Solid material comminution or disintegration – Processes – With classifying or separating of material
Reexamination Certificate
2001-01-19
2003-02-25
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
With classifying or separating of material
C241S030000, C241S016000
Reexamination Certificate
active
06523764
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for separating metallic material, such as copper foil, solder, and electronic parts, from waste printed circuit boards, which are recovered from used electrical products or are yielded in manufacturing processes as inferior products or scraps.
Further, the present invention relates to a dry distillation apparatus used for heating and dry distillation of metal-having resin composite and for separation of metal and resin components.
Moreover, the present invention pertains to technology of cleaning-up of dry distillation gas from an apparatus used for heating and dry distillation of waste containing combustible organic material to carbonate to reduce weight.
2. Related Art of the Invention
Land disposal in controlled-type landfill sites is presently a general approach to dispose waste printed circuit boards, for example, contained in used electrical products. Because the controlled-type landfill sites are equipped with isolation sheets surrounding the site, it is avoidable that harmful substances, such as lead component originating in solder retained on the waste printed circuit boards, diffuse into the environment even when such harmful components get dissolved in rainwater.
Nevertheless, in the case of potential damage in the isolation sheets, the harmful substances could diffuse into the environment. Therefore, it is still desired to remove the harmful components, such as solder, from the waste printed circuit boards to make them harmless before disposal. Furthermore, since the printed circuit boards and the electronic parts retained thereon contain valuable metals such as copper, it has been desired to efficiently recover and recycle them.
In addition, waste printed circuit boards are also being yielded as inferior products or scraps in manufacturing plants, and are presently treated as industrial waste for land disposal described above. It is also desired to efficiently recover and recycle the valuable metals, such as copper, contained in such waste printed circuit boards.
Reflecting such situation, a couple of methods for treating waste printed circuit boards have been proposed. For example, Japanese Laid-open Patent Application No. Hei 6-228667 discloses a method, wherein printed circuit boards retaining electronic parts are pulverized through a coarse and a fine pulverization processes. Then, the pulverized material is separated and recovered using specific gravity separation process into two components: a portion mainly containing metallic material such as copper, and the other portion mainly consists of resin and filler materials.
To pulverize the waste printed circuit boards as described therein, strong pulverizing force is necessary because of toughness of board portion of the waste printed circuit boards. However, the force strong enough to pulverize the printed circuit boards excessively pulverizes solder potion during the pulverization of the board resin component. The excessive pulverization causes a difficulty in the specific gravity separation process to separate the solder component from the board resin component.
Similarly, electronic parts are also excessively pulverized and become difficult to separate from the board resin component. As such, there has been a problem of low recovery efficiency of the metal component, such as solder and electronic parts.
Another prior art method for treating waste printed circuit boards is disclosed in Japanese Laid-open Patent Application No. Hei 8-139446. As described therein, electronic parts soldered on a printed circuit board are removed therefrom by applying an external force to the board while the solder is heated and re-melted.
In this method, however, the external force is exerted also onto the heated and re-melted solder, making the solder to splash into fine drops. This situation causes another difficulty in the recovery of solder. In addition, regarding the electronic parts that are assembled on circuit boards with lead wire's ends being bent, it is difficult to remove such electronic parts from the circuit boards with this method alone.
On the other hand, a number of heat treatment methods have been proposed for recycling resin material that is contained in used products or manufacturing waste. In one of the methods, the resin material is directly used as fuel in a combustion furnace, and then the heat of combustion of the resin is utilized as energy resource. In an alternative method, the resin material is heated at a high temperature at a low oxygen concentration, such as in nitrogen atmosphere, and the generated combustible gas is used as fuel. These methods are called thermal recycle.
In another alternative method, metal-having resin material, which includes printed circuit boards and metallic material such as wiring connectors, is supplied into a metal smelting furnace. Contained valuable metals, such as gold, are recovered while the resin material is used as substitute of reducing agent.
In those heat treatment methods for using the resin material as a direct fuel, the combustion can be perfect, and hence, its utilization can be efficient, only if the composition of the resin material for treatment is pure. Further, when the material is containing metals, the metals remain in the ash, which requires another appropriate treatment.
For the printed circuit boards that retain a large amount of solder, substantial amount of lead component of the solder retained on the circuit boards can evaporate out due to a high temperature at the combustion treatment. Thus, a consideration is necessary for exhaust gas treatment.
Furthermore, the method for separation of metal and non-metal components using a metal smelting furnace is economically efficient only when a large amount of such valuable metals as gold is contained in the waste. In other cases of, for example, home appliances, wherein valuable metals other than copper are scarcely contained, such method is technically still possible, but has no economical effectiveness. Therefore, it has been avoided to generally adopt this method.
Moreover, a number of methods have been proposed for waste reduction treatment of waste containing combustible organic material, such as garbage discharged from houses or feeding facilities, and offal from food processing plants. Other than incineration treatment and bio-fermentation treatment, there is a method by heating and dry distillation of the waste to carbonize to reduce its mass. The yielded carbide is used as land improvement stuff.
In the heating and dry distillation method, cleaning-up treatment of dry distillation gas is necessary. Prior art for this includes a method by introducing the gas into a flame combustion furnace to incinerate it at high temperature, and a method by means of oxidization cleaning of the gas using an oxidizing catalyst.
In the prior art method by incineration of the gas in a flame combustion furnace, a simpler and rather compact apparatus can be used. However, since composition and amount of the generated dry distillation gas is not constant, the method has a problem that perfect combustion is difficult to keep, and that unburned component is accordingly easy to escape.
On the contrary, in the method using oxidizing catalyst as shown in
FIG. 19
, dry distillation gas carried out from a dry distillation furnace
21
B by a scavenging fan
22
B is introduced through a scavenging pipe
23
B onto an oxidizing catalyst
26
B. The temperature of the oxidizing catalyst
26
B is kept by a flame burner
25
B equipped in a gas treatment chamber
24
B. A part of combustible component is oxidized by the flame in the vicinity of the flame burner
25
B, and the rest part is perfectly cleaned up by the oxidizing catalyst
26
B. As such, perfectly treated clean exhaust gas can be exhausted from an exhaust vent
27
B.
In this configuration, however, in the case of large variation in the concentration of combustible substances in the dry distillation gas exhausted from the dry distillation furnace
21
B, stable combust
Kawakami Tetsuji
Kawasaki Yoshitaka
Nakajima Keizo
Onishi Hiroshi
Suzuki Masa-aki
RatnerPrestia
Rosenbaum Mark
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