GB2186285A

GB2186285A - Bitumen or tarmacadam/aggregate recovery

Info

Publication number: GB2186285A
Application number: GB08603425A
Authority: GB
Inventors: Peter Michael Robinson
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-02-12
Filing date: 1986-02-12
Publication date: 1987-08-12
Also published as: WO1987005042A1; AU7025287A; GB8603425D0

Abstract

A separator for bitumen and aggregate or tarmacadam and aggregate compositions comprises a container (1) for receiving the composition, means (5) for loading the container with the composition, inlet means (4) for receiving the composition and for receiving solvent to dissolve the bitumen or tarmacadam portion, the container being rotatable and having outlet means (4) for extracting bitumen or tarmacadam and solvent mixture and air inlet means (9) leading into the container. Extraction means are provided for extracting a solvent and air mixture and aggregate outlet means are provided for removing dried aggregate from the container to means for grading removed aggregate. A method of separating bitumen or tarmacadam and/or aggregate components from a composition comprising them is also disclosed based on use of such a container. The invention has principal application in the recovery of these components from particularly used pedestrian or vehicular surfaces for subsequent re-use.

Description

SPECIFICATION Bitumen/aggregate recovery This invention concerns separation and subsequent reuse of bitumen and aggregate components from composite material, such as ashphalt or tarmac, comprising them. It is more particularly concerned with recovery of bitumen and aggregate from used pedestrian or vehicular surfaces and their subsequent reuse in, for example, construction or repair of similar or different surfaces.

The invention may find application in construction or repair of pedestrian surfaces such as paving or vehicular surfaces such as roads.

Recovered bitumen may be used in ashphalt/ tarmac surfaces and recovered aggregate may be used not only in these surfaces but also, for example, in concrete surfaces.

Because fresh bitumen is expensive and supplies may be restricted in the future as it is an oil-derived product, it is desirable to recycle it. Supplies of aggregate are also finite and require costly extraction methods as well as leaving unattractive excavation sites.

It is known to add some old bitumen/aggregate composition to fresh materials and re-mix them to meet current required specifications, i.e. the appropriate British Standard in force.

This is urisatisfactory for a number of reasons. Specifications for bituminous-based surfaces change over a number of years and recovered material does not always fulfil the requirements of current specifications. Existing bituminous/aggregate compositions such as ashphalt or tarmac surfaces can through use become oxidised and contaminated with, e.g.

oil drippings and rubber deposits and the like, and the inclusion of these components with fresh aggregates raises doubt as to long term performance. In particular, oxidised bitumen can lose flexibility and weight-bearing performance.

In consequence, complete recycling of bitumen and aggregate has not been feasible. Bitumen aggregate surfaces which through use and/or age require replacement or repair result in substantial waste of the original components which is economically and environmentally disadvantageous.

It is from a consideration of the shortcomings of existing recovery techniques and the limited re-use of recovered materials that has led to the development of the present invention.

The present invention provides in one aspect a method of separating bitumen and/or aggregate components from a composition comprising them which includes drying, if necessary, bitumen/aggregate composition, adding this composition and a bitumen solvent to a container, causing the bitumen component to dissolve in the solvent, extracting bitumen/solvent mixture from the container, passing air into the container, extracting a mixture of air/solvent from the container, removing dried aggregate component from the container, separating removed aggregate into batches of different size and optionally recovering the bitumen and/or solvent by suitable means.

In a second aspect the invention provides a separator comprising a container for receiving bitumen/aggregate compositions, means for loading the container with such composition, inlet means for receiving bitumen/aggregate composition and inlet means for receiving solvent to dissolve the bitumen component, means for rotating the container, outlet means for extracting bitumen and solvent mixture, air inlet means leading into the container, extraction means for extracting a solvent and air mixture, aggregate outlet means for removing dried aggregate from the container and means to transport removed aggregate for grading.

The separator may include drying means, such as a drying chamber, through which the material to be broken down in the container passes prior to loading. Alternatively, this might be effected by use of the air inlet means which is preferably adapted to direct heated air into the container.

The invention furthermore provides in a third aspect the use of bitumen and/or aggregate separated by a method according to the first aspect in the construction or repair of a pedestrian or vehicular surface.

The container may be in the form of a hollow drum which is preferably cylindrical. The means for loading the container may comprise a driven elevator. The same inlet means may be used both for receiving bitumen/aggregate composition and the bitumen solvent. The aggregate outlet means may also comprise the inlet means for receiving bitumen/aggregate composition and/or inlet means for receiving bitumen solvent.

