Recycling method of waste tungsten filament

Abstract

The invention belongs to the technical field of waste tungsten filament recycling, and particularly relates to a waste tungsten filament recycling method. The recycling method of the waste tungsten filament comprises the following steps that the cleaned waste tungsten filament is subjected to electric explosion in a liquid carbon source, and mixed slurry is obtained; the liquid carbon source comprises an organic solvent which is in a liquid state at normal temperature and normal pressure; and carrying out solid-liquid separation on the mixed slurry, and carrying out carbonization treatment on the obtained solid by adopting a gaseous carbon source at normal temperature and normal pressure to obtain tungsten carbide-containing powder. According to the clean, efficient and environment-friendly waste tungsten filament recycling method, the cleaned waste tungsten filaments are placed in a liquid carbon source (which is a liquid organic solvent at normal temperature and normal pressure) for electric explosion, carbonization treatment is performed after solid-liquid separation, and tungsten carbide-containing powder can be obtained. The recycling method is short in process, simple and low in cost, and the purpose of industrially and rapidly recycling the waste tungsten filaments can be achieved. And moreover, no acid-base reagent is needed, so that the method is environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of waste tungsten wire recycling, and in particular relates to a method for recycling waste tungsten wire. Background Art

[0002] Diamond cutting wire (diamond wire for short) is a cutting tool with diamond micro-teeth, mainly used for silicon wafer processing. Compared with traditional mortar cutting technology, diamond wire cutting has fast cutting speed, high cutting efficiency, low silicon wafer loss rate, and is friendly to the ecological environment. Therefore, it has been widely used in the field of silicon wafer cutting in the photovoltaic industry. With the development of the photovoltaic industry, silicon wafers are developing towards thinner and larger sizes, which requires diamond wire to develop thinner. The limit of carbon steel diamond wire is about 35μm, while the strength of tungsten wire with the same wire diameter is 15% higher than that of carbon steel wire and its stability is better than that of carbon steel, which can effectively improve cutting efficiency. Below 35μm, the potential for tungsten wire thinning is better than that of carbon steel wire.

[0003] Tungsten wire diamond wire includes a nickel-plated layer and a tungsten wire mother wire. With the extensive use of tungsten wire diamond wire, the recovery of valuable elements in waste tungsten wire has become a new problem. At the same time, the finished product rate of tungsten wire diamond wire is about 50%, and the recycling of broken tungsten wire during processing has also become an urgent problem to be solved. At present, the recycling of waste tungsten wire is mainly aimed at used waste tungsten wire diamond wire. The main idea is to quickly recover the tungsten wire mother wire by separating the nickel-plated layer, such as using concentrated sulfuric acid and hydrogen peroxide acid leaching to separate the nickel on the surface of the tungsten wire to obtain the tungsten wire mother wire; or oxidizing and roasting the waste tungsten wire diamond wire, then alkali dissolving or ammonia dissolving, evaporating and crystallizing to obtain ammonium paratungstate. However, the current recovery methods all have the problem of long processes, and require the use of a large amount of acid (such as hydrochloric acid) and alkali (such as sodium hydroxide) reagents, which cause great pollution to the environment and harm to the human body. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for recycling waste tungsten wires. The method for recycling waste tungsten wires of the present invention is simple, does not require the use of acid and alkali reagents, and is environmentally friendly.

[0005] The present invention provides a method for recycling waste tungsten wire, comprising the following steps:

[0006] The cleaned waste tungsten wire is subjected to electric explosion in a liquid carbon source to obtain a mixed slurry; the liquid carbon source includes an organic solvent that is liquid at normal temperature and pressure;

[0007] The mixed slurry is subjected to solid-liquid separation, and the obtained solid is subjected to carbonization treatment using a gaseous carbon source at normal temperature and pressure to obtain tungsten carbide-containing powder.

[0008] Preferably, the voltage of the electric explosion is 15-40 kV.

