WO2020233912A1

WO2020233912A1 - Device for measuring a mass flow and for metering bulk material, and method for metering bulk material

Info

Publication number: WO2020233912A1
Application number: PCT/EP2020/060679
Authority: WO
Inventors: Robert Weinand
Original assignee: Schenck Process Europe Gmbh
Priority date: 2019-05-23
Filing date: 2020-04-16
Publication date: 2020-11-26
Also published as: DE102019113718A1

Abstract

The invention relates to a device (1) for measuring a mass flow and for metering bulk material, having: a conveying channel (2) for transferring bulk material to be metered from an entry side (3) to an exit side (4) of the conveying channel (2); a conveying means (5) arranged in the conveying channel (2), for conveying the bulk material from the entry side (3) to the exit side (4) of the conveying channel (2); and a drive unit (6) for driving the conveying means (5), wherein the conveying means (5) has multiple congruent helices (7) which have a common central axis. The invention also relates to a method for metering bulk material.

Description

Device for measuring a mass flow and metering

Bulk material and methods of dosing bulk material

description

The invention relates to a device for measuring a mass flow and metering bulk material, with a conveyor channel for transferring bulk material to be metered from an inlet side to an outlet side of the conveyor channel, with a conveyor arranged in the conveyor channel for conveying the bulk material from the inlet side to the outlet side of the conveyor channel , and with a

Drive unit for driving the conveyor. The invention also relates to a method for metering bulk material with such a device.

A feed metering device for measuring bulk material is already known from WO 2009/065524 A1. The document discloses a conveyor dosing device for bulk material with a motor-driven conveyor for conveying the bulk material, the conveyor being mounted separately and completely floating, with a number of measuring devices being provided which are designed to measure the weight load on the conveyor, a screw conveyor, by the To determine bulk material. The

Weight is calculated as the mean value of several measuring devices, assuming a uniformly distributed load and thus a constant load by the bulk material. However, this assumption is only correct for homogeneous bulk solids, the density and flow properties of which remain largely constant and do not contain any impurities, agglomerates or foreign bodies.

A feed metering device is also known from WO 2013/026574 A1. In this a dosing device for bulk goods with a horizontally extending, motor-driven one arranged at an outlet opening of a bulk goods container

driven conveyor disclosed, wherein the conveyor is designed to convey the bulk material from an entry area to an exit area, and wherein the entry area is arranged below the bulk material container and the exit area is supported on at least one first measuring device. The measuring device serves to determine the weight load on the conveying means by the bulk goods, the conveying means being suspended from the bulk goods container at the entry area in a freely floating manner. A triangular line load is assumed to record the weight in the corresponding measuring device. In order to achieve good metering accuracy, this requires a constant and steady course of the

Weight loading by the bulk material. This is when using a

Conveyor screw is limited and sometimes difficult to implement for several reasons.

However, the prior art always has the disadvantage that when using screw conveyors, i. E. a screw tube lying in a trough, rotating around its central axis, as a conveying means the weight detection of the conveyed bulk material is often relatively imprecise. On the one hand, part of the bulk material is supported on the worm shaft when the weight is recorded. On the other hand, the bulk material descends in front of the driving screw spiral and / or towards the side housing wall. The resulting shifts in the center of gravity cause errors in weight recording and

Dosing inaccuracies.

It is therefore the object of the invention to avoid or at least reduce the disadvantages of the prior art. In particular, a device for measuring and metering a mass flow of bulk material is to be provided which enables the bulk material to be weighed as precisely as possible. These

In addition, accuracy should be achieved with a high setting range a high ratio between minimum and maximum delivery rate can be achieved.

It is also the object of the invention to provide a method for dosing

Provide bulk material by means of which a predetermined amount of

Bulk material can be dispensed particularly precisely dosed.

The object of the invention is achieved with a device of the generic type

solved according to the invention in that the conveying means has several congruent flelices which have a common central axis.

In contrast to the blades of a screw conveyor, which consist of a flange that is arranged around and attached to a central shaft, is a Helix a shaftless screw conveyor. The flange of a helix is self-supporting and describes a spiral around the central axis of the screw conveyor, the flange extending between an inner and an outer radius.

According to the invention, the helices are designed so that they go through

Congruence images, such as rotation, mirroring and / or parallel displacement, can be converted into one another. They are symmetrical to one another, in particular axially symmetrical about their central axis or axis of rotation. In other words, the conveying means is formed by at least two helices that are of identical design. The helices are arranged with respect to one another in such a way that they have a common central axis. In other words, the helices are

axially symmetrical, i.e. rotationally symmetrical by 180 °, to a common

Central axis, i.e. designed as a multi-start screw, in particular as a double-start screw. This means that the helices rotate around the same axis as one

Corresponds to the central axis of the conveyor. In other words, the helices are arranged coaxially to one another. As a result, the helices of the conveyor rotate about their common central axis when the conveyor is driven.

