CN117604281B - Method for promoting fluorine escape in rare earth ore concentrated sulfuric acid decomposition process - Google Patents

Abstract

The invention belongs to the technical field of rare earth hydrometallurgy, and discloses a method for promoting fluorine escape in a rare earth ore concentrated sulfuric acid decomposition process. Uniformly mixing the dried Bayan obo mixed rare earth concentrate or fluorine-containing rare earth concentrate such as bastnaesite and a fluorine conversion agent, adding 92% -98% concentrated sulfuric acid for mixed pulping, and carrying out sectional calcination reaction on the slurry; and detecting the conversion rate of fluorine in the roasted ore after the reaction is finished. The fluorine in the roasted ore was almost completely converted to SiF ₄. The method has the advantages of simple operation, low cost and high fluorine conversion rate, and the product SiF ₄ is easy to recycle and realize industrial production.

Description

A method for promoting fluorine release during the decomposition of rare earth ore in concentrated sulfuric acid

Technical Field

The invention belongs to the field of rare earth hydrometallurgy, relates to a method for promoting fluorine escape during the roasting process of rare earth ore, and specifically discloses a method for promoting fluorine escape during the decomposition process of rare earth ore with concentrated sulfuric acid.

Background technique

Fluorocarbonate cerium ore and Bayan Obo mixed rare earth ore are two rare earth minerals currently used in the rare earth metallurgical industry. Fluorocarbonate cerium ore can be expressed by the chemical formula REFCO ₃ or REF ₃ ·RE ₂ (CO ₃ ) _3. Mixed rare earth ore is a mixed ore of fluorocarbonate cerium ore and monazite. Monazite ore can be expressed by the chemical formula REPO ₄ .

Fluorocarbon cerium ore is easily decomposed by acid and alkali, but monazite ore has stable chemical properties and is difficult to decompose using general acid-base decomposition methods. At present, in industry, the oxidation roasting-hydrochloric acid leaching method is mainly used for single-type fluorocarbon cerium ore. The mineral is roasted at high temperature to decompose into rare earth oxides. A part of fluorine escapes in the form of HF gas, and another part of fluorine is retained in the roasting product in the form of rare earth fluoride (REF ₃ ) and rare earth fluoride oxide (REOF). During the hydrochloric acid leaching process, it enters the solution in the form of NaF; the Bayan Obo mixed rare earth concentrate mainly adopts concentrated sulfuric acid high-temperature roasting-water leaching process. During the roasting process, most of the fluorine will escape in the form of HF, a small part will escape in the form of SiF ₄ , and a trace amount of fluorine will enter the subsequent solution system. It is very difficult to separate the HF and SiF ₄ that enter the gas together, which increases production costs and reduces production efficiency.

After fluorine ions enter the solution system, they will continue to accumulate in the circulation system, resulting in increased concentration and serious corrosion to the equipment. Only by adding a decalcifying agent can part of the fluorine be removed, which not only increases the production cost, but also complicates the production process. At present, the research on fluorine in rare earth ores mainly focuses on the treatment of tail gas after roasting and the removal of fluorine in the solution system. For example, Chinese patent CN111285332A discloses an integrated method for decomposing fluorine-containing rare earth minerals and recovering hydrofluoric acid. Although high-concentration hydrofluoric acid can be recovered on the basis of ensuring a high fluorine decomposition rate, fluorine still escapes in the form of HF and _SiF4 mixed gas, which is difficult to separate. Chinese patent CN115927884A discloses a method for defluorinating rare earth ore leachate. Although it can be applied to defluorinating the leachate of fluorine-containing carbonate rare earth ore, oxalate rare earth ore, carbon grass mixed rare earth ore or oxide rare earth ore, it is only applicable to ionic rare earth ores.

There are currently no similar reports on the process design and related research content of promoting fluorine conversion during the decomposition of rare earth minerals with concentrated sulfuric acid.

Summary of the invention

In view of this, the purpose of the present invention is to provide a method for promoting fluorine escape during the decomposition process of rare earth ore with concentrated sulfuric acid, which is not only beneficial to the subsequent recovery of rare earth compounds, but also beneficial to the centralized and comprehensive recovery and utilization of fluorine resources, and has important application value for the green extraction of rare earths.

