Title of Invention	"A METHOD OF REFINING A METAL-CONTAINING WASTE TO RECOVER THE METAL THEREFROM"
Abstract	A method of refining a metal-containing waste, containing at least one metal selected from the group consisting of platinum group metals, silver and/or gold, to recover the metal therefrom, which method comprising receiving a bulk sample of the waste of unknown composition, dispersing the bulk sample in water to form a bulk sample dispersion, stirring the bulk sample dispersion in a mixing tank (1), continuously withdrawing from the bottom section of the tank a portion of the of the dispersion and recycling it via a recycle loop (3) to the upper portion of the tank such that a substantially homogeneous dispersion is obtained in at least the recycle loop, characterized by taking a representative sample of the bulk sample dispersion from the recycle loop to yield a reduced volume sample, assaying said reduced volume sample for the metal, calculating the content of the metal in the remaining bulk sample dispersion, and recovering the metal from the remaining bulk sample dispersion in a supercritical water oxidation process.

Title of Invention

"A METHOD OF REFINING A METAL-CONTAINING WASTE TO RECOVER THE METAL THEREFROM"

Abstract

A method of refining a metal-containing waste, containing at least one metal selected from the group consisting of platinum group metals, silver and/or gold, to recover the metal therefrom, which method comprising receiving a bulk sample of the waste of unknown composition, dispersing the bulk sample in water to form a bulk sample dispersion, stirring the bulk sample dispersion in a mixing tank (1), continuously withdrawing from the bottom section of the tank a portion of the of the dispersion and recycling it via a recycle loop (3) to the upper portion of the tank such that a substantially homogeneous dispersion is obtained in at least the recycle loop, characterized by taking a representative sample of the bulk sample dispersion from the recycle loop to yield a reduced volume sample, assaying said reduced volume sample for the metal, calculating the content of the metal in the remaining bulk sample dispersion, and recovering the metal from the remaining bulk sample dispersion in a supercritical water oxidation process.

