Metallurgical apparatus – Having means for leaching and subsequently precipitating a...
Reexamination Certificate
2000-01-24
2001-09-18
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Having means for leaching and subsequently precipitating a...
C266S171000
Reexamination Certificate
active
06290897
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a silver recovery system and, more particularly, to a simplified system for recovering silver ions from photographic developing fluids without the use of a pump or other electronic devices.
BACKGROUND OF THE INVENTION
Photographic films including photographic paper typically comprise a base material coated with a light-sensitive emulsion containing various silver salts and silver halides. During the developing process, the films are placed in solutions that chemically react with the emulsion layer in order to develop an image. During this process, some of the silver salts and silver halides dissolve and become suspended within the solutions. For example, one type of film developing solution, called a fixer, is specifically used to dissolve out any silver halides that were not exposed when the picture or image was taken.
Commercial film developing machines process such a large number of batches of photographs each day that recovery of the silver from the used developing fluids becomes cost-effective, even necessary. Of course, silver is a precious metal and is valuable even in fairly small quantities, which presents a financial incentive. Moreover, recovery of silver from commercial film developing operations is regulated by the government as an anti-pollution measure. Certain environmental regulations require that the amount of silver remaining in waste developing fluid be less than or equal to 0.3 parts per million (ppm).
Many commercial film developing machines are single units operated from small retail businesses, such as groceries, drugstores or stationers. Even these single retail units must comply with the relatively stringent environmental regulations and thus must implement a silver recovery process. Unfortunately, the equipment needed for silver recovery is often fairly expensive, and relatively complex to maintain. Understandably, the small business owner is reluctant to make a capital expenditure in such silver recovery equipment, and make the time and effort to learn how to operate it. Therefore, a significant portion of the silver recovery systems are leased and serviced under contract, which can be economically burdensome.
Of course, silver recovery is a relatively mature technology, as exhibited in U.S. Pat. No. 3,840,217 to MacKay, U.S. Pat. No. 4,441,697 to Peterson, et al., U.S. Pat. No. 5,004,212 to Gutierrez, and U.S. Pat. No. 5,472,176 to Azzara. The process typically involves passing the used film developing solution through a container in which is placed a screen, mesh, or porous filler of a metal that is above silver in the electromotive force series. For example, steel wool or woven screen wire may be used for the filler. The resulting galvanic replacement action causes silver to be deposited within the container as the metal is dissolved. After a predetermined time, contents of the container are sent to and further processed at a refinery to recover the silver.
Silver recovery systems available on the market all utilize a variable speed pump to insure an optimum flow rate through a container in which the galvanic reaction occurs. For example, a system denoted the METS model E-100 sold by CPAC equipment division of Leicester, N.Y., includes a variable speed pump that receives fluid directly from the film processing unit, or from an intermediate reservoir. The fluid is pumped to the lower portion of a first silver recovery container where it rises through the silver recovery filler to exit from an upper portion thereof. The precision metering pump is provided so that the fluid passes through the silver recovery container at the proper flow rate for optimum silver recovery.
Despite the availability of commercial silver recovery systems, there is a need for a simpler, more economical system.
SUMMARY OF THE INVENTION
The present invention provides a distinct advantage over prior art silver recovery systems by providing a simple and reliable system that does not include a pump or any other electronic devices. Instead, the present invention relies on a series of containers connected together to define a flow path through which solution flows by gravity. The flow rate of the solution through the containers is regulated by a manual-type valve, preferably a pinch valve.
In accordance with a preferred embodiment of the present invention, a pumpless system for recovering silver ions from a solution comprises a reservoir container for holding a quantity of solution containing silver ions, the reservoir container having an outlet. A first processing container has an interior cavity sized to receive a silver recovery filler material and includes an inlet positioned below the level of the filler material, and an outlet positioned above the level of filler material. A conduit connects the reservoir container outlet to the processing container inlet, the processing container being positioned below the reservoir container to establish gravity flow through the conduit. A manual valve is positioned in the conduit and has variable positions for metering the flow of solution through the conduit. In a preferred embodiment, the conduit is flexible and the manual valve is a pinch clamp. In addition, the reservoir container and first processing container preferably comprise industrial-type buckets. A second processing container similar to the first processing container may be provided in series to receive fluid flow from the first processing container.
In preferred embodiment of the system, a waste container is provided to receive discharge from the last processing container. The silver recovery material may comprise a porous metal above silver in the electromotive force series. Desirably, the filler material is steel wool. An inlet manifold may be positioned to receive fluid flowing through the inlet of the first processing container, the inlet manifold being sized to support the porous metal above the inlet. The inlet manifold is desirably a tubular PVC pipe having a plurality of apertures therein, a clear inlet flow path to the processing container thus being insured. An outlet pipe may be provided in communication with the outlet of the first processing container. The outlet pipe desirably extends generally horizontally into the interior cavity the processing container and terminates in a downturned end to reduce the possibility of particulate matter clogging system.
In a further embodiment of the present invention, a method of recovering silver from a solution is provided. The method includes providing a reservoir container stacked above a processing container, and connecting an outlet of the reservoir container to inlet of the processing container disposed in a lower portion of the processing container. The processing container further includes an outlet disposed in an upper portion thereof, and a mass of porous metal above silver in the electromotive force series positioned therein between the inlet and the outlet. A manual-type valve regulates the flow of solution from the reservoir container to the processing container. The method includes opening the manual-type valve to allow solution to flow from the reservoir container to the processing container until solution flows from the outlet of the processing container, measuring the rate of solution flow from the outlet of the processing container, and adjusting the manual-type valve to vary the flow of solution from the reservoir container to processing container.
A further understanding of the nature and advantages of the invention will become apparent by reference to the remaining portions of the specification and drawings.
REFERENCES:
patent: 3630505 (1971-12-01), MacKay
patent: 3655175 (1972-04-01), Zeleny et al.
patent: 3692291 (1972-09-01), MacKay
patent: 3840217 (1974-10-01), MacKay
patent: 4441697 (1984-04-01), Peterson et al.
patent: 4457495 (1984-07-01), Eder et al.
patent: 4740244 (1988-04-01), Williams
patent: 4804452 (1989-02-01), Rhodes
patent: 5004212 (1991-04-01), Gutierrez
patent: 5472176 (1995-12-01), Azzara
patent: 5626816 (1997-05-01), Fournie
Cumberbatch Guy L.
Kastler Scott
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