OA17900A - Roasting of sulfur-poor metal oxide concentrates. - Google Patents
Roasting of sulfur-poor metal oxide concentrates. Download PDFInfo
- Publication number
- OA17900A OA17900A OA1201600183 OA17900A OA 17900 A OA17900 A OA 17900A OA 1201600183 OA1201600183 OA 1201600183 OA 17900 A OA17900 A OA 17900A
- Authority
- OA
- OAPI
- Prior art keywords
- sulfur
- poor
- métal
- oxide
- concentrate
- Prior art date
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- 239000012141 concentrate Substances 0.000 title claims abstract description 63
- 229910044991 metal oxide Inorganic materials 0.000 title abstract 5
- 150000004706 metal oxides Chemical class 0.000 title abstract 5
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 58
- NINIDFKCEFEMDL-UHFFFAOYSA-N sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 57
- 239000011593 sulfur Substances 0.000 claims abstract description 57
- 239000007789 gas Substances 0.000 claims abstract description 27
- 239000000446 fuel Substances 0.000 claims abstract description 22
- 238000010438 heat treatment Methods 0.000 claims abstract description 18
- 150000003464 sulfur compounds Chemical class 0.000 claims abstract description 15
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 13
- 239000001301 oxygen Substances 0.000 claims abstract description 13
- MYMOFIZGZYHOMD-UHFFFAOYSA-N oxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 13
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 238000005201 scrubbing Methods 0.000 claims abstract description 8
- 230000000875 corresponding Effects 0.000 claims abstract description 5
- 238000010791 quenching Methods 0.000 claims abstract description 4
- 230000000171 quenching Effects 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 6
- 150000001805 chlorine compounds Chemical class 0.000 claims description 5
- 150000002222 fluorine compounds Chemical class 0.000 claims description 5
- ZKATWMILCYLAPD-UHFFFAOYSA-N Niobium pentoxide Chemical compound O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 claims description 4
- 230000005587 bubbling Effects 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 3
- IJDNQMDRQITEOD-UHFFFAOYSA-N butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims description 2
- 239000001273 butane Substances 0.000 claims description 2
- 239000000295 fuel oil Substances 0.000 claims description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 2
- 239000003345 natural gas Substances 0.000 claims description 2
- 229910000484 niobium oxide Inorganic materials 0.000 claims description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 2
- 239000001294 propane Substances 0.000 claims description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- 241001088417 Ammodytes americanus Species 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N HCl Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 5
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 5
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 description 5
- 229910052683 pyrite Inorganic materials 0.000 description 5
- 239000011028 pyrite Substances 0.000 description 5
- 150000004763 sulfides Chemical class 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- 239000010955 niobium Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L Iron(II) sulfate Chemical class [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 2
- SZVJSHCCFOBDDC-UHFFFAOYSA-N Iron(II,III) oxide Chemical compound O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical group 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- -1 niobium (Nb) Chemical class 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000002203 pretreatment Methods 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000005350 fused silica glass Substances 0.000 description 1
- 238000009854 hydrometallurgy Methods 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229910000460 iron oxide Inorganic materials 0.000 description 1
- 235000013980 iron oxide Nutrition 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- GNVXPFBEZCSHQZ-UHFFFAOYSA-N iron(2+);sulfide Chemical compound [S-2].[Fe+2] GNVXPFBEZCSHQZ-UHFFFAOYSA-N 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000004949 mass spectrometry Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229910052904 quartz Inorganic materials 0.000 description 1
- 230000001172 regenerating Effects 0.000 description 1
- 230000000717 retained Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000004449 solid propellant Substances 0.000 description 1
- 229910052950 sphalerite Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000003643 water by type Substances 0.000 description 1
Abstract
The present invention provides a method of
pre-treating sulfur-poor metal oxide concentrate,
comprising the steps of : providing sulfur-poor
metal oxide concentrate having sulfur content
below 10 % w/w; (a) heating the sulfur-poor metal
oxide concentrate at an elevated temperature and
in presence of oxygen and an external fuel source
to oxidize sulfur compounds contained in the
sulfur-poor concentrate to corresponding oxides
and/or to thermally decompose the said sulfur
compounds to obtain a sulfur-depleted oxide
concentrate and a sulfur-containing off-gas; (b)
separating the sulfur-depleted metal oxide calcine
from the sulfur-containing off-gas; (c) cooling the
obtained sulfur-depleted oxide calcine; (d) cooling
the off-gas by quenching; and (e) scrubbing the
cooled off-gas to recover sulfur.
