Method for removing sulfuric acid and inhibiting dissolution of rare earth sulfate in acid leaching residue

Abstract

The application discloses a method for removing sulfuric acid in pulping acid leaching residue and inhibiting dissolution of rare earth sulfate, and belongs to the technical field of hydrometallurgy. The acid leaching residue is subjected to N-1 (N is an integer) stage washing, and the Nth stage washing is performed by using a rare earth sulfate water leaching solution; after the washing is completed, the acid leaching residue is subjected to water leaching to obtain the rare earth sulfate water leaching solution and water leaching residue. The hydrogen ion concentration in the washing water after the first stage washing is greater than 12 mol / L, the REO content is less than 8 g / L, and the hydrogen ion concentration in the rare earth sulfate water leaching solution is controlled to be below 0.2 mol / L. Compared with direct washing, the use efficiency of production water is improved, water consumption is saved, the washing water consumption is reduced by more than 50%, the last stage is washed by the rare earth sulfate water leaching solution, dissolution of rare earth sulfate in the acid leaching residue is inhibited, hole formation is prevented, and the acid leaching residue is fully washed.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for removing sulfuric acid from pulping acid leaching residue and inhibiting the dissolution of rare earth sulfate. Background Technology

[0002] The sulfuric acid slurry process involves reacting rare earth minerals with a 40%-85% sulfuric acid solution at 100℃-180℃. After the reaction, the mixture is filtered, and the filter residue is leached with water to obtain a rare earth sulfuric acid leachate. This process decomposes fluorine-containing rare earth mineral particles through a liquid-solid phase mixing reaction at relatively low temperatures, achieving rapid decomposition of these particles. The reaction is easy to control and has broad application prospects. Furthermore, the sulfuric acid does not decompose at low temperatures, reducing sulfuric acid consumption. However, the filtered slurry yields acid leaching residue and acid leaching solution. The acid leaching residue contains a high concentration of residual sulfuric acid. To ensure that the hydrogen ion concentration in the rare earth sulfuric acid leachate is <0.1mol / L, fresh water is needed to wash away the residual sulfuric acid in the acid leaching residue, thus generating a large amount of acid washing wastewater and increasing wastewater treatment costs. Summary of the Invention

[0003] The purpose of this invention is to provide a method for removing sulfuric acid from pulping acid leaching residue and inhibiting the dissolution of rare earth sulfuric acid, so as to solve the problems existing in the prior art.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] One of the technical solutions of the present invention is a method for removing sulfuric acid from pulping acid leaching residue and inhibiting the dissolution of rare earth sulfuric acid, comprising the following steps:

[0006] (1) Mix rare earth concentrate with sulfuric acid solution and heat to react. After the reaction is completed, filter the slurry to obtain acid leaching solution and acid leaching residue.

[0007] (2) Use Grade 1 wash water to wash the acid leaching residue for the first time. After washing, combine the wash water with the acid leaching solution, add sulfuric acid, and continue to react with rare earth concentrate.

[0008] (3) Then, the acid leaching residue that has been washed in the first wash is washed a second time using 2-stage wash water. After the washing is completed, the wash water enters the 1-stage wash water tank as 1-stage wash water.

[0009] (4) In this way, the acid leaching residue after the N-2th washing is washed with N-1 grade wash water, and the wash water after washing enters the N-2 grade wash water tank as N-2 grade wash water.

[0010] (5) The acid leaching residue after the N-1 wash is washed for the Nth time using rare earth sulfuric acid leaching solution. After the washing is completed, it enters the N-1 grade washing water tank as the N-1 grade washing water.

[0011] (6) Add 8-12 times the amount of water to the acid leaching residue after the Nth washing and leach it to obtain rare earth sulfate water leaching solution and water leaching residue.

[0012] N is an integer, and N≥4.

[0013] Based on the above technical solution, the present invention has the following technical effects:

[0014] (1) Compared with direct washing, it improves the efficiency of production water use, saves water, and reduces washing water consumption by more than 50%.

[0015] (2) The sulfuric acid concentration in the wash water was significantly increased. The hydrogen ion concentration in the wash water after the first wash was greater than 12 mol / L, which can be directly reused in the reaction.

[0016] (3) The final washing is performed with rare earth sulfate solution to inhibit the dissolution of rare earth sulfate in the acid leaching residue, prevent the formation of pores, and ensure that the acid leaching residue is thoroughly washed. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the technical solution for removing sulfuric acid from pulping acid leaching residue and inhibiting the dissolution of rare earth sulfuric acid. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0025] This invention provides a method for removing sulfuric acid from pulping acid leaching residue and inhibiting the dissolution of rare earth elements in sulfuric acid, comprising the following steps:

[0026] (1) Mix rare earth concentrate with sulfuric acid solution and heat to react. After the reaction is completed, filter the slurry to obtain acid leaching solution and acid leaching residue.