The means for rotating the container may comprise tyred drive wheels which are preferably pneumatic and may be driven by, for example, an eiectric or other motor. Alternatively, a chain drive may be employed. The interior surface of the container is preferably provided with projections or angled lifters to assist in the breakdown of loaded bitumen/aggregate composition. Preferably the air inlet means are capable of receiving heated air and the extraction means are capable of extracting a mixture of hot air and solvent which mixture may further be passed to solvent recovery means by, e.g. suitable compressors. Additionally, the bitumen and solvent mixture may be processed in recovery means to recover the bitumen and solvent for re-use as required.Separated aggregate may be removed from the container and loaded onto a moving conveyor to grading means for separating/classifying aggregate into batches of different size. A screening unit may be employed for separating aggregate into its original large components and a sand classifier may be used for separating the fine aggregate particles. The container is preferably provided at each end with bearings in which inlets or outlets for the aforesaid materials may be located.

In order that the invention may be illustrated and readily carried into effect an embodiment thereof will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is an elevation of an apparatus for separating bitumen/aggregate, Figure 2 is a plan view of Fig. 1, Figure 3 is an end view showing alternative container drive, and Figure 4 is a plan view of Fig. 3 Referring to Figs. 1 and 2 of the drawings the apparatus comprises a container in the form of a substantially hollow cylindrical drum which may conveniently be approximately 30 metres by 7 metres in diameter. Belt elevators 5 are used to convey bituminous materials for recycling into the container 1. The bitumen/ aggregate composition is conveyed into the inlet 4 which is constituted by a hydraulically operated portal.A bitumen solvent, for example methylene chloride, is added into the same inlet means 4 by means of delivery pipes 6. A specified mixture of bituminous materials and bitumen solvent can thus be obtained inside the container 1. The drum is then rotated by pneumatic tyred drive wheels 2 driven by electric motors (not shown). The wheels make suitable contact with the drum against a steel band fixed around the container. Rotating action of the drum causes the bitumen/aggregate composition and bitumen solvent to mix together whereby the solvent dissolves or at least substantially solubilizes the bitumen component.Dissolution of the bitumen in the solvent is further assisted by means of angled lifters 3 which serve to stir the mixture and also lift the bituminous materials from the base of the drum, up the sides of the drum to the roof where they can fall back under gravity into the mass of solution which will remain at the base of the drum.

After a suitable interval all the bitumen component will have been dissolved and the drum will then contain aggregates free of bitumen together with a solution of bitumen and solvent. Rotation of the drum is stopped whereby it returns to its original loading position, i.e. the position illustrated in Fig. 1 for loading bituminous mixtures and bitumen solvent. The major proportion of bitumen/solvent solution is then extracted from the drum via a sump 8 and removed to a distillery (not shown) where the bitumen is separated from the solvent for both components to be capable of re-use. The operation may need repetition on one or more occasions to force all solution to the sump 8. At this point the drum contains aggregate which is wet with bitumen/solvent solution and probably a small amount of solution remaining on the base of the drum.The drum 1 is further rotated whilst hot air is pumped into the drum through air inlet means in the form of air portal 7. Simultaneously an extractor unit is operated to remove the hot air which will have dried the aggregate and also contain solvent molecules, the extraction being effected through air outlet means in the form of an exit portal 9. This air and solvent mixture can be pumped to, e.g.

compressors (not shown), for recovery of the solvent again for re-use as required. Both inlet 7 and exit 9 portals are fitted inside bearings 12 which allow the portal to remain stationary whilst the drum rotates around these portals.

The portals are supported on hydraulic legs 13 whilst the drum is supported on its own frame and the drive wheels 2. Such hydraulic support provides flexibility of movement in the portal inputs/outputs in the event of variation in level of the drum. Variation in the level of the drum may be caused by atmospheric alterations which may affect tyre pressures in the drum drive wheels 2. The drum is rotated whilst the air is drying the aggregate and being extracted.

After a further interval of rotation the aggregate which has been lifted by the lifters 3 and dropped through the hot air is totally dry. The solvent and hot air mixture has been removed from the container. In the drum there then remains dry and bitumen-free aggregate and the container is stopped but this time in a position displaced at 1800 from the view shown in Fig. 1. The inlet 4 thus serves as aggregate outlet means and upon opening the input portal the aggregate falls onto a rubber conveyor belt 10 which conveys the material away from the drum to a screening unit to separate it into its original components for large aggregate and to a sand classifier to separate the fine aggregates, all preferably for re-use in a method according to the third aspect of the invention.

