GB2477924A

GB2477924A - A method of encapsulating waste material

Info

Publication number: GB2477924A
Application number: GB1002667A
Authority: GB
Inventors: Jonathan Quinn; Stanley George Caza
Original assignee: ENCAPSUWASTE Ltd
Current assignee: ENCAPSUWASTE Ltd
Priority date: 2010-02-17
Filing date: 2010-02-17
Publication date: 2011-08-24
Also published as: WO2011101674A2; GB201002667D0

Abstract

A method of encapsulating waste material comprises the steps of forming a first mixture of the waste material and a solvent, vibrating the first mixture to encourage the breakdown of agglomerates of the waste material, introducing a particulate material to the first mixture to produce a second mixture and finally extracting the solvent. The vibration causes the agglomerates of waste to split into smaller components so that the particulate material can encapsulate the waste. The waste may be oleophilic waste such as grease, sludge oil or paint. The solvent maybe a volatile organic solvent such as toluene or trichloroethene and the particulate material maybe a porous material such as fly ash. The first mixture is preferably vibrated by passing an ultrasonic wave 21 through the mixture as the mixture passes along a conduit 19. Ideally, the second mixture is subjected to ultrasonic vibrations as well. Preferably, the first and second mixtures are formed in a mixing chamber 11 with suitable agitation 15 before being sonicated. The solvent maybe extracted in a wipe evaporation chamber 24.

Description

A Method of Encapsulating Waste Material The present invention relates to a method of encapsulating waste material and particularly, but not exclusively, to the encapsulation of agglomerates of waste material.

European Patent No. 0655955 discloses a process for encapsulating waste material comprising the steps of providing the waste material in association with a vaporizable liquid, admixing the waste material/liquid composition with a particulate material such as fly ash and heating the admixture to remove the vaporizable liquid such that the waste material remains firmly bound within the particulate material.

It is found however that the process disclosed in European Patent No. 0655955 is not suitable for encapsulating waste materials consisting of agglomerates of large diameter, for example heavy metals, which generally have an average diameter of 75 microns. In particular, up until now, it was not appreciated that fly ash, having a particle size of between 10-40 microns, would not efficiently encapsulate waste material including agglomerated particles of large diameter, for example heavy metals, by the sole action of the vaporizable liquid.

We have now devised a method of encapsulating waste material which addresses the above-mentioned limitations.

In accordance with the present invention as seen from a first aspect, there is provided a method of encapsulating waste material, the method comprising the steps of: -forming a first mixture of the waste material and a solvent; -vibrating the first mixture to encourage the breakdown of agglomerates of the waste material; -introducing a particulate material to the first mixture to produce a second mixture; and -extracting the solvent.

The vibration causes the agglomerates of waste material to split into smaller component parts so that the particulate material can combine with and suitably encapsulate the waste.

Preferably, the method further comprises the step of vibrating the second mixture.

The first and second mixtures are preferably formed in a mixing chamber comprising a paddle which is arranged to rotate with respect to the mixing chamber to agitate the respective mixture.

Preferably, the first and second mixtures are vibrated by passing an ultrasonic wave through the respective mixture.

The vibration is preferably performed in a flow duct and preferably comprises passing an ultrasonic wave through the respective mixture within the flow duct. The flow duct preferably comprises a coiled portion which is arranged to induce a turbulent flow within the respective mixture. Preferably, the flow duct comprises a hydrocoil.

The particulate material preferably comprises a porous material. The pores within the material serve to retain and thus encapsulate the waste material. Preferably, the particulate material comprises fly ash and more preferably, mechanical fly ash.

Preferably, the waste material comprises oleophilic waste material, such as grease, sludge or paint.

Preferably, the solvent comprises a vaporisable organic liquid and is preferably removed by heating the mixture to cause the solvent to evaporate. The solvent is preferably extracted in a wipe evaporation chamber. Preferably, the wipe evaporation chamber and the mixing chamber comprise a jacket which is arranged to heat and cool the respective chamber to affect the temperature of the mixture.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawing which provides a schematic illustration of a system for carrying out the encapsulation of waste material.

Referring to the drawing there is illustrated a system 10 for carrying out the encapsulation of waste material according to an embodiment of the method of the present invention. The system 10 comprises a mixing chamber 11 within which a mixture of waste material (not shown), for example grease, sludge and heavy metals, and a vaporisable organic liquid or solvent (not shown), such as trichloroethylene or toluene, is introduced. If necessary the waste material (not shown) may be pre-treated in a blender receptacle 12 comprising a blade 13, for example, which is arranged to rotate within the receptacle 12 via a motor 14 and break down the agglomerated waste into smaller particles. In this respect, the blender 12 produces a more fluid waste material, so that it can flow more easily along flow ducts within the system 10.