Advantageous embodiments are claimed in the subclaims and are explained in more detail below.

According to a preferred embodiment, the funding means can have two helices. The two or more helices can be of the same type, preferably the same, with regard to their outer diameter and / or their core diameter, i.e. their inside diameter and / or their pitch, preferably with their constant

Pitch, and / or its axial extent and / or its winding direction, i.e. be designed left-handed or right-handed, and / or their number of turns and / or their pitch. This means that the helices can be designed as identical parts, which has an advantageous effect on production. It is also ensured in an advantageous manner that by conveying the bulk material

the resulting load is distributed essentially evenly, ie in equal parts, to the individual helices. According to a preferred development, the helices can be offset from one another by half a pitch and / or by half a revolution, ie by 180 °. As a result, a conveyor with two helices will necessarily be symmetrical

Arrangement of the two helices guaranteed. In a preferred embodiment of the conveying means with n helices, the n helices can each be rotated by a 1 / n pitch and / or by a 1 / n revolution, i.e. be arranged offset from one another by 360 h. This advantageously ensures that the bulk material is conveyed evenly through the helices.

In a preferred embodiment, the funding, preferably the

Helices, be prestressed in the axial direction in the conveyor channel. In particular, it is advantageous if the helices are axially pretensioned via a spring assembly in a bearing supporting the conveying means. This allows the deflection of the helices and thus of the conveying means to be additionally reduced.

Furthermore, according to a preferred further development of the embodiment, several measuring devices can be provided which are arranged and designed to determine the weight load on the conveying means by the bulk material. The weight of the bulk material, which is made up of the individual weight measurements of the multiple measuring devices, can thus be recorded continuously and reliably. By providing several measuring devices, leverage effects resulting from different centers of gravity of the bulk material can be compensated.

In a preferred embodiment, a first measuring device on the inlet side of the conveying channel and / or a second measuring device on the

Be arranged exit side of the conveyor channel for measuring the weight of the bulk material. By providing measuring devices on the inlet side and on the outlet side, it is advantageously possible to detect the weight of an inlet quantity of bulk material and the weight of an outlet quantity of bulk material. A mass flow of the bulk material can thus be determined very precisely. According to an advantageous further development of the embodiment, the first measuring device can be formed by two load cells and the second measuring device by one load cell. For reasons of symmetry there are at least three

Load cells required to get an accurate measurement. In addition, it has proven to be advantageous to provide more load cells on the entry side, since the drive for the conveying means is mostly arranged on the entry side, and therefore there is a greater weight load on the entry side. By providing the three load cells, a secure stand as a “tripod” can also be guaranteed.

According to a preferred further development of the embodiment, an adjustable gap can be formed between the helices and an inner wall of the conveying channel which is lower in the direction of gravity. For example, the conveying channel has a tubular or trough-shaped housing in which the helices are arranged. This advantageously makes it possible to adjust the gap as a function of a grain size of the bulk material to be conveyed.

It is particularly preferred if the gap is a maximum of 5 times as large, preferably a maximum of 2 times as large as an average grain size of the bulk material.

This enables the conveyor channel to be emptied completely and reproducibly. This is essential for a particularly precise taring of the zero point.

The object of the invention is also achieved by a method for dosing

Bulk material, in particular with a device according to the invention, solved, the method comprising the following steps: measuring the weight of the

Bulk material of the device by means of a first measuring device on an inlet side of a conveying channel in order to regulate a (dispenser) inlet quantity; - Measuring the weight of the bulk material of the device by means of a second

Measuring device on an exit side of the conveyor channel for determining a

Mass flow of the bulk material conveyed in the conveying channel; - Comparing the determined mass flow with a predetermined target mass flow; Adaptation of a conveying speed of a conveying means as a function of the comparison between the determined mass flow and the specified target mass flow. In other words, the invention relates to a device and a method for measuring and metering a bulk material mass flow. In contrast to

Dosing devices with conventional conveying means, for example a screw, in which no satisfactory accuracy is achieved due to their screw tube and the bulk material that is supported on it and therefore not precisely recorded by measurement, and an absolute accuracy of the measurement of the degree of filling of the

Depending on the conveyor channel, a conveyor with more precise

Weight measurement developed. The (conveying) device according to the invention has two symmetrically arranged flelices which are pretensioned in a loose bearing supporting the flelices. This eliminates or at least reduces the deflection due to its own weight and a gap between one

Conveyor channel housing / the conveyor channel and the helices can be made small and constant. For dosing, a feeder is controlled via two load cells at the inlet / inlet side and the load is regulated to a constant level. At the discharge / on the exit side, the target value of the

Delivery rate regulated by the speed. For taring / for zero point referencing, the feeder is stopped and the conveyor channel is completely emptied. This means that caking in the conveyor channel or on the conveyor can also be tared away, so that the measurement is not falsified by caked-on bulk material.

