GB2517175A

GB2517175A - Apparatus and method for washing aggregate

Info

Publication number: GB2517175A
Application number: GB1314517.2A
Authority: GB
Inventors: Simon Wells
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-08-14
Filing date: 2013-08-14
Publication date: 2015-02-18
Anticipated expiration: 2033-08-14
Also published as: GB2517175B; GB201314517D0

Abstract

Apparatus for washing aggregate 14, the apparatus comprises a hopper 12 to receive aggregate, an aggregate washing means 16, 18 having a base (28, fig 4) comprising apertures (30, fig 4) and means to feed aggregate 14 from the hopper 12 to the washing means 16, 18, the washing means arranged to retain at least a portion of the aggregate 14 while allowing wash liquid to pass through the apertures (30, fig 4) after washing the aggregate14, a liquid storage tank 32; a liquid supply means 20, 22 operable to supply liquid from the tank 32 and to direct liquid onto the washing means 16, 18 and aggregate outlet means 36 to allow aggregate to be removed from the washing means. The method includes collecting the wash liquid from the washing means 16, 18 and directing it along a liquid flow pathway 38 to the tank 32 and adding neutralising material to liquid in the tank 32 under the control of a pH sensor 52 in the tank 32 so that it can be reused.

Description

Apparatus and method for washing aggregate

Field of the Invention

The present invention relates to an apparatus and a method for washing aggregate used with cement in construction, and in particular to adjust the pH of one or both of the aggregate and wash liquid for re-use or disposal

Background

Waste liquid collection and neutralisation apparatus is known in which liquid that has been used to dilute used concrete or cement or to wash tools or equipment is stored and has its pH adjusted towards neutral in order for it to be disposed of safely.

The waste liquid may be re-used for further concrete mixing in some cases. It is also advantageous to re-use aggregates, and to be able to process such aggregates locally on a construction site. No apparatus is known that is adapted for this purpose. The present invention provides such apparatus and a method using the apparatus.

Prior Art

Accordingly a number of patent applications have been filed in an attempt to resolve the problem or similar, including the following: W0201082038 assigned to Siltbuster discloses a method of neutralising washout from concreting operations comprises the steps of providing an unit to contain the washout, providing the unit with a store of neutralising agent, receiving the washout in the unit, transferring a liquid washwater component from the washout receiving region of the unit to a washwater containment region of the unit, and supplying the neutralising agent to the washout in the washwater containment region of the unit.

Preferably, the neutralising agent is carbon dioxide gas. The pH of the washwater in the washwater containment region may be measured and the supply of neutralising agent regulated based on the measured pH. There may be baskets, provided in the washout receiving region such that solid material is retained therein, whilst the washwater drains into the washwater containment region. In another aspect a unit for treating washout is also claimed.

W0201 040999 to Siltbuster discloses a method and apparatus for treating alkaline water comprises the steps of introducing water into a first compartment, bubbling carbon dioxide into the water in the first compartment which causes solids to precipitate, transferring the water with the precipitate into a second compartment in which the precipitate is separated from the water, then transferring the water into a third compartment where carbon dioxide is bubbled into the water to reduce the pH of the water, and finally removing the treated water from the third compartment. The pH of the water removed from the third compartment is lower than the pH of the water in the second compartment. The compartments are provided in a single portable unit.

The first compartment and third compartment include sparging arrangements to supply the carbon dioxide. The second compartment comprises inclined plates to aid solid separation by slowing the flow of the water.

Both the above apparatus are means to neutralise waste water from a washing process, but do not provide means to wash, sort and/or recycle aggregate or solids.

W0200164348 discloses a mechanical and chemical method for regenerating waste water from a concrete plant characterised in that it consists in: (a) filtering said waste water with decreasing filtering gauges; (b) recuperating in parallel the retained material at each filtering; (c) finally, subjecting the resulting filtrate to a chemical treatment adapted to reduce simultaneously the hardness and the pH of said filtrate.

