introductory

The coal processing plant of Zizi Group Xufang Coal Mine was put into operation in 1999, with a design capacity of 1.50 Mt/a. In order to further improve the yield of smelting coal and increase the economic benefits, it was technologically upgraded in 2009, so that the processing capacity was increased to 2.10 Mt/a. The original jigging process is replaced by the heavy-medium selection, and the raw coal of 50-0.63 nun is washed by the two products of the heavy-medium cyclone, while the coarse coal slurry below 0.63mm enters into the coal slurry cyclone, the bottom flow is recycled by 0.4mm high frequency screen. Coal slurry below 0.63mm enters into the slurry cyclone, and the bottom flow passes through 0.4mm high-frequency sieve to recover the coarse slurry, and the fine slurry is finally recovered by the quick-opening diaphragm filter press.

?KZG450/ 2000-U type quick-opening diaphragm filter pressWorking Principle

The filter press is mainly composed of frame, filter plate, hydraulic station and PLC control cabinet.

The working principle is that after the filter plate and cloth are pressed, the filter slurry is pushed by the feeding pump and enters into each filter chamber through the feeding port, and the solid-liquid separation is carried out with the help of the feeding pressure, the solid stays in the filter chamber to form the cake, and the filtrate is discharged out by the liquid discharge port. Compressed air is introduced at the air inlet to press the filter cake and further reduce the moisture. After the filter plates are loosened, the rapid pulling mechanism pulls each group of filter plates in turn to achieve the final discharge. This completes the filter press cycle.

Main technical parameters

Filter area: 450 m²

Chamber volume: 9.96 m³

Number of chambers: 64

Filtrate solid content: <5 %

Cake thickness: 45 mm

Pressing pressure: 1.0 MPa

Feeding pressure: 0.5 ~0.8 MPa Wet coal slurry handling capacity: 40~55 t/h

operating effect

The main factor affecting the operational effectiveness, the influence of the feed concentration;

Data on the effect of feed concentration

subtype of experiment	Feed concentration (&/L)	Cake moisture (%)	Filtrate solids (%)	cycle time (s)
1	250	23.87	4.16	790
2	300	22.35	3.82	760
3	350	21.08	2.66	750
4	450	20.12	1.96	728
5	550	19.68	1.88	726
6	600	19.51	1.36	723

As the concentration of feed material increases, the moisture of filter cake decreases. Due to the different settling speed of particles, the average particle size of the cake decreases gradually from bottom to top, and the resistance of the cake increases gradually, which affects the dewatering of the lower layer of the cake, and this effect increases gradually with the decrease of the feed concentration; due to the increase of the concentration, the formation speed of the cake is accelerated, and the structure of the cake layer is improved. As the amount of solids carried away by the filtrate is greatest when the cake is first formed, the probability of fine particles passing through the filtration medium is reduced, thus lowering the solids content of the filtrate.

Influence of feed size

It can be understood that when the content of less than 0.074mm is greater than 55%, the cake moisture and filtrate solid content will increase significantly. The specific resistance of the cake increases because the fine particles fill in between the pores of the cake layer formed by the large particles, which makes it more difficult for the water to pass through the cake layer.

Influence data on feed size

<	0.074mm Content (%)	) Cake moisture (%)	Filtrate solid content (%)
Experiment 1	46.69	19.18	1.91
Test 2	51.39	20.01	2.03
Test III	60.27	23.89	4.18

Influence of feed ash, the higher the feed ash, the longer the single cycle time. Because of the high ash fine mud content, the amount increases, the viscosity of the slurry becomes larger, the filtration rate decreases, the time is prolonged.

Influence data on feed ash

Feed ash (%)	Single cycle time (hours)
30.02	726
31.97	750
33.38	780

(4) The feeding pressure is 0.7~0.8MPa.

economic benefit

Pu cake automatic unloading, no need to poke cake manually, reducing the post of labour. Currently, the amount of dry coal slurry is about 441,000t/a, and the moisture is reduced from 26% to 20%, then the amount of wet coal slurry is changed from 555,900t/a to 551,300t/a. Comparison of the selling price of wet coal slurry: the selling price of wet coal slurry with the moisture of 20% is 360RMB/t, and that of slurry with the moisture of 26% is 335RMB/t.

Annual economic benefits

55.13 x 360 - 55.59 x 335 = $12,241,500

Comprehensive annual economic benefits

8 +1224.15 = $123,215,000

social benefit

The amount of water lost due to the water content of coal slurry has been reduced from 144,500t/a to 110,300t/a, which saves water resources. At the same time, it improves the performance of storage, loading and transporting, and greatly improves the environment of the plant and mine.

Problems and recommendations

The content of ＞5mm in the feed is sometimes as high as 6%, which will cause the cake to be loose and accelerate the wear of the filter cloth. It is recommended to take measures such as replacing the sieve plate and adjusting the feeding pressure of the cyclone to reduce the content of 0.5mm in the heavy media selection system.

When the filtrate is not clear, the damaged filter cloth should be replaced in time, otherwise, the coal sludge will accumulate between the filter cloth and the filter plate, resulting in poor sealing of the contact surface, and the phenomenon of spraying will be very likely to occur. The concentration of feed material should be 270~450g/L, if the concentration is too low, the moisture of the filter cake will be big, and if the concentration is too high, the phenomenon of "pressure rake" of the rake-type thickener will be very likely to happen.

reach a verdict

sinceQuick-opening diaphragm filter pressesSince it has been put into operation, it has met the needs of coal washing production. Compared with plate and frame filter press, it has high production process index, PLC control, simple operation, low failure rate, stable and reliable operation, low labour intensity of workers, and is an effective and economic coal sludge dewatering equipment.