According to the invention, a conveying means is proposed which has two symmetrically arranged and prestressed helices.

The invention is explained below with the aid of drawings. Show it:

1 shows a perspective representation of a device according to the invention with several similar cylindrical helices as a conveying means,

2 shows a longitudinal sectional view of the device,

3 shows a perspective illustration of the helices, and

4 shows a schematic block diagram of a method according to the invention The figures are only of a schematic nature and serve exclusively

Understanding the Invention. The same elements are identified by the same reference symbols.

FIGS. 1 and 2 show a device 1 according to the invention for measuring a mass flow and metering bulk material. The device 1 has a conveyor channel 2 by means of which bulk material to be metered can be transferred from an inlet side 3 to an outlet side 4 of the conveyor channel 2. By doing

Conveying channel 2, a conveyor 5 is arranged, which is designed to

To convey bulk material from the inlet side 3 to the outlet side 4 of the conveyor channel 2. The device 1 also has a drive unit 6 which drives the conveyor 5 at an adjustable speed, so that the conveyor 5 rotates about its own axis. The conveyor 5 has several, shown in the

Embodiment two, flelices 7, which have a common central axis (see FIG. 3). The multiple flelices 7 are designed to be congruent to one another.

The conveying channel 2 has a circular cross section and encloses a cavity in which the bulk material / bulk material is conveyed. An allocator or inlet quantity of bulk material is introduced into the conveying channel 2 on the inlet side 3 via a distributor channel 8. A discharge amount of bulk material is on the

Exit side 4 is discharged from the conveying channel 2 via an exit channel 9.

The conveying means 5 has two shaft journals 10 by means of which it is rotatably mounted on the inlet side 3 and on the outlet side 4 with respect to the conveying channel 2. On the inlet side 3, a self-aligning bearing 11, designed as a fixed bearing, is arranged for mounting the one shaft journal 10. On the exit side 4 there is a self-aligning bearing 12 designed as a floating bearing for mounting the other shaft journal 10

arranged. The drive unit 6 is arranged on the entry side 3 and drives the conveying means 5 via the shaft journal 10. The conveyor 5 is biased in the axial direction. The preload is implemented in the self-aligning bearing 12.

The device 1 has several measuring devices 13. A first measuring device 14 is arranged on the inlet side 3 of the conveying channel 2 and a second one Measuring device 15 is arranged on exit side 4 of conveyor channel 2. The first measuring device 14 is formed by a first load cell 16 and a second load cell 17. The second measuring device 15 is formed by a third load cell 18. The device 1 thus stands on a “tripod” formed by the three load cells 16, 17, 18. The load cells 16, 17, 18 are arranged below a housing 19 of the conveying channel 2 in the direction of gravity.

In FIG. 2 it can be seen that a gap 21 is formed between an outer diameter of the conveying means 5 and a lower inner wall 20 of the housing 19 of the conveying channel 2. The gap 21 is adjustable and over the axial extent of the

Conveying channel 2 largely constant.

3 shows a perspective illustration of the conveying means 5. The conveying means 5 has the two flelices 7, which have a common axis of rotation and are arranged offset from one another by 180 °. A first helix 22 of the two flelices 7 has the same external diameter as a second helix 23 of the two flelices 7. The first helix 22 has the same core diameter or

Inner diameter like the second helix 23. The first helix 22 has the same axial extension 24 as the second helix 23. An axial extension 24 is defined by the axial extension of the coils, i. winding flange that defines flelices 7. The first helix 22 is arranged in the axial direction on the same flea as the second helix 23, so that the two flelices 7 completely overlap in the axial direction. The first helix 22 has the same pitch 25 as the second helix 23. The first helix 22 has the same pitch as the second helix 23. The first helix 22 has the same winding direction as the second helix 23. The first helix 22 has the same number of turns as the second helix 23.

The first helix 22 is arranged offset by half the pitch 25 to the second helix, so that the conveying means 5 has a uniform pitch of turns. The first helix 22 and the second helix 23 are each attached to the shaft journal 10, so that when the shaft journal 10 rotates, they rotate about their common central axis at the same speed.

