CN111285332B - Integrated method for decomposing fluorine-containing rare earth mineral and recovering hydrofluoric acid - Google Patents
Integrated method for decomposing fluorine-containing rare earth mineral and recovering hydrofluoric acid Download PDFInfo
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- CN111285332B CN111285332B CN202010102363.1A CN202010102363A CN111285332B CN 111285332 B CN111285332 B CN 111285332B CN 202010102363 A CN202010102363 A CN 202010102363A CN 111285332 B CN111285332 B CN 111285332B
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- C01—INORGANIC CHEMISTRY
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Abstract
The invention discloses an integrated method for decomposing fluorine-containing rare earth minerals and recovering hydrofluoric acid, which comprises the following steps: (1) Mixing fluorine-containing rare earth minerals with a sulfuric acid solution with the concentration of 40-85 wt% to obtain slurry; then, carrying out a first stage of decomposition reaction on the slurry at the temperature of 80-120 ℃ for 5-20 min to obtain a first product and a first tail gas, and condensing and absorbing the first tail gas to obtain a first tail gas acid; wherein the first tail gas acid contains 15-30 wt% of hydrofluoric acid; (2) Heating the first product to 120-140 ℃ to perform a second stage decomposition reaction for 9-155 min to obtain a second product and second tail gas, and condensing and absorbing the second tail gas to obtain a second tail gas acid; (3) And carrying out solid-liquid separation on the second product to obtain a filter cake and filtrate. The invention can recover high-concentration hydrofluoric acid on the basis of ensuring higher fluorine decomposition rate.
Description
Technical Field
The invention relates to an integrated method for decomposing fluorine-containing rare earth minerals and recovering hydrofluoric acid.
Background
The earth crust contains more than 20 kinds of fluorine-containing rare earth minerals, mainly bastnaesite, bastnaesite and the like. In addition, fluorite mineral (CaF) is often associated with the mineral 2 ). The single bastnaesite is typically treated industrially using an oxidative roasting-hydrochloric acid leaching process. However, fluorine resources are finally present in wastewater and cannot be effectively utilized. The mixed rare earth mineral is a mixed mineral containing bastnaesite and monazite, and contains a certain amount of fluorite (CaF) 2 ). The mixed rare earth mineral is decomposed mainly by adopting a concentrated sulfuric acid high-temperature roasting decomposition process, the mixed rare earth mineral and the concentrated sulfuric acid are roasted at a high temperature of 500-1000 ℃ to generate acid tail gas containing a large amount of fluorine, sulfur, silicon and other elements, and the acid tail gas is usually treated by adopting a spray absorption method, so that the difficulty is increased for the recycling of fluorine resources. Therefore, how to ensure a high fluorine decomposition rate while extracting rare earth elements in rare earth minerals containing fluorine and recover hydrofluoric acid with high concentration is a technical problem of industrial attention.
CN109231174A discloses a method for recovering sulfuric acid and hydrofluoric acid from roasting spray wastewater. The method comprises the steps of spraying and absorbing mixed acid wastewater containing sulfuric acid and hydrofluoric acid obtained by a concentrated sulfuric acid high-temperature rare earth ore roasting process, removing suspended matters by using a membrane filter, and further removing dust impurities in the mixed acid by using a fine filter; the filtered mixed acid wastewater sequentially enters a preheating evaporation system, a secondary-effect evaporation system and a primary-effect evaporation system, hydrofluoric acid is evaporated and separated under the action of negative pressure, and the separated hydrofluoric acid enters a hydrofluoric acid storage tank; the single-effect evaporation system further evaporates and separates hydrofluoric acid from the mixed acid wastewater treated by the single-effect evaporation tank, and the remaining mixed acid wastewater enters a finished product sulfuric acid storage tank so that hydrofluoric acid is separated from sulfuric acid. However, the method has large investment and long process flow, and the obtained fluorine-silicon mixed acid has the concentration of about 12 percent and lower utilization value.
