Method for recycling valuable metals from laterite-nickel ore and regenerating acid
Technical Field
The invention belongs to the cross field of metallurgy and chemical industry, and particularly relates to a method for recovering valuable metals from laterite-nickel ore and recycling acid in the process.
Background
Nickel is an important strategic reserve metal for national production and development, plays an important role in the fields of national defense, aerospace, transportation, petrochemical industry, energy sources and the like, and is also an important raw material for producing stainless steel, high-temperature alloy, high-performance special alloy, magnetic material and electromagnetic shielding material. Most of nickel ores exist in the laterite-nickel ores in the world, but the laterite-nickel ores have low grade and low smelting efficiency. Generally speaking, the pyrometallurgical process is more suitable for treating ores with higher nickel content, such as nickel sulfide ores and the like; the wet process is more suitable for treating minerals with lower nickel content, such as limonite type laterite-nickel ore and the like. With the decreasing of nickel sulfide ores and the shortage of high-grade laterite-nickel ores, limonite type laterite-nickel ores gradually enter the visual field of people, and the wet treatment process is also widely concerned and researched.
The wet treatment process mainly comprises a reduction roasting-ammonia leaching method and a pressure acid leaching method. The main advantage of the reduction roasting-ammonia leaching method is that the reagent can be used repeatedly, but the whole process has high energy consumption and high cost. The high-pressure acid leaching method is classified into a sulfuric acid pressure leaching method, a hydrochloric acid pressure leaching method, and a nitric acid pressure leaching method according to the acid used in the treatment process. The sulfuric acid high pressure leaching method is a mainstream wet process for treating the laterite-nickel ore at present, but the process has the problem of high sulfur content, so that the difficulty of comprehensively recovering valuable metals is high. The high-pressure hydrochloric acid leaching method has high requirements on equipment, is still in a laboratory exploration stage at present, and has a certain distance from the realization of industrial production. The advantage of the nitric acid pressure leaching method is that the leaching residue has low sulfur content, can be comprehensively recycled, has lower leaching temperature and lower pressure, but the popularization of the process is limited because the nitric acid is expensive. In addition, magnesium oxide is used as a precipitator in the nitric acid leaching process, so that the nickel and cobalt are seriously mixed due to the generation of aluminum hydroxide flocculent precipitates in the aluminum precipitation process, the loss amount of the nickel and cobalt respectively reaches about 5 percent, and the economic benefit is obviously reduced.
Chinese patent CN108950205B discloses a method for homogeneous precipitation and separation of iron and aluminum from a lateritic nickel ore pickle liquor, which adopts alkaline substance calcium carbonate and magnesium carbonate to grind and mix with water uniformly, then adds the mixture and the pickle liquor into a stirring tank by controlling the flow rate, and then precipitates aluminum iron slag homogeneously by adjusting the pH value of the solution. Although the method can improve the filtering performance of the precipitate to a certain extent, the content of nickel-cobalt metal carried in the precipitate is about 1-2%, which causes the recovery loss of nickel-cobalt metal.
