Where t is the time (in seconds) elapsed during the filtration phase and must be calculated in conjunction with the filter pattern. Because in a filtration cycle, the filtration process is not continuous. Therefore, its filtering time should be appropriately changed. For example, a cylindrical vacuum filter, the time required for each revolution of the drum is t c , then: β———the immersion angle of the drum in the slurry, rad; For materials with coarse or coarse particles, fine inclusions and high density, the sedimentation speed is also faster. Generally, a cylindrical filter vacuum filter should be used to rationally stratify the slurry, which can improve the production capacity of the filter. Better dehydration efficiency can be obtained. The large-tube internal filter vacuum filter has large production capacity, is technically reliable, and is easy to operate. However, such equipment is relatively complicated, high in cost, high in power consumption, high in moisture content of the filter cake, and inconvenient to replace the filter cloth. Where n--the number of filter machines, Taiwan; Deep Groove Ball Bearing Widen Series Deep Groove Ball Bearing Widen Series are the most representative and widely used. Deep groove ball bearing friction coefficient is small, the limit speed is very high, especially under the axial load a lot of high speed operation, deep groove ball bearing thrust ball bearings are more advantages than that. Roller Bearing,Ball Bearing,Speed Deep Groove Ball Bearing,Motorcycle Parts Ball Bearing NINGBO FANGXING IMPORT& EXPORT CO.,LTD. , https://www.fxbearings.com
t= ƒ · t c (18)
Wherein a cycle of operation Æ’ --- filtered fraction occupied by the phase time; for purposes of the drum, the drum is equal to Æ’ immersed portion area fraction of the slurry, namely: 
S u — the filtration area of ​​the drum immersed in the slurry, m 2 ;
S w ———The total filter area of ​​the drum, m 3 .
After thoroughly and carefully studying the properties of the slurry and preliminarily selecting the filter type, in order to more accurately select the type, specification and number of industrial filters, standard filter blades must be used to simulate the operating conditions of the industrial filter, for a certain quantity. A representative sample is tested for filtration performance to provide a basis for design calculations. If conditions permit, a more accurate measurement is made with an intermediate test machine having a filtration area of ​​0.5 to 1 m2 and a structure similar to that of the selected filter after the filter blade test. In the intermediate factory test, in addition to obtaining more precise filtration constants, reliable data on filter cake washing, removal, and media regeneration can be obtained.
The pulp used in the test should be fully representative. The initial concentration of the slurry, the composition of the solid (ie, the nature of the mineral), the composition of the particle size, the agent contained in the slurry, and the pretreatment conditions such as pH, temperature, and agitation should be consistent with the operating conditions of the industrial production. The filter cloth material, specifications and feeding method used should also conform to the actual production. The following data should be provided for the vacuum filtration test:
(1) The concentration of the ore and the particle size of the solid phase, the pH and temperature of the slurry.
(2) Vacuum of filtration or vacuum gauge pressure.
(3) The wet weight, dry weight, thickness, formation time, rinsing time, dehydration time of the filter cake, the content of soluble solid components in the filter cake, and the volume of the filter cake.
(4) The volume, volume concentration, and content of soluble solid components of the filtrate.
(5) The volume of the rinse water.
(6) The volume and velocity of the gas passing through the filter cake.
(7) Observe the formation process and state of the filter cake, filter cake discharge, filter cloth clogging and filtrate condition.
For the filtration test and the determination method of various parameters, see the relevant sections of the 22nd test technique in this manual.
After comprehensive analysis of the above test results, you can determine the type of filter, the material and specifications of the media, and other operating conditions. [next]
(III) Classification, selection and calculation of filter A Classification of filter The appearance and application of industrial filter are relatively early and there are many types. Filters can be divided into four types according to the source of the filter driving force, namely vacuum filter, filter press, magnetic filter and centrifugal filter.
With the advancement of industrial production and technology, in recent years, foreign filter machines have been developing in the direction of large-scale, and the structure of the body has been continuously improved and improved. New high-efficiency, high-yield filters such as automatic filter presses and large-disc types Filters and horizontal belt filters have emerged and applied, facilitating the development of filtration technology and equipment at a faster rate. The largest disc vacuum filter in the United States has an area of ​​400 to 800 m 2 , and the maximum size of the disc filter with a steam hood is 220 m 2 . In recent years, horizontal disc filters have also appeared, which have a large processing capacity. The filter cake has a low moisture content and is one of the better filtration equipment . The traditional cylindrical vacuum filter has also been developed to a large scale with a maximum diameter of 8.5 meters.
