CN114715916B - A process and equipment for recycling nitrogen trifluoride electrolysis residue resources - Google Patents

Abstract

The invention discloses a process and equipment for recycling resources of electrolytic residues of nitrogen trifluoride, wherein the process comprises the steps of firstly crushing the electrolytic residues, then carrying out high-temperature anaerobic pyrolysis, reserving metal fluoride in a powdery form, changing most of ammonium bifluoride and hydrogen fluoride into steam, introducing the steam after pyrolysis into a condensing device, condensing condensate liquid into ammonium bifluoride, crystallizing the condensate liquid into hydrogen fluoride, and recycling to obtain ammonium bifluoride solid; introducing the non-condensable hydrogen fluoride gas into a container filled with calcium oxide to react to generate calcium fluoride; the metal fluoride residues after pyrolysis are completely defluorinated by high-temperature steam, the defluorinated steam is absorbed by ammonia water, and the defluorinated metal oxide powder is cooled and then recovered. The invention utilizes the phase change characteristics of the gas, solid and liquid of ammonium bifluoride, hydrogen fluoride and metal fluoride at different temperatures, and realizes the separation and clean production of ammonium bifluoride, hydrogen fluoride and metal oxide in the electrolytic residue of nitrogen trifluoride and the recycling of resources by combining with equipment.

Description

A process and equipment for recycling nitrogen trifluoride electrolysis residue resources

Technical Field

The invention relates to the technical field of recycling nitrogen trifluoride electrolysis residue, and in particular to a process and equipment for recycling nitrogen trifluoride electrolysis residue resources.

Background Art

High-purity nitrogen trifluoride gas is an excellent plasma etching gas in the microelectronics industry. It has excellent etching rate and selectivity for silicon and silicon oxide. Therefore, it occupies an important position in many industries such as integrated circuits and chip manufacturing. In industry, there are two ways to produce nitrogen trifluoride: one is to electrolyze anhydrous hydrogen fluoride to produce fluorine gas, and then react with molten ammonium bifluoride to produce nitrogen trifluoride; the other is to electrolyze a mixture of anhydrous hydrogen fluoride and molten ammonium bifluoride, which can directly produce nitrogen trifluoride in the electrolytic cell. The crude nitrogen trifluoride obtained by the above two processes contains a large amount of hydrogen fluoride, which needs to be removed in the subsequent purification process. However, the existing purification technology is to absorb it with solid alkali or alkali solution, and the subsequent treatment process is relatively complicated and easy to cause secondary pollution. Therefore, it is necessary to further explore and optimize the process equipment. In addition, there are hydrogen fluoride and ammonium fluoride, which are solid hazardous wastes and need to be treated as solid wastes, otherwise it will cause serious waste of materials and heavy metal pollution.

During the electrolytic preparation of nitrogen trifluoride, nickel gradually dissolves as the anode and is deposited at the bottom of the electrolytic cell in the form of nickel fluoride, complexes, etc., affecting the electrolysis efficiency. Therefore, the sediment in the electrolytic cell must be cleaned regularly to maintain the smooth progress of electrolysis. The cleaned sediment is the electrolytic waste slag. In fact, the content of ammonium bifluoride and hydrogen fluoride in the electrolytic residue is about 50-60%; the remaining solids are composed of 55-65% nickel fluoride, 25-35% iron fluoride, 8-12% copper fluoride and 2% impurities. The electrolytic cell needs to be thoroughly cleaned during disassembly, which produces a large amount of wastewater containing fluorine and ammonia nitrogen. Nickel, as a precious metal, has high economic value. If it is not recycled, it will cause waste and serious heavy metal pollution. The electrolytic waste slag carries a large amount of ammonium bifluoride, whose characteristic pollutants are fluorine and ammonia nitrogen. Fluorine is highly toxic, and ammonia nitrogen is also a serious pollutant. Fluorine and ammonia nitrogen are second-class pollutants. The maximum allowable emission concentration of fluoride is 6 mg/L, and ammonia nitrogen is 10 mg/L.

