Solid material comminution or disintegration – Processes – With heating or cooling of material
Reexamination Certificate
1999-12-13
2002-01-08
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
With heating or cooling of material
C241S024130, C241SDIG014
Reexamination Certificate
active
06336601
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 discarded 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 composites and for separation of metal and resin components.
Moreover, the present invention pertains to technology for cleaning-up dry distillation gas from an apparatus used for heating and dry distillation of waste containing combustible organic material into 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, harmful substances, such as lead component originating in solder retained on the waste printed circuit boards are prevented from diffusing 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 discarded 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 in a low oxygen environment, 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 placed into a metal smelting furnace. Valuable metals, such as gold, are recovered and the resin material is used as a substitute for the reducing agent.
In those heat treatment methods 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 contains metals, the metals remain in the ash, which requires another appropriate treatment.
For printed circuit boards that retain a large amount of solder, a substantial amount of the lead component of the solder retained on the circuit boards can evaporate due to a high temperature in the combustion treatment. Thus, consideration is necessary for proper 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 valuable metals such as gold, is contained in the waste. In other cases of, for example, home appliances, where valuable metals other than copper are scarce, such a method, while technically still possible, has little economical incentive. Therefore, this method has not been generally adopted.
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 reduce its mass. The yielded carbide is used as land improvement stuff.
In the heating and dry distillation method, 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 of oxidization cleaning of the gas using an oxidizing catalyst.
In the prior art method of incineration of the gas in a flame combustion furnace, a simpler and rather compact apparatus can be used. However, since the composition and amount of the generated dry distillation gas is not constant, the method has a problem that perfect combustion is difficult to maintain, and that unburned components may easily escape.
On the contrary, in the method using an oxidizing catalyst as shown in
FIG. 19
, dry distillation gas carried out from dry distillation furnace
21
B by scavenging fan
22
B is introduced through scavenging pipe
23
B onto oxidizing catalyst
26
B. The temperature of the oxidizing catalyst
26
B is maintained by flame burner
25
B in 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 variations in the concentration of combustible substances in the dry distillation gas exhausted from dry distillation furnace
21
B,stable combustion in the flame burner
25
B can deteriorate. Furthermore, when the gas contains a large
Nakajima Keizo
Onishi Hiroshi
Suzuki Masa-aki
Terada Takahiko
Ueno Takayoshi
Ratner & Prestia
Rosenbaum Mark
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