Our metal mine beneficiation plant filtration equipment currently used mostly cylindrical vacuum filter. Large disc, belt and rope filters have been used in recent years. The successful development of the domestic 1000 mm wide belt filter press and large automatic filter press provides a new way to solve the problem of dewatering of finely viscous materials in China. In recent years, in addition to the development of new products in China, the specifications of the original cartridge vacuum filter and the folding belt vacuum filter have been serialized and updated, and new specifications have been added; at present, 30 m 2 and 40 m 2 have been produced. The gridless filter. Magnetic filter machine is also developing, in addition to rectify the original 12 m 2 models, but added a new 8 and 20 m 2 in two sizes.
B Filter selection and calculation a Filter selection The filter is selected mainly according to the nature of the material being processed and the requirements of the product, such as the particle size characteristics of the material to be filtered, the solid content in the slurry, the density of the solid, the temperature of the slurry and Factors such as the amount of the agent, the required filter cake moisture, the quality of the filtrate, and the production scale of the concentrator (the amount of concentrate). When selecting slurry with different concentration and solid particle size, the filter selection is shown in Figure 2.
Iron ore concentrate or magnetic dewatering bulk concentrate containing a small amount of hematite, the choice of the magnetic filter. Whether it is a permanent magnet internal filter or a permanent magnet external filter vacuum filter, it can be adapted to coarse or fine particles (-0.074 mm accounted for less than 70%) and dehydrated magnet concentrate concentrate. This type of equipment has a small body, high output, and high dewatering efficiency.
For fine-adhesive materials or pulp dewatering with low density and concentration, it is advisable to use cylindrical external filter vacuum filter, disc filter, belt vacuum filter, folding belt, plain or rope vacuum filter and pressure. Filter machine.
The filter-type vacuum filter of the cylindrical external filter has a lower water content, and the filter cloth per ton of concentrate is less consumed. However, the equipment is heavy and it is troublesome to replace the filter cloth.
It is convenient to replace the filter cloth with the vertical disc vacuum filter. In the case of the same size of the body, the filtration area is about twice as large as that of the cylindrical vacuum filter. The filter cloth has a short parking time. However, the filter cake has a higher moisture content, which is about 1-2% higher than that of the drum filter.
Horizontal disc vacuum filters are mainly used for product dewatering of coarse and heavy particles, such as tungsten, tin and gold-containing minerals.
The horizontal belt vacuum filter is a filter device that has been developed and widely used in modern times. The filtration area ranges from 1 to 120 m2 , and the types and specifications are various. The adaptability of this type of equipment to the dewatering of coarse and fine-grained materials is similar to that of the cylindrical internal filtration vacuum filter. However, the structure of the device is simple, the filter cloth has a long service life, can be cleaned from both sides, has high washing efficiency, and can separate filtrates of different grades. The operation is convenient and flexible, the filtration area can be increased according to production requirements, and the production and maintenance costs are low. Large belt filter used mainly in the processing of mineral ore, smelting products and pulverized coal dewatering.
Folding belt and rope belt filter are convenient for unloading, filter cloth cleaning conditions are better, not easy to block, and filter cloth wear is less. The blast discharge facility can be eliminated to prevent the filtrate from flowing back into the filter cake. It is convenient to replace the filter cloth. The filter cake has a low water content, but the filter cloth is easy to run off and requires a higher feed concentration, otherwise the dewatering efficiency will be reduced. This type of equipment is suitable for the treatment of materials with finer particle size, low density, high viscosity and difficult to remove.
For fine granules, low density, difficult to precipitate, and low concentration slurry, in order to improve the dehydration efficiency, flocculation and concentration are usually required. The viscosity of the concentrated product is increased, and the floc contains more pore water. It is not easy to be removed by a vacuum filter. The filter press must be used to force the extrusion at a pressure higher than atmospheric pressure several times or more than ten times. Only a filter cake with a lower water content can be obtained.
