AU2021107186A4

AU2021107186A4 - Conveying Granular Glass

Info

Publication number: AU2021107186A4
Application number: AU2021107186A
Authority: AU
Inventors: Alan Travers; Kenneth Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-08-25
Filing date: 2021-08-25
Publication date: 2021-12-09
Anticipated expiration: 2029-08-25

Abstract

The present invention relates to methods for conveying a granular glass material using a belt conveyor and/or screw conveyor, especially in the field of concrete manufactured 5 articles, and especially polymer concrete manufactured articles.

Description

AUSTRALIA Patents Act 1990

COMPLETE SPECIFICATION INNOVATION PATENT

Invention Title: Conveying Granular Glass

The following statement is a full description of this invention, including the best method of performing it known to us:

Conveying Granular Glass

Field of the Invention

The present invention relates to methods for conveying a granular glass material using a belt conveyor and/or screw conveyor, especially in the field of concrete manufactured articles, and especially polymer concrete manufactured articles.

Background of the Invention

Glass materials, especially recycled glass material, are becoming more available. For example, there is an increased societal focus on glass recycling. Many municipalities now provide a dedicated industrial and household glass recycling scheme. As a result, there is a need for means of appropriate disposal of glass materials.

One means for using glass materials lies in the field of concrete manufactured articles. A multitude of concrete articles are manufactured and used daily in many different fields of endeavour, including most significantly the building and construction industry. Concrete is traditionally composed of a mixture of granular materials being natural aggregates, primarily sand (quartz), and natural Portland cement. Manufacture of concrete articles typically involves moving bulk quantities of these raw ingredients by belt and screw conveyors to concrete plant manufacturing machinery, e.g. mixers.

A belt conveyer is an apparatus of machinery which includes a conveyor belt wrapped in a closed loop about, and forming an elongate linear top-side carrying surface between, a tail and a header pulley, at least one of which is turned by an electric motor to rotate the conveyor belt through its loop in tail to header direction (i.e. in operation). The underside of the carrying surface is generally supported between the tail and header pulleys by one or more rollers and/or platforms. Additional take-up pulleys may also be used within the loop. A material loaded to the carrying surface in the region of the tail pulley is thus conveyed in apportioned amounts towards the header pulley and deposited off the end where the conveyor belt wraps about the header pulley. Often, the carrying surface is inclined to convey material to a deposit point which is higher than the load point. For conveying granular materials, the conveyor belt may also include a series of evenly-spaced cleats which extend from the conveyor belt surface and assist to pick up the material.

A screw conveyor is an apparatus of machinery used primarily for conveying granular materials, which includes an elongate barrel of fixed inner diameter within which is axially disposed a helical screw having helix blades (flights) and often a core. The flights define an outer diameter of the helix screw. The granular material is loaded to the barrel about the base end of the helix screw, which is turned by an electric (or other type of) motor (i.e. in operation) to convey the material along the barrel in apportioned amounts by the rotating flights, and deposited from an outlet towards the other end of the helix screw.

Recently, the present inventors have found that various concrete articles in building and construction can be made using glass aggregate in which some of the natural sand aggregate is replaced with granular glass. See for example Applicant's patent application No. 2021103675 "Building Element" and No. 2020901863 "Traffic management device".

With the availability of glass materials and uses found in manufacturing concrete articles, there is a need for suitable conveying methods and machinery to enable conveying of glass materials, especially for manufacturing concrete articles.

There exists a need to overcome, or at least alleviate, one or more of the difficulties or deficiencies associated with the prior art.

Summary of the Invention

In one aspect, the present invention provides a method for conveying a granular glass material, including one or both of: (a) loading granular glass material to a conveyor belt of an operating belt conveyor, said belt conveyor being suitable for conveying a natural sand aggregate when loaded to the conveyor belt using a loading chute with an opening area, wherein the granular glass material is loaded using a loading chute with an opening area that is reduced as compared to the opening area for conveying a natural sand aggregate; and (b) loading granular glass material to a barrel of an operating screw conveyor, said screw conveyor being suitable for conveying a natural sand aggregate using a helical screw with a maximum outer diameter; wherein the barrel contains a helical screw having a maximum outer diameter that is reduced as compared to the maximum outer diameter of the screw for conveying a natural sand aggregate.

In many existing plants which manufacture concrete articles, belt and screw conveyers operate to convey natural sand aggregate to downstream manufacturing machinery.