Disclosure of Invention
The invention discloses a method for recovering valuable metals from laterite-nickel ore and recycling acid, aiming at the problems of high cost, immature process, high comprehensive recovery difficulty of valuable metals, serious nickel and cobalt inclusion and the like in a laterite-nickel ore wet treatment process in the prior art. Firstly, crushing and finely grinding laterite-nickel ore raw ore to obtain mineral powder, and then preparing the mineral powder into slurry to carry out nitric acid high-pressure leaching; carrying out solid-liquid separation on the obtained leaching pulp by a thickener to obtain leaching slag and leaching liquid, filtering and drying the leaching slag to obtain iron ore concentrate, evaporating and concentrating the leaching liquid, cooling the nitric acid volatilized in the concentration process to obtain condensed nitric acid, and then introducing the condensed nitric acid into a subsequent nitric acid regeneration system; pumping the concentrated solution into a reaction kettle for reduction to obtain nickel-cobalt mixed powder, and drying the nickel-cobalt mixed powder to be sold as a commodity; the nickel-cobalt separated liquid is decomposed at high temperature in a decomposing furnace to obtain mixed metal oxide powder and NO x Water vapor, O 2 The dust gas is cooled and then is processed by a dust collecting system to obtain the product containing Fe 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 MgO mixed powder can be sold as a commodity and can also be deeply processed; part of NO after dust collection x The gas is heated by the combustion furnace and then enters the decomposition system again, and the other part of NO x Cooling the gas, and flowing the gas to a nitric acid regeneration system; the gas entering the nitric acid regeneration system is subjected to tail gas heat exchange, deep dust removal and secondary cooling condensation to obtain condensed dilute nitrateAn acid; pressurizing and thickening the subsequent gas by a nitrogen oxide compressor, and allowing the subsequent gas to enter an absorption tower; the condensed acid obtained by the previous condensation is pumped to a corresponding tower plate of a nitric acid absorption tower for nitric acid preparation after the concentration is measured, and the industrial nitric acid generated by a nitric acid regeneration system is used for the front-end leaching process. The process is efficient and simple, and the problem that nickel-cobalt metal is carried in aluminum slag due to generation of aluminum hydroxide flocculent precipitate in the process of nickel-cobalt separation after alkaline substances are added into the nitric acid leaching solution of the laterite-nickel ore in the traditional process is solved, so that the total recovery rate of the nickel-cobalt metal is improved. Decomposing and regenerating the reduced solution to obtain nitric acid and MeO X And the regeneration cycle of the nitric acid is realized. In addition, the process has strong raw material adaptability, and is particularly suitable for treating brown iron type laterite-nickel ore with high aluminum content.
The invention is realized by the following technical scheme:
a method for recycling valuable metals and acid from laterite-nickel ore specifically comprises the following steps:
(1) Drying and dehydrating laterite-nickel ore raw ore, crushing and grinding to obtain mineral powder, fully stirring and mixing the mineral powder with water and nitric acid according to a certain solid-liquid ratio and acidity to prepare pulp;
(2) Pumping the prepared ore pulp into a reaction kettle, fully stirring, and carrying out heat preservation at a specific temperature for a period of time for selective leaching;
(3) After the leaching reaction is finished, the leaching slurry is pumped into a thickener for solid-liquid separation, and the bottom flow is filtered and dried to obtain iron ore concentrate;
(4) Evaporating and concentrating the overflow liquid, adding the overflow liquid into a reaction kettle for reduction reaction, and filtering the reduced liquid to obtain nickel-cobalt mixed powder;
(5) Decomposing the filtered solution of nickel and cobalt in a decomposing furnace to obtain the product containing MeO x 、O 2 、NO x 、H 2 O, separating the dust gas by a dust collecting system after the dust gas is cooled to obtain mixed powder containing a plurality of metal oxides;
(6) Part of NO after dust collection x The gas is heated by a combustion furnace and is recycled into the decomposing furnace for pyrolyzing the filtered liquid, and the other part of NO x Entering a nitric acid regeneration system to outputThe nitric acid is returned to the leaching process.
Further, in the step (1), the laterite-nickel ore comprises the following components in percentage by mass: ni is 0.5 to 1.5 percent; co is 0.05 to 0.15 percent; 40 to 50 percent of Fe; 0.5 to 4.5 percent of Al; mg is 0.10 to 3.0 percent; sc is 30-100 g/t.
Furthermore, in the step (1), the acidity of the nitric acid is 120-230 g/L, and the solid-liquid ratio is 1.
Further, the stirring speed in the step (2) is 150-300 rpm, the specific temperature range is 160-230 ℃, and the heat preservation time is 0.5-3 h.
Further, the iron content of the iron ore concentrate in the step (3) is 48-60%.
Further, the step (4) further comprises: and cooling the nitric acid volatilized in the process of evaporating and concentrating the overflow liquid to obtain condensed nitric acid, and pumping the condensed nitric acid into a subsequent nitric acid regeneration system.
Further, the overflow liquid in the step (4) is evaporated and concentrated to improve the ion concentration in the solution, and the evaporation and concentration equipment used comprises any one of a multi-effect evaporator and an MVR evaporator or a combination mode thereof.
Further, the reaction temperature of the reduction reaction in the step (4) is 140-220 ℃, the reaction pressure is 2.0-5.0 Mpa, and the stirring speed is 200-700 rpm; the reducing agent includes CO and H 2 Any one or a combination thereof.
