Title of Invention

"DEVICE FOR CONTINUOUSLY FEEDING A POWDERY SOLID INTO A PNEUMATIC CONVEYING LINE"

Abstract

A device for continuously feeding a powdery solid from a storage container (10) into a pneumatic conveying line (12, 12') comprises a first and a second intermediate vessel (14 and 16) arranged side by side. The first intermediate vessel (14) takes the form of a lock chamber with an upper shut-off valve (18) and a lower shut-off valve (20). The second intermediate vessel (16) takes the form of an injection chamber. Between the lower shut-off valve (20) of the first intermediate vessel (14) and an upper inlet (30) of the second intermediate vessel (16) a pneumatic intermediate conveying line (50) is arranged, by means of which the powdery solid from the first intermediate vessel (14) can be conveyed into the second intermediate vessel (16). (Fig- 1)

Full Text

DEVICE FOR CONTINUOUSLY FEEDING A POWDERY SOLID INTO A PNEUMATIC CONVEYING LINE The present invention concerns a device for continuously feeding a powdery solid into a pneumatic conveying line. Prior art When a powdery solid, such as coal dust, is to be fed continuously from a storage container into a pneumatic conveying line, two different introduction methods may be used, depending on the state of the art. In the first method, two intermediate vessels are positioned vertically one above the other under the storage container. The upper intermediate vessel operates as a lock chamber. The following cycle is enacted periodically: (1) filling of the upper intermediate vessel with powdery solid under ambient pressure from the storage container; (2) closure of the upper intermediate vessel with respect to the storage container; (3) pressurization of the upper intermediate vessel; (4) emptying of the pressurized upper intermediate vessel by gravity into the lower intermediate vessel; (5) closure of the upper intermediate vessel with respect to the lower intermediate vessel, and (6) depressurization of the upper intermediate vessel. The lower intermediate vessel serves as an injection chamber which is permanently under pressure and from which the powdery solid is continuously fed into the pneumatic conveying line. In the second method, two similar intermediate vessels are arranged side by side and in parallel under the storage container. These intermediate vessels act as both lock chamber and injection chamber. They both repeat the same cycle, but offset in time so that at any given moment the powdery solid is being continuously blown into the pneumatic conveying line from one of the two containers, while the other intermediate vessel is being refilled from the storage container. Vertical arrangement of the intermediate vessels in series is mainly used when the powdery solid is to be injected into a relatively large number of conveying lines. Parallel flow with the intermediate vessels arranged horizontally is mainly used when only one conveying line, or at most a few lines, is to be fed. EP 0362120 describes a device for continuous feed of bulk material into a pneumatic conveying line with a lock chamber and an output container arranged in series. The lock chamber is arranged above the output container and its outlet opens into the output container underneath it through an outlet valve. Emptying of the lock chamber into the output container is assisted by higher pressure in the lock chamber. US 4,599,017 describes a device for supplying a plurality of user stations with a powdery solid from a conveying line. The conveying line is constructed as a ring line with a storage container, pressure container and one intermediate vessel for each user station. The storage container is apparently arranged above the pressure container and empties into the latter through a shut-off valve. Feeding of the powdery solid into the conveying line is interrupted while the pressure container is topped up, so that this cannot be considered to be continuous feeding of a powdery solid into the conveying line. WO 87/04415 describes a device for conveying bulk material on a ship. This installation comprises at least one storage container below decks, a loading unit on the upper deck of the ship, a transport line linking the storage container to the loading unit and a feed line which links the loading unit to an unloading station. The loading unit comprises at least two loading containers. These can operate alternately, one loading container being filled by the transport line while the other loading container is being emptied by the feed line. To fill a loading container, the storage container is subjected to pressure and the loading container is depressurized into the atmosphere, so that transport of the bulk material from the storage container to the loading container positioned at a higher level is carried out pneumatically. The loading container is emptied by being subjected to a higher pressure. This device needs at least two loading containers in parallel to provide continuous feed of the bulk material into the feed line. Both parallel and series connection of the intermediate vessels present disadvantages. Disadvantages of serial flow with vertical arrangement of the intermediate vessels are, for example: the great height of the structure, bearing in mind that above the two vertically arranged intermediate vessels, there is also a large storage container. the