Title:
Integration processes of the treatments of zinc silicate concentrates or zinc silicate ore and roasted concentrates of zinc sulphides
Kind Code:
A1


Abstract:
The invention refers to the many ways of integrating and joining the processes for treating ore and silicate concentrates of zinc with the product of the sulphide roaster in the zinc industry. These processes include: (i) Use of concentrated raw or ore zinc silicates, from several mineral sources, which are leached with the calcine from the zinc sulphide roaster in Neutral leaching. (ii) Use of concentrated raw or ore zinc silicates, from several mineral sources, interlinked with the treatment of the zinc sulphide roaster calcine, in Acid leaching of Ferrites and Iron Precipitation (iii) Use of concentrated raw or ore zinc silicates, from several mineral sources, interlinked with the treatment of the zinc sulphide roaster calcine in Neutral leaching, after silicate leaching. (iv) Use of calcine (600-900° C.) of silicate concentrates or silicate ores with selective precipitation of zinc in the Magnesium Treatment, and integration with the calcine from zinc sulphide roasters either in Neutral leaching, Acid leaching of ferrites of Iron Precipitation (v to viii) Processes I to IV, as above, adding the step to remove halogens such as fluorides and chlorides.



Inventors:
De Souza, Adelson Dias (Tres Marias - MG, BR)
Application Number:
10/497133
Publication Date:
03/31/2005
Filing Date:
11/07/2002
Assignee:
DE SOUZA ADELSON DIAS
Primary Class:
International Classes:
C22B1/02; C22B3/08; C22B3/20; C22B3/44; C22B19/00; (IPC1-7): C22B19/00
View Patent Images:



Primary Examiner:
FIORITO, JAMES A
Attorney, Agent or Firm:
WOOD, HERRON & EVANS, LLP (CINCINNATI, OH, US)
Claims:
1. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides characterized by the use of raw concentrates or zinc silicate ores from several mineral sources, which are leaching solutions together with the roaster calcine of zinc sulphide in the Neutral leaching stage, as shown in the blocks flowchart of FIG. I.

2. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by being able to repulp the zinc silicate concentrates with washing using water from the leaching residue, residual water or industrial water in the repulping stage.

3. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 and 2 characterized by the fact that solids concentration is held at between 40 and around 60% of mass.

4. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that the spent solution from zinc electrolysis is added to the zinc concentrate silicate/ore to maintain pH between 4.0 and 4.5.

5. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that direct or indirect steam is injected into the tanks to maintain a temperature in thee range of 75 and 85° C.

6. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that when the zinc concentrates are lower than 10.0 g/l, solid/liquid can take place where the liquid is sent to the zinc recuperation and the solid to the pre-leaching of the silicate ore or concentrate.

7. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that the pH in the pre-leaching of the ore/silicate concentrate (4) is held at approximately 3.0 to 3.5, by adding the spent solution created by zinc electrolysis.

8. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that the time of residence in pre-leaching of the ore/silicate concentrate, can vary approximately between 3 and 6 hours, varying as a function of the physical and chemical characteristics of the types of silicate being treated.

9. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that in the neutral leaching (5) there is integration of the process of the two silicate ores and the duly calcinated zinc sulphide.

10. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that in neutral leaching (5) the PH can vary between approximately 3.2 and 3.8; the temperature between around 70 and 75° C. and the time of residence between 4 and 5 hours approximately.

11. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 1 characterized by the fact that there is an option to remove halogens such as fluorides and chlorides, according to the blocks flowchart of FIG. V, based on precipitation with lime.

12. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides characterized by the use of raw concentrates or zinc silicate ores from several mineral sources, interlinked with the treatment of the calcine from roaster of zinc sulphides, in Acid leaching of the ferrites or calcine (7) and Iron Precipitation (11), in accordance with the blocks flowchart presented in FIG. II.

13. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 12 characterized by the fact that the quantity of silicate ore or concentrate in each stage can vary from zero to 100%.

14. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 12 characterized by the fact that the operating conditions for neutral leaching are the same as those described in the process item in integration I.

15. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 12 characterized by the fact that there is optional removal of halogens, such as fluorides and chlorides, according to the blocks flow chart of FIG. VI, based on precipitation using lime.

16. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides characterized by the use of zinc silicate ore or raw concentrates, from several mineral sources, interlinked with the treatment with the calcine from roasting zinc sulphides in the Neutral leaching (5), after leaching of the silicates, in accordance with the blocks flowchart of FIG. III.

17. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 characterized by the fact that the solution called the attack solution is a mixture of concentrated Sulfuric acid mixed or not with a spent solution from electrolysis.

18. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 and 17 characterized by the fact that the acid concentration in the attack solution may vary between 150 to 250 g/l where the variation is a function of the sulphide balance in the process.

19. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 and 17 characterized by the fact that the time of residence is preferably between 5 to 8 hours and depends basically on the efficiency of the agitation tanks, granulometry of the ore/concentrate, temperature and of the levels of ores contained in the zinc silicate sources.

20. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 characterized by the fact that integration of the two plants arises from the liquid obtained in the solid/liquid separation, which is sent o neutral leaching (5).

21. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 characterized by the fact that the operating conditions of neutral leaching are the same as those described in integration process I.

22. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 characterized by the fact that the solid residue obtained is sent to filtration (15) where washing of the residue is carried out to recover the soluble zinc.

23. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 characterized by the fact that washing is carried out in two stages, repulping and dislocation of the soluble zinc in the discarded mud being less than approximately 0.5%.

24. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 16 characterized by the fact that there is an option to remove halogens, such as fluorides and chlorides, according to the blocks flowchart of FIG. VII, based on precipitation using lime.

25. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides characterized by use of zinc silicate raw or ore concentrates from seeral mineral sources, interlinked with the treatment with the zinc sulphide roaster calcine, in accordance with blocks flowchart of FIG. IV.

26. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides characterized by use calcine (obtained at 600-900° C.) of silicate concentrates or ore silicates, with selective precipitation of zinc in the magnesium treatment, and integration of the roaster product of zinc sulphide either in the Neutral leaching, Acid leaching of ferrites of Precipitation of Iron, or in accordance with the blocks flowchart of FIG. IV.

27. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 26 characterized by the fact that there is an option to remove halogens, such as fluorides and chlorides, according to the blocks flowchart of FIG. VII, based on precipitation using lime.

28. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides characterized by the fact that that process integration can be: Added directly to the silicate calcine in neutral leaching (5), or; Adding the silicate calcine in Acid leaching (7), or; Adding the silicate calcine during precipitation of Iron/Paragoethite (11), or; Adding the silicate calcine in two or three simultaneous stages; For al of the above options, the silicate calcinate may or may not go through the Magnesium treatment beforehand, together with secondary filtration from the washing of the filtration bricks or other water from plant washing. This depends on the magnesium balance in the plant. In FIG. IV, magnesium treatment was considered in all options.

29. Integration processes of the treatments of concentrates or zinc silicates ore and roasted concentrates of zinc sulphides in accordance with request 28 characterized by the fact that there is an option to remove halogens, such as fluorides and chlorides, according to the blocks flowchart of FIG. VII, based on precipitation using lime.

Description:

This invention aims to supply several processes of integration and unification in the treatment of zinc silicate ores and concentrates with the calcine obtained from the sulphides roasting, defined by joint or interconnected leaching of these several sources of zinc, their filtrations and joint purification of the solutions of the obtained zinc sulphate.

The well-known hydrometallurgic processes of obtainment of zinc in solution consist in the treatment of Sulphide Roaster calcine by neutral leaching through several Teachings stages of the ferrites and consequent removal of iron, either by precipitation as jarosite, paragoethite, goethite, haematite or iron slag. The patents GB 2 114 966 A “Recovery of zinc from sulphidic material”, U.S. Pat. No. 5,120,353 “Hidrometallurgic method for processing raw materials containing zinc sulphide”, U.S. Pat. No. 5,585,079 “Method for leaching material containing zinc oxide and zinc silicate” and the Brazilian Patent PI 9407223-0 A “Processes for extraction of Zinc from Concentrates of Zinc Sulphide, and for the leaching of zinc ferrite, jointly with a sulphided material containing zinc sulphide”, refer to these processes.

The results are options of simplified processes with elevated performances of recovery of zinc, mainly from the silicate concentrates and ores (increase from 88% to 97% in zinc solution, in the treatment of the silicates).

The use of only one acid leaching for the zinc ferrites has also been achieved through the integrated process with the silicate ores and concentrates, allowing for the obtainment of up to 99.3% of a zinc solution in relation to this Zinc source.

The extraction of magnesium, a chemical element, with high levels in ores and zinc silicate concentrates, is obtained using the magnesium treatment system described in all integration operations. The invention also includes processes for purging undesirable elements during zinc production, such as fluorides and chlorides.