Further, the reaction temperature of the reduction reaction in the step (4) is 70-95 ℃, the reaction pressure is normal pressure, and the stirring speed is 100-300 rpm; the used reducing agent is hydrazine hydrate, and the addition amount of the hydrazine hydrate and the molar ratio of the total nickel ions and cobalt ions in the evaporated and concentrated solution is 5-50.
Further, the decomposition method of the decomposition furnace in the step (5) includes any one of, but not limited to, boiling decomposition, calcination decomposition, and spray decomposition, and the decomposition temperature in the furnace is 400 to 900 ℃.
Further, the temperature of the dust gas in the step (5) is reduced to 200-500 ℃, and the dust collection mode comprises any one or a combination of cyclone dust collection, gravity settling dust collection, high-temperature cloth bag dust collection, electrostatic dust collection and high-temperature metal film dust collection.
Further, the metal oxide in the step (5) includes Fe 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 、MgO。
Further, 20-90% of NO is obtained after dust collection in the step (6) x The gas is heated by the combustion furnace and is recycled into the decomposing furnace for pyrolysis of the filtered liquid.
Further, NO entering the nitric acid regeneration system in the step (6) x After deep dust removal, the temperature is reduced to below 130 ℃ by a cooling system to obtain a large amount of condensed acid, wherein the concentration of the condensed acid is 20-40%; NO not absorbed by condensation x Pressurizing to 4.0-5.0 MPa, absorbing in an absorption tower to prepare nitric acid, treating the absorbed tail gas with the condensed acid as absorbent and exhausting.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
(1) The invention avoids adding magnesium oxide, calcium oxide and the like to adjust the pH value of the solution in the traditional process, greatly reduces the purchase cost of auxiliary materials and reduces the direct processing cost;
(2) The problem of nickel and cobalt inclusion in the process of precipitating the aluminum hydroxide by adding alkali in the traditional process is avoided, and the recovery rate of the nickel and cobalt is improved;
(3) The acid used in the process can be regenerated and recycled, so that the purchase quantity of nitric acid is reduced, and the direct processing cost is reduced;
(4) The full recovery and slag-free discharge of valuable metal elements are realized, and the whole process is green and environment-friendly;
(5) The condensed acid formed in the process is recycled to the maximum extent, the waste acid is changed into valuable, the nitric acid regeneration efficiency is improved, and the fixed investment of a nitric acid regeneration system and the nitric acid regeneration cost are reduced.
Drawings
Fig. 1 is a schematic process flow diagram of the recycling process of valuable metals and acid from laterite-nickel ore.
Detailed Description
The invention will be described in further detail with reference to the following figures and specific examples, without limiting the scope of the invention.
The invention discloses a method for recovering valuable metals from laterite-nickel ore and recycling acid. The process flow diagram of the method is shown in figure 1: firstly, crushing and finely grinding laterite-nickel ore raw ore to obtain ore powder, then preparing the ore powder into slurry to carry out nitric acid high-pressure leaching, carrying out solid-liquid separation on the obtained leaching slurry through a thickener to obtain leaching slag and leaching liquid, and filtering and drying the leaching slag to obtain iron ore concentrate. And (3) evaporating and concentrating the leachate, cooling the nitric acid volatilized in the concentration process to obtain condensed nitric acid, and then introducing the condensed nitric acid into a subsequent nitric acid regeneration system. And pumping the concentrated solution into a reaction kettle for reduction to obtain nickel-cobalt mixed powder, and drying the nickel-cobalt mixed powder to be sold as a commodity. The nickel-cobalt separated liquid is decomposed at high temperature in a decomposing furnace to obtain mixed metal oxide powder and NO x Water vapor, O 2 The dust gas is cooled and then is processed by a dust collecting system to obtain the Fe-containing dust 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 The MgO mixed powder can be sold as a commodity or further processed. Part of NO after dust collection x The gas is heated by the combustion furnace and then enters the decomposition system again, and the other part of NO x The gas flows to a nitric acid regeneration system after being cooled. And (3) carrying out tail gas heat exchange, deep dust removal and secondary cooling condensation on the gas entering the nitric acid regeneration system to obtain condensed dilute nitric acid. And pressurizing and thickening the subsequent gas by a nitrogen oxide compressor, and feeding the subsequent gas into an absorption tower. The condensed acid obtained by the previous condensation is pumped to a corresponding tower plate of a nitric acid absorption tower for nitric acid preparation after the concentration is measured, and industrial nitric acid generated by a nitric acid regeneration system is used for the front-end leaching process.