comparatively large diameter of the linking line (down-pipe) between the lower outlet of the upper intermediate vessel and the upper inlet into the lower intermediate vessel. This large diameter is necessary so that outflow of the powdery solid from the upper container into the lower container can be induced. This large diameter, however, necessitates large and costly shut-off valve fittings at the outlet resp. inlet of both containers. It should also be noted that the shut-off valve fitting at the outlet of the upper lock chamber is impinged upon by the powdery solid, and that opening it becomes proportionately more difficult as the diameter of the shut-off device increases. the relatively frequent perturbations known from experience in the feed operation. This is because pressurization compacts the powdery solid in the lock chamber, so that in spite of the large diameter of the outlet and the utilization of loosening devices, hesitations, interruptions or cessation of the outlet process can occur. Disadvantages of parallel flow are: Each intermediate vessel has to be equipped with a complete loosening and delivery system to form a solid-fluid mixture and convey the mixture into the conveying line. Introducing the powdery solid into a plurality of conveying lines can only be done at great expense. The variations that experience shows to occur frequently in the volume of output flow at each changeover from one container to the other. These variations can only be suppressed with difficulty, at great expense, and only incompletely. The object of the invention The object of the invention is to design a simple device for continuously feeding a powdery solid into a pneumatic conveying line which would, at least partially, eliminate the above-mentioned disadvantages. This object is achieved by a device according to Claim 1. Summary of the invention A device according to the invention for continuously feeding a powdery solid from a storage container into a pneumatic conveying line comprises a first and a second intermediate vessel. The first intermediate vessel constitutes a lock chamber with an upper shut-off valve and a lower shut-off valve, able to be topped up with powdery solid from the storage container through the upper shut-off valve and emptied through the lower shut-off valve. The second intermediate vessel constitutes an injection chamber with an upper inlet for filling from the first intermediate vessel and a lower delivery opening for continuously feeding the powdery solid into the pneumatic conveying line. According to the invention, the first and second intermediate vessels are set up side by side and, between the lower shut-off valve of the first intermediate vessel and the upper inlet to the second intermediate vessel, a pneumatic intermediate conveyor with fluidization device is provided, by means of which the powdery solid can be conveyed from the first intermediate vessel into the second intermediate vessel. The transfer of the powdery solid from the first intermediate vessel into the second intermediate vessel by means of a pneumatic intermediate conveyor with fluidization device avoids the outlay on equipment and the vulnerability to disruption of a pressurized gravity feed. From the second intermediate vessel, which is permanently pressurized, the solid-fluid mixture is continuously fed into one or more conveying lines. Only one loosening and delivery device is required, and the variations in the volume of output flow resulting from the changeover between containers are absent. It should be noted that for the pneumatic intermediate transfer between the two adjacent intermediate vessels, only a small increase in pressure in the first intermediate vessel is required, and that the resulting increase in consumption of pressurizing gas is also modest compared to the consumption of a gravity feed. For the two adjacent intermediate vessels, a common device for pressure maintenance resp. a common device for pressure release can advantageously be included. A common device for pressure maintenance can for example comprise: a common gas supply; a pressure regulation valve in the common gas supply; a first connection with a first shut-off valve to the first intermediate vessel; and a second connection with a second shut-off valve to the second intermediate vessel. A common device for pressure release can for example comprise: a common gas release line; a pressure release valve in the common gas release line; a first connection with a first shut-off valve to the first intermediate vessel; and a second connection with a second shut-off valve to the second intermediate vessel. Only one set of the equipment for pressure maintenance and pressure release need be provided, as it can be switched from one intermediate vessel to the other by means of shut-off valves. If no material is transferred from the first to the second intermediate vessel, the pressure regulation device in the second intermediate vessel maintains the necessary additional pressure to ensure perfect delivery of the solid-fluid mixture into the second intermediate vessel. During the pneumatic intermediate transfer of the powdery solid from the first to the second intermediate vessel, the pressure regulator maintains the necessary additional pressure in the second intermediate vessel, while the pressure release regulator evacuates