Comprehensive utilization method for valuable elements in discharged slag of laterite-nickel ore smelting

Abstract

A comprehensive utilization method for valuable elements in discharged slag of laterite-nickel ore smelting, comprising the following steps: S1, placing, into a tubular furnace, iron-aluminum slag generated by means of hydrometallurgy of laterite-nickel ore, introducing HCl gas flow, and carrying out first-stage distillation at 185-290°C to obtain first-stage distillation tail gas and first-stage distillation residues; and condensing the first-stage distillation tail gas to obtain anhydrous AlCl3; S2, introducing HCl gas flow into the first-stage distillation residues for second-stage distillation at 320-500°C to obtain second-stage distillation tail gas and second-stage distillation residues; condensing the second-stage distillation tail gas to obtain anhydrous FeCl3; S3, leaching the second-stage distillation residues by using a leaching solution to obtain leaching residues and a leachate; and carrying out scandium precipitation treatment on the leachate to obtain a scandium precipitate and a residual solution after scandium precipitation; and S4, adjusting the pH value of said residual solution to carry out precipitation treatment to obtain a nickel-cobalt hydroxide. The obtained aluminum, iron and scandium products have high purity and high recovery rate.

Description

A comprehensive utilization method of valuable elements in slag discharged from laterite nickel ore smelting Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of laterite nickel ore, and in particular to a method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting. Background Art

[0002] Nickel, a pillar of the rapid development of new energy, has become a strategic metal resource. Laterite nickel ore, one of the primary natural occurrences of nickel, is attracting increasing research attention. Hydrometallurgical processes for laterite nickel ore are widely used in industrial production. Hydrometallurgical processes generate significant amounts of smelting waste slag, particularly ferroaluminum slag containing 0.05-0.5wt.% of metallic Sc, which has significant recycling value.

[0003] Currently, the processes for extracting Sc from Sc-containing slag are mostly acid-base leaching or water leaching after roasting, and further enrichment of Sc is achieved by extraction or precipitation. For example, patent "CN103468979A" discloses a method for recovering scandium from iron-aluminum slag in laterite nickel ore smelting, which uses leaching and extraction to recover scandium.

[0004] However, since the aluminum content of ferroaluminum slag is 10-30 times that of scandium, and since the chemical properties of Sc and Al are very similar, it is difficult to effectively separate Al and Sc using existing methods such as extraction or oxalate or hydroxide precipitation. Most of the Sc will continue to enter the final aluminum or iron product during the processing process, which not only affects the purity of the aluminum or iron product, but also reduces the effective recovery rate of Sc.

[0005] Summary of the Invention

[0006] In view of this, the present application provides a method for comprehensive utilization of valuable elements in the slag discharged from laterite nickel ore smelting, and the obtained aluminum, iron and scandium products have high purity and high recovery rate.

[0007] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0008] The present application provides a method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting, comprising the following steps:

[0009] S1. The iron-aluminum slag produced by hydrometallurgy of laterite nickel ore is placed in a tube furnace and a stream of HCl is introduced at 185-290 ° C for a distillation to obtain a distillation tail gas and a distillation residue; a distillation tail gas is condensed to obtain anhydrous AlCl3;

[0010] S2. The first distillation residue was passed through a stream of HCl and distilled for a second stage at 320-500 ° C to obtain a second distillation tail gas and a second distillation residue; the second distillation tail gas was condensed to obtain anhydrous FeCl3;

[0011] S3. The second distillation residue was leached using the extract to obtain a leaching residue and a leachate; the leachate was subjected to scandium precipitation treatment to obtain a precipitate of scandium and a liquid after precipitation of scandium;

[0012] S4. Adjust the pH value of the solution after scandium precipitation to perform precipitation treatment to obtain nickel cobalt hydroxide.

[0013] Preferably, step S1 further comprises absorbing the HCl gas flow after the first stage of distillation with an alkaline solution, and step S2 further comprises absorbing the HCl gas flow after the second stage of distillation with an alkaline solution.

