WO2009021389A1

WO2009021389A1 - A PROCESS OF SMELTING MONAZITE RARE EARTH ORE RICH IN Fe

Info

Publication number: WO2009021389A1
Application number: PCT/CN2008/000715
Authority: WO
Inventors: Xiaowei Huang; Hongwei Li; Zhiqi Long; Ying Liu; Na Zhao; Guocheng Zhang
Original assignee: Grirem Advanced Materials Co., Ltd.
Priority date: 2007-08-10
Filing date: 2008-04-08
Publication date: 2009-02-19

Abstract

A process of smelting monazite rare earth ore rich in Fe in particular comprises the following steps: mixing Fe-rich monazite rare earth ore containing 8-40% Fe with concentrated sulphuric acid and adding the mixture into a calcining kiln; calcining at 231-600ºC, wherein rare earth reacts with sulphuric acid to produce rare earth sulphate which dissolves in water or a solution with a H+ concentration less than 1.5mol/L and Fe is transformed into at least one of iron sulphate, iron phosphate and iron pyrophosphate; leaching the calcined ore with water or a solution with a H+ concentration less than 1.5mol/L and filtering to obtain a solution of rare earth sulphate containing Fe and P; neutralizing the solution to recover Fe and P and to obtain pure solution of rare earth sulphate; producing single or mixed rare earth compound by extracting and separating the pure solution directly, or producing mixed rare earth carbonates by precipitation process. The process could avoid the influence of Fe on extracting rare earth. The process is simple, continuous, easy to control, low in consumption of chemical engineering materials, high in recovery ratio of rare earth and suitable for large-scale production.

Description

Smelting method of rich iron monazite rare earth ore

The invention relates to a method for smelting iron-rich monazite rare earth ore, in particular to a method for smelting a monazite rare earth ore containing 8% to 40% of iron, belonging to the field of rare earth ore smelting production. BACKGROUND OF THE INVENTION Monazite is a kind of rare earth phosphate mineral. Generally, monazite minerals are easy to be selected, and concentrates with high rare earth grade can be obtained. The mineral content of monazite in the concentrate can reach more than 95%, and the concentrate also contains a small amount of rutile and titanium. Other minerals such as iron ore, zircon and quartz. In the industry, it is generally used to decompose caustic soda at normal pressure ["Rare Earth", the first edition of the book, Metallurgical Industry Press, 1978, P221 - 237; Second Edition, Metallurgical Industry Press, 1995, P365-373] method of decomposition of monazite concentrate During the reaction between monazite and caustic soda, the rare earth forms a water-insoluble hydroxide, the phosphorus is converted into trisodium phosphate, and the rare earth hydroxide is further dissolved and removed by hydrochloric acid to obtain a mixed rare earth chloride. Characteristics of the process: Basically no waste gas pollution, phosphorus is recovered in the form of sodium phosphate, but the process requires high grade of concentrate. If the content of impurities such as iron and silicon in the concentrate is high, it is easy to form sodium silicate, iron hydroxide and other glue. The material, the precipitation filtration separation process is difficult to perform, and therefore, the process will not operate normally. For example, the Mt. Weld monazite mine in Australia, the iron ore content in the ore is as high as 40%, and the monazite mineral and iron mineral are embedded together, the grain size is fine, it is difficult to sort, the concentrate grade can only reach 40%, and the ore dressing The yield is low. For this type of rare earth ore, the use of caustic soda decomposition does not work at all.

In the early days, some scholars also studied and developed the monolithic concentrated sulfuric acid decomposition method ["Rare Earth", the first edition of the book, Metallurgical Industry Press, 1978, P237-241], the monazite concentrate and concentrated sulfuric acid mixed at 200-230 °C decomposition 2 For a period of 4 hours, the concentrated sulfuric acid is 1.7-2 times the weight of the concentrate. After the decomposition product is cooled, it is leached with 7-10 times the weight of the concentrate. The rare earth 55g/L in the leachate, P ₂ 0 ₅ 25g/L, Fe ₂ 0 ₃ 2.5g/L, acidity 2.5N. The leachate has high acidity, high impurity phosphorus and antimony content, and the rare earth and strontium are precipitated by sodium sulfate double salt, and then converted into hydroxide by alkali, then the rare earth is preferentially leached with acid, and the rare earth and strontium are separated by extraction. The method is complicated in process, many solid-liquid separation steps, discontinuous process, low rare earth recovery rate; combined use of acid and alkali, high cost, in addition, phosphorus is difficult to be treated and recovered in wastewater, and radioactive cesium is difficult to be recycled in slag and wastewater. Summary of the invention

