AU643815B2

AU643815B2 - Process and apparatus for the production of paper products

Info

Publication number: AU643815B2
Application number: AU82037/91A
Authority: AU
Inventors: Peter John Mitchell Farley; Donald Barry Webb
Original assignee: FibreCycle Pty Ltd
Current assignee: FibreCycle Pty Ltd
Priority date: 1990-07-18
Filing date: 1991-07-11
Publication date: 1993-11-25
Anticipated expiration: 2011-07-11
Also published as: AU8203791A

Description

PROCESS AND APPARATUS FOR THE PRODUCTION OF PAPER PRODUCTS

Technical Field

This invention relates to a process and apparatus for the production of paper products, such as moisture absorbing products or a combustible paper fuel.

In the case of a moisture absorbing product, such may be capable of absorbing liquids without losing its shape, and in particular, but not exclusively, such a product in a pelletised form. One embodiment of the invention has been ^Particularly developed for use as "cat litter" although x nay be used for other purposes where its moisture absorbing properties are required. Background Art

The majority of products presently available for use as "cat litter" or for other moisture (liquid) absorbing purposes, are formed from clay based materials and are non-organic with the resulting problem that they will not decompose. - In addition they have the added disadvantage of depositing clay powder on the paws of cats which is subsequently transferred to floor surfaces leaving tracks. In addition such products result in the continued use of mineral resources whilst more recently certain cultivated pasture crops have been unnecessarily harvested and used merely for the purposes of "cat litter".

In the case of paper fuel it may be composed of a relatively high percentage of paper. Whilst paper combusts readily it can not be used in its basic form as it either burns too quickly in its loose sheet form or will not burn satisfactory when in the form of a thick mass. In addition, it is important to consider the physical transportation of recyclable paper in its normal form from collection zones to points of use for heating and/or cooking.

As a result of a heightening of community awareness, the supply of paper for recycling has increased to such a degree that it, in many cases, far exceeds the demand for conventional products made from such recycled paper, and as a result the excess is disposed of by landfilling or exported usually at the cost of the country. Disclosure of the Invention

It is therefore one object of the present invention to utilize surplus recycled non-toxic paper in a form convenient for moisture absorbing purposes, such as "cat litter" and which is also convenient for the purposes of ease and cleanliness of handling, packaging and storage.

It is also an object of the present invention to utilise surplus recycled non-toxic paper in a form convenient and effective for domestic, commercial and industrial heating and/or cooking, and which also provides for ease and cleanliness of handling, packaging and storage.

The invention envisages a process for producing a paper product of the type defined above, including the steps of reducing paper to particulate form, mixing the particles of paper with water, subjecting the mix to pressure to form a compacted mass which is subsequently subjected to dehydration to reduce the moisture content.

Preferably the paper is reduced to a particulate form by grinding.

The invention also envisages an apparatus for carrying out the process defined above.

The invention still further envisages a paper product resulting from the process and apparatus defined above. Brief Description of the Drawings

In one embodiment of the invention the process and apparatus produces a paper product for use as a moisture absorbing medium.

In another embodiment the process and apparatus produces a combustible fuel formed primarily from particles of compressed paper combined at least with coal dust.

Preferably, in the case of a combustible fuel, a proportion of calcium oxide is also added to the mix.

One preferred embodiment of the process and apparatus of the invention will now be described with reference to the accompanying drawings, in which;

Figure 1 is a flow diagram showing a process for producing a paper product which may be a moisture absorbing paper product or a paper fuel.

Figure 2 is a side elevational view of part of an apparatus for carrying out the process of the invention, and

Figure 3 is a plan view of the part of the apparatus of Figure 2. Best Mode for Carrying out the Invention

In this preferred embodiment of the invention, as applied to producing a moisture absorbing product, the recycled paper used is primarily newsprint which is ground in available paper grinding equipment down to a paper fluff suitable for subsequent compression and binding. Water is then added to the paper fluff to achieve an overall water content of between 25 - 30%.

The mixture of paper and water is then extruded under high pressure, thought to be in excess of 2,000MPa, and then divided into moisture absorbing pellets having a surface area of between 110 mm² and 210 mm² and a length of between 5 mm and 15 mm.

The pellets are then finally dehydrated by a drying process to reduce their moisture content to something less than 10%.

The resultant pellets are capable of absorbing in excess of twice their own weight of water without substantially changing their shape and are also substantially free of paper dust. After use, for example as "cat litter", the pellets can be readily disposed of by digging into soil as an organic, decomposable, non-toxic soil conditioner, or flushed into sewerage systems.

Other suitable uses of the pellets is as water retention masses and soil conditioners to aid the cultivation of plants.

As applied to paper fuel the particle size produced from the grinding operation should be such as to range from paper fluff to particles having a surface area up to 5 cm² whilst the fluff should not be less than 30% of the total paper mix.

The ground paper is then mixed with coal dust, calcium oxide and water. The coal dust can be a by-product of the manufacturer of briquettes, and may range in particle size up to 1.5 mm in diameter and blended with the ground paper in the ratio between 2:1 and 4:1 paper to coal dust. The calcium oxide component should be 1 part per 100 of the paper and coal mix and sufficient water added to result in a moisture content for the mix of between 25 to 30%.

The above mixture is then extruded under high pressure, thought to be in excess of 2,000MPa, and divided into units of fuel having a surface area between 60 cm² and 100 cm², with a length between 3 cm and 6 cm and a mass in excess of 1.00 g s per cm³ of dry weight.

The extruded units are then finally dehydrated by a drying process to reduce the moisture content of the units for something less than 13.5%.