Item 11 is the power unit required to open the portal 4 for initial loading of bitumen/aggregate and loading of solvent and also for finally removing dried aggregate from the drum. The cycle can then be repeated as required.

Referring to Figs. 3 and 4 an additional steel band 14 is fixed to the container surface and has teeth projections 15. Sprockets 16 driven by motors carry a continuous chain 17 which runs under the drum 1. The teeth engage the chain links providing positive drive to the drum. The motors driving sprockets are reversible to drive the drum in either or both directions. The position of this alternative drive band 14 is adjacent the existing smooth band and wheels 2. The pneumatic tyred wheels 2 then act as a support trunnion and not as a drive means.

In a further modification which is not illustrated the separator further includes a drying chamber through which bitumen/aggregate to be loaded is first dried. Material extracted from existing ashphalt or tarmac will generally be stored in open conditions and consequently is likely to be wet or frosty or covered with snow. It is then of advantage to pass the material to be separated, before loading into the drum, through or past drying means such as a heated chamber to remove surface moisture, ice or snow. The heating action can help the solvent act on the bitumen. Additionally, if the bitumen is warmed during this drying step it should dissolve more rapidly in the solvent.

The invention can thus serve to recover bitumen and aggregate from an old or otherwise unsatisfactory surface and permit a greater degree of reuse than has previously been possible. All recovered aggregate can be reused in bituminous or non-bituminous surface as fresh material and the recovered bitumen can be redeployed after any desirable further treatment.

Claims

1. A method of separating bitumen or tarmacadam and/or aggregate components from a composition comprising them which includes adding the composition and a solvent for the bitumen or tarmacadam to a container, causing the bitumen or tarmacadam component to dissolve in the solvent, extracting bitumen or tarmacadam/solvent mixture from the container, passing air into the container, extracting a mixture of air/solvent from the container, removing dried aggregate component from the container and separating removed aggregate into batches of different size.

2. A method as claimed in claim 1, in which the bitumen or tarmacadam and/or solvent therefor is recovered for further use.

3. A method as claimed in either preceding claim, in which the composition is bituminous.

4. A method as claimed in claim 3, in which the composition comprises asphalt.

5. A method as claimed in any preceding claim, in which the composition to be separated has been obtained from a pedestrian or vehicular surface.

6. A method as claimed in any preceding claim, in which the aggregate-containing composition is initially dried prior to addition to the container.

7. A bitumen or tarmacadam/aggregate separator comprising a container for receiving bitumen or tarmacadam/aggregate composition, means for loading the container with such composition, inlet means for receiving bitumen or tarmacadam/aggregate composition and inlet means for receiving solvent to dissolve the bitumen or tarmacadam component, means for rotating the container, outlet means for extracting bitumen or tarmacadam and solvent mixture, air inlet means leading into the container, extraction means for extracting a solvent and air mixture, aggregate outlet means for removing dried aggregate from the container and means for grading removed aggregate.

8. A separator as claimed in claim 7, including drying means through which material passes prior to loading.

9. A separator as claimed in claim 7 or 8, wherein the air inlet means is adapted to direct heated air into the container.

10. A separator as claimed in any one of claims 7 to 9, wherein the container is in the form of a hollow drum.

11. A separator as claimed in any one of claims 7 to 10, in which the same inlet means is used for receiving both bitumen or tarmacadam/aggregate composition and the bitumen solvent.

12. A separator as claimed in any one of claims 7 to 11, in which the aggregate outlet means also comprises the inlet means for receiving bitumen or tarmacadam/aggregate composition and/or the inlet means for receiving solvent.

13. A separator as claimed in any one of claims 7 to 12, in which the container includes projections or angled lifters.

14. A separator as claimed in any one of claims 7 to 13, in which the air inlet means is adapted to receive heated air and the extraction means is adapted to extract a mixture of hot air and solvent.

15. A separator as claimed in any one of claims 7 to 14, in which the extraction means communicate with solvent recovery means.

16. A separator for bitumen or tarmacadam/aggregate composition substantially as herein described with reference to and as illustrated in any of the accompanying drawings.

17. A method of separating bitumen or tarmacadam and/or aggregate substantially as herein described.

18. A method of separating aggregate and/or bitumen from a composition containing both components substantially as herein described or exemplified.

19. A method of constructing or repairing a pedestrian or vehicular surface using bitumen or tarmacadam and/or aggregate separated in accordance with a method as claimed in any one of claims 1 to 6, 17 or 18.

20. A method of constructing or repairing a pedestrian or vehicular surface using aggregate and/or bitumen recovered in accordance with a method as claimed in any one of claims 1 to 6, 17 or 18.