At present, the fluorine and ammonia nitrogen in the electrolytic waste slag of nitrogen trifluoride and the electrolytic cell cleaning wastewater are generally treated separately. There are mainly the following methods for treating the electrolytic waste slag of nitrogen trifluoride: one is to neutralize and precipitate the fluorine ions in the nickel-containing waste slag with lime, and then use a chemical method to treat the ammonium ions with ammonia nitrogen. This treatment method only performs harmless treatment and does not achieve the recycling of resources, resulting in a waste of resources and an increase in treatment costs; the other is to dissolve the electrolytic nickel-containing waste slag with water, and then separate the solid and liquid, so that the liquid becomes an ammonium fluoride aqueous solution and the solid becomes a nickel-containing waste slag. The solid slag needs to be further separated. This treatment method is more complicated, and the separated nickel-containing waste slag is a hazardous waste and still needs to be handled by a professional company. Another method is to use hydrofluoric acid to dissolve the nickel slag, add sulfuric acid to the electrolyte, and use electrolysis to recover metallic nickel. This treatment method consumes a lot of energy, and after adding sulfuric acid, other impurities will be introduced, resulting in an increase in subsequent treatment processes and costs.

Summary of the invention

In order to overcome the shortcomings of the prior art, one of the purposes of the present invention is to provide a process for recycling the resources of nitrogen trifluoride electrolysis residue. According to the gas-solid-liquid phase change characteristics of hydrogen fluoride and ammonium bifluoride, by controlling the appropriate temperature, ammonium bifluoride and hydrogen fluoride are evaporated from the nitrogen trifluoride electrolysis residue, and the resources are recycled through condensation and crystallization; the second purpose of the present invention is to provide a device for the process for recycling the resources of nitrogen trifluoride electrolysis residue, by separating ammonium bifluoride and hydrogen fluoride through a high-temperature oxygen-free pyrolysis device, then recovering ammonium hydrogen cyanide through condensation and crystallization, recovering hydrogen fluoride through a calcium oxide tank, defluorinating metal fluoride powder through a steam defluorination device, and obtaining metal oxide powder after cooling through a cooling device, thereby realizing resource recycling.

One of the purposes of the present invention is achieved by the following technical solution:

A process for recycling nitrogen trifluoride electrolysis residue resources comprises the following steps:

1) crushing the nitrogen trifluoride electrolysis residue;

2) feeding the crushed residue to a high-temperature oxygen-free pyrolysis device for high-temperature oxygen-free pyrolysis to obtain pyrolysis gas and powder; wherein the powder is metal fluoride powder;

3) The pyrolyzed gas is condensed to obtain condensate and non-condensable gas. The condensate is crystallized to obtain ammonium bifluoride. The non-condensable gas is passed into a container filled with calcium oxide to generate calcium fluoride. The reaction equation is: 2HF+Ca(OH) ₂ =CaF ₂ ↓+2H ₂ O.

4) The pyrolyzed metal fluoride powder is passed through high-temperature steam for defluorination. The defluorinated high-temperature steam is subjected to heat exchange treatment and then passed through a container filled with ammonia water to absorb fluorine gas; and the solid is cooled to obtain a metal oxide powder, wherein the metal oxide powder contains 70-80% nickel oxide, and the rest is iron oxide, copper oxide or other impurities.

Furthermore, in step 2), the temperature of high-temperature oxygen-free pyrolysis is 400-600°C, preferably 500°C, because metal corrosion is accelerated at high temperatures, 400-600°C can both meet the pyrolysis process and appropriately extend the corrosion resistance of the metal. The selection of 500°C can both completely pyrolyze ammonium bifluoride and hydrogen fluoride and appropriately reduce energy consumption.

Furthermore, in step 3), the condensation crystallization is water-cooled, and the water cooling is tap water at room temperature. The tap water is cooled by an air-cooled heat exchanger to achieve recycling.

Furthermore, in step 4), the temperature of the high temperature steam is 400-600°C, preferably 500°C.

Furthermore, in step 4), an excess of ammonia water is used to absorb the fluorine gas after heat exchange. Just enough ammonia water: 2NH ₃ +3F ₂ =N ₂ +6HFNH ₃ ; excess ammonia water: 8NH ₃ +3F ₂ =N ₂ +6NH ₄ FF ₂ ; excess ammonia water: NH ₃ +3F ₂ =NF ₃ +3HF. Excess ammonia water can completely reduce hydrogen fluoride.