the excess gas from the second intermediate vessel and releases it for example through a filter into the environment. When the intermediate transfer is complete, the pressure release regulator is brought into action to release the pressure in the first intermediate vessel. A feed unit for fluidization gas advantageously comprises three branches in parallel, each having a shut-off valve and a Laval nozzle. The Laval nozzle in the first branch should then admit one seventh, the Laval nozzle in the second branch two sevenths, and the Laval nozzle in the third branch four sevenths of the maximum gas flow required. By this means, the flow volume can be adjusted in six equal steps from 1/7 of the maximum gas flow to 7/7 of the maximum gas flow. Thus practically continuous regulation of the flow volume of fluidization gas is obtained, without the need to have recourse to complicated flow measurements. Such a gas feed unit advantageously also comprises a fourth branch with a shut-off valve and a Laval nozzle, designed as a flushing gas supply. The fluidization device of the pneumatic intermediate transfer advantageously comprises a fluidization chamber with a gas feed unit. The latter advantageously comprises two branches in parallel, each having a shut-off valve and a Laval nozzle, one of the branches being designed as a flushing gas supply. List of drawings In what follows, an embodiment of the invention will be described with reference to the attached drawing. Fig. 1 : shows a diagram of a device according to the invention for continuously feeding a powdery solid from a storage container into a pneumatic conveying line. Description of a preferred embodiment of the invention with reference to drawings Reference number 10 in Fig. 1 designates a storage container in which a powdery solid, e.g. coal dust, is stored. This powdery solid is to be continuously blown into at least one pneumatic conveying line 12,12'. The device employed for this purpose comprises a first intermediate vessel 14 and a second intermediate vessel 16 arranged side by side at the same level underneath the storage container 10. The first intermediate vessel 14 is made in the form of a lock chamber with an upper shut-off valve 18, a discharge cone 19 and a lower shut-off valve 20, so that the first intermediate vessel 14 can be filled with powdery solid from the storage container 10 through the upper shut-off valve 18 and emptied through the discharge cone 19 and the lower shut-off valve 20. The upper shut-off valve 18 advantageously comprises a flat slide valve 22 as a retaining device for the powdery solid in the storage container 10 and a ball valve 24 beneath it to provide a gas-tight seal. The lower shut-off valve 20 also comprises a ball valve to provide a high degree of gas-tightness. The reference number 28 designates a first weighing unit to ascertain the filling level in the first intermediate vessel 14. The second intermediate vessel 16 is made in the form of an injection chamber with an upper inlet 30 for filling from the first intermediate vessel 14 and a lower outlet opening 32. The reference number 34 designates a second weighing unit to ascertain the filling level in the second intermediate vessel 16. The reference number 38 is an overall designation for a fluidization device which is connected through a delivery valve 40 to the lower delivery opening 32 of the second intermediate vessel 16. This fluidization device 38 comprises a fluidization chamber 42 known in its own right with a gas feed unit 44. The latter advantageously comprises four shut-off valves 46-i, 462, 463, 464 in parallel, each followed by its own Laval nozzle 481, 482l 483l 484 to limit the volume of flow. The reference number 50 is an overall designation for a pneumatic intermediate conveying line which connects the shut-off valve 20 of the first intermediate vessel 14 to the upper inlet 30 of the second intermediate vessel 16 and conveys the powdery solid out of the first intermediate vessel 14 into the second intermediate vessel 16. This pneumatic intermediate conveying line 50 also comprises a fluidization chamber 52 known in its own right with a gas feed unit 54. The latter advantageously comprises two shut-off valves 56-1, 662 connected in parallel, each one followed by its Laval nozzle 681, 682 to regulate the volume of flow. An additional gas feed 60 is provided in the discharge cone 19 of the first intermediate vessel 14. This gas feed is also equipped with a shut-off valve 62 and a Laval nozzle 64. A common device for pressure maintenance resp. pressure release, is provided for the two intermediate vessels 14 and 16. The device for pressure maintenance comprises a common gas feed 70 with a regulator valve 72 and a first connection 73 with a first shut-off valve 74 to the first intermediate vessel 14 and a second connection 75 with a second shut-off valve 76 to the second intermediate vessel 16. The device for pressure release comprises a common gas release line 80 with a regulator valve 82 and a first connection 83 with a first shut-off valve 84 to the first intermediate vessel 14 and a second connection 85 with a second shut-off valve 86 to the second intermediate vessel 16. The reference number 90 designates a regulator which controls both the pressure maintenance regulator valve 72 and the pressure release regulator valve 82. This regulator 