The process is efficient and simple, and the problem that nickel-cobalt metal is carried in aluminum slag due to generation of aluminum hydroxide flocculent precipitate in the process of adding an alkaline substance nickel-cobalt into the laterite-nickel ore nitric acid leaching solution in the traditional process is solved, so that the total recovery rate of the nickel-cobalt metal is improved. Decomposing and regenerating the reduced solution to obtain nitric acid and MeO x Realizing the regeneration cycle of the nitric acid. And the process has strong adaptability of raw materials, and is particularly suitable for treating brown iron type laterite-nickel ore with high aluminum content.
Example 1
Drying, crushing and finely grinding raw laterite-nickel ore ores, wherein the ores contain 0.7% of nickel, 0.069% of cobalt, 48% of iron, 1.02% of aluminum, 0.53% of magnesium and 45g/t of scandium. Mineral powder, water and nitric acid are stirred fully in a slurrying tank to prepare slurry according to the solid-liquid ratio of 1 to 125g/L of initial acidity, then the slurry is pumped into a nitric acid pressure kettle, and selective leaching is carried out under the conditions of stirring speed of 160rpm, leaching temperature of 170 ℃ and heat preservation time of 0.7 h. And pumping the obtained ore pulp into a thickener for solid-liquid separation, and filtering and drying the bottom flow to obtain iron ore concentrate containing 58% of iron. And (4) introducing the overflow liquid into an evaporator for evaporation concentration to improve the ion concentration in the solution, adding the concentrated solution into a pressure reduction kettle for reduction, wherein the used reducing agent is CO. The temperature of the reduction reaction is controlled to be 150 ℃, the pressure in the kettle after the CO is added is 2.0Mpa, the reaction time is 0.5h, and the stirring speed is 300rpm. And after the reaction is finished, filtering to obtain nickel-cobalt powder, and washing, filtering and drying the mixed powder to serve as a commodity for sale. Adding the nickel-cobalt separated liquid into a decomposing furnace for decomposition at the decomposition temperature of 500 ℃ to obtain the NO-containing liquid x 、H 2 O、MeO x 、O 2 The mixed dust gas of (2). The dust gas is cooled to 200 ℃ and separated by dust collecting equipment to obtain the Fe-containing dust gas 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 And MgO mixed powder, which can be sold as a commodity or subjected to deep processing. 80% NO after dust collection x The gas is heated by a combustion furnace and is circulated into the decomposing furnace again for pyrolyzing the separated liquid of the nickel cobalt powder. Remaining NO x And deeply dedusting the other part of the gas, and cooling to reduce the temperature to 45 ℃ to obtain the condensed nitric acid with the concentration of 35%. The remaining gas was pressurized to 4.0Mpa by a nitrogen oxide compressor and introduced into an absorption tower. And pumping the obtained condensed acid into a corresponding tower plate of the absorption tower, finally obtaining regenerated nitric acid with the concentration of 48% at the tower bottom, and treating the absorbed tail gas to reach the standard and discharging.