In the case of a belt conveyor, bulk natural sand aggregate is generally loaded in large quantities to a feeding hopper which loads the material to the conveyor belt carrying surface via a loading chute which has an opening area, under gravity. The opening area may serve a metering function, in that is of a size such that, in operation within the operating parameters of the belt conveyer (e.g. capacity, speed, incline angle etc., which are usually determined by the material delivery requirements of downstream processes), the natural sand aggregate is loaded in a stream of material, or a consistent cleat (if present) pick-up volume, covering the width of the carrying surface. The carrying surface is often the entire width, or mostly the entire width, of the conveyer belt. If the opening area is too great (again, within the operating parameters of the belt conveyer) then to much material may be loaded to the carrying surface and result in overloading of the belt conveyor - whether by exceeding the carrying capacity of the belt conveyer or delivering too much material too quickly to downstream manufacturing machinery - and/or loss of substantial amounts of material over the sides. Accordingly, the chute opening area is generally intended to provide a suitable metering of the loaded material. For natural sand aggregate, this may be achieved using a chute opening area corresponding to about a width by width dimension of the conveyor belt carrying surface, or at least a width by three-quarter width of the conveyor belt carrying surface. For example, for a 200 mm conveyor belt, the opening area may be about 200 mm by 200 mm (i.e. 400 cm 2 ) or at least 200 mm by 150 mm (i.e. 300cm 2).

Accordingly, by the belt conveyor being suitable for conveying a natural sand aggregate when loaded to the conveyor belt using a loading chute with an opening area, is meant that the opening area is such that an amount of material loaded to the carrying surface of the conveyor belt is such that the belt conveyor is capable of conveying the natural sand aggregate, within the operating parameters of the belt conveyer, without overloading the belt conveyer, and/or without substantial loss of material from the conveyer belt.

In the case of a screw conveyor (taken to include both augering and metering screw conveyors), bulk natural sand aggregate is generally loaded in large quantities to a feeding hopper which loads the material to the barrel of the screw conveyer via a loading chute, under gravity. The turning helical screw draws sand along the barrel to a deposit outlet, and in doing so may serve a metering function such that, in operation within the operating parameters of the screw conveyer (e.g. capacity, speed, incline angle etc., which are again usually determined by the material delivery requirements of downstream processes), the natural sand aggregate is deposited from the screw conveyer in a stream of material. The barrel usually has a fixed and constant inner diameter (ID), while the helical screw may have flights of varying outer diameter including a maximum outer diameter (OD). As the helical screw rotates within the barrel, the OD is generally smaller than the ID, leaving a space, or offset, there between (i.e. (ID-OD)/2 = offset). If the OD is too large, and the offset too small, then the natural sand aggregate may become trapped between the flights and the barrel causing the screw jam and become damaged and/or to wear excessively. Accordingly, the OD of the helical screw is intended to provide a functional conveyance of the loaded material. For natural sand aggregate, this may be achieved using an OD which leaves an offset that is at least twice the maximum particle size.

Accordingly, by the screw conveyor being suitable for conveying a natural sand aggregate using a helical screw with a maximum outer diameter, is meant that the maximum outer diameter is such that the screw conveyor is capable of conveying the natural sand aggregate, within the operating parameters of the screw conveyer, without jamming and/or wearing excessively.

By a natural sand aggregate is meant a natural sand (soil) with a particle size of no larger than that which defines it as sand or fine gravel according to ISO 14688-1:2002. For example, coarse sand has a particle size distribution of between 0.62 mm and 2.0 mm, medium sand has a particle size distribution of between 0.2 mm and 0.63 mm, and fine sand has a with a particle size distribution of between 0.063 mm and 0.2 mm. For completeness, coarse, medium and fine silt together occupies the particle size range from 0.002 mm to 0.063 mm.

In preferred embodiments, the natural sand aggregate for which the belt conveyor and screw conveyor are suitable for conveying is coarse sand.

This being a comparator, the method of the present invention is directed towards conveying a granular glass material. The present inventors have found that belt and screw conveyers suitable for conveying natural sand aggregates are not suitable, or at least not efficiently used, for conveying granular glass materials. The belt conveyor tends to lose substantial amounts of ground glass off the sides and/or become overloaded. The screw conveyer tends to grind the glass and jam and/or excessively wear the helical screw. Without wishing to be limited by theory, it is thought that these tendencies are caused by one or more factors, being that: granular glass generally has a higher flowability, a larger maximum particle size, and a wider particle size distribution; and granular glass tends not to have a spherical particle shape, as compared to natural sand aggregate.

Accordingly, the granular glass material (also called ground, crushed, crunched, rolled or particulate glass, or glass cullet) may be thought of as a material (including a mixture) containing granular glass in a proportion that increases one or more of the flowability, maximum particle size, particle size distribution and particle shape irregularity of the material as compared with natural sand aggregate. Generally speaking, the granular glass material may comprise at least approximately 80%, preferably 90%, more preferably at least approximately 95%, w/w granular glass. In preferred embodiments, the granular glass material consists essentially of granular glass, in that it is composed mostly entirely of granular glass on a w/w basis, for example at least approximately 98% and more preferably at least approximately 99% granular glass including essentially 100% ground glass.

