WO2006098692A1

WO2006098692A1 - Device for transport of granular material

Info

Publication number: WO2006098692A1
Application number: PCT/SE2006/050019
Authority: WO
Inventors: Tuomo Kainulainen; Bengt Greus
Original assignee: Swedish Bioburner System AB
Current assignee: Swedish Bioburner System AB
Priority date: 2005-03-14
Filing date: 2006-03-01
Publication date: 2006-09-21
Anticipated expiration: 2007-09-14
Also published as: SE528393C2; SE0500575L

Abstract

The present invention relates to a device for transport of granular material, comprising a container having an upper part (4), a lower part (1), at least one inlet (3), at least a first outlet (2) for the granular material, as well as a second outlet for a transport medium, said container being arranged to be connected to an appliance for achieving a vacuum 5 (5) in said container, via said outlet for the transport medium, said inlet (3) for the granular material being arranged to be connected to a transport system, such as a hose or pipe system, for transport of the granular material to the container by said transport medium, and said first outlet (2) being positioned at a lower level than said inlet (3) and comprising an opening means (9) for opening and closing of said first outlet (2), 10 wherein the container comprises a lifting means (6) that can be influenced by the transport medium, the lifting means (6) and the opening means (4) being mechanically interconnected, whereby control of the opening means takes place by said transport medium.

Description

DEVICE FOR TRANSPORT OF GRANULAR MATERIAL

TECHNICAL FIELD The present invention relates to a device for transport of granular material, comprising a container having an upper part, a lower part, at least one inlet, at least a first outlet for the granular material, as well as a second outlet for a transport medium, said container arranged to be connected to an appliance for achieving a vacuum in said container, via said outlet for the transport medium, said inlet for the granular material arranged to be connected to a transport system, such as a hose or pipe system, for transport of the granular material to the container by said transport medium, said first outlet being positioned at a lower level than said inlet and comprising an opening means for opening and closing of said first outlet.

PRIOR ART

It is known to use mechanical transport screws to feed fuel pellets to a combustion device or to intermediate storing in connection with the combustion device. In recent years, such transport screws have been developed from comprising only straight screws to now also comprising flexible screws. By this development, it has become possible to feed pellets directly from a large supply, where the positioning of the supply is more flexible than before. Hereby, advantages can be attained in terms of choice of room, replenishment of the supply etc. The flexibility is however not unlimited, but still the positioning is determined by the distance to the combustion device. Also the bend radiuses constitute a limitation to the flexible feed screws. It is realised that at shutdown it can be complicated to deal with the problem, which e.g. is due to a pellets jam inside the screw. It is also a known problem that transport by pellets screws puts specific requirements on the strength of the pellets. The dimensions of the pellets will furthermore affect its transporting properties. Since the pellets screw functions also to supply the correct amount of pellets to the burner, the systems are designed such that the pellets will fall down to the burner by gravity. This may also result in the breaking of pellets. Due to the limitations according to the above, the systems will most often be unnecessarily space demanding.

Another way of transporting fuel pellets is by pneumatics, whereby fast flowing air takes care of the transport. The applicant is aware of a device for pneumatic transport, in which a cyclone suction apparatus is used to collect a certain amount of pellets. When the container is filled with a desired amount of pellets, a feed screw in the bottom of the container is activated, which feed screw feeds forward pellets to the combustion device. Such a device is both expensive and complicated.

A system for pneumatic transport of granular materials is previously known for industry and farming. One example of this is a cyclone suction apparatus called ISU 2553 and marketed by the company Swedish Eurovac in Falkenberg, website www.eurovac.nu, and that is used within metal and plastics industry to suck up granules, metal shavings, dusts etc. The feeding out of sucked up material takes place automatically by aid of a flap valve and down into a waste container e.g., after each finished sucking up. Cyclone suction apparatuses comprise air filters that have to be cleansed regularly, which takes place by manual external shaking of the filter or by pneumatic filter shaking cleansing. Swedish Eurovac also markets a dust separator called BMS-020 and that is provided with automated back flushing for filter cleansing.