It should be noted that the purpose of adopting staged roasting + fluorine conversion agent in the present invention is to first remove excess moisture in the mineral, and then promote the conversion and escape of fluorine under the action of fluorine conversion agent and high temperature, so that all fluorine is converted into _SiF4 gas, which is beneficial to the comprehensive recovery and utilization of fluorine, and provides a new idea for the treatment of Bayan Obo mixed rare earth minerals and the recovery and utilization of fluorine.

Specifically, the method of the present invention is to select silicon-containing compounds that are both resistant to high temperatures and easy to combine with fluorine to promote the conversion of fluorine during the decomposition process of rare earth ore with concentrated sulfuric acid. The reaction process between fluorine-containing rare earth minerals and silicon-containing compounds is relatively complex and is not a conventional simple chemical reaction. Under the process conditions designed by the present invention, the fluorine element in the concentrate can eventually be converted into SiF _4. Through the unconventional reaction mechanism, the complex reaction is normalized, and the final fluorine conversion rate reaches more than 99.4%.

Furthermore, the process technology of the present invention is to convert almost all the fluorine into _SiF4 and enter the tail gas in the first step of the decomposition reaction. The overall process is simple to operate, the conversion rate of fluorine is high, and it does not affect the subsequent leaching and purification of rare earths; and the silicon-containing compound neither reacts with rare earth minerals and other impurities, nor reacts with concentrated sulfuric acid, and directly enters the solid slag after washing with water, which is of great significance to the green extraction of rare earths and the comprehensive utilization of fluorine resources.

In order to achieve the above object, the present invention provides the following technical solutions:

A method for promoting fluorine release during the decomposition of rare earth ore in concentrated sulfuric acid, the method specifically comprising the following steps:

The dried Bayan Obo mixed rare earth concentrate or fluorocarbon cerium ore is mixed evenly with a fluorine conversion agent at a fluorine-silicon molar ratio of 1: (1.5-3), and then 92%-98% concentrated sulfuric acid is added at a mineral acid mass ratio of 1: (1.2-1.6) to prepare a slurry; the slurry is subjected to a staged roasting reaction; after the reaction is completed, the fluorine conversion rate in the roasted ore is detected.

It should be noted that the present invention is to add a silicon-containing compound that is both resistant to high temperatures and easy to combine with fluorine to promote the conversion of fluorine while adding concentrated sulfuric acid to the rare earth concentrate for roasting. In this process, almost all of the fluorine enters the tail gas as _SiF4 , which is convenient for recycling. This not only avoids the complex process of mixed gas recovery, but also effectively prevents fluorine from entering the solution circulation system, avoiding fluorine corrosion on equipment and the impact of products. Through the process conditions of the present invention, fluorine is promoted to react with silicon in a complex reaction system, inhibiting the generation of HF, and all generating _SiF4 gas, which is convenient for centralized recycling at the back end, and has a high application value.

In addition, the heating and drying of the mixed rare earth concentrate or fluorocarbon cerium ore in Bayan Obo is to reduce the moisture in the mineral. The presence of water will cause some fluorides to react with water to generate HF gas, which will mix with SiF ₄ gas and be difficult to separate. Controlling the fluorine-silicon ratio between 1: (1.5-3) ensures that fluorine can fully react with excess silicon to generate SiF ₄ to escape. Controlling the mineral acid ratio of 1: (1.2-1.6) and adding 92%-98% concentrated sulfuric acid to mix and pulp can ensure that the rare earth ore is completely decomposed to release free fluoride ions. The rotary tube furnace uses steel pipes for heating in order to better imitate the working state of the rotary kiln. The staged roasting is to better remove the moisture brought in by the concentrated sulfuric acid so that the fluorine in the concentrate can completely generate SiF ₄ gas.