Fig. 3
Description
Roasting of Sulfur-Poor Métal Oxide Concentrâtes
FIELD OF THE INVENTION
The présent invention relates to pre-treatment of métal oxide concentrâtes, in particular concentrâtes with low sulfur content, and provides a method of pre-treating of sulfur-poor métal oxide concentrate for removing most or ali the sulfur contained in the oxide concentrate.
BACKGROUND OF THE INVENTION
Roasting is typically applied to concentrâtes such as sphalerite or pyrite having a high heat value which provides enough energy for the heating of the roasting step and even extra energy is produced. However, this type of roasting is not possible for material with limited sulfur and carbon content.
However, there is an existing need for a method of processing concentrâtes with low sulfur and possibly also low carbon content as these concentrâtes may bearvaluable metals, such as niobium (Nb), which are scarcely available.
In order to recover scarce valuable metals from concentrâtes with low sulfur content the concentrate must be pre-treated to remove most or ail the sulfur contained in the concentrate. This allows further processing of the concentrâtes in hydrometallurgical processes which do not tolerate the présence of sulfur.
To our knowledge there are no existing methods for the pretreatment of oxide concentrâtes having a low sulfur content.
BRIEF DESCRIPTION OF THE INVENTION
It is thus an object to provide a method and an apparatus for implementing the method so as to overcome the above problems. The objects ofthe invention are achieved by a method and an arrangement, which are characterized by what is stated in the independent daims. The preferred embodiments ofthe invention are disclosed in the dépendent daims.
The invention is based on the idea of heating of oxide concentrâtes with limited sulfur content in presence of oxygen and an external fuel source which provides the energy required for oxidation and/or thermal composition of the sulfur. This is advantageously accomplished in a fluidized bed furnace, whereby the external fuel source provided by fuel lances.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described in greater detail by means of preferred embodiments with référencé to the attached drawings, in which
Figure 1 shows a first prédominance diagram for Fe-O-S Systems;
Figure 2 shows a second prédominance diagram for Fe-O-S Systems; and
Figure 3 illustrâtes a flow diagram of a first example of the method of the présent invention.
DETAILED DESCRIPTION OF THE INVENTION
The présent invention relates to a method of pre-treating sulfur-poor métal oxide concentrate, comprising the steps of: (o) providing sulfur-poor métal oxide concentrate having sulfur content below 10 % w/w; (a) heating the sulfur-poor métal oxide concentrate at an elevated température and in presence of oxygen and an external fuel source to oxidize sulfur compounds contained in the sulfur-poor métal oxide concentrate to corresponding oxides and/or to thermally décomposé the said sulfur compounds to obtain a sulfurdepleted métal oxide calcine and a sulfur-containing off-gas; and (b) separating the sulfur-depleted métal oxide calcine from the sulfur-containing off-gas;
(c) cooling the obtained sulfur-depleted oxide calcine; (d) cooling the off-gas by quenching; and (e) scrubbing the cooled off-gas to recover sulfur.
The heating step (a) can be performed in any roasterfound suitable by a person skilled in the art. The roasting step (a) can for example be carried out in a roaster selected from the group consisting of a rotary kiln, a fluidized bed reactor, such as a bubbling fluidized bed roaster, a circulating fluidized bed roaster, an annular fluidized bed roaster, and a flash reactor. In accordance with an advantageous example of the présent invention the heating step (a) is accomplished in a fluidized bed furnace. This ensures a very good mass and heat transfer. In a preferred example of the invention the fluidized bed furnace is a bubbling fluidized bed furnace or a circulating fluidized bed furnace.
The term “sulfur-poor métal oxide concentrate” refers to concentrâtes having sulfur content below 10% w/w and comprising more than 40 % w/w métal oxide, in particular from 50 to 90 % w/w métal oxide, more particularly from 60 to 70 % w/w métal oxide.