The second object of the present invention is achieved by adopting the following technical solution:

A device for recycling nitrogen trifluoride electrolysis residue resources, the use method of the device is the same as the above-mentioned process for recycling nitrogen trifluoride electrolysis residue resources, the device comprises a crushing device, a feeding device, a high-temperature oxygen-free pyrolysis device, a condensing device, a crystallization device, a calcium oxide tank, a steam defluorination device, an ammonia water tank, a heat exchange device and a cooling device;

The discharge port of the pulverizing device is connected to the feed port of the feeding device, the discharge port of the feeding device is connected to the feed port of the high-temperature oxygen-free pyrolysis device, the gas outlet of the high-temperature oxygen-free pyrolysis device is connected to the gas inlet of the condensing device, the condensate outlet of the condensing device is connected to the condensate inlet of the crystallization device, and the non-condensable gas outlet of the condensing device is connected to the non-condensable gas inlet of the calcium oxide tank;

The discharge port of the high-temperature oxygen-free pyrolysis device is connected to the feed port of the steam defluorination device, and high-temperature steam flows inside the steam defluorination device; the steam outlet of the steam defluorination device is connected to the steam inlet of the heat exchange device, the air outlet of the heat exchange device is connected to the air inlet of the ammonia water tank, and the discharge port of the steam defluorination device is connected to the cooling device.

Furthermore, the feeding device includes a hopper, a material pipe and a screw feeder, and the hopper is connected to the screw feeder through a material pipe; the material pipe is provided with a level meter and a plurality of valves, and during the feeding stage, the valves are used to seal in sections to extract the air inside to prevent the gas in the high-temperature anaerobic pyrolysis device from being re-injected into the feeding device.

Furthermore, the high-temperature oxygen-free pyrolysis device is a molten salt heating furnace or an electric heating furnace.

Furthermore, the equipment also includes a vacuum pump, which is connected to the high-temperature oxygen-free pyrolysis device, so that the high-temperature oxygen-free pyrolysis device is in an oxygen-free vacuum state, reducing the mixing of oxygen during the pyrolysis process; the condensing device is a scraper condenser.

Furthermore, the equipment also includes a discharging device, which includes a water-cooled screw conveyor and a silo connected in sequence. The water-cooled screw conveyor is provided with a cooling water outlet, and the cooling water outlet and inlet of the water-cooled screw conveyor are cyclically connected to the cooling device.

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

(1) It is known that the main pollutants in the nitrogen trifluoride electrolysis residue are ammonium bifluoride, hydrogen fluoride and metal fluoride, the boiling point of ammonium bifluoride is 240°C, and the boiling point of hydrogen fluoride is 19.51°C. The process for recycling the nitrogen trifluoride electrolysis residue resources of the present invention is to first crush the electrolysis residue, and then perform high-temperature oxygen-free pyrolysis, most of the ammonium bifluoride and hydrogen fluoride are gasified into steam, and the metal fluoride is retained in powder form, the steam after pyrolysis is passed into a condensing device, and the condensate after condensation is ammonium bifluoride, and the non-condensable gas is hydrogen fluoride. After the condensate is crystallized, the ammonium bifluoride solid is recovered; the non-condensable hydrogen fluoride gas is passed into a container filled with calcium oxide to react and generate calcium fluoride; the metal fluoride powder after pyrolysis is completely defluorinated by high-temperature steam to obtain metal oxide powder; the defluorinated steam is absorbed by ammonia water after heat exchange treatment to avoid fluorine gas escaping and polluting the environment, and the defluorinated metal oxide powder is cooled and recovered. The invention utilizes the gas-solid-liquid phase change characteristics of ammonium bifluoride, hydrogen fluoride and metal fluoride at different temperatures to achieve separation and resource recovery of ammonium bifluoride, hydrogen fluoride and metal oxides in nitrogen trifluoride electrolysis residue. The main components of the obtained metal oxide powder are nickel oxide (80-85%), iron oxide and copper oxide, and a small amount of impurities (1-2%).

Compared with the prior art, the process of the present invention has the following advantages: first, no pollution; second, no other materials are added and no other materials are generated; third, no ammonia water or hydrofluoric acid is added, so the cost of the added materials and the energy consumption of the added materials in the evaporation and concentration process are not increased; fourth, it is cleaner and more thorough than the existing process, and the overall content of hydrogen fluoride and ammonium hydrogen fluoride contained in the metal fluoride powder after pyrolysis is 2-3%, while the content in the original process is more than 20%; fifth, the metal fluoride contains 50-60% nickel fluoride, which is oxidized to nickel oxide after steam defluorination, which is conducive to the purification of nickel oxide for recycling, thereby increasing the application value; sixth, it reduces labor.