[0009] Preferably, the organic solvent that is liquid at room temperature and pressure includes one or more of benzene, methanol, ethanol, ethylene glycol, acrylic acid, liquid paraffin and ether.

[0010] Preferably, the liquid carbon source further comprises water, and the volume ratio of the water to the liquid organic solvent at normal temperature and pressure is 5-10:90-95.

[0011] Preferably, the gaseous carbon source at normal temperature and pressure includes one or more of methane, ethane, propane, butane and carbon monoxide.

[0012] Preferably, the temperature of the carbonization treatment is 1100-1400° C., and the insulation time is 0.5-4 h.

[0013] Preferably, the waste tungsten wire includes one or more of a first tungsten wire, a second tungsten wire and a third tungsten wire, the wire diameter of the first tungsten wire is less than 50 μm, the wire diameter of the second tungsten wire is greater than or equal to 50 μm and less than 500 μm, and the wire diameter of the third tungsten wire is greater than or equal to 500 μm and less than 1000 μm.

[0014] Preferably, the waste tungsten wire includes tungsten wire broken during the preparation of tungsten diamond wire or waste tungsten diamond wire containing nickel coating.

[0015] Preferably, the cleaning includes water washing and organic solvent washing, and the organic solvent used in the organic solvent washing includes alcohol or acetone.

[0016] Preferably, the carbonization treatment further comprises: washing, drying and crushing the obtained solid; the particle size after crushing is 50 to 200 nm.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The invention provides a method for recycling waste tungsten wires, comprising the following steps: subjecting the cleaned waste tungsten wires to electric explosion in a liquid carbon source to obtain a mixed slurry; the liquid carbon source comprises an organic solvent which is liquid at normal temperature and pressure; subjecting the mixed slurry to solid-liquid separation, and subjecting the obtained solid to carbonization treatment using a gaseous carbon source at normal temperature and pressure to obtain tungsten carbide-containing powder.

[0019] The present invention provides a clean, efficient and environmentally friendly method for recycling waste tungsten wires. The present invention places the cleaned waste tungsten wires in a liquid carbon source (liquid organic solvent at normal temperature and pressure) for electric explosion, and then performs carbonization treatment after solid-liquid separation to obtain tungsten carbide powder (including tungsten carbide or tungsten carbide-nickel composite powder). The recycling method of the present invention has a short process, a simple method, and a low cost, and can achieve the purpose of industrially and rapidly recycling waste tungsten wires. Moreover, it does not require the use of acid and alkali reagents, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a process flow chart for preparing tungsten carbide powder in the embodiment;

[0022] Figure 2 Schematic diagram of the electric explosion device used in the embodiment;

[0023] Figure 3 The XRD spectra of nano tungsten carbide prepared in Example 1 and Comparative Examples 1 and 3. DETAILED DESCRIPTION

[0024] The present invention provides a method for recycling waste tungsten wire, comprising the following steps:

[0025] The cleaned waste tungsten wire is subjected to electric explosion in a liquid carbon source to obtain a mixed slurry; the liquid carbon source includes an organic solvent that is liquid at normal temperature and pressure;

[0026] The mixed slurry is subjected to solid-liquid separation, and the obtained solid is subjected to carbonization treatment using a gaseous carbon source at normal temperature and pressure to obtain tungsten carbide-containing powder.

[0027] In the present invention, unless otherwise specified, the materials and equipment used are commercially available products in the art.

[0028] The invention conducts electric explosion on the cleaned waste tungsten wire in a liquid carbon source to obtain a mixed slurry; the liquid carbon source comprises an organic solvent which is liquid at normal temperature and pressure.

[0029] In the present invention, the cleaning preferably includes water washing and organic solvent washing, and the organic solvent used in the organic solvent washing preferably includes alcohol or acetone; the cleaning method is preferably ultrasound, and the present invention has no special requirements for the conditions of the ultrasound. The purpose of the cleaning is to remove stains such as oil, dust, etc.

