Back washing method of neodymium iron boron waste acid leaching iron slag
By using concentrated hydrochloric acid to wet and slurry in the recovery process of NdFeB scrap acid-immersed iron slag, combined with warming and ultrasonic treatment, the problem of large rare earth loss is solved, the rare earth recovery efficiency and overall recovery rate are improved, and more efficient is achieved rare earth recycling.
Patent Information
- Application Number
- CN202411337205.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-25
- Publication Date
- 2024-12-27
AI Technical Summary
In the existing NdFeB scrap acid-leached iron slag recycling process, rare earths suffer a large loss, resulting in low recycling benefits and it is difficult to effectively extract rare earth elements due to special forms of distribution.
After using concentrated hydrochloric acid to wet and slurry in a certain proportion, combined with warming and ultrasonic oxidation, the use of concentrated hydrochloric acid and pH value correction are optimized to improve the leaching efficiency of rare earth elements through multiple steps of solid-liquid separation and water washing.
The recycling efficiency of rare earths has been significantly improved, and the rare earth content has dropped from 0.5%-0.6% to 0.2%-0.3%, reducing rare earth losses and improving overall recovery rate and benefits.
Smart Images
Figure CN119194076A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of industrial waste slag recovery, in particular to a method for rewashing NdFeB waste acid-leached iron slag. Background Art
[0002] With the rapid development of the new energy sector, the demand for NdFeB magnets has increased rapidly. During the production of permanent magnet materials, 25% to 30% of scraps, namely NdFeB scraps, are generated. In addition, as time goes by, more and more equipment using NdFeB magnets will be scrapped due to the end of service, resulting in a large amount of NdFeB scraps, which are basically the same as NdFeB magnetic materials, with a rare earth content of 20%-25%, of which praseodymium and neodymium account for more than 80%. The two are the main rare earth components. Praseodymium and neodymium are important elements supporting the magnetic material industry and have extremely high recycling value.
[0003] NdFeB waste acid leaching slag is the acid leaching slag produced by the optimal solution process to decompose NdFeB waste in the process of extracting rare earths from NdFeB waste. Its main components are Fe2O3 and REO (rare earth oxides). The REO content in the acid leaching slag is <0.5%. Generally, enterprises will sell it as ironmaking raw materials. However, due to the poor control of the oxidation rate in the raw material roasting process, the terminal control conditions in the acid leaching process and the impurity removal process, it is easy to cause the REO content in the acid leaching slag to reach 0.6%-1.0%. If this part of the slag is sold, it will cause a large loss of rare earths, affect the overall rate of return, and affect the overall income of the company. At present, the traditional rewashing process in the industry is to add concentrated acid to the mixing barrel to leach rare earths, adjust the pH value to remove impurities, and wash and filter in the plate and frame mill. Finally, the rare earth in the acid leaching slag after the second rewashing is reduced to 0.5%-0.6%, and the recoverable rare earth is 0.1%-0.4%. Most rare earths cannot be dissolved by simple hydrochloric acid due to their special form in the residue. Summary of the invention
[0004] In view of the shortcomings of the prior art, the present invention provides a method for rewashing NdFeB waste acid leaching iron slag, which solves the problems of low recovery efficiency of high-industrial waste and large loss of rare earth in the slag.
[0005] To achieve the above purpose, the present invention is implemented by the following technical scheme: a method for rewashing NdFeB waste acid leaching iron slag, comprising the following steps:
[0006] Step 1: Wetting the dried re-washing residue with concentrated hydrochloric acid in a certain proportion, and then leaving it for a period of time;
[0007] Step 2: slurry the washed residue after placement according to a certain solid-liquid ratio;
[0008] Step 3, adding concentrated hydrochloric acid to the slurry to react for several hours;
[0009] Step 4: The material is heated, an ultrasonic oxidizer is used to vibrate the material to accelerate the leaching of rare earth elements in the rewashed slag, and liquid alkali is added to adjust the pH value;
[0010] Step 5, performing solid-liquid separation on the adjusted material to obtain feed liquid and filtered iron slag;
[0011] Step 6: Wash the filtered iron slag twice with water to obtain a low-concentration rare earth liquid and unqualified iron slag.
[0012] Preferably, in the step 1, the rewashed slag is leaching filter press slag obtained after high-temperature calcination of NdFeB waste.
[0013] Preferably, in step 1, the mass ratio of the concentrated hydrochloric acid to the rewashing residue is (1:20) to (1:40).
[0014] Preferably, in the step 1, the re-washed residue is left to stand for a period of time after being wetted, specifically 5 to 10 days.
[0015] Preferably, in step 2, the solid-liquid ratio of the slurry is 1:(1-3).
[0016] Preferably, in step 1 and step 3, the concentration of concentrated hydrochloric acid is 6 to 10 mol / L, and in step 3, the reaction of concentrated hydrochloric acid is 2 to 4 hours.
[0017] Preferably, in step 4, the heating temperature is 80-100°C, the pH value is 3-5, and the ultrasonic air flow rate is 20-40m 3 / h, reaction time 1 to 3h.
