DE8701970U1 - Device for pneumatic conveying of bulk materials with dosing option - Google Patents

Description

- 1 Description

Device for pneumatic conveying of bulk materials with dosing option

The invention relates to the pneumatic transport of dusty or granular bulk materials through conveying lines with dosing options. The arrangement and design of the two injectors at the beginning and end of the conveying line significantly reduces the risk of blockages with difficult materials, while at the same time allowing controlled dosing. It is also possible to convey to receivers that have too high a back pressure for injection conveying processes according to previous designs. The dosing option is guaranteed by a low-wear process. The reliability of the conveying and dosing is particularly pronounced.

The pneumatic conveying of bulk materials using the injection conveying technique has been known for a long time. Usually, low nozzle pre-pressures are used. The conveying gas pressure is generated using fans or side-channel compressors. In the usual technique, the injector is placed at the beginning of the conveying line and the conveying movement in the conveying line is set in motion by the combined suction and pressure effect of the jet.

Dosing is already carried out in a variety of ways, e.g. with valves or components that act like valves, whereby volumetric or gravimetric dosing is possible.

The injector conveying system with the injector positioned at the beginning of the line must be designed so that the internal resistance of the conveying line does not exceed the conveying pressure generated by the injector. With long conveying paths, this leads to increased line cross-sections, which also results in an increase in the required conveying gas quantity. The risk of blockage is particularly high when conveying

difficult dust-like substances to an increased extent and increases even further if there is a counterpressure in the receiver. Often the necessary increase in the conveying gas quantity, which is carried out in such cases to reduce the susceptibility to interference, is not compatible on the receiver side.

The dosing valves or valve-like dosing units used to date, e.g. rotary valves, dosing screws, perforated disks, etc., are highly susceptible to wear, with dosing accuracy decreasing with increasing wear. In addition, there are problems with various dosing arrangements in sufficiently fluidizing the material to be conveyed within the dosing device, which is also a significant source of disruption. All efforts made to date to eliminate these disadvantages have led to significantly more expensive and often complex, failure-prone designs and processes. The existing technologies are often unsuitable for use in systems that require a long service life with the greatest possible reliability of conveying or dosing, especially when conveying difficult materials, which also include highly abrasive materials.

The invention is based on the task of providing a pneumatic conveying device for dusty and granular bulk materials in which the disadvantages described are completely or largely eliminated. Particular emphasis is placed on maximum reliability and service life. The dosing accuracy does not necessarily have to reach maximum values with volumetric dosing. The process should be able to be carried out using simple means and with as little effort as possible for the required control. When dosing with the help of dosing valves, the valve design should also offer maximum reliability with the greatest possible resistance to wear.

The device should also be able to function without pressure vessel transport.

This object is achieved in a generic device by the characterizing features of claims 1-3. A reduction in the required gas quantity

Safe material transport is achieved by using relatively small pipe diameters, e.g. plastic hoses, as conveyor lines. The injector nozzles only have small diameters.

C 10 with the highest possible conveying gas pressure. With this arrangement, a very high suction can be generated in the conveying line, especially if the injector at the end of the line is correctly designed, which reduces the risk of blockages in the long term. Since the injector at the end of the line delivers directly into the receiver, a significantly higher counterpressure can be overcome than was previously usual with injector conveying. When cross-linked plastic hoses are used as the conveying line, the susceptibility to wear, even with abrasive materials, is significantly reduced.

The injectors themselves are subject to only minimal wear if the material is chosen sensibly. If metering is carried out using valves, the metering accuracy increases. The use of linearly moving tappet valves, e.g. as

Poppet valve, significantly reduces wear

susceptibility. In the further development of the invention, the use of a valve with a linearly moving drive rod is described, in which the head of the drive rod is designed in such a way that on the one hand it accommodates the injection nozzle and on the other hand it ensures closure when pressed against the valve seat, which is formed by the collecting nozzle.

