RU2106605C1 - Method of dosing of loose materials by means of valve-type devices with continuous delivery of compressed gas into dosing apparatus cavity above valve - Google Patents

Abstract

FIELD: dosing of loose materials. SUBSTANCE: method consists in constant delivery of compressed gas into dosing apparatus cavity under valve at fixed excess pressure, formation of portion of product stabilized by mess, which is removed after valve operation, and formation of next portion of product for removal in one action of valve operation together with removal of preceding portion of product due to abrupt drop of pressure in dosing apparatus cavity. EFFECT: more effective dosing. 2 dwg

Description

 The invention can be used to organize high-precision automatic dosing of finely divided bulk materials, including those with significant caking, in the food, pharmaceutical, chemical industries, as well as in remote-serviced nuclear fuel cycle technologies.

 The most important goal in organizing the dispensing of bulk materials is to ensure the uniformity of their supply to subsequent stages of technological processes. The solution to this problem is often difficult due to poor flowability of the dosed product due to caking and a tendency to clumping or arching. To overcome these factors, loosening devices of various designs are used.

 The main effect on the material is either by rotating inside it the inducers installed in the dispenser housing, or by shaking, or by vibration of the walls. Various types of mechanical disintegrants, agitators, and other similar devices, as well as vibration exciters, are described in detail in the literature (Orlov S.P. Dosing devices. - M .: MashGiz, 1960; Orlov S.P., Mikhailovsky S.S., Timofeev K. K. Scales and dispensers. - M.: Mechanical Engineering, 1972).

 In some cases, for example, when dosing special products (food, pharmaceutical, nuclear), when mechanical devices in the backfill area are undesirable: maintenance is difficult, lubrication is unacceptable, etc., pneumatic methods of breaking the roof and feeding materials are preferable.

 However, in the public literature there is a small amount of information on this issue. Basically, this is the use in large-sized installations of directed jets of compressed air for pneumatic collapse of vaults (description of installations for dosing coal in “Dosing devices" by S. P. Orlov, p. 30).

 In such designs, compressed air flows cause atomization and material loss. In addition, compressed air is used exclusively for the directional destruction of the vaults and is not the carrier of the dosed product, thus, the delivery of material from the dispenser and the organization of its collapse in the hopper of the dispenser are two separate processes.

 The following inventions are considered as analogues of the proposed dosing method.

 Dispenser for fine materials [1], in which the material is in the hopper in a fluidized state due to the flow of compressed air. Dosing of the product is carried out by pumping the gas-dust mixture from the hopper into the metering chamber in which the vacuum is created, followed by the release of material from it with increasing pressure after disconnecting from the hopper. This design provides high metering accuracy.

 However, the known design is intended for a very narrow circle of fine powders with a low specific gravity. In addition, dosing in this case is carried out in two separate sequential stages: first, a dose of material is formed, and then it is dispensed. The disadvantage of this design is also that to maintain a fluidized bed in the hopper of the dispenser requires significant gas flow, as well as a filter system for its continuous removal.

 A powder batcher [2], in which the material in the hopper is loosened during the reciprocating movements of a mechanical baking powder mounted along the entire height of the hopper, as well as during the periodic supply of compressed air through the walls of the metering needle located along the axis of the hopper and introduced through the top cover to the very its bottom. Compressed air is fed alternately into the dispenser in two directions: either into the hopper cavity through a metering needle for loosening and for squeezing out a dose of material into the transport pipeline, or into the pipeline for transporting the dispensed portion. Thus, dosing also occurs in two separate consecutive stages.

 The disadvantages of this design include its high complexity and the presence of a mechanical cultivator in the cavity of the dispenser, which imposes certain restrictions on its scope.

 As the closest analogue of the proposed dispensing method, a device for feeding fine-grained material [3] is considered, where gas is a breaker of compilation in the starting material and a carrier of a dose of material with the latter being supplied as a part of the gas-dust mixture to a constant total gas flow in the transport pipeline, i.e. pneumatic transport is being implemented. Destruction of arch formation in the metering hopper is carried out by specially organized additional gas flows above the closed valve.