[0018] Preferably, in step five, solid-liquid separation is carried out in any one of filtering devices such as a filter press and a filter.
[0019] Preferably, in step six, the water washing method is one of stirring washing, vacuum filtration washing or plate and frame washing, the water used for the first water washing is the recovered liquid obtained from the second water washing of the iron slag, and the water used for the second water washing is tap water.
[0020] The present invention provides a method for rewashing NdFeB waste acid leaching iron slag, which has the following beneficial effects:
[0021] 1. The present invention greatly improves the recovery efficiency of rare earths by optimizing the solid-liquid ratio and reaction time of slurry adjustment, and cooperates with temperature treatment and ultrasonic assistance, reducing the rare earth content in the final secondary rewashing acid leaching residue to 0.2%-0.3%, providing effective treatment for the acid leaching residue with a REO content of 0.6%-1.0%, avoiding a large amount of rare earth loss, and improving the overall yield and profit.
[0022] 2. The present invention effectively improves the recovery efficiency of rare earths in industrial waste by optimizing each link of the method flow, the proportion of concentrated hydrochloric acid used, the placement time, the solid-liquid ratio of slurry adjustment, the temperature treatment, the ultrasonic vibration assistance, the pH value adjustment, the solid-liquid separation and the synergistic effect of the water washing treatment steps. The specific rewashing method is adopted to enable most of the rare earths that are originally difficult to dissolve due to their special occurrence forms to be leached and recovered, and the recovery value of the NdFeB waste acid leaching residue is fully explored. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is a flow chart of a method for rewashing NdFeB waste acid leaching iron slag according to the present invention; DETAILED DESCRIPTION
[0024] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0025] Please see attached Figure 1 The embodiment of the present invention provides a method for rewashing NdFeB waste acid leaching iron slag, comprising the following steps:
[0026] Step 1: Wetting the dried re-washing residue with concentrated hydrochloric acid in a certain proportion, and then leaving it for a period of time;
[0027] Step 2: slurry the washed residue after placement according to a certain solid-liquid ratio;
[0028] Step 3, adding concentrated hydrochloric acid to the slurry to react for several hours;
[0029] Step 4: The material is heated, an ultrasonic oxidizer is used to vibrate the material to accelerate the leaching of rare earth elements in the rewashed slag, and liquid alkali is added to adjust the pH value;
[0030] Step 5, performing solid-liquid separation on the adjusted material to obtain feed liquid and filtered iron slag;
[0031] Step 6: Wash the filtered iron slag twice with water to obtain a low-concentration rare earth liquid and unqualified iron slag.
[0032] In step 1, the rewashed slag is the leaching filter press slag after high-temperature calcination of NdFeB waste.
[0033] In step 1, the mass ratio of concentrated hydrochloric acid to re-washing residue is (1:20) to (1:40).
[0034] In step 1, the re-washed residue is left to stand for a period of time, specifically 5 to 10 days, after being wetted.
[0035] In step 2, the solid-liquid ratio of the slurry is 1:(1-3).
[0036] In step 1 and step 3, the concentration of concentrated hydrochloric acid is 6 to 10 mol / L, and in step 3, the reaction of concentrated hydrochloric acid is 2 to 4 hours.
[0037] In step 4, the heating temperature is 80-100°C, the pH value is 3-5, and the ultrasonic air flow rate is 20-40m 3 / h, reaction time 1 to 3h.
[0038] In step 5, solid-liquid separation is carried out in any filtering equipment such as a filter press or a filter.
[0039] In step six, the washing method is one of stirring washing, vacuum filtration washing or plate and frame washing, the water used for the first washing is the recovered liquid obtained from the second washing of iron slag, and the water used for the second washing is tap water.
[0040] In step 1, concentrated hydrochloric acid within a specific concentration range is selected to wet the re-washed slag in a specific proportion and is left for a certain period of time. The purpose of this operation is to allow the hydrochloric acid to fully penetrate into the microstructure of the iron slag and react initially with the compounds therein. Through this pretreatment, subsequent chemical reactions can proceed more fully and rapidly, thereby improving the leaching efficiency of rare earth elements.
[0041] The solid-liquid ratio in step two is determined through research and practice. The appropriate solid-liquid ratio can provide an ideal environment for the chemical reaction, ensure sufficient contact and uniform mixing of the reactants, avoid insufficient or excessive local reactions, and thus ensure the stability and consistency of the entire reaction process.
[0042] In step three, the reaction time of concentrated hydrochloric acid is controlled within 2 to 4 hours. This is to ensure sufficient reaction while avoiding excessive reaction that leads to waste of resources and increases the difficulty of subsequent treatment. During this period, hydrochloric acid can effectively react with the target components in the re-washing slag to gradually dissolve the rare earth elements into the solution.
[0043] In step four, raising the temperature to 80-100°C can increase the thermal motion speed of molecules, increase reaction activity, and accelerate the chemical reaction. Ultrasonic vibration can break the diffusion layer on the surface of the material, promote the transfer and reaction of the material, and greatly improve the leaching speed and leaching rate of rare earth elements. At the same time, by accurately adjusting the pH value to 3-5, the reaction conditions can be optimized so that the rare earth elements exist in a form that is more conducive to subsequent separation and extraction.
