Patent Application
20050247162
The present invention relates to methods for recycling small electronic items such as cell phones, pagers, personal data assistants (PDA's), etc. More particularly, the present invention is directed to apparatus and methods for recovering valuable metals from small electronic items.
Electronic items such as computers, cell phones, pagers, personal data assistants (PDA's), handheld global positioning systems (GPS's), MP3 players, calculators, batteries, etc. are quickly becoming a significant source of electronic waste. As technology advances, consumers are replacing such electronic items with newer models and newer equipment more and more frequently. Due to a very small after-market demand for used electronic equipment, the quantity of these materials that is being thrown away in landfills has been increasing at an alarming rate. One current estimate is that there are over 100 million used cell phones in the United States alone with at least one manufacturer replacing 250,000 cell phones monthly.
The discarding of electronic equipment creates a two-fold problem. First, the electronic equipment often contains hazardous materials such as lead, cadmium, mercury, etc. that can be of concern when discarded in an improper fashion. The second problem is that the electronic equipment may also contain valuable metals such as gold, silver, etc. that are lost.
Small electronic items such as cell phones, pagers, personal data assistants (PDA's), etc. contain, in addition to plastics and other organic materials, a small amount of copper, lead, tin, gold, iron, aluminum, zinc, cadmium, etc. The more abundant valuable materials, including gold and silver would be worth recovering if there existed an efficient and economic process to perform such recovery.
One of the basic problems encountered when developing processes for the recovery of materials from the electronics industry has been the high cost associated with the dismantling of equipment. This is especially true for smaller handheld items such as cell phones, pagers, personal data assistants (PDA's), handheld global positioning systems (GPS's), MP3 players, calculators, and other personal computing devices. The small nature of these devices makes it difficult to provide good separation of the various components into useful materials for recycle.
There has been a great deal of discussion concerning the best manner to handle the recycle and reuse of electronic equipment. There are a number of programs that have been established for the collection of these items. Current programs include the dismantling of equipment into steel, copper, aluminum, plastic, circuit boards and power supplies. This can be a very time consuming and labor intensive process. The recovery of precious metals from the dismantled equipment is usually handled by sending material to smelters for processing.
The present invention provides for an apparatus and process for recycling small electronic items and for recovering valuable metals there from. Moreover, the invention provides an alternative for the recovery of valuable metals that are present in materials separated in dismantling operations and in some cases can replace the dismantling operation, or allow more automated methods to be used for material separation.
According to various features, characteristics and embodiments of the present invention which will become apparent as the description thereof proceeds, the present invention provides a method of recovering metals from electronic wastes which comprises:
The present invention further provides a method of recycling electronic wastes including cell phones, pagers, personal data assistants, handheld global positioning devices, MP3 players, and calculators, which method comprises:
The present invention further provides a liquid bath that comprises a mass of liquid iron and the metal components of a charge of electronic waste that was added to the mass of liquid iron and melted therein.
The present invention will be described with reference to the attached drawings which are given as non-limiting examples only, in which:
The present invention involves methods and apparatus for recovering valuable components from electronic waste. According different embodiments, the present invention limits or completely avoids manual separation of the components of electronic waste.
The invention makes use of an induction furnace that maintains a bath of liquid metal into which electronic waste such as cell phones, pagers, PDA's, etc. are fed. The liquid metal bath can be iron or any other suitable metal which can be maintained a sufficient temperature to process electronic waste as described below. The temperature of the liquid bath provides sufficient energy to melt, volatilize or destroy all of the components of the electronic equipment. Metal portions of the feed materials with high boiling points such as iron, copper, tin, lead, gold, silver, etc. will melt at the process operating temperature. These metals will then either dissolve in the iron bath, or be separated in layers due to differences in specific gravity.
Lighter metals such as zinc, cadmium, mercury, etc. and organic materials would volatilize and exit the furnace as gases. These gases could be either collected or processed through an afterburner. Since induction furnaces use electric current as their energy source, gases are not produced to provide the energy for the process, this results in lower volumes of gas to be treated. The lower gas volume will allow more alternatives to be evaluated for the treatment of the gases exiting the process.
According to one embodiment, the electronic waste items are fed directly into the liquid metal bath without any preprocessing. In such a process, organics, such as plastic cases or housings, keypads, display screens, gasket/seal elements, oils, etc. will either volatilize or be decomposed (then volatilized from the system) while volatile metal components will volatilize out and other metal components will be melted into the liquid metal bath where they can be removed from the bath or form separate liquid layers that are arranged by their densities.
