GB2125974A - Measuring the weight of powder feed - Google Patents
Measuring the weight of powder feed Download PDFInfo
- Publication number
- GB2125974A GB2125974A GB08224000A GB8224000A GB2125974A GB 2125974 A GB2125974 A GB 2125974A GB 08224000 A GB08224000 A GB 08224000A GB 8224000 A GB8224000 A GB 8224000A GB 2125974 A GB2125974 A GB 2125974A
- Authority
- GB
- United Kingdom
- Prior art keywords
- powder
- container
- replenishing
- feed container
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G13/00—Weighing apparatus with automatic feed or discharge for weighing-out batches of material
- G01G13/02—Means for automatically loading weigh pans or other receptacles, e.g. disposable containers, under control of the weighing mechanism
- G01G13/022—Material feeding devices
- G01G13/028—Material feeding devices by pneumatic carrying means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G11/00—Apparatus for weighing a continuous stream of material during flow; Conveyor belt weighers
- G01G11/14—Apparatus for weighing a continuous stream of material during flow; Conveyor belt weighers using totalising or integrating devices
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Weight Measurement For Supplying Or Discharging Of Specified Amounts Of Material (AREA)
Abstract
A powder control system has a pressurised powder feed container 4 for supplying powder from delivery port 7. The feed container 4 is connected to a replenishing container 3 by an expansible joint 5. Containers 3 and 4 are supported by load cells 6 and 8, signals from which are compensated for variations attributable to the pressurisation of the feed container 4, and displacements of expansible joint 5. The total weight of powder fed in any given period of time is determined by adding the weights of each replenishment from the replenishing container 3 to the feed container 4, and subtracting the weight of powder in containers 3 and 4 from the total weight of powder replenishment when the measurement is made during a replenishing operation, or subtracting the weight of powder in feed container 4 from the total weight of powder replenishment when the measurement is made outside the period of a replenishing operation. <IMAGE>
Description
SPECIFICATION
Method of measuring the weight of powder feed
This invention relates to a method of measuring the weight of powder feed in a given period of time while the powder is being continuously fed to a powder treating system.
Various feed mechanisms for particulate or powdery materials (hereinafter referred to simply as "powder" for brevity) are known, of which the systems utilising fluid pressure have a number of advantages over gravitational or mechanical feed systems, these advantages including a longer transfer distance of the powder, and the possibility of continuous quantitative feed. A powder transfer over a long distance, however, gives rise to large pressure losses in the feed line, necessitating the powder being fed under an extremely high pressure. This is particularly the case where a high pressure operation is required at the end of the feed line. In such a case, it becomes necessary to raise the pressure of the carrier gas source, and to increase the internal pressure of the powder feed container which delivers the powder.Moreover, a powder replenishing container is required for replenishing the powder feed container with powder; and desirably a hopper is also required for holding a stock of the powder for supply to the replenishing container. The powder is thus fed successively from the hopper to the replenishing container (hereinafter refferred to as "stock feed"), from the replenishing container to the feed container (hereinafter referred to as "powder replenishment"), and from the feed container to a powder treating system (hereinafter referred to as "powder feed"). Besides, it is the general practice to feed the stock powder under the ambient pressure, while intermittently pressurising the replenishing container each time the feed container is replenished, so that a complicated pressure control is involved in the transfer of the powder.However, there is no known method or means for accurately measuring the weight of the powder flowing along the afore-mentioned routes, for example, a method for accurately measuring the total weight of powder fed in a given past period of time, making it difficult to improve the accuracy of operation control on the side of the powder treating system.
The aim of the invention is to provide a method of measuring at an arbitrary movement in time, the total weight of powder which has been fed to a powder treating system in a given past period of time.
According to the present invention, this aim is achieved by a method which includes the steps of providing a powder delivery port in a lower portion of a powder feed container maintained under pressure for supplying powder to a powder blowing port of a powder treating system; connecting a powder replenishing container to an upper portion of the powder feed container, the powder replenishing container being provided for replenishing the powder feed container with fresh powder; continuously discharging the powder from the powder feed container by entrainment in a pressurised carrier gas introduced into the powder delivery port; communicating the powder replenishing and feed containers with each other in a suitable timing for replenishing the powder; and sequentially measuring the weights of powder in the respective containers to measure the integrated weight of the powder fed through the powder delivery port during a time period of operation; the method being characterised by the steps of: adding up batchwise the weight of each powder replenishment from the replenishing container to the powder feed container to obtain the total weight of powder replenishment; subtracting the sum of weights of momentary powder contents in the respective containers from the total weight of replenishment when the measurement takes place concurrently with the replenishing operation; and subtracting the weight of the momentary powder content in the powder feed container from the total weight of replenishment when the measurement takes place at a time point outside a time period of replenishing operation to obtain an integrated weight of the feed of the particulate material in a given time period.
