AU593012B2

AU593012B2 - Treatment of rare earth ores

Info

Publication number: AU593012B2
Application number: AU62438/86A
Authority: AU
Inventors: Frederic Fabre; Claude Magnier; Jean-Paul Tognet
Original assignee: Rhone Poulenc Specialites Chimiques
Current assignee: Rhone Poulenc Specialites Chimiques
Priority date: 1985-09-10
Filing date: 1986-09-08
Publication date: 1990-02-01
Anticipated expiration: 2006-09-08
Also published as: CN1009115B; ZA866838B; EP0216687B1; KR870003219A; NO863571L; FR2587036A1; CA1284886C; EP0216687A1; JPS6260833A; CN86105862A; FI863610A0; ATE45389T1; FI863610L; AU6243886A; DE3664929D1; BR8604288A; NO863571D0

Abstract

1. A method of treating an ore containing lanthanides and yttrium, including a first stage comprising grinding the ore, followed by a second stage comprising reacting the ground ore with a concentrated aqueous alkali metal hydroxide solution at an elevated temperature, characterised in that grinding is carried out in the presence of a concentrated aqueous alkali metal hydroxide solution at a temperature of up to 100 degrees C.

Description

F COMMONWEALTHOF AUSTRAL 9 3 0" 1 2 FORM PATENTS ACT 1952 CO0M PL ET E SPE C I FI C ATIO N FOR OFFICE USE: Class Int .Cl-Ass Application Number: f Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: This docuuict contains the aediens matde under Section 49.

and is oorrect Nrpralot

I

4 Name of Applicant: Address of Applicant: Actual Inventor: RHONE-POULENC SPECIALITES CHIMIQUES 11LES

MIROIRS"I

18 AVENUE D'ALSACE, 92400 COURBEVOXE,

FRANCE

FREDERIC FABRE, JEAN-PAUL TOONET AND CLAUDE MAGNIER Address for Service: SHELSTON WATERS, 55 Clarence Street, Sydney Complete Specificat~ion for the Invention entitled: "TREATMENT OF RARE EARTH ORES" The following statement is a fuill. desoription of this invention, including the best method of perforrming it known to me/us:- -1Ila tMETHOD OF TREAT'MENT FOR RARI, EARTH ORS This invention relates to a process for the treatment of rare earth ores. It deals, more particularly with an improvement to the method for treating rare earth ores with an alkaline metal hydroxide in order to obtain rare earth hydroxides.

The invention deals more specifically with the treatment of these ores with sodium hydroxide.

Previous methods in general consisted of thoroughly crushing, dry or in water, a rare earth ore such as monazite and then treating it with a concentrated ao ieous solution of sodium S hydroxide at high temperature. Paten. lJS-2 811 411 for example, describes a method where the ere is crushed so 100% of the 9* particles pass through a screen with a 74 jm mesh and 95 to 98% Sthrough a screen with a 44 um mesh. This patent states that the attack by the sodium hydroxide is more complete and the reaction time shorter if the ore is more finely crushed. The crushed ore is then treated with a solution of sodium hydroxide at a concentration of 30 to 70% by weight at temperatures from 135 to 220 0

C

for 1 to 3 hours. The ponderal ratio between the sodium hydroxide S0 and the ore is from 2 to 3.

This method i'as the disadvantage of creating high fuel costs due to the necessary prolonged crushing.

t If the ore is dry crushed it produces very fine dust which is difficult to collect. Losses are inevitable. It also has the added drawback of being radioactive like the ore itself.

This method is therefore unsatisfactory both from the economic point of view (loss of the dust, i.e. the crushed ore) and the ecological point of view (radioactivity of the dust).

If the ore is crushed in water, the pulp leaving the crusher is naturally diluted. The attack to which it is ultimately subjected needs to take place in a concentrated medium.

Consequently, the pulp has to be decanted after crushing to eliminate as much water as possible. A decanter or filter becomes necessary thereby inyolving additional cost.

T

he decanted pulp frequently contains between 25 and 40% of water.

This leads to the necessity of using large quantities of costly b 9 i r 2 soda flakes in the subsequent stages to obtain the required concentration of soda.