Full Text	The present invention relates to a method of refining a metal-containing waste to recover the metal therefrom. The present invention concerns a method of refining a metal-containing waste to recover the metal therefrom, wherein the metal is selected from the group consisting of platinum group metals, silver and/or gold. Many processes involve the sampling of bulk variable feedstocks, and this has especial importance where the feedstock contains one or more high value components. For example, in methods of recycling and refining waste catalysts, or other wastes containing materials such as the platinum group metals, silver and gold, the refining organisation needs to determine levels of such metals in the bulk material to assess the value of metals to be credited to the owner of the bulk material. There is a need for improved sampling methods and, accordingly, for improved metal assays within such methods. The bulk materials acting as feedstocks in the present invention may be in any nongaseous form, for example liquid, such as waste homogeneous catalyst, solid or slurry. If the feedstock is a solid, such as a filter cake or other solid form, it is necessary to break up the solid, by for example crushing or milling so that the bulk is dispersible. Desirably, the particle size of solids is less than 500 µm, preferably less than 100 urn, bearing in mind the need to obtain suspension as a homogeneous slurry. The present invention accordingly provides a method of refining a metal-containing waste, containing at least one metal selected from the group consisting of platinum group metals, silver and/or gold, to recover the metal therefrom, which method comprising receiving a bulk sample of the waste of unknown composition, dispersing the bulk sample in water to form a bulk sample dispersion, stirring the bulk sample dispersion in a mixing tank, continuously withdrawing from the bottom section of the tank a portion of the dispersion and recycling it via a recycle loop to the upper portion of the tank such that a substantially homogeneous dispersion is obtained in at least the recycle loop, taking a representative sample of the bulk sample dispersion from the recycle loop to yield a reduced volume sample, assaying said reduced volume sample for the metal, calculating the content of the metal in the remaining bulk sample dispersion, and recovering the metal from the remaining bulk sample dispersion in a supercritical water oxidation process. If necessary, the reduced volume sample may be subsequently sub-divided and representative sub-division samples are assayed or analysed for key components in conventional manner. Preferably, the supercritical water oxidation process is as described in WO 01/83834. For technical reasons, conventional refining techniques do not sample and assay the bulk sample, but only sample and assay after one or more preliminary concentration or refining steps. Accordingly, the present invention represents a significant departure from the state of tfie art, and is believed to offer advantages in speed of processing, and hence significantly reduce the cost of financing "work in progress". The method of sampling according to the invention desirably uses a conical-ended stirred mixing tank, fitted with a pipe at the apex of the cone. Other tank shapes may, however, be used, for example a hemispherical, frusto -conical or similar section base. The recycle of dispersion is to the upper section of the tank, and may be made to any one or more points in said upper section. Conveniently, a single recycle point is approximately half-way along a radius of the tank. Suitable mixing speeds, impeller shapes, recycle line diameters and recycle rates may vary according to the volume of the mixing tank and volume of the sample dispersion, and may be established by routine experiment. The aim is, of course, to ensure that the representative sample taken from the recycle loop is truly representative and this is essentially achieved by ensuring that the dispersion is homogenised. Particularly preferred bulk sample feedstocks are spent catalysts, especially those comprising a platinum group metal carried on a carbon support. Such spent catalysts generally contain considerable quantities of organic solvent. However, since these are often regarded as wastes, they may be contaminated with a variety of organic (e.g. paper, cloth etc.) or inorganic (e.g. nuts and bolts etc.) matter. Such contaminating matter is desirably screened out. Suitable liquid or slurry samplers are commercially available for use in the recycle loop. The volume taken is not especially important. The methods used for assay or further analysis are conventional and form no part of this invention. Depending upon the nature of the bulk sample and especially the nature of solvents or residues associated with the values in the bulk sample, an additive to improve dispersion in the water may be required. Conventional and commercially available surfactants may be used if the bulk sample is essentially non-polar. Initial tests on bulk samples which have a polar character indicate that certain surfactants, e.g. "Quadralene"™ (used for glassware washing'machines) may be advantageously used. Suitable concentrations of bulk sample in the water are from 10-15 wt%. Conveniently, the bulk sample, crushed or milled if necessary, is added, together with an appropriate surfactant, to the tank already charged with water, mixing is begun and the recycle initiated. The present invention will now be described by way of example only and with reference to the accompanying drawings in which; Figure 1 shows a schematic representation of apparatus for carrying out sampling according to the invention; and, Figure 2 is a graph comparing metal values for a range of samples evaluated using the method of the present invention with those obtained using conventional pyrolysis. With reference to Fig. 1, apparatus for carrying out the invention includes a mixing tank, 1. In proving trials, a steel tank of 600 litre capacity, with a conical bottom, has been used. A conventional axial impeller, 2, is fitted in tank 1, to mix the contents. A recycle line, 3, of 19 mm internal diameter is attached to the conical base of tank 1. The recycle line is connected to a pump, 4, before being returned to the upper section of tank 1. The pump has been operated at 4400 l/hr. Fitted downstream of the pump is a commercial liquid/slurry sampler "Isolock"™ 5, which collects a sample volume of 500 ml. The recycle line may include a line, 6, to allow the contents of the tank to be emptied or further processed. The charge of bulk sample is conveniently received in a bulk container, 7, fitted with a pump, 8, for water, wash water and/or surfactant. The bulk sample is fed to a screen, 9, to remove gross contaminants; a screen size of 3-10 mm size is generally appropriate for spent carbon-based catalyst. The sample is suitably passed to an assay laboratory, where it is resuspended and kept agitated. Sub-samples may be taken by using tube sampling. It is generally good practice to take a number of samples, some of which may be retained as a reference sample, to minimise the opportunity for process variability. For example, where the bulk sample consists essentially of spent carbon-supported catalyst with organic solvent, it is preferred to oxidise all organic/carbonaceous material to CO2, using a mixture of sulphuric and nitric acids. The residual precious metal can then be dissolved in a pre-set volume of aqua regia and analysed, for example using Inductively Coupled Plasma Emission Spectroscopy against standard solutions of known platinum group metal content. In order that the mvention may be more fully understood, an example showing the efficacy of the sampling step of the method of the invention is provided by way of illustration only, compared with a known pyrolysis sampling step. EXAMPLE Fifty-one catalyst samples were evaluated using the method of the invention. The samples were sourced from a wide range of used and unused materials with a range of physical properties and impurities. Results are shown in Table 1. Recovery is measured as the ratio (expressed as a percentage) between the amount of metal evaluated in each sample using the method of the invention and that evaluated by conventional pyrolysis. Excellent agreement was found between the two methods indicating that method of the invention provides an accurate and reliable measure of total metal content. The results of Table 1 are illustrated graphically in Fig. 2, with a line of unit gradient for reference. Table 1. (Table Removed) WE CLAIM; 1. A method of refining a metal-containing waste, containing at least one metal selected from the group consisting of platinum group metals, silver and/or gold, to recover the metal therefrom, which method comprising receiving a bulk sample of the waste of unknown composition, dispersing the bulk sample in water to form a bulk sample dispersion, stirring the bulk sample dispersion in a mixing tank (1), continuously withdrawing from the bottom section of the tank a portion of the of the dispersion and recycling it via a recycle loop (3) to the upper portion of the tank such that a substantially homogeneous dispersion is obtained in at least the recycle loop, characterized by taking a representative sample of the bulk sample dispersion from the recycle loop to yield a reduced volume sample, assaying said reduced volume sample for the metal, calculating the content of the metal in the remaining bulk sample dispersion, and recovering the metal from the remaining bulk sample dispersion in a supercritical water oxidation process. 2. A method as claimed in claim 1, wherein the bulk sample is a spent catalyst. 3. A method as claimed in claim 2, wherein the spent catalyst is a platinum group metal on carbon catalyst. 4. A method as claimed in any one of the preceding claims, where a surfactant is added to the water or the sample to facilitate dispersion. 5. A method as claimed in any one of the preceding claims, wherein the sample is a solid having particle size of less than 500µm, preferable less than l00µm. 6. A method as claimed in any one of the preceding claims, wherein the concentration of the bulk sample in the liquid is between 10 and 15wt%.