Preferably, the granular glass to which the method is applied includes, or is wholly (consists essentially of), recycled glass. The use of recycled glass is preferred because it provides a useful application for recycled glass materials, and confers the associated reduced cost and environmental impact.

The present invention is defined by, in the case of a belt conveyer, loading with a reduced chute opening area for a granular glass material as compared to that for natural sand aggregate. In traditional practices the opening area of a loading chute for loading a material to a belt conveyor may increase as the particle size of the material increases. However, the present inventors have found that reducing the opening area additionally meters the loading of the granular glass (within the operating parameters of the belt conveyer) and accounts for the putative increased flowability of the material, surprisingly without causing the chute to become clogged despite the larger particles size, and significantly reducing incidents of loss of material over the side of the conveyor belt and overloading.

The opening area of the loading chute may be reduced to less than a width by width dimension of the conveyor belt carrying surface as may be used for natural sand aggregate. Whatever the case, in preferred embodiments, the opening area of the loading chute is reduced by about 10% to about 60%, preferably by about 20% to about 50%, and more preferably by about 30% to about 40%, as compared to the opening area for natural sand aggregate.

In preferred embodiments, the reduced loading opening area is directed to load the granular glass material onto the width-wise centre of the conveyor belt carrying surface. This may further assist to achieve an even stream of material on the conveyor belt and reduce loss of material over the sides.

The opening area may be reduced by any suitable means. In preferred embodiments, the opening area is suitably reduced by adding a blocking member such as a steel plate to the inside of the chute.

In the case of a screw conveyer, the present invention is defined by a reduced helical screw OD as compared to that for natural sand aggregate. The present inventors have found that reducing the OD (within the operating parameters of the belt conveyer) accounts for the putative increased maximum particle size and widened particle size distribution of granular glass materials, significantly reducing incidents of jamming and excessive wearing. The present inventors have also found that, as compared to natural sand aggregate, granular glass may be effectively conveyed using an OD which leaves an offset that is less than twice the maximum particle size of the granular glass material.

Accordingly, in a preferred embodiment, the OD is reduced by an amount which provides an offset that is less than twice the maximum particle size, and preferably which provides an offset of about 1.5 to about 1.9.

As many existing plants are equipped with belt and screw conveyers which operate to convey natural sand aggregate, the present invention is intended to provide a means for using existing equipment with a granular glass material. However, the same principles of the invention apply to new dedicated-glass equipment, which if turned over to conveying natural sand aggregate would tend to utilise a belt conveyer with a chute opening area greater than that used for granular glass and/or a screw conveyer with a helical screw OD larger than that used for granular glass.

The method for conveying a granular glass material may be used in any process in which granular glass is required to be conveyed, for example in a process of manufacturing the granular glass material itself, or in a process of using it to make manufactured articles. In preferred embodiments, the method for conveying a granular glass material is used in a process of making glass aggregate concrete articles, preferably glass aggregate polymer concrete articles, for example in conveying it within a manufacturing plant from cargo to downstream manufacturing equipment.

Accordingly, in another aspect, the present invention provides a glass aggregate concrete article, preferably a glass aggregate polymer concrete article, manufactured using a method as herein described.

By "glass aggregate concrete" is meant a concrete material containing granular glass as aggregate. In other words, generally speaking a glass aggregate concrete as compared to traditional concrete is a concrete in which granular glass replaces at least a portion of natural sands as aggregate. A polymer concrete is a material comprising aggregate bound with a polymer. In other words, generally speaking a polymer concrete as compared to traditional concrete is a concrete in which a polymer substantially replaces natural lime-type cements (Portland cement) as a binder. Accordingly, by "glass aggregate polymer concrete" is meant a polymer concrete containing granular glass as aggregate. In other words, generally speaking a glass aggregate polymer concrete is a polymer concrete in which granular glass replaces natural sands as aggregate.

The glass aggregate polymer concrete article may be of any suitable type to which concrete or concrete-like materials are applicable. Examples include the building elements as described in the specification for patent application No. 2021103675, the traffic management devices as described in the specification for patent application No. 2020901863, drainage channels, pipes, slabs, and the like. The specification for patent application Nos. 2021103675 and 2020901863 are hereby incorporated by reference in their entirety.