[0027] (2) Use Grade 1 wash water to wash the acid leaching residue for the first time. After washing, combine the wash water with the acid leaching solution, add sulfuric acid, and continue to react with rare earth concentrate.

[0028] (3) Then, the acid leaching residue that has been washed in the first wash is washed a second time using 2-stage wash water. After the washing is completed, the wash water enters the 1-stage wash water tank as 1-stage wash water.

[0029] (4) In this way, the acid leaching residue after the N-2th washing is washed with N-1 grade wash water, and the wash water after washing enters the N-2 grade wash water tank as N-2 grade wash water.

[0030] (5) The acid leaching residue that has been washed N-1 times is washed N times with rare earth sulfuric acid leaching solution I. After washing, it enters the N-1 level washing water tank as N-1 level washing water.

[0031] (6) Add 8-12 times the amount of water to the acid leaching residue after the Nth washing and leach it to obtain rare earth sulfate water leaching solution II and water leaching residue;

[0032] N is an integer, and N≥4.

[0033] In some specific implementations, the heating reaction is carried out at a temperature of 100–180°C for a duration of 1–4 hours.

[0034] In some specific implementations, the concentration of rare earth oxides (REO) in the rare earth sulfate aqueous leaching solution I is >30 g / L.

[0035] In some specific implementation schemes, the hydrogen ion concentration in rare earth sulfate aqueous leaching solution II is no higher than 0.2 mol / L.

[0036] In some specific implementations, the mass ratio of the rare earth sulfate aqueous leaching solution I to the leaching residue from the Nth wash is (0.2-0.6):1.

[0037] In some specific implementation schemes, the hydrogen ion concentration in the wash water after the first wash is >12mol / L, and the REO content is <8g / L.

[0038] In some specific implementation schemes, for every 0.1 mol / L increase in hydrogen ion concentration in rare earth sulfate aqueous leaching solution II, the volume of rare earth sulfate aqueous leaching solution I is increased by 0.1 times.

[0039] Rare earth sulfate aqueous leaching solution I is a rare earth sulfate solution, which is a conventional product in this field; when the hydrogen ion concentration in rare earth sulfate aqueous leaching solution II is less than 0.2 mol / L, it can be used as rare earth sulfate aqueous leaching solution I.

[0040] In this invention, the acid leaching residue is washed for the last time with a high-concentration rare earth sulfate aqueous leaching solution. Based on the solubility properties of rare earth sulfate, this method ensures the washing efficiency of sulfuric acid in the acid leaching residue and also solves the problem of excessive dissolution of rare earth sulfate in the acid leaching residue.

[0041] Example 1

[0042] 600 kg of rare earth concentrate was mixed with 2.4 m 3 After the sulfuric acid solution is mixed and heated to 140°C for 2 hours, the slurry is then fed into a filter press for filtration to obtain acid leaching solution and acid leaching residue, which are then washed in four stages.

[0043] (1) Use Grade 1 washing water to wash the acid leaching residue for the first time. After washing, combine the washing water and acid leaching solution to supplement sulfuric acid and continue to react the rare earth concentrate.

[0044] (2) The acid leaching residue is washed a second time using second-stage wash water. After the washing is completed, the wash water enters the first-stage wash water tank as first-stage wash water.

[0045] (3) The acid leaching residue is washed a third time using three-stage washing water. The washing water after washing enters the two-stage washing water tank as the second-stage washing water.

[0046] (4) The acid leaching residue was washed for the fourth time using rare earth sulfate water leaching solution I (REO concentration 35g / L, hydrogen ion concentration 0.06mol / L). The amount of water added was 0.4 times that of the acid leaching residue in the fourth wash. After washing, the water entered the 3rd stage washing tank as the 3rd stage washing water.

[0047] The final hydrogen ion concentration in the wash water after the first wash was 18.1 mol / L, and the REO content was 1.3 g / L. After washing, a 4.8 m... 3 Water was used for leaching, and the hydrogen ion concentration in rare earth sulfate aqueous leaching solution II was 0.31 mol / L.

[0048] Example 2

[0049] 600 kg of rare earth concentrate was mixed with 2.4 m 3 After the sulfuric acid solution is mixed and heated to 140°C for 1 hour, the slurry is then fed into a filter press for filtration to obtain acid leaching solution and acid leaching residue, which are then washed in four stages.

