WO2016001045A1

WO2016001045A1 - Method for the thermal decomposition of a rare earth ore concentrate

Info

Publication number: WO2016001045A1
Application number: PCT/EP2015/064325
Authority: WO
Inventors: Bernd Friedrich; Marc Hanebuth; Stephanie KRUSE; Alexander Tremel; Daniel VOSSENKAUL
Original assignee: Siemens Aktiengesellschaft
Priority date: 2014-07-03
Filing date: 2015-06-25
Publication date: 2016-01-07
Also published as: DE102014212908A1

Abstract

The invention relates to a method for thermally decomposing a rare earth ore concentrate, characterized in that the rare earth concentrate (2) is introduced into a fluidized-bed reactor (4) and is thermally decomposed therein, and thermal decomposition products are continuously discharged from the fluidized-bed reactor (4).

Description

description

Process for the thermal decomposition of a rare earth ore concentrate

The invention relates to a process for the thermal decomposition of a rare earth ore concentrate according to the preamble of claim 1. In rare earth-containing ores rare earths (compounds of rare earth elements) are bound. In the case of the mineral bastnaesite, the rare earth elements are bound in fluorocarbonates. These are difficult to hydrometallurgically process directly, which is why they are thermally decomposed. In this case, the carbonate is decomposed under oxidizing conditions and thereby split off carbon dioxide, wherein the rare earth element, for example, the cerium is oxidized by the oxidation dation +3 to the oxidation state +4. This can be separated hydrometallurgical subsequently, as opposed to the trivalent oxide, it has a lower Lös ^¬ friendliness.

The same applies to phosphate-containing rare earth minerals, such as monazite, from which rare earth elements are also obtained on a larger scale.

Concentrates of these minerals, such as the

Bastnäsitkonzentrat, are applied in the art usually with sulfuric acid and then reacted in a rotary kiln at temperatures between 500 ° C and 700 ° C thermally to rare earth sulfates or a pure thermal Be ^¬ treatment (ie without addition of sulfuric acid) into oxides ^¬ converts. In the purely thermal splitting of bastnasite, either rotary kilns or stack kilns are also used, which are characterized by a very high energy requirement. Furthermore, such ovens are particularly susceptible to wear due to their rotating parts at very high temperatures. The object of the invention is to provide a process for the thermal decomposition of rare earth ore concentrates, which is less expensive and more energy efficient than the prior art.

The solution of the problem consists in a method having the features of claim 1. The inventive method according to claim 1 is used for the thermal decomposition of a rare earth ore concentrate. Here, rare earths are, as already mentioned, compounds of rare earth metals, whereby the rare earth metals are understood as the metals that are commonly referred to in the chemical as lanthanides (here, because of the chemical relationship of yttrium and scandium also understood by the term rare earth metals) , Here, the lanthanum, the yttrium and the scandium are to be added to this group. These rare earths are finely distributed in minerals such as bastnasite or monazite. To concentrate these rare earths finely distributed in the designated minerals, physical methods such as the flotation method are commonly used. Furthermore, here the term rare earth ore concentrate is understood to mean a concentrate which has already been preconcentrated from maternal ore, such as bastnasite on rare earths. In these rare earth ore concentrates (hereinafter referred to as SE concentrate) are compounds of rare earth elements in ge ^¬ mixed form. The concentration of the individual rare earth elements in the SE concentrates differs depending on the ore and the mining area.

The invention is characterized in that the SE concentrates are placed in a fluidized bed reactor and thermally decomposed there, the products being continuously removed from this thermal decomposition from the fluidized bed reactor. The rotary kiln customary in the prior art is inventively by a fluidized bed reactor replaced, which means that even wear-prone and maintenance-intensive rotating parts in thermal Zerset ^¬ tion method can be dispensed with and at the same time a continuous process can be used, which is much more energy efficient compared to the conventional rotary kiln.

The solid products, which are continuously removed from the Wirbelbettre ^¬ actuator, are separated either in a filter or in a cyclone.

It is expedient that the SE concentrates are admixed with additives in the form of oxides or hydroxides of alkali metals or alkaline earth metals before they are reacted in the fluidized-bed reactor. The addition of these additives usually leads to a more favorable thermodynamic reasons digestion of the SE concentrates so that effectively lower temperatures, ver ^¬ pared with the situation without additives necessary for the conversion.