The use of glass aggregate polymer concrete is advantageous, as it reduces the use of natural cement materials and the associated environmental impact. Polymer concrete is also generally stronger than traditional concrete; for example less prone to chipping and fracture.

In this specification, the term 'comprises' and its variants are not intended to exclude the presence of other integers, components or steps.

In this specification, reference to any prior art in the specification is not and should not be taken as an acknowledgement or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably expected to be combined by a person skilled in the art.

The present invention will now be more fully described with reference to the accompanying Examples and drawings. It should be understood, however, that the description following is illustrative only and should not be taken in any way as a restriction on the generality of the invention described above.

Detailed Description of the Embodiments

A belt conveyer with 200 mm wide conveyor belt and 25 mm cleats and including a hopper having a chute opening area of about 200 mm by 150 mm (i.e. about 300cm 2 ) is routinely operable, with a belt speed of about 115 metres per minute at an incline angle is approximately 450, to convey coarse sand from the chute to a deposit point off the end of the conveyor belt.

When turned over to ground glass aggregate fed from the chute having the same opening area and the same operating parameters, the same belt conveyor became overloaded resulting in the belt conveyor pulleys slipping and damaging the conveyor belt. Significant amount of ground glass aggregate was also lost over the sides of the conveyor belt.

A steel plate was added to the chute to reduce its opening are to about 180 cm 2

corresponding to a 40% reduction in the opening area. This resulted in the same belt conveyor being operable with the same operating parameters to convey ground glass from the chute to a deposit point off the end of the conveyor belt, without becoming overloaded or losing significant amounts of material over the sides.

A screw conveyor with a barrel having a 75 mm ID and a helical screw with an OD of 67 mm (i.e. 4 mm offset) is routinely operable, with a screw speed of about 80 RPM at an incline angle is approximately 450, to convey coarse sand having a maximum particle size of 2.0 mm (i.e. an offset of twice the maximum particle size).

The screw conveyor was turned over to two samples of ground glass, one having a maximum particle size of about 4.75 mm and another having a maximum particle size of about 8.0 mm. Using the same operating parameters, the same screw conveyor was worn excessively and tended to become jammed with both of these samples.

For the 4.75 mm sample, the helical screw was replaced with a helical screw with an OD of 57 mm, corresponding to an offset of 9 mm (i.e. an offset of 1.89 times the maximum particle size). For the 8.0 mm sample, the helical screw was replaced with a helical screw with an OD of 50 mm, corresponding to an offset of 12.5 mm (i.e. an offset of 1.56 times the maximum particle size)

This resulted in the same screw conveyor being operable with the same operating parameters to convey both samples of ground glass from the chute to a deposit point, without excessive wear to the screw or becoming jammed.

Finally, it is to be understood that various alterations, modifications and/or additions may be made without departing from the spirit of the present invention as outlined herein.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for conveying a granular glass material, including one or both of: a. loading granular glass material to a conveyor belt of an operating belt conveyor, said belt conveyor being suitable for conveying a natural sand aggregate when loaded to the conveyor belt using a loading chute with an opening area, wherein the granular glass material is loaded using a loading chute with an opening area that is reduced as compared to the opening area for conveying a natural sand aggregate; and b. loading granular glass material to a barrel of an operating screw conveyor, said screw conveyor being suitable for conveying a natural sand aggregate using a helical screw with a maximum outer diameter (OD); wherein the barrel contains a helical screw having an OD that is reduced as compared to the OD of the screw for conveying a natural sand aggregate.

2. A method for conveying a granular glass material according to claim 1, wherein the natural sand aggregate is coarse sand.

3. A method for conveying a granular glass material according to claim 1 or 2, wherein the granular glass material consists essentially of granular glass.

4. A method for conveying a granular glass material according to any one of claims 1 to 3, wherein the granular glass material consists essentially of recycled glass.

5. A method for conveying a granular glass material according to any one of claims 1 to 4, wherein the opening area of the loading chute is reduced by about 10% to about 60%.

6. A method for conveying a granular glass material according to any one of claims 1 to 5, wherein the reduced loading opening area is directed to load the granular glass material onto a width-wise centre of the conveyor belt.

7. A method for conveying a granular glass material according to any one of claims 1 to 6, wherein the opening area is reduced by adding a blocking member.

8. A method for conveying a granular glass material according to any one of claims 1 to 7, wherein the OD is reduced by an amount which provides an offset that is less than twice the maximum particle size of the granular glass material.

9. A method for conveying a granular glass material according to any one of claims 1 to 8, wherein the OD is reduced by an amount which provides an offset that is about 1.5 to 1.9 times the maximum particle size of the granular glass material.

10. A glass aggregate concrete article, manufactured using a method according to any one of claims 1 to 9.