[0050] (1) Use Grade 1 washing water to wash the acid leaching residue for the first time. After washing, combine the washing water and acid leaching solution to supplement sulfuric acid and continue to react the rare earth concentrate.

[0051] (2) The acid leaching residue is washed a second time using second-stage wash water. After the washing is completed, the wash water enters the first-stage wash water tank as first-stage wash water.

[0052] (3) The acid leaching residue is washed a third time using three-stage washing water. The washing water after washing enters the two-stage washing water tank as the second-stage washing water.

[0053] (4) The acid leaching residue was washed for the fourth time using rare earth sulfate water leaching solution I (REO concentration 35g / L, hydrogen ion concentration 0.06mol / L). The amount of washing water added was 0.6 times that of the acid leaching residue. After washing, the washing water entered the 3rd stage washing water tank as the 3rd stage washing water.

[0054] The final hydrogen ion concentration in the wash water after the first wash was 12.6 mol / L, and the REO content was 3.4 g / L. After washing, a 4.8 m... 3 Water was used for leaching, and the hydrogen ion concentration in rare earth sulfate aqueous leaching solution II was 0.16 mol / L.

[0055] Based on Example 1, the amount of water in rare earth sulfate aqueous leaching solution I was increased from 0.4 times to 0.6 times, and the hydrogen ion concentration in rare earth sulfate aqueous leaching solution II could be reduced to below 0.2 mol / L.

[0056] Example 3

[0057] 600 kg of rare earth concentrate was mixed with 2.4 m 3 After the sulfuric acid solution is mixed and heated to 140°C for 3 hours, the slurry is then fed into a filter press for filtration to obtain acid leaching solution and acid leaching residue, which are then washed in 6 stages.

[0058] (1) Use Grade 1 washing water to wash the acid leaching residue for the first time. After washing, combine the washing water and acid leaching solution to supplement sulfuric acid and continue to react the rare earth concentrate.

[0059] (2) The acid leaching residue is washed a second time using second-stage wash water. After the washing is completed, the wash water enters the first-stage wash water tank as first-stage wash water.

[0060] (3) The acid leaching residue is washed a third time using three-stage washing water. The washing water after washing enters the two-stage washing water tank as the second-stage washing water.

[0061] (4) The acid leaching residue is washed for the fourth time using 4-stage washing water. After the washing is completed, the washing water enters the 3-stage washing water tank as the 3-stage washing water.

[0062] (5) The acid leaching residue is washed for the fifth time using 5-stage wash water. After the washing is completed, the wash water enters the 4-stage wash water tank as 4-stage wash water.

[0063] (6) The acid leaching residue was washed for the sixth time using rare earth sulfate water leaching solution I (REO concentration 30g / L, hydrogen ion concentration 0.08mol / L). The amount of washing water added was 0.4 times that of the acid leaching residue. After washing, the washing water entered the 5th stage washing water tank as the 5th stage washing water.

[0064] The final hydrogen ion concentration in the wash water after the first wash was 13.7 mol / L, and the REO content was 2.6 g / L. After washing, a 4.8 m... 3 Water was used for leaching, and the hydrogen ion concentration in rare earth sulfate aqueous leaching solution II was 0.14 mol / L.

[0065] By increasing the number of washing stages, the amount of washing water required for the rare earth sulfate leaching solution I can be reduced, thus achieving the technical effect of this invention.

[0066] Example 4

[0067] 600 kg of rare earth concentrate was mixed with 2.4 m 3 After the sulfuric acid solution is mixed and heated to 140°C for 4 hours, the slurry is then fed into a filter press for filtration to obtain acid leaching solution and acid leaching residue, which are then washed in 8 stages.

[0068] (1) Use Grade 1 washing water to wash the acid leaching residue for the first time. After washing, combine the washing water and acid leaching solution to supplement sulfuric acid and continue to react the rare earth concentrate.

[0069] (2) The acid leaching residue is washed a second time using second-stage wash water. After the washing is completed, the wash water enters the first-stage wash water tank as first-stage wash water.

[0070] (3) The acid leaching residue is washed a third time using three-stage washing water. The washing water after washing enters the two-stage washing water tank as the second-stage washing water.

[0071] (4) The acid leaching residue is washed for the fourth time using 4-stage washing water. After the washing is completed, the washing water enters the 3-stage washing water tank as the 3-stage washing water.

[0072] (5) The acid leaching residue is washed for the fifth time using 5-stage wash water. After the washing is completed, the wash water enters the 4-stage wash water tank as 4-stage wash water.

[0073] (6) The acid leaching residue is washed for the sixth time using 6-stage wash water. The wash water after washing is then transferred to the 5-stage wash water tank as 5-stage wash water.

