TWI590873B - Cryo-smashing of waste pcb - Google Patents

Description

Low temperature pulverization of discarded printed circuit boards

The present invention relates to a method and apparatus for cryogenically pulverizing a waste printed circuit board (PCB).

Waste electrical and electronic equipment (WEEE) has grown throughout the world in recent decades. The recycling of WEEE is becoming more and more important not only from the perspective of environmental concerns but also from the perspective of recycling valuable materials.

Waste PCB recycling is an important part of the WEEE industry. In general, the recycling procedure consists of: 1) selective disassembly: removal of components attached to the PCB, such as capacitors; 2) upgrading and refining: using mechanical, chemical and/or metallurgical processes to upgrade the desired material content And then refined to recover the material returned to its life cycle; 3) the final disposal of the waste.

The comminution procedure is a relatively critical pretreatment prior to the mechanical or chemical refining step. The comminution procedure typically breaks the panel into small particles, for example, 1 x 1 mm or even smaller. A conventional procedure for disposal of PCBs is shown in FIG. In general, this procedure involves rough cutting a bare PCB to a size of 10 mm to 20 mm, cooling the cut PCB with liquid nitrogen and then performing a fine comminution.

Referring to Figure 2, a typical shredder is shown. To obtain a finer particle size, a liquid nitrogen nozzle is provided at the material inlet of the pulverizer. The plates are cooled and frozen before being loaded into the crushing chamber. Alternatively, another liquid nitrogen nozzle can be provided in the chamber to cool the cutter and load it. board.

There are many disadvantages in the prior art. For example, the cooling effect is not well controlled and the nitrogen consumption for cooling is typically extremely high. Additional removal steps are required to remove the components, which is not helpful. In addition, a rough cutting step is involved to cut the panel to an intermediate size for further fine comminution.

One of the objectives of the present invention is to solve the above problems and other problems in the prior art.

In one aspect, the present invention generally provides a method of cryogenically pulverizing a waste PCB, the method comprising: preheating the PCB; cooling the preheated PCB; and pulverizing the cooled PCB.

In another aspect, a device for cryogenically pulverizing a waste PCB is disclosed herein, the device comprising: a heater configured to preheat one or more PCBs; a cooler coupled to the heater And configured to cool the one or more pre-heated PCBs; a pulverizer coupled to the chiller and configured to smash the one or more cooled PCBs.

100‧‧‧Cryogenic crushing device

110‧‧‧heater

120‧‧‧cooler

130‧‧‧Smasher

200‧‧‧Cryogenic crushing device

210‧‧‧Preheating furnace

220‧‧‧Liquid nitrogen bath

230‧‧‧Crushing room/room

300‧‧‧Cryogenic crushing device

310‧‧‧ furnace

320‧‧‧Nozzle array / liquid nitrogen nozzle array

330‧‧‧Crushing room

BRIEF DESCRIPTION OF THE DRAWINGS The benefits, features, and advantages of the present invention will be better understood from the following description, in which: FIG. 1 illustrates a conventional comminution procedure in the prior art; FIG. 2 illustrates a typical prior art. FIG. 3 is a block diagram showing a low temperature pulverizing apparatus according to an embodiment of the present invention; FIG. 4 is a block diagram showing a low temperature pulverizing apparatus according to an embodiment of the present invention; and FIG. 5 illustrates a low temperature pulverizing apparatus using a liquid nitrogen bath. Embodiments; and Figure 6 illustrates another embodiment of a cryogenic comminution apparatus that uses liquid nitrogen spray.

3 is a block diagram showing a low temperature pulverization process in accordance with an embodiment of the present invention. As shown in the figure As shown in 3, the comminution procedure can include preheating the loaded waste PCB, cooling the preheated PCB, and pulverizing the cooled PCB to a desired size, such as less than 1 x 1 mm.

In an embodiment, the PCB can be preheated to a temperature between about 150 °C and about 200 °C. The pre-heating step can, for example, enhance the low temperature treatment effect and reduce the adhesion between the layers to facilitate the following procedure. Preheating can include electrical heating, thermal heating, and other heating techniques. The invention is not limited in this aspect.