Full Text

The present invention relates to a method of refining a metal-containing waste to recover the metal therefrom.
The present invention concerns a method of refining a metal-containing waste to recover the metal therefrom, wherein the metal is selected from the group consisting of platinum group metals, silver and/or gold.
Many processes involve the sampling of bulk variable feedstocks, and this has especial importance where the feedstock contains one or more high value components. For example, in methods of recycling and refining waste catalysts, or other wastes containing materials such as the platinum group metals, silver and gold, the refining organisation needs to determine levels of such metals in the bulk material to assess the value of metals to be credited to the owner of the bulk material. There is a need for improved sampling methods and, accordingly, for improved metal assays within such methods.
The bulk materials acting as feedstocks in the present invention may be in any nongaseous form, for example liquid, such as waste homogeneous catalyst, solid or slurry. If the feedstock is a solid, such as a filter cake or other solid form, it is necessary to break up the solid, by for example crushing or milling so that the bulk is dispersible. Desirably, the particle size of solids is less than 500 µm, preferably less than 100 urn, bearing in mind the need to obtain suspension as a homogeneous slurry.
The present invention accordingly provides a method of refining a metal-containing waste, containing at least one metal selected from the group consisting of platinum group metals, silver and/or gold, to recover the metal therefrom, which method comprising receiving a bulk sample of the waste of unknown composition, dispersing the bulk sample in water to form a bulk sample dispersion, stirring the bulk sample dispersion in a mixing tank, continuously withdrawing from the bottom section of the tank a portion of the dispersion and recycling it via a recycle loop to the upper portion of the tank such that a substantially homogeneous dispersion is obtained in at least the recycle loop, taking a representative sample of the bulk sample dispersion from the recycle loop to yield a reduced volume