Example 2
Drying, crushing and finely grinding raw laterite-nickel ore ores, wherein the ores contain 0.9% of nickel, 0.093% of cobalt, 46% of iron, 2.3% of aluminum, 1.32% of magnesium and 63g/t of scandium. Mineral powder, water and nitric acid are stirred fully in a slurrying tank to prepare slurry according to the solid-liquid ratio of 1:2 and the initial acidity of 160g/L, and then the slurry is pumped into a nitric acid pressure kettle, and selective leaching is carried out under the conditions of stirring speed of 180rpm, leaching temperature of 180 ℃ and heat preservation time of 1.0 h. And pumping the obtained ore pulp into a thickener for solid-liquid separation, and filtering and drying the bottom flow to obtain iron ore concentrate containing 60 percent of iron. And (4) introducing the overflow liquid into an evaporator for evaporation concentration to improve the ion concentration in the solution, adding the concentrated solution into a pressure reduction kettle for reduction, wherein the used reducing agent is CO. The temperature of the reduction reaction is controlled to be 180 ℃, the pressure in the kettle after the CO is added is 2.5Mpa, the reaction time is 1h, and the stirring speed is 400rpm. Filtering to obtain nickel-cobalt powder after the reaction is finished, and washing, filtering and drying the mixed powder to obtain the product for sale. Adding the nickel-cobalt separated liquid into a decomposing furnace for decomposition at the decomposition temperature of 550 ℃ to obtain the NO-containing liquid x 、H 2 O、MeO x 、O 2 The mixed dust gas. The dust gas is cooled to 250 ℃ and is separated by dust collecting equipment to obtain the Fe-containing gas 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 And MgO mixed powder, which can be sold as a commodity or subjected to deep processing. 70% NO after dust collection x The gas is heated by a combustion furnace and is circulated into the decomposing furnace again for pyrolyzing the separated liquid of the nickel cobalt powder. Remaining NO x And deeply dedusting the other part of gas, and cooling to reduce the temperature to 60 ℃ to obtain the condensed nitric acid with the concentration of 33%. The remaining gas was pressurized to 4.5Mpa by a nitrogen oxide compressor and introduced into an absorption tower. And pumping the obtained condensed acid into a corresponding tower plate of an absorption tower, finally obtaining regenerated nitric acid with the concentration of 49% at the tower bottom, and treating the absorbed tail gas to reach the standard and discharging.
Example 3
Drying, crushing and finely grinding raw laterite-nickel ore ores, wherein the ores contain 1.0% of nickel, 0.12% of cobalt, 45% of iron, 2.3% of aluminum, 2.35% of magnesium and 83% of scandiumg/t. Mineral powder, water and nitric acid are fully stirred in a slurrying tank to prepare slurry according to the solid-liquid ratio of 1 to 3 and the initial acidity of 180g/L, then the slurry is pumped into a nitric acid pressure kettle, and selective leaching is carried out under the conditions of stirring speed of 200rpm, leaching temperature of 200 ℃ and heat preservation time of 1.5 h. And pumping the obtained ore pulp into a thickener for solid-liquid separation, and filtering and drying the bottom flow to obtain iron ore concentrate containing 57% of iron. Introducing the overflow liquid into an evaporator for evaporation and concentration to increase the ion concentration in the solution, adding the concentrated solution into a pressure reduction kettle for reduction, wherein the reducing agent is H 2 . The temperature of the reduction reaction is controlled to be 210 ℃, and H is added 2 The pressure in the kettle is 3.2Mpa, the reaction time is 2.5h, and the stirring speed is 600rpm. Filtering to obtain nickel-cobalt powder after the reaction is finished, and washing, filtering and drying the mixed powder to obtain the product for sale. Adding the nickel-cobalt separated liquid into a decomposing furnace for decomposition at the decomposition temperature of 650 ℃ to obtain the NO-containing liquid x 、H 2 O、MeO x 、O 2 The mixed dust gas of (2). The dust gas is cooled to 300 ℃ and is separated by dust collecting equipment to obtain the Fe-containing iron 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 The MgO mixed powder can be sold as a commodity or subjected to deep processing. 50% NO after dust collection x The gas is heated by a combustion furnace and is circulated into the decomposing furnace again for pyrolyzing the separated liquid of the nickel cobalt powder. Remaining NO x And deeply dedusting the other part of the gas, and cooling to reduce the temperature to 80 ℃ to obtain the condensed nitric acid with the concentration of 29%. The remaining gas was pressurized to 4.7Mpa by a nitrogen oxide compressor and introduced into an absorption tower. And pumping the obtained condensed acid into a corresponding tower plate of the absorption tower, finally obtaining regenerated nitric acid with the concentration of 50% at the tower bottom, and treating the absorbed tail gas to reach the standard and discharging.