This device is also directed to treatment of waste liquid, but not aggregate.

Summary of the Invention

According to the present invention there is provided a device for washing aggregate in liquid comprising: a hopper to receive aggregate; an aggregate washing means having a base comprising apertures and means to feed aggregate from the hopper to the washing means, the washing means arranged to retain at least a portion of the aggregate while allowing liquid to pass through the apertures; a liquid storage tank; a liquid supply means operable to supply liquid from the tank and to direct liquid onto the washing means; and aggregate outlet means to allow aggregate to be removed from the washing means.

In preferred embodiments a liquid flow pathway is included via which liquid returns to the tank. A treatment or neutralisation means may be advantageously provided which is, adapted to treat liquid before or within the tank in preferred embodiments so as to at least adjust the pH of the liquid. In some further embodiments said treatment may include filtration.

Said liquid typically comprises liquid and wash liquid. By wash liquid is meant liquid that has passed over or through the aggregate.

In one embodiment the washing means comprises a filter screen suspended within the tank.

In one embodiment the washing means comprises a washing platform in the form of a sloping screen.

In one embodiment the washing means comprises a washing platform in the form of a conveyor belt having apertures within it.

In one embodiment the washing means comprises a washing platform in the form of a vibrating screen.

Preferably the washing means is arranged to retain at least a portion of the aggregate, while allowing liquid to pass through the apertures, subsequent to washing.

In one embodiment the apparatus comprises a wash liquid collection means beneath the washing means to collect liquid falling through the apertures.

In one embodiment the apparatus comprises one or more liquid jets operable to direct liquid towards aggregate on the washing means.

In one embodiment the apparatus comprises a first and a second sloping washing platform and at least one liquid jet directed at each platform, the lower end of the first upper washing platform being adjacent to the upper end of the second lower washing platform.

In one embodiment the aggregate moves along an aggregate pathway from the inlet hopper, onto a first sloping aggregate washing platform adjacent to its upper end, down the platform and falling from its lower end onto the second sloping aggregate washing platform adjacent to its upper end, down the second platform to an aggregate outlet means.

In one embodiment the first upper washing platform comprises first apertures larger than the second apertures in the second lower washing platform, the first apertures being sized to retain a larger size fraction of the aggregate while allowing a smaller size fraction to fall through them onto the second sloping platform, the second apertures being sized to retain the smaller size fraction.

In one embodiment the apparatus comprises a first aggregate outlet means from the first washing platform and a second aggregate outlet means from the second washing platform.

In one embodiment the neutralising means comprises a source of neutralising material that is alkaline when in solution and means to introduce the neutralising material into the tank.

In one embodiment the apparatus comprises agitator means to mix the liquid and neutralising material.

In one embodiment the neutralising material is carbon dioxide and the source comprises a cylinder of pressurised carbon dioxide gas.

In one embodiment the neutralising means comprises gas dispersing means adapted to disperse carbon dioxide gas into the tank. In one embodiment the gas dispersing means comprises a gas diffuser. In one embodiment the gas dispersing means and the agitator means may be combined in a common unit.

In one embodiment the apparatus comprises a control means operable to control one or more of the flow of aggregate from the hopper; vibration of the vibrating screens; liquid flow through the liquid jets and liquid flow pathway; and/or pumps provided to circulate liquid. In one embodiment the neutralisation means comprises a pH sensor and the control means is adapted to read a signal from the pH sensor and to control the supply of the neutralising material to the tank.

In one embodiment the control means operates in accordance with instructions stored on a data storage means forming part of the control means.

In one embodiment the control means is enabled and operable to control the pH of the liquid in the tank.

In one embodiment the control means is operable to maintain the pH within a range of a set point pH. In one embodiment the set point pH may be a substantially neutral pH, for example pH 7.

In one embodiment the apparatus comprises a wash liquid flow pathway from the liquid collection means into the tank. In one embodiment the wash liquid flow pathway comprises a silt collection means having a silt collection outlet adapted to allow silt to be removed from the liquid flow pathway.