The Petitioner has developed integration and unification processes of the treatments of concentrates or zinc silicate ore and roasted concentrates of zinc sulphides caracterized by joint leaching from the many sources of zinc, its filtrations and the unique purification obtained. The integration can be obtained in eight distinct processes, as follows:

    • (i) The Integration process is characterized by the use of raw or zinc silicate ore concentrates supplied by several ore sources which are leached jointly with the calcine from the zinc sulphide roaster, in the Neutral Leaching process, as shown in the flowchart of FIG. 1 attached;
    • (ii) Integration process characterized by the use of raw concentrates or zinc silicate ores, interlinked with treatment of the zinc sulphide roaster calcine, in the Acid Ferrite Leaching or calcine (7) and Iron Precipitation (11) process, in accordance with the flowchart of FIG. II attached;
    • (iii) Integration process, characterized by use of raw concentrates or zinc silicate ores from several mineral sources, interlinked using treatment with the zinc sulphide roasted calcine in the Neutral Leaching stage (5), after silicate leaching in accordance with the flowchart in FIG. III attached;
    • (iv) Integration process, characterized by the use of calcines of silicate concentrates or silicate ores (obtained at 600-900° C.), with selective zinc precipitation in the Magnesium treatment, and integration with the product of the Zinc Sulphide Roaster in the Neutral Leaching, Ferrite Acid Leaching or iron Precipitation stages, in accordance with the flowchart in FIG. IV attached;
    • (v) Integration process, characterized by the use of raw concentrates or zinc silicate ores from several mineral sources, which are leached together with the calcine from the zinc sulphide roaster, during the Neutral Leaching stage including the removal of halogens such as: fluorides and chlorides, in accordance with the flowchart in FIG. V attached;
    • (vi) Integration process, characterized by the use of raw concentrates or zinc silicate ores from several mineral sources, interlinked with the treatment with the calcine from the zinc sulphide roaster, in the Acid Leaching and Iron Precipitation stage including the stages of halogen removal, such as fluorides and chlorides, in accordance with the flowchart in FIG. VI attached;
    • (vii) Integration process, characterized by the use of concentrates raw concentrates or zinc silicate ores from several mineral sources, interlinked with the treatment with the calcine from the zinc sulphide roaster in the Neutral Leaching stage after silicate leaching, including the stages of halogen removal, such as fluorides and chlorides, in accordance with the flowchart in FIG. VII attached;
    • (viii) Integration process, characterized by the use of calcine (obtained at 600-900° C.) of silicate concentrates or silicate ores with selective precipitation of zinc in the Magnesium treatment and integration with the product of the Zinc Sulphide Roaster either in the Neutral Leaching, Acid Leaching of ferrites or Iron Precipitation stages, including the stages of halogen removal, such as fluorides and chlorides, in accordance with the flowchart in FIG. VIII attached;
      Integration process I—shown in the blocks flowchart of FIG. I, attached.

Integration Process I—shown in the blocks flowchart of FIG. 1.

FIG. I shows the option of integration of the treatment processes of sulphide concentrate and silicate (or ore) zinc concentrate, where the integration or linking of the processes occurs in the Neutral Leaching stage (5). After the magnesium treatment of the concentrate or silicate ore (2), to extract the magnesium present in the concentrate and in the spent solution from the electrolysis (13), the silicate cake is pre-leached (4). In the pre-leaching stage(4), the carbonates present in the concentrate are dissolved and the acid pulp is driven to the Neutral Leaching (5) of the calcine (arising from the Roasting of the sulphide concentrate), where it is integrated into the joint zinc extraction process of the two sources of Zinc. The operational conditions, for each stage of this process are described hereinbelow:

Repulping Stage (1)—This stage consists of the repulping of the zinc silicate concentrate with washing waters of the leaching residues, residual waters of the plant or simply industrial water. The operation parameter in this phase of the process is the concentration of the solids, to be kept from 45% to 60%. The repulping tank is to be coated with an anti-acid material, to resist the chemical effect, when liquids of high degree of acidity are used.

Stage of Magnesium Treatment (2)—Its purpose is to eliminate part of the magnesium contained in the source of silicates zinc and in the spent solution from the electrolysis. It is suited to control the balance of the plant waters.

The spent solution arising from the stage of the zinc electrolysis is added to the ore pulp/zinc silicated concentrate, so as to maintain the pH ranging from 4.0 to 4.5. Direct or indirect steam is injected in the tanks to maintain a temperature ranging from 75 to 85° C. Upon such conditions, part of the magnesium and of the zinc contained in the silicate ore is added to the solution. Next, in a series of cascade tanks, it is executed the selective precipitation of the zinc in relation to the magnesium, by adjusting the pH parameters, temperature and residence time. When the zinc concentrations are lesser than 10.0 g/l, it is performed the separation solid/liquid, where the liquid is sent to the stage of recuperation of zinc and the solid part to the ore's or silicates concentrate's pre-leaching stage.