Example 4
The raw laterite-nickel ore is dried, crushed and finely ground, and the raw laterite-nickel ore contains 1.2% of nickel, 0.19% of cobalt, 44% of iron, 3.4% of aluminum, 2.5% of magnesium and 91g/t of scandium. Mineral powder, water and nitric acid are stirred fully in a pulping tank to prepare slurry according to the solid-to-liquid ratio of 1:4 and the initial acidity of 200g/L, and then the slurry is pumped into a nitric acid pressure kettle at 220rpmThe stirring speed and the leaching temperature are 210 ℃, and the selective leaching is carried out under the condition of the heat preservation time of 2.0 h. And pumping the obtained ore pulp into a thickener for solid-liquid separation, and filtering and drying the bottom flow to obtain iron ore concentrate containing 53% of iron. And (4) introducing the overflow liquid into an evaporator for evaporation concentration to improve the ion concentration in the solution, adding the concentrated solution into a reaction kettle for reduction, wherein the used reducing agent is hydrazine hydrate. Wherein hydrazine hydrate and the liquid after evaporation concentration are according to N 2 H 4 :(Ni 2+ +Co 2+ ) Mixing and configuring according to the proportion of 40. The temperature of the reduction reaction is controlled to be 75 ℃, the reaction time is 1h, and the stirring speed is 150rpm. Filtering to obtain nickel-cobalt powder after the reaction is finished, and washing, filtering and drying the mixed powder to obtain the product for sale. Adding the nickel-cobalt separated liquid into a decomposing furnace for decomposition at the decomposition temperature of 700 ℃ to obtain the NO-containing liquid x 、H 2 O、MeO x 、O 2 The mixed dust gas of (2). The dust gas is cooled to 300 ℃ and separated by dust collecting equipment to obtain the Fe-containing gas 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 And MgO mixed powder, which can be sold as a commodity or subjected to deep processing. 35% NO after dust collection x The gas is heated by a combustion furnace and is circulated into the decomposing furnace again for pyrolyzing the separated liquid of the nickel cobalt powder. Remaining NO x The other part of the gas is deeply dedusted and then cooled to 100 ℃ to obtain condensed nitric acid with the concentration of 25%. The remaining gas was pressurized to 5.0MPa by a nitrogen oxide compressor and introduced into an absorption column. And pumping the obtained condensed acid into a corresponding tower plate of the absorption tower, finally obtaining regenerated nitric acid with the concentration of 51% at the tower bottom, and treating the absorbed tail gas to reach the standard and discharging.
Example 5
Drying, crushing and finely grinding the raw laterite-nickel ore, wherein the ore contains 1.4% of nickel, 0.12% of cobalt, 43% of iron, 4.0% of aluminum, 2.7% of magnesium and 98g/t of scandium. Mineral powder, water and nitric acid are fully stirred in a slurrying tank to prepare slurry according to the solid-liquid ratio of 1 to 5 and the initial acidity of 220g/L, then the slurry is pumped into a nitric acid pressure kettle, the stirring speed of 235rpm, the leaching temperature of 200 ℃ and the heat preservation time of 3.0h are carried outAnd (4) selective leaching. And pumping the obtained ore pulp into a thickener for solid-liquid separation, and filtering and drying the bottom flow to obtain iron ore concentrate containing 48 percent of iron. And (4) introducing the overflow liquid into an evaporator for evaporation concentration to improve the ion concentration in the solution, adding the concentrated solution into a reaction kettle for reduction, wherein the used reducing agent is hydrazine hydrate. Wherein hydrazine hydrate and the solution after evaporation concentration are according to N 2 H 4 :(Ni 2+ +Co 2+ ) Mixing and preparing according to the proportion of 40. And after the reaction is finished, filtering to obtain nickel-cobalt powder, and washing, filtering and drying the mixed powder to serve as a commodity for sale. Adding the nickel-cobalt separated liquid into a decomposing furnace for decomposition at the decomposition temperature of 800 ℃ to obtain the NO-containing liquid x 、H 2 O、MeO x 、O 2 The mixed dust gas. The dust gas is cooled to 400 ℃ and is separated by dust collecting equipment to obtain the Fe-containing material 2 O 3 、Al 2 O 3 、Sc 2 O 3 、MnO 2 The MgO mixed powder can be sold as a commodity or subjected to deep processing. 25% NO after dust collection x The gas is heated by a combustion furnace and is circulated into the decomposing furnace again for pyrolyzing the separated liquid of the nickel cobalt powder. Remaining NO x And deeply dedusting the other part of the gas, and cooling to reduce the temperature to 110 ℃ to obtain the condensed nitric acid with the concentration of 23%. The remaining gas was pressurized to 5.0MPa by a nitrogen oxide compressor and introduced into an absorption column. And pumping the obtained condensed acid into a corresponding tower plate of the absorption tower, finally obtaining regenerated nitric acid with the concentration of 52% at the tower bottom, and treating the absorbed tail gas to reach the standard and discharging.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.