Sulfur-poor métal oxide concentrate pre-treated with the method of the invention is preferably a concentrate having sulfur content from 0.2 to 8 % w/w, more preferably from 3 to 7 % w/w. In a suitable example of the présent invention sulfur-poor métal oxide concentrate comprises niobium oxide (e.g. Nb2O5), in particular from 30 to 60 % w/w, more particularly from 50 to 60 % w/w. In a further example ofthe présent invention sulfur comprised in the sulfur-poor concentrate is mostly pyrite. In particularly suitable example of the présent invention the sulfur-poor métal oxide concentrate comprises from 30 to 40 % w/w Nb and 5 to 8 % w/w Fe.
Further in accordance with an example of the présent invention the carbon content of the sulfur-poor métal oxide concentrate is so low, that it together with sulfide it does not produce enough heat for heating material to required température. The carbon content of the oxide concentrate affects the heat value of the concentrate and thus oxide concentrate with particularly low carbon content cannot be treated with conventional pre-treatment methods.
The method of the invention advantageously provides sulfurdepleted métal oxide calcine having sulfur content below 0.2 % w/w, more preferably below 0.15 % w/w. Such pre-treated oxide calcine can be processed in by suitable hydrometallurgical methods known by person skilled in the art for recovering the valuable metals comprised in the said pre-treated oxide calcine The term “calcine” as used herein and hereafter refers to a product obtained by heating a concentrate to a high température but below the melting or fusing point, causing loss of moisture, réduction or oxidation, and at least partial the décomposition of carbonates and other compounds.
The method of the invention is applicable for removal of sulfur from a sulfur-poor métal oxide concentrate regardless of whether the sulfur is présent as sulfate(s), sulfide(s), or both. The conversion of sulfides and/or sulfates to corresponding oxides with oxygen is dépendent on the local oxygen concentration. Oxygen can be introduced into the heating step (a) for example as air, oxygen enriched air, or other oxygen containing gas, preferably as air or oxygen enriched air. The required amount of oxygen in the heating step (a) dépends on the sulfur content of the oxide concentrate and the desired sulfur content of the pre-treated oxide concentrate and the mineralogical nature of the sulfides and/or sulfates as well as carbon and/or carbonates comprised in the sulfur-poor métal oxide concentrate.
The external fuel source is preferably liquid and/or gaseous fuel, such as methane, propane, butane, natural gas or heavy oil. Use of solid fuel sources, such as sulfur bearing carbonaceous materials, is not désirable as they are easily retained in the solid concentrate and thus would not allow obtaining pre-treated material with a very low sulfur and carbon content. The fuel source is preferably proved to the roasting stage through one or more fuel lances. Fuel lance supplies the liquid and/or gaseous fuel into the furnace by a liquid-fuel passage that extends into the furnace chamber. Fuel is oxidized with oxygen containing fluidizing media. The required number of fuel lances dépends on the need of additional energy and the capacity of the plant. Fuel lances can be provided on one or more, preferably one or two, levels depending on the size of the furnace. The required amount of fuel is depended on the desired température of the heating step (a) the reaction kinetics, and thermodynamic stability.
The température of the heating step (a) must be kept within oxide stability range. This is dépendent of the nature of the sulfur-poor métal oxide concentrate, but varies typically from 500 to 1000°C depending on the minerais. Température must also be minimized to minimize the need of external fuel source. The rétention time of step (a) is depended on the mineralogical nature of the sulfur-poor ore. For example sulfur in présent as a pyrite can be easily removed in minutes. Figure 1 and Figure 2 show calculations relating to suitable conditions regarding température and oxygen pressure of the heating step (a) for oxidation of sulfur comprised in a sulfur-poor métal oxide concentrate comprising sulfur mainly as pyrite (iron sulfide) in such manner that sulfide oxidizes to iron oxides (FeO, Fe3O4 and/or Fe2O3) and no iron sulfates (FeSO4) are formed.
As the préférable process conditions of the heating step (a) are directly affected by the nature of the pre-treated sulfur-poor métal oxide concentrate the nature of the said oxide concentrate is preferably determined beforehand and the process conditions are selected accordingly. The accordance with one example ofthe présent invention the process conditions ofthe heating step (a) are determined by the steps of: (i) analyzing the nature of the sulfur compound(s) and the nature ofthe métal oxide(s) ofthe sulfur-poor métal oxide concentrate; and (ii) selecting the process conditions in such manner that the métal oxide retains it stability while the sulfur compounds are oxidized and/or thermally decomposed.