[0014] Preferably, the extract in step S3 is water or acid, the solid-liquid ratio of the second-stage distillation residue to the leaching liquid is 50-200 g / L, the leaching temperature is 20-25° C., and the leaching time is 0.5-2 h.

[0015] Preferably, the acid is one or more of an inorganic acid or an organic acid, and the concentration of the acid is 0.001-0.1 mol / L.

[0016] Preferably, in step S3, the scandium precipitation treatment includes the steps of: adjusting the pH of the leaching solution to 4-6, filtering, and obtaining a scandium precipitate and a scandium precipitation liquid, wherein the scandium precipitate is one or more of scandium hydroxide and scandium oxalate.

[0017] Preferably, step S3 further comprises calcining the scandium precipitate at 500-1000° C. for 0.5-5 h to obtain scandium oxide.

[0018] Preferably, the leaching residue comprises a mixture of SiO2 and CaSO4, and the leaching residue is used to manufacture environmentally friendly permeable bricks or ceramsite.

[0019] Preferably, in step S4, the pH is 9-10.

[0020] Preferably, the flow rate of the HCl gas flow in the first distillation and the second distillation is 10-300 ml / min, and the introduction time is 0.5-3 h.

[0021] Preferably, the flow rates of the HCl gas streams used in the first-stage distillation and the second-stage distillation remain unchanged, and the concentrations of the alkali solutions in step S1 and step S2 remain unchanged.

[0022] The beneficial effects of this application are as follows:

[0023] The present application achieves deep separation of AlCl3, FeCl3 and ScCl3 through segmented distillation and sublimation, and the final iron, aluminum and scandium products obtained are of high purity and high recovery rate;

[0024] The two distillation gas streams used in this application are both HCl gas streams, which can eliminate the iron, aluminum and scandium chlorination steps in the pretreatment process, shorten the process flow and improve production efficiency;

[0025] In addition to obtaining high-purity and high-recovery iron, aluminum, and scandium products, this application also obtains leaching residue containing SiO2 and CaSO4, which can be used to manufacture environmentally friendly permeable bricks or expanded clay; at the same time, nickel cobalt hydroxide (MHP) is also obtained with a high yield, realizing the recovery and treatment of nickel and cobalt; the products and by-products produced can be used in industrial applications, with less waste residue and waste liquid, environmental friendliness, and high commercial value. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] The present application provides a method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting, comprising the following steps:

[0028] S1. The iron-aluminum slag produced by hydrometallurgy of laterite nickel ore is placed in a tube furnace and a stream of HCl is introduced at 185-290 ° C for a distillation to obtain a distillation tail gas and a distillation residue; a distillation tail gas is condensed to obtain a solid anhydrous AlCl3;

[0029] S2. The first distillation residue was passed through a gas stream of HCl at 320-500 ℃ for two-stage distillation to obtain a second distillation tail gas and a second distillation residue; the second distillation tail gas was condensed to obtain a solid anhydrous FeCl3;

[0030] S3. The second distillation residue was leached using the extract to obtain a leaching residue and a leachate; the leachate was subjected to scandium precipitation treatment to obtain a precipitate of scandium and a liquid after precipitation of scandium;

[0031] S4. Adjust the pH value of the solution after scandium precipitation to perform precipitation treatment to obtain nickel cobalt hydroxide.

[0032] This solution is based on the different physical properties of iron, aluminum and scandium metal chlorides, namely the different sublimation temperatures of AlCl3, FeCl3 and ScCl3. Through the method of staged distillation and sublimation, the deep separation between the three is achieved, which greatly improves the recovery rate of scandium and obtains high-purity iron, aluminum and scandium related products. In addition, a small amount of nickel and cobalt entrained in the iron and aluminum slag can also be recovered and processed to obtain related nickel and cobalt products (MHP). It is worth noting that AlCl3(s), FeCl3(s) and ScCl3(s) are prone to decomposition when directly heated and distilled, such as AlCl3(s) Direct heating distillation will produce 2AlCl3+3H2O=Al2O3+6HCl, causing the aluminum element to continue to remain in the iron-aluminum slag and fail to achieve the purpose of separation. In order to inhibit the progress of the above chemical reaction, this solution further proposes to introduce HCl gas flow during the heating distillation process to achieve good results. It was unexpectedly discovered that the use of HCl gas flow can omit the process of chlorination of iron, aluminum and scandium in the pretreatment process.