[0074] (7) The acid leaching residue is washed for the seventh time using 7-stage washing water. The washing water after washing enters the 6-stage washing water tank as 6-stage washing water.

[0075] (8) The acid leaching residue was washed for the tenth time using rare earth sulfate water leaching solution I (REO concentration 35g / L, hydrogen ion concentration 0.06mol / L). The amount of washing water added was 0.2 times that of the acid leaching residue. After washing, the washing water entered the 7th stage washing water tank as the 7th stage washing water.

[0076] The final hydrogen ion concentration in the wash water after the first wash was 15.2 mol / L, and the REO content was 1.9 g / L. After washing, a 4.8 m... 3 Water was used for leaching, and the hydrogen ion concentration in rare earth sulfate aqueous leaching solution II was 0.18 mol / L.

[0077] Comparative Example 1

[0078] 600 kg of rare earth concentrate was mixed with 2.4 m 3 After the sulfuric acid solution is mixed and heated to 140°C for 2 hours, the slurry is then fed into a filter press for filtration to obtain acid leaching solution and acid leaching residue. Fresh water is used to wash the acid leaching residue, with the amount of fresh water added being 0.5 times that of the acid leaching residue. The wash water is then placed into a washing tank.

[0079] The hydrogen ion concentration in the wash water was 16.2 mol / L, and the REO content was 1.9 g / L. After washing, a 4.8 m... 3 The rare earth sulfate solution was leached with water, and the hydrogen ion concentration in the leaching solution was 4.3 mol / L.

[0080] Compared with the technology of this invention, the method of washing with fresh water without using countercurrent washing fails to fully wash the sulfuric acid in the acid leaching residue with the same amount of washing water, resulting in a higher concentration of hydrogen ions in the rare earth sulfuric acid leaching solution.

[0081] Comparative Example 2

[0082] 600 kg of rare earth concentrate was mixed with 2.4 m 3 After mixing with sulfuric acid solution and heating to 140°C for 2 hours, the slurry is then fed into a filter press for filtration to obtain acid leaching solution and acid leaching residue. The acid leaching residue is washed with fresh water at a ratio of 1.2 times that of the acid leaching residue, and the wash water is then placed in a washing tank.

[0083] The hydrogen ion concentration in the wash water was 10.2 mol / L, and the REO content was 10.5 g / L. After washing, a 4.8 m... 3 The rare earth sulfate solution was leached with water, and the hydrogen ion concentration in the leaching solution was 0.13 mol / L.

[0084] Compared with Example 1, to obtain the same rare earth sulfate water leaching solution, the amount of washing water needs to be greatly increased, which is about 1.5-2 times that of the present invention. In addition, the concentration of rare earth sulfate in the washing water is higher, and some rare earth sulfate in the acid leaching residue dissolves into the washing water, resulting in the loss of rare earth sulfate.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for removing sulfuric acid from pulping acid leaching residue and inhibiting the dissolution of rare earth sulfuric acid, characterized in that, Includes the following steps: (1) Mix rare earth concentrate with sulfuric acid solution and heat to react. After the reaction is completed, filter the slurry to obtain acid leaching solution and acid leaching residue. (2) The acid leaching residue was washed for the first time with first-grade wash water. After the washing was completed, the wash water and acid leaching solution were combined, sulfuric acid was added, and the reaction with rare earth concentrate continued. (3) Then, the acid leaching residue after the first washing is washed a second time using second-stage wash water. After the washing is completed, the wash water enters the first-stage wash water tank as the first-stage wash water. (4) In this way, the acid leaching residue after the N-2th washing is washed with N-1 grade wash water, and the wash water after washing enters the N-2 grade wash water tank as N-2 grade wash water. (5) The acid leaching residue that has been washed N-1 times is washed for the Nth time using rare earth sulfate water leaching solution I. After washing, it is put into the N-1 level washing water tank as the N-1 level washing water. The REO concentration in the rare earth sulfate water leaching solution I is >30g / L. The mass ratio of the rare earth sulfate water leaching solution I to the acid leaching residue washed N times is (0.2~0.6):

1. (6) Add 8-12 times the amount of water to the acid leaching residue after the Nth washing and leach it to obtain rare earth sulfate water leaching solution II and water leaching residue; the hydrogen ion concentration in rare earth sulfate water leaching solution II is not higher than 0.2 mol / L; for every 0.1 mol / L increase in the hydrogen ion concentration in rare earth sulfate water leaching solution II, the amount of water in rare earth sulfate water leaching solution I is increased by 0.1 times; N is an integer, and N≥4.

2. The method according to claim 1, characterized in that, The heating reaction is carried out at a temperature of 100~180 ℃ for a time of 1~4 h.

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