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

Abstract

The invention discloses a method for removing sulfuric acid in pulpified acid leaching residues and inhibiting dissolution of rare earth sulfate, and belongs to the technical field of hydrometallurgy. The acid leaching residues are subjected to N-1 (N is an integer)-level washing, the sulfuric acid rare earth water leaching liquid is adopted for washing for the Nth time, and after washing is finished, the acid leaching residues are subjected to water leaching to obtain the sulfuric acid rare earth water leaching liquid and water leaching residues. The hydrogen ion concentration in the washing water after the first washing is more than 12mol / L, the REO content is less than 8g / L, and the hydrogen ion concentration in the sulfuric acid rare earth water immersion liquid is controlled to be below 0.2 mol / L. Compared with direct washing, the use efficiency of production water is improved, water is saved, the use amount of washing water is reduced by more than 50%, the rare earth sulfate water leaching liquid is used for washing in the last stage, rare earth sulfate in the acid leaching residues is inhibited from being dissolved, holes are prevented from being formed, and the acid leaching residues are fully washed.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a method for removing sulfuric acid from slurry acid leaching residue and inhibiting the dissolution of rare earth sulfate. Background Art

[0002] The sulfate pulping process uses 40%-85% sulfuric acid solution to react with rare earth minerals at 100℃~180℃, and then filters after the reaction. The filter residue is leached in water to obtain a sulfate rare earth leaching solution. This process decomposes fluorine-containing rare earth mineral particles through liquid-solid phase mixed reaction at a relatively low temperature, achieving rapid decomposition of fluorine-containing rare earth mineral particles. The reaction is easy to control and has broad application prospects. In addition, sulfuric acid does not decompose in low-temperature reactions, which reduces sulfuric acid consumption. However, after the pulp is filtered, it becomes acid leaching residue and acid leaching solution. A high concentration of sulfuric acid remains in the acid leaching residue. In order to ensure that the hydrogen ion concentration in the sulfate rare earth leaching solution is less than 0.1mol / L, new water is needed to wash the sulfuric acid remaining in the acid leaching residue, thereby generating a large amount of acid washing wastewater, which increases the cost of wastewater treatment. Summary of the invention

[0003] The object of the present invention is to provide a method for removing sulfuric acid from slurry acid leaching residue and inhibiting the dissolution of rare earth sulfate, so as to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides the following solutions:

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

[0006] (1) mixing rare earth concentrate and sulfuric acid solution and heating them for reaction, filtering the slurry after the reaction to obtain acid leaching solution and acid leaching residue;

[0007] (2) The acid leaching residue is washed for the first time with the first-grade washing water. After the washing, the washing water is combined with the acid leaching solution, and sulfuric acid is added to continue to react with the rare earth concentrate;

[0008] (3) The acid leaching residue after the first washing is then washed for the second time with the second-level washing water. After the washing is completed, the washing water enters the first-level washing water tank as the first-level washing water;

[0009] (4) Similarly, the acid leaching residue that has been washed for the N-2th time is washed for the N-1th time using the N-1th level washing water, and the washing water enters the N-2th level washing water tank as the N-2th level washing water;

[0010] (5) The acid leaching residue after the N-1th washing is washed for the Nth time with rare earth sulfate aqueous solution, and after the washing is completed, it enters the N-1th level washing water tank as the N-1th level washing water;

[0011] (6) adding 8-12 times of water to the acid leaching residue after the Nth washing to carry out leaching, thereby obtaining a 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 utilization efficiency of production water, saves water, and reduces the amount of washing water by more than 50%.

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

[0016] (3) The last washing step is performed by washing with rare earth sulfate aqueous solution to inhibit the dissolution of rare earth sulfate in the acid leaching residue, prevent the formation of holes, and ensure that the acid leaching residue is fully washed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The present invention is a flow chart of the technical solution for removing sulfuric acid from slurry acid leaching residue and inhibiting the dissolution of rare earth sulfate. DETAILED DESCRIPTION

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

[0020] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0021] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0022] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

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

[0024] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0025] The embodiment of the present invention provides a method for removing sulfuric acid from slurry acid leaching residue and inhibiting the dissolution of rare earth sulfate, comprising the following steps:

[0026] (1) mixing rare earth concentrate and sulfuric acid solution and heating them for reaction, and after the reaction, filtering the slurry to obtain acid leaching solution and acid leaching residue;

[0027] (2) The acid leaching residue is washed for the first time with the first-grade washing water. After the washing, the washing water is combined with the acid leaching solution, and sulfuric acid is added to continue to react with the rare earth concentrate;

[0028] (3) The acid leaching residue after the first washing is then washed for the second time with the second-level washing water. After the washing is completed, the washing water enters the first-level washing water tank as the first-level washing water;

[0029] (4) Similarly, the acid leaching residue that has been washed for the N-2th time is washed for the N-1th time using the N-1th level washing water, and the washing water enters the N-2th level washing water tank as the N-2th level washing water;

[0030] (5) The acid leaching residue after the N-1th washing is washed for the Nth time using rare earth sulfate aqueous solution I, and after the washing is completed, it enters the N-1th level washing water tank as the N-1th level washing water;

[0031] (6) adding 8-12 times of water to the acid leaching residue after the Nth washing to carry out leaching, thereby obtaining rare earth sulfate water leaching solution II and water leaching residue;

[0032] N is an integer, and N≥4.