CN109988903A discloses a method for decomposing high-grade mixed rare earth concentrate by roasting concentrated sulfuric acid in two sections. Firstly, rare earth ore concentrate is mixed withMixing concentrated sulfuric acid for pre-reaction; then low-temperature roasting is carried out to prepare low-temperature roasted ore; and directly roasting the low-temperature roasted ore at high temperature to prepare the high-temperature roasted ore. HF and SiF are firstly calcined by two sections of concentrated sulfuric acid 4 Discharging and then discharging SO 2 、SO 3 And (4) discharging. The low-temperature roasting temperature of the method is 180-380 ℃, and partial concentrated sulfuric acid is decomposed or evaporated to generate SO due to overhigh temperature 2 、SO 3 Therefore, the purity and concentration of the collected hydrofluoric acid and fluosilicic acid mixed acid are low, and the utilization value is low.
CN109022838A discloses a treatment method of fluorine-containing rare earth mineral particles. Mixing fluorine-containing rare earth mineral particles with a sulfuric acid solution according to a certain weight ratio, then heating and preserving heat for liquid-solid reaction, and condensing and absorbing steam through a tail gas system. In this patent document, the reaction is carried out only once by heating, and the reaction is not carried out stepwise. Although the rare earth decomposition rate is high, the reaction temperature is high, and the reaction time is long, so that the concentration of hydrofluoric acid obtained by condensation and absorption of an exhaust gas system is low due to decomposition or evaporation of concentrated sulfuric acid and evaporation of water vapor in the reaction process, and the utilization value of the obtained exhaust gas acid (hydrofluoric acid) is low.
CN106978532A discloses a method for extracting rare earth, fluorine and thorium from fluorine-containing rare earth minerals by concentrated sulfuric acid. Mixing fluorine-containing rare earth minerals and concentrated sulfuric acid solution according to a certain weight ratio, then carrying out burning reaction, and cooling or spraying the obtained hydrogen fluoride tail gas to form hydrofluoric acid. However, this patent document only carries out a heating reaction once, and does not carry out the reaction in stages, and since the reaction temperature is high and the reaction time is long, the concentration of hydrofluoric acid obtained by absorption of off-gas is low due to decomposition or evaporation of concentrated sulfuric acid and evaporation of water vapor during the reaction. And no specific hydrofluoric acid concentration is mentioned in this patent document.
CN109371239A discloses a method for treating low-grade fluorite ore containing rare earth. Mixing the rare earth-containing low-grade fluorite mineral with a sulfuric acid solution, pulping and decomposing in sections, controlling a low-temperature section to decompose the fluorite mineral preferentially, and increasing the temperature to decompose the rare earth mineral. And recovering hydrofluoric acid from tail gas generated by decomposition through condensation and absorption. In the method, low-concentration sulfuric acid is adopted for long-time decomposition, and is not recycled by sectional condensation, but is once condensed and recycled to obtain tail gas acid containing hydrofluoric acid, and the evaporation of water vapor in the reaction process can cause the concentration of hydrofluoric acid obtained by tail gas absorption to be low.
Disclosure of Invention
In view of the above, an object of the present invention is to provide an integrated method for decomposing rare earth fluoride-containing minerals and recovering hydrofluoric acid, which can recover high-concentration hydrofluoric acid while ensuring a high fluorine decomposition rate. In addition, the sulfuric acid of the invention can be recycled, thereby reducing the production cost.
The invention adopts the following technical scheme to achieve the aim.
The invention provides an integrated method for decomposing fluorine-containing rare earth minerals and recovering hydrofluoric acid, which comprises the following steps:
(1) Mixing fluorine-containing rare earth minerals with a sulfuric acid solution with the concentration of 40-85 wt% to obtain slurry; then, carrying out a first stage of decomposition reaction on the slurry at the temperature of 80-120 ℃ for 5-20 min to obtain a first product and a first tail gas, and condensing and absorbing the first tail gas to obtain a first tail gas acid; wherein the first tail gas acid contains 15-30 wt% of hydrofluoric acid;
(2) Heating the first product to 120-140 ℃ to perform a second-stage decomposition reaction for 9-155 min to obtain a second product and second tail gas, and condensing and absorbing the second tail gas to obtain a second tail gas acid;
(3) And carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate.
According to the process of the present invention, preferably, in the step (1), the concentration of the sulfuric acid solution is 72 to 85wt%.