4 shows, in an abstract representation, steps of a method according to the invention. In a first step 26, the bulk material is fed to the device 1 via a feeder channel 8 via a feeder. In the second step 27 the

Weight load or the weight of the bulk material by means of the first

Measuring device 14 measured on the inlet side 3 of the conveyor channel 2. Based on the measurement of the weight load, in a third step 28 the dispenser or inlet amount is regulated to a desired inlet amount. In a fourth step 29, the bulk material is by means of a regulated drive unit 6 by means of the

Conveyor transported to the exit side.

In the fifth step 30, the weight loading of the bulk material is measured by means of the second measuring device 15 on the outlet side 4 of the conveying channel 2.

Based on the measurement of the weight load, the conveyed mass flow of bulk material is determined in the conveying channel 2.

In a sixth step 31, the determined mass flow is compared with a predefined setpoint mass flow. In a step 31, a conveying speed of the conveying means 5 is adapted, for example via a control of the speed of the drive unit 6, as a function of the comparison between the determined mass flow and the target mass flow.

List of reference symbols

1 device

2 conveyor channel

3 entry side

4 exit side

5 grants

6 drive unit

7 helix

8 distributor channel

9 outlet duct

10 shaft journals

11 self-aligning bearings

12 self-aligning bearings

13 measuring device

14 first measuring device on the inlet side

15 second measuring device on the exit side

16 first load cell on the entry side

17 second load cell on the entry side

18 third load cell on the exit side

19 housing

20 lower inner wall

21 gap

22 first helix

23 second helix

24 axial extension 25 pitch

26 first step

27 second step

28 third step

29 fourth step 30 fifth step

31 sixth step

Claims

Expectations

1. Device (1) for measuring a mass flow and metering

Bulk material,

with a conveying channel (2) for transferring bulk material to be dosed from an inlet side (3) to an outlet side (4) of the conveying channel (2),

with a conveyor (5) arranged in the conveyor channel (2) for conveying the

Bulk material from the inlet side (3) to the outlet side (4) of the conveyor channel (2), and

with a drive unit (6) for driving the conveyor (5),

characterized in that

the conveyor (5) has a plurality of congruent flelices (7) which have a common central axis.

2. Device (1) according to claim 1, characterized in that the conveying means (5) has two flelices (22, 23).

3. Device (1) according to claim 1 or 2, characterized in that the flelices (7, 22, 23) are similar with respect to their outer diameter and / or their

Core diameter and / or their pitch and / or their axial extent (24) and / or their winding direction and / or their number of turns and / or their pitch (25).

4. Device (1) according to one of claims 1 to 3, characterized in that the flelices (7, 22, 23) by half a pitch (25) and / or by half

Rotation are offset from each other.

5. Device (1) according to one of claims 1 to 4, characterized in that the helicopters (7, 22, 23) in the conveying channel (2) are biased in the axial direction.

6. Device (1) according to one of claims 1 to 5, characterized in that a plurality of measuring devices (13) are provided, which are arranged and designed to the weight load of the conveyor (5) by the

To determine bulk material.

7. Device (1) according to claim 6, characterized in that a first measuring device (14) on the inlet side (3) of the conveyor channel (2) and / or a second measuring device (15) on the outlet side (4) of the conveyor channel (2 ) are arranged for measuring the weight of the bulk material.

8. Device (1) according to claim 7, characterized in that the first

Measuring device (14) is formed by two load cells (16, 17) and / or the second measuring device (15) is formed by a load cell (18).

9. Device (1) according to one of claims 1 to 8, characterized in that an adjustable gap (21) is formed between the helices (7, 22, 23) and a lower inner wall (20) of the conveying channel (2).

10. Device (1) according to claim 9, characterized in that the gap (21) is a maximum of 5 times as large, preferably a maximum of 2 times as large as a middle one

Grain size of the bulk material is.

11. A method for dosing bulk material with a device (1) according to one of claims 1 to 10, with the steps:

- Measuring the weight of the bulk material of the device (1) by means of a first measuring device (14) on an entry side (3) of a conveying channel (2) to a

To regulate the (dispenser) inlet volume;

- Measuring the weight of the bulk material of the device (1) by means of a second measuring device (15) on an exit side (4) of the conveying channel (2) to determine a mass flow of the bulk material conveyed in the conveying channel (2); - Compare the determined mass flow with a given target

Mass flow;

- Adaptation of a conveying speed of a conveying means (5) as a function of the comparison between the determined mass flow and the specified target mass flow.