As shown in Figure 3, the preheated PCB can be cooled to a desired temperature, such as between about -50 °C and -100 °C, and then pulverized into small sized particles. Cooling the preheated PCB may be implemented in various ways, including but not limited to use liquid nitrogen to cool and the liquid CO _2, such as a coolant or mechanical cooling.

The low temperature treatment after preheating can, for example, provide a strong thermal attack and thus embrittle the PCB. In particular, strong thermal shock can, for example, create a large amount of interlayer detachment, internal stress, and impart brittleness to the sheet, which helps to make the particle size after pulverization smaller. In some embodiments, the temperature gap between heating and cooling of the PCB can range from about 200 °C to 300 °C.

Additionally, in certain embodiments, the liquid electrolyte in the components on the PCB can be frozen to a temperature between, for example, about -5 ° C and about -55 ° C under cooling effects. Therefore, unlike the prior art, it is not necessary to remove components such as capacitors before pulverization. In addition, the procedure shown in Figure 3 removes the rough cutting steps of the PCB prior to comminution in the prior art. Thus, the comminution procedure disclosed herein can advantageously simplify prior art procedures.

4 is a block diagram illustrating a cryogenic comminution apparatus 100 in accordance with the present invention. As shown in FIG. 4, cryogenic comminution apparatus 100 can include a heater 110, a chiller 120 coupled to heater 110, and a pulverizer 130 coupled to chiller 120.

The heater 110 can be configured to preheat the waste PCB loaded to the heater 110. In certain embodiments, the PCB can be preheated to a temperature ranging from about 150 °C to about 200 °C, which can, for example, reduce adhesion between multiple layers. In various embodiments The heater 110 can include any type of heating device such as an electric heater, a heat heater, and the like. For example, heater 110 can be a nominal heating mesh belt furnace.

The preheated PCB can then be supplied from heater 110 to cooler 120. The chiller 120 can cool the pre-heated PCB to a desired temperature, such as between about -50 °C and -100 °C. In various embodiments, the cooler can be in any suitable form, such as a coolant bath, a coolant nozzle, a cooling compressor, and others. The coolant can be, but is not limited to, liquid nitrogen.

The cooled PCB can be delivered to a pulverizer 130 that comminutes the PCB into a suitable size, such as less than 1 x 1 mm. As mentioned above, the low temperature treatment after preheating can, for example, provide a strong thermal attack and embrittle the PCB, which is helpful for the finer particle size after comminution.

Figure 5 illustrates an embodiment of a cryogenic comminution apparatus 200 using a liquid nitrogen bath. As shown in FIG. 5, the waste PCB to be pulverized can be loaded into the preheating furnace 210. The pre-heated PCB can then be dropped into the liquid nitrogen bath 220 via, for example, a belt conveyor. Of course, other conveyors can be used instead. The PCB can then be immersed in liquid nitrogen by preheating the PCB. The temperature ramp rate of the PCB can range from about 40 ° C/min to 80 ° C/min or even higher. Strong thermal shock can make the PCB brittle. Then, the PCB cooled in the liquid nitrogen bath can be conveyed into the pulverization chamber 230, wherein the PCB is pulverized into particles having a small size such as less than 1 x 1 mm.

To further reduce the temperature, in certain embodiments, additional liquid nitrogen is provided in the comminution chamber 230 and controlled to be ejected therein, as shown in FIG. For example, in an embodiment, a thermal sensor is provided to monitor the temperature inside chamber 230 and then control the liquid nitrogen emission rate.

Figure 6 illustrates another embodiment of a cryogenic comminution apparatus 300 that uses liquid nitrogen spray. As shown, one or more PCBs can be delivered to the low temperature chamber after preheating in furnace 310. A nozzle array 320 is provided in the low temperature chamber to inject liquid nitrogen to the PCB. In one embodiment, the rate of liquid nitrogen injection is controlled. The temperature ramp rate of the PCB can range from about 40 ° C/min to 80 ° C/min or even higher. In this manner, each plate can be efficiently cooled to a desired temperature, such as between about -50 °C and -100 °C. Then, it can be dropped into the pulverization chamber 330 via the cooling plate.