The water balance in the plant is done by virtue of a greater or lesser amount of solution spent in this stage. When the balance of water in the plant is unfavorable (increase of the general volume) it is increased the amount of spent solution introduced in this stage and vice-versa, and the favorable balance of water decreases the quantity of spent solution.

Pre-leaching stage of ore/silicate concentrate(4)—This stage consists of the pre-leaching of the pulp with a view to promote the dissociation of the carbonates contained in the silicate ore/concentrate, according to reaction:
MeCO3+H2SO4 - - - MeSO4+CO2+H2O, where Me=Ca, Mg, Zn, etc.

The pH, in this stage, is kept within the range from 3.0 to 3.5, through the addition of spent solution arising from the zinc electrolysis. The residence time ranges from 3 to 6 hours and varies according to the physical & chemical characteristics of the silicate that is being treated.

Stage of neutral leaching (5)—It is in this stage that the integration of the process occurs. The two ores (the silicated ore and the zinc sulphide already duly calcined) are leached together. The leaching is to be performed so as to be obtained the zinc's maximum extraction and the silica coagulation, so that the obtained pulp may be decanted, filtered or centrifuged. Of the several studied parameters it was verified that the most important to obtain a maximum extraction of zinc and coagulation of the silica were:

    • pH—3.2 to 3.8.
    • Temperature—70 to 75° C.
    • Residence Time: from 4 to 5 hours.

The zinc extraction efficiency in this stage is 80%.

The concentration of soluble silica in the industrial tests was around 60 to 80 mg/l in the zinc sulphate solution, which is sent for purification. This concentration of silica didn't harm or decrease the efficiency of the processes of solid/liquid separation of the pulp.

Yet in this stage it is made the purification of the elements deemed dangerous to the stage of the electrolysis of the zinc. This purification is made through the precipitation of the iron contained in the solution, in the form of ferric hydroxide. Chemical elements as As, Ge, Sb, Se and Te are purified in this stage. The iron in the first tank has to be kept ranging from 0.5 to 3.0 g/l and this variation is in accordance with the concentration of these elements deemed dangerous in the ores/concentrates which are being processed. The adjustment of the concentration of iron in the first tank is made by using the liquid from the acid leaching stage. Anode mud containing manganese dioxide is also added in this tank for the oxidation of the Fe++ to Fe+++.

The pulp obtained in the last tank of Neutral Leaching (7) is thickened, so that an overflow be obtained, such overflow constituted of a zinc sulphate with traces of cadmium, copper, cobalt, nickel, arsenic, germanium, antimony, which goes to the stages of Purification, Electrolysis and Casting. These last phases of the process are not the subject of the Patent.

The underflow goes to the Acid Leaching unit (7), for leaching of the zinc ferrites from the Roaster's calcine, whose later phases are not the subjects of this Patent, as well.

Integration Process II—shown in the blocks flowchart of FIG. II.

FIG. II exhibits another option of connection of the processes of treatment of the zinc sources. In this case, the interlinking occurs in the stages of Acid Leaching of the calcine (7) and/or precipitation of iron (11), instead of the stage of Neutral Leaching of the previous option.

The amount of concentrate or silicated ore in each stage may range from zero to one hundred percent. The option to use the integration process I or II depends on:

    • whether the plant is already in operation: the availability of equipments in each stage; complexity of lay-out change; physical space for the adaptation; cost/benefit.
    • If a new plant: it depends more on the cost/benefit.

Integration Process III—shown in the blocks flowchart of FIG. III.

FIG. III presents the integrated process for the obtainment of zinc, where the silicate concentrate or ore is fully leached (4) and the obtained pulp is sent to the Neutral Leaching of the Calcine of sulphide zinc concentrate (5).

In this process it is introduced a step denominated silicate leaching followed by a solid/liquid separation. The silicate acid leaching (4) is made with a solution denominated leaching solution, which is a mixture of Concentrated Sulfuric Acid with spent solution from the electrolysis. The concentration of acid in the leaching solution may range from 150 to 250 g/l and such variation is due to the balance of sulphate in the process. The residence time ranges from 5 to 8 hours and basically depends on the efficiency of agitation in the tanks, granulometry of the ore/concentrate, temperature and the grade of the minerals contained in the source of silicate zinc. The purpose of this stage is to extract the maximum possible of the zinc contained in the silicate source and