opening diaphragm filter press in coal preparation plant greatly relieves the pressure of coal slurry water system, and the concentration of washing water is kept below 100g/L for a long time, which meets the needs of coal washing production. Quick-opening diaphragm filter press, as a substitute for plate and frame filter press, has a broad development prospect.

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