CN107419103B - A kind of recycling processing method of discarded varistor - Google Patents

Abstract

The invention discloses a method for recycling waste piezoresistors, and belongs to the technical field of resource utilization of electronic waste. The main points of the technical solution of the present invention are: a recycling treatment method for waste varistors, including solvent mixed flow to remove insulating paint, low-temperature liquid nitrogen freezing mechanical collision to remove nickel-iron alloy wire and solder, high-temperature scraping and reciprocating screening to recover silver crumbs and other steps. During the implementation of the present invention, there is no discharge of incineration pollutants, acid-containing wastewater, heavy metal ion-containing wastewater, and waste residues, and the entire process does not require fuel combustion to supply energy, which is more energy-saving and environmentally friendly, and the process refinement degree, comprehensive output value and input-output ratio Far higher than the traditional processing technology.

Description

A recycling method for waste varistors

technical field

The invention belongs to the technical field of resource utilization of electronic waste, and in particular relates to a method for resource recovery of waste varistors.

Background technique

A varistor is a resistive device with nonlinear volt-ampere characteristics. Its structure is usually silver-plated on both sides of a smooth high-temperature sintered ceramic substrate, and then copper-plated iron-nickel alloy wires are welded on both sides by electronic soldering tin, and then painted. Apply a layer of polymer insulating paint. Due to its good nonlinear volt-ampere characteristics, the varistor has no discharge gap. When the overvoltage is applied, the resistance drops sharply, and the overvoltage energy is released to achieve the protective effect.

Varistors are disposable consumables for power electronic components. Since their invention, they have been widely used in power supply systems, motor protection systems, automotive electronic systems, and lightning protection systems for power electronic products. The unqualified products and disassembled varistors weigh thousands of tons. Discarded varistors contain valuable precious metal silver, solder and nano-resistor materials for varistors, which have high recycling value.

For a long time, the recycling of such electronic components in my country has been called electronic waste disposal. Its industries are mainly concentrated in Chaoshan area of Guangdong, Xiangxi area of Hunan, Jiangsu and Zhejiang areas, etc., and its industrial characteristics are often small in scale and the education level of employees And small workshop factories with low technical level, extensive treatment process, high energy consumption, and serious pollution usually carry out the process flow shown in Figure 1 for the recovery of varistors.

There are many disadvantages in the above process: the method of incineration to remove insulating paint has long been banned by the environmental law enforcement department of our country, and a large number of incineration operations are illegal or even criminal; the removal of solder at high temperature is usually done by direct heating, baking or even burning and frying. This method is simple and extensive, the removal of solder is insufficient, and silver is also lost; silver pickling is carried out with waste nitric acid from the factory, and sodium chloride is used as the precipitant. The crude silver obtained is filtered through the plate frame and then burned to obtain Crude silver, this process will produce a certain amount of acid wastewater containing heavy metal ions, nitrogen oxides, hydrogen chloride, etc., which will endanger the health of operators and seriously pollute the surrounding environment. With the gradual improvement of my country's environmental laws and regulations and the continuous strengthening of law enforcement, the process of recovering raw materials from varistors needs further research and development and improvement.

Contents of the invention

The technical problem to be solved by the invention is to provide a recycling method for discarded varistors with simple process, low cost, environmental friendliness and high recovery rate.

In order to solve the above technical problems, the present invention adopts the following technical scheme, a method for recycling waste varistors, which is characterized in that the specific process is:

(1) Place the cleaned and dried piezoresistor in a stainless steel drum with a sealed outer cylinder and a mesh inner cylinder, and perform solvent reflux washing under rotation. The solvent is compounded from the following raw materials with the following weight ratio : N-methylpyrrolidone 30%-40%, propylene glycol methyl ether acetate or/and propylene glycol methyl ether butyrate 10%-20%, 120 ^# petroleum ether 20%-30% and methyl cyclohexyl ester 10% -20%, the solvent is heated to 160-200°C with circulating heat transfer oil for reflux, and the turned varistor is continuously cleaned by the reflux liquid and high-temperature steam, so that the surface insulating paint is continuously washed and flowed down for recycling;

