WO1987005281A1

WO1987005281A1 - Method and apparatus for feeding an even flow of particulate material

Info

Publication number: WO1987005281A1
Application number: PCT/SE1987/000103
Authority: WO
Inventors: Jan-A^oke NILSSON; Bengt Hansson
Original assignee: Rippelton N.V.
Priority date: 1986-03-10
Filing date: 1987-03-04
Publication date: 1987-09-11
Also published as: SE8601091L; SE8601091D0; AU7128087A

Abstract

When a variable but regular flow of a particulate material is dosed, an apparatus is used, which includes a storage container (1) for the material (7), a packing chamber (2) for the material (7'), means (3, 9) in order to convey the material (7) from the storage container to the packing chamber, as well as means (3, 8) in order to pack the material (7') in the packing chamber to a certain packing degree, so that it gets a certain volumetric weight, which is constant for the material.

Description

METHOD AND APPARATUS FOR FEEDING AN EVEN FLOW OF PARTICULATE MATERIAL

The Technical Field

The present invention relates to a method and an apparatus for a dosage of a regular but variable flow of a particu- late material to a recipient. More specifically, the in¬ vention relates to a method and an apparatus, in which the material from a storage container is fed to a packing chamber, in which the material is packed to a certain pac¬ king degree and consequently to a certain volumetric weight, which is related to the material of interest, after which the material is discharged with a certain regular volumet- ric amount per unit of time. The present invention has been developed in order to handle biological fuels, the volumetric weights of which may vary to a high degree de¬ pending to the packing degree, primarily chopped straw and other fragmentized straw products, but it is advanta- geous to use it also for other solid fuels, e.g. fragmen¬ tized paper, as well as for other particulate materials than solid fuels, e.g. for dosage of cattle-food materials to a pelletizer device.

The Background of the Present Invention

A demand which can be made upon e.g. a device for dosage of solid fuels to a burner, which functions continuously and to which solid fuels are fed continuously, is that it deliver a regular flow to the burner. The dosage can as a principle be either volumetric or gravimetric. Gravimetric dosage normally means a continuous weighing, if the dosage is to take place continuously, which requires a quite ex¬ pensive apparatus. Volumetric dosage in return requires, that the volumetric weight of the material is known. In the art there is no technical and economically acceptable solution to the problem of a volumetric dosage of particu- late material in the form av chopped straw and similar comp¬ ressible materials.

A Brief Description of the Present Invention

The object of the present invention is to suggest a method and an apparatus for a volumetric dosage of a regular but variable flow of a particulate material, which may be highly compressible, e.g. chopped straw, fragmentized paper and the like.

In accordance with the present invention the material is packed by means of at least one rotary packing roll, which is disposed between the storage container and the packing chamber, which packing roll constitutes the bottom of the storage container, and at the same time it conveys the mate¬ rial from the storage container to the packing chamber as well as gives the material in the packing chamber a certain volumetric weight, which is related to the material of in¬ terest.

From the packing chamber the material can be discharged by means of a dosage roll, which during every turn picks up a certain volume of the material from the packing chamber and delivers this amount of material to a duct outside the pac¬ king chamber. From there the material is pneumatically con¬ veyed via said duct to a recipient, which can be a burner, in case the particulate material is a solid fuel.

In accordance with a preferred embodiment of the apparatus of the present invention the packing roll or packing rolls, which are disposed between the storage container and the pac¬ king chamber, are provided partly with means designed to re- turn the excess material to the storage container, so that the volume of the material in the packing chamber all the time is kept constant, and partly with means designed to exert a pressure against this constant volume of particu¬ late material, so that also the packing degree in this vo¬ lume is kept constant. Preferably these elements, i.e. the return feeders and the "packers", are integrated in one and the same packing roll and suitably two such pac¬ king rolls are disposed in parallell with each other bet¬ ween the storage container and the packing chamber. Pre¬ ferably the storage container is disposed above the pac- king chamber, so that the material in the storage contai¬ ner is fed downwards towards the packing rolls by its own weight and so that the material in the packing cham¬ ber is fed downwards against the dosage roll by means of a combined action of the packing rolls and the weight of the material.

Additional characterizing features and attributes as well as advantages of the present invention are stated in the patent claims and the following description of a preferred embodiment.

A Brief Description of the Drawings

" In the following description of a preferred embodiment reference is made to the accompanying drawings, which schematically shows a vertical section of the apparatus according to the present invention.

A Description of a Preferred Embodiment

The main components of the apparatus are made up of a sto¬ rage container 1, below it a packing chamber 2, between storage container 1 and packing chamber 2 two packing rolls 3, a dosage roll 4 in the bottom of packing chamber 2, a pneumatic conveyor duct 5 and a separator 6. A fan in the conveyor duct has reference numeral 18. In storage container 1 there is a supply of the used so¬ lid fuel 7, e.g. chopped straw. Storage container 1 is gradually filled with new fuel 7, when the fuel is dis¬ charged from the lowermost portion. The storage container can e.g. be equipped with level guards, which inform of when the container is to be filled (20) and when it is filled (21) . The bottom of storage container 1 is made up of packing rolls 3, which are provided with two types of pins, namely resilient helical pins 8 and rigid radial pins. The number of packing rolls is two in this embodi¬ ment. Each packing roll 3 is provided with four resilient and four rigid pins 8 and 9 respectively. Packing rolls 3 are disposed in a space 10 called a middle section. Sides 11 of the middle section have a cylindrical shape.