According to the method of the invention, preferably, in the step (1), the fluorine-containing rare earth mineral and H in the sulfuric acid solution 2 SO 4 The weight ratio of (A) to (B) is 1.5-5.
According to the method of the present invention, preferably, in the step (1), the first stage decomposition reaction time is 5 to 15min.
According to the method of the present invention, preferably, in the step (1), the first stage decomposition reaction temperature is 90 to 120 ℃ and the reaction time is 5 to 10min.
According to the method of the present invention, preferably, in the step (1), the second off-gas acid in the step (2) contains 0 to 3wt% of hydrofluoric acid.
According to the method of the present invention, preferably, in the step (2), the second-stage decomposition reaction time is 10 to 155min.
According to the method of the present invention, preferably, the method further comprises the steps of:
washing the filter cake in the step (3) with the second tail gas acid in the step (2) to obtain acid leaching residue and washing liquid; and extracting the acid leaching residue with water to obtain a rare earth sulfate aqueous solution and the water leaching residue.
According to the method of the present invention, preferably, the method further comprises the steps of:
combining the washing liquid with the filtrate obtained in the step (3) to obtain pickle liquor; regulating the acid leaching solution to a sulfuric acid concentration of 40-85 wt% by using concentrated sulfuric acid for treating the next batch of fluorine-containing rare earth minerals.
According to the method of the present invention, preferably, in the step (1), the fluorine-containing rare earth mineral is one of bastnaesite or a mixed rare earth ore containing bastnaesite and monazite; the fluorine content in the fluorine-containing rare earth mineral is more than or equal to 2wt%.
Detailed Description
The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.
"wt%" of the present invention means weight percent.
The integrated method for decomposing the rare earth mineral containing fluorine and recovering hydrofluoric acid comprises the following steps: (1) a first stage decomposition reaction; (2) second stage decomposition reaction; and (3) carrying out solid-liquid separation. As described in detail below.
< first stage decomposition reaction >
Mixing the fluorine-containing rare earth mineral with 40-85 wt% sulfuric acid solution to obtain slurry. This is advantageous for obtaining a higher concentration of hydrofluoric acid.
The fluorine-containing rare earth mineral is one of bastnaesite or mixed rare earth mineral of bastnaesite and monazite. Preferably, the fluorine-containing rare earth mineral can be ground and then participate in the reaction. The polishing method is not particularly limited. According to one embodiment of the invention, the fluorine-containing rare earth mineral is bastnaesite. According to another embodiment of the present invention, the fluorine-containing rare earth mineral is a mixed rare earth mineral of bastnaesite and monazite.
The fluorine content in the fluorine-containing rare earth mineral is more than or equal to 2wt%. Preferably, the fluorine content in the fluorine-containing rare earth mineral is more than or equal to 5wt%. More preferably, the fluorine content in the fluorine-containing rare earth mineral is greater than or equal to 7wt%.
The concentration of the sulfuric acid solution may be 40 to 85wt%, preferably 65 to 85wt%, more preferably 72 to 85wt%. The sulfuric acid solution with the concentration range is beneficial to greatly reducing the content of S in the first tail gas acid and improving the concentration of hydrofluoric acid in the first tail gas acid.
Fluorine-containing rare earth mineral and H in the sulfuric acid solution 2 SO 4 The weight ratio of (A) to (B) is 1.5 to 5, preferably 1 to 2 to 5, more preferably 1. Thus being beneficial to the reaction in the slurry state, improving the decomposition rate of fluorine, reducing the decomposition temperature and further being beneficial to obtaining hydrofluoric acid with higher concentration.
And carrying out a first stage of decomposition reaction on the slurry at the temperature of 80-120 ℃ for 5-20 min to obtain a first product and a first tail gas. The reaction temperature of the first stage decomposition reaction may be 80 to 120 ℃, preferably 90 to 120 ℃, and more preferably 100 to 120 ℃. The reaction time may be 5 to 20min. Preferably, the reaction time is 5 to 15min. More preferably, the reaction time is 5 to 10min. Thus, the decomposition of the fluorine-containing rare earth mineral can be ensured, the evaporation amount of water can be reduced, and the hydrofluoric acid with higher concentration can be obtained. Particularly, the reaction time and the reaction temperature are strictly controlled, and the time is preferably not more than 20min, otherwise, the hydrofluoric acid with higher concentration cannot be obtained. The reaction temperature cannot be too high, and if the reaction temperature is too high, the amount of evaporation of the generated water increases, and the content of S in the tail gas increases due to decomposition of sulfuric acid, so that hydrofluoric acid having a high concentration cannot be obtained.
