RU2771771C1 - Hydraulic classifier for separation of suspension particles by their size - Google Patents

Abstract

FIELD: industrial equipment.

SUBSTANCE: proposed invention relates to devices for carrying out the processes of hydraulic separation of various suspensions and can be used in the food industry, for example, to separate starch suspension into fractions according to particle size. It can also be used in the chemical, petrochemical, pulp and paper, construction and other industries. The hydraulic classifier for separating suspension particles by their size consists of a nozzle and a valve for feeding the suspension, sequentially arranged deposition chambers with a conical bottom, valves for removing particles from the deposition chambers. The classifier is equipped above the deposition chambers with an inclined mesh filter partition with an angle of inclination to the horizon from 10° to 35°, performing oscillatory motion and mounted on vibration supports, walls of the deposition chambers that have the ability to change the angle of inclination to the horizon in the range from 25° to 155°.

EFFECT: increase in the efficiency of classification of suspension particles by their size, as well as the productivity of the classification process.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to devices for carrying out hydraulic separation processes of various suspensions and can be used in the food industry, for example, for separating a starch suspension into fractions according to particle size.

The invention can also find application in the chemical, petrochemical, pulp and paper, construction and other industries.

Known hydraulic classifier, including a housing with a cylindrical chamber and a conical bottom, located in the lower part of the housing pipe for supplying pulp and pipe for unloading sand, pipe for water supply installed in the upper part of the housing drain chute and a sealed casing with a pipe for air outlet [Author's USSR certificate No. 1351674, class. B 03 B 5/62, 1986].

The disadvantage of this hydraulic classifier is associated with the lack of structural elements in it that allow you to adjust the quality of the classification.

Known hydraulic classifier, including a housing with a cylindrical chamber and a conical bottom, located in the lower part of the housing pipe for supplying pulp and pipe for unloading sand, tangential pipes for supplying water to the middle part of the housing, installed in the upper part of the housing drain chute and pipe for air exhaust cylindrical rings located coaxially inside the body with diameters decreasing from top to bottom, installed inside the body radially of a plate, a conical shell located in the lower part of the body, a cylinder installed coaxially with it in the upper part of the body with a sealed casing above the cylinder and with a gap located inside the cylinder coaxially with it a parabolic reflector, its part open facing the pulp inlet, the air outlet is located in the upper part of the sealed casing [Patent of the Russian Federation No. 2029625, cl. B 03 B 5/62, 1989, bul. No. 6, 1995].

The disadvantage of this hydraulic classifier, as well as [1], is the lack of structural elements in it that allow you to adjust the quality of the classification.

The closest to the proposed device in terms of technical essence and the achieved result is a multi-section hydraulic classifier [Kalinkin, I.P. New reference book of a chemist and technologist / I.P. Kalinkin. - M .: ANO NPO "Mir and Family". - T. 2. - 2006] - a prototype containing a body, chambers, mixers, unloader and drive.

In this device, the efficiency of the process is increased by the use of several pyramidal chambers, increasing in size from the place of loading of the source material to the overflow threshold. The lower part of each chamber consists of three parts: a cylindrical part for mixing the pulp, in the lower part turning into a truncated cone, as a result of which cramped conditions are created; a glass cylindrical chamber for monitoring and regulating the classification process; and an injection pipe having a spiral shape inside, through which water enters tangentially. Below the injection pipe there is a receiver for unloading the settled material, which is unloaded through an opening periodically opened by means of a ball valve fixed on the rod. However, the installation also lacks a structural element that allows you to adjust the quality of the classification.

To improve the performance of the classification process and carry out deep processing for the separation of native starch suspension particles by size, it is recommended to create a hydraulic classifier for separating suspension particles by size, which will improve the quality of the suspension being separated.

Thus, the technical problem to be solved by this invention is to increase the efficiency of classifying particles of suspensions by their size through the use of an inclined mesh filter partition above the sedimentation chambers, the presence of walls in the sedimentation chambers with the possibility of changing the angle of inclination, which makes it possible to adjust particle sizes by fractions , based on the conditions of their fallout.

частиц требуемого размера в соответствии с уравнением: The solution of the technical problem is achieved by the fact that the hydraulic classifier for separating particles of suspensions according to their size, consisting of a branch pipe and a valve for supplying a suspension, successively arranged sedimentation chambers with a conical bottom, valves for removing particles from the sedimentation chambers, is characterized in that it is equipped with an inclined mesh filter a partition with an inclination angle to the horizon from 10° to 35°, which makes an oscillatory movement and is mounted on vibration mounts, the walls of the sedimentation chambers, which have the ability to change the angle of inclination to the horizon in the range from 25° to 155°, which allows you to adjust the length of the sedimentation section

particles of the required size in accordance with the equation:

, (1)

, (one)

where V _d - the speed of movement of particles of starch suspension, m / s ;

Voc _i – settling speed of particles of the i -th size, m/s ;

h _i is the height of the liquid above the wall of the i -th receiving chamber, m .

