RU2450861C1 - Loose material grinder - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to grinding and sizing means to be applied in multiple branches of national economy. Proposed device comprises vacuum chamber accommodating two tapered grinding discs rotating in opposite directions and fitted on fixed spindle to form grinding zone and annular slot for discharge of finished product, initial material and air feed system communicated with grinding zone between grinding discs, and finished product discharge system. Initial material and air feed system is provided with pressure regulator and communicated via adjustable valve with aforesaid grinding zone while the device is furnished with synchroniser connected with pressure regulator and adjustable valve to equalise initial material feed rate and grinding rate.

EFFECT: synchronised feed and discharge.

4 cl, 1 dwg

Description

The invention relates to means for grinding and calibration of various materials and can find application in various fields of the national economy.

A device for grinding bulk materials containing two grinding cone-shaped discs driven in counter-rotation and mounted on two hollow cantilever shafts through the cavities of which the source material is fed into the grinding chamber is known. There are percussion elements on the inner surfaces of the disks; the finished product is released through the annular gap between the disks (see USSR author's certificate No. 1565509, publ. 05.23.1990).

Closest to the proposed invention is a device for grinding bulk materials containing two grinding cone-shaped counter-rotating disks with impact elements, a feed system of raw material and air through the cavity along the axis of the support shaft and an annular gap for the release of the finished product formed by the inner surfaces of the grinding disks, and final product reception system. Two counter-grinding grinding disks are mounted on one fixed shaft, connected to a source of compressed air and with a hopper with the source material and having a cutout in the central part for supplying the source material to the grinding zone between the disks (RF patent No. 2397021, published on 08/20/2010).

The objective of the invention is to create an equilibrium dynamic mode of supply of the source material and its grinding.

The technical result of the invention is to ensure synchronization of the feed of the starting material and grinding and removal of the product, which eliminates dusting of the product and jamming of the surfaces of the counter-rotating disks.

The specified result is achieved by the fact that in the device for grinding bulk materials containing a vacuum chamber, there are two cone-shaped grinding disks of counter-rotation mounted on a fixed shaft with the formation of a grinding zone and an annular gap for the release of the finished product and connected to the drive, the feed system material and air connected to the grinding zone between the grinding disks, and the finished product discharge system, according to the proposal, the feed material and air supply system is provided a pressure regulator and is connected to the grinding zone between the grinding disks through an adjustable valve, and the device is equipped with a synchronizer connected to the pressure regulator and an adjustable valve to ensure equality of the feed rate of the starting material and the grinding speed.

In addition, the synchronizer is preferably also associated with the drive with the ability to control the rotation speed of the grinding discs.

In this case, the outlet system of the finished product preferably contains at least one valve connected to the synchronizer with the possibility of regulating its flow area.

In addition, the vacuum chamber may be equipped with a pressure regulator associated with the synchronizer.

The invention is illustrated in the drawing.

The device for grinding bulk materials contains an active grinding block, which includes a fixed support shaft 1, which is mounted on racks 2 and on which grinding coils 3 are coaxially mounted on bearings. The parts of grinding coils 3 facing each other are cone-shaped grinding disks 4, between which is formed grinding zone and annular gap for the output of the finished product. On the inner facing each other surfaces of the grinding discs 4 applied superhard coating.

The grinding coils 3 are driven counter-clockwise by drives (not shown). The grinding unit together with the drives is mounted on the reference coordinate plate 5 inside the vacuum shell 6. On the shell 6 there is a fitting 7 for supplying air or other gas and an automatic pressure regulator 8.

The annular gap between the grinding disks 4 is covered by a hollow receiving hoop 9, mounted on a reference coordinate plate 5 and connected through valves 10 and 11 and the tube 12 with a receiving hopper 13 having an air filter 14 in the upper part.

The source material is fed into a pneumatic metering device 15 having a vacuum-tight cover 16 and a bottom 17. The pneumatic metering device 15 is connected via a fitting 18 to a compressor 19 supplying compressed air to it. The pneumatic metering device 15 through an opening in the bottom 17, an adjustable valve 20 and a tube 21 is connected to a cavity made in the support shaft 1 and communicated with the grinding zone through the hole 22. The support shaft 1 is cooled by means of grooves made in it, connected to the tubes 23.

The pneumatic doser 15 is equipped with a pressure regulator 24 connected to the synchronizer 25. The synchronizer 25 is an electronic device connected by electrical circuits to actuators, which are pressure regulators 8 and 24, valves 10, 11 and an adjustable valve 20, as well as frequency converters of electric actuators, driving the grinding coils 3 (not shown).