In one embodiment the tank comprises silt removal means to remove silt collected at the base of the tank, for example a silt outlet provided near the lowest point of the tank In some preferred embodiments the apparatus comprises use of solar trickle chargers to maintain battery levels.

In one embodiment the apparatus is adapted to recirculate liquid from the tank to the liquid jets.

In this way the apparatus provides an effective means to wash aggregate in order that it may be re-used and to re-use the washing liquid while maintaining the pH of the washing liquid within an acceptable range. Addition of neutralising agent to the wash liquid acts in some embodiments and in some uses to precipitate dissolved species from the liquid in the form of a solid precipitate. Silt and precipitate are removed from the washing liquid and as the liquid is preferably re-circulated from the tank, which is maintained at a control pH value, the silt is also at a pH within a known range of the control pH value, and so may be safely disposed of or re-used in further concrete mixing.

In one embodiment the control means comprises pH threshold detection means to initiate control actions of the apparatus if the pH varies from a control pH by more than a chosen amount. Such control actions may comprise sounding an alarm, stopping the flow of aggregate from the hopper and stopping flow of liquid through the liquid flow pathway.

In one embodiment the apparatus is provided as a self-contained unit comprising components of the apparatus arranged in a format based on the footprint of a standard pallet, and so is adapted to be movable by a forklift truck. For example the apparatus may have the format of a standard IBC container. In one embodiment the apparatus may have footprint dimensions of approximately 1.02m by 1.20m. The height may be in the range 1.0 to 2m, preferably in the range 1.0 to 1.15m.

In one embodiment the apparatus may be provided in the footprint of a standard shipping container.

In this way the apparatus may be made portable and easy to transport and install on a construction site.

In one embodiment the apparatus is powered from a standard site-available mains power supply, for example 3-phase, 230V or 1 iSV single phase supplies. In one embodiment the apparatus is adapted to operate from a battery forming part of the apparatus chargeable from the main supply.

According to a further aspect the invention provides a method for washing of aggregate comprising the steps of: providing an apparatus as described herein; adding aggregate to the aggregate inlet hopper; allowing aggregate to move across the washing platform; directing liquid at the platform to wash the aggregate; discharging aggregate from the platform for re-use; collecting the wash liquid from the washing platform and directing it along a liquid flow pathway to a tank; and adding neutralising material to liquid in the tank under the control of a ph sensor in the tank.

In one embodiment the method comprises the further steps of maintaining the pH in the tank within a chosen range of a chosen set point.

In one embodiment the chosen set point is substantially neutral pH.

In one embodiment the method comprises the further step of recirculating liquid from the tank for use in washing the aggregate.

The invention has been described by way of examples only and it will be appreciated that variation may be made to the above-mentioned embodiments without departing from the scope of invention.

With respect to the above description then, it is to be realised that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Brief Description of Figures

Figure 1 shows an isometric view of an embodiment of an apparatus according to the invention.

Figure 2 shows a side view of the embodiment shown in figure 1.

Figure 3 shows a rear view of the embodiment shown in figure 1.

Figure 4 shows a top view of the embodiment shown in figure 1.

Figure 5 shows a cross-section of the embodiment shown in figure 1.

Detailed Description of Figures

Referring to figures 1 to 5, an embodiment 10 of a device for washing aggregate comprises: A hopper 12 to receive aggregate 14, a first and a second aggregate washing means in the form of a first sloping washing platform 16, and a second sloping washing platform 18, at least the first sloping washing platform being a vibrating screen driven by a motor 171 a first liquid jet 20 directed at the first platform and a second liquid jet 22 directed at the second platform, the lower end 24 of the first upper washing platform being adjacent to the upper end 26 of the second lower washing platform.

Each washing platform has a base 28 comprising apertures 30 and means to feed aggregate from the hopper to the washing means, the washing means being adapted to retain at least a portion of the aggregate while allowing wash liquid to pass through the apertures after washing the aggregate.