sample, assaying said reduced volume sample for the metal, calculating the content of the metal in the remaining bulk sample dispersion, and recovering the metal from the remaining bulk sample dispersion in a supercritical water oxidation process. If necessary, the reduced volume sample may be subsequently sub-divided and representative sub-division samples are assayed or analysed for key components in conventional manner.
Preferably, the supercritical water oxidation process is as described in WO 01/83834. For technical reasons, conventional refining techniques do not sample and assay the bulk sample, but only sample and assay after one or more preliminary concentration or refining steps. Accordingly, the present invention represents a significant departure from the state of tfie art, and is believed to offer advantages in speed of processing, and hence significantly reduce the cost of financing "work in progress".
The method of sampling according to the invention desirably uses a conical-ended stirred mixing tank, fitted with a pipe at the apex of the cone. Other tank shapes may, however, be used, for example a hemispherical, frusto -conical or similar section base. The recycle of dispersion is to the upper section of the tank, and may be made to any one or more points in said upper section. Conveniently, a single recycle point is approximately half-way along a radius of the tank.
Suitable mixing speeds, impeller shapes, recycle line diameters and recycle rates may vary according to the volume of the mixing tank and volume of the sample dispersion, and may be established by routine experiment. The aim is, of course, to ensure that the representative sample taken from the recycle loop is truly representative and this is essentially achieved by ensuring that the dispersion is homogenised.
Particularly preferred bulk sample feedstocks are spent catalysts, especially those comprising a platinum group metal carried on a carbon support. Such spent catalysts generally contain considerable quantities of organic solvent. However, since these are often regarded as wastes, they may be contaminated with a variety of organic (e.g. paper,

cloth etc.) or inorganic (e.g. nuts and bolts etc.) matter. Such contaminating matter is desirably screened out.
Suitable liquid or slurry samplers are commercially available for use in the recycle loop. The volume taken is not especially important.
The methods used for assay or further analysis are conventional and form no part of this invention.
Depending upon the nature of the bulk sample and especially the nature of solvents or residues associated with the values in the bulk sample, an additive to improve dispersion in the water may be required. Conventional and commercially available surfactants may be used if the bulk sample is essentially non-polar. Initial tests on bulk samples which have a polar character indicate that certain surfactants, e.g. "Quadralene"™ (used for glassware washing'machines) may be advantageously used.
Suitable concentrations of bulk sample in the water are from 10-15 wt%. Conveniently, the bulk sample, crushed or milled if necessary, is added, together with an appropriate surfactant, to the tank already charged with water, mixing is begun and the recycle initiated.
The present invention will now be described by way of example only and with reference to the accompanying drawings in which;
Figure 1 shows a schematic representation of apparatus for carrying out sampling according to the invention; and,
Figure 2 is a graph comparing metal values for a range of samples evaluated using the method of the present invention with those obtained using conventional pyrolysis.

With reference to Fig. 1, apparatus for carrying out the invention includes a mixing tank, 1. In proving trials, a steel tank of 600 litre capacity, with a conical bottom, has been used. A conventional axial impeller, 2, is fitted in tank 1, to mix the contents. A recycle line, 3, of 19 mm internal diameter is attached to the conical base of tank 1.
The recycle line is connected to a pump, 4, before being returned to the upper section of tank 1. The pump has been operated at 4400 l/hr. Fitted downstream of the pump is a commercial liquid/slurry sampler "Isolock"™ 5, which collects a sample volume of 500 ml.
The recycle line may include a line, 6, to allow the contents of the tank to be emptied or further processed.
The charge of bulk sample is conveniently received in a bulk container, 7, fitted with a pump, 8, for water, wash water and/or surfactant. The bulk sample is fed to a screen, 9, to remove gross contaminants; a screen size of 3-10 mm size is generally appropriate for spent carbon-based catalyst.
The sample is suitably passed to an assay laboratory, where it is resuspended and kept agitated. Sub-samples may be taken by using tube sampling. It is generally good practice to take a number of samples, some of which may be retained as a reference sample, to minimise the opportunity for process variability.
For example, where the bulk sample consists essentially of spent carbon-supported catalyst with organic solvent, it is preferred to oxidise all organic/carbonaceous material to CO2, using a mixture of sulphuric and nitric acids. The residual precious metal can then be dissolved in a pre-set volume of aqua regia and analysed, for example using Inductively Coupled Plasma Emission Spectroscopy against standard solutions of known platinum group metal content.

