GB2104097A

GB2104097A - Fuel from spent chicken litter, paper, and wood

Info

Publication number: GB2104097A
Application number: GB08120983A
Authority: GB
Inventors: John Henry Stanbury
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-07-07
Filing date: 1981-07-07
Publication date: 1983-03-02

Abstract

A mixture of milled spent litter from the broiler industry, paper and wood products is passed through a press to form combustible pellets the percentage by weight of the milled spent litter being between 40 and 70%, of the weight of the final product, and the relative percentages of the components being such that the water content of the final product is not above 15% of the total weight thereof.

Description

SPECIFICATION Manufacture and composition of combustible materials The present invention concerns the manufacture and composition of combustible materials. The combustible materials with which the present invention are concerned can be used both for burning in domestic fires and for industrial heating purposes.

The invention has for an object to provide combustible materials which are manufactured from products which would otherwise be wasted.

In particular the invention proposes using as a major constituent in the manufacture of combustible material spent litter which has previously been used in the rearing of broiler chickens.

Various types of litter are known and the most common type in present use is basically constituted by wood shavings. Another type of litter is that disclosed in the specification of British Patent Application No. 8026010. It will be appreciated that the latter specification discloses a method of manufacturing litter for livestock, and particularly for broiler chickens, which uses waste products to manufacture the litter. The result of this is that the present invention is particularly satisfactory from an ecologicai point of view in that it employs a waste product of a process which in turn used waste products at its starting point.

Accordingly from a first aspect the present invention consists in a method of manufacturing a combustible product from a plurality of separate components comprising, providing as one major component milled spent litter from the broiler industry, providing as a moisture absorbing main component a mixture of paper products and wood products, and passing the mixture of the milled spent litter and of the second component through a press so as to produce pellets or brickettes of the mixed component which form a combustible material, and wherein the percentage by weight of the milled spent litter is not greater than 70%, or less than 40%, of the weight of the final product, and wherein the percentage by weight of the components is selected so that the water content of the final product is not above 15% of the total weight thereof.

From a second aspect the invention consists in a combustible product manufactured by the above process.

From a third aspect the invention consists in a combustible product comprising a mixture of spent litter from the broiler which has been milled, industry, paper products and wood products, in which the proportion of paper and wood products is not less than 30% and not greater than 60% of the total weight of the product, in which the percentage by weight of water in the final product is not greater than 15%, and in which the final product includes a mould inhibitor.

Preferably the mould inhibitor is propionic acid.

In addition to the major components mentioned hereinbefore, the combustible material may include up to 10% by weight of secondary components. These secondary components may include straw, coal dust, peat or a thermoplastics material. Naturally coal dust like sawdust, as it is already in particulate form does not require milling or grinding before being mixed with the other components.

However secondary components in the form of straw, peat or thermoplastics will require milling.

In order that the present invention may be more readily understood, an embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a diagram showing the manufacture of pellets of combustible material in accordance with the present invention, and Figure 2 is a diagrammatic view of a pelleting mill.

Referring now to the drawings, Figure 1 shows diagrammatically an arrangement for manufacturing combustible pellets and comprises four hammer mills 1, 2, 3 and 4. Such mills are well known for grinding or milling foodstuffs and comprise a chamber, for example a substantially cylindrical chamber or hopper, into which the material to be milled is fed. The chamber contains motor driven bars, for example, of steel, which flail around in the chamber close to a screen the mesh size of which is chosen to suit application required. The hammer mill 1 is intended to handle spent broiler litter after it has been used in broiler houses. Such litter may initially have consisted of wood shavings or it may be litter of the type disclosed in British Patent Application No. 8026010.

The mesh openings in the screen of mill 1 preferably have a diameter of 3/16". Hammer mill 2 is for treating another main component in the form of paper products. By paper products it is intended to include ordinary paper and cardboard. It is also believed that waxed paper will be highly appropriate for use in the present invention as the wax component will increase volatility whilst it may also assist in the subsequent pelleting operation. Hammer mill 3 is for treating wood products such as wood shavings. If sawdust is to be a component of the final combustible product then this will not require milling and it is held in a hopper indicated at 5 for use as required. Hammer mill 4 is for milling secondary components such as straw, peat and thermoplastics materials which are to provide only a small part of the final combustible material.The screens of mills 2, 3 and 4 preferably have apertures of approximately 5/16" in diameter. A secondary component, coal dust, which does not require milling is housed in a hopper 1 6.

It will be appreciated that the spent litter has a relatively high water content. This water content could be reduced by heating but it is illogical to employ a heating step in the manufacture of a component which is itself to be used for heating. It will be appreciated that one of the advantages of the process described herein resides in the fact that the process does not include a heating step.

It is thus essential that the water content of the final product should be below a certain value in order to ensure effective combustion. It has been discovered that an upper limit for the water content is 1 5% by weight but that better results can be obtained if the water content is reduced to 12% by weight.

It is thus a purpose of adding additional components to the milled spent litter to reduce the water content of the final products to the required level.