The obtained first product is not treated, and the first product is directly heated continuously to carry out second-stage decomposition reaction.
And condensing and absorbing the first tail gas to obtain a first tail gas acid. The first tail gas contains HF and H 2 And (O). The mode of condensation is not particularly limited as long as the object of the present invention can be achieved. The first tail gas acid obtained by the invention contains hydrofluoric acid. The obtained first tail gas acid contains almost no sulfuric acid. The concentration of hydrofluoric acid in the first tail gas acid is more than or equal to 15wt%, preferably more than or equal to 20wt%. Specifically, the concentration of hydrofluoric acid in the first off-gas acid is 20 to 30wt%, preferably 22 to 30wt%, and more preferably 25 to 30wt%.
According to one embodiment of the invention, the concentration of the sulfuric acid solution is 65-70 wt%, and the fluorine-containing rare earth mineral and H in the sulfuric acid solution 2 SO 4 The weight ratio of 1 to 2.8-3, and the fluorine content in the fluorine-containing rare earth mineral is 8.0-8.1 wt%. The reaction temperature of the first stage decomposition reaction is 105-110 ℃, and the reaction time is 10-11 min. The concentration of hydrofluoric acid in the first tail gas acid is 25-26 wt%.
According to another embodiment of the present invention, the concentration of the sulfuric acid solution is 70 to 75wt%, and the fluorine-containing rare earth mineral and H in the sulfuric acid solution 2 SO 4 The weight ratio of 1 to 2.5-2.6, and the fluorine content in the fluorine-containing rare earth mineral is 34-35 wt%. The reaction temperature of the first stage decomposition reaction is 118-120 ℃, and the reaction time is 18-20 min. The concentration of hydrofluoric acid in the first tail gas acid is 28-29 wt%.
According to another embodiment of the present invention, the concentration of the sulfuric acid solution is 75 to 85wt%, and the fluorine-containing rare earth mineral and H in the sulfuric acid solution 2 SO 4 The weight ratio of the fluorine-containing rare earth mineral is 1. The reaction temperature of the first stage decomposition reaction is 115-120 ℃, and the reaction time is 5-6 min. The concentration of hydrofluoric acid in the first tail gas acid is 29-30 wt%.
The first stage decomposition reaction is completed by controlling the reaction temperature and the reaction time, so that the water evaporation amount and the decomposition amount or evaporation amount of the sulfuric acid can be controlled while the fluorine-containing mineral is efficiently decomposed, and the hydrofluoric acid with higher concentration (the concentration of the hydrofluoric acid is more than or equal to 15 wt%) is obtained. The obtained hydrofluoric acid with higher concentration can be directly used as a primary chemical raw material, and the subsequent recovery procedures are reduced. If the temperature is too low and the reaction time is too short, the fluorine-containing rare earth mineral is incompletely decomposed, so that the fluorine recovery rate is reduced; if the temperature is too high and the reaction time is too long, the amount of water evaporated increases and the amount of sulfuric acid decomposed or evaporated increases, resulting in a decrease in the concentration of the recovered hydrofluoric acid.
< second-stage decomposition reaction >
And heating the first product to 120-140 ℃ to perform a second-stage decomposition reaction for 9-155 min to obtain a second product and a second tail gas.
The reaction temperature of the second stage decomposition reaction may be 120 to 140 ℃, preferably 128 to 140 ℃, and more preferably 130 to 140 ℃. The reaction time may be 9 to 155min. Preferably, the reaction time is 10 to 155min. More preferably, the reaction time is 10 to 150min. Thus being beneficial to obtaining rare earth sulfate, improving the fluorine decomposition rate and recycling more fluorine resources.