When the organic materials are volatilized or decomposed in the induction furnace, the resulting exhaust is subjected to appropriate containment, including scrubbing, bag house collection, treatments, etc. to prevent environmental pollution.
According to another embodiment of the present invention the electronic waste items are subject to a preprocessing step that removes a percentage of the organic components. A suitable preprocessing step would involve sorting the organic components from the metal components. This can be done according to the present invention by subjecting the electronic waste items to a process of crushing, cutting and/or grinding to reduce the electronic items into smaller pieces and using air to blow off the lighter organic components or using a water bath to float off the lighter organic components. The use of air to blow off the lighter organic components could be used in conjunction with a conveyer system, a fluidized bed, a falling stream of the ground, cut and/or crushed electronic waste, or any other conventional physical separation apparatus.
The present invention will be discussed with reference to
In the embodiment of the invention depicted in
Components of the electronic waste which are easily oxidized such as calcium, silicon, magnesium, aluminum, etc. will form slag that floats on the top of the metal bath 2. This slag layer can be skimmed off using conventional techniques and subjected to further processing or disposal. Metals with higher densities such as gold, silver, lead, copper, etc. will form separate layers at the bottom of the furnace. Metals such as zinc, cadmium, mercury, etc. that are volatile at the operating temperature of the system will exit the furnace as a vapor and, if desired, can be collected using conventional techniques or otherwise contained for environmental purposes.
While the bath 2 in the induction furnace 1 is being heated it is subject to turbulent conditions owing to the effect of the high intensity induced currents that are typical in induction furnaces. This turbulence helps mix the electronic waste into the bath and helps even out the temperature in the bath.
After a period of time during which electronic waste have been fed into the induction furnace 1, the induction current used to heat the charge is turned off so that the turbulent conditions of the charge are minimized. As the charge settles, various liquid metal layers will become arranged according to their specific gravities or densities. Table 1 below lists the densities for various metals that can be recovered from electronic wastes and the melting points of the metals.
From Table 1 it can be seen that after turbulent conditions in the bath are reduced, the components will settle out by density. Several of the metals will form alloys with either the iron or copper in the metal bath. The iron with its alloys will typically float on top of the bath. The heavier alloys with the copper will form the lower layers of the bath.
It is to be understood that the separation of the various metal layers may not be complete so that all of the individual metals can be recovered in their pure form. However, the process of separation effected by the use of the liquid iron bath will allow sufficient separation of the individual metals or metal alloys which can, if necessary be subject to further purification using known techniques.
In
The process depicted schematically in
Following processing in the sizing apparatus 20, the electronic waste is subjected to a process that separates at least a portion of the organic components from the metal components. Such a process utilizes a physical separation apparatus 21 that can, for example, use an air stream(s) to blow away/off the lighter organic components or use a liquid such as water to float off the lighter organic components in a bath. The use of air to blow away/off the lighter organic components could be used in conjunction with a conveyer system, a fluidized bed, a falling stream of the ground, cut and/or crushed electronic waste. It is to be understood that the overall preprocessing can be performed by any other conventional physical separation apparatus(es).
In
Accordingly, there are fewer pollutants generated when the electronic waste enters the induction furnace 1. Of course, the exhaust from the induction furnace 1 has to be contained and subject to any necessary environmental cleaning/treatment using conventional apparatus and possible recovery of volatile metal vapors. Accordingly, a particulate separator 5 and a sock or bag filter 6 as depicted in
As in the process depicted in discussed in reference to
The liquid metal bath 2 in the induction furnace 1 is intended to serve primarily as a heat reservoir to carry out the separation process described above. The bath 2 can be replaced and/or replenished if it becomes contaminated with components that adversely effect the metals that are to be separated and collected. During the operation of the process a slag layer will form on the surface of the bath 2. The slag layer can be controlled using conventional methods. For example, the thickness of the slag layer can be controlled by the addition of suitable chemical slagging agents or by mechanically removing, e.g. skimming, the slag layer off the bath 2.
The system can be operated in a continuous or batch mode. In the continuous operation, feed material, i.e. electronic waste can be continuously added to the process with slag and metals being removed at various levels from the bath 2. If the process is operated in a batch manner, feed materials would be added until the furnace was full, then the slag and a portion of the liquid metal bath would be removed before additional feed material is added.
Although the present invention has been described with reference to particular means, materials and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and various changes and modifications can be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as described above and set forth in the attached claims.