Moreover, the rare earth content (measured in _RE2O3 ) of the Bayan Obo mixed rare earth concentrate or fluorocarbon cerium ore is greater than 40%, and the aluminum content ( _measured in _Al2O3 ) is less than 0.1%. If the grade of the rare _earth ore is lower than 40%, the aluminum content will be too high. During the reaction process, silicon-containing compounds will easily react with aluminum-containing compounds to form colloidal products, which will adhere to the tube wall or the kiln wall of the rotary kiln to form rings, which will not only affect the conversion of fluorine, but also affect continuous production.

Optionally, the fluorine conversion agent is a single silicon-containing compound or a mixture that is both resistant to high temperatures and capable of reacting with fluorine.

Furthermore, the fluorine conversion agent includes at least one of SiO ₂ , SiC, SiN, and H ₂ SiO ₄ .

It should be noted that silicon-containing compounds such as SiO ₂ , SiC, SiN, H ₂ SiO ₄ , etc. are all compounds with very stable physical and chemical properties. They are selected because the above silicon-containing compounds will not participate in the reaction of concentrated sulfuric acid decomposing rare earth ores, and will only react with fluorine-containing compounds to generate SiF ₄ gas under appropriate temperature conditions.

Taking the addition of _SiO2 as an example, the chemical reaction formula is:

4REFCO ₃ +SiO ₂ =SiF ₄ ↑+4CO ₂ ↑+2RE ₂ O _3.

Moreover, the particle size requirement of Bayan Obo mixed rare earth concentrate or fluorocarbon cerium ore is that the mineral is under the 200 mesh sieve, and the particle size requirement of the silicon-containing compound is that the compound is under the 400 mesh sieve. The particle size of the silicon-containing compound is smaller than that of the mineral, so as to ensure that the fluorine-containing compound can fully react with the silicon-containing compound.

Optionally, the staged roasting reaction is performed as follows:

The mixture is calcined in a rotary tube furnace at 120-170°C for 30-120 min, and then calcined at 170-350°C for 60-180 min.

Furthermore, the rotation speed of the rotary tube furnace is 3 to 6 r/min.

It is worth noting that the roasting temperature in the rotary tube furnace is first controlled at 120-170°C to remove moisture brought in by the concentrate and concentrated sulfuric acid, and then controlled at 170-350°C. Under this temperature condition, the fluorine-containing compound and the silicon-containing compound can fully react chemically to completely generate _SiF4 gas.

Moreover, the rotation speed of the rotary tube furnace is controlled at 3-6 r/min. If the speed is too fast, the fluorine-containing compound is easy to generate HF gas and escape. Only within this speed range can the fluorine-containing compound and the silicon-containing compound be controlled to fully react chemically and completely generate _SiF4 gas.

It can be seen from the above technical solution that, compared with the prior art, the method for promoting fluorine release during the decomposition of rare earth ore in concentrated sulfuric acid provided by the present invention has the following excellent effects:

The method comprises the following steps: uniformly mixing the dried Bayan Obo mixed rare earth concentrate or bastnaesite with a fluorine conversion agent, then adding 92% to 98% concentrated sulfuric acid to mix and prepare a slurry, and subjecting the slurry to a staged calcination reaction; after the reaction is completed, the conversion rate of fluorine in the roasted ore is detected. It is found that almost all the fluorine in the roasted ore is converted into SiF ₄ . The method of the present invention is simple to operate, low in cost, and high in conversion rate of fluorine. Not only is the product SiF ₄ easy to recycle, but it is also easy to realize industrial production.

BRIEF DESCRIPTION OF THE DRAWINGS

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 or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

FIG1 is a process flow chart of the inventive method.

Detailed ways

The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments 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.

The embodiment of the invention discloses a method for promoting fluorine escape during the decomposition process of rare earth ore in concentrated sulfuric acid.

In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

Embodiment 1:

A -200 mesh dried Bayan _Obo mixed rare earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 45%, the fluorine content was 7.02%, _and the aluminum content (in terms of _Al2O3 ) was 0.06%. The ore was evenly mixed with -400 mesh _SiO2 powder at a fluorine-silicon molar ratio of 1:1.5, and then 96% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.4 to make a mixed pulp. The mixture was added into a rotary tube furnace steel tube and the speed was controlled at 3r/min. The mixture was first roasted at 150°C for 90min, and then roasted at 320°C for 70min. After the reaction was completed, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 99.6%.