The manual plate and frame filter press has intermittent operation, low output and high labor intensity, but the filter cake generation and washing time can be adjusted, the washing operation effect is good, and the water consumption is less than that of the continuously operated filter press. This type of equipment has a large footprint and is inconvenient to observe during operation. The automatic plate and frame filter press can work continuously and has high output, which can overcome the above shortcomings.
The continuous operation of the automatic filter press has a large production capacity. Among them, various pressure filters can be dehydrated by using both vacuum and pressure thrusts, and the pore water and water in the pores can be removed economically. [next]
The horizontal plate and frame automatic filter press has high filtration rate, large output, energy saving, and requires fewer operators. The largest filtration area in foreign countries is 200 m2 . The use of such equipment can save drying operations, simplify the production process and improve the environment. It is an effective equipment for dealing with fine and difficult to filter slurry. It has been widely used in industrial and mining wastewater treatment abroad. But used in metal ore dehydration is less.
Compared with the horizontal plate frame automatic filter press, the vertical plate frame automatic filter press has a high production capacity, but the large-size model has fewer models, so the number of units required is large. High infrastructure costs also result in higher infrastructure costs.
The automatic filter press has high ore pressure, requires special pressure equipment, and has many auxiliary facilities. The filter cloth works under high pressure and affects its service life.
Centrifugal filters are typically used to treat fine, difficult-to-precipitate materials such as kaolin slurry filtration and filtration of certain fines and other low-concentration slurries. The production capacity is low, the equipment is complicated, the price is high, and the dehydration of metal ore products is rarely used. The equipment has high filtration speed, high dehydration efficiency and good filtrate quality. However, the operation and maintenance of the equipment is troublesome.
b Calculation of the filter The number of the working table of the filter is generally calculated according to the production capacity per unit of filtration area. The production capacity per unit filtration area can be calculated by the theoretical formula (7) after the filtration constant is determined according to the filtration test performed on a representative material. In the absence of test data, it can be selected with reference to the actual production indicators of similar factories and mines. When calculated by the theoretical formula, due to the large number of influencing factors, the calculated production capacity per unit area is often different from the actual needs. Therefore, it should be adjusted with reference to actual production indicators. When selecting empirical data for actual production, it is important to pay attention to the indicators obtained under the same conditions as the actual operating conditions of the on-site filter. Because of the initial humidity and final humidity of the filter cake, the mineral composition and particle size characteristics of the solid material, the soluble salts and chemicals present in the slurry, the temperature of the slurry and the type of filter cloth, the working index of the filter is large. Impact.
Number of filters required:
Q—the amount of dry ore to be treated, t/h;
A—the filtration area of ​​a selected filter, m 2 ;
q———The production capacity per unit area of ​​the filter, t/(m 2 · h).
When selecting the q value, it should be noted that the data in this table is a summary of the commonly used inner filter cylinder, outer filter cylinder and disc vacuum filter using cotton filter cloth. For the selection of new filter equipment or new filter cloth such as synthetic fiber, the q value should be obtained according to the actual production mine experience data or through the filtration test.
Since the nature of the slurry used in the filtration test and the operational continuity of the filtration device are difficult to be fully consistent with industrial production, the filtration rate of the actually produced filter is often lower than the rate of the small filtration test. Especially in the range of high filtration pressures, the difference is greater. Therefore, in addition to the correct selection must first be ensured in the process design, the amplification effect must also be considered. In the absence of on-site production data, for the drum filter, when using the intermediate test device for the filtration test, the amplification design should be geometrically similar, requiring filtration in a cycle for suction filtration, washing, and draining. The mutual proportional relationship of the drum areas is equal to the experimental apparatus. At the same time, the rotational speed of the drum, the filtration rate per unit of filtration area, and all parameters of the filtration system should be kept constant, and the speed of the filter should be flexible, and the area of ​​the drum should have a 25% margin. The disadvantage of this scale-up design is that the intermediate factory test setup is not readily available and requires a large amount of slurry.
The number of filters used in the design is selected. In the absence of a concentrate concentrator, it is considered to be based on the number of stations to be calculated. The reserve factor is generally 1.2, but not less than 2 units, one for work and one for standby.