The apparatus comprises a liquid storage tank 32, and a liquid supply means 34 operable to supply liquid from the tank and to direct liquid onto the washing means, comprising a pump (not shown in the figures), aggregate outlet means 36 to allow aggregate to be removed from the washing means, a wash liquid flow pathway 38 via which wash liquid used to wash the aggregate returns to the tank 32, a treatment means adapted to treat liquid within the tank so as to adjust the pH of the liquid, and liquid drain means (not shown) to drain treated liquid from the tank.

In use the aggregate moves along an aggregate pathway from the inlet hopper 12, onto a first sloping vibrating screen 16 adjacent to its upper end, down the screen, falling from its lower end onto the second sloping aggregate washing platform 18 adjacent to its upper end 26, down the second platform to an aggregate outlet means 36.

The neutralising means uses carbon dioxide as a neutralising material and the apparatus comprises a cylinder 40 of pressurised carbon dioxide gas, and gas dispersing means in the form of a gas diffuser 42 adapted to disperse carbon dioxide gas into the tank.

The apparatus comprises a control means 50 operable to control one or more of the flow of aggregate from the hopper, vibration of the vibrating screens, liquid flow through the liquid jets and liquid flow pathway and pumps provided to circulate liquid.

In one embodiment the neutralisation means comprises a pH sensor 52 and the control means is adapted to read a signal from the pH sensor and to control the supply of carbon monoxide to the tank.

The control means operates in accordance with instructions stored on a data storage means forming part of the control means and is operable to control the pH of the liquid in the tank. The control means may be programmed and/or operated from a control panel 54.

In this embodiment the wash liquid flow pathway comprises a silt collection means 56 having a silt collection outlet 58 adapted to allow silt to be removed from the liquid flow pathway.

Preferably tank comprises silt removal means to remove silt collected at the base of the tank, for example a silt outlet provided near the lowest point of the tank.

In this embodiment the apparatus is provided as a self-contained unit comprising components of the apparatus arranged in the format of a standard IBC container and has footprint dimensions of approximately 1.02m by 1.20m. The height may be in the range 1.0 to 2m, preferably in the range 1.0 to 1.15m. The apparatus is built on a frame 62 having apertures 64 in the base 66 adapted to allow it to be lifted by a fork lift truck.

The apparatus is powered from a standard site-available mains power supply, for example 3-phase, 230V or 1 15V single phase supplies and is adapted to operate from a battery 60 forming part of the apparatus chargeable from the main supply.

The apparatus may be built from materials known in the art, for example metal components for the bed of the vibrating screen(s) and washing platform(s), a metal frame and base, engineering polymer tank, either metal or plastic pipework, and a pressurised tank for carbon dioxide as known in the art. The pH electrode may be a ruggedised industrial electrode as known in the art.