Thus, the adjustable values are the pressure in the pneumatic doser 15 and in the volume of the shell 6, the cross-sectional area of the valves through which the air-sand mixture passes, and the rotation speed of the grinding coils 3.

The main purpose of the synchronizer 25 is the automatic selection of these three groups of parameters for automatic coordination of the process (speed equalization) of the supply and grinding of the initial product.

The device operates as follows.

The source material is loaded into the pneumatic doser 15 and under the action of compressed air pressure through the tube 21 and the hole 22 in the support shaft 1 is fed into the grinding zone between the cone-shaped surfaces of the grinding disks 4, which are driven in counter rotation. The source material is crushed by grinding disks 4, and the finished product exits through the annular gap. The width of the slit can vary widely depending on the required grinding fineness. The finished product cannot have fineness greater than the width of the outlet slit. Preferably, the particle size distribution after passing through the annular gap has a Gaussian distribution with a maximum of about 1/10 θ, where θ is the width of the gap.

The finished product enters the receiving hoop 9 and through the valves 19 and 11 and the tube 12 into the receiving hopper 13.

The synchronizer 25, acting on the adjustable valve 29 and the pressure regulator 24, maintains the necessary overpressure in the pneumatic metering device 15, the value of which is automatically set based on the values of the width of the annular gap, the speed of the oncoming rotation of the grinding coils 3 and the size of the source material.

The use of a synchronizer 25, which controls the operation of the adjustable valve 20 and the air pressure regulator 24 in the pneumatic doser, ensures the equality of the feed rates of the source material and the grinding rate, which eliminates the accumulation of material in the grinding zone, its dusting and jamming of the grinding discs 4.

The following is an example of calculating the dynamic equilibrium during the operation of the proposed synchronous ultrafine bulk material grinder.

In the operation of any grinder, especially in the field of ultrafine grinding (<20 μm), the factor of dynamic equilibrium is very important, i.e. synchronization of feed with grinding speed. Without such equilibrium, there will be either dusting of the product or jamming of counter-rotating surfaces. Mathematically, the relation (1) must be observed

Here:

D is the diameter of the grinding disk 4 from the side facing the grinding area;

θ is the width of the outlet annular gap formed by grinding disks 4;

τ is the frequency of rotation of the drive of the grinding coils 3;

d is the diameter of the exhaust pipe 21 of the valve 20;

P is the pressure in the pneumatic doser 15 (approximately equal to the pressure in the zone of active grinding);

γ is the bulk density of the starting material (coarse sand).

In the actual design of the grinder, the parameter D is unchanged, γ is determined by the feed supplied, and θ is dictated by the required dispersion of the final product.

Thus, the parameters synchronized by the synchronizer 25 are P, d and τ.

Consider, for example, the process of producing ultrafine coal for combustion in modern state district power plants.

Bulk density of steam coal γ = 700 kg / m ³ . The required fineness of the ultrafine grinding is 15 microns. This dispersion is achieved with a gap θ = 60 μm. We take the diameter of the coil D = 0.25 m and the operating frequency of the drive τ = 200 Hz. Then the adjustable parameters will be the output diameter of the valve d and the pressure in the meter R. We calculate the diameter of the valve 20 at a pressure in the pneumatic meter 15 equal to two technical atmospheres (~ 0.2 MPa):

After substituting the above values of the parameters, we obtain d = 19.85 mm, which is quite enough for the release of coal sand from a pneumatic doser with a particle size of 3-4 mm.

Claims (4)

1. A device for grinding bulk materials, containing a vacuum chamber, two conical grinding disks of counter-rotation located in it, mounted on a fixed shaft with the formation of a grinding zone and an annular gap for the release of the finished product and connected to the drive, a feed system of raw material and air connected with a grinding zone between grinding disks, and a finished product discharge system, characterized in that the feed material and air supply system is equipped with a pressure regulator and is connected to the zone grinding between grinding disks through an adjustable valve, and the device is equipped with a synchronizer connected to a pressure regulator and an adjustable valve to ensure equality of the feed rate of the source material and the grinding speed. 2. The device according to claim 1, characterized in that the synchronizer is also associated with the drive with the ability to control the rotation speed of the grinding discs. 3. The device according to claim 1, characterized in that the exhaust system of the finished product contains at least one valve connected to the synchronizer with the possibility of regulating its flow area. 4. The device according to claim 1, characterized in that the vacuum chamber is equipped with a pressure regulator associated with the synchronizer.

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