The invention will now be described in greater detail, by way of example, with reference to the accompanying drawing, the single figure of which is a diagrammatic representation of a typical powder control system which can be used for carrying out the method of the invention.
Referring to the drawing, a powder control system has a powder feed container 4 which is supplied with powder (such as fine coal) from a hopper 2 via a replenishing container 3. The hopper 2 is used to store the fine coal under atmospheric pressure, the fine coal being obtained by pulverisation of coal 1. A valve 9 is provided to control the flow of fine coal from the hopper 2 to the replenishing container 3. A flexible expansion joint 5 is provided between the replenishing container 3 and the powder feed container 4, and a valve 1 3 is provided for controlling the flow of powder from the replenishing container to the powder feed container. A powder delivery port 7 is provided at the base of the powder feed container 4. The port 7 is provided with a valve 7' which, in use, is constantly open.
The powder feed container 4 is pressurised by a carrier gas which is introduced thereinto, via the port 7, from a pressure source A. Preferably, where the powder is fine coal, the carrier gas is nitrogen or an inert gas such as a rare gas. The pressure source A can also be connected to the replenishing container 3 via a valve 11. The replenishing container 3 can be connected to the atmosphere via a valve 10. Powder leaving the port 7 is delivered to a powder treating system 1 6 by means of a carrier gas supplied from a source
B. Although the pressure sources A and B are shown as separate sources they may be constituted by a single source.The gas flow from the source B is controlled by a valve 14, and the gas is mixed with the powder at a T-joint 1 5. A pressure-equalising valve 12 is provided in a line between the two containers 3 and 4.
In use, the powder (fine coal) is fed from the
hopper 2 to the replenishing container 3 by opening the valve 9 when the replenishing container is empty, or is running short of powder.
On such an occasion, the valve 10 is opened and the valves 11 and 1 2 are closed, so that the
replenishing container 3 is at atmospheric pressure. As the powder feed container 4 becomes short of powder as a result of the continuous discharge through the port 7, it is necessary to replenish this container with powder from the replenishing container 3. Before doing this, the replenishing container 3 (which is at atmospheric pressure) must be pressurised to a level substantially the same as that of the powder feed container 4. This is accomplished by opening the valve 11 and closing the valves 9, 10 and 12.
This permits the container 3 to be pressurised from the pressure source A. Then, when the amount of powder in the powder feed container 4 has fallen to a predetermined level, the valve 13 is opened to start replenishment of the container 4.
This leads to a pressure drop in the container 3 and a pressure rise in the container 4, so that the valve 12 is opened to equalise the pressures in the two containers. As soon as the powder replenishment process is finished, the valves 11, 12 and 13 are closed, and the valve 10 is slowly opened to release the pressure in the container 3 for equalisation with the atmospheric pressure.
The valve 9 can then be opened to refill the container 3 with powder from the hopper 2.
As the valve 7' at the powder delivery port 7 is aiways open, powder particles constantly drop, in a pressurised state, towards the T-joint 1 5.
Although the powder in the container 4 is pressurised, it is kept from being consolidated by the agitating action of the carrier gas which is blown into the container 4 from the pressure source A. The falling powder particles are mixed with the blown carrier gas from the pressure source B at the T-joint 15, the carrier gas blowing the powder particles into the powder treating system 1 6.
Where the powder treating system 1 6 has a
number of tuyeres (for example in the case of a
blast furnace), a distributor may be provided
downstream of the powder delivery port 7.
Alternatively, a distributor may be provided down
stream of a number of delivery ports provided in
the lower portion of the powder feed container 4,
(the number of ports corresponding to the number
of tuyeres or groups of tuyeres). In this case, the
distributor is connected to the delivery ports by
respective T-joints to provide powder blowing
lines which are completely independent of each
other, and which are easily controllable separately
in dependence upon the differences in pressure
loss resulting from the differences in length of the blowing lines (and any bent portions contained therein).