And condensing and absorbing the second tail gas to obtain a second tail gas acid. The condensing method is not particularly limited. The second tail gas contains a very small amount of HF. The second tail gas acid contains very low concentration hydrofluoric acid, and the concentration of the hydrofluoric acid is less than or equal to 4wt%. Preferably, the hydrofluoric acid concentration is 3.5wt% or less. More preferably, the hydrofluoric acid concentration is 3wt% or less. Specifically, the concentration of hydrofluoric acid in the second tail gas acid is 0 to 3wt%, preferably 0 to 2wt%. By re-condensing and absorbing, more fluorine resources can be recovered.
According to an embodiment of the present invention, the temperature of the second stage decomposition reaction is 130 to 132 ℃, and the reaction time is 150 to 160min. The concentration of hydrofluoric acid in the second tail gas acid is 1.5-1.6 wt%.
According to another embodiment of the present invention, the temperature of the second stage decomposition reaction is 133 to 135 ℃ and the reaction time is 50 to 60min. The concentration of hydrofluoric acid in the second tail gas acid is 2.3-2.4 wt%.
According to another embodiment of the present invention, the temperature of the second stage decomposition reaction is 138 to 140 ℃ and the reaction time is 10 to 15min. The concentration of hydrofluoric acid in the second tail gas acid is 2.9-3.0 wt%.
The temperature of the second-stage decomposition reaction is higher than that of the first-stage decomposition reaction, the fluorine-containing rare earth minerals can be completely decomposed by the arrangement, more fluorine resources can be recycled, the fluorine element and the rare earth element can be almost completely separated, the influence of the fluorine element on extraction of the rare earth element is avoided, and the yield of the rare earth sulfate is improved.
< solid-liquid separation >
And carrying out solid-liquid separation on the second product to obtain a filter cake and filtrate.
Washing the filter cake with the second tail gas acid in the step (2) to obtain acid leaching residue and washing liquid.
And extracting the acid leaching residue with water to obtain a rare earth sulfate aqueous solution and the water leaching residue. Thus, an aqueous solution of a rare earth sulfate can be obtained.
And (4) combining the washing liquid with the filtrate obtained in the step (3) to obtain pickle liquor. And regulating the sulfuric acid concentration of the pickle liquor to 40-85 wt%, preferably 72-85 wt% by using concentrated sulfuric acid, and treating the next batch of fluorine-containing rare earth minerals. The concentration of the pickle liquor is adjusted by concentrated sulfuric acid, and then new fluorine-containing rare earth minerals are continuously and circularly treated, so that the raw materials are saved, and the production cost is reduced.
And (3) washing the filter cake to obtain a second tail gas acid which is obtained by the second-stage decomposition reaction in the step (2). Therefore, the production cost can be reduced, and the low-concentration hydrofluoric acid can be continuously used so as not to lose fluorine resources. In addition, because the reaction temperature and the reaction time are strictly controlled in the first stage of decomposition reaction, the first tail gas acid containing hydrofluoric acid with higher concentration and the second tail gas acid containing hydrofluoric acid with lower concentration can be obtained.
In the following examples and comparative examples, the fluorine decomposition rate = (weight of fluorine in the fluorine-containing rare earth mineral-weight of fluorine in the water-leached residue)/weight of fluorine in the fluorine-containing rare earth mineral × 100%.
Example 1
The fluorine-containing diluent used in the present exampleThe soil mineral is Baotou mixed rare earth concentrate, and the fluorine content of the soil mineral is 7.6wt%. Fluorine-containing rare earth mineral and H in sulfuric acid solution 2 SO 4 The weight ratio of (1).
Uniformly mixing 100kg of ground fluorine-containing rare earth mineral and 455kg of sulfuric acid solution with the concentration of 55wt% to obtain slurry; and then carrying out a first stage decomposition reaction on the slurry at 100 ℃ for 15min to obtain a first product and a first tail gas. And condensing and absorbing the first tail gas to obtain a first tail gas acid. The concentration of hydrofluoric acid in the obtained first tail gas acid is 15wt%.
And heating the first product to 120 ℃ to perform a second-stage decomposition reaction for 180min to obtain a second product and a second tail gas. And condensing and absorbing the second tail gas to obtain a second tail gas acid. The concentration of hydrofluoric acid in the second tail gas acid is 1.7wt%.
And carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate.
And washing the filter cake with a second tail gas acid to obtain acid leaching residue and washing liquid. The washing liquid and the filtrate are combined to obtain pickle liquor. And extracting the acid leaching residue with water to obtain a rare earth sulfate solution and the water leaching residue. And (3) measuring the content of fluorine in the water leaching residue, and calculating to obtain the fluorine decomposition rate in the fluorine-containing rare earth mineral. And regulating the acid leaching solution to 55wt% with concentrated sulfuric acid for treating the next batch of fluorine-containing rare earth minerals.
Example 2
The rare earth mineral containing fluorine used in the present example was tetrachoria bastnaesite, and the fluorine content thereof was 8.1wt%. Fluorine-containing rare earth mineral and H in sulfuric acid solution 2 SO 4 The weight ratio of (1).
Uniformly mixing 100kg of ground fluorine-containing rare earth mineral and 375kg of 40wt% sulfuric acid solution to obtain slurry; then, the slurry is subjected to a first stage decomposition reaction at 120 ℃ for 20min to obtain a first product and a first tail gas. And condensing and absorbing the first tail gas to obtain a first tail gas acid. The concentration of hydrofluoric acid in the obtained first tail gas acid is 16.4wt%.
And heating the first product to 120 ℃ to perform a second-stage decomposition reaction for 240min to obtain a second product and a second tail gas. And condensing and absorbing the second tail gas to obtain a second tail gas acid. The concentration of hydrofluoric acid in the second tail gas acid is 1.2wt%.
And carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate.
And washing the filter cake with a second tail gas acid to obtain acid leaching residue and washing liquid. The washing liquid and the filtrate are combined to obtain pickle liquor. And extracting the acid leaching residue with water to obtain a rare earth sulfate solution and the water leaching residue. And (3) measuring the fluorine content in the water leaching residue, and calculating to obtain the fluorine decomposition rate in the fluorine-containing rare earth mineral. And regulating the acid leaching solution to the concentration of 40wt% by using concentrated sulfuric acid for treating the next batch of fluorine-containing rare earth minerals.
Example 3
The rare earth mineral containing fluorine used in the present example was tetrachoric bastnaesite, and the fluorine content thereof was 8.1wt%. Fluorine-containing rare earth mineral and H in sulfuric acid solution 2 SO 4 The weight ratio of (1).
Uniformly mixing 100kg of ground fluorine-containing rare earth mineral and 460kg of 65wt% sulfuric acid solution to obtain slurry; then, the slurry is subjected to a first stage decomposition reaction at 110 ℃ for 10min to obtain a first product and a first tail gas. And condensing and absorbing the first tail gas to obtain a first tail gas acid. The concentration of hydrofluoric acid in the first tail gas acid is 25.7wt%.
And heating the first product to 130 ℃ to perform a second-stage decomposition reaction for 150min to obtain a second product and a second tail gas. And condensing and absorbing the second tail gas to obtain a second tail gas acid. The concentration of hydrofluoric acid in the second tail gas acid is 1.5wt%.
And carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate.
And washing the filter cake with a second tail gas acid to obtain acid leaching residue and washing liquid. The washing liquid and the filtrate are combined to obtain pickle liquor. And extracting the acid leaching residue with water to obtain a rare earth sulfate solution and the water leaching residue. And (3) measuring the content of fluorine in the water leaching residue, and calculating to obtain the fluorine decomposition rate in the fluorine-containing rare earth mineral. And regulating the acid leaching solution to a sulfuric acid concentration of 65wt% by using concentrated sulfuric acid so as to treat the next batch of fluorine-containing rare earth minerals.
Example 4
The rare earth mineral containing fluorine used in the embodiment is BaiyuneboitanThe fluorine content of the rare earth low-grade fluorite ore is 34.9wt%. Fluorine-containing rare earth mineral and H in sulfuric acid solution 2 SO 4 The weight ratio of (1).
Uniformly mixing 100kg of ground fluorine-containing rare earth mineral and 357kg of sulfuric acid solution with the concentration of 70wt% to obtain slurry; and then, carrying out a first stage decomposition reaction on the slurry at 120 ℃ for 20min to obtain a first product and a first tail gas. And condensing and absorbing the first tail gas to obtain a first tail gas acid. The concentration of hydrofluoric acid in the obtained first tail gas acid is 28.4wt%.