(2) The equipment for recovering the resources of the nitrogen trifluoride electrolysis residue of the present invention comprises a crushing device, a feeding device, a high-temperature oxygen-free pyrolysis device, a condensing device, a crystallizing device, a calcium oxide tank, a steam defluorination device, a heat exchange device, an ammonia water tank and a cooling device; the electrolysis residue first passes through the crushing device and then is sent to the high-temperature oxygen-free pyrolysis device by the feeding device; the high-temperature oxygen-free pyrolysis device is used to gasify most of the ammonium bifluoride and hydrogen fluoride into steam, and the metal fluoride is retained in the form of powder; the condensing device is used to condense the steam to obtain a condensate (ammonium bifluoride) and a non-condensable gas (hydrogen fluoride); the crystallizing device is used to crystallize and recover the condensate to obtain ammonium bifluoride; the calcium oxide tank is used to react with the non-condensable gas (hydrogen fluoride) to obtain calcium fluoride; the steam defluorination device is used to defluorinate the metal fluoride in the metal fluoride powder after pyrolysis by steam heating to obtain a metal oxide powder; the heat exchange device is used to perform heat exchange with the high-temperature steam after defluorination to cool it; the ammonia water tank is used to absorb the fluorine gas in the defluorination steam after heat exchange; and the cooling device is used to cool the metal oxide powder after defluorination. The equipment of the present invention realizes resource recovery and clean production of ammonium bifluoride, hydrogen fluoride and metal oxides, resource recycling, reduces energy consumption and labor costs, and improves the recovery rate.

(3) The present invention does not require low-temperature concentration, evaporative crystallization (compressor condensation energy consumption), and both condensation and crystallization are cooled by water. The cooling device is cooled by tap water in the outer jacket of the water-cooled screw conveyor, which reduces energy consumption and labor by more than 50%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a device of Example 1;

FIG. 2 is a schematic diagram of the device of Examples 2 to 5.

In the figure: 1. hopper; 2. material pipe; 3. valve; 4. material level meter; 5. screw feeder; 6. high-temperature oxygen-free pyrolysis device; 7. star-shaped unloader; 8. steam defluorination device; 9. cooling device; 10. water-cooled screw conveyor; 11. silo; 12. cracking gas outlet pipe; 13. crystallization device; 14. condensation device; 15. vacuum pump; 16. calcium oxide tank; 17. condensate inlet; 18. condensate outlet; 19. condensate pump; 20. control cabinet; 21. heat exchange device.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

Ammonium bifluoride is an inorganic substance with the molecular formula NH ₄ HF ₂ . It is white or colorless transparent orthorhombic crystal. The commodity is in the form of flakes with a slightly sour taste. The relative density is 1.52, the melting point is 124.6℃, and the boiling point is 240℃.

Hydrogen fluoride is an inorganic acid with a chemical formula of HF, a density of 0.922 kg, a melting point of -83.37 ° C, and a boiling point of 19.51 ° C.

Example 1

A device for recycling nitrogen trifluoride electrolysis residue resources, as shown in FIG1 , the method of using the device is the same as the above-mentioned process for recycling nitrogen trifluoride electrolysis residue resources, the device includes a crushing device, a feeding device, a high-temperature oxygen-free pyrolysis device 6, a condensing device 14, a crystallization device 13, a calcium oxide tank 16, a steam defluorination device 8, an ammonia water tank, a heat exchange device 21 and a cooling device 9; the above devices are all controlled and operated by a control cabinet 20;

The discharge port of the pulverizing device is connected to the feed port of the feeding device, the discharge port of the feeding device is connected to the feed port of the high-temperature oxygen-free pyrolysis device 6, the gas outlet of the high-temperature oxygen-free pyrolysis device 6 is connected to the gas inlet of the condensing device 14 through the cracking gas outlet pipe 12, the condensate outlet 18 of the condensing device 14 is connected to the condensate inlet 17 of the crystallization device 13 through the condensate pump 19, and the non-condensable gas outlet of the condensing device 14 is connected to the non-condensable gas inlet of the calcium oxide tank 16 through the vacuum pump 15;

The discharge port of the high-temperature oxygen-free pyrolysis device 6 is connected to the feed port of the steam defluorination device 8 through a star-shaped discharger 7, and high-temperature steam flows inside the steam defluorination device 8; the steam outlet of the steam defluorination device 8 is connected to the steam inlet of the heat exchange device 21, the air outlet of the heat exchange device 21 is connected to the air inlet of the ammonia water tank, and the discharge port of the steam defluorination device 8 is connected to the cooling device 9.

