With the continuous progress of China's society and the continuous innovation of science and technology, the construction of intelligent coal preparation plant is of great strategic significance for promoting the supply-side structural reform of China's coal industry, creating new competitive advantages in coal preparation industry, and realising a strong country in science and technology.

filter pressAs the key equipment of the closed-circuit recycling system of coal slurry water in the coal preparation plant, it is now developing in the direction of large capacity and high efficiency, which mainly has the advantages of strong slurry processing capacity, large filtration area, high-pressure and strong inflow of material through multiple ports, uniform compression by multiple cylinders, fast pulling apart and unloading, and automatic control by PLC and information technology.

Current status of coal slurry water treatment

Influenced by the geological conditions of the mine, the faults in the coal seams and the rock nature of the gangue in Dongtan Coal Mine are siltstone or mudstone, which are clay minerals that are very easy to be muddied in contact with water. With the prolongation of the mining time of the mine, the high-quality coal reserves are gradually reduced, and the content of coal slurry in the raw coal is getting bigger and bigger, especially when there are faults in the underground quarry, the phenomenon of muddying of the raw coal into the washings is serious, and the content of the fine particles in the coal slurry is high (over 70% of the total amount of the coal slurry is of the order of -200 mesh). The content of fine particles in the slurry is high (-200 mesh accounts for more than 70%), which results in slow filtration speed of the slurry water and high water content of the slurry. The nature of coal slurry (high ash and fine slurry, easy to sludge, high viscosity, etc.) seriously affects the efficiency of filter press. When the coal quality of the mine is good, the circulation cycle of KM300/2000 rapid diaphragm filter press is about 15min, and when the coal quality is poor, the circulation cycle of KM300/2000 rapid diaphragm filter press is about 40min, and the efficiency of filter press is reduced by 2~3 times. When the coal slurry content of the mine is about 15%, the coal slurry water treatment has the capacity of full washing, but when the coal slurry content of some working faces of the mine is high, for example, the coal slurry content of the 3306 consolidation face is up to 25.95%, an increase of nearly 60%, and the gangue and gangue are easy to be sludged, so the treatment capacity of the existing coal slurry water filtering filter press of coal processing plant can not satisfy the requirement of raw coal being washed. When the coal quality is poor, the fine-grained slurry accumulates in the system, the concentration of circulating water and clarified water increases dramatically, the sorting efficiency of the non-pressure re-mediation system decreases, and the product quality is unstable, and when it is serious, it is necessary to take measures to reduce the production, and to implement the "water production", which affects the normal production of the whole coal washing system.

?capacity expansion and reconstruction

Coal plant filter press 615 (KM300/2000 model) has a small filter area and long feeding time. The nature of the coal slurry (high ash and fine sludge, easy to sludge, high viscosity, etc.) seriously affects the efficiency of filter press production. In addition, the filter press was put into use in April 2005, and although the main machine part has not shown any major deformation or failure, it is seriously corroded and worn out, and the hydraulic system and transmission device are often malfunctioning, so it is planned to increase the capacity of filter press 615 on the first floor of the filter press plant. It is planned to increase the capacity of filter press 615 on the second floor of the filter press plant. The capacity of the filter press will be increased through research and development and upgrading by adding special filter plates for KM-type rapid filter press, updating the technology of pulling apart the filter plates in groups for discharging, improving the technology of synchronous pressing with multiple cylinders, and improving the safety protection system of the press. After the capacity increase, the effective filtering area of the filter press for coal sludge will be increased from 300m2 to 600m2 to improve the capacity of coal sludge treatment. In order to meet the requirements of the existing filter press for processing difficult-to-filter coal sludge, the existing KM300/2000 rapid diaphragm plate and frame filter press is expanded to KM600/2000 rapid diaphragm plate and frame filter press, so as to increase the processing capacity of a single filter press to meet the production needs of the closed-circuit recycling of coal slurry system in the coal washing plant, and at the same time to avoid the large amount of manpower and material inputs brought about by the further expansion of the plant and the increase of the new equipment and system. At the same time, it avoids a large amount of manpower and material input brought by plant expansion and adding new equipment system.

Major research projects

1) Development of KM typeRapid filter pressesSpecial filter plate. The filter plate is specially designed for 1.6MPa high-pressure filter press of KM series rapid filter press. The special filter plate and diaphragm sheet are made of pure polypropylene with high thermal stability, and the fine particles are directly moulded and die-casted without any additives such as calcium carbonate and glass fibre; the filter plate adopts the design for simultaneous discharge of both dark and light streams, and the filtration surface of the special plate, the outlet holes, the integrated holes, and the angular holes are designed for fluid dynamics optimization, which ensures a decreasing hydraulics radius. The hydrodynamic radius is decreasing, so that the filtrate flow path forms an obvious and uniform pressure gradient from the inside to the outside, which can realise rapid negative pressure and high efficiency of filtration, and meanwhile, the number of filter plates of the filter press is increased from 44 to 88 to realise the expansion of the capacity of the filter press.