In certain embodiments, cold nitrogen gas may flow into the comminution chamber 330 and/or additional liquid nitrogen may be controlled to be injected in the pulverization chamber 330 to further reduce the temperature if desired.

With the liquid nitrogen bath 220 of FIG. 5 or the liquid nitrogen nozzle array 320 of FIG. 6, the preheated PCB can be subjected to rapid and sufficient cooling to embrittle the PCB while the use of liquid nitrogen can be well controlled in an efficient manner. Therefore, overall nitrogen consumption can be significantly reduced compared to prior art.

Although specific embodiments have been illustrated and described in detail herein, it is understood that the invention The invention is intended to cover any and all variations or modifications of the embodiments. It is to be understood that the above description has been made by way of illustration and not limitation. Those skilled in the art, after reviewing the above description, will immediately understand the combinations of the above embodiments and other embodiments not specifically described herein. Therefore, those skilled in the art should understand that the disclosed concept and the specific embodiments can be used as a design or modification other without departing from the spirit and scope of the invention as defined by the following claims. The basis of the structure.

Claims (19)

A method of cryogenically pulverizing a waste printed circuit board (PCB), comprising: preheating the PCB; cooling the preheated PCB, wherein the preheated PCB means the PCB is still in a preheated state; and pulverizing the cooled PCB. The method of claim 1, wherein the preheating comprises preheating the PCB up to about 150 °C to 200 °C and/or the cooling comprises cooling the PCB to between about -50 °C and -100 °C. The method of claim 1, wherein the cooling comprises immersing the preheated PCB in liquid nitrogen. The method of claim 1, wherein the cooling comprises spraying liquid nitrogen to the preheated PCB. The method of claim 4, wherein the spraying the liquid nitrogen to the preheated PCB comprises spraying the liquid nitrogen to the plurality of preheated PCBs with a plurality of nozzles. The method of claim 3 or 4, wherein the cooling temperature ramp rate of the PCB is between about 40 ° C/min and 80 ° C/min. The method of claim 1, wherein the temperature gap between the preheating and cooling of the PCB is in a range from about 200 °C to 300 °C. The method of claim 1, wherein the cooling comprises freezing the liquid electrolyte in the assembly on the PCB to a temperature between about -5 ° C and about -55 ° C. The method of claim 1, wherein the pulverizing comprises placing the PCB into the pulverization chamber and controlling an injection rate at which liquid nitrogen is ejected in the pulverization chamber. The method of claim 1, wherein the pulverizing comprises pulverizing the PCB into particles having a size of less than 1 x 1 mm. A device for cryogenically pulverizing a waste printed circuit board (PCB), comprising: a heater configured to preheat one or more PCBs; a cooler coupled to the heater and configured to cool the one or more preheated PCBs, wherein the preheated PCB means The PCB is still in a preheated state; and a pulverizer coupled to the chiller and configured to smash the one or more cooled PCBs. The device of claim 11, wherein the heater is configured to preheat the one or more PCBs up to about 150 ° C to 200 ° C and/or the cooler is configured to cool the PCB to about -50 ° C To -100 ° C. The device of claim 11, wherein the cooler comprises a liquid nitrogen bath in which the one or more preheated PCBs are immersed. The device of claim 11, wherein the cooler comprises an array of nozzles for injecting liquid nitrogen to the one or more preheated PCBs. The device of claim 13 or 14, wherein the one or more PCBs have a cooling temperature ramp rate of between about 40 ° C/min and 80 ° C/min. The device of claim 11, wherein the temperature gap between the preheating and cooling of the one or more PCBs is in a range from about 200 °C to 300 °C. The device of claim 11, wherein the cooler is configured to freeze the liquid electrolyte in the assembly on the PCB to a temperature between about -5 ° C and about -55 ° C. The apparatus of claim 11, wherein the pulverizer comprises a pulverization chamber and a liquid nitrogen nozzle to control an injection rate of liquid nitrogen sprayed in the pulverization chamber when the PCB is placed in the pulverization chamber. The apparatus of claim 11, wherein the pulverizer is configured to pulverize the cooled PCB to a size of less than 1 x 1 mm.