Apparatus and method for recovering precious metals, such as platinum, rhodium, gold, silver, etc., from contaminated cement

Abstract

Apparatus and method for recovering precious metals from contaminated cement, comprising, in order of process, a crusher, in which a cement-metal conglomerate is placed, a sieve, a dispenser, a first container, suitable for collecting the metal on the bottom through the action of a magnetic stirrer, an expander, a second container, a drainage tank, and a sieve. The present invention relates in particular to the recovery of precious metal from the batch of cement contaminated by precious metals, such as platinum, rhodium, gold, or silver. In the production of glass fibers for reinforcement, dies made of an alloy of precious metals, in particular platinum and rhodium, are used. These dies are supported by a special cement structure. During the months of production life of the die, part of the precious metal diffuses into the cement on account of the high temperatures. Given the value of the metals, it is economically advantageous to recover them from the supporting cement at each change of the die.

Claims

1. An apparatus for recovering precious metals from contaminated cement, comprising, in order of process: a crusher, in which a cement-metal conglomerate is placed, a first sieve, a dispenser, a first container, an expander, a second container, a drainage tank, and a second sieve, wherein the first container is suitable for collecting the metal on the bottom through the action of a magnetic stirrer and collecting cement-containing liquid on the upper part of said first container, wherein the expander is provided for transferring said cement-containing liquid, and wherein said expander comprises a tube having a diameter; said tube connecting said first container to said second container; a flow being ensured by a difference in head between said first container and said second container, determining a transfer speed.

2. The apparatus according to claim 1, wherein said crusher comprises a stirrer and metal balls for crushing said cement-metal conglomerate and forming a cement-metal powder.

3. The apparatus according to claim 2, wherein said first sieve receives said cement-metal powder, and separates said powder from pieces not completely crushed; said dispenser comprises a hopper suitable for collecting said filtered powder; said dispenser feeds, by means of an auger conveyor, said powder into said first container.

4. The apparatus according to claim 3, wherein said first container is provided with a level sensor whose signal controls the opening and closing of an on/off valve placed in a pipe at the inlet of said first container.

5. The apparatus according to claim 1, wherein said expander comprises an expander element positioned in the middle of the tube, and the diameter of said expander element is embodied so as not to allow entrainment of the metal but to allow passage of the cement into said second container.

6. The apparatus according to claim 5, wherein said second container comprises two sectors, divided by a wall which maintains a first sector of the two sectors at a predetermined level, to ensure said difference in head with said first container.

7. The apparatus according to claim 6, wherein said drainage tank, positioned below said second container, collects the wet cement; said second sieve allowing the water to pass and be drained off.

8. A method for recovering precious metals from contaminated cement by means of the apparatus according to claim 1, wherein a powder of the cement-metal conglomerate is mixed with water inside the first container by means of the magnetic stirrer, in which the metal deposits on the bottom of said first container and the cement-containing liquid is transferred to the second container for separating the cement from water.

9. The method according to claim 8, wherein the flow of said cement-containing liquid through said expander is ensured by the difference in head between said first container and said second container, determining the transfer speed configured so as to be sufficiently high to allow the entrainment of metal and cement.

10. The method according to claim 9, wherein said expander element slows said flow from said transfer speed to a speed determined by the diameter of said expander element so as not to allow entrainment of the metal, but sufficient to allow passage of the cement into said second container, said metal falling, sliding to the bottom of said first container.

11. The method according to claim 8, wherein the level of the cement-containing water is maintained, in a first sector of the second container, at a predetermined level to ensure the difference in head with said first container, the cement depositing on the bottom of said first sector, while a second sector of the second container has the function of draining off the water so that the level can be maintained.

12. The method according to claim 8, wherein the cement collected in said second container is dried and fed back into the circuit to improve the efficiency of said method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of this invention will be more apparent from an examination of the description of a preferred, though not exclusive, embodiment of the invention, illustrated by way of non-limiting example in the appended drawings, in which:

(2) FIG. 1 is a schematic view of the apparatus according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) With particular reference to the numerical symbols of the aforementioned FIGURE, the apparatus for recovering precious metals from contaminated cement, according to the invention, indicated as a whole with the reference number 1, comprises, in order of process, a crusher 2, in which a cement-metal conglomerate is placed, a sieve 3, a dispenser 4, a first container 5, suitable for collecting the metal on the bottom through the action of a magnetic stirrer 6, an expander 7, a second container 8, a drainage tank 9, and a sieve 10.