The nature of the sulfur compound(s) and the oxide(s) of the sulfurpoor métal oxide concentrate in step (i) can be analyzed by methods known suitable by a person skilled in the art. The main éléments of the sulfur-poor métal oxide concentrate can for example be analyzed by inductively coupled plasma (ICP) mass spectrometry. The sulfur content of the oxide concentrate can be determined for example by an elemental analyzer utilizing combustion techniques, such as Eltra CS2000. The chemical composition of the main components of the oxide concentrate can be analyzed for example by field émission scanning électron microscope. The main mineralogy of the oxide concentrate can be determined for example by X-ray diffraction. Preferably the nature of the sulfur compound(s) and the nature of the oxide(s) of the sulfurpoor concentrate is analyzed at least by X-ray diffraction.
The process conditions in step (ii) are then selected by performing stability calculations and utilizing thermochemical estimations, such as those shown in Figure 1 and/or Figure 2. The température of the heating step (a) can be further determined by testing the reaction température of the sulfur-poor métal oxide concentrate using a thermogravimetric/differential scanning calorimetric (TG/DSC) method which indicates the temperature(s) where the sulfur compound(s) are oxidized and/or thermally decomposed.
In accordance with a further example of the présent invention the séparation step (b) is accomplished by a cyclone. In accordance with a still further example of the présent invention cooling of calcine in step (c) is accomplished by a fluidized bed cooler.
The method of the invention is particularly suitable for the sulfurpoor métal oxide concentrate comprising small amounts chlorides and/or fluorides. Thus in an advantageous example ofthe invention the sulfur-poor métal oxide concentrate comprises chlorides and/or fluorides. The sulfur-poor métal oxide concentrate can comprise from 0 to 4 % w/w, in particular from 1 to 2 % w/w, chlorides and/or fluorides. In accordance with the method of the invention these compounds are volatilized and when présent as gaseous H F and HCl in the off-gas also removed in the scrubbing step (e). It is not possible to recycle off-gas comprising HCl and/or HF. The presence of HCl and/or HF also prevents utilization ofthe off-gas in an acid plant.
When the off-gas contains no or only minor amounts of HCl and/or HF scrubbing step (e) can be accomplished for example by regenerative scrubbing methods to recover sulfur. The wash chemicals can be recycled.
When SO2and/or HCl and/or HF are présent scrubbing in step (e) can be done for example with an aqueous alkaline solution, such as NaOH (aq) and CaOH2 (aq).
Figure 3 illustrâtes an example of the method of the présent invention. With reference to Figure 3, sulfur-poor métal oxide concentrate (1) and an extemal fuel source (2) are introduced into a roaster (A) and heated in présence of preheated air (3) to oxidize sulfur compounds contained in the sulfurpoor métal oxide concentrate to corresponding oxides and/or to thermally décomposé the said sulfur compounds, to obtain a gas/calcine mixture (4) comprising sulfur-depleted métal oxide calcine and sulfur-containing off-gas. The gas/calcine mixture is then introduced into a cyclone (B) and separated to obtain a sulfur-depleted métal oxide calcine (5) and a sulfur-containing off-gas (6). The sulfur-containing gas (6) can analyzed with a gas analyzer (G) and the process conditions of the roaster (A) can be adjusted accordingly.
With further reference to Figure 3, the obtained sulfur-depleted métal oxide calcine (5) is then cooled in a fluidized bed cooler (C) where the heat of the said calcine is utilized to heat the air (3’) entering the heating step (a). Further the air (3’) used and in the fluidized be utilized as a warm gas (13) in drying of the concentrate (1). The sulfur-containing off-gas (6) is cooled by quenching with water (8) in a quencher (D) and the thus obtained cooled offgas (7) is scrubbed with an aqueous alkaline solution (9) to produce cleaned off-gas (10). The wash waters (11) and (12) from the quencher (D) and the scrubber (E) can be further treated (F) to recover sulfur removed from the offgas.