The resultant combustible fuel is in effect clean, readily packaged units suitable for domestic, commercial and/or industrial purposes, such as for heating, and the blend of the mixture and the degree of compression is such as to have an overall energy value of 15 MJ/kg.

With reference to Figure 1 of the drawings, and in accordance with this preferred embodiment of the invention, the process as applied to the production of a moisture absorbing paper product, or a predominantly paper based combustible fuel, involves taking raw material (waste paper) from a storage 10, passing it through a preliminary sizing process 11 to reduce the waste paper to a manageable size for subsequent grinding in a grinding plant 12 to paper fluff. The paper fluff is subsequently aspirated at station 13, whereafter the fluff is settled at 14 and subsequently conditioned by application of water at 15. The conditioned paper product is then transferred to extruding equipment 16 where it is extruded in a pellet mill 16 into a continuous length and cut to individual pellet lengths, before being dryed in a dryer 17. The process is completed by a sizing operation at station 18 to remove undersized and oversized pellets (including dust particles), for subsequent transfer to a finished product despatch station 19.

Figures 2 and 3 of the drawings show the part of the apparatus for carrying out the aspiration, settling and conditioning steps of the process, and comprises a storage bin 20 from which ground paper gravitates as a layer onto the upper run of a first stage conveyor belt 21 driven to run at a speed of in the order of 1 metre per second and then beneath a first pivoted leveling and pressurising roller 22 which serves to compact the layer of ground paper on the conveyor belt 21 to a thickness of between 10 to 20 mm. Because of the pivoted support for the leveling and pressurising roller 22, it is free floating to ride over larger objects or masses of material. The compacted paper fluff is then passed on the conveyor belt 21 beneath a first flow sensor 23, in the form of a micro-switch, which confirms that there is a layer oi material on the conveyor belt 21.

The material on the first stage conveyor belt 21 then passes beneath a first set of spraying jets 24, supplied with water through a supply conduit 25, and only operable if the first flow sensor 23 has detected the presence of material on the conveyor. The moistened (conditioned) material on the conveyor belt then moves beneath a second flow sensor 26 which confirms that there is still a layer of material on the conveyor belt 21, and then gravitates through a rearwardly inclined transfer chute 27 to a second stage conveyor belt 21' and in the process the material is inverted to expose the opposite side of the material to firstly a second free floating pivoted leveling and pressurising roller 28 and thereafter a second set of spraying jets 29, also supplied with water through a supply conduit 30, and the aspirated, settled and conditioned mass of paper fluff is then transferred to the extruder where it is extruded and cut to the required pellet size, before drying and sizing.

In the case of paper fuel, the ground paper, before being supplied to the storage bin 20, is mixed with a proportion of coal dust and a proportion of calcium oxide, and the mixture is thereafter subjected to aspiration, settling and conditioning in the apparatus shown in Figures 2 and 3.

Modulator valves (not shown) control the volume of water sprayed onto the material by the spraying jets 24 and 29 above both the first and second stage conveyor belts 21 and 27, and the volume of the sprays is controlled to be dependent on the speed of the respective conveyor belts.

As shown in the drawings, each of the conveyor belts 21 and 27 have a plurality of spaced apart cleats 31 extending transversely of their length which serve to not only assist in conveying the material, but also to control the thickness of material between the preferred limits of 10 to 20 mm.

In relation particularly to a moisture absorbing paper product, the process of this preferred embodiment of the invention can achieve bulk densities of product up to 660 kg/m³ with a relatively slow throughput, and less friable for use as a "cat litter" for example, whilst in relation to a low density product capable of rapidly absorbing floor spills, such as oils, bulk density of between 300 to 500 kg/m³ are desirable.

Claims

1. A process for producing a paper product, including the steps of reducing paper to a particulate form, mixing the particles of paper with water, subjecting the mix to pressure to form a compacted mass which is subsequently subjected to dehydration to reduce the moisture content.

2. A process as claimed in Claim 1, wherein the water is added to the particles of paper as they move as a layer of material o: a first conveyor, and also whilst moving on a second conveyor after being transferred thereto in a manner which involves inversion of the layer.

3. A process as claimed in Claim 1 or 2, wherein the paper is reduced to particulate form by grinding to produce particles in the form of paper fluff.

4. An apparatus for producing paper product, including means to reduce paper to a particulate form, means for mixing the particles of paper with water, means to apply pressure to the mix to form a compacted mass, and means to dehydrate the compacted mass.

5. An apparatus as claimed in Claim 4, wherein the means to reduce the paper to particulate form includes a grinding means to produce particles in the form of paper fluff.

6. An apparatus as claimed in Claim 5, wherein the means to reduce the paper to particulate form also includes means to shred the paper prior to grinding.

7. An apparatus as claimed in any one of Claims 4 to 6, wherein the means to add water to the particles of paper includes a first and a second conveyor, along which the paper particles move as a layer with the layer being discharged from the leading end of the first conveyor onto the trailing end of the second conveyor in a manner which results of inversion of the layer, and spraying means to, whilst said layer is on said conveyors, subject the layer to controlled sprays of water.

8. An apparatus as claimed in Claim 7, wherein rollers are disposed above each of said conveyors to level and compact said layer.

9. An apparatus as claimed in Claim 7 or 8, wherein sensors are disposed above said first conveyor to sense the presence of a layer thereon and actuate said spraying means accordingly.

10. A paper product manufactured in accordance with the process of Claims 1 to 3, using an apparatus in accordance with Claims 4 to 9.