Finally, the fineness of the crushing required for the conventional methods is time consuming.

G.A. feerson and Li ian Khek Russ. Met 1967, 1.20 described an experimental study of the treatment of monazite which consisted of simultaneously crushing and attacking the ore with sodium hydroxide in a laboratory ball mill at a temperature of 175 to 200 0 C. using a sodium hydroxide solution at 40 or 50%, a quantity which reoresents 135 to 150% of the stoichiometry. The duration of the treatment with sodium hydroxide at 50, a quantity S representirg150% of the stoichiometry was 4, 5 and 6 hours at 175 C a'nd 3 hours 15 minutes at 200oC. Such a method cannot be transposed to the industrial level. Industrial crushers able to 0* stand up to such conditions for any length of time simply do not exist.

The applicant has discovered a method which overcomes the drawbauks of this industrial procedure. It offers cost advantages as well as advantages at th- ecological level. It also has the advantage of aiding the subsequent attack on the rare earth ore.

This procedure can be used industrially, with conventional machinery and materials, unlike that described by G.A. Meerson and Li Man Khek.

i The objective of this invention is a method for treating a rare earth ore which in a first stage involves the ore being crushed and in a second stage the ore is attacked with a concentrated alkaline metal hydroxide aqueovus solution at a hign temperature, characterised by the crushing taking place in an aqueous solution of the hydroxide of an alkaline metal at a temperature of 100QC or less.

In accordance with the invention, the rare earth ore is crushed with an alkaline metal hydroxide such as sodium hydroxide, potassium hydroxide or a mixture of these.

Soda is preferred.

Tn the explanation of the invention which follows we define the quantities and the concentrations of soda used, these can easily be extrapolated by an expert should the soda be replaced r-x-ii;-;i*ttr~Frr- x 3 by another alkaline metal hydroxide.

The rare earthores used are all ores which can be treated with an alkaline metal hydroxide. Consequently, monazite, xenotime and fluicarbonates containing rare earths will be discussed, e.g. bastnaesite as we.l as mixtures of these such as monazite-bastnaesite.

According to the invention, when we speak of rare earths we mean the elements of the periodic classification with atomic numbers from 57 to 71, yttrium being number 39. The rare earth ores treated in accordance with the invention may contain these elements in extremely variable quantities.

In the procedure according to the invention, the crushing of the ore in a concentrated solution of alkaline metal hydroxide can be done in any way whatsoever, for.example in a turning or vibrating rod crusher or ball mill.

In this invention, by concentrated aqueous solution of sodium hydroxide, we mean an aqueous solution with concentrations of sodium hydroxide of 30 to 70% by weight. A commercial soda lye at 48 to 50% by weight is recommended.

The ponderal ratio sodium hydroxide/ore used at the crushing stage, in accordance with a first variation of the invention is from 0.1 to 2.5 and preferably from 0.5 to 1. In a second variation this ratio is 0.1 to 1 and preferably 0.2. to In the first variation all the sodium hydroxide necessary for a total reaction is employed at the crushing stage. In the second variation a part only of the sodium hydroxide needed for a complete reation is employed at the crushing stage, the remainder being added at the next or 'attack' stage. Preferably, the quantity of sodium hydroxide used in total for both stages is such that the 4' 30 ponderal ratio, sodium hydroxide/ore is less than 1 and preferably Sstill, more than or equal to 0.80 and less than or equal to 0.95.

The temperature at the time of crushing may reach approximately 90 to 100 preferably 60 0 C or less. The crusher may be cooled by spraying it with water or a jacketer crusher with a cooling fluid circulating in it may be used.

*t The ore may be crushed in an open cycle until the particles are of a size so that 40% by weight or less fail to pass TECu^\ f/^UL through a 40 micron screen. Particularly good results were obtained when the size of these particles was such that 20% or less were left in a 40 micron screen.

The crushing time usually varies between 30 minutes and 2 hours.