(2) Add the piezoresistor and liquid nitrogen after removing the surface paint into the double-layer closed horizontal mixing drum. At this time, the part of the tin in the solder that is in contact with the alloy iron bar becomes brittle due to the change of crystal shape under ultra-low temperature conditions, and the stirring drum is started to stir , the brittle solder bonding effect deteriorates and is constantly torn and knocked off. When the mechanical stirring makes the temperature of the material rise, the temperature is lowered by adding liquid nitrogen until the solder falls off completely, and then the nickel-iron alloy is recovered by magnetic separation. The solder slag is recovered by vibration screening and remelted for recovery;

(3) Place the piezoresistor after removing the solder in a reciprocating vibrating screen with an infrared heating tube on the top. Semicircular protrusions are evenly distributed on the sieve plate, and the piezoresistor is heated to 800-900°C by an infrared heating tube. Under the reciprocating horizontal vibration of the vibrating screen, the surface of the piezoresistor substrate and the horizontal rough surface of the sieve plate are constantly rubbed , and under the action of the semicircular bulge, the piezoresistor is automatically turned over, and the silver plating softened by heat falls off and hits into silver scraps to be screened and recycled, and the silver scraps are melted and smelted to obtain coarse silver ingots.

Compared with the prior art, the present invention has the following beneficial effects:

1. During the implementation of the present invention, there is no discharge of incineration pollutants, acid-containing wastewater, heavy metal ion-containing wastewater and waste residues, and the whole process does not require fuel combustion for energy supply, which is more energy-saving and environmentally friendly compared with traditional methods;

2. The processing method selected in this plan is to classify and recycle based on the analysis of the properties of the various parts of the varistor. The selected method hardly changes the properties of the raw materials, and the recycled raw materials do not change the chemical properties of the original raw materials. The processing method is scientific , which embodies the idea of recycling and reusing renewable resources;

3. The treatment method adopted by the present invention has a high degree of mechanization, and the equipment used can be designed and manufactured by using general materials in the market according to the needs, and the operation consumes less manpower, and does not have high professional requirements for operators, and is suitable for enterprises of various scales;

4. The recovery of silver in the present invention, because it does not go through the process of pickling and re-precipitation, has a high recovery rate, and the weight of the solder slag obtained by freezing and separation is much higher than that of silver. It can be recovered after only re-melting, and can be directly used as ordinary solder or even re-soldered. Used as a special solder for resistors, the economic value is objective. The polymer paint slurry can be reused as a new material through appropriate compounding and adjustment, or used as a compounding of other insulating coatings, and can also create a certain profit. Its degree of refinement and comprehensiveness The output value and input-output ratio are far higher than the traditional treatment process.

Description of drawings

Figure 1 is a flow chart of the traditional treatment process for waste varistors;

Fig. 2 is a flow chart of the recycling process of waste varistors according to the present invention.

Detailed ways

The above-mentioned contents of the present invention are described in further detail below through the embodiments, but this should not be interpreted as the scope of the above-mentioned themes of the present invention being limited to the following embodiments, and all technologies realized based on the above-mentioned contents of the present invention all belong to the scope of the present invention.

Example

After washing and drying 200Kg of recycled material with skin, use 300Kg of mixed solvent for reflux washing. The proportion of mixed solvent is as follows: N-methylpyrrolidone 120Kg, propylene glycol methyl ether butyrate 50Kg, methyl cyclohexyl ester 50Kg and 120 ^#petroleum ether 80Kg, heat the mixed solvent in an oil bath to 160°C and reflux until the recycled material completely turns into glue, filter the glue while it is hot, grind it in a sand mill after cooling, adjust the solid content to 40%, and seal it for storage for later use , the weight of the obtained material after washing off the insulating paint skin is 147Kg, and enters the next step of the process;