[0033] In some specific embodiments, the heating reaction is carried out at a temperature of 100 to 180° C. and for a time of 1 to 4 hours.

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

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

[0036] In some specific embodiments, the mass ratio of the rare earth sulfate water extract I to the Nth washing residue is (0.2-0.6):1.

[0037] In some specific embodiments, the hydrogen ion concentration in the washing water after the first washing is greater than 12 mol / L, and the REO content is less than 8 g / L.

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

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

[0040] In the present invention, the acid leaching residue is washed for the last time by a high concentration rare earth sulfate aqueous solution. According to the solubility property of rare earth sulfate, the washing efficiency of sulfuric acid in the acid leaching residue is ensured, and the problem of excessive dissolution of rare earth sulfate in the acid leaching residue is solved.

[0041] Example 1

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

[0043] (1) The acid leaching residue is washed for the first time with first-grade washing water, and after washing, the washing water is combined with the acid leaching solution to add sulfuric acid to continue to react with the rare earth concentrate;

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

[0045] (3) The acid leaching residue is washed for the third time with the 3rd-level washing water, and the washing water enters the 2nd-level washing water tank as the 2nd-level washing water;

[0046] (4) Rare earth sulfate aqueous solution I (REO concentration 35 g / L, hydrogen ion concentration 0.06 mol / L) is used as washing water to wash the acid leaching residue for the fourth time. The amount of washing water added is 0.4 times the acid leaching residue of the fourth washing. After washing, the washing water enters the 3rd washing water tank as the 3rd washing water.

[0047] The final hydrogen ion concentration in the washing water after the first washing was 18.1 mol / L and the REO content was 1.3 g / L. After the washing was completed, 4.8 m 3 The rare earth sulfate water extract II was leached with water, and the hydrogen ion concentration was 0.31 mol / L.

[0048] Example 2

[0049] 600 kg of rare earth concentrate and 2.4 m 3 The sulfuric acid solution was mixed and heated to 140°C for reaction for 1 hour. After the reaction, the slurry was pumped into a filter press for filtration to obtain acid leaching solution and acid leaching residue, which were washed in 4 stages.

[0050] (1) The acid leaching residue is washed for the first time with first-grade washing water, and after washing, the washing water is combined with the acid leaching solution to add sulfuric acid to continue to react with the rare earth concentrate;

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

[0052] (3) The acid leaching residue is washed for the third time with the 3rd-level washing water, and the washing water enters the 2nd-level washing water tank as the 2nd-level washing water;

[0053] (4) The acid leaching residue was washed for the fourth time using rare earth sulfate aqueous solution I (REO concentration 35 g / L, hydrogen ion concentration 0.06 mol / 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 level washing water tank as the 3rd level washing water.

[0054] The final hydrogen ion concentration in the washing water after the first washing was 12.6 mol / L and the REO content was 3.4 g / L. 3 The rare earth sulfate water extract II was leached with water, and the hydrogen ion concentration was 0.16 mol / L.

[0055] On the basis of Example 1, the water volume of rare earth sulfate water extract I is increased from 0.4 times to 0.6 times, and the hydrogen ion concentration in rare earth sulfate water extract II can be reduced to below 0.2 mol / L.

[0056] Example 3

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

[0058] (1) The acid leaching residue is washed for the first time with first-grade washing water, and after washing, the washing water is combined with the acid leaching solution to add sulfuric acid to continue to react with the rare earth concentrate;

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

[0060] (3) The acid leaching residue is washed for the third time with the 3rd-level washing water, and the washing water enters the 2nd-level washing water tank as the 2nd-level washing water;

[0061] (4) The acid leaching residue is washed for the fourth time with 4-level washing water, and after washing, the washing water enters the 3-level washing water tank as 3-level washing water;

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

[0063] (6) The acid leaching residue was washed for the sixth time using rare earth sulfate aqueous solution I (REO concentration 30 g / L, hydrogen ion concentration 0.08 mol / 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 level washing water tank as the 5th level washing water.

[0064] The final hydrogen ion concentration in the washing water after the first washing was 13.7 mol / L and the REO content was 2.6 g / L. 3 The rare earth sulfate water extract II was leached with water, and the hydrogen ion concentration was 0.14 mol / L.

[0065] By increasing the number of washing stages, the amount of washing water of the rare earth sulfate water leaching solution I can be reduced, and the technical effect of the present invention can be achieved.