Embodiment 2:

A -200 mesh dried Bayan _Obo mixed rare earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 50%, the fluorine content was 7.33%, and the aluminum content (in terms of _Al2O3 ) was 0.05%. The ore was evenly mixed with -400 mesh SiC powder at a fluorine-silicon molar ratio of 1: _1.4 , and then 98% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.5 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled at 4r/min. It was first roasted at 120°C for 120min, and then roasted at 300°C for 100min. After the reaction was completed, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 99.5%.

Embodiment 3:

A -200 mesh dried Bayan _Obo mixed rare earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 60%, the fluorine content was 6.12%, _and the aluminum content (in terms of _Al2O3 ) was 0.03%. The ore was evenly mixed with -400 mesh _SiO2 and SiN mixed powders at a fluorine-silicon molar ratio of 1:2, and then 92% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.6 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled at 6r/min. It was first roasted at 150°C for 100min, and then reacted at 350°C for 70min. After the reaction, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 99.6%.

Embodiment 4:

A -200 mesh dried fluorocarbon cerium rare _earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 70%, the fluorine content was 6.02%, _and the aluminum content (in terms of _Al2O3 ) was 0.08%. The ore was evenly mixed with -400 mesh _SiO2 powder at a fluorine-silicon molar ratio of 1:3, and then 95% concentrated sulfuric acid was added at a ore-acid mass ratio of 1:1.4 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled to be 5r/min. It was first roasted at 150°C for 90min, and then reacted at 200°C for 150min. After the reaction, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 99.5%.

Embodiment 5:

A -200 mesh dried fluorocarbon cerium rare earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 60%, the fluorine content was 7.03%, _and the aluminum content (in terms of _Al2O3 ) was 0.08%. The ore was evenly mixed with _a -400 mesh SiC and SiN mixed powder at a fluorine-silicon molar ratio of 1:3, and then 94% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.5 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled to be 6r/min. It was first roasted at 140°C for 100min, and then reacted at 340°C for 70min. After the reaction, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 99.7%.

Embodiment 6:

A -200 mesh dried fluorocarbon cerium rare earth concentrate was selected, in which the rare earth content ( _calculated as _RE2O3 ) was 50%, the fluorine content was _7.67 %, and the aluminum content ( _calculated as _Al2O3 ) was 0.07%. The ore was evenly mixed with _H2SiO4 at a fluorine-silicon molar ratio of 1:2.5, and then 98% concentrated sulfuric acid was added at a ore-acid mass ratio of 1:1.6 to make a mixed pulp. The ore was added into a rotary tube furnace steel tube and the speed was controlled at 4r/min. The ore was first roasted at 150°C for 90min, and then reacted at 260°C for 140min. After the reaction, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 99.3%.

In order to further illustrate the advantages and effects of the present invention, the inventors conducted a comparative experiment on the technical parameters according to Example 1:

Comparative Example 1:

A -200 mesh dried Bayan _Obo mixed rare earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 45%, the fluorine content was 7.02%, _and the aluminum content (in terms of _Al2O3 ) was 0.06%. No fluorine conversion agent was added, and then 96% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.4 to mix and make pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled at 3r/min. It was first roasted at 150°C for 90min, and then roasted at 320°C for 70min. After the reaction was completed, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 11.7%.

Comparative Example 2:

A -200 mesh dried Bayan _Obo mixed rare earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 50%, the fluorine content was 7.33%, and the aluminum content (in terms of _Al2O3 ) was 0.05%. The ore was evenly mixed with -300 mesh SiC powder at a fluorine-silicon molar ratio of 1: _1.4 , and then 98% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.5 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled at 4r/min. It was first roasted at 120°C for 120min, and then roasted at 300°C for 100min. After the reaction was completed, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 54.5%.