Another example of a pneumatic transport device is the central vacuum cleaner Husky 325 marketed by KEK Projektering in Enkδping, Sweden, with the website www.k- ek.nu, which central vacuum cleaner can be used together with an initial separator to suck up dust, hair, shavings, feed residues and water in livestock stables. The initial separator consists of an oil drum with a specially designed cover, which drum acts also as a collecting container, the largest part of the sucked up material being separated off before reaching the actual vacuum cleaner.

BRIEF ACCOUNT OF THE INVENTION

It is an object of the present invention to provide for a device for pneumatic transport of a granular fuel, such as pellets, shavings or grain, from a supply and to a combustion device, which device eliminates or at least minimizes today's transport screw problems. It is also an object of the invention to provide for a device that is considerably easier to manufacture and handle, and that results in simplified and improved operating conditions in relation to the devices for pneumatic transport of granular fuel that the applicant is aware of, as discussed above.

Yet another object of the invention is to provide for a transport device for granular material, such as grain or feeding pellets, which can be used in industry and farming in order in a simple and flexible way to transport and dose such material.

At least one of the above mentioned objects is achievable by a device for transport of granular material, such as fuel pellets, shavings, grain or feeding pellets, comprising a container having an upper part, a lower part, the container comprising at least one inlet and at least one outlet for the granular material, said outlet being positioned in the lower part of the container and at a lower level than said inlet for the granular material, and an outlet for a transport medium, said container being arranged to be connected to an appliance for achieving a vacuum in said container, via said outlet for the transport medium, said inlet for the granular material being arranged to be connected to a transport system, such as a hose or pipe system, for transport of the granular material to the container by said transport medium, said outlet for the granular material comprising an opening device to open and close said outlet for the granular fuel, and said container comprising a filter for separation of the granular fuel and the transport medium, characterised in that the valve and the filter are mechanically connected to each other by a power transmission and that they are arranged to cooperate with the motor in order to fill and empty the container with the granular fuel.

Thanks to the invention, a device is provided for transport of granular material, such as fuel pellets, shavings, grain or feeding pellets, which device enables a more flexible solution to the positioning of the supply in relation to the device.

According to yet another aspect of the invention, a device is provided in which the influence of the transport itself on the granular material decreases in relation to devices of today.

Additional advantages of the invention are clear from the description below, the claims and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail with reference to the attached drawing figures, of which:

Fig. 1 shows a view in perspective of a preferred embodiment of the transport device,

Fig. 2 shows a view in cross-section of a preferred embodiment of the transport device in a filling position,

Fig. 3 shows a cross-section of the transport device in emptying position,

Fig. 4 shows the transport device and a connection to a tipping chute, Fig. 5 schematically shows a system for pellets firing, comprising a transport device according to the invention, and

Fig. 6 shows a detail of the transport pipe. DETAILED DESCRIPTION OF THE INVENTION

In the detailed description of the drawings, the device will be described and exemplified in an embodiment intended for transport of fuel pellets, from a pellets supply to a pellets burner. Primarily, the device is intended to be used to feed- forward granular fuel and granular feed, but it is realised that other fields of application can exist, such as a feeding-forward and dosing device in various industries that handle granular materials. Particularly, the device is suitable for use when the material fed forward is required in several different places.

Fig. 1 shows a view in perspective of a preferred embodiment of the transport device. The device comprises a container with a lower part 1, an upper part 4 and an inlet 3 and an outlet 2 for the granular material.

Fig. 2 shows a preferred embodiment of the transport device in a filling position, as seen in cross-section. The device comprises a container for collection of the granular material. In a preferred embodiment, the container is formed from a shell shaped as a cyclone, which forms the lower part 1 of the container, in its lower portion having an outlet 2 for the granular material. The lower part 3 also comprises an inlet 3 for the granular material, which inlet suitably has a conventional design in order to achieve a tangential approach flow of the granular material. The container also comprises an upper part 4 that in this embodiment accommodates a vacuum device 5, most simply in the form of a conventional vacuum cleaner motor or in the form of an electric motor and an impeller, in order to achieve a vacuum in the container. The upper part has a perforated shell for evacuation of the transport medium. A dust filter 6 is arranged in connection with the upper end of the lower part, at a level above the inlet 3, in order to catch any fine shavings and dust. To prevent the dust filter from being sucked into the vacuum device, a perforated plate 7 is arranged between the dust filter and the motor unit. The perforated plate may also have the object of constituting a holder-on for a rod 8 that connects the dust filter with a cover 9 positioned in connection with the outlet in the lower end of the container. Suitably, the rod is mounted in the centre of the cover and the filter.