(2) Designing the latest filter plate pull-open discharging technology. Adopting the latest filter plate pull-open drive mechanism, changing from the existing three times group pull-open to rapid pull-open discharging in sections, with no change in the distance of pull-open of the filter plate, and at the same time, with the function of discharging with the filter plate deflection torque swinging impeller.

(3) Improve the synchronous pressing technology of multiple cylinders. Improve the technology of oil cylinder pressing and closing the filter plate group, so that the synchronisation of multiple oil cylinders in the process of pressing and loosening will be better, the failure rate will be lower, and the sealing force of the filter plate group will be sufficient during 0.8MPa high pressure feeding and 1.6MPa diaphragm pressing, so as to avoid the phenomenon of spraying caused by insufficient or deviated pressure of the oil cylinders.

(4) Improve the pressing safety protection system. Increase the hydraulic cylinder pressure loss protection procedure, through the setting of pressure sensors, automatic control programme to check the high-pressure feeding and pressing process, to avoid personnel and equipment safety problems caused by insufficient sealing force of the cylinder or hydraulic components.

Rehabilitation programme

In recent years, the development trend of the same type of diaphragm plate and frame filter press applied in the mining industry at home and abroad is large-scale and intelligent. The filtration area of a single filter press is generally above 500m2, and the filter plate size is 2×2m or 2.5×2.5m. In the iron and steel industry, the filter plate size of the iron ore filter press reaches above 3.5m. With the increase of filtering area of the filter press, the single-cycle capacity of a single filter press increases, and the automation control level of the supporting filter presses also improves significantly. The filter presses can achieve automatic operation in the whole process, and the control system of the industrial machine can monitor and record the operating parameters of the filter press in real time, thus truly realising the automation and intelligent management of industrial production. Technical cooperation with the domestic advanced filter press manufacturer, as the first manufacturer to take the lead in developing the fast-opening filter press in China, the manufacturer has advanced research results in high-strength and high-toughness filter plate and diaphragm sheet; hydraulic motor dragging system and hydraulic motor PLC automatic control system; hydraulic drive control system and transmission chain dragging new type of linkage structure puller trolley pulling open the filter plate discharging device in sections. Combining the problems of small filtering area and long filtering cycle time of the existing KM300/2000 diaphragm filter press in the coal processing plant, the project adopts the methods of technical research, on-site drawing, optimising the design layout and organising scientific research, etc., to study and determine the design scheme of the hydraulic motor-driven movable platen pulling open the filter plate to unload the material for the first time, and the drive of new type of connecting rod structure puller cart to realise the sectional automatic pulling open of the filter plate to unload the material system. Doubling the original 300m2 three times grouped opening filter press filter plate; grouped opening is changed to segmented opening, each time pulling open five filter plates to unload the cake; the original transport system, feeding system, hydraulic system, water system, piping system remain unchanged, reducing unnecessary inputs. The existing transport system, feeding system, hydraulic system, water discharge system and pipeline system remain unchanged, reducing unnecessary inputs. 44 filter plates are added to the original KM600/2000 rapid diaphragm filter press, which doubles the processing capacity of the filter press.

Key Design

(1) Adopting the main cylinder to drive 4 auxiliary cylinders to press, which can improve the action efficiency of the pressing mechanism, ensure that the sealing force of the filter plate group is sufficient, and there will not be any phenomenon of spraying material due to insufficient pressing force of the cylinders or deviation of the pressure, so as to ensure the stability and reliability of the feeding material in the production process of the filter press.

(2) The hydraulic motor drives the puller trolley through the roller chain to pull away and discharge the material in several times and the automatic programme control of the working process. Increase the design of the structure of the plate release plate in the process of pulling away the filter plate by sections driven by the pulling plate trolley.

(3) Improve the safety, reliability and service life of the multi-port feeding structure of the filter press, and on the premise of satisfying the function of multi-stage feeding, make the feeding pipe of the filter press reasonably arranged, beautiful in appearance and convenient in operation and maintenance.

(4) Add a new type of mechanical linkage type plate pulling device, and use the hydraulic motor to drag the chain plate pulling system to complete the automatic closing and pulling apart of the filter press plate for multiple discharging function.

(5) Changed to the section of fast pulling off the discharge, with the filter plate deflection torque swing impact discharge function.