Comparative Example 3:

A -200 mesh dried Bayan _Obo mixed rare earth concentrate was selected, in which the rare earth content (in terms of _RE2O3 ) was 60%, the fluorine content was 6.12%, _and the aluminum content (in terms of _Al2O3 ) was 0.03%. The ore was evenly mixed with -400 mesh _SiO2 and SiN mixed powders at a fluorine-silicon molar ratio of 1:1, and then 92% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.6 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled at 6r/min. It was first roasted at 150°C for 100min, and then reacted at 350°C for 70min. After the reaction, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 59.3%.

Comparative Example 4:

A -200 mesh dried fluorocarbon cerium rare earth concentrate was selected, in which the rare earth content ( _calculated as _RE2O3 ) was 70%, the fluorine content was 6.02%, and the aluminum content ( _calculated as _Al2O3 ) was 0.08%. The ore was evenly mixed with -400 mesh _SiO2 powder at a fluorine-silicon molar ratio of 1:3, and then 95% concentrated sulfuric acid was added at a ore-acid mass ratio of 1:1 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled to be 5r/min. It was first roasted at 150°C for 90min, and then reacted at 200°C for 150min. After the reaction, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 60.1%.

Comparative Example 5:

A -200 mesh dried fluorocarbon cerium rare earth concentrate was selected, in which the rare earth content (in terms of RE ₂ O ₃ ) was 60%, the fluorine content was 7.03%, and the aluminum content (in terms of Al ₂ O ₃ ) was 0.08%. The ore was evenly mixed with -400 mesh SiC and SiN mixed powders at a fluorine-silicon molar ratio of 1:3, and then 84% concentrated sulfuric acid was added at a mineral acid mass ratio of 1:1.5 to make a mixed pulp. The concentrate was added into a rotary tube furnace steel tube and the speed was controlled at 6r/min. It was first roasted at 140°C for 100min, and then reacted at 340°C for 70min. After the reaction, the SiF ₄ content in the roasted ore was detected, and the SiF ₄ rate of fluorine was calculated to be 49.5%.

Comparative Example 6:

A -200 mesh dried fluorocarbon cerium rare earth concentrate was selected, in which the rare earth content ( _calculated as _RE2O3 ) was 50%, the fluorine content was _7.67 %, and the aluminum content ( _calculated as _Al2O3 ) was 0.07%. The ore was evenly mixed with _H2SiO4 at a fluorine-silicon molar ratio of 1:2.5, and then 98% concentrated sulfuric acid was added at a ore-acid mass ratio of 1:1.6 to make a mixed pulp. The ore was added into a rotary tube furnace steel tube and the speed was controlled to 4r/min. It was first roasted at 150°C for 90min, and then reacted at 160°C for 140min. After the reaction, the _SiF4 content in the roasted ore was detected, and the fluorine conversion rate was calculated to be 1.1%.

The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims (2)

1. A method for promoting fluorine release during the decomposition of rare earth ore in concentrated sulfuric acid, characterized in that the method specifically comprises the following steps: The Bayan Obo mixed rare earth concentrate or fluorocarbon cerium ore with reduced moisture in the dried mineral is mixed evenly with a fluorine conversion agent at a fluorine-silicon molar ratio of 1: (1.5-3), and then 92%-98% concentrated sulfuric acid is added at a mineral acid mass ratio of 1: (1.2-1.6) to mix and prepare pulp; and the pulp is subjected to staged roasting reaction; after the reaction is completed, the fluorine conversion rate in the roasted ore is detected; The stepwise roasting reaction is operated as follows: Roasting in a rotary tube furnace at 120-170° C. for 30-120 min to remove moisture introduced by the Bayan Obo mixed rare earth concentrate and the concentrated sulfuric acid; then roasting at 170-350° C. for 60-180 min; The fluorine conversion agent is a silicon-containing single compound or mixture that is both resistant to high temperatures and capable of reacting with fluorine; The fluorine conversion agent includes at least one of SiC, SiN, and H ₂ SiO ₄ ; The particle size of the Bayan Obo mixed rare earth concentrate or fluorocarbon cerium ore mineral is -200 mesh, and the particle size of the fluorine conversion agent is -400 mesh. 2. The method for promoting fluorine release during the decomposition of rare earth ore with concentrated sulfuric acid according to claim 1, characterized in that the rotation speed of the rotary tube furnace is 3 to 6 r/min.