The object of the present invention is to provide a method for smelting iron-rich monazite rare earth ore which is simple in process, continuous and easy to control, low in chemical material consumption, high in rare earth recovery rate, and suitable for mass production. For monazite rare earth mines with high iron content, such as the Mt. Weld monazite mine in Australia, the iron oxide content in the ore is as high as 40wt% or more, and the monazite minerals and iron minerals are embedded together, and the grain size is fine and difficult to select. The concentrate grade can only reach 40wt%, and cannot be smelted by caustic soda decomposition method. The present invention mixes 8wt%-40wt% iron-rich monazite rare earth ore and concentrated sulfuric acid into the roasting kiln at 231-600°C. Baked at a temperature, the rare earth reacts with sulfuric acid to form a rare earth salt of sulfuric acid soluble in water or a solution having a H+ concentration of less than 1.5 mol/L, and the iron forms at least one of iron sulfate, iron phosphate and iron pyrophosphate, and is used for roasting ore. Water or dilute acid leaching to obtain a rare earth slurry containing iron and phosphorus, and more than 95% of the rare earth enters the slurry in an ionic state, and after filtration, a rare earth solution containing iron and phosphorus is obtained. The rare earth sulfate solution is neutralized with oxides, hydroxides and carbonates containing magnesium, calcium and aluminum. When the pH of the solution is 3-5, the iron ions present in the solution combine with phosphorus to form iron phosphate precipitate, which avoids Formation of a rare earth phosphate precipitate. In order to ensure that the rare earth is not lost during the precipitation of phosphorus and iron, Fe/P should be greater than 2, preferably greater than 3. After precipitation, it is filtered to obtain a pure rare earth sulfuric acid solution, which is directly subjected to extraction and separation to prepare a single or mixed rare earth compound, or a carbonate precipitation method to prepare a rare earth carbonate.

The main reactions of monazite and concentrated sulfuric acid at high temperatures are as follows:

2REP0 ₄ +3H ₂ S0 ₄ =RE ₂ (S0 ₄ ) ₃ +2H ₃ P0 ₄

Th ₃ (P0 ₄ ) ₄ +6H ₂ S04=3Th(S0 ₄ ) ₂ +4H ₃ P0 ₄

Fe ₂ 0 ₃ +3H ₂ S0 ₄ =Fe ₂ (S0 ₄ )3+3H ₂ 0 t When the reaction temperature reaches 300 ° C, the phosphoric acid formed by the decomposition reaction dehydrates to form pyrophosphoric acid, pyrophosphoric acid and antimony, iron and calcium Forming pyrophosphate which is poorly soluble in water.

2H ₃ P0 ₄ =H ₄ P ₂ 0 ₇ +H ₂ 0 t

Th(S0 ₄ ) ₂ +H ₄ P ₂ 0 ₇ =ThP ₂ 0 ₇ +2H ₂ S0 ₄

2Fe ₂ (S0 ₄ ) ₃ +3H ₄ P ₂ 0 ₇ =Fe ₄ (P ₂ 0 ₇ ) ₃ +6H ₂ S0 ₄

2CaS0 ₄ + H ₄ P ₂ 0 ₇ = Ca ₂ P ₂ 0 ₇ + 2H ₂ S0 ₄ When the reaction temperature is about 328 ° C, sulfuric acid is decomposed.

H ₂ S0 ₄ =S0 ₃ t +H ₂ 0 t When the reaction temperature reaches 400 ° C, Fe ₂ (S0 ₄ ) ₃ decomposes into a salt-insoluble iron sulfate which is hardly soluble in water, and pyrophosphoric acid is further dehydrated.