[0033] As known to those skilled in the art, the iron, aluminum, and scandium in the iron-aluminum slag exist in the form of hydroxides. In this solution, during the introduction of HCl gas flow, the following reactions gradually occur by controlling the distillation temperature:

[0034] (Fe,Al,Sc)(OH)3+3HCl=(Fe,Al,Sc)Cl3+3H2O (1); The hydroxides of iron, aluminum, and scandium are converted into corresponding solid salts by passing HCl;

[0035] AlCl3(s)→AlCl3(g) (2); Under the condition of adding HCl, AlCl3 is sublimated from solid (s) to gas (g) by controlling T (185-290℃);

[0036] FeCl3(s)→FeCl3(g) (3); Under the condition of introducing HCl, FeCl3 is sublimated from solid (s) to gas (g) by controlling T (320-500℃);

[0037] However, since the sublimation process of ScCl3(s)→ScCl3(g) requires high conditions (it will only occur when T>850℃), it consumes a lot of energy, and since the subsequent processing steps of the three-stage distillation tail gas and the three-stage distillation residue obtained after the three-stage distillation are complicated, this application adopts the leaching-scandium precipitation-nickel and cobalt precipitation method for post-processing after the second-stage distillation, and the obtained by-products are of high value and save energy.

[0038] Step S1 further includes absorbing the HCl gas flow after the first distillation with an alkali solution, and step S2 further includes absorbing the HCl gas flow after the second distillation with an alkali solution; that is, the distillation tail gas is first connected to a condensation collection device, and then the remaining gas after condensation is passed into the alkali solution for absorption. In order to fully condense AlCl3 and FeCl3, the condensation collection device can be repeatedly set to multiple; the alkali solution used includes but is not limited to one or more of ammonia water and sodium hydroxide, and the concentration of the alkali solution is 1-3 mol / L.

[0039] In step S3, the extract is water or acid, the solid-to-liquid ratio of the second-stage distillation residue to the leaching solution is 50-200 g / L, the leaching temperature is 20-25°C, and the leaching time is 0.5-2 hours. The leaching process produces a leaching residue containing SiO2 and CaSO4 and a leachate containing salt-resistant and nickel-cobalt salts. This solid-to-liquid ratio maximizes the leaching of SiO2 and CaSO4. The leaching residue, comprising a mixture of SiO2 and CaSO4, is used to manufacture environmentally friendly permeable bricks or ceramsite.

[0040] The acid is one or more inorganic or organic acids, and the acid concentration is 0.001-0.1 mol / L. If the acid concentration is too high, calcium sulfate will dissolve, and if the acid concentration is too low, no leaching effect will be achieved.

[0041] In step S3, the scandium precipitation treatment includes the steps of adjusting the pH of the leaching solution to 4-6, filtering, and obtaining a scandium precipitate and a scandium precipitation liquid. The scandium precipitate is one or more of scandium hydroxide and scandium oxalate.

[0042] Step S3 also includes calcining the scandium precipitate at 500-1000° C. for 0.5-5 hours to obtain scandium oxide.

[0043] Scandium oxide with a purity of >99% can be obtained through the scandium precipitation-calcination treatment in step S3; and the liquid after the scandium precipitation can be used to recover nickel-cobalt hydroxide.

[0044] In step S4, the pH is 9-10. In this pH range, nickel and cobalt are precipitated to form nickel-cobalt hydroxide (MHP) and a small amount of nickel-cobalt carbonate.

[0045] The flow rate of the HCl gas flow in the first and second distillation stages is 10-300 ml / min, and the introduction time is 0.5-3 h. Under this flow rate and time limit, AlCl3 and FeCl3 are fully distilled and sublimed.