The disadvantages of this design include
the impossibility of forming and issuing a fixed localized portion of the dosed material, since the dosing regime in this case is implemented as a uniform supply of the dosed material (here the product flow rate per unit time is normalized);
the need to ensure and manage complex gas flows.

 Overcome the disadvantages of the described designs of dispensers while maintaining a sufficiently high metering accuracy as the issuance of fixed portions of material allows the proposed method of dispensing.

 The invention allows to solve the problem of uniform batch dosing of finely dispersed materials with different (including unsatisfactory) flowability, provides the ability to organize automated and remotely controlled processes.

 The essence of the proposed method of dispensing bulk materials is to use a sealed valve-type dispenser with a constant supply of compressed gas with a fixed excess pressure into the dispenser cavity above the valve.

 The product layer in the metering hopper is under pressure.

 At the moment of short-term valve actuation, the compressed gas saturating the dosed material layer carries out the dose of the product. The value of this dose depends on the effective cross section of the valve outlet, the characteristics of the material itself (flowability, bulk and specific gravity) and the duration of the valve opening cycle and does not depend on the excess pressure of the supplying compressed gas exceeding a certain limiting value p determined experimentally in each case .

 In addition, due to the sudden drop in pressure in the dispenser cavity when the valve is triggered, which causes the collapse of the arches of the dosed product, a new portion of material is formed at the moment the valve is closed, ready to be dispensed in the next valve actuation.

 The absence of any gas movement in the dispenser cavity in the closed valve mode is also significant.

 The proposed dispensing method combines in one act the delivery of a portion of the dosed material with the simultaneous formation of the next portion, this eliminates the use of variable modes of compressed gas supply, which simplifies the process and increases the uniformity of dispensing, and, therefore, increases the reliability of the equipment.

 The advantages of the proposed method also include the absence of the need for any mechanical baking powder.

 The proposed method for dispensing bulk materials is implemented in the following design (Fig. 1): valve-type dispenser, consisting of a hopper 1 with a sealed stopper 2 for loading the product, valve body 3 with guides 4, valve 5 pressed to the body by springs 6, electromagnetic coil 7 with a movable core 8 mounted on the springs 9, a fitting 10 for supplying compressed gas to the dispenser cavity.

 Example. Tests were carried out with a dispenser of this design (drawing N 9B. 1739.000.00, manufactured at the SSC RIAR) for dosing a simulating material with unsatisfactory flowability - 600 grade cement - with and without compressed gas supply above the valve. The load was 2.0 kg.

Dosage regimen:
interval between valve actuation 2.7 s;
time to dispense a portion of the product 0.3 s;
one dosing cycle was five valve operations, after which the dosed product was weighed on a VLKT-500 balance;
compressed gas supply to the dispenser cavity with an overpressure of 40 mm of water. Art. that amounted to a gas flow rate of 20 l / h

 1) The valve is closed. No gas or product movement occurs. All material is saturated with gas with overpressure P.

 2) The moment of opening the valve. A portion of the dosed material is pushed out of the dispenser cavity by excessive gas pressure together with a small portion of gas. At the same time, due to an abrupt drop in pressure in the layer of gas-saturated material, its arches collapse in the metering hopper.

 3) The moment of closing the valve. Over the closing valve, the next portion of the dosed material is formed from the crumbling destroyed arches of this material. At the moment the valve is completely closed, any movement of material and gas ceases, the pressure in the dispenser cavity becomes the standard statistical P. The dispenser is set to the position in step 1 and is ready for a new valve actuation.

 The test results of the dispenser without gas supply above the valve (1) and with gas supply (2) are presented in FIG. 2.

 The dosing schedules presented above confirm the advantages of introducing compressed gas over the dosing valve and, accordingly, saturating it with the entire layer of the dosed material in the dosing hopper, since this ensures stabilization of the dispensing of the dosed product and also causes a significant increase in the dosing performance.

Claims (1)

 A method of dispensing bulk materials in a valve-type dispenser, which consists in continuously supplying compressed gas with a fixed overpressure to the dispenser cavity above the valve, forming a mass-stabilized portion of the product that is discharged when the valve is triggered, forming the next portion of the product for its removal, different the fact that the next portion of the product is formed for its removal in one act of valve actuation along with the removal of the previous portion of the product due to a step-like pressure drop in the cavity to congestion.

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