90 is connected to a first pressure sensor 92 in the first intermediate vessel 14 and a second pressure sensor 94 in the second intermediate vessel 16. In what follows, the mode of operation of the device schematically represented in Fig. 1 will be described. The first intermediate vessel 14 serves for the pneumatic transfer of the material to be conveyed out of the storage container 10 into the second intermediate vessel 16. The cyclical transfer process begins with the filling of the first intermediate vessel 14 from the storage container 10. For this purpose, the ball valve 24 and then the flat slide valve 22 are opened. The material to be conveyed flows by gravity from the storage container 10 into the first intermediate vessel 14. When the weighing unit 28 establishes that the maximum filling level in the first intermediate vessel 14 has been reached, the flat slide valve 22 and then the ball valve 24 are closed. The shut-off valve 84 in the pressure release line 83, previously open, is now closed. The first intermediate vessel 14 is pressurized by opening the shut-off valve 62. The Laval nozzle 64 limits the volume of flow. When the pressure sensor 92 establishes that injection pressure has been reached, the shut-off valve 62 is closed again. Once a minimum filling level is reached in the intermediate vessel 16, the pneumatic intermediate conveying line 50 is started. For this purpose, the shut-off valve 661 of the gas feed unit 54 is opened, and then the lower shut-off valve 20 of the first intermediate vessel 14 is opened. In the fluidization chamber 52, the fluidizing gas is mixed with the flow of solid matter. The Laval nozzle 58-| limits the volume of flow of the fluidizing gas. The solid-fluid mixture is transported by the pneumatic intermediate conveying line 50 to the upper inlet 30 of the second intermediate vessel 16. By means of the regulator valve 72, pressure in the first intermediate vessel is kept constant during the intermediate transfer. In this operation, the shut-off valve 76 is closed and the shut-off valve 74 is opened, and the regulator 90 regulates the pressure maintenance regulator valve 72 as a function of the measured values returned by the first pressure sensor 92. Once a minimum filling level has been reached in the first intermediate vessel 14, the lower shut-off valve 20 of the first intermediate vessel 14 is closed. The pneumatic intermediate conveying line 50 is flushed by opening the flushing valve 662. The Laval nozzle 682 determines the volume of flushing gas flow. After flushing of the pneumatic intermediate conveying line 50, the shut-off valves 56-|, 662 are closed. The regulator valve 72 is now switched on to the second intermediate vessel 16. This is done by closing the shut-off valve 74 and opening the shut-off valve 76. The pressure release regulator valve 82, however, is switched on to the first intermediate vessel 14. This is done by closing the shut-off valve 86 and opening the shut-off valve 84. By opening the pressure release regulator valve 82, the first intermediate vessel 14 can now be depressurized. Opening of the pressure release regulator valve 82 is controlled in proportion to the residual pressure (pressure sensor 92) in the first intermediate vessel 14 so that the volume of flow remains approximately constant over a wide range. The depressurized first intermediate vessel 14 is now weighed and the cycle starts again from the beginning. From the second intermediate vessel 16, the powdery solid is continuously injected into at least one of the two pneumatic conveying lines 12, 12'. To do this, the delivery valve 40 is opened and as it flows out, the powdery solid is mixed with carrier gas in the fluidization chamber 42. The carrier gas is fed into the fluidization chamber 42 from the gas feed unit 44. Depending on the gas flow needed to transport the powdery solid, one, two or three of the shut-off valves 46-i, 462, 46s are opened. The Laval nozzles 48-|, 482, 48s limit the volume of flow. They are so dimensioned that Laval nozzle 48-i passes one seventh (1/7), Laval nozzle 482 two sevenths (2/7) and Laval nozzle 48s four sevenths (4/7) of the maximum gas throughput required. In this way, the volume of flow of fluidizing gas can be increased in six steps of equal magnitude from 1/7 of the maximum gas throughput to 7/7 of the maximum gas throughput. By this means, practically continuous metering of the flow volume of fluidizing gas is obtained, without the need to have recourse to complicated flow rate measurements. The injection line can be flushed in the event of a disruption or a blockage. This is done by closing the shut-off valves 461, 462 and 463l and opening the shut-off valve 464. The Laval nozzle 484 determines the flushing gas flow rate. During injection, the pressure in the second intermediate vessel 16 is kept constant. Here, two operating conditions must be distinguished: whether the pneumatic intermediate conveying line 50 is in action or not. If the pneumatic intermediate conveying line 50 is not in action, the regulator valve 72 is switched to the second Intermediate vessel 16, i.e. the shut-off valve 74 is closed and the shut-off valve 76 is open. The pressure in the second intermediate vessel 16 is kept constant by the regulation circuit between the pressure sensor 94 and the regulator valve 72. When the weighing unit 34 