Fe ₂ (S0 ₄ ) ₃ =Fe ₂ 0(S0 ₄ ) ₂ +S0 ₃ t

H ₄ P ₂ 0 ₇ =2HP0 ₃ +H ₂ 0 t

Therefore, when the rare earth ore is calcined with a certain amount of concentrated sulfuric acid, it is necessary to control the appropriate temperature and baking time to obtain a high rare earth decomposition rate. When the calcination temperature is lower than 230 ° C, the mineral decomposition ability is weak; but the calcination temperature is too high, sulfur The acid is easily decomposed, and it is easy to burn the ore, the solubility of the rare earth sulfate is weakened, and the rare earth leaching rate is lowered. When the calcination temperature is low, the calcination time is longer.

The method is also applicable to the treatment of other phosphate-containing rare earth ores such as xenotime or its mixed rare earth ore.

The invention specifically adopts the following technical solutions: A method for smelting iron-rich monazite rare earth ore, using iron-rich monazite rare earth ore as raw material, containing 8 wt% to 40 wt% of iron in the ore, and the smelting method comprises the following technical features:

1) the iron-rich monazite rare earth ore and concentrated sulfuric acid are mixed into the roasting kiln according to the weight ratio of acid/mine = 1 to 2;

2) calcination at a temperature of 231-600 ° C for 1-20 hours, the rare earth and sulfuric acid react to form a rare earth salt of sulfuric acid soluble in water or a solution having a concentration of H + less than 1.5 mol / L, iron forms iron sulfate, iron phosphate, coke At least one of iron phosphates;

3) roasting ore water or a solution with a H+ concentration of less than 1.5 mol/L to obtain a rare earth water immersion slurry containing iron and phosphorus, the rare earth concentration REO is 20-55 g/L, the H+ concentration is less than 1.5 mol/L, and the rare earth The decomposition rate is greater than 95%.

The smelting method of the iron-rich monazite rare earth ore according to the present invention is based on the Australian Mt. Weld monazite ore or concentrate, and the iron content in the ore is 15wt%-40wt%, REO 18wt-60wt%. The mixing weight ratio of the ore and the concentrated sulfuric acid with the content of ≥90 wt% is mixed in the ratio of acid/mine = 1.3-1.69, and then continuously added to the rotary kiln, and calcined at a temperature of 231-400 ° C for 2-12 hours to roast the ore. The solution is leached with water or a solution having a H+ concentration of less than 1.5 mol/L to obtain a rare earth decomposition rate of more than 97% in a rare earth water immersion slurry containing iron and phosphorus.

The calcined ore is leached with water or a solution having a H+ concentration of preferably less than 1.0 mol/L, and the solid-liquid weight ratio is 1:5 - 1:12, and filtered to obtain a rare earth solution containing iron and phosphorus, and the rare earth concentration thereof is REO. It is 25-55g/L and the acidity is 0.05-1.0 mol/L. The optimum conditions are a solid-liquid ratio of 1: 7 - 1: 10, and the rare earth concentration REO is 30-50 g/L and the acidity is 0.1-0.5 mol/L.

The iron or phosphorus-containing rare earth water immersion slurry or the iron and phosphorus-containing rare earth solution is neutralized with at least one of magnesium, calcium, aluminum oxides, hydroxides and carbonates to recover iron and phosphorus. After filtration, a pure rare earth sulfate solution is obtained, wherein Fe<0.05g/L, P<0.001 g/L, Th<0.1 mg/L, pH 3-5. The optimized condition is that the rare earth aqueous immersion liquid containing iron or phosphorus or the rare earth sulfuric acid solution of iron or phosphorus is used in at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, calcium oxide, calcium carbonate, calcium hydroxide and calcium carbide slag. And, iron and phosphorus are recovered in the form of iron phosphate to obtain a pure rare earth sulfuric acid solution, wherein Fe<0.005g/L, P<0.0005g/L, Th<0.05 mg/L, pH 3.5-4.5. The above pure rare earth sulfuric acid solution is directly extracted by an acidic phosphorus extracting agent or separately to prepare a single or mixed rare earth compound; or the acidic rare earth extracting agent or the carboxylic acid extracting agent is used to extract all the rare earths, and then is prepared by stripping with hydrochloric acid or nitric acid. Mixing rare earth chloride or rare earth nitrate, or further extracting and separating to prepare a single or mixed rare earth compound.