In order that the mvention may be more fully understood, an example showing the efficacy of the sampling step of the method of the invention is provided by way of illustration only, compared with a known pyrolysis sampling step.
EXAMPLE
Fifty-one catalyst samples were evaluated using the method of the invention. The samples were sourced from a wide range of used and unused materials with a range of physical properties and impurities. Results are shown in Table 1. Recovery is measured as the ratio (expressed as a percentage) between the amount of metal evaluated in each sample using the method of the invention and that evaluated by conventional pyrolysis. Excellent agreement was found between the two methods indicating that method of the invention provides an accurate and reliable measure of total metal content. The results of Table 1 are illustrated graphically in Fig. 2, with a line of unit gradient for reference.
Table 1.
(Table Removed)

WE CLAIM;
1. A method of refining a metal-containing waste, containing at least one metal selected from the group consisting of platinum group metals, silver and/or gold, to recover the metal therefrom, which method comprising receiving a bulk sample of the waste of unknown composition, dispersing the bulk sample in water to form a bulk sample dispersion, stirring the bulk sample dispersion in a mixing tank (1), continuously withdrawing from the bottom section of the tank a portion of the of the dispersion and recycling it via a recycle loop (3) to the upper portion of the tank such that a substantially homogeneous dispersion is obtained in at least the recycle loop, characterized by taking a representative sample of the bulk sample dispersion from the recycle loop to yield a reduced volume sample, assaying said reduced volume sample for the metal, calculating the content of the metal in the remaining bulk sample dispersion, and recovering the metal from the remaining bulk sample dispersion in a supercritical water oxidation process.
2. A method as claimed in claim 1, wherein the bulk sample is a spent catalyst.
3. A method as claimed in claim 2, wherein the spent catalyst is a platinum group metal on carbon catalyst.
4. A method as claimed in any one of the preceding claims, where a surfactant is added to the water or the sample to facilitate dispersion.
5. A method as claimed in any one of the preceding claims, wherein the sample is a solid having particle size of less than 500µm, preferable less than l00µm.

6. A method as claimed in any one of the preceding claims, wherein the concentration of the bulk sample in the liquid is between 10 and
15wt%.

Documents:

1108-delnp-2004-abstract.pdf

1108-delnp-2004-claims.pdf

1108-delnp-2004-complete specification (as files).pdf

1108-delnp-2004-complete specification (granted).pdf

1108-DELNP-2004-Correspondence Others-(12-10-2011).pdf

1108-delnp-2004-correspondence-others.pdf

1108-delnp-2004-correspondence-po.pdf

1108-delnp-2004-description (complete).pdf

1108-delnp-2004-drawings.pdf

1108-delnp-2004-form-1.pdf

1108-delnp-2004-form-13.pdf

1108-delnp-2004-form-19.pdf

1108-delnp-2004-form-2.pdf

1108-delnp-2004-form-3.pdf

1108-delnp-2004-form-4.pdf

1108-delnp-2004-form-5.pdf

1108-DELNP-2004-GPA-(12-10-2011).pdf

1108-delnp-2004-gpa.pdf

1108-delnp-2004-pct-210.pdf

1108-delnp-2004-pct-304.pdf

1108-delnp-2004-pct-409.pdf

1108-delnp-2004-pct-416.pdf

1108-delnp-2004-petition-137.pdf

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Patent Number

231869

Indian Patent Application Number

1108/DELNP/2004

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

12-Mar-2009

Date of Filing

26-Apr-2004

Name of Patentee

JOHNSON MATTHEY PUBLIC LIMITED COMPANY

Applicant Address

2-4 COCKSPUR STREET, TRAFALGAR SQUARE, LONDON SW1Y 5BQ, U.K.

Inventors:

#	Inventor's Name	Inventor's Address
1	PIERS SCOTT GRUMETT	JOHNSON MATTHEY, 8 AVENUE DE BALE, 1140 BRUSSELS, BELGIUM.
2	PETER WILLIAM ASH	8 ST BARTHOLOMEWS ROAD, READING RG1 3QA, U.K.
3	BRIAN HARRISON	NEW HOUSE CHURCH STREET, TEMPSFORD, SANDY, BEDFORDSHIRE SG19 2AN,U.K.

PCT International Classification Number

G01N 1/00

PCT International Application Number

PCT/GB02/04724

PCT International Filing date

2002-10-18

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0126346.6	2001-11-02	U.K.