In a preferred embodiment, the rod 8 will however not abut the plate 7 as the filter 6 is sucked up, in order to ensure a snug fit between the cover 9 and the outlet 2 in the bottom of the container. In order to achieve a snug fit, the cover and the rim of the outlet are suitably shaped to match to each other. The rim of the outlet and/or the cover can also be provided with a rubber gasket (not shown), which will also lead to a dampening of the sound that arises as the cover is closed. Furthermore, it is an advantage if the shape of the cover contributes to a positioning of the cover in the opening, but in order to ensure this, the device may be provided with a rod guide in the form of a sleeve 10 that surrounds the rod. This sleeve also contributes to protect the rod from neighbouring pellets. It has been shown, namely, that neighbouring pellets may result in a locking of the rod, which renders the emptying more difficult. This phenomenon is particularly pronounced in use of a threaded rod, which has been the case in tests with a rod for screwed attachment in the filter and the cover, wherein the position of the filter and the cover can be varied along the rod.

According to yet another aspect, it is an advantage if the shape of the cover contributes to the falling down of the granular material from the cover, and this in a controlled manner without spreading of the material. In this preferred embodiment of the device, the cover has therefore been given the shape of an upside-down funnel, but also a cover with a surface that is convex in the direction of flow, which results in at least one or some of the above mentioned advantages being attained.

The filter 6 is shaped to allow for a movement that oscillates in a vertical direction, between upper and lower end positions. The drawing shows the device when the filter is in its upper end position, which is achieved by a starting of the motor, and which creates a vacuum in the container, which in turn results in a flow of air into the container. Hereby, the filter 6 is lifted up to the perforated plate 7, and the cover 9 is lifted up via the rod 8, to give a tight fit with the outlet 2. Hereby, the flow of air into the container is concentrated to the inlet 3, and granular material can be transported from a remote supply to the container via a pipe or hose system. For transport of regular sized pellets, i.e. pellets with a size of 4-10 mm in diameter, an air flow of at least 25-30 m/s is required. In connection with faster air flows, noise problems will eventually occur in the form of whistling and rattling in the pipes, but in return, pellets can be transported longer distances. Of course, noise can be muffled by isolation around the pipes.

It is realised that it is an advantage that fibres and dust will not penetrate into and get caught in the filter 6, impairing the suction of the device and meaning that the filter quality must be chosen to minimize this. For this reason, tests have been made with loose filters, the primary task of which is to act as a lifting device for the cover. Such a "filter" will catch no or a few particles, and the transport device should then be equipped with a means for recirculation of the transport air, in order to avoid fibres and dust from being spread in the air, or alternatively the air is led out through an outer wall.

Fig. 3 shows a cross-section of the transport device in an emptying position, i.e. in the lower end position. This is also the position of the container when the motor is not in operation. In the shown position, the filter 6 is in a fully extended position, and the cover 9 is freely suspended in the filter, via the rod 8. At the attachment of the rod in the filter, there is a reinforcement in the form of a washer 11 with a simple snap locking, in order to enable easy changing of filters. Furthermore, the filter is attached to the wall of the container by the wall being provided with a rim 12 for a snap fit. The described attachments are only examples of possible attachments, and should not be seen as limiting to the invention.

According to the concept of the invention, the gravity of the granular material is enough to open the cover as the filling of the container has been completed and the motor has been shut off. If desirable, the cover can of course be made heavier, or weights can be hooked onto the cover, suitably on the underside of the cover, inside the funnel. It has been shown that when the container is full, there should be a certain space between the filter and the upper level of the pellets filled- in, or the device may self-lock whereby emptying is prevented. In tests, a well functioning emptying has been achieved with a gap of about 50 mm in height, between the filter and the pellets, which is approximately half the amplitude of the oscillating movement of the device used in the tests. It remains to be established more precisely which smallest size of the space that can be used, but it is realised that when the motor is shut off and the pellets are pressing the cover downwards, a relative movement results between the cover and the upper level of the pellets, due to the shape of the container. From that aspect, it is realised that if reasonably fast emptying is desired, this has to be taken into account, such that an adequately large gap is initially formed between the cover and the rim of the opening. Knowing the smallest required height of said space may also be of importance if the filling degree of the container is to be optimized.