The above pure rare earth sulfuric acid solution can also be used to produce mixed rare earth carbonate by ammonium bicarbonate, sodium carbonate or sodium hydrogencarbonate precipitation. The mixed rare earth carbonate can be subjected to extraction by hydrochloric acid or nitric acid, an acidic phosphorus extractant or a carboxylic acid extractant to prepare a single or mixed rare earth compound.

In the smelting method of the iron-rich monazite rare earth ore according to the present invention, in the sulfuric acid roasting process of the rich iron monazite rare earth ore, the tail gas generated is subjected to leaching to recover sulfuric acid, or discharged by using an alkali liquid absorption treatment.

The advantages of the invention are:

The invention is an effective smelting method for treating iron-rich low-grade monazite rare earth ore. The method comprises the following steps: extracting and separating various rare earth compounds by concentrated sulfuric acid roasting, water immersion, impurity removal, and effectively solving the influence of iron on the rare earth extraction process, the process The process is simple, continuous and easy to control, low consumption of chemical materials, high recovery rate of rare earth, suitable for large-scale production. detailed description:

Example 1 _:

The iron-rich monazite concentrate is used as raw material, and the Fe 20.6 wt REO is 41.8 wt%, P 7.5 wt%. The ore is mixed with 93 wt% concentrated sulfuric acid in the weight ratio of acid/mine = 1.4, and then continuously added to the rotary kiln, and calcined at 240 ° C for 8 hours, and the calcined ore is leached with water, and the solid-liquid ratio is 1:9. A rare earth water immersion slurry was obtained, the rare earth concentration REO was 44.6 g/L, the acidity was 0.2 mol/L, and the rare earth decomposition rate was 95.5 %. After filtration, a rare earth solution containing iron and phosphorus is obtained, and iron and phosphorus are neutralized by magnesium oxide, and then filtered to obtain a pure rare earth sulfuric acid solution, wherein REO is 44.3 g/L, Fe 0.03 g/L, P< 0.001 g/L, Th<0.05 mg/L, pH 3.6. The pure rare earth sulfuric acid solution is directly extracted by using the non-saponified P507 extractant, and then the mixed rare earth chloride solution is obtained by reverse stripping with hydrochloric acid, and then the P507 or P204 extractant is used to extract the group or separate the single rare earth.

Example 2:

Taking iron-rich monazite ore as raw material, the iron content in the ore is 27.3 wt%, REO 25.2 wt%> P 6.6 wt%. The ore is mixed with 90 wt% concentrated sulfuric acid in the weight ratio of acid/mine = 1.7, and then continuously added to the rotary kiln, and calcined at 320 ° C for 5 hours, and the calcined ore is leached with water, and the solid-liquid ratio is 1:6. The rare earth concentration REO of the water immersion slurry is 47.16g/L, the acidity is 0.43 mol/L, and the rare earth decomposition rate is 98.2%. The water immersion slurry is neutralized with magnesium oxide and calcium oxide to recover iron and phosphorus, and filtered to obtain a pure rare earth sulfate solution (Fe 0.01 g/L, P 0.0007 g/L, One

Th<0.03 mg/L, pH 4.0) and iron phosphate concentrate.

The pure rare earth sulfate solution is produced by ammonium bicarbonate precipitation to produce mixed rare earth carbonate, then dissolved in hydrochloric acid, and P507 or P204 is extracted and separated to prepare a single rare earth compound.