EXAMPLES
Example 1
Nb2O5 concentrate was analyzed chemically and its mineralogy and particle size distribution where determined. The particle size of the oxide concentrate was 88 pm and dgo 207 pm. The oxide concentrate consisted mainly of zoned to homogeneous pyrochlore-columbite and pyrite grains. The concentrate comprised Nb 36.4 % w/w, S 7.61 % w/w, Cl 0.83 % w/w and F 1.8 % w/w. A 150g sample of the oxide concentrate was roasted in a laboratory-scale fluidized bed furnace that comprised a vertical trans temp 2%” x 20” furnace and a fused quartz tube. A porous quartz sinter was used as a grate and aided in distributing the gas flow. Roasting was performed as a batch operation and at température of 750 °C under an air flow. The sulfur and carbon contents of the sample were analyzed periodically.
Sulfur and carbon content of the thus obtained product was 0.13 and 0.06 % w/w, respectively, after two minutes roasting at température of750 °C.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the daims.
Claims (15)
1. A method of pre-treating sulfur-poor métal oxide concentrate, comprising the steps of:
(o) providing sulfur-poor métal oxide concentrate having sulfur content below 10 % w/w, wherein the sulfur-poor métal oxide concentrate comprises niobium oxide;
(a) heating the sulfur-poor métal oxide concentrate at an elevated température and in presence of oxygen and an external fuel source to oxidize sulfur compounds contained in the sulfur-poor concentrate to corresponding oxides and/or to thermally décomposé the said sulfur compounds to obtain a sulfur-depleted métal oxide calcine and a sulfur-containing off-gas;
(b) separating the sulfur-depleted métal oxide calcine from the sulfur-containing off-gas; .
(c) cooling the obtained sulfur-depleted oxide calcine;
(d) cooling the off-gas by quenching; and (e) scrubbing the cooled off-gas to recover sulfur.
2. The method as claimed in claim 1, wherein the sulfur-poor métal oxide concentrate comprises more than 40 % w/w métal oxide, in particuiar from 50 to 90 % w/w métal oxide, more particularly from 60 to 70 % w/w métal oxide.
3. The method as claimed in claim 1 or 2, wherein the sulfur content of the sulfur-poor métal oxide concentrate is from 0.2 to 8 % w/w, more preferably from 1 to 7 % w/w.
4. The method as claimed in any one of daims 1 to 3, wherein step (a) is accomplished in a fluidized bed fumace.
5. The method as claimed in claim 4, wherein the fluidized bed furnace is a bubbling fluidized bed fumace or a circulating fluidized bed fumace.
6. The method as claimed in any one of daims 1 to 5, wherein the sulfur-poor métal oxide concentrate comprises chlorides and/or fluorides.
7. The method as claimed in daim 6, wherein the sulfur-poor métal oxide concentrate comprises 0 to 4 % w/w, preferably from 1 to 2 % w/w, chlorides and/or fluorides.
8. The method as claimed in any one of daims 1 to 7, wherein the sulfur content of the sulfur-depieted métal oxide calcine is below 0.2 % w/w, more preferably below 0.15 % w/w.
9. The method as claimed in any one of ciaims 1 to 8, wherein the elevated température is from 500 to 1000 °C, more preferably from 700 to 900 °C.
10. The method as claimed in any one of ciaims 1 to 9, wherein the process conditions of step (a) are determined by the steps of:
(i) analyzing the nature of the sulfur compound(s) and the nature of the métal oxide(s) of the sulfur-poor métal oxide concentrate; and (ii) selecting the process conditions in such manner that the métal oxide retains it stability while the sulfur compounds are oxidized and/or thermally decomposed.
11. The method as claimed in any one of ciaims 1 to 10, wherein the séparation step (b) is accomplished in a cyclone.
12. The method as claimed in any one of ciaims 1 to 11, wherein the cooling of calcine in step (c) is accomplished by a fluidized bed cooler.
13. The method as claimed in any one of ciaims 1 to 12, wherein an aqueous alkaline solution, such as NaOH (aq) or CaOH2 (aq), is utilized in the scrubbing step (e).
14. The method as claimed in any one of ciaims 1 to 13, wherein the external fuel source is liquid and/or gaseous fuel.
15. The method as claimed in claim 14, wherein the fuel source is selected from the group consisting of methane, propane, butane, natural gas and heavy oil.
Publications (1)
| Publication Number | Publication Date |
|---|---|
| OA17900A true OA17900A (en) | 2018-02-27 |
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