In such a powder control system, it may be
necessary to weigh the amount of powder fed to the powder treating system 1 6 is a given period of time. A rough value of the weight of powder feed can be obtained by summing up the weights of the replenishments of powder from the replenishing container 3 to the powder feed container 4. However, more elaborate calculations are required to measure the weight of powder feed in a short time period, or between arbitrary moments in time. Moreover, depending upon the capacities of the containers 3 and 4 and the feed rate of the powder, powder replenishment may be necessary at frequent intervals and/or take a relatively long time for each replenishing operation. Consequently, the time period in which the weight of powder feed is required, may overlap a period of powder replenishment.The aim of the invention is to provide a method of accurately weighing the powder feed even on such occasions.
According to the invention, this aim is achieved by connecting the replenishing container 3 and the feed container 4 to one another by the expansion joint 5, and by supporting the containers 3 and 4 by respective load-detecting means such as load cells 6 and 8. Since the weights of the containers 3 and 4 (including valves and other attached elements) are known, the weights of powder in the containers can be obtained by subtracting the known container weights from the values supplied by the load cells 6 and 8. The resulting values may be used directly, but is desired to add the following corrections for enhancing the accuracy of measurement. Firstly, as the powder feed container 4 is constantly maintained under pressure, it is necessary to make corrections in consideration of the resulting ioad, and the reaction of the replenishing container 3.For this purpose, the reading of a pressure gauge 19 is supplied to weight-computing devices 1 7 and 18 to make a corresponding correction towards the positive (+) end for the powder in the container 3 and towards the negative (-) end for the powder in the container 4. Moreover, as the containers 3 and 4 are connected to one another by the flexible expansion joint 5, the readings of the load cells 6 and 8 are influenced by the spring reactions which act on the containers 3 and 4 due to vibrations occurring during powder relenishment operations. To make corrections to allow for these influences, the reactions resulting from contraction and expansion of the joint 5 are measured by, for example, a strain gauge 20. The strain gauge sends a signal of positive compensation (+) to the weight-computing device 17, and a signal of negative compensation () to the weight computing device 18. The resulting signals are converted into electric current signals, of which:
(1) The sum of the weights of the powder in the containers 3 and 4 at a given moment is defined as the weight of the currently-available powder feed when a measurement is made during a powder replenishment operation; and
(2) The weight of the powder in the container 4 at a given moment is defined as the weight of the currently-available powder feed when a measurement is made outside the period of a powder replenishment operation.
Therefore, at a given moment, in order to get the total weight of powder feed since the start of operation, the weight of the afore-mentioned currently-available powder feed at that moment is substracted from the total weight of powder replenishments. Thus, according to the present invention, the weight of currently-available powder feed to be subtracted depends upon whether or not the moment of measurement falls in a period of powder replenishment, thereby permitting accurate measurement at an arbitrary moment in time irrespective of powder replenishing operations.However, it is recommended not to make the measurement (or the above-mentioned calculations) in the initial stage of a powder replenishment operation (normally 10-1 5 seconds), during which the reading of the load cell 8 fluctuates owing to the impact of the falling powder, as this could lead to substantial errors creeping into the measured values. The total weight of the powder replenishments in a given past period of operation can be obtained by adding the weights of the replenishments, that is to say by adding the weights of powder supplied under atmospheric pressure to the container 3, and subtracting the weight of residual powder in the replenishing container at the end of the replenishing operation.
Thus, the total weight of powder feed from the very start of operation can be obtained. For example, if the total weight of powder feed is found to be Wa at moment a and to be Wb 30 minutes or 1 hour later at moment b, the weight of the powder feed during the time interval of measurement (during the time of b-a) is expressed by
Wb-Wa
Thus, it is possible to measure accurately the total weight of powder feed from the starting point of a given operation. Consequently, if the measurement is effected at predetermined moments or at suitable time intervals, an exact weight of powder feed between two selected moments can be obtained by calculating the difference between the integrated weights at those moments.
It will be appreciated from the foregoing description that the method of the present invention always ensures correct measurement of the weight of powder feed in a past time period irrespective of the timing of measurement.
