Examples of waste materials with which the invention is primarily concerned include such materials present in a sludge.

As will be appreciated, sludges, which generally have no value, are generated in various industrial processes. For example, a sludge consisting of an organic solvent and grease is produced when cleansing metal parts to remove grease, a waste material, therefrom.

In addition, sludges may also be produced in the dye, ink and paint industries where dye, ink or paint is dissolved in an organic solvent; such organic solvents including chlorinated solvents, for example, trichloroethylene, perchlorethylene etc. , or aromatic solvents, for example, toluene.

European Patent No. 655,955 discloses a process for encapsulating waste material comprising the steps of providing the waste material in association with a vaporisable liquid, admixing the waste material/liquid composition with a particulate material, preferably, fly ash, and heating the admixture to remove the vaporizable liquid such that the waste material remains firmly bound within the particulate material. In this connection, it is the vaporizable liquid which acts as a vehicle to transport the waste material into the particulate material, that is, before being vaporized. The contents and disclosure of European Patent No. 655,955 are incorporated herein by reference.

One of the unanticipated problems associated with the process of European Patent No. 655,955 is that same is not suitable for treating by encapsulation waste materials consisting of an agglomeration of large diameter, for example, heavy metals, which generally have an average diameter of 75mm. In particular, up until now, it was not appreciated that fly ash, having a particle size of between 10-40 micron, would not efficiently encapsulate waste material including agglomerated particles of large diameter, for example, heavy metals by the sole action of the vaporizable liquid.

According to the present invention there is provided a process for encapsulating waste material including the steps of: providing the waste material in association with a vaporisable liquid, admixing the waste material/liquid composition with a particulate material, preferably fly ash, and heating the admixture to remove the vaporizable liquid characterised in that the process further includes the step of pre-treating the waste material ultrasonically.

It is believed that a process in accordance with the present invention at least addresses the problems outlined above in that the step of pre-treating the waste material ultrasonically produces a slurry of smaller particle size, preferably below 5 microns, thereby making same suitable for use in encapsulating heavy metal waste materials.

In a further aspect of the present invention there is provided a process apparatus suitable for pre-treating a waste material prior to encapsulating same.

An apparatus suitable for carrying out the pre-treatment stage of the process of the present invention will now be described by way of reference to the accompanying drawing, in which: Figure 1 is a schematic diagram of a process plant suitable for carrying out the process of the present invention.

As illustrated in Figure 1, a sludge of variable particle size or dried material waste is delivered into vessel 1 via valve V2. The sludge is then mixed with a suitable solvent, such as toluene, by opening valve V1, preferably at a dilution rate of between 1 to 10.

Once the solvent level is above the agitator or fluidising unit 2, the agitator 2 is started and the solvent is allowed to mix with the waste material.

After a predetermined time, that is, when the solids are thoroughly wetted, valve V3 is opened and the pump 3 is started. The pump 3 may be a simple slurry pump, jet pump, inductor or other hydro-transport device, which may need a transport medium, such as a further solvent, fed into it at pressure via valve V8. It is to be understood that in the case of large material, a maceration pump may be used.

Valves V4 and V6 are then opened and once re-circulation is established, an ultrasonic processor 4, preferably of the type disclosed in PCT GB96/01612, is actuated and the waste material is re-circulated until the slurry is suitably deaglomerated for encapsulation. This can be assessed by taking samples via sample plant valve V7.

Once this is achieved, V4 is closed and V5 is opened with V3, V6, V1 and V5 open. The system can be purged of any solids prior to a plant or system shut-down and the treated waste material is transferred for encapsulation as described in European Patent No. 0,655, 955.

As illustrated, in an alternative embodiment, pump 3, may be replaced by a fluidising unit 5 which can act as a slurry. transport system to either re- circulate the waste material through the ultrasonic processor unit 4 and/or purge the system with solvent with all valves to vessel 1 closed and the valves to the fluidising unit 5 open.

It is to be understood that the process of the present invention, although not limited too, has particular application in the treatment of the following waste streams: waste paint, ink dyes, sludge and dry solids ; tar sludge and solids waste; hydrocarbon sludges and solid waste; textile waste sludges ; metal waste sludges ; solvent degreasing sludges ; dry cleaning sludges ; radioactive sludges ; petrochemical sludges ; waste incinerator ash; waste incinerator fume scrubber materials; removal of hydrocarbon on fire ash to cement industries; waste based toxic sludges.