Suspension (from late Latin suspensio - suspension) is a dispersed system in which the dispersed phase is solid particles in suspension, and the dispersed medium is liquid.

The starch suspension to be separated is a suspension with a temperature of 45–50°C and a content of 28–32% solids [Zhuzhikov, V.A. Filtration. Theory and practice of separation of suspensions / V.A. Zhuzhikov. - M.: Chemistry - 1971. - 440 p.].

At the initial stage, in order to separate the largest granules of the starch suspension, a mesh filter partition is installed in the hydraulic classifier. The main quantity characterizing the process of separation of suspension particles by size is the speed, i.e. the amount of product that has passed per unit of time through a unit area of the surface of the mesh partition. This speed is directly proportional to the pressure difference of the product during separation and inversely proportional to the viscosity of the filtrate and the total resistance of the sediment and the filter wall. In differential form, this is equal to:

, (2)

, (2)

where W is the separation rate, m ³ /m ² s ;

V is the volume ^of the filtrate, m3 ;

S is ^the separation surface area, m2 ;

τ is the separation time, s ;

ΔP - pressure difference, N / m ² (Pa) ;

µ is the viscosity of the filtrate, n.s./m ² (Pa s) ;

Roc is the _sediment layer resistance, m – ¹ ;

R _avg. is the resistance of the filtering partition, m – ¹ .

, (3)

, (3)

where r _o is the specific volume resistance of the sediment (resistance to the flow of the filtrate by a uniform layer of sediment 1 m thick), m – ² ;

x _o is the ratio of sediment and filtrate volumes.

Thus, the driving force of the process is the pressure difference of the product on both sides of the sieve filter wall.

The viscosity of the liquid phase of the suspension has a great influence on the separation rate. In addition, it is important to take into account the shape of the cells of the mesh partition. As is known, starch suspension contains particles of native starch. The main structural characteristic of the structure of native starch, which determines its physicochemical properties, is a starch grain (granule). A wide variety of forms of starch grains has been revealed. Starch grains of regular and irregular oval, round, polyhedral shape were identified.

The fineness of the separation is determined by the size of the cell and the shape of the grid. It is also important to consider the material of manufacture of such partitions. In the food industry, when classifying starch slurry, plastic filter membranes are the most corrosion-resistant and safe. Typically, the separation fineness of plastic partitions is about 50 µm. Mesh filter elements are often made multilayer, which somewhat increases the fineness and efficiency of cleaning, but leads to an increase in the hydraulic resistance of the filter element in proportion to the number of mesh layers.

The structure of the precipitate formed during filtration and, consequently, its resistance to liquid flow depend on the properties of the solid particles and the liquid phase of the suspension, on the separation conditions.

The proposed names of groups of fractions of starch granules of native starch, according to [Litvyak, V.V. Specifications: TU BY 190239501.924-2019 "Native starch, classified by granule size" / V.V. Litvyak, A.A. Zabolotets // RUE "Scientific and Practical Center of the National Academy of Sciences of Belarus for Food". Minsk, 2019. - 16 p. - State registration No. 054974 dated January 23, 2019] in accordance with the size of the fraction are given in table 1.

Table 1
Characteristics of the fraction of native starch granules Number of starch fraction Name of starch fraction Size of starch granules, microns (0) "Maximus" 150–200 (one) "Maxi" 100–150 (2) "Pioneer" 50–100 (3) "Superior" 30–50 (4) "Prima" 20–30 (5) "Second" 10–20 (6) "Waste" <10

The initial stage of the classification of native starch granules by size is the use of an inclined mesh filter partition to isolate the starch fraction (0) - "Maximus" with a granule size of 150–200 microns. To isolate starch fractions: fractions (1) - "Maxi", fractions (2) - "Pioneer", fractions (3) - "Superior", fractions (4) - "Prima", fractions (5) - "Second", fraction (6) - "Waste" the settling method is used.

Settling is a special case of separation of inhomogeneous liquid or gaseous systems as a result of the release of solid or liquid particles under the action of gravitational force. In this connection, the following conditions must be met during settling:

1) the residence time of the separated stream in the device must be equal to or greater than the particle settling time, in order to create conditions for the starch suspension granules to stand out and settle in the installation;

2) the linear flow rate must be less than the settling rate to prevent the creation of vortex flows, which are stirred up and carried away by the settling particles from the classifier.

In FIG. 1 schematically shows a hydraulic classifier for separating slurry particles according to their size.