Claims (8)
1. A method of measuring the weight of powder feed to a powder treating system by a powder control system having a pressurised powder feed container for supplying powder into a blowing port of the powder treatment system, a powder replenishing container connected to an upper portion of the powder feed container or replenishing the powder feed container with powder under pressure, the lower portion of the powder feed container being provided with a powder delivery port through which powder is continuously fed, by means of carrier gas introduced into the powder delivery port, to said blowing port, the powder feed container being replenished with powder from the powder replenishing container whenever the powder in the powder feed container falls to a predetermined level, the method comprising the steps of adding up batchwise the weights of each powder replenishment from the powder replenishing container to the powder feed container to obtain the total weight of powder replenishment, subtracting the sum of the weights of the powder in said containers from said total weight of powder replenishment when the measurement is made during a replenishing operation; and subtracting the weight of powder in the powder feed container from said total weight of powder replenishment when the measurement is made outside the period of a powder replenishing operation.
2. In a method for measuring an integrated weight of powder being continuously fed to a powder treating system or the like by providing a powder delivery port in a lower portion of a pressurised powder feed container for supplying said powder into a blowing port of said treating system, connecting a pressurised powder replenishing container to an upper portion of said powder feed container for replenishing same with said powder under pressure, continuously feeding the powder along with part of a pressurised carrier gas introduced into said delivery port of said pressurised powder feed container, communicating said powder replenishing and feed containers with each other in a suitable timing for replenishing said powder, and sequentially measuring the weights of powder contents in said containers to measure the integrated weight of the powder fed through said delivery port during a time period of operation, the method comprising the steps of: adding up batchwise the weight of each powder replenishment from said replenishing container to said feed container to obtain the total weight of powder replenishment; subtracting the sum of the weights of momentary powder contents of said containers from said total weight of powder replenishment when the measurement is made in concurrence with a replenishing operation; and subtracting the weight of momentary powder content of said powder feed container from said total weight of powder replenishment when the measurement is made at a time point falling outside the time period of a replenishing operation.
3. A method as claimed in claim 1 or claim 2, wherein the pressurised powder feed container is connected to the powder replenishing container by an expansible joint, and each of the containers is supported in position by a respective loaddetecting device, the load-detecting devices being effective to measure the weights of powder in the containers, and to compensate for variations attributable to the pressurisation of the powder feed container and displacements of the expansible joint.
4. A method as claimed in any one of claims 1 to 3, wherein the measurement is reserved in the initial stage of a replenishing operation from the powder replenishing container to the powder feed container until the reading of the weight of powder in the powder feed container settles down.
5. A method of measuring the weight of powder feed to a powder treating system, the
method being substantially as hereinbefore described with reference to the accompanying drawing.
6. A powder control system comprising a
pressurised powder feed container for supplying powder to a powder treating system via a powder delivery port, a powder replenishing container for replenishing the powder feed container with powder when the powder in the powder feed container falls to a predetermined level, and means for weighing the amount of powder feed through the powder delivery port in a given period of time, wherein the powder feed container is connected to the powder replenishing container by an expansible joint, and wherein each of the containers is supported in position by a respective load-detecting device, the load-detecting devices being effective to weigh the powder in the containers, and to compensate for variations attributable to the pressurisation of the powder feed container and displacements of the expansible joint.
7. A system as claimed in claim 6, wherein each of the load-detecting devices is a load cell.
8. A powder control system substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08224000A GB2125974B (en) | 1982-08-20 | 1982-08-20 | Measuring the weight of powder feed |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08224000A GB2125974B (en) | 1982-08-20 | 1982-08-20 | Measuring the weight of powder feed |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2125974A true GB2125974A (en) | 1984-03-14 |
| GB2125974B GB2125974B (en) | 1985-08-29 |
Family
ID=10532431
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08224000A Expired GB2125974B (en) | 1982-08-20 | 1982-08-20 | Measuring the weight of powder feed |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2125974B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100354613C (en) * | 2002-08-06 | 2007-12-12 | 维特罗环球有限公司 | Method and apparatus for feeding a pulverized material |
-
1982
- 1982-08-20 GB GB08224000A patent/GB2125974B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100354613C (en) * | 2002-08-06 | 2007-12-12 | 维特罗环球有限公司 | Method and apparatus for feeding a pulverized material |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2125974B (en) | 1985-08-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19980820 |