The feeding device includes a hopper 1, a feed pipe 2 and a screw feeder 5. The hopper 1 is connected to the screw feeder 5 through the feed pipe 2. The feed pipe 2 is provided with a level meter 4 and a plurality of valves 3. During the feeding stage, the valves 3 are used to seal the pipe in sections to extract the air inside. The high-temperature oxygen-free pyrolysis device 6 is a molten salt heating furnace or an electric heating furnace. The inner tank of the heating furnace is respectively equipped with a pressure gauge, a safety valve, an air outlet pipe and a discharge pipe 2. The condensing device 14 is a scraper condenser.

A process for recycling nitrogen trifluoride electrolysis residue resources comprises the following steps:

1) crushing the nitrogen trifluoride electrolysis residue into particles less than 20 mm by a shredder;

2) The crushed residue is fed into a high-temperature oxygen-free pyrolysis device 6 through a feeding device, and high-temperature oxygen-free pyrolysis is performed at 500° C. to obtain pyrolysis gas and powder; wherein the powder is a metal fluoride powder, and condensation and crystallization are performed by water cooling, and the water cooling is normal temperature tap water, and the tap water is cooled by an air-cooled heat exchanger to achieve recycling;

3) The pyrolyzed gas is added to the condensation device 14, condensed to obtain condensate and non-condensable gas, the condensate enters the crystallization device 13 to obtain ammonium bifluoride, and the non-condensable gas is pumped into the calcium oxide tank 16 through the vacuum pump 15 to generate calcium fluoride;

4) The metal fluoride powder after pyrolysis is defluorinated by passing high-temperature steam at 400°C in a steam defluorination device 8, and the high-temperature steam after defluorination is passed into a heat exchange device 21 for heat exchange treatment, and then passed into an ammonia water tank to absorb fluorine gas; after the solid is cooled, a metal oxide powder is obtained, and the main component of the metal oxide is nickel oxide.

Example 2

A device for recycling nitrogen trifluoride electrolysis residue resources, as shown in FIG2 , the method of using the device is the same as the above-mentioned process for recycling nitrogen trifluoride electrolysis residue resources, the device includes a crushing device, a feeding device, a high-temperature oxygen-free pyrolysis device 6, a condensing device 14, a crystallization device 13, a calcium oxide tank 16, a steam defluorination device 8, an ammonia water tank, a cooling device 9, a heat exchange device 21 and a discharging device; the above devices are all controlled and operated by a control cabinet 20;

The discharge port of the pulverizing device is connected to the feed port of the feeding device, the discharge port of the feeding device is connected to the feed port of the high-temperature oxygen-free pyrolysis device 6, the gas outlet of the high-temperature oxygen-free pyrolysis device 6 is connected to the gas inlet of the condensing device 14 through the cracking gas outlet pipe 12, the condensate outlet 18 of the condensing device 14 is connected to the condensate inlet 17 of the crystallization device 13 through the condensate pump 19, and the non-condensable gas outlet of the condensing device 14 is connected to the non-condensable gas inlet of the calcium oxide tank 16 through the vacuum pump 15;

The discharge port of the high-temperature oxygen-free pyrolysis device 6 is connected to the feed port of the steam defluorination device 8 through a star-shaped discharger 7, and high-temperature steam flows inside the steam defluorination device 8; the steam outlet of the steam defluorination device 8 is connected to the steam inlet of the heat exchange device 21, the air outlet of the heat exchange device 21 is connected to the air inlet of the ammonia water tank, and the discharge port of the steam defluorination device 8 is connected to the cooling device 9; the discharge device includes a water-cooled screw conveyor 10 and a silo 11 connected in sequence, and the cooling water outlet and inlet of the water-cooled screw conveyor 10 are cyclically connected to the cooling device 9.