In a preferred embodiment, the device is dimensioned such that when the cover is opened, by being pressed down by the granular material, the filter is extended with a light jerk in the lower end position. This results in the positive effect of an automated filter cleansing. Therefore, no manual filter cleansing or back-flushing according to prior art, is required. It is realised that the above mentioned solution for emptying of the device and at the same time achieving a filter cleansing, is of essential importance to the inventive device, since the feeding forward of pellets takes place more or less continuously over the day. The user-friendliness in the form of a decreased manual input is an important argument for increased use of pellets in heating, in particular for owners of private houses that can not themselves supervise their heating plants. It is also realised that a filter cleansing that requires no back-flushing is of critical importance, since back-flushing most likely would mean that the back-flushing air interferes with the operation of the combustion device.

The basic principle for filling and emptying of the device is based on achieving a differential pressure on the filter, where the pressure above the filter is lower than the pressure below the filter. It is also realised that the differential pressure on the filter must be large enough also to counteract that the gravity of the granular material inside the container opens the cover in the bottom of the container during filling. The following relation should exist: P2-Pl>mg, where

Pl is the pressure above the filter, in connection with the first outlet,

P2 is the pressure below the filter, in connection with the inlet for the granular material, and mg is the mass of the granular material inside the container.

The basic concept can be developed to achieve additional advantages, and Fig. 4 shows a cross-section of how the transport device can be connected to a tipping chute 13. In order to minimize dusting in connection with the combustion device, the coupling of the transport device with the tipping chute may suitably be provided with a foam rubber packing 14 that prevents dust from whirling up from the tipping chute as the transport device is emptying its content. This foam rubber packing also has the advantage that it allows for a certain flow of air, which is important from a safety point of view. In the event that the cover 9 has not been properly closed when the motor starts, e.g. due to pellets being clamped in the opening 2, air will be sucked back-ways through the opening. If the connection between the tipping chute and the container was instead air tight, it would be possible for hot combustion air to be sucked into the device, thereby causing a backfire. Another way of achieving this protection against a backfire, is to provide the wall in the tipping chute with aerating holes 15 that are covered by a tiltable cover or a rubber cloth 16 on the inside of the pipe, which allows for air to flow into the pipe but prevents pellets from flowing out. Fig. 5 shows a transport system for pellets, from a pellets supply 17 and to a combustion device 18, including a transport device according to the invention. In the figure, the container according to the invention is mounted above a short tipping chute 13 that is connected directly to the pellets burner and that is provided with a level indicator 19, in order to indicate if pellets filling is required. As is conventional, the tipping chute may comprise a dosing device that is controlled by the fuel requirement of the burner, and that may beneficially be an intermediate supply integrated with the burner.

The container is supplied with pellets from the pellets supply 17. The pellets supply is provided with a dosing screw 25 that at a given signal feeds forward pellets from the supply, at a suitable rate, to one end of a hose/pipe 20, the other end of which is connected to the inlet 3 of the transport device. Control equipment of conventional type is arranged for control and operation of the system, which equipment is not described in detail. The function of the system will now be described with reference to this simple embodiment of a feeding system.

When the tipping chute calls for pellets, a signal is given to the motor 5 of the feeding- forward device, which starts, whereafter the filter 6 exerts a lifting force on the cover 9 that closes. The air flow is concentrated to the transport pipe 20, and after a predetermined time period, such as 20 sec, the dosing screw 19 starts to feed forward pellets from the pellets supply 17, at a given rate. Pellets are transported to the container, and when it has been filled up to a given level, the level indicator 21 indicates that the forward-feeding is to be ended. The pellets screw is shut off by a signal, and after a predetermined time period, adapted to empty the transport pipe 20, the motor is shut off. As the suction decreases, the gravity of the pellets will affect the cover that will then be pushed downwards, whereby pellets can fall out of the container and into the tipping chute. If the tipping chute calls for more pellets, the procedure is repeated, but most beneficially a single filling is enough to fill the tipping chute. Hereby, the procedure can be secured by a control function that shuts off the entire feeding system, if no signal for a full tipping chute has been given within a given time period after the signal for an empty tipping chute. In this way, there is a distinct filling operation, which is advantageous from an operational point of view in order to minimize the risk of overfilling in the event that the level indicator fails or that the feeding forward of pellets does not work, leading to a risk of continuous operation of the system.