Claims

Claims 1. Apparatus for washing aggregate, the apparatus comprising: a hopper to receive aggregate; an aggregate washing means having a base comprising apertures and means to feed aggregate from the hopper to the washing means, the washing means arranged to retain at least a portion of the aggregate while allowing wash liquid to pass through the apertures after washing the aggregate; a liquid storage tank; a liquid supply means operable to supply liquid from the tank and to direct liquid onto the washing means; and aggregate outlet means to allow aggregate to be removed from the washing means.
2. Apparatus as claimed in claim 1 wherein the washing means comprises a filter screen suspended within the tank.
3. Apparatus as claimed in claim I wherein the washing means comprises a washing platform in the form of a sloping screen.
4. Apparatus as claimed in claim I wherein the washing means comprises a washing platform in the form of a conveyor belt having apertures within it.
5. Apparatus as claimed in claim 1 wherein the washing means comprises a washing platform in the form of a vibrating screen.
6. Apparatus as claimed in any claim above wherein the apparatus comprises a wash liquid collection means located beneath the washing means to collect liquid falling through the apertures.
7. Apparatus as claimed in any claim above wherein the apparatus comprises one or more liquid jets operable to direct liquid towards aggregate on the washing means.
8. Apparatus as claimed in any of claims 3 to 7 wherein the apparatus comprises a first and a second sloping washing platform and at least one liquid jet directed at each platform, the lower end of the first upper washing platform being adjacent to the upper end of the second lower washing platform.
9. Apparatus as claimed in any of claims 3 to 8 wherein in use the aggregate moves along an aggregate pathway from the inlet hopper, onto a first sloping aggregate washing platform adjacent to,its upper end, down the platform and falling from its lower end onto the second sloping aggregate washing platform adjacent to its upper end, down the second platform to an aggregate outlet means.
10. Apparatus as claimed in any of claims 3 to 9 wherein the first upper washing platform comprises first apertures larger than the second apertures in the second lower washing platform, the first apertures being sized to retain a larger size fraction of the aggregate while allowing a smaller size fraction to fall through them onto the second sloping platform, the second apertures being sized to retain the smaller size fraction.
11. Apparatus as claimed in any of claims 3 to 10 comprising a first aggregate outlet means from the first washing platform and a second aggregate outlet means from the second washing platform.
12. Apparatus as claimed in any claim above wherein a neutralising or treatment means is included comprising a source of neutralising material that is acidic when in solution and means to introduce the neutralising material into the tank.
13. Apparatus as claimed in claim 12 wherein the treatment means comprises agitator means to mix the liquid and neutralising material.
14. Apparatus as claimed in any of claims 12 to 13 above wherein the neutralising material is carbon dioxide and the source comprises a cylinder of pressurised carbon dioxide gas.
15. Apparatus as claimed in any claim above comprising a control means operable to control one or more of: the flow of aggregate from the hopper; vibration of the vibrating screens; liquid flow; andlor pumps provided to circulate liquid; wherein a liquid treatment means comprises a pH sensor and the control means is adapted to read a signal from the pH sensor and to control supply of neutralising material to the tank.
16. Apparatus as claimed in claim 15 wherein the control means is operable to control the pH of the liquid in the tank within a range of a set point pH.
17. Apparatus as claimed in claim 15 wherein the set point pH is a substantially neutral pH, for example pH 7.
16. Apparatus as claimed in any of claims 7 to 17 above adapted to recirculate liquid from the tank to the liquid jets.
19. Apparatus as claimed in any claim above wherein the control means is operable to control actions of the apparatus if the pH varies from a control pH by more than a chosen amount comprising one or more of sounding an alarm, stopping the flow of aggregate from the hopper and stopping flow of liquid through the liquid flow pathway.
20. Apparatus as claimed in any claim above provided as a self-contained unit comprising components of the apparatus arranged in a format based on the footprint of a standard pallet.
21. Apparatus as claimed in any claim above in the format of a standard IBC container having footprint dimensions of approximately 1.02m by I.20m.
22. Apparatus as claimed in any claim above adapted to be powered from a standard site-available mains power supply such as 3-phase, 230V or 1 15V single phase supplies and adapted to operate from a battery forming part of the apparatus chargeable from the mains supply.
23. A method for washing of aggregate comprising the steps of: providing an apparatus as claimed in any one of claims ito 22; adding aggregate to the aggregate inlet hopper; allowing aggregate to move across the washing platform; directing liquid at the platform to wash the aggregate; dishcarging aggregate from the platform for re-use; collecting the wash liquid from the washing platform and directing it along a liquid flow pathway to a tank; and adding neutralising material to liquid in the tank under the control of a pH sensor in the tank.
24. A method according to claim 23 comprising the further step of maintaining the pH in the tank within a chosen range of a chosen set point.
25. A method according to claim 24 wherein the chosen set point is substantially neutral pH.
26. A method according to any of claims 23 to 25 comprising the further step of recirculating liquid from the tank for use in washing the aggregate.
27. An apparatus substantially as described herein and with reference to the figures.