The crushed ore is then heat treated with a concentrated solution of sodium hydroxide forming a pulp. This process takes place in the conventional manner. The temperature may vary from 100 to 220°C, preferably from 130 to 18000 and the pressure from atmospheric pressure to 3.10 Pa. The duration is a function of the temperature and pressure and may be from 1 to 10 hours. The reaction medium should be energetically agitated during this attacking stage.

After this attack, it is known that the pulp is water .iluted and that the rare earth hydroxides are later separated from the sodium hydroxide solution or sodium phosphate if monazite and fluoride are being treated and sodium carbonite if basnaesite is S being treated.

In another method, in keeping with the invention, the 20 first stage consists of controled crushing of the ore. After it S has been attacked and diluted in the reaction medium and before the hydroxides are separated from the rare earth hydroxides, the ore particles are sorted by granulometry so that the larger, only partially attacked particles may be recycled to the crushing stage.

The quantity of sodium hydroxide used and the temperature remain the same as previously stated.

By controled crushing we mean crushing until more than of the particles will not pass through a 40 micron screen.

The crushing time is usually shorter and may vary from 15 minutes to 1- hours.

With this procedure, the partially attacked granules, Si.e the larger ones are recycled the granulometric cut-off is selected at about 10 to 100 um, preferably 10 to 40 um. The smaller particles go to the stage of separation of the rare earth hydroxides. This granulometric sorting can only take place once the pulp obtained after the attack has been diluted. A hydroseparator or preferably an hydrocyclone is used.

Nib- Compared to the conventional methods, the procedure used in the invention permits a saving of fuel thanks to the ore being crushed into larger particles requiring a shorter crushing period.

The procedure in accordance with the invention has the following advantages no polution from radio-active dusts, the ore is not diluted in water before the attacking process in the concentrated soda which follows. Thus in the last stage, i.e. the leaching, industrial soda at 48 to 50% can be used which is far more economical than anhydrous soda. In a controled crushing and the subsequent dilution caused by recycling the larger particles, there is less dilution than there would be had they been crushed in water, this method also has the advantage that it reduces the crushing time.

Finally, and this is one of the more important aspects, 4 the applicant has discovered that this method of crushing causes the ore to be more reactive in the attacking stage which follows it. It creates, in fact, a pre-attack on the ore. The level of attack in the conditions menbioned varies between 5 and dQ (in comparison at 1100C a monazite previously crushed at 100%' 40 Pm is only attacked at after about 10 hours of intense agitation. This demonstrated the advantage and the specific Scharacter of the crushing in soda).

In accordance with the invention therefore, this procedure makes the ore more reactive and obtains in the final attack stage.higher yields with lower fuel costs due to less crushing being necessary coarser granulometry and a shorter crushing time).

This procedure also economises substantially in sodium hydroxide compared to conventional methods. The ponderal ratio total amount of sodium hydroxide/ore being less than 1 and even 0.95 or less, whereas in the procedure described in patent US-A-2 811 411 this ratio is 2 to 3.

The exampls which follow illustrate this invention Examole 1 Malayan monazite with the following composition is used 1C-p- 6 COMPOSITION PERCENTAGE BY WEIGHT ThO 2 6.8 Rare earth oxides 59.7 P205 27.1 SiO 2 1.9 ZrO 2 0.7 TiO 2 0.8 the dry crushing takes place concurrently dry and in the soda.

SThe dry crushing is continuous in a closed cycle ball mill on an air selector.

I The crushing with soda is continuous and is done in an open cycle ball mill. The crushing time (average time the ore is in the crusher) is 1 hours. The crusher is kept at a temperature of 60°C below the atmospheric pressure.

'«The fuel used is 95 kWh/T or- in the first instance and only 35 kWh/T in the second.

,o0 After crushing, the ore from the dry crushing and the pulp from the crushing with soda are each placed in a reactor for the attack process.

In both instances, this stage takes place in the follow- S ing conditions identical period of time atmospheric pressure a temperature of 1470C identical total quantity of soda used.

The soda is industrial lye with initially 48% soda by weight.

The total amount of soda used is such that the ponderal ratio soda is 0.85% (for 1 T of ore, 850kg. of pure soda at 100%).

oreFor the dry crushed ore, all the soda is added at the attacking stage.