detects a minimum filling level in the second intermediate vessel 16, the pneumatic intermediate conveying line 50 is activated. By closing the shut-off valve 76 and opening the shut-off valve 74, the regulator valve 72 is switched over to the first intermediate vessel 14. If the pneumatic intermediate conveying line 50 is in action, more powdery solid and carrier gas arrives in the second intermediate vessel 16 than is extracted from it by the injection process. The pressure in the second intermediate vessel 16 is then kept constant by controlled release of a specific quantity of gas. To do this, the regulator valve 82 is switched to the second intermediate vessel 16, i.e. the shut-off valve 84 is closed and the shut-off valve 86 is opened. The pressure in the second intermediate vessel 16 is kept constant by the regulation circuit between the pressure sensor 94 and the pressure release regulator valve 82. When filling of the second intermediate vessel 16 and flushing of the pneumatic intermediate conveying line 50 are complete, The pressure release regulator valve 82 is again switched to the first intermediate vessel 14 (i.e. the shut-off valve 84 is opened and the shut-off valve 86 is closed) and the regulator valve 72 is again switched to the second intermediate vessel 16 (i.e. the shut-off valve 76 is opened and the shut-off valve 74 is closed), so that the initial operating condition is reached once again. (TableRemoveds) We claim: 1. Device for continuously feeding a powdery solid from a storage container (10) into a pneumatic conveying line (12, 12'), comprising: a first intermediate vessel (14) taking the form of a lock chamber with an upper shut-off valve (18) and a lower shut-off valve (20), wherein the intermediate vessel (14) can be filled with powdery solid from the storage container (10) through the upper shut-off valve (18) and emptied through the lower shut-off valve (20); and a second intermediate vessel (16) taking the form of an injection chamber with an upper inlet (30) for filling from the first intermediate vessel (16) and a lower delivery opening (32) for continuously feeding the powdery solid into the pneumatic conveying line (12, 12'); characterized in that said first and second intermediate vessels (14 and 16) are located side by side, and between said lower shut-off valve (20) of said first intermediate vessel (14) and said upper inlet (30) of said second intermediate vessel (16), a pneumatic intermediate conveying line (50) with a fluidization device (38) provided, by means of which the powdery solid can be conveyed out of said first intermediate vessel (14) into said second intermediate vessel (16). 2. Device as claimed in claim 1, wherein said first intermediate vessel (14) and to said second intermediate vessel (16) are connected to a common pressure maintaining device (70, 72, 73, 74, 75, 76). 3. Device as claimed in claim 2, wherein said common pressure maintaining device (70, 72, 73, 74, 75, 76) consists of: a common gas feed (70); a pressure maintenance regulator valve (72) in said common gas feed (70); a first connection (73) with a first shut-off valve (74) connected to said first intermediate vessel (14); and a second connection (75) with a second shut-off valve (76) connected to said second intermediate vessel (16). 4. Device as claimed in claims 2 or 3, wherein said first intermediate vessel (14) and to said second intermediate vessel (16) are connected to a common pressure release device (80, 82, 83, 84, 85, 86) , said common pressure release device (80, 82, 83, 84, 85, 86) consisting of: a common gas pressure release line (80); a pressure release regulator valve (82) in said common gas pressure release line (80); a first connection (83) with a first shut-off valve (84) connected to said first intermediate vessel (14); and a second connection (85) with a second shut-off valve (86) connected to said second intermediate vessel (16). 5. Device as claimed in claims 3 and 4, wherein said pressure maintenance regulator valve (72) and said pressure release regulator valve (82) are operatively associated by a regulator (90). 6. Device as claimed in claims 1 to 5, wherein said fluidization device (38) is connected to a lower outlet opening (32) of said second intermediate vessel (16) and comprises a fluidization chamber (42) with a gas feed unit (44). 7. Device as claimed in claim 6, wherein: said gas feed unit (44) comprises three branches in parallel, each of said branches having a shut-off valve (46-i, 462, 463) and a Laval nozzle (48-|, 482, 483), and said Laval nozzles are dimensioned so that through the Laval nozzle (48-0 in the first branch passes one seventh, through the Laval nozzle (482) in the second branch two sevenths, and through the Laval nozzle (483) in the third branch four sevenths of the maximum gas throughput required. 8. Device as claimed in claim 7, wherein said gas feed unit has a fourth branch with a shut-off valve (464) and a fourth Laval nozzle (484), and this fourth branch is designed as a flushing gas supply. 9. Device as claimed in claims 1 to 7, wherein: said fluidization device (38) has a fluidization chamber (52) with a gas feed unit (54), and the gas feed unit (54) has two branches connected in parallel, each with a shut-off valve (561, 562) and a Laval nozzle (581, 582), one of said branches being designed as a flushing gas supply.