It is expedient that the SE concentrates are pressed together with the ad ^¬ ditiven so that the additives lichst mög ^¬ be close to the SE-concentrates and already adjacent microscopically with these together. Here, it may also be expedient that instead of a pressing operation Bezie ^¬ hung example next to a pressing operation of the SE-concentrates with the additives is a thermal pretreatment of the mixture takes place, so that the additives are melted (e.g., at low ^¬ melting hydroxides) and fused to the SE Place concentrates around. Furthermore, the additives, in particular in the form of oxides with the SE concentrates, can form a sintered compound based on diffusion processes. In addition, two example reactions are mentioned below. In the case of a phosphorus-containing mineral as the starting material for the SE concentrates, such as monazite, an exemplary reaction proceeds as follows: GL1: 2 SEP0 ₄ + 3CaO = SE ₂ 0 ₃ + Ca ₃ (P0 ₄ ) ₂

In a carbonate mineral as starting material the SE concentrates, such as the Bastnäsit, exempla ^¬ driven following reaction occurs:

GL2: CaO + 2 SEF (C0 ₃ ) = SE ₂ 0 ₃ + CaF ₂ + C0 ₂ where each SE stands for any rare earth element. In addition to the addition of additives, carbon-containing fuels can also be added to increase the reaction temperature. In this case, particular mention should be made of heavy oil, which in particular contains sulfur. The addition of sulfur in elemental form or in a compound can be fed to the SE concentration, this means that little or hardly rare earth oxides are formed in the thermal decomposition of the SE concentrates, but rather rare earth sulfates or, depending on the reaction, rare earth sulfites gebil - det, which are more soluble than the oxides. Here ^¬ by the further processing and separation of the rare earth elements is facilitated by other elements.

In a further embodiment of the invention, the fluidized bed reactor is designed such that it preferably widens conically towards the top, which means that only small particles that have already reacted in the described reaction regime leave the fluidized-bed reactor. In addition, the conical shape increases the residence time, as a result of which the particles have sufficient time to react

Further embodiments of the invention and further features will be described with reference to the following figures. Showing:

1 shows a method for the separation of rare earth concentrates using a fluidized bed reactor with an affiliated cyclone and

Particle recycling, and

Figure 2 is a fluidized bed reactor for use of the same

Method, which widens conically upwards and to which a filter is connected.

Both in Figure 1 and in Figure 2, the application of a fluidized bed reactor 4 for the decomposition of SE concentrates 2 is shown. Device features or process features having the same designation and meaning, but different embodiments in the two examples of Figure 1 and Figure 2 are given the same reference number but with an appended ^λ .

The focus of the described method is a vortex ^¬ bed reactor 2, in which a SE-concentrate is fed via a charging device 24 continuously. The SE concentrate 2 is initially in a fluidized bed 5. By a PrimärluftZuführung 8 air or combustion gas is supplied at a preferred temperature between 10 ° C and 800 ° C. The fluidized bed 5 has a fluidization unit, not shown here, through which the primary air 8 can flow through ^¬ . Typically, the fluidization unit, also referred to as the distributor plate, is 90% to 97% covered with the SE concentrate, so that 3% to 10% of the area through which the primary air 8 can flow is free. For heating the primary air 8 here also not shown burners are used at the bottom of the fluidized bed reactor 4. In addition, a further separate air supply 14 may be provided. Alternatively, a hot exhaust gas of an externally occurring combustion can serve as an air supply. The regulation of this air supply or gas supply determines the flow velocity of the fluidization unit. If the vortex point, that a certain flow rate is exceeded, it comes to fluidize the material, so the SE-concentrate 2. That is, it forms a so-called fluidized bed of ^¬. A vortex point is reached when Are friction and buoyancy forces with the weight of a ^¬ individual particles in balance. The SE concentrate 2 is characterized by fine granularity, wherein the particles are ideally spherical. A particle size is preferably in a range between 10 .mu.m and 5 mm, preferably between 50 .mu.m and 1 mm, but is characterized by a preferably largely uniform size.

The so-called bed material preferably consists of the reaction onsukte, either alone from the SE concentrate or a mixture of the SE concentrate and Additi ^¬ ven, in which case the SE concentrates should be present directly in the ^{erforderli ¬} chen particle size to fluidized to become. Alternatively, it is also possible to form the fluidized bed 5 from a homogeneous inert bed material, such as sand. It is now also possible to introduce rare earth ore concentrates having a broader particle size distribution into this bedding material. By the heat input of the combustion air, by the

Primary air supply 8 or 8 ^{λ is introduced} in Figure 2 and the oxygen in the air, the SE-Erzkonzentrat is decomposed ther ^¬ mixed. The gas release occurs, for example, after the reaction:

GL3: 3 SEF (C0 ₃ ) -> SE ₂ 0 ₃ + SEF ₃ + 3 C0 ₂

The friction of the particles in the fluidized bed leads to a

Reduction of particle size. As a result, the solid, dusty reaction products largely on the

Exhaust path (as fine dust) together with gaseous compo ^¬ nents (for example, CO2) are discharged. This is done through the openings 20 and 20 ^λ in the fluidized bed reactors 4 shown in Figure 1 and Figure 2.

Equation 3 described here corresponds to a reaction without the addition of additives. In an advantageous manner, additives in the form of oxides or hydroxides can be added to the SE concentrate. xiden the alkali or alkaline earth metals are added. Such additives typically cause a beneficiaries ^¬ preferential reaction with the SE-concentrates, which reduces the total energy input in the process described for the implementation of SE-ore concentrates. Corresponding exemplary

Equations are already given with respect to equation 1 and equation 2.