The mixing chamber 11 may be formed of a corrosion resistant material and comprises an inlet (not shown) for receiving the waste material (not shown) to be encapsulated, an inlet (not shown) for receiving the solvent (not shown) and a further inlet (not shown) for receiving a particulate material (not shown) such as fly ash, or more particularly mechanical fly ash, which is used to encapsulate the waste material (not shown).

The mixing chamber 11 further comprises a shaft 15 which extends into the mixing chamber 11 via an aperture (not shown) arranged at an upper region ha thereof. The aperture (not shown) comprises a seal (not shown) which is arranged to provide a sealing contact with an outer surface of the shaft 15 but which permits the shaft 15 to move within the aperture (not shown). The distal end of the shaft 15 is coupled to a mixing paddle 16 which is arranged near a lower region lib of the mixing chamber 11.

The proximal end of the shaft 15 is coupled to a motor 17 which is arranged to drive the shaft 15 to cause the mixing paddle 16 to rotate within the chamber 11 and thus mix the waste material (not shown), solvent (not shown) and particulate material (not shown) to substantially wet the waste material (not shown).

At the lower region lib of the mixing chamber 11 there is provided an outlet 18 for extracting the mixture (not shown). The outlet 18 is arranged in fluid communication with a flow duct 19 which may also be formed of a corrosion resistant material and which comprises a pump 20 for circulating the mixture (not shown) around the flow duct 19 back into the mixing chamber 11. The flow duct 19 further comprises a vibration unit 21 which is arranged to impart an ultrasonic agitation to the material (not shown) within the flow duct 19 to cause the agglomerated particles (not shown) of waste material to break up into smaller particles. The vibration unit 21 comprises a coiled portion (not shown) of flow duct 19, for example a hydrocoil, disposed therein which is arranged to induce a turbulent flow of the mixture within the duct 19 to further agitate the mixture (not shown).

The flow duct 19 further comprises a junction 22 disposed therein to a further flow duct 23 which is arranged to convey the mixture (not shown) to an evaporation chamber 24, proximate an upper region 24a thereof. The evaporation chamber 24 is substantially cylindrical in transverse cross-section and the mixture (not shown) is passed from the flow duct 23 to a wiper arrangement 25 which is arranged to wipe the mixture (not shown) over an interior surface 26 of the chamber 24 to facilitate the evaporation of the solvent (not shown) therefrom. The arrangement 25 comprises a drive shaft 27 which is coupled at one end to a motor 28 and at the other end to a plurality of wipers 25a which extend substantially parallel to the longitudinal axis of the chamber 24 and which are arranged to wipe along the curved surface of the chamber 24 to distribute a film of mixture (not shown) thereon. The dried residue from the evaporation of the solvent (not shown), namely the encapsulated waste 29, subsequently falls from the chamber 24 and is collected in a bin 30 disposed at a lower region 24b thereof.

The evaporated solvent is passed in the gas phase to a condenser unit 31 via a conduit 32 which extends from the upper region 24a of the evaporation chamber 24. The conduit 32 extends through the condenser unit 31 and is cooled therein by a flow of coolant, such as water, which is arranged to pass in close proximity with the conduit 32. The coolant is passed through the unit 31 between an inlet 33 disposed at one end of the unit 31 and an outlet 33 disposed at an opposite end. The condensate, namely the recovered solvent 34, is arranged to pass out from the condenser unit 31 to a collection chamber 35 which is coupled at one end to a distal end of the conduit 32 and at the other end to the collection chamber 35.

The mixing chamber 11, evaporation chamber 24 and collection chamber 35 comprise a vent 36 disposed at an upper region of the respective chamber 11, 24, 35 and are arranged in fluid communication via a vent duct 38 which extends between the vents 36.

The vent duct 38 comprises a pump 39 disposed therein which is arranged to extract any build up of excess gases within one or more of the chambers 11, 24, 35 to the atmosphere. The vent duct 38 comprises two valves 40, 41 disposed therein, one valve 40, 41 being disposed substantially adjacent the exit point of the vent duct 38 from the mixing chamber 11 and evaporation chamber 24. The system 10 further comprises a return duct 42 which is arranged to pass the recovered solvent 34 from the collection chamber 35 to the mixing chamber 11 via the solvent inlet (not shown) disposed at the upper region ha of the mixing chamber 11.

In use, a sludge (not shown) for example, of variable particle size is introduced into the mixing chamber 11 via the waste inlet (not shown). A solvent of trichloroethylene or toluene, for example, is then added to the mixing chamber 11 at a dilution rate of approximately I part waste material to 10 parts solvent, and the inlets (not shown) to the mixing chamber 11 are closed to substantially seal the chamber 11. The paddle 16 is subsequently rotated to cause the solvent (not shown) and waste to mix to cause the waste to become thoroughly wetted. The outlet 18 to the mixing chamber 11 is then opened and the mixture is pumped along the flow duct 19 using the pump, back into the top of the mixing chamber 11 through the vibration unit 21. This is maintained for approximately 20 minutes to enable the mixture to become suitably mixed and to enable the ultrasonic vibration to breakdown any large agglomerates within the waste material to smaller component parts.