And heating the first product to 135 ℃ to perform a second-stage reaction for 60min to obtain a second product and a second tail gas. And condensing and absorbing the second tail gas to obtain a second tail gas acid. The concentration of hydrofluoric acid in the second tail gas acid is 2.3wt%.
And carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate.
And washing the filter cake with a second tail gas acid to obtain acid leaching residue and washing liquid. The washing liquid and the filtrate are combined to obtain pickle liquor. And extracting the acid leaching residue with water to obtain a rare earth sulfate solution and the water leaching residue. And (3) measuring the fluorine content in the water leaching residue, and calculating to obtain the fluorine decomposition rate in the fluorine-containing rare earth mineral. And regulating the acid leaching solution to a sulfuric acid concentration of 70wt% by using concentrated sulfuric acid so as to treat the next batch of fluorine-containing rare earth minerals.
Example 5
The fluorine-containing rare earth mineral used in the embodiment is Baotou mixed rare earth concentrate, and the fluorine content of the Baotou mixed rare earth concentrate is 7.6wt%. Fluorine-containing rare earth mineral and H in sulfuric acid solution 2 SO 4 The weight ratio of (1).
Uniformly mixing 100kg of ground fluorine-containing rare earth mineral and 588kg of sulfuric acid solution with the concentration of 85wt% to obtain slurry; then, the slurry is subjected to a first stage decomposition reaction at 120 ℃ for 5min to obtain a first product and a first tail gas. And condensing and absorbing the first tail gas to obtain a first tail gas acid. The concentration of hydrofluoric acid in the obtained first tail gas acid is 30wt%.
And heating the first product to 140 ℃ to perform a second-stage decomposition reaction for 10min to obtain a second product and a second tail gas. And condensing and absorbing the second tail gas to obtain a second tail gas acid. The concentration of hydrofluoric acid in the second tail gas acid is 3wt%.
And carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate.
And washing the filter cake with a second tail gas acid to obtain acid leaching residue and washing liquid. The washing liquid and the filtrate are combined to obtain pickle liquor. And extracting the acid leaching residue with water to obtain a rare earth sulfate solution and the water leaching residue. And (3) measuring the content of fluorine in the water leaching residue, and calculating to obtain the fluorine decomposition rate in the fluorine-containing rare earth mineral. And regulating the acid leaching solution to the sulfuric acid concentration of 85wt% by using concentrated sulfuric acid so as to treat the next batch of fluorine-containing rare earth minerals.
Comparative example 1
The rare earth mineral containing fluorine used in the present example was tetrachoric bastnaesite, and the fluorine content thereof was 8.1wt%. Fluorine-containing rare earth mineral and H in sulfuric acid solution 2 SO 4 The weight ratio of (1).
Uniformly mixing 100kg of ground fluorine-containing rare earth mineral and 460kg of 65wt% sulfuric acid solution to obtain slurry; then, the slurry is subjected to a first stage decomposition reaction at 110 ℃ for 30min to obtain a first product and a first tail gas. And condensing and absorbing the first tail gas to obtain a first tail gas acid. The concentration of hydrofluoric acid in the obtained first tail gas acid is 12.7wt%.
And heating the first product to 130 ℃ to perform a second-stage decomposition reaction for 150min to obtain a second product and a second tail gas. And condensing and absorbing the second tail gas to obtain a second tail gas acid. The concentration of hydrofluoric acid in the second tail gas acid is 1.3wt%.
And carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate.
And washing the filter cake with a second tail gas acid to obtain acid leaching residue and washing liquid. The washing liquid and the filtrate are combined to obtain pickle liquor. And extracting the acid leaching residue with water to obtain a rare earth sulfate solution and the water leaching residue. And (3) measuring the content of fluorine in the water leaching residue, and calculating to obtain the fluorine decomposition rate in the fluorine-containing rare earth mineral. And regulating the acid leaching solution to a sulfuric acid concentration of 65wt% by using concentrated sulfuric acid so as to treat the next batch of fluorine-containing rare earth minerals.