Example 3:

Based on the Australian Mt. Weld monazite concentrate, the iron content in the mine is 19.7 wt%, REO 41.3 wt%, P 7.8 wt%. The ore is mixed with 95 wt% concentrated sulfuric acid in the weight ratio of acid/mine = 1.5, and then continuously added to the rotary kiln, and calcined at 300 ° C for 8 hours, and the calcined ore is leached with water, and the solid-liquid ratio is 1:11. A rare earth water immersion slurry is obtained, wherein the rare earth concentration REO is 36.61 g/L, the acidity is 0.15 mol/L, and the rare earth decomposition rate is 97.5%. After filtration, a rare earth solution containing iron and phosphorus is obtained, and iron and phosphorus are recovered by neutralizing the precipitate with magnesium hydroxide, and then filtered to obtain a pure rare earth sulfate solution (Fe 0.008g/L, P 0.0005 g/L, Th< 0.01 mg/L, pH 4.3) and iron phosphate concentrate. The pure rare earth sulfate solution is directly extracted or separated from the single rare earth by a non-saponified mixed extractant of P204 and P507.

Example 4:

In the iron-rich monazite ore (the iron content of the mine is 37.3 wt%, REO 22.2 wt%, P6.6 wt%), 61 wt% of strontium ore containing rare earth is added, and the proportion is 30 wt% of the original ore, and then with 98 ^% concentrated sulfuric acid is mixed in the weight ratio of acid/mine = 1.9, and then continuously added to the rotary kiln, calcined at 500 ° C for 6 hours, and the calcined ore is leached with water. The solid-liquid ratio is 1: 7, the water-immersed slurry is rare earth. The concentration REO was 46.2 g/L, the acidity was 0.15 mol/L, and the rare earth decomposition rate was 95.6%. The aqueous immersion slurry is neutralized with calcium oxide to recover iron and phosphorus, and filtered to obtain a pure rare earth sulfuric acid solution (Fe <0.05 g/L, P <0.001 g/L, Th<0.08 mg/L, pH 4). Pure rare earth sulfuric acid solution is directly extracted with non-saponified P204 and P507 mixed extractant, and then stripped with hydrochloric acid to obtain mixed rare earth chloride solution, and then extracted by non-saponified P507, ?272, naphthenic acid extractant or Separate a single rare earth.

Example 5

Taking monazite concentrate as raw material, the iron content in the ore is 23.5 wt%, REO 44.6 wt%, P8.1 wt%. The ore is mixed with 95 wt% concentrated sulfuric acid in the weight ratio of acid/mine = 1.7, and then continuously added to the rotary kiln, calcined at 380 °C for 4 hours, and the calcined ore is leached with a 0.05 mol/L dilute hydrochloric acid solution to solidify. The liquid ratio is 1:10, the rare earth concentration REO of the water immersion slurry is 42.4 g/L, the acidity is 0.12 mol/L, and the rare earth decomposition rate is 95.0%. The aqueous immersion slurry is neutralized with magnesium oxide to recover iron and phosphorus, and then filtered to obtain a pure rare earth sulfate solution (Fe 0.005 g / L, P 0.0005 g / L, Th <0.01 mg / L, pH 4.5). The pure rare earth sulfate solution is produced by the sodium carbonate precipitation method to produce mixed rare earth carbonate. The mixed rare earth carbonate is dissolved in hydrochloric acid and extracted by P507 to prepare a single or complex rare earth compound.

Claims

Claim

A method for smelting a rich iron monazite rare earth ore, characterized in that: the iron-rich monazite rare earth ore contains 8 wt% to 40 wt% of iron, and the smelting method comprises the following technical features:

1) the iron-rich monazite rare earth ore and concentrated sulfuric acid are mixed according to the weight ratio of acid/mine = 1~2;

2) The mixture is calcined at a temperature of 231-600 ° C for 1-20 hours, and the iron-rich monazite rare earth mineral reacts with sulfuric acid to form a rare earth sulfate which is soluble in water or a solution having a H+ concentration of less than 1.5 mol/L, and the iron forms sulfuric acid. At least one of iron, iron phosphate, and iron pyrophosphate;

3) roasting ore water or a solution having a H+ concentration of less than 1.5 mol/L is leached to obtain a rare earth water immersion slurry containing iron and phosphorus, the rare earth concentration REO is 20-55 g/L, and the H+ concentration is less than 1.5 mol/L, rare earth The decomposition rate is greater than 95%.