The feeding device includes a hopper 1, a feed pipe 2 and a screw feeder 5. The hopper 1 is connected to the screw feeder 5 through the feed pipe 2. The feed pipe 2 is provided with a level meter 4 and a plurality of valves 3. During the feeding stage, the valves 3 are used to seal the pipe in sections to extract the air inside. The high-temperature oxygen-free pyrolysis device 6 is a molten salt heating furnace or an electric heating furnace. The inner tank of the heating furnace is respectively equipped with a pressure gauge, a safety valve, an air outlet pipe and a discharge pipe 2. The condensing device 14 is a scraper condenser.

A process for recycling nitrogen trifluoride electrolysis residue resources comprises the following steps:

1) crushing the nitrogen trifluoride electrolysis residue into particles less than 20 mm by a shredder;

2) The crushed residue is fed into a high-temperature oxygen-free pyrolysis device 6 through a feeding device, and high-temperature oxygen-free pyrolysis is performed at 400° C. to obtain pyrolysis gas and powder; wherein the powder is a metal fluoride powder, and the condensation crystallization is water-cooled, and the water cooling is normal temperature tap water, and the tap water is cooled by an air-cooled heat exchanger to achieve recycling;

3) The pyrolyzed gas is added to the condensation device 14, condensed to obtain condensate and non-condensable gas, the condensate enters the crystallization device 13 to obtain ammonium bifluoride, and the non-condensable gas is pumped into the calcium oxide tank 16 through the vacuum pump 15 to generate calcium fluoride;

4) The pyrolyzed metal fluoride powder is defluorinated by passing high-temperature steam at 600° C. in a steam defluorination device 8, and the high-temperature steam after defluorination is passed into a heat exchange device 21 for heat exchange treatment, and then passed into an ammonia water tank to absorb fluorine gas; and after the solid is cooled, a metal oxide powder is obtained, and the main component of the metal oxide is nickel oxide;

5) The metal oxide powder is fed into a discharging device and then sent to a silo 11 for storage via a water-cooled screw conveyor 10 .

Example 3

The device of Example 3 is the same as that of Example 2, but the specific process is different.

The process for recycling nitrogen trifluoride electrolysis residue resources in this embodiment includes the following steps:

1) crushing the nitrogen trifluoride electrolysis residue into particles less than 20 mm by a shredder;

2) The crushed residue is fed into a high-temperature oxygen-free pyrolysis device 6 through a feeding device, and high-temperature oxygen-free pyrolysis is performed at 600° C. to obtain pyrolysis gas and powder; wherein the powder is a metal fluoride powder, and condensation and crystallization are performed by water cooling, and the water cooling is normal temperature tap water, and the tap water is cooled by an air-cooled heat exchanger to achieve recycling;

3) The pyrolyzed gas is added to the condensation device 14, condensed to obtain condensate and non-condensable gas, the condensate enters the crystallization device 13 to obtain ammonium bifluoride, and the non-condensable gas is pumped into the calcium oxide tank 16 through the vacuum pump 15 to generate calcium fluoride;

4) The pyrolyzed metal fluoride powder is defluorinated by passing high-temperature steam at 500° C. in a steam defluorination device 8, and the high-temperature steam after defluorination is passed into a heat exchange device 21 for heat exchange treatment, and then passed into an ammonia water tank to absorb fluorine gas; and after the solid is cooled, a metal oxide powder is obtained, and the main component of the metal oxide is nickel oxide;

5) The metal oxide powder is fed into a discharging device and then sent to a silo 11 for storage via a water-cooled screw conveyor 10 .

Performance and testing

The process and equipment of Examples 1 to 3 were used to treat nitrogen trifluoride electrolysis residue resources, and the contents of hydrogen fluoride and ammonium hydrogen fluoride in the metal fluoride powder and the mass ratio of nickel oxide in the metal oxide powder were detected, as shown in Table 1.

Table 1 The content of hydrogen fluoride and ammonium hydrogen fluoride in the metal oxide powders and the mass ratio of nickel oxide to nickel oxide in the metal oxide powders in each group

As can be seen from Table 1, the overall content of hydrogen fluoride and ammonium bifluoride in the metal fluoride powder after being treated by the equipment and process of Examples 1 to 3 is only between 1 and 2%, while the proportion of nickel oxide in the metal oxide powder is as high as 85%, thereby achieving the separation of metal fluoride from hydrogen fluoride and ammonium bifluoride. After subsequent operations, hydrogen fluoride, ammonium bifluoride and nickel oxide can be recovered, and the purity of nickel oxide can be improved.