Following the initial mixing and breakdown of large particles, the particulate inlet (not shown) to the mixing chamber 11 is opened and a porous material, such as fly ash is introduced into the mixing chamber 11. The inlet is subsequently closed and the mixture is circulated for approximately a further 20 minutes through the flow duct 19 and vibration unit 21 and back into the mixing chamber 11. The vibration unit 21 generates an ultrasonic vibration within the waste material, thereby causing the agglomerated particles (not shown) of waste material to break up into smaller particles. The ultrasonic vibration further causes the pores or cavities within the fly ash to expand. This break up of waste material and the expansion of the pores in the fly ash causes the waste material to pass into the pores of the fly ash. Valve 43 disposed within the flow duct 19 to the vibration unit 21 is then closed and a valve 44 downstream of the junction 22 is opened to enable the fluid mixture to pass into the evaporation chamber 24. During this process, the mixing chamber 11 and evaporation chamber 24 are heated using jackets 45 which are secured around the outside of the respective chamber. The jackets 45 comprise a convoluted channel (not shown) disposed therein for receiving and passing a liquid (not shown) to and from a temperature control unit 46 via a ducting arrangement 47. The unit 46 is arranged to affect the temperature of the liquid and thus the temperature of the mixture within the mixing and evaporation chambers 11, 24 to encourage the dissolving of the waste within the solvent and to subsequently encourage the evaporation of the solvent from the mixture, respectively.

The fluid mixture is passed subsequently from the mixing chamber 11 to the evaporation chamber 24 under the action of the pump 20. The pump 20 causes the mixture to pass along flow ducts 19 and 23, to the evaporation chamber 24, whereupon the mixture becomes wiped along the interior surface 26 of the chamber 24 using the wiper arrangement 25. Once all the mixture has passed from the mixing chamber 11 to the evaporation chamber 24, the valve 44 is then closed. The jacket 45 disposed around the evaporation chamber 24 is subsequently used to heat the wall of the chamber 24 to encourage the solvent within the film of mixture distributed on the interior surface 26 thereof by the wiper arrangement 25, to evaporate. Once the mixture is fully dried, namely once all the solvent has evaporated, the waste material becomes fully encapsulated within pores within the fly ash. The dry residue subsequently falls off the walls of the chamber 24 and is collected in the bin 30 disposed beneath the open lower region 24b of the chamber 24. The resulting encapsulated waste material 29 is inert and may be used to create an aggregate or building element, or may be used as a filler, for

example.

The extracted gaseous solvent, namely the evaporate, subsequently passes under the action of the vacuum into the conduit 32 which passes the evaporate into the condenser unit 31. The condenser unit 31 causes the evaporate to return to a liquid phase and the resulting condensate 34, namely the solvent is collected in the collection chamber 35.

The condensate may be recycled back to the mixing chamber 11 for further use or extracted as required.

From the foregoing therefore it is evident that the method of the present invention provides for a more versatile encapsulation since waste material comprising large diameter agglomerates may also be suitably treated with fly ash.

Claims

Claims 1. A method of encapsulating waste material, the method comprising the steps of: -forming a first mixture of the waste material and a solvent; -vibrating the first mixture to encourage the breakdown of agglomerates of the waste material; -introducing a particulate material to the first mixture to produce a second mixture; and -extracting the solvent.
2. A method according to claim 1, further comprising the step of vibrating the second mixture.
3. A method according to claim I or 2, wherein the first and second mixtures are formed in a mixing chamber comprising a paddle which is arranged to rotate with respect to the mixing chamber to agitate the respective mixture.
4. A method according to any preceding claim, wherein the first and second mixtures are vibrated by passing an ultrasonic wave through the respective mixture.
5. A method according to any preceding claim, wherein the vibration is performed in a flow duct.
6. A method according to claim 5, wherein the vibration comprises passing an ultrasonic wave through the respective mixture within the flow duct.
7. A method according to claim 5 or 6, wherein the flow duct comprises a coiled portion which is arranged to induce a turbulent flow within the respective mixture.
8. A method according to any of claims 5 to 7, wherein the flow duct comprises a hydrocoil.
9. A method according to any preceding claim, wherein the particulate material comprises a porous material.
10. A method according to any preceding claim, wherein the particulate material comprises fly ash.
11. A method according to any preceding claim, wherein the waste material comprises oleophilic waste material.
12. A method according to any preceding claim, wherein the solvent comprises a vaporisable organic liquid.
13. A method according to any preceding claim, wherein the solvent is extracted by heating the mixture to cause the solvent to evaporate.
14. A method according to any preceding claim, wherein the solvent is extracted in a wipe evaporation chamber.
15. A method according to claim 14 as appended to claim 2, wherein the wipe evaporation chamber and the mixing chamber comprise a jacket which is arranged to heat and cool the respective chamber to affect the temperature of the mixture.