As mentioned before, noise may arise from high velocities in the transport pipe. A way of muffling this noise can be to design the system with the transport of pellets and the recirculation of air as "pipe in pipe", which also may simplify the installation. It is shown in Fig. 6 that the recirculated air can be led in an air gap 26 between an outer pipe 27 and an inner pipe 28, where the inner pipe is used for the pellets transport. In both ends of the transport pipe, the outer pipe is deflected, most simply by a conventional 45° pipe bend 29, whereby an inlet and an outlet for the transport air, to and from the air gap 26, respectively, is achieved. In the front end of the transport pipe, adjacent the feeding-forward screw from the pellets supply, the recirculated air is then returned to the transport pipe, which can take place in different ways.

One way of returning the recirculated transport air is to use it also to create beneficial conditions from a flow point of view, in connection with the inlet opening of the transport pipe. This may be achieved for example by allowing the recirculated air to whirl around the pellets that is directly in front of the inlet opening of the hose/pipe. It may also be suitable to use the recirculated air to guide the pellets fed forward to the inlet opening, in the appropriate direction.

According to yet another aspect of the invention, it is beneficial if the feeding forward of pellets from the pellets supply, to the inlet opening of the transport pipe, takes place in a manner such that there is no risk of pellets forming lumps (compare the forming of lumps at the inlet of the hose of a vacuum cleaner).

As described above, a system with recirculated air may allow for a use of the recirculated air to achieve good feeding-forward conditions. Within the scope of the invention, the applicant has developed a special pipe branching that is connected to the transport screw at the pellets supply. This pipe branching, in the form of a pipe with essentially the same diameter as the pipe that surrounds the transport screw, is mounted between the front end of the pellets screw, as seen in the transport direction, and the motor 22, and comprises an inlet in the pipe wall for any recirculated air. Preferably, a plurality of such inlets are arranged in the pipe wall and positioned such that the pellets fed forward is brought to whirl around/float inside the pipe. Preferably, at least one of said inlets is positioned such that the inflowing air has a flow direction that guides the whirling pellets to an outlet to which the transport pipe is connected.

According to the invention, said pipe branching can also be provided with means 23, 24 for breaking very long pellets that otherwise risk to cause a flow stoppage or are not fed forward at all. Tests have shown, namely, that very long pellets tend to orient themselves in the flow direction, falling to the bottom of the transport pipe. In time, they will cause a local reduction of the cross- sectional area of the pipe, which in turn leads to an increase in flow velocity. At a certain flow velocity, such long pellets will be sucked up momentary, which may result in troubles.

Said means for breaking very long pellets comprises at least two holding-on tools 24 arranged axially on both sides of the outlet inside the pipe branching. Most simply, the holding-on tools are two screws that have been screwed from the outside of the pipe. Furthermore, said means comprises at least one paddle 23 mounted on a rotary shaft, suitably the drive shaft of the pellets screw. Very long pellets can be broken by counteraction of the holding-on tools and the paddle.

The device shown in the figures has been described in connection with an application for transport of fuel pellets, but according to the scope of the invention, it can be used also for transport of other granular materials, such as grain, feeding pellets and flour. For example in connection with the feeding of animals, the device can be used to dose a suited amount of feed directly into each animal's manger. In such an application, the device is equipped with control devices that enable forward- feeding of a varied amount of feed, or it is suspended in a scale in order to manually interrupt the filling when a correct amount of feed has been filled in. The device may also be equipped with a plurality of inlets that can be used simultaneously or independently, in order thereby to be able to fed forward different types of feed. Suitably, the device is mobile and the feed is transported in a hose system that is arranged in an extension system with guide rails, in the ceiling, such as a known system for the transport of exhaust gases from vehicles.