Documents:

5087-DELNP-2005-Abstract-(26-09-2008).pdf

5087-delnp-2005-abstract.pdf

5087-DELNP-2005-Claim (23-02-2009).pdf

5087-DELNP-2005-Claims-(06-03-2009).pdf

5087-DELNP-2005-Claims-(26-09-2008).pdf

5087-delnp-2005-clamis.pdf

5087-delnp-2005-complete specification (granted).pdf

5087-DELNP-2005-Correspondence-Others-(26-09-2008).pdf

5087-delnp-2005-correspondence-others.pdf

5087-delnp-2005-description (complete).pdf

5087-DELNP-2005-Drawings-(26-09-2008).pdf

5087-delnp-2005-form-1.pdf

5087-delnp-2005-form-18.pdf

5087-DELNP-2005-Form-2-(26-09-2008).pdf

5087-delnp-2005-form-2.pdf

5087-DELNP-2005-Form-3-(26-09-2008).pdf

5087-delnp-2005-form-3.pdf

5087-DELNP-2005-Form-5-(26-09-2008).pdf

5087-delnp-2005-form-5.pdf

5087-DELNP-2005-GPA (23-01-2009).pdf

5087-delnp-2005-gpa.pdf

5087-delnp-2005-pct-210.pdf

5087-DELNP-2005-PCT-304-(26-09-2008).pdf

5087-delnp-2005-pct-338.pdf

5087-delnp-2005-pct-409.pdf

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