TABLE 1
As is clear from table 1, in examples 1 to 5, while the decomposition rate of fluorine in the rare earth fluoride-containing mineral was maintained, the concentration of hydrofluoric acid in the recovered first off-gas acid was significantly higher than that in comparative example 1.
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.
Claims (2)
1. An integrated method for decomposing fluorine-containing rare earth minerals and recovering hydrofluoric acid is characterized by comprising the following steps:
(1) Mixing fluorine-containing rare earth minerals with sulfuric acid solution with the concentration of 72-85 wt% to obtain slurry; then, carrying out a first stage of decomposition reaction on the slurry at 100-120 ℃ for 5-10 min to obtain a first product and a first tail gas, and condensing and absorbing the first tail gas to obtain a first tail gas acid; wherein the first tail gas acid contains 25-30 wt% of hydrofluoric acid;
the fluorine-containing rare earth mineral is selected from one of bastnaesite or a mixed rare earth mineral containing bastnaesite and monazite; fluorine-containing rare earth mineral and H in sulfuric acid solution 2 SO 4 The weight ratio of the fluorine-containing rare earth mineral is 1;
(2) Heating the first product to 130-140 ℃ to perform a second-stage decomposition reaction for 10-150 min to obtain a second product and second tail gas, and condensing and absorbing the second tail gas to obtain a second tail gas acid; the concentration of hydrofluoric acid in the second tail gas acid is 2-3.0 wt%;
(3) Carrying out solid-liquid separation on the second product to obtain a filter cake and a filtrate;
washing the filter cake in the step (3) with the second tail gas acid in the step (2) to obtain acid leaching residue and washing liquid; and extracting the acid leaching residue with water to obtain a rare earth sulfate aqueous solution and the water leaching residue.
2. The method according to claim 1, characterized in that the method further comprises the steps of:
combining the washing liquid with the filtrate obtained in the step (3) to obtain pickle liquor; regulating the acid leaching solution to 72-85 wt% with concentrated sulfuric acid for treating the next batch of fluorine-containing rare earth minerals.
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| WO2017100933A1 (en) * | 2015-12-16 | 2017-06-22 | Quest Rare Minerals Ltd. | Rare earth ore processing methods by acid mixing, sulphating and decomposing |
| CN106978532A (en) * | 2017-03-15 | 2017-07-25 | 包头稀土研究院 | The method that the concentrated sulfuric acid extracts fluorine-containing rare-earth mineral middle rare earth, fluorine and thorium |
| CN107475542A (en) * | 2017-07-17 | 2017-12-15 | 中国恩菲工程技术有限公司 | The method for handling rare earth ore concentrate |
| CN109371239A (en) * | 2018-12-03 | 2019-02-22 | 包头稀土研究院 | A method of low-grade fluorite mine of the processing containing rare earth |
| CN109536746A (en) * | 2018-12-03 | 2019-03-29 | 包头稀土研究院 | A kind of method that the pulp of low calcium high-grade mixed rare earth concentrates circulation is decomposed |
| CN109988903A (en) * | 2019-05-21 | 2019-07-09 | 李梅 | A kind of method that concentrated sulfuric acid two-stage roasting decomposes high-grade mixed rare earth concentrates |
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| WO2017100933A1 (en) * | 2015-12-16 | 2017-06-22 | Quest Rare Minerals Ltd. | Rare earth ore processing methods by acid mixing, sulphating and decomposing |
| CN106978532A (en) * | 2017-03-15 | 2017-07-25 | 包头稀土研究院 | The method that the concentrated sulfuric acid extracts fluorine-containing rare-earth mineral middle rare earth, fluorine and thorium |
| CN107475542A (en) * | 2017-07-17 | 2017-12-15 | 中国恩菲工程技术有限公司 | The method for handling rare earth ore concentrate |
| CN109371239A (en) * | 2018-12-03 | 2019-02-22 | 包头稀土研究院 | A method of low-grade fluorite mine of the processing containing rare earth |
| CN109536746A (en) * | 2018-12-03 | 2019-03-29 | 包头稀土研究院 | A kind of method that the pulp of low calcium high-grade mixed rare earth concentrates circulation is decomposed |
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