Add 147Kg of insulating paint leather material to the double-layer closed horizontal mixing drum with a safety release valve, then add 6Kg of liquid nitrogen, close the horizontal mixing drum and let it stand for 20 minutes, then stir for 60 minutes, then add 3Kg of liquid nitrogen, and close the stirring After 40 minutes, add 3Kg of liquid nitrogen, close and stir for 1 hour to discharge the material, screen out the tin slag through a vibrating sieve and collect it, separate the nickel-iron alloy wire through magnetic separation, and obtain 2.26Kg of solder and 23.74Kg of nickel-iron alloy wire by weighing, and the rest The remaining 121.2Kg;

Place the piezoresistor after removing the solder in a reciprocating vibrating screen with an infrared heating tube on the top. There are evenly distributed semicircular protrusions. Turn on the reciprocating vibrating screen to heat up the infrared heating tube and start reciprocating motion at the same time. The temperature of the sieve plate is controlled at 800 °C, and the material temperature is about 870 °C. After sieving for 80 minutes, the silver skin turns into silver flakes Completely removed and sieved, the sieved silver shavings were collected and re-cast to obtain 876g of coarse silver ingots with a purity of 91.4%, and the remaining 120Kg of the resistance substrate material.

The above embodiments have described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What are described in the above embodiments and description are only to illustrate the principles of the present invention. Without departing from the scope of the principle of the present invention, there will be various changes and improvements in the present invention, and these changes and improvements all fall within the protection scope of the present invention.

Claims (2)

1. a kind of recycling processing method of discarded varistor, it is characterised in that detailed process is：

（1）Varistor after washes clean and drying is placed in outer barrel sealing and stainless steel drum of the inner cylinder with mesh, rotation Turn to carry out solvent refluxing washing under state, the raw material which is matched by following weight percent compounds：N- crassitudes Ketone 30%-40%, propylene glycol methyl ether acetate or/and propylene glycol monomethyl ether butyrate 10%-20%, 120^#Petroleum ether 20%-30% and first Base cyclohexyl 10%-20%, solvent are heated to 160-200 DEG C using circulating heat conduction oil and flow back, and pass through withdrawing fluid and high temperature Steam persistently cleans the varistor stirred so that surface insulation coat of paint, which is constantly washed to gutter down, is able to recycling profit With；

（2）Varistor and liquid nitrogen after removal surface coat of paint are added in double-layer seal Horizontal stirring roller, at this time in scolding tin With dilval silk contact portion tin because under condition of ultralow temperature crystalline form become fragile, start mixing drum and be stirred, become fragile Scolding tin adhesive effect variation is constantly torn and shock falls off, when mechanical agitation so that by adding liquid nitrogen when temperature of charge increases Mode cool down again until scolding tin is completely fallen off, then recycle dilval silk by way of magnetic separation separation, then pass through oscillation The mode of screening recycles scolding tin slag and re-melts and recycled；

（3）Varistor after removal scolding tin is placed in top to be equipped in the reciprocating vibration sieve of infrared heating pipe, this is reciprocating The sieve plate of vibrating screen and the contact surface of varistor are hard abrasive material matte, are evenly distributed on sieve plate semicircle convex It rises, varistor is heated to 800-900 DEG C by infrared heating pipe, the pressure-sensitive electricity under vibrating screen reciprocal horizontal effect of vibration Resistance substrate surface constantly rubs with the horizontal matte of sieve plate, and varistor automatic turning under the action of semi-cylindrical hill Face, it is heated soften it is silver-plated fall off and hit into silver bits sieve, recycle, silver, which is considered to be worth doing, melt freshening and obtains thick silver ingot.

2. the recycling processing method of discarded varistor according to claim 1, it is characterised in that：Step（1）In Solvent is compounded by the raw material of following weight：N-Methyl pyrrolidone 120Kg, propylene glycol monomethyl ether butyrate 50Kg, methyl ring Own ester 50Kg and 120^#Petroleum ether 80Kg.