ALTERNATIVE EMBODIMENTS

Alternative embodiments may exist within the scope of the invention. It is realised that the shape of the container need not be as the preferred one. The container may for example have a circular or cylindrical shape. The vacuum device need not be arranged in direct connection with the container, but can be located elsewhere and be connected with the container via a hose or a pipe. If it is desired to dose a larger amount of pellets, the volume of the device can be increased, which is most easily achieved by increasing the distance between the outlet and the inlet for the granular material. In the preferred embodiment, a product programme can be designed that makes use of the same filter dimension and motor, by a building-up system with extension rings in the form of cylindrical container sections. Since some filter types need to be cleansed after some time, it is realised that if the volume of the device is increased, the filter will be the limiting factor, which means that it is conceivable also to increase the diameter of the container in order to scale up the device. The skilled man also realises that containers with non-dust-collecting filters and recirculation of the transport air need not be limited in this way. The skilled man also realises that the air permeation of the filter, the distance to the pellets supply and the pipe dimension all affect the air flow and that the motor has to be adapted to these circumstances, to achieve proper operational conditions.

Claims

A device for transport of granular material, comprising a container having an upper part (4), a lower part (1), at least one inlet (3), at least a first outlet (2) for the granular material, as well as a second outlet for a transport medium, said container being arranged to be connected to an appliance for achieving a vacuum (5) in said container, via said outlet for the transport medium, said inlet (3) for the granular material being arranged to be connected to a transport system, such as a hose or pipe system, for transport of the granular material to the container by said transport medium, said first outlet (2) being positioned at a lower level than said inlet (3) and comprising an opening means (9) for opening and closing said first outlet (2), characteri se d in that the container comprises a lifting means (6) that can be influenced by the transport medium, and that the lifting means (6) and the opening means (9) are mechanically interconnected, whereby control of the opening means (9) takes place by said transport medium.

2. A device according to claim 1, characteri s e d i n that said appliance for achieving a vacuum (5) is used to control the flow velocity of said transport medium, in order thereby to fill and empty the container with/of the granular material.

3. A device according to claim 2, characteri s e d in that said appliance for achieving a vacuum (5) comprises a vacuum motor or a motor connected with an impeller.

4. A device according to claim 1, ch aracteri s e d in that the device comprises means for controlling the flow velocity of said transport medium inside the container, in order thereby to fill and empty the container with/of the granular material.

5. A device according to claim 4, ch aracteri s e d in that said means is arranged between said lifting means (6) and said appliance for achieving a vacuum (5).

6. A device according to claim 4, characteri s e d i n that said means comprises throttle devices, such as dampers or valves.

7. A device according to claim 1, characteri s e d in that said lifting means (6) and opening means (9) are mechanically interconnected by a power transmission (8) that acts by an essentially axial oscillating movement between two end positions.

8. A device according to claim 7, characteri s e d i n that said end positions are a closed position of the first outlet d for filling of the container, and an open position for filling of the container, respectively.

9. A device according to claim 7, ch aracteri s e d in that said lifting means (6) is arranged in connection with said outlet for the transport medium, essentially perpendicularly to the axial movement of the power transmission (8).

10. A device according to claim 9, ch aracteri s e d in that the power transmission (8) is attached at a point that is essentially centrally positioned on the lifting means (6).

11. A device according to claim 7, characteri s e d in that said lifting means (6) comprises a dust filter (6), formed from a flexible material that allows for the oscillating movement of the power transmission (8).

12. A device according to claim 7, characteri se d in that the opening means (9) comprises a cover (9) that in closed position allows for an essentially air tight fit with the outlet for the granular material.

13. A device according to claim 12, ch aracteri s e d i n that the cover (9) has a conical or convex shape, as seen in the flow direction for the granular material.

14. A device according to claim 12, ch aracteri s e d i n that the power transmission is attached at a point that is essentially centrally positioned on the cover (9). 5. A device according to any one of the preceding claims, characteri s e d i n that the container is shaped as a cyclone, the lifting means (6) being positioned such that the inlet (3) and the first outlet (2) for the granular material are below the lifting means (6), while the second outlet for the transport medium is above the lifting means (6).