[0030] In the present invention, the waste tungsten wire preferably includes broken tungsten wire or nickel-plated waste tungsten diamond wire in the process of preparing tungsten diamond wire. Using the broken tungsten wire as the raw material, tungsten carbide (WC) powder can be obtained; using the nickel-plated waste tungsten diamond wire as the raw material, tungsten carbide-nickel (WC-Ni) composite powder can be obtained.

[0031] In the present invention, the waste tungsten wire preferably includes one or more of a first tungsten wire, a second tungsten wire and a third tungsten wire, the wire diameter of the first tungsten wire is less than 50 μm, the wire diameter of the second tungsten wire is greater than or equal to 50 μm and less than 500 μm, the wire diameter of the third tungsten wire is greater than or equal to 500 μm and less than 1000 μm, and the wire diameter of the first tungsten wire is preferably greater than or equal to 25 μm.

[0032] In the present invention, the organic solvent that is liquid at room temperature and pressure preferably includes one or more of benzene, methanol, ethanol, ethylene glycol, acrylic acid, liquid paraffin and ether, and specifically can be acrylic acid and ethanol, benzene and ethylene glycol, ethanol and liquid paraffin, or benzene and liquid paraffin, the volume ratio of acrylic acid and ethanol is preferably 25:70, the volume ratio of benzene and ethylene glycol is preferably 80:15, the volume ratio of ethanol and liquid paraffin is preferably 10:85, and the volume ratio of benzene to liquid paraffin is preferably 40:60. The organic solvent that is liquid at room temperature and pressure is a carbon source.

[0033] In the present invention, the liquid carbon source preferably also includes water, and the volume ratio of the water to the liquid organic solvent at room temperature and pressure is preferably 5-10:90-95, specifically 10:90 or 5:95.

[0034] The present invention uses a liquid organic solvent at room temperature and pressure as a carbon source for electric explosion. Compared with the process in a carbon-containing atmosphere (gaseous carbon source), the electric explosion efficiency is high, the powder collection rate is high, and the carbonization effect during the electric explosion is good; and there is no need to perform air washing and ventilation before each electric explosion, so the operation is simple.

[0035] In the present invention, the liquid carbon source is preferably reused, and the number of reuses is preferably 5 to 7 times. In the present invention, different waste tungsten wires can be electrically exploded in the same liquid carbon source, and the electrical explosion products are accumulated and then separated, without the need for electrical explosion and separation. The present invention uses a liquid carbon source for electrical explosion, which can avoid the rapid oxidation and spontaneous combustion of highly active and highly pyrophoric nanopowders produced by the electrical explosion.

[0036] In the present invention, the voltage of the electric explosion is preferably 15 to 40 kV, specifically 15 kV, 20 kV, 25 kV or 40 kV. During the electric explosion, the length of the cleaned waste tungsten wire is preferably 2 to 5 cm. During the electric explosion, a strong pulse current flows quickly through the waste tungsten wire, and the tungsten wire is instantly vaporized and exploded; the tungsten wire is crushed into powder by high energy, and the liquid carbon source carbonizes the powder to form tungsten carbide.

[0037] After obtaining the mixed slurry, the present invention performs solid-liquid separation on the mixed slurry, and carbonizes the obtained solid using a gaseous carbon source at normal temperature and pressure to obtain tungsten carbide-containing powder.

[0038] In the present invention, the solid-liquid separation also obtains a liquid, which can be reused as a recovered liquid carbon source. The present invention has no special requirements for the solid-liquid separation method, such as filtration.

[0039] In the present invention, the carbonization treatment preferably also includes: washing, drying and crushing the obtained solid; the washing agent is preferably anhydrous ethanol, the drying temperature is preferably 80°C, and the time is preferably 1 hour; the particle size after crushing is preferably 50-200nm, and the crushing is to crush large particles in the solid.

[0040] In the present invention, the gaseous carbon source at normal temperature and pressure preferably includes one or more of methane, ethane, propane, butane and carbon monoxide.