Gaseous and solid products are continuously discharged from the fluidized bed. For solid products, the effect is utilized, that the particles are finely verrie ^¬ ben for sufficiently long residence time due to friction within the fluidized bed 5 and are then discharged as flue dust. The fes ^¬ th products are then conveniently in a filter (Figure 2) or in a cyclone (Figure 1) separated from the gas phase, wherein the remaining exhaust gas is fed to a post-treatment. This is conveniently carried out by a gas scrubbing, not shown, with a basic washing solution. The fact that the exhaust gas is withdrawn continuously, in combination with a continuous charging of SE concentrate, means that the reaction does not come to a standstill due to an equilibrium that occurs. A continu ^¬ ous reaction is generally compared to a charge linked reaction decisive technical process advantage since this allows a higher throughput per unit time.

In the fluidized bed reactor 4 according to Figure 1, a fuel supply 10 is provided laterally in the region of the fluidized bed 5, can be supplied by the additional fuel, such as heavy ^¬ oil, in order to influence the reaction temperature, or to increase as a whole. Basically, a fuel in the form of coal or oil can also been fed to the Rare-earth or a mixture of Rare-earth and additives ^¬ to. The supply of sulfur or sulfur-containing compounds to the rare earth concentrates, preferably before charging, leads to thermal decomposition SE-Seltenerdsulfite concentrates are respectively formed rare ^¬ erdsulfate which are with respect to a solubility in common solvents advantageous over rare earth oxides.

To increase the reactivity of the concentrates with respect to the SE-mentioned additives, it is desirable to produce a Mi ^¬ research between these two materials and be subjected to a thermal pretreatment. Depending on the temperature, depending on the type and melting temperature or diffusion behavior of the additive, either sinter-like connections between the SE concentrates and the additives or melt connections between the SE concentrates and the additives can be formed. This close connection between the two components promotes a further reaction in the fluidized bed reactor and leads to a uniform and complete reaction sequence.

In the following, the different structures of the reactors 4 and 4 ^λ in FIG. 1 and FIG. 2 will be discussed in greater detail. In the fluidized bed reactor 4 according to Figure 1 is a reactor which is constructed substantially cylindrical and at the top of a gas / solids outlet 20, wherein the gas and the solid is transferred into a cyclone 6, in which the gas and the solid ^{voneinan ¬ are} separated. In this construction, fine and coarser particles are deposited through the outlet 20, wherein the coarser particles are brought back via a siphon 18 from the cyclone 6 back into the fluidized bed 5. Fine, thermally decomposed rare earth particles, which are present in the form of the desired sel ^¬ tener oxide or sulfite or sulfates or - fluorides, are supplied via an outlet 16 to a cooling and further processed according to the rare earth element preparation.

Furthermore, the discharge of fine product particles with the gas stream 21 can also take place. The separation is then again by a cyclone or another separation process. With this structure, multi-stage fluidized beds and recirculations are possible.

Alternatively, the fluidized bed reactor 4 ^λ is configured in Figure 2 so that it widens conically upwards, which leads to the fact that upwards the buoyancy force is reduced by the sinking flow velocity and thus decreases the force acting on the particles. Depending on the size and density of a particle, there is therefore an area in which it can remain in equilibrium. Smaller and thus already reacted particles are discharged via the outlet 20 and fed to a filter 26. Via an exhaust pipe 21, the exhaust gas is derived and processed analogous to Figure 1. The filter material 26 taken, already converted SE material in the form of SE oxides or sulfates, sulfites or fluorides is also fed to a further treatment. A combination between the two described reactor types with the two different separation processes, filters and cyclones is possible.

Claims

claims

1. A process for the thermal decomposition of a rare earth ore concentrate, characterized in that the rare earth ore concentrate (2) is placed in a fluidized bed reactor (4) and thermally reacted there and products from the thermal reaction continuously from the fluidized bed reactor (4) be dissipated.

2. The method according to claim 1, characterized in that solid products in a filter or in a cyclone (6) are derived.

3. The method according to claim 1 or 2, characterized in that the rare earth ore concentrates (2) before the reaction in

Fluidized Bed Reactor (4) Additives in the form of oxides or hydroxides of alkali or alkaline earth metals are added.

4. The method according to any one of claims 1 to 3, character- ized in that the rare earth ore concentrate (2) to a

Grain size between 10 ym and 5 mm is ground and mixed with the additives.

5. The method according to any one of the preceding claims, character- ized in that the rare earth ore concentrates (2) are pressed or fused with the additives.

6. The method according to claim 4 or 5, characterized in that a mixture of rare earth ore concentrates (2) and additives are subjected to a thermal pretreatment.

7. The method according to any one of the preceding claims, characterized in that the rare earth ore concentrate (2) is supplied to a carbonaceous fuel.

8. The method according to claim 7, characterized in that the rare earth ore concentrate heavy oil is supplied.

9. The method according to any one of the preceding claims, characterized in that the rare earth ore concentrate sulfur or a sulfur compound is supplied.

10. The method according to any one of the preceding claims, characterized in that the fluidized bed reactor (4) widens si upwards.