[0066] Example 4

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

[0068] (1) The acid leaching residue is washed for the first time with first-grade washing water, and after washing, the washing water is combined with the acid leaching solution to add sulfuric acid to continue to react with the rare earth concentrate;

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

[0070] (3) The acid leaching residue is washed for the third time with the 3rd-level washing water, and the washing water enters the 2nd-level washing water tank as the 2nd-level washing water;

[0071] (4) The acid leaching residue is washed for the fourth time with 4-level washing water, and after washing, the washing water enters the 3-level washing water tank as 3-level washing water;

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

[0073] (6) The acid leaching residue is washed for the sixth time using the 6th-level washing water, and the washing water enters the 5th-level washing water tank as the 5th-level washing water.

[0074] (7) The acid leaching residue is washed for the seventh time using the 7th-level washing water, and the washing water enters the 6th-level washing water tank as the 6th-level washing water;

[0075] (8) The acid leaching residue was washed for the tenth time using rare earth sulfate aqueous solution I (REO concentration 35 g / L, hydrogen ion concentration 0.06 mol / 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-level washing water tank as the 7th-level washing water.

[0076] The final hydrogen ion concentration in the washing water after the first washing was 15.2mol / L and the REO content was 1.9g / L. 3 The rare earth sulfate water extract II was leached with water, and the hydrogen ion concentration was 0.18 mol / L.

[0077] Comparative Example 1

[0078] 600 kg of rare earth concentrate and 2.4 m 3 The sulfuric acid solution is mixed and heated to 140°C for reaction for 2 hours. After the reaction is completed, the slurry is pumped into a filter press for filtration to obtain acid leaching solution and acid leaching residue. The acid leaching residue is washed with new water, and the amount of new water added is 0.5 times that of the acid leaching residue. After washing, the washing water enters the washing water tank.

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

[0080] Compared with the technology of the present invention, the countercurrent washing method is not adopted, and only new water is used for washing. The same amount of washing water cannot fully wash the sulfuric acid in the acid leaching residue, resulting in a higher hydrogen ion concentration in the rare earth sulfate water leaching solution.

[0081] Comparative Example 2

[0082] 600 kg of rare earth concentrate and 2.4 m 3 The sulfuric acid solution is mixed and heated to 140°C for 2 hours. After the reaction is completed, the slurry is pumped into the filter press for filtration to obtain acid leaching liquid and acid leaching residue. The acid leaching residue is washed with new water, and the amount of new water added is 1.2 times that of the acid leaching residue. After washing, the washing water enters the washing water tank.

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

[0084] Compared with Example 1, to obtain the same effect of rare earth sulfate water leaching solution, the amount of washing water needs to be greatly increased. The amount of washing water is about 1.5-2 times that of the technology of the present invention, and the concentration of rare earth sulfate in the washing water is relatively high. Part of the 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 methods of the present invention. For ordinary technical users in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for removing sulfuric acid from slurry acid leaching residue and inhibiting the dissolution of rare earth sulfate, characterized in that: The following steps are involved: (1) mixing rare earth concentrate and sulfuric acid solution and heating them for reaction, filtering the slurry after the reaction to obtain acid leaching solution and acid leaching residue; (2) The acid leaching residue is washed for the first time with the first-grade washing water. After the washing, the washing water is combined with the acid leaching solution, and sulfuric acid is added to continue to react with the rare earth concentrate; (3) The acid leaching residue after the first washing is then washed for the second time with the second-level washing water. After the washing is completed, the washing water enters the first-level washing water tank as the first-level washing water; (4) Similarly, the acid leaching residue that has been washed for the N-2th time is washed for the N-1th time using the N-1th level washing water, and the washing water enters the N-2th level washing water tank as the N-2th level washing water; (5) The acid leaching residue after the N-1th washing is washed for the Nth time using rare earth sulfate aqueous solution I, and after the washing is completed, it enters the N-1th level washing water tank as the N-1th level washing water; (6) adding 8-12 times of water to the acid leaching residue after the Nth washing to carry out leaching, thereby obtaining rare earth sulfate water leaching solution II and water leaching residue; 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 to 180° C. and for a time of 1 to 4 hours.

3. The method according to claim 1, characterized in that The REO concentration in the rare earth sulfate water extract I is greater than 30 g / L.

4. The method according to claim 1, characterized in that: The hydrogen ion concentration in the rare earth sulfate aqueous solution II is not higher than 0.2 mol / L.

5. The method according to claim 1, characterized in that The mass ratio of the rare earth sulfate water extract I to the Nth washing residue is (0.2-0.6):

1.

6. The method according to claim 1, characterized in that When the concentration of hydrogen ions in the rare earth sulfate water extract II increases by 0.1 mol / L, the amount of water in the rare earth sulfate water extract I increases by 0.1 times.

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