[0041] In the present invention, the temperature of the carbonization treatment is preferably 1100-1400°C, specifically 1100°C, 1200°C, 1300°C or 1400°C, and the holding time is preferably 0.5-4h, specifically 0.5h, 1h, 1.5h, 2h or 4h. The flow rate of the gaseous carbon source at room temperature and pressure is preferably 0.5-2L / min, specifically 0.5L / min, 1L / min, 1.5L / min or 2L / min, and the carbonization treatment is preferably carried out in a molybdenum wire furnace.

[0042] In the present invention, the tungsten carbide-containing powder includes tungsten carbide powder or tungsten carbide-nickel composite powder, and the particle size of the tungsten carbide powder or tungsten carbide-nickel composite powder is preferably independently 20 to 200 nm.

[0043] In order to further illustrate the present invention, the method for recycling waste tungsten wire provided by the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Follow the steps below Figure 1 The flow chart shown is used to prepare nano tungsten carbide powder or nano tungsten carbide-nickel composite powder. Figure 2 Schematic diagram of the electric explosion device used in the embodiment, wherein the electrodes are copper electrodes.

[0045] Example 1

[0046] Step 1: Use clean water and alcohol to ultrasonically clean the waste tungsten wire in turn to obtain the cleaned waste tungsten wire (clean tungsten wire), and select tungsten wire with a diameter of 25 to 50 μm.

[0047] Step 2: Preparation of liquid carbon source: Mix water and liquid paraffin in a volume ratio of 1:9 to obtain a liquid carbon source.

[0048] Step 3: Electric explosion step: Use an electric explosion device with a voltage of 15 kV to perform electric explosion on the clean tungsten wire in a liquid carbon source to obtain a mixed slurry.

[0049] Step 4: After the tungsten wire is electrically exploded in the liquid carbon source, the mixed slurry is filtered to obtain tungsten carbide filter residue, and the filtrate can be returned to step 2 to continue to be used as a liquid carbon source.

[0050] Step 5: The obtained tungsten carbide filter residue is washed with anhydrous ethanol, dried (80°C, 1h) and crushed, and then placed in a molybdenum wire furnace for carbonization treatment. Methane (flow rate 1L / min) is introduced into the process, the carbonization temperature is 1300°C, and the time is 2h, and finally nano tungsten carbide powder with a particle size of 20-50nm is obtained.

[0051] Example 2

[0052] Step 1: Use clean water and alcohol to ultrasonically clean the waste tungsten wire in turn to obtain clean tungsten wire, and select tungsten wire with a diameter of 50 to 500 μm.

[0053] Step 2: Preparation of liquid carbon source: Mix water, acrylic acid and ethanol in a volume ratio of 5:25:70 to obtain a liquid carbon source.

[0054] Step 3: Electric explosion step: Use an electric explosion device with a voltage of 20 kV to perform electric explosion on the clean tungsten wire in a liquid carbon source to obtain a mixed slurry.

[0055] Step 4: After the tungsten wire is electrically exploded in the liquid carbon source, the mixed slurry is filtered to obtain tungsten carbide filter residue, and the filtrate is returned to step 2 to continue to be used as a liquid carbon source.

[0056] Step 5: The obtained tungsten carbide filter residue is washed with anhydrous ethanol, dried (80°C, 1h) and crushed, and then placed in a molybdenum wire furnace for carbonization treatment. During this process, carbon monoxide (flow rate 1.5L / min) is introduced, the carbonization temperature is 1200°C, and the time is 1.5h, and finally nano tungsten carbide powder is obtained with a particle size of 30 to 180nm.

[0057] Example 3

[0058] Step 1: Use clean water and alcohol to ultrasonically clean the waste tungsten wire in turn to obtain clean tungsten wire, and select tungsten wire with a diameter of 500-1000μm.

[0059] Step 2: Preparation of liquid carbon source: Mix water, benzene and ethylene glycol in a volume ratio of 5:80:15 to obtain a liquid carbon source.