Packing rolls 3, which rotate with opposite directions, have three functions. Firstly, they constitute the bottom of storage container 1. Secondly, they convey fuel 7 down¬ wards to packing chamber 2 through middle section 10. Thirdly, they give the fuel in packing chamber 2'a cons¬ tant volumetric weight. The resilient, helically bent pins 8 are then used to compress fuel 7¹ in packing chamber 2 above dosage roll 4 to a certain volumetric weight. Rigid pins 9 are primarily used to feed fuel 7 downwards from storage container 1 to packing chamber 2 but also to re¬ turn the excess material upwards to storage container 1 through middle section 10, so that all the time a constant volume of fuel 7' in packing chamber 2 is maintained. Thus, when level 12 in packing chamber 2 rises, so that it is reached by rigid pins 9, the latter will convey the ex¬ cess back to storage container 1.

Dosage roll 4 is disposed in the lower, trough-shaped pro¬ jection 13 below packing chamber 2. In this trough-shaped projection, which is provided with a cylindrical bottom portion 14, dosage roll 4 rotates. Its speed provides the desired fuel flow and is controlled by the heat require¬ ment of the succeeding boiler. Dosage roll 4 and packing rolls 3 rotate by means of not shown driving means. Dosage roll 4 comprises a perforated tube 15, which is provided with radially, possibly somewhat forwardly bent, outwardly directed barbs 16. Inside tube 15 a nozzle 17 is disposed having a narrow gap arranged in the longitudinal direction of the roll. Return air 19 flows through this gap, is then fed through the perforations of the dosage roll, hits the conveyed fuel, which is in this way removed from the barbs, and is then discharged through duct 5.

-Dosage roll 4 has also three functions. It is designed to pick up fuel 7¹ having a certain volume weight from packing chamber 2. It is also designed to convey this fuel to the nozzle area and to deliver this amount of fuel to the air stream in pneumatic conveyor-duct 5. In order to give the boiler, to which the dosage device is connected, a large range of control, the fuel conveyor air flow must be as small as possible. At the same time a certain air flow is required in order to loosen the fuel from dosage roll 4. In order to meet these two requirements a cyclone separa¬ tor 6 is disposed in front of the burner chamber. The re¬ turn air from the cyclone separator is used to loosen the fuel from dosage roll 4 and blow it into conveyor duct 5.

The amount of air, which flows to the boiler, is fed into the dosage device from the ambient air. Consequently, the dosage device works free from dust, which is very impor- tant in order to prevent dust explosions.

Claims

Claims:

1. A method of dosing a variable but regular flow of a particulate material (7,7*), in which the material from a storage container (1) is fed into a packing chamber (2) , in which the material (7') is packed to a certain packing degree and consequently to a certain volumetric weight, which is related to the used material, after which the ma¬ terial is discharged from the packing chamber with a cer- tain volumetric amount per unit of time, c h a r a c -

^" t e r i z e d in that the material (7') is packed by means of at least one rotary packing roll (3) , which is disposed between the storage container (1) and the packing chamber (2) , which packing roll constitutes the bottom of the sto- rage container, while it at the same time conveys the ma¬ terial (7) from the storage container to the packing cham¬ ber as well as gives the material (7') in the packing cham¬ ber said volume weight, which is related to the used mate¬ rial.

2. A method according to claim 1, c h a r a c t e r i z e d in that the packing roll also conveys an excess material from the packing chamber back to the storage container.

3. A method according to claim 1 or 2, c h a r a c ¬ t e r i z e d in that the material is discharged from the packing chamber by means of a dosage roll (4) , which for each -turn picks up a certain volume of material from the packing chamber and delivers this amount of material to a duct (5) outside the packing chamber, and that the material via said duct is pneumaticly conveyed to a recipient.

4. A method according to any of claims 1-3, c h a r a c ¬ t e r i z e d in that the material is a solid fuel and that the recipient is a burning chamber.

5. An apparatus for dosage of a regular flow of a parti¬ culate material, which includes a storage container (1) for the material (7) , a packing chamber (2) for the mate¬ rial (7'), means (3,9) which convey the material (7) from the storage container to the packing chamber, as well as means (3,8), which packs the material (7') in the packing chamber to a certain packing degree, so that it gets a certain volume weight, which is constant for the material, c h a r a c t e r i z e d by one or several packing rolls (3) between the storage container (l)and the packing cha - ^• ber (2) .

6. An apparatus according to claim 5, c h a r a c t e ¬ r i z e d in that the storage container (1) is disposed above the packing chamber (2) and that the packing roll or the packing rolls (3) are disposed therebetween in order to partly constitute a bottom in the storage container (1) , partly convey the material (7) from the storage container (1)downwards into the packing chamber (2) and partly comp- ress the material (7¹) in the packing chamber (2), so that it gets a volumetric weight, which is constant for the used material.

7. An apparatus according to claim 6, c h a r a c - t e r i z e d in that the packing roll or the packing rolls are provided with rigid carriers (9) in order to feed downwardly the material (7) from the storage contai¬ ner (1) to the packing chamber (2) and in order to feed the excess material from the packing chamber (2) back into the storage container (1) as well as resilient ele¬ ments (8), which, when they spring outwards, have a lar¬ ger, radial length than the rigid carriers, in order to pack the material (7') in the packing chamber (2) to a constant volumetric weight.

8. An apparatus according to any of claims 5-7, c h a - r a c t e r i z e d in that a dosage roll (4) is dis¬ posed in a space below the packing chamber (2) .

9. An apparatus according to any of claims 5-8, c h a - r a c t e r i z-e d by a pneumatic conveyor duct (5) , whichconveys the material, which is portioned out from the dosage roll, towards a recipient, a separator, which separates the main part of the amount of air from the fed material, as well as a return air duct (20) from the sepa- rator in order to blow out material, which is fed by means of the dosage roll.

10. An apparatus according to any of claims 5-9, c h a ¬ r a c t e r i z e d in that said material is solid fuel and that said recipient is a burning chamber.