[0044] The solid-liquid separation operation in step five uses filtering equipment, which can achieve solid-liquid separation efficiently and accurately, ensuring that the obtained feed liquid and filtered iron slag have high purity and quality.
[0045] The two water washing treatments in step six are to further remove the rare earth elements and impurities remaining in the iron slag. The rational use of recycled liquid and tap water for step-by-step washing not only saves water resources, but also minimizes the emission of pollutants, achieving a green and environmentally friendly treatment process.
[0046] The following is an introduction in conjunction with specific embodiments:
[0047] Embodiment 1:
[0048] The REO content of the acid leaching residue reaches 0.6%. Compared with the traditional hydrochloric acid leaching process, the rare earth in the acid leaching residue after the final secondary washing can be reduced to 0.2%, which greatly improves the recovery efficiency and reduces the rare earth loss. The specific steps are as follows:
[0049] Wet the dried rewash residue with concentrated hydrochloric acid at an acid-to-solid ratio of 1:20 (hydrochloric acid concentration is 6N), and then leave it for 3 days;
[0050] The washed residue after placement is slurried according to a certain solid-liquid ratio of 1:1;
[0051] Add concentrated hydrochloric acid to the slurry for 2 hours;
[0052] The solid and liquid are heated to 80°C, and an ultrasonic oxidizer is used to vibrate the material. The ultrasonic air flow rate is 20m 3 / h, reaction time 1h, and adding liquid alkali to adjust the pH value to 3;
[0053] The adjusted material is subjected to solid-liquid separation, and a filter press is used to obtain the liquid material and the iron slag after filtration;
[0054] The filtered iron slag is washed twice with water, and low-concentration rare earth liquid and unqualified iron slag are obtained after the two washings. The washing method adopts stirring washing.
[0055] Embodiment 2:
[0056] The REO content of the acid leaching residue reaches 1.0%. Compared with the traditional hydrochloric acid leaching process, the rare earth in the acid leaching residue after the final secondary washing can be reduced to 0.3%, which greatly improves the recovery efficiency and reduces the loss of rare earth. The specific steps are as follows:
[0057] Wet the dried rewash residue with concentrated hydrochloric acid at an acid-to-solid ratio of 1:40 (hydrochloric acid concentration of 10N), and then leave it for 5 days;
[0058] The rewashed residue after placement is slurried according to a certain solid-liquid ratio of 1:3;
[0059] Add concentrated hydrochloric acid to the slurry for 4 hours;
[0060] The solid and liquid are heated to 100°C, and an ultrasonic oxidizer is used to vibrate the material. The ultrasonic air flow rate is 40m 3 / h, reaction time 3h, and adding liquid alkali to adjust the pH value to 5;
[0061] The adjusted material is subjected to solid-liquid separation, and a filter is used to obtain the liquid material and the filtered iron slag;
[0062] The filtered iron slag is washed twice with water, and low-concentration rare earth liquid and unqualified iron slag are obtained after the two washings. The washing method adopts vacuum filtration washing.
[0063] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for rewashing NdFeB waste acid leaching iron slag, characterized in that: The following steps are involved: Step 1: Wetting the dried re-washing residue with concentrated hydrochloric acid in a certain proportion, and then leaving it for a period of time; Step 2: slurry the washed residue after placement according to a certain solid-liquid ratio; Step 3, adding concentrated hydrochloric acid to the slurry to react for several hours; Step 4: The material is heated, an ultrasonic oxidizer is used to vibrate the material to accelerate the leaching of rare earth elements in the rewashed slag, and liquid alkali is added to adjust the pH value; Step 5, performing solid-liquid separation on the adjusted material to obtain feed liquid and filtered iron slag; Step 6: Wash the filtered iron slag twice with water to obtain a low-concentration rare earth liquid and unqualified iron slag.
2. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step 1, the rewashed slag is the filter press slag leached after high-temperature calcination of NdFeB waste.
3. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step 1, the mass ratio of the concentrated hydrochloric acid to the rewashing residue is (1:20) to (1:40).
4. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step 1, the re-washed residue is left to stand for a period of time, specifically 5 to 10 days, after being wetted.
5. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step 2, the solid-liquid ratio of the slurry is 1:(1-3).
6. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step 1 and the step 3, the concentration of the concentrated hydrochloric acid is 6 to 10 mol / L. In the step 3, the reaction of the concentrated hydrochloric acid is 2 to 4 hours.
7. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step 4, the heating temperature is 80-100°C, the pH value is 3-5, and the ultrasonic air flow rate of the ultrasonic oxidizer is 20-40m 3 / h, reaction time 1 to 3h.
8. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step 5, the solid-liquid separation is carried out in any filtering equipment such as a filter press or a filter.
9. The method for rewashing NdFeB waste acid leaching iron slag according to claim 1, characterized in that: In the step six, the washing method is one of stirring washing, vacuum filtration washing or plate and frame washing, the water used for the first washing is the recovered liquid obtained from the second washing of iron slag, and the water used for the second washing is tap water.