The ability of the various non-litter components to reduce the final water level varies so that the amount of sawdust which has to be added to spent litter to achieve a suitable water level is greater than the weight of milled paper which has to be added to the same amount of spent litter to achieve the same result.

It will also be appreciated that the cost of the various components making up the final material will also vary.

Accordingly the contents of the mills 1, 2, 3 and 4 and hoppers 5 and 6 can be fed, possibly by suitable conveyor mechanisms, to weighing stations 7, 8, 9 and 10 from which metered amounts of the various components can be supplied to a pelleting machine 13 under the control of a control centre 11 including a computer.

Accordingly the computer at the control centre 11 is programmed so as to select appropriate ratios by weight of the components available so that the commercially most advantageous mixture can be arrived at. The pelleting machine also controls the supply to the pelleting machine 13 of additional chemical components such as propionic acid for inhibiting mould in the final product, aromatics so that the final product will burn with an attractive smell, and if the final product is for domestic use, colouring agents. At the same time a chemical for inhibiting the generation of ammonia may be added to the mixture prior to pelleting.

The pelleting machine 1 3 is shown in greater detail, though still diagrammatically, in Figure 2.

The machine 13 comprises an electric drive motor 20 which drives, through a suitable gearing 21, a pair of rollers which are driven around the inner circumference of a cylindrical dye 22. The mixture to be pelleted is introduced into the dye via a hopper 23 and is forced outwardly through dye openings 24 by the passage of the two rollers. The mixture is extruded through the dye openings. Revolving knives circulating around the circumference of the dye shear through the extruded material when it reaches a certain length and the sheared pellets fall into a hopper 25 from which they can be removed for packaging and use.

An important consideration is the length and nature of the dye openings in the dye 22. It has been found that these must not be tapered and should have a length of approximately 2". If the length of the dye openings is greater there is a tendency for the material to be compressed to such an extent that the heat so generated causes the material to lose its viscosity so that the press will tend to seize up.

The apparatus described above has several hammer mills which can be employed simultaneously.

However it is entirely possible to mix all the main components before milling and then to mill the mixture in a single mill before applying the milled mixture to the pelleting machine. However the arrangement described with regard to the drawings has the advantage of greater flexibility in that it is easier to control the flow and feed of milled components rather than the components prior to milling.

Typical ranges for combustible material according to the present invention are set out in the following table. The percentages are by weight.

Woodshavings/sawdust 20% - 20% Milled paper/cardboard - 20% 10% Milied paper/cardboard (waxed) 20% 30% 10% Milled straw - - 20% Broiler manure 60% 50% 40% 100 100 100 The above ranges are by way of example only.

Claims

1. A method of manufacturing a combustible product from a plurality of separate components comprising providing as one major component milled spent litter from the broiler industry, providing as a moisture absorbing main component a mixture of paper products and wood products, and passing the mixture of milled spent litter and of the moisture absorbing component through a press so as to form combustible pellets or brickettes of the mixed components, and wherein the percentage by weight of the milled spent litter is not greater than 70%, or less than 40% of the weight of the final product. and wherein the relative percentages of the component is selected so that the water content is not above 1 5% of the total weight thereof.

2. A method as claimed in claim 1, wherein the spent litter is milled in a hammer mill prior to being mixed with the moisture absorbing component.

3. A method as claimed in claim 2, wherein the hammer mill for milling the spent litter has a screen through which the milled litter passes having mesh openings with a diameter of approximately 3/1 6".

4. A method as claimed in any one of the preceding claims wherein at least a portion of the moisture absorbing component is milled in one or more hammer mill prior to being mixed with the milled spent litter.

5. A method as claimed in claim 4, wherein the or each hammer mill for milling the moisture absorbing component has a screen with mesh openings having a diameter of approximately 5/16".

6. A method as claimed in any one of the preceding claims wherein the mixture to be pelletted includes up to 10% by weight of a secondary component which is selected from, or a mixture of any two or more, of the following materials: coal dust, sawdust, straw, peat or thermoplastics.

7. A method as claimed in any one of the preceding claims including adding a mould inhibiting agent to the mixed components prior to pelletting.

8. A method as claimed in claim 7 wherein the inhibiting agent is propionic acid.

9. A method as claimed in any one of the preceding claims wherein pelleting the mixed components comprising extruding them through die openings having a length not greater than 2".

10. A method of manufacturing a combustible product substantially as herein before described with reference to the accompanying drawings.

11. A combustible product when manufactured by the method as claimed in any one of the preceding claims.

1 2. A combustible product comprising a mixture of spent litter from the broiler industry which has been milled, paper and/or wood products, in which the proportion of the paper and/or wood products is not less than 30% and not greater than 60% of the total weight of the product, in which the percentage by weight of water in the final product is not greater than 1 5%, and in which the final product includes a mould inhibitor.

1 3. A combustible product as claimed in claim 11, and including a secondary component which is not more than 10% by weight of the final product, the secondary component including one or more of the following materials: coal dust, sawdust, straw peat or thermoplastics.

14. A combustible product substantially as hereinbefore described in the foregoing specification.

1 5. Apparatus for manufacturing a combustible material substantially as hereinbefore described.

with reference to the accompanying drawings.