A filter is a device that USES porous filter media to trap solid particles in the mixture of liquid and solid particles and realize solid and liquid separation. Filters are widely used in chemical, petroleum, pharmaceutical, light industry, food, mineral processing sand, coal and water treatment industries. A simple filter is formed by dividing the container into upper and lower cavities with filter media. The suspension is added to the upper chamber, and under the action of pressure, it enters the lower chamber through the filter medium to become filtrate. Solid particles are trapped on the surface of the filter medium to form filter residue (or filter cake). During the filtration process, the filter slag layer accumulated on the surface of the filter medium gradually thickens, and the resistance of the liquid through the filter slag layer increases accordingly, and the filtration speed decreases. When the filter chamber is full of filter residue or the filtration speed is too small, stop filtering, remove the filter residue, so that the filter medium regeneration, to complete a filtration cycle. Liquid through the filter slag layer and filter medium must overcome the resistance, so there must be a pressure difference on both sides of the filter medium, which is the driving force to achieve filtration. Increasing the pressure difference can accelerate filtration, but the deformation of particles after compression is easy to block the pores of filtration medium when the pressure difference is large, and the filtration is slowed down.
Larox_PF automatic filter press and CJzJ automatic filter press have been successfully applied in sand and stone processing industry in China. CJzj 56 automatic filter press single filter plate area of 2.56m2, single filter area of 56m2, has been successfully applied in sichuan la la copper mine, xiachun silver polymetallic mine, Inner Mongolia dongshengmiao zinc concentrate and tajikistan, and other small and medium-sized mines.
The application practice has proved that cjzj-56 automatic filter press can effectively deal with viscous refractory filter concentrate, and the filter cake moisture is significantly lower than that of vacuum filter and plate and frame filter press. However, when this type of filter press was used for tailings dewatering in a sand and stone mining plant in jilin, it was found that this kind of automatic filter press had some phenomena such as incomplete sealing, large consumption of rubber diaphragm, filter cloth and other vulnerable parts, small processing capacity and secondary increase of water, which finally led to the water in the tailings could not meet the technical requirements. Therefore, it is decided to improve the phenomenon of filter press by adding frequency converter.
Main functions and features of AMB300 inverter:
With vector control and V/F control functions; Torque automatic lifting function, low frequency and large torque output function; Built-in PID closed-loop control function; Built-in rs-485 interface, can be networked with the computer control; With a variety of protection functions (overvoltage, undervoltage, overcurrent, phase miss, overload, overheat, reverse protection, etc.). It can implement soft start and slow stop of the motor, reduce the impact of starting current on the power supply, and replace the step-down start equipment and protection equipment of the high-power motor. It is very convenient to control the positive and negative rotation of the motor, and a series of advantages such as wide range of speed regulation, high transmission efficiency and remarkable power saving.
Principle of variable frequency speed regulation of frequency converter:
The rotating magnetic field speed of induction motor: n1(r/min)=60 f/p, where: f -- power supply frequency (Hz); P -- logarithm of the magnetic pole of the motor; Motor speed n
In order to solve the above high efficiency filter press in the industrial application, this project through the filter press after the transformation of the inverter to achieve high efficiency dehydration process, filter plate sealing structure, vulnerable parts, etc. The modified automatic filter press can press and filter normally and continuously for the extremely fine and sticky materials like phosphorous tailings, and control the moisture in the range of technological indicators.
After careful observation and analysis, it is speculated that the main reason for grouting is that the filter cake has high water content and certain viscosity, so it is difficult to completely fall off from the filter cloth. At the same time, the press cloth at each spraying is badly damaged, and even if the washing time is prolonged, the effect is not obvious. Manual unloading is required, which results in increased workload of workers and difficulty in ensuring the unloading effect. Only when the tailing moisture is controlled below 13%, the filter cake viscosity will be greatly reduced, and this problem can be effectively solved.
Forced the adoption of high head big flow of pulp pump injection seal cavity, when a large number of high pressure slurry into the filter chamber, because of the filter chamber depth of 50 itll 'n, caused the rubber diaphragm instantaneous deformation is bigger, also caused the instantaneous deformation of rubber sealing surface, the compensation of the rubber ductility, easily lead to high pressure slurry from seal not introduce shotcrete.
To solve the grouting problem caused by pump pressure, the following technologies have been tried in the early stage.
First of all, choose low head is great but still flow pump, reduce the pressure of pump, and reduce the influence of pulp on rubber diaphragm deformation, but because of the pressure filter most of the filtrate discharge in the admission process, therefore, although this method can ease the shotcrete phenomenon, but the influence of the filter cake thickness, cause of filter press each cycle capacity decreased obviously and cycle time lengthen, therefore method is not suitable for industrial transformation.
Second, it is controlled by installing valves in the feed line. Lower the valve at the start of feeding, increase it gradually during the feeding process, and fully open within 30s. This measure can solve the grouting problem, but because of the valve control is more troublesome, and in the acid environment and high-speed slurry erosion, the valve is easily damaged, difficult to be used in industrial production.
Finally, the technology of frequency conversion is applied to adjust the grouting pressure curve of slurry pump. By adding a frequency converter, the initial grouting pressure is reduced, then gradually increased to o.8mpa and kept constant, and the grouting is stopped when the pressure is slightly higher. After using this method in the field, it can effectively inhibit the grouting and has no effect on the thickness of filter cake formation, and has little effect on the circulation time, so it can be successfully used in the transformation of the feeding process of filter press.
Dewatering process of automatic press a complete working process of automatic press includes: filter plate closing, feeding press, mechanical press, air drying, filter cake pulling, cake unloading, filter cloth cleaning, etc. The three processes that work on dehydration are feed pressing, mechanical pressing and air drying.
According to the data comparison, the application of frequency conversion technology can slow down the instantaneous deformation of rubber diaphragm. Because the rubber has a good extension compensation, it can also solve the influence of residual filter residue lower than Irmn thickness on the sealing surface on the spraying, so as to avoid the occurrence of spraying phenomenon to a large extent. This transformation has achieved a good effect, and also reduced the damage of the filter cloth on the sealing surface.
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