[0060] Step 3: Electric explosion step: Use an electric explosion device with a voltage of 40 kV to perform electric explosion on the clean tungsten wire in a liquid carbon source to obtain a mixed slurry.

[0061] Step 4: After the tungsten wire is electrically exploded in the liquid carbon source, the mixed slurry is filtered to obtain tungsten carbide filter residue, and the filtrate is returned to step 2 to continue to be used as a liquid carbon source.

[0062] Step 5: The obtained tungsten carbide filter residue is washed with anhydrous ethanol, dried (80°C, 1h) and crushed, and then placed in a molybdenum wire furnace for carbonization treatment. Butane (flow rate 0.5L / min) is introduced into this process, the carbonization temperature is 1300°C, the time is 1h, and finally nano tungsten carbide powder with a particle size of 50-150nm is obtained.

[0063] Example 4

[0064] Step 1: Use clean water and alcohol to ultrasonically clean the waste tungsten wire in turn to obtain clean tungsten wire, and select tungsten wire with a diameter of 50 to 500 μm.

[0065] Step 2: Preparation of liquid carbon source: Mix water, ethanol and liquid paraffin in a volume ratio of 5:10:85 to obtain a liquid carbon source.

[0066] Step 3: Electric explosion step: Use an electric explosion device with a voltage of 25 kV to perform electric explosion on the clean tungsten wire in a liquid carbon source to obtain a mixed slurry.

[0067] Step 4: After the tungsten wire is electrically exploded in the liquid carbon source, the mixed slurry is filtered to obtain tungsten carbide filter residue, and the filtrate is returned to step 2 to continue to be used as a liquid carbon source.

[0068] Step 5: The obtained tungsten carbide filter residue is washed with anhydrous ethanol, dried (80°C, 1h) and crushed, and then placed in a molybdenum wire furnace for carbonization treatment. Propane (flow rate 2L / min) is introduced into the process, the carbonization temperature is 1300°C, the time is 1h, and finally nano tungsten carbide powder is obtained with a particle size of 40 to 160nm.

[0069] Example 5

[0070] Step 1: Use clean water and alcohol to ultrasonically clean the used tungsten wire (containing nickel plating) to be recycled to obtain clean tungsten wire, and select tungsten wire with a diameter of 25 to 50 μm.

[0071] Step 2: Preparation of liquid carbon source: Mix benzene and liquid paraffin in a volume ratio of 40:60 to obtain a liquid carbon source.

[0072] Step 3: Electric explosion step: Use an electric explosion device with a voltage of 25 kV to perform electric explosion on the clean tungsten wire in a liquid carbon source to obtain a mixed slurry.

[0073] Step 4: After the tungsten wire is electrically exploded in the liquid carbon source, the mixed slurry is filtered to obtain a WC-Ni composite filter residue, and the filtrate is returned to step 2 to continue to be used as a liquid carbon source.

[0074] Step 5: The obtained WC-Ni composite filter residue is washed with anhydrous ethanol, dried (80°C, 1h) and crushed, and then placed in a molybdenum wire furnace for carbonization treatment. Propane (flow rate 2L / min) is introduced into the process, the carbonization temperature is 1300°C, and the time is 1h, and finally a nano WC-Ni composite powder with a particle size of 50 to 100nm is obtained.

[0075] Example 6

[0076] The difference from Example 2 is that the voltage is 15 kV and the particle size of the obtained nano tungsten carbide powder is 60-200 nm.

[0077] Example 7

[0078] The difference from Example 2 is that the voltage is 25 kV and the particle size of the obtained nano tungsten carbide powder is 20-120 nm.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that Comparative Example 1 does not undergo carbonization treatment in a molybdenum wire furnace.

[0081] Comparative Example 2

[0082] The difference from Example 2 is that the electric explosion is carried out in the gaseous carbon source methane, step 4 is not carried out, and the carbonization treatment is not carried out in the molybdenum wire furnace.