The hydraulic classifier contains a valve 1 and a branch pipe 2 for supplying the suspension to the pre-separation zone, an inclined mesh filter partition 3 with an inclination angle α to the horizon from 10° to 35°, equipped with a vibration device 4 . The filtering partition 3 has the ability to create oscillatory movements due to vibration mounts 5 . Vibration in combination with the slope of the filter wall surface allows you to speed up the filtration process and organize the removal of sediment from the surface of the wall, and also prevents clogging of the suspension particles of the filter wall. Consecutive settling chambers 6, 7, 8, 9, 10 have a conical bottom and walls with the possibility of changing the angle of inclination β to the horizon in the range from 25° to 155°. The value of the angle of inclination is related to the coefficient of friction of starch particles on the surface of the partitions. When the angle of inclination β is set to less than 25° or more than 155°, the particles will be decelerated on the surface of the partitions and are poorly removed from the respective chambers. The bottom of the settling chambers is equipped with outlet valves 11, 12, 3, 14, 15 for discharging particles into trays 16, 17, 18, 19, 20, respectively. The valve 21 allows the discharge of the supernatant containing the smallest starch particles at the end of the precipitation process.

In FIG. 2 shows various possible options for the shape of the cells of the mesh filter partition:

- fig. 2 a - in the form of a square;

- fig. 2 b - in the form of a circle;

- fig. 2 c - in the form of a parallelogram;

- fig. 2 s - in the form of a rhombus.

Hydraulic classifier for particle size separation of suspensions works as follows.

The initial suspension containing starch granules of various sizes and shapes, by opening the valve 1 , is fed under the required pressure through the nozzle 2 to the inclined mesh filtering partition 3 with an inclination angle α to the horizon from 10° to 35°. The filtering partition makes oscillatory movements due to the presence of a vibration device 4 and vibration mounts 5. to prevent it from being clogged with suspension particles. Vibration in combination with the slope of the filter wall surface allows you to speed up the filtration process and organize the removal of sediment from the surface of the wall, and also prevents clogging of the suspension particles of the filter wall. After the initial separation of the suspension using a mesh filtering partition, the largest starch granules of the fraction (0) - "Maximus" with a size of 150 to 200 microns are separated.

частиц требуемого размера в соответствии с уравнением (1):Next, the filtered suspension enters successive settling chambers6, 7, 8, 9, 10, having a conical bottom and walls with the possibility of changing the angle of inclination β to the horizon in the range from 25° to 155°, which allows you to adjust the length of the sedimentation area

particles of the required size in accordance with equation (1):

, где

, where

V _d - the speed of movement of particles of starch suspension, m / s ;

Voc _i – settling speed of particles of the i -th size, m/s ;

h _i is the height of the liquid above the wall of the i -th receiving chamber, m.

,

,

,

) меняет длину участка осаждения

,

,

,

и

соответственно. Each deposition chamber, depending on the angle of inclination of the wall (

,

,

,

) changes the length of the deposition area

,

,

,

and

respectively.

Thus, each of the chambers of the hydraulic classifier will allow obtaining a certain size of starch fractions: chamber 1 - fractions (1) - "Maxi" with a granule size of 100-150 microns, chamber 2 - fractions (2) "Pioneer" with a granule size of 50-100 µm, chamber 3 - fractions (3) "Superior" with a granule size of 30-50 µm, chamber 4 - fractions (4) "Prima" with a granule size of 20-30 µm, chamber 5 - fractions (5) "Second" with a size granules 10-20 microns. The supernatant containing the smallest particles of starch after settling through the nozzle and valve 21 is removed from the device, which makes it possible to obtain a fraction (6) "Waste" with a granule size of less than 10 microns.

The value of the angle of inclination is related to the coefficient of friction of starch particles on the surface of the partitions. When the angle of inclination β is set to less than 25° or more than 155°, the particles will be decelerated on the surface of the partitions and are poorly removed from the respective chambers. And the ability to control the position of the walls will allow you to remove fractions of uniform particle size from the classifier and adjust the classifier when working with different productivity and concentration of starch suspension.

Upon completion of the settling process, the sediment is discharged through the outlet valves 11, 12, 13, 14, 15 into trays 16, 17, 18, 19, 20, respectively. Each obtained starch fraction is placed in a separate successive tray.

Thus, the proposed invention will improve the performance of the process of classifying suspension particles according to their size into fractions, to produce a deep separation of the starch suspension (starch granules) by particle size.

Claims (5)

Hydraulic classifier for separating particles of suspensions according to their size, consisting of a branch pipe and a valve for supplying a suspension, successively arranged settling chambers with a conical bottom, valves for removing particles from the settling chambers, characterized in that it is equipped above the settling chambers with an inclined mesh filter partition with an angle of inclination to the horizon from 10° to 35°, oscillating and mounted on vibration mounts, by the walls of the sedimentation chambers, which have the ability to change the angle of inclination to the horizon in the range from 25° to 155°, which allows you to adjust the length of the sedimentation area

particles of the required size in accordance with the equation:

, where V _d - the speed of movement of particles of starch suspension, m / s ; Voc _i – settling speed of particles of the i -th size, m/s ; h _i is the height of the liquid above the wall of the i -th receiving chamber, m .

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