(6) Adding a telescopic feed tube device to replace the existing side feed hose assembly improves the appearance of the equipment while increasing the stability and safety of the filter press operation.

(7) Increase the hydraulic cylinder pressure loss protection procedure, through the installation of pressure sensors, automatic control programme to monitor the high-pressure feeding and pressing process, to avoid the cylinder or hydraulic components sealing force is not enough to cause personnel and equipment safety problems.

Enlargement effect

After the capacity expansion of KM300/2000 rapid diaphragm plate and frame filter press, the filtration area will be increased from 300m2 to 600m2, the volume of filter chamber will be increased from 6m2 to 12m2, and the output of single cycle of filter press can be doubled. By increasing the capacity, the hourly processing capacity of the filter press is doubled, which solves the problem of difficult processing of coal slurry caused by the change of the nature of coal slurry, and meets the requirements of the overall production of the coal washing plant. At the same time, it reduces unnecessary inputs, such as plant building, receiving tank, discharging tank, feeding pump, conveyor, operation desk, pipeline and valves, and so on.

?Main technical indicators

Filtering area: 600m2 Filter plate size: 2000×2000mm Filter plate number: 88 Filter chamber depth: 40mm Filter chamber volume: 12m2 Feeding pressure: 0.8MPa (Splendid) Pressing pressure: 0.8MPa (Splendid) 2.5 Economic and Social Benefits The increase in capacity of the filter presses of the filter press plant can increase the capacity of the coal slurry water system, and increase the washing capacity of the washing system. Before the renovation, the washing system would be deteriorated due to the deterioration of the coal slurry water, fine-grained coal slurry would accumulate in the system, the concentration of circulating water and clarified water would increase dramatically, the sorting efficiency of the unpressurised re-mixing system would be lowered, and the quality of the products would be unstable, and when it was serious, it would be necessary to take measures to reduce the production. After renovation, the filtering area of 300m2/table is increased to 600m2/table, which can produce 160t of tail coal slurry per day, and the washing capacity can be increased by about 1,000t. 2,419.3 thousand tonnes of raw coal were washed in January-August 2018 before renovation, with a monthly average of 345.6 thousand tonnes, and 2,099 thousand tonnes of raw coal were washed in August-December 2018 after renovation, with a monthly average of 419.8 thousand t. The washing efficiency of one tonne of coal was RMB 115.29 yuan, with a monthly average of 349,800 yuan. Benefit of 115.29 yuan, the average monthly efficiency increase is as follows: (41.98-34.59)×115.29=8.51999 million yuan In addition, if the purchase of a KM600/2000 rapid diaphragm filter press requires about 1.5 million yuan, the transformation of the same specifications of the old filter press only requires 850,000 yuan, each unit can save filter press purchase funds of 650,000 yuan, the use of the technology for upgrading and transformation has a very high popularity. Renewal and reconstruction with this technology has very high value of popularisation and application and good economic and social benefits.

Value of promotion and application

The filter press after capacity enlargement and renovation is installed with 88 filter plates, of which 44 are diaphragm and 44 are chamber type. The total volume of filter chamber of filter plate is increased from 6m2 to 12m2, and the effective filtration area of coal slurry is increased from 300m2 to 600m2, and the amount of coal slurry handled in each filtering cycle is 15t, and the time for each filtering cycle is 20min when the quality of coal is good; and 45min when the quality of coal is poor; the filter press after capacity enlargement and development can realise all the filtering plates to be closed together and pressed tightly automatically at one time, feeding materials at multiple points, reverse blowing, secondary pressing, negative pressure and high-efficiency filtration, and liquid discharge in both open and dark flow at the same time. The developed filter press can realise automatic closing and pressing of all filter plates at one time, multi-point feeding, reverse blowing, secondary pressing, negative pressure and high-efficiency filtration, and simultaneous discharge of liquid from both open and dark flow. Comparing the diaphragm plate and frame filter press after capacity expansion and renovation with other filter presses of the same type, under the same feeding concentration and pressure, this filter press can shorten the feeding time of 25%, and the cake is not easy to stick to the filter cloth, and it can also reduce the time of discharging, lowering the staff's labour intensity, and the processing capacity of a single filter press is large, the equipment is reliable, and it is convenient to operate. After expanding the capacity of filter press, it can increase the filtration processing capacity of single filter press, improve the reliability and stability of the operation of coal washing system in coal processing plant, and also improve the modernisation level of equipment management in coal mine, which is of excellent value for popularisation and application. 20 December 2018, the project passed the acceptance of the company. The new style technology of filter press has been partially applied to other filter presses, and the coal slurry water treatment capacity is obviously improved, the operation is convenient, the reliability of the equipment is increased, and huge economic benefits can be created.