[0046] The flow rates of the HCl gas streams used in the first and second distillation stages remain unchanged, and the concentrations of the alkali solutions in steps S1 and S2 remain unchanged; this is beneficial for maintaining the stability of process conditions, reducing the number of adjustments, and saving resources.

[0047] The present invention is further described below through specific examples.

[0048] Example 1

[0049] A method for comprehensively utilizing valuable elements in slag discharged from laterite nickel ore smelting comprises the following steps:

[0050] S1. Take 1kg of iron-aluminum slag produced by hydrometallurgy of laterite nickel ore and place it in a tube furnace, control the HCl gas flow rate to 30ml / min, the distillation temperature to 200°C, and the time to 2h to obtain a section of distillation tail gas and a section of distillation residue. The distillation tail gas is condensed and condensed using a circulating water device to collect solid anhydrous aluminum chloride with a purity of 99.52%. The yield of anhydrous aluminum chloride is 92.14%. The condensed distillation tail gas (HCl gas flow) is passed into an alkali solution for absorption, and the alkali solution is a NaOH solution with a concentration of 1mol / L. The yield of anhydrous aluminum chloride is obtained by dividing the aluminum content of the anhydrous aluminum chloride by the aluminum content of the original iron-aluminum slag phase, and the aluminum content of the original iron-aluminum slag phase is determined by ICP;

[0051] S2. After the first distillation residue was kept warm for 2h, the temperature was further increased to 400°C and kept warm for 2h. The HCl gas flow rate was controlled to be constant. After distillation and sublimation, the second distillation tail gas and the second distillation residue were obtained. The second distillation tail gas was collected after the circulating water condenser to obtain solid anhydrous ferric chloride with a purity of 99.33%. The yield of ferric chloride was 90.45%. The condensed distillation tail gas (HCl gas flow) was passed into an alkali solution for absorption. The concentration of the alkali solution was constant. The yield of anhydrous ferric chloride was obtained by dividing the iron content of the anhydrous ferric chloride by the iron content of the original iron-aluminum slag phase. The iron content of the original iron-aluminum slag phase was determined by ICP.

[0052] S3. The second-stage distillation residue was leached with 0.01 mol / L sulfuric acid, the solid-liquid ratio was controlled at 100 g / L, the time was 30 min, and the temperature was 20-25 ° C to obtain a leached residue and a leachate; the leached residue was a mixture of SiO2 and CaSO4, which can be used to manufacture environmentally friendly permeable bricks or ceramsite, the leachate was a Sc enriched solution and an enriched residue, the leachate was adjusted to pH 5 using liquid alkali, and filtered to obtain a scandium precipitate and a scandium precipitation liquid, the scandium precipitate was Sc(OH)3, and the scandium precipitate was then calcined at a temperature of 600 ° C for 1 h to obtain Sc2O3 with a purity of 99.12%, and the Sc yield was 97.34%; the scandium precipitation liquid was further adjusted to pH 10 with liquid alkali, filtered and precipitated to obtain nickel cobalt hydroxide (MHP), and the nickel cobalt yield was 95.25%; the yields of Sc and nickel cobalt were calculated in the same way as the aluminum yield in step S1.

[0053] Example 2

[0054] A method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting is the same as Example 1 in other contents, except that the first-stage distillation temperature is 185°C, and liquid anhydrous aluminum chloride is collected with a purity of 92.15% and a yield of 85.28%; the second-stage distillation temperature is 500°C, and anhydrous ferric chloride is collected with a purity of 98.34% and a yield of ferric chloride of 91.52%; the pH of the leachate is adjusted to 4 to obtain Sc2O3 with a purity of 96.66% and a yield of Sc of 96.21%; the pH of the solution after scandium precipitation is adjusted to 9, and the nickel and cobalt yield is 93.37%.

[0055] Example 3

[0056] A method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting is the same as Example 1 in other contents, except that the first-stage distillation temperature is 290°C, and liquid anhydrous aluminum chloride is collected with a purity of 99.31% and a yield of 95.29%; the second-stage distillation temperature is 320°C, and anhydrous ferric chloride is collected with a purity of 99.36% and a yield of ferric chloride of 82.58%; the pH of the leachate is adjusted to 6 to obtain Sc2O3 with a purity of 95.45%, a Sc yield of 95.39%, and a nickel and cobalt yield of 97.44%.

