Method Of Compacting A Slurry By Pressure Filtration
The invention provides a method for the reduction of the volume of solid liquid dispersion or suspension, the method comprising the steps of: (a) providing a receptacle comprising at least one permeate a or semi-permeable membrane; (b) introducing the solid/liquid dispersion or suspension into the receptacle; and (c) applying a mechanical force so as to substantially expel the liquid and compact the solid residue; characterised in that the application of the mechanical force comprises the application of pressure to the solid/liquid dispersion or suspension by means of at least one solid mechanical member, the magnitude of the pressure being increased during the process. The receptacle generally comprises a barrel ( 1 ), the permeable or semi-permeable membrane is most preferably a filter ( 2 ), and the mechanical force is typically applied by means of a source of an inflatable air bag ( 4 ) or a hydraulic ram. The compaction of the solid residue from the waste material may additionally comprise compression of the receptacle. In all embodiments of the invention, the residue obtained is suitable for storage or disposal by any appropriate means. The solid/liquid dispersion or suspension preferably comprises an aqueous slurry of waste material, most preferably an Intermediate Liquid Waste slurry generated in the nuclear industry.
1 . A method for the reduction of the volume of solid/liquid dispersion or suspension, said method comprising the steps of:
(a) providing a receptacle comprising at least one permeable or semi-permeable membrane;
(b) introducing said solid/liquid dispersion or suspension into said receptacle; and
(c) applying a mechanical force so as to substantially expel said liquid and compact the solid residue;
wherein said mechanical force comprises the application of pressure to said solid/liquid dispersion or suspension by means of at least one solid mechanical member, and wherein the magnitude of said pressure being increased during the process.
2 . The method as claimed in claim 1 wherein said solid/liquid dispersion or suspension comprises a slurry of a solid material.
3 . The method as claimed in claim 2 wherein said slurry comprises an aqueous slurry.
4 . The method as claimed in claim 1 wherein said solid/liquid dispersion comprises a waste material.
5 . The method as claimed in claim 4 wherein said waste material comprises a waste material generated in the nuclear industry.
6 . The method as claimed in claim 1 wherein said receptacle comprises a cylindrical container.
7 . The method as claimed in claim 6 wherein said cylindrical container comprises a barrel.
8 . The method as claimed in claim 1 wherein said permeable or semi-permeable membrane comprises a filter.
9 . The method as claimed in claim 8 wherein said filter comprises a woven metal mesh material.
10 . The method as claimed in claim 8 wherein said permeable or semi-permeable membrane is integrated into the surface of the receptacle.
11 . The method as claimed in claim 8 wherein said permeable or semi-permeable membrane is comprised in the base of said receptacle.
12 . The method as claimed in claim 11 wherein said permeable or semi-permeable membrane is additionally comprised in the top and/or sides of said receptacle.
13 . The method as claimed in claim 1 wherein said application of a mechanical force to substantially expel said liquid from said receptacle and compact said solid residue provides an increase in the pressure applied to said solid/liquid dispersion or suspension.
14 . The method as claimed in claim 13 wherein said increase in the pressure applied to said solid/liquid dispersion or suspension is achieved gradually by the action of at least one solid mechanical member on said dispersion or suspension.
15 . The method as claimed in claim 14 wherein said at least one mechanical member comprises at least one inflatable member located within said receptacle.
16 . The method as claimed in claim 15 wherein said at least one inflatable member comprises at least one air bag.
17 . The method as claimed in claim 16 wherein said at least one inflatable member is inflated by the ingress of compressed air.
18 . The method as claimed in claim 15 , wherein said at least one inflatable member additionally comprises at least one rigid member.
19 . The method as claimed in claim 18 wherein said at least one rigid member comprises at least one base plate.
20 . The method as claimed in claim 19 wherein said at least one base plate is comprised of metal.
21 . The method as claimed in claim 1 wherein said mechanical force is applied to the top of the receptacle.
22 . The method as claimed in claim 21 wherein said mechanical force is applied by the action of a rigid member.
23 . The method as claimed in claim 23 wherein said rigid member comprises a piston or hydraulic ram.
24 . The method as claimed in claim 23 wherein said rigid member is comprised of metal.
25 . The method as claimed in claim 24 wherein said rigid member includes holes or grooves adapted to further facilitate the egress of liquor from the system.
26 . The method as claimed in claim 1 wherein the pressure applied to the solid/liquid dispersion or suspension is in the region of 5-200 bar.
27 . The method as claimed in claim 26 wherein said pressure is in the region of 10-50 bar.
28 . The method as claimed in claim 26 wherein an initial pressure in the region of 5-20 bar is applied to said solid/liquid dispersion, and said pressure is increased to a level of 100-200 bar.
29 . The method as claimed in claim 1 wherein a pressure of 300 bar is applied to achieve maximum compaction.
30 . The method as claimed in claim 1 wherein further permeable or semi-permeable membranes are comprised inside said receptacle.
31 . The method as claimed in claim 30 wherein said further permeable or semi-permeable membranes are provided by means of a plate filter.
32 . The method as claimed in claim 31 wherein said plate filter comprises an internal cavity and surfaces comprising permeable or semi-permeable membranes.
33 . The method as claimed in claim 31 wherein said plate filter comprises a disc comprised of metal and having an internal cavity, wherein the top and bottom of said disc are permeable and comprise metal filter media.
34 . The method as claimed in claim 30 wherein means are provided for the removal of liquor which has been filtered through said further permeable or semi-permeable membranes.
35 . The method as claimed in claim 34 wherein said means for the removal of said liquor comprise hoses which are attached to said plate filter such that the expressed liquor may be directed away from said internal cavity.
36 . The method as claimed in claim 35 wherein said hoses comprise reinforced metal hoses.
37 . A method for the reduction of the volume of solid/liquid dispersion or suspension, said method comprising the steps of:
(a) reducing the volume of said solid/liquid dispersion or suspension according to the method as claimed in any preceding claim; and
(b) compacting the receptacle by the application of a further mechanical force.
38 . The method as claimed in claim 37 wherein said further mechanical force comprises very high pressure.
39 . The method as claimed in claim 38 wherein said further mechanical force is applied by the direct mechanical action of at least one solid mechanical member.
40 . The method as claimed in claim 39 wherein said at least one solid mechanical member comprises a hammer, piston or hydraulic ram.
41 . The method as claimed in claim 37 wherein a compaction force of several hundreds of tonnes is applied to achieve maximum compaction of the receptacle.
42 . The method as claimed in claim 41 wherein said compaction force is 200-2000 tonnes.
43 . The method as claimed in claim 42 wherein said compaction force is 1000-2000 tonnes.
44 . The method as claimed in claim 37 wherein the residue is subsequently despatched for storage or disposal.
45 . The method as claimed in claim 37 whenever applied to the treatment of Intermediate Liquid Waste in the nuclear industry.