Since the material is only available without pressure, no increased requirements are placed on the sealing, so that a simple, inexpensive design is sufficient. The dosing option created in this way, a valve integrated in the injector, works with considerably greater accuracy than dosing with the help of a changed nozzle pressure. The linearly moving drive rod is subject to only minor

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which are based on rotating parts within the bulk material flow, e.g. ball valves, perforated disks, etc. For dosing, only the opening and closing phases need to be controlled. A large number of such valves can be connected to a control unit. If pneumatic cylinders with a hollow piston rod are used for the drive, the entire conveying process, including dosing, can be carried out using a purely pneumatic control system. There are particular advantages in areas at risk of explosion. The reliability of pneumatic controls, especially when using control air above 2.5 bar, is well known.

A high level of dosing accuracy can be achieved by using electronic or pneumatic weighing systems, whereby the opening and closing phases of the dosing valves are controlled via an electronic control system.

&iacgr; ) A particular advantage of the device is that when using a high nozzle pre-pressure with conveying lines of correspondingly small diameters, a large number of lines can be arranged directly on the bottom of a silo. This means that, for example, in the case of flue gas desulfurization with dry additives, the required lime powder can be blown directly from the silo into the steam generator via many lines that are necessary for good distribution in the receiver. The same applies, for example, to blowing coal dust into cupola furnaces - and other types of application.

A corresponding arrangement using low pressure is possible at any time. However, the necessary enlargement of the pipe cross-sections, valves, etc. lead to higher system costs. The possible number of pipes leading directly from the silo base is also reduced by the necessary enlargement of the injection housing.

The functional principle is shown in the drawing. Shown are:

Fig. 1: Principle of conveying with 1 injector at the beginning and at the end of a conveying line

Fig. 2: Injector at the beginning of the line with upstream dosing unit or controlled valve

Fig. 3 + 4: Injector with integrated dosing valve Key to symbols:

1 = delivery line

2 = pre-fluidized bulk material

3 = Injector nozzle at the beginning of the delivery line

4 = Delivery gas pressure of the injector at the beginning of the line 5 = - " - -"- -"- " End of the line

6 = Injector nozzle at the end of the delivery line

7 = Dosing unit or controlled valve

8 = hollow piston rod

9 = Piston rod end, e.g. with valve plate or plunger

10 = inner part of the collecting nozzle designed as a valve seat

det

11 &xgr; Catch nozzle

12 = Piston rod drive

13 Direction of the jet stream

Claims (1)

Protection claims * 1. Device for pneumatic conveying of dusty or granular bulk materials with dosing option characterized in that at the beginning and at the end of a delivery line (1) an injector according to the Injection conveying principle is arranged, whereby the injector located at the end of the line ensures a constant suction in the conveying line (1), which mainly causes the conveying, while the injector at the &zgr;\ 10 injector located at the beginning of the delivery line (1) ^; · is designed so that a maximum of only so much material] (2) can be sucked in as corresponds to the performance of the conveyor line (1) for blockage-free material transport, whereby the injection nozzle (3), the conveying gas pressure (4) and the conveying gas quantity are designed in such a way that the gas quantity required for conveying and the fluidization of the material during transport through the conveyor line (1) is ensured and dosing is possible by changing the gas pressure at the upper injector nozzle (3) or both injector nozzles (3,6). ( ) 2. Device according to claim 1 characterized in that both injectors operate with a constant gas pre-pressure (4,5) and the material metering is carried out by an upstream metering unit or an upstream valve (7), the opening and closing times of which are controlled according to the metering requirement. 3. Valves according to claim 2 characterized in that a linearly moving tappet valve is used, through whose hollow piston rod (8) the gas for the injector nozzle (3) is guided, the end of the piston rod (9) being designed in such a way that a tight seal against the valve seat (10), which is formed by the collecting nozzle (11), is achieved while simultaneously integrating the injector nozzle (3) into this piston rod head (9).