(4) In the crusher 2, the cement-metal conglomerate, where the metal in this case is platinum, is inserted in a stirrer, together with cemented balls, to be crushed and pulverized.

(5) The cement-platinum powder is passed through the sieve 3 to separate the powder from the pieces not completely crushed.

(6) The filtered powder is collected in the hopper of the dispenser 4 which, by means of an auger conveyor, feeds the powder into the first container 5.

(7) The cement-platinum powder and water are fed into the first container 5.

(8) The water is kept at a predetermined level by means of a level sensor whose signal controls the opening and closing of an on/off valve 51 located in a pipe 52 at the container inlet, for topping up the water.

(9) The water and the powder are mixed inside the first container 5 by the magnetic stirrer 6.

(10) Having a higher specific weight than the cement, the platinum begins to deposit on the bottom of the first container 5.

(11) The expander 7 comprises a tube having a diameter D1 which connects the first container 5 to the second container 8, consisting of a tank.

(12) The flow is ensured by the difference in head h between the first container 5 and the second container 8, which also determines the transfer speed V1.

(13) An expander element 71, positioned in the middle of the connecting tube, allows the flow speed to slow down to a value V2.

(14) The circuit is designed in such a way as to have a value of V1 high enough to allow entrainment of platinum and cement.

(15) The value of V2, determined by the diameter of the expander element 71, is such as not to allow entrainment of the platinum but sufficient to allow passage of the cement into the second container 8.

(16) The platinum then falls, sliding, to the bottom of the first container 5.

(17) The second container 8 is made up of two sectors, divided by a wall 81 which maintains the first sector 82 at a predetermined level, ensuring the difference in head with the first container 5.

(18) The cement settles on the bottom of the first sector 82 while the second sector 83 has the function of draining off the water so that the level can be maintained.

(19) The drainage tank 9, positioned below the second container 8, collects the wet cement.

(20) The sieve 10 allows the water to pass through and be drained off.

(21) The collected cement can optionally be dried and fed back into the circuit to improve the efficiency of the process.

(22) It has been seen in practice that the invention accomplishes the intended aim and objects.

(23) In fact, a plant has been provided that solves the technical problem of reducing the technological and logistical complexity of the prior the art in the recovery of precious metals.

(24) The system of the present invention is based on the idea of exploiting the difference in density of the cement and the precious metal immersed in a water tank.

(25) The batch is crushed in advance into fine particles and immersed in a water tank.

(26) Water and the lighter particles are evacuated by a siphon current, that enables segregation by difference of density.

(27) The precious metal is separated in the water tank.

(28) The system according to the present invention differs from the prior art, for example from WO99/47714A1, by the synergistic action of the devices, such as the dispenser, the magnetic stirrer and the expander, which are all used, not as alternatives or auxiliaries to one another.

(29) The system of the present invention offers several real technical advantages.

(30) An advantage of the present invention is constituted by the reduced time to recover the precious material, unlike the very long times of traditional chemical systems.

(31) The invention provides for the recovery to take place in the same factory where the cement is used for the production of glass fibers.

(32) Another important problem solved by the present invention is the transport of the material which, in the traditional systems, in addition to lengthening times, generates a series of logistical problems and costs which are instead eliminated by this invention, with the possibility of carrying out the process directly in the factory.

(33) Furthermore, the present invention allows the material to be recovered as an alloy and not in individual components, with the possibility of using the material again directly to make new dies.

(34) No use is required of acids or chemical components. The treatment is purely mechanical.

(35) The system of the present invention offers great simplicity of operation and also savings in energy and water consumption.

(36) The invention does not use chemicals and is therefore much less dangerous.

(37) Naturally the materials used, as well as the dimensions, may be adapted to meet any needs.