The method for smelting iron-rich monazite rare earth ore according to claim 1, characterized in that: in the step 1), the iron-rich monazite rare earth ore is used as the Australian Mt. Weld monazite For mines or concentrates, the iron content in the ore is 15 wt% - 40 wt%, REO 18 wt% - 60 wt%; the mixing weight ratio of concentrated sulfuric acid with ore content ≥ 90% is acid/mine = 1.3 - 1.69; In the step 2), the calcination temperature is 231-400 ° C, and the calcination time is 2-12 hours; in the step 3), the roasting ore is leached with water to obtain the rare earth water immersion of iron and phosphorus containing sulfuric acid. The rare earth decomposition rate in the slurry is greater than 97%.

The method for smelting iron-rich monazite rare earth ore according to claim 1 or 2, characterized in that: in the step 3), roasting mineral water or a solution having a H+ concentration of less than 1.0 mol/L Leaching, solid-liquid weight ratio of 1: 5 - 1: 12, and after filtration, the obtained rare earth solution containing iron and phosphorus has a rare earth concentration REO of 25-55 g/L and a H+ concentration of 0.05-1.0 mol. /L.

The method for smelting iron-rich monazite rare earth ore according to claim 3, wherein in the step 3), the calcined ore is leached with water, and the solid-liquid weight ratio is 1: 7-1. : 10, the rare earth concentration REO of the obtained iron and phosphorus-containing rare earth solution is 30-50 g/L, and the H+ concentration is 0.1-0.5 mol/L.

The method for smelting iron-rich monazite rare earth ore according to any one of claims 1 to 4, characterized in that: the rare earth water immersion slurry containing iron or phosphorus or the rare earth sulfate containing iron or phosphorus The solution neutralizes and recovers iron and phosphorus with at least one compound containing magnesium, calcium, aluminum oxide, hydroxide, carbonate, and then filters to obtain a pure rare earth sulfuric acid solution, wherein Fe<0.05g/L , P < 0.001 g / L, Th < 0.1 mg / L, pH 3-5.

The method for smelting iron-rich monazite rare earth ore according to claim 5, characterized in that the rare earth water immersion slurry containing iron or phosphorus or the rare earth sulfuric acid solution containing iron and phosphorus is made of magnesium oxide or hydroxide. Magnesium, magnesium carbonate, Neutralizing at least one of calcium oxide, calcium carbonate, calcium hydroxide and calcium carbide slag, returning iron and phosphorus in the form of iron phosphate, and obtaining a pure rare earth sulfuric acid solution containing Fe<0.005g/L, P<0.0005g /L, Th<0.05 mg/L, pH 3.5 - 4.5 ο

The method for smelting iron-rich monazite rare earth ore according to claim 5 or 6, wherein the pure rare earth sulfate solution is directly extracted by an acidic phosphorus extractant or separated to prepare a mixed or single rare earth compound.

The method for smelting iron-rich monazite rare earth ore according to claim 5 or 6, wherein: the pure rare earth sulfuric acid solution is extracted by using an acidic phosphorus extracting agent or a carboxylic acid extracting agent; The mixed rare earth chloride or rare earth nitrate is prepared by stripping with hydrochloric acid or nitric acid, or further extracting and separating the rare earth.

The method for smelting iron-rich monazite rare earth ore according to claim 5 or 6, wherein the pure rare earth sulfate solution is produced by using ammonium hydrogencarbonate, sodium carbonate or sodium hydrogencarbonate precipitation to produce mixed rare earth carbonate.

The method for smelting iron-rich monazite rare earth ore according to claim 9, characterized in that: the mixed rare earth carbonate is dissolved by hydrochloric acid or nitric acid, and then extracted and extracted by using an acidic phosphorus extracting agent or a carboxylic acid extracting agent. Single or mixed rare earth compounds.

The method for smelting iron-rich monazite rare earth ore according to claim 1 or 2, wherein in the step 2), the tail gas generated during the roasting process of the iron-rich monazite rare earth ore sulfuric acid is passed through The sulfuric acid is recovered by leaching, or discharged after being absorbed by the lye.