GB2396354A

GB2396354A - A method for manufacturing bulk products from waste material

Info

Publication number: GB2396354A
Application number: GB0229491A
Authority: GB
Inventors: Thomas Malcolm Kemp
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-12-18
Filing date: 2002-12-18
Publication date: 2004-06-23
Anticipated expiration: 2022-12-18
Also published as: GB0229491D0; GB2396354B

Abstract

A method for manufacturing bulk products from plastics material comprises the steps of conveying plastics particles (12) having a mean size no larger than 10mm in diameter to a vessel heated to soften the particles, tumbling the plastics particles in the heated vessel (14) while simultaneously feeding finely divided filler material (16) to the heated vessel to cause the filler to adhere to the plastics particles, separating and cooling a first portion of the plastics material and adhered filler (17), blending said cooled particles (19) with further heated plastics particles and said filler mixture (17), and shaping the blended material to form a product (24). Additional waste materials such as paper, wood-chip or sawdust may be added to the blend.

Description

! A METHOD FOR MANUFACTURING BULK PRODUCTS FROM WASTE

MATERIAL

The present invention relates to a method for manufacturing multi-purpose building and construction products from waste materials.

The legislation regarding the recycling of our waste is becoming more demanding than ever. Taxes have been introduced to assist in the costs related to the disposal of waste. These are seen to encourage the adoption of the means to increase recycling and to reduce the number of landfill sites required. Tax has been applied to the quarrying of aggregates, which has brought about the development of various types of "alternative aggregate".

This alternative aggregate is manufactured from waste material such as crushed concrete, ash, plastic, sand and glass.

Alternative aggregate produced by previous known methods is used as bulking agents for use within the manufacture of conventional concrete products and as an additive within conventional bituminous products and surfaces.

The major disadvantage of the previous recycling method is that the alternative aggregate produced could only ever be a partial resolution to the problems of waste. There is a problem with the co-adhesion of the concrete and the alternative aggregate, which can only be introduced into the manufacture of a concrete product or structural component in a low percentage to retain the required strength of the concrete.

Numerous methods for manufacturing building products from waste materials such as plastics are known. However, the currently used methods have limitations in relation to temperature, process speed and product size.

When indiscriminately assorted waste plastic is mixed at temperatures exceeding 200 C for any prolonged period, dangerous emissions occur, rendering the process environmentally unsuitable.

When indiscriminately assorted waste plastic is mixed at temperatures below 200 C, there are few emissions. However, it can take more than an hour to adequately blend one tonne of material before it can further be worked on by placing it into moulds and shaping it. Products manufactured by such methods are surface cooled by cold air or water thereby causing the surface to act as an insulation barrier that traps heat within the product. This, in most instances, causes indiscriminate degradation to the core of the product, commonly known as burn-out, and the larger the product, the greater the effect. It is not possible to align steel reinforcement centrally within a product that contains degradation (burnout) to its core, since the aggregate breaks down, loosening the reinforcement. Some processes retain products in moulds under pressure whilst the product cools, but this can be a lengthy process and requires large quantities of moulds.

The present method overcomes the problem of the previous methods by producing bulk structural, building and construction finished products completely or mostly from waste.

The present invention provides a method for manufacturing bulk products from plastics material comprising the steps of conveying plastics particles having a mean diameter no larger than 1 Omm to a vessel heated to soften the particles, tumbling said plastics particles in the heated vessel while simultaneously feeding finely divided filler material to the heated vessel to cause the filler to adhere to the plastics particles, separating and cooling a first portion of the plastics material and mixing it with more of said heated plastics particles and said filler mixture. The method has lower energy costs and requires little manpower compared to conventional methods. A typical plant can produce around 20 tonnes of finished product per hour, the product being up to 30% lighter than its concrete equivalent whilst maintaining the required structural integrity. The product can itself be recycled by being used as a second phase cooling and bulking agent in the method of the present invention.

The present invention incorporates a method whereby mixed waste plastic is processed at temperatures of 250 to 350 C without the occurrence of dangerous emissions because the plastic is in effect "flash-heated" and simultaneously fused with filler material such as sand/quarry-fines as it passes through the heated vessel. The fused particulates remain unconsolidated until they are conveyed into a blending vessel where previously prepared cooling/bulking material is added.

The present invention incorporates a method for cooling the product from within whereby degradation and burn-out do not occur. Therefore, products of a far greater size and structural integrity, compared to products made from known methods, can be produced with steel reinforcement and without lengthy cooling periods. The plastics particles and filler material are passed through the heated vessel by means of a calibrated rotation. Tumbling of the two materials occurs in the heated vessel, preferably at a temperature in the range of 250 to 350 C, and more preferably, at a temperature of about 300 C.

In one preferred embodiment of the invention, the blending of the cooled particles with the heated plastics material and filler mixture is carried out in a vessel containing a screw discharge. Once the materials have been blended it is then fed through an open mould configuration, made up of stainless steel plates which oscillate to form the desired shape of the end product. The product is then conveyed to a cutting bay where it is cut to the desired length.

The off-cuts from this process are fed to a granulator to reduce the mean diameter of the particles to no larger than 1 Omm. The plastics particles are then returned to the start of the process as integral cooling and bulking agents, thus rendering the method efficient as no waste is produced.