[0057] Comparative Example 1

[0058] A method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting is the same as Example 1 except that the first-stage distillation temperature and the second-stage distillation temperature are both 200°C. Liquid anhydrous aluminum chloride is collected with a purity of 99.28%, the yield of anhydrous aluminum chloride is 92.63%, almost no ferric chloride is collected, the purity of Sc2O3 is 90.52%, the yield of Sc is 80.94%, and the yield of nickel and cobalt is 80.39%.

[0059] Comparative Example 2

[0060] A method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting is the same as Example 1 in other contents, except that the first-stage distillation temperature and the second-stage distillation temperature are both 400°C, and liquid anhydrous aluminum chloride is collected with a purity of 75.85% and a yield of 96.64%. Anhydrous ferric chloride is collected with a purity of 95.59% and a yield of ferric chloride of 73.74%. Sc2O3 is obtained with a purity of 92.29%, a yield of Sc is 83.68%, and a nickel-cobalt yield is 84.55%.

[0061] It can be seen that the present application achieves deep separation of AlCl3, FeCl3 and ScCl3 through segmented distillation and sublimation, and the iron, aluminum and scandium products finally obtained have high purity and high recovery rate.

[0062] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting, characterized in that: The following steps are involved: S1. The iron-aluminum slag produced by hydrometallurgy of laterite nickel ore is placed in a tubular furnace, and HCl gas is introduced at 185-290 ° C for a distillation to obtain a distillation tail gas and a distillation residue; the distillation tail gas is condensed to obtain anhydrous AlCl3; S2. The first distillation residue is introduced into a HCl gas stream and distilled in two stages at 320-500 ° C to obtain a second distillation tail gas and a second distillation residue; the second distillation tail gas is condensed to obtain anhydrous FeCl3; S3. The second distillation residue is leached using an extract to obtain a leaching residue and a leachate; the leachate is subjected to scandium precipitation treatment to obtain a scandium precipitate and a scandium precipitation solution; S4. Adjusting the pH value of the solution after the scandium precipitation to perform precipitation treatment, thereby obtaining nickel-cobalt hydroxide.

2. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 1, characterized in that: Step S1 further comprises absorbing the HCl gas flow after the first stage of distillation with an alkali solution, and step S2 further comprises absorbing the HCl gas flow after the second stage of distillation with an alkali solution.

3. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 1, characterized in that: In step S3, the extract is water or acid, the solid-liquid ratio of the second-stage distillation residue to the leaching solution is 50-200 g / L, the leaching temperature is 20-25° C., and the leaching time is 0.5-2 h.

4. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 3, characterized in that: The acid is one or more of an inorganic acid or an organic acid, and the concentration of the acid is 0.001-0.1 mol / L.

5. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 1, characterized in that: In step S3, the scandium precipitation treatment includes the steps of: adjusting the pH of the leaching solution to 4-6, filtering, and obtaining a scandium precipitate and a scandium precipitation liquid, wherein the scandium precipitate is one or more of scandium hydroxide and scandium oxalate.

6. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 1, characterized in that: Step S3 also includes calcining the scandium precipitate at 500-1000° C. for 0.5-5 h to obtain scandium oxide.

7. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 1, characterized in that: The leached residue comprises a mixture of SiO2 and CaSO4, and the leached residue is used for manufacturing environmentally friendly permeable bricks or ceramsite.

8. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 1, characterized in that: In step S4, the pH is 9-10.

9. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 1, characterized in that: The flow rate of the HCl gas flow in the first-stage distillation and the second-stage distillation is 10-300 ml / min, and the introduction time is 0.5-3 h.

10. The method for comprehensive utilization of valuable elements in slag discharged from laterite nickel ore smelting according to claim 2, characterized in that: The flow rates of the HCl gas streams used in the first-stage distillation and the second-stage distillation remain unchanged, and the concentrations of the alkali solutions in step S1 and step S2 remain unchanged.

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