For the procedure according to the invention, half the soda is placed in the crusher with the ore, the remainder is added when it leaves the crusher, just befoe the attack.

I.

C

VIA

2 7 When the crushing with soda, in accordance with the iiivention is over, the rate of attack of the ore is 6/6 by weight.

The results are the folloving: Dry crushing Crushing in soda

II

LI

Ii

I

Attack yield of Ithe rare earths 9 1 "6 96.3 1~ 6

I

tilt 4' 4' I I I

I

it?- I I

II

A test, identical to that in example I is carried out on Australian monazite with the following composition: (2UNPOSITION NPIRCf,'TAG-IE BY *NVIGHLT ThO 2 7.-3 "6 P~are earth oxides 58.9 ;n' P 2 0 5 28.0 Sio 2 1.1

ZCO

2 1.9 7 TiO 2 01~ The results are the following: I i.

I I I FDry crushing Crushing in soda Granuloraetry 80 pm 0 1,1T 2. 9 of ore after -6 3 Lim. 0 6 crushing -40 PM 0 14.4 Attack yield of 1 95.2~ the rare earths

Claims

1. Method for treating a rare earth ore comprising a first stage which consists of crushing the ore, and a second stage which consists of attacking the crushed ore with a concentrated aqueous solution of alkaline metal hydroxide at a temperature of between 100 0 C 2200C, characterised by the crushing taking place with the inclusion of a concentrated aqueous solution of alkaline metal hydroxide at 100 0 C or less.

2. Method according to Claim 1, characterised by the alkaline metal hydroxide being sodium hydroxide.

3. Method according to Claim 2, characterised by the ponderal ratio sodium hydroxide/ore being 0.1 to 2.5 for the crushing.

4. Method according to Claim 3, characterised by the ponderal ratio sodium hydroxide/ore being 0.5 to 3 for the crushing. Method according to Claim 2, characterised by the ponderal ratio sodium hydroxide/ore being 0.1 to 1 for the crushing.

6. Method according to Claim 5, characterised by the ponderal ratio sodiuim hydroxide/ore being 0.2 to 0.5 for the crushing.

7. Method according to any one of Claims 2 to 6, characterised by the quantity of sodium hydroxide added in total in both stages being such that the ponderal ratio sodium hydroxide/ore is less thar 1.

8. Method according to Claim 7, characterised by the quantity of sodium hydroxide added in total in both stages being such that the ponderal ratio sodium hydroxide/ore is more than or equal to 0.80 and less than or equal to 0.95. 1 9. Method according to any one of Claims 2 to 7, characterised by the crushing being carried out with an aqueous solution containing from 45 to 50% by weight of P. sodium hydroxide. Method according to any one of the previous Claims 1 I to 9, characterised by the crushing taking place at a temperature of 60 0C or less. 1-1. Method according to any one of the previous Claims 1 to 10, char~acterised by the crushing of the ore in an open cycle being continued until a size of particle is obtained where 40% or less fails to go through a 40 micron screen.

12. Method according to Claim 11, characterised by 20% or less failing to pass through a 40 micron screen.

13. Method according to any one of Claims 11 and 12, characterised by the crushing time being between minutes and 2 hours.

14. Method according to any one of the previous Claims 1 to 13, characterised by the temperature in the second stage being between 130 and 180 0C Method according to any one of Claims 1 to 10 and 14, characterised by controlled crushing of the ore before it is attacked by hydroxide and by recycling of the particles partially attacked by hydroxide to a controlled crushing step.

16. Method according to Claim 15, characterised by the ore being crushed until particles are obtained so that more than 20% fail to pass through a 40 micron screen.

17. Method according to any one of Claims 15 and 16, .characterised by the cut-off point for the granulometry being selected at about 10 to 100pm. 4,18. Method according to any one of Claims 15 to 17, characterised by the crushing time varying between 15 minutes and 1 hour 30 minutes, DATED this 27th uay of October 1909 RHONE-POULENC SPECIALITES CHXMIQUES Attorney: IAN T. ERN$T Fellow Institute of Patent Attorneys of AUs~.ralia of SHEI.STON WATERS i