The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims (9)

1. A process for recycling nitrogen trifluoride electrolysis residue resources, characterized in that it comprises the following steps: 1) crushing the nitrogen trifluoride electrolysis residue; 2) feeding the crushed residue to a high-temperature oxygen-free pyrolysis device for high-temperature oxygen-free pyrolysis to obtain pyrolysis gas and powder; wherein the powder is metal fluoride powder; 3) The pyrolyzed gas is condensed to obtain a condensate and non-condensable gas. The condensate is crystallized to obtain ammonium bifluoride. The non-condensable gas is passed into a container containing calcium oxide to generate calcium fluoride; 4) The metal fluoride powder after pyrolysis is passed through high-temperature steam for defluorination. The high-temperature steam after defluorination is subjected to heat exchange treatment and then passed through a container filled with ammonia water to absorb fluorine gas; and the solid is cooled to obtain a metal oxide powder. 2. The process for recycling nitrogen trifluoride electrolysis residue resources as claimed in claim 1, characterized in that in step 2), the temperature of high-temperature oxygen-free pyrolysis is 400-600°C. 3. The process for recycling nitrogen trifluoride electrolysis residue resources as claimed in claim 1, characterized in that in step 3), condensation and crystallization are both water-cooled, and the water cooling is tap water at room temperature. 4. The process for recycling nitrogen trifluoride electrolysis residue resources as claimed in claim 1, characterized in that in step 4), the temperature of the high-temperature steam is 400-600°C. 5. The process for recycling nitrogen trifluoride electrolysis residue resources as claimed in claim 1, characterized in that in step 4), an excess of ammonia water is used to absorb the fluorine gas. 6. A device for recycling nitrogen trifluoride electrolysis residue resources, characterized in that the method for using the device is the process for recycling nitrogen trifluoride electrolysis residue resources as described in any one of claims 1 to 5, and the device includes a crushing device, a feeding device, a high-temperature oxygen-free pyrolysis device, a condensing device, a crystallization device, a calcium oxide tank, a steam defluorination device, an ammonia water tank, a heat exchange device and a cooling device; The discharge port of the pulverizing device is connected to the feed port of the feeding device, the discharge port of the feeding device is connected to the feed port of the high-temperature oxygen-free pyrolysis device, the gas outlet of the high-temperature oxygen-free pyrolysis device is connected to the gas inlet of the condensing device, the condensate outlet of the condensing device is connected to the condensate inlet of the crystallization device, and the non-condensable gas outlet of the condensing device is connected to the non-condensable gas inlet of the calcium oxide tank; The discharge port of the high-temperature oxygen-free pyrolysis device is connected to the feed port of the steam defluorination device, and high-temperature steam flows inside the steam defluorination device; the steam outlet of the steam defluorination device is connected to the steam inlet of the heat exchange device, the air outlet of the heat exchange device is connected to the air inlet of the ammonia water tank, and the discharge port of the steam defluorination device is connected to the cooling device; The equipment also includes a vacuum pump, which is connected to the high-temperature oxygen-free pyrolysis device; and the condensing device is a scraper condenser. 7. The equipment for recycling nitrogen trifluoride electrolysis residue resources as described in claim 6 is characterized in that the feeding device includes a hopper, a feeding pipe and a screw feeder, and the hopper is connected to the screw feeder through a feeding pipe; the feeding pipe is provided with a level meter and a plurality of valves. 8. The equipment for recovering nitrogen trifluoride electrolysis residue resources as claimed in claim 6, characterized in that the high-temperature oxygen-free pyrolysis device is a molten salt heating furnace or an electric heating furnace. 9. The equipment for recovering nitrogen trifluoride electrolysis residue resources as described in claim 6 is characterized in that the equipment also includes a discharging device, which includes a water-cooled screw conveyor and a silo connected in sequence, and the water-cooled screw conveyor is provided with a cooling water outlet, and the cooling water outlet and inlet of the water-cooled screw conveyor are cyclically connected to the cooling device.