[0083] Comparative Example 3

[0084] The difference from Comparative Example 2 is that the obtained powder is carbonized in a molybdenum wire furnace, propane is introduced (flow rate 2 L / min), the carbonization temperature is 1300° C., and the time is 1 h.

[0085] Figure 3 The XRD patterns of nano tungsten carbide prepared in Example 1 and Comparative Examples 1 and 3. It can be seen that there is only a diffraction peak of WC in the XRD of Example 1, indicating that the carbonization is complete. The method of the present invention can efficiently recycle waste tungsten wire to obtain tungsten carbide powder. The diffraction peaks of W and W2C appear in Comparative Example 1, indicating that the tungsten wire cannot be completely carbonized to obtain tungsten carbide powder only by means of electric explosion, and secondary carbonization is required. In Comparative Example 3, electric explosion and secondary carbonization are carried out in a gaseous carbon source, but there is still insufficiently carbonized W2C in the product, indicating that it is better to carry out electric explosion carbonization in a liquid carbon source.

[0086] The tungsten carbide powder or tungsten carbide-nickel composite powder prepared by the present invention has nano-scale particles, and the recovery method of the present invention does not need to use reagents such as acid and alkali. The metal wire electric explosion method has the advantages of high energy utilization efficiency and controllable powder particle size. Tungsten carbide nanoparticles can be successfully prepared by one electric explosion, which is conducive to the preparation of batch metal nanoparticles. The present invention can control the particle size by controlling the voltage, and the powder product obtained by the present invention has a concentrated particle size distribution.

[0087] Although the above-mentioned embodiments have made a detailed description of the present invention, they are only some embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on the embodiments of the present invention without creative work, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for recycling waste tungsten wire, characterized in that: The following steps are involved: The cleaned waste tungsten wire is subjected to electric explosion in a liquid carbon source to obtain a mixed slurry; the liquid carbon source includes an organic solvent that is liquid at normal temperature and pressure; The mixed slurry is subjected to solid-liquid separation, and the obtained solid is subjected to carbonization treatment using a gaseous carbon source at normal temperature and pressure to obtain tungsten carbide-containing powder.

2. The recycling method according to claim 1, characterized in that: The voltage of the electric explosion is 15-40 kV.

3. The recycling method according to claim 1, characterized in that: The organic solvent that is liquid at normal temperature and pressure includes one or more of benzene, methanol, ethanol, ethylene glycol, acrylic acid, liquid paraffin and ether.

4. The recovery method according to claim 1 or 3, characterized in that: The liquid carbon source also includes water, and the volume ratio of the water to the liquid organic solvent at normal temperature and pressure is 5-10:90-95.

5. The recycling method according to claim 1, characterized in that: The gaseous carbon source at normal temperature and pressure includes one or more of methane, ethane, propane, butane and carbon monoxide.

6. The recycling method according to claim 1 or 5, characterized in that: The temperature of the carbonization treatment is 1100-1400° C., and the insulation time is 0.5-4 hours.

7. The recycling method according to claim 1, characterized in that: The waste tungsten wire includes one or more of a first tungsten wire, a second tungsten wire and a third tungsten wire, the wire diameter of the first tungsten wire is less than 50 μm, the wire diameter of the second tungsten wire is greater than or equal to 50 μm and less than 500 μm, and the wire diameter of the third tungsten wire is greater than or equal to 500 μm and less than 1000 μm.

8. The recycling method according to claim 1 or 7, characterized in that: The waste tungsten wire includes tungsten wire broken in the process of preparing tungsten wire diamond wire or waste tungsten wire diamond wire containing nickel coating.

9. The recycling method according to claim 1, characterized in that: The cleaning includes water washing and organic solvent washing, and the organic solvent used in the organic solvent washing includes alcohol or acetone.

10. The recycling method according to claim 1, characterized in that: Before the carbonization treatment, the method further comprises: washing, drying and crushing the obtained solid; the particle size after the crushing is 50 to 200 nm.

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