In an alternative embodiment of the present invention, additional bulking agents incorporated into the blend used in the process are comprised of waste materials such as paper, wood chip and ash.

In a further embodiment of the present invention, reinforcing means are added to the bulk product. Glass fibre is added to the blending process of cooling and bulking to reinforce the product, whilst steel is included in the product by means of an apparatus that feeds the reinforcing steel through a manifold together with the blended mixture.

Specific embodiments of the method of the present invention, will now be described further, with reference to the accompanying drawing which illustrates schematically a production plant for performing the claimed method.

Referring to the drawing, mixed waste plastic 12 of any grade is received from a waste stream in bulk. It is then reduced in size to particles having a mean diameter no larger than 1 Omm. The resultant plastic particles are conveyed to a heated vessel 14 where they are passed through the heated vessel by means of a calibrated rotation at temperatures of between 250 and 350 C, preferably at 300 C, at a rate of 6 tonnes per hour.

Simultaneously, waste material known as quarry fines 16, which are a by-

product of aggregate, is conveyed to and passed through the heated vessel 14 by means of a calibrated rotation at a desired rate. As the combined particles pass through the heated vessel 14, they become fused together. For the first phase of the process, the fused material 17 is immediately conveyed through a water trough 18 for 1 hour in order to cool it completely. This provides material 19 for use in the second phase of the process.

For the second phase of the process, the mixed plastic waste particles 12 and the quarry fines 16 are fused together whilst continuously passing through the heated vessel 14 at temperatures between 250 and 350 C, preferably at 300 C and at a combined rate of 20 tonnes per hour. The mixture 17 is then charged to a blending vessel 20 containing a screw discharge.

The cooled material produced during the first hour of the process is simultaneously fed to the blender 20 at a rate of about 2 tonnes per hour.

The screw within the blender continuously discharges the combined material where it then passes through an open mould configuration 22 made up of stainless steel plates that oscillate to form the desired shape of the end product 24. The cold material that has been blended with the fused material 17 absorbs the heat which would otherwise become trapped within the product as the surface cools, which allows the product to retain its density and stability without degradation. The product 24 is then conveyed to a cutting bay 26 where it is cut to the desired length. The off-cuts 28 are fed into a granulator 30 to reduce the particle size and then returned to the process as integral cooling and bulking agents as described in the second phase.

The present invention includes a method for incorporating reinforcing means to all products produced that may require it. The reinforcing means can be of steel or any other additive such as glass fibre. If steel reinforcement is required, it is incorporated into the product by means of an apparatus that feeds the reinforcing steel through a manifold together with the blended mix. If glass fibre is preferred, it would be added to the blending process of cooling and bulking as described within the second phase operation.

The present invention includes a method for incorporating additional cooling and bulking agents such a paper, wood-chip, sawdust and other forms of waste including ash.

The products to be made by the method of the invention include sectional pile foundations, beams and floor panels.

! In the preferred embodiment of the method of invention, the preferred temperature of the heated vessel is gauged by the throughput tonnage per hour of plastic flakes and quarry fines. The greater the throughput, the higher the temperature. For example, if the tonnage is 20 tonnes per hour, the preferred temperature of the heated vessel is 300 C, whereas if the throughput is 10 tonnes per hour, the preferred temperature of the vessel is 250 C.

Claims

1. A method for manufacturing bulk products from plastics material comprising the steps of: a) conveying plastics particles having a mean size no larger than 10 mm in diameter to a vessel heated to soften the particles, b) tumbling said plastics particles in the heated vessel while simultaneously feeding finely divided filler material to the heated vessel to cause the filler to adhere to the plastics particles, c) separating and cooling a first portion of the plastics material and adhered filler, d) blending said cooled particles with further said heated plastics particles and said filler mixture, and e) shaping the blended material to form a product.

2. A method according to claim 1 wherein said plastics particles and filler material are passed through said heated vessel by means of a calibrated rotation.

3. A method according to claim 1 or claim 2 wherein the temperature of the heated vessel is between 250 and 350 C.

4. A method according to claim 3 wherein the temperature of the heated vessel is about 300 C.

5. A method according to any preceding claim wherein the blending step (d) is carried out in a vessel containing a screw discharge.

6. A method according to any preceding claim wherein the blended material is fed through an open mould configuration.

7. A method according to claim 6 wherein the open mould configuration is made up of stainless steel plates which oscillate to form the desired shape of the end product.

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8. A method according to claim 7 wherein the product is conveyed to a cuffing bay and product is cut to the desired length in said cutting bay.

9. A method according to claim 8 wherein off-cuts of the product are fed to a granulator and then returned to the process as integral cooling and bulking agents.

10. A method according to any preceding claim wherein additional bulking agents comprised of waste materials such as paper, wood chip and ash are incorporated into the blend.

11. A method according to any preceding claim wherein reinforcing means are added to the bulk product.

12. A method according to claim 11 wherein glass fibre is added to the blending process of cooling and bulking to reinforce the product.

13. A method according to claim 11 wherein steel is included into the product by means of an apparatus that feeds the reinforcing steel through a manifold together with the blended mixture.

14. A method for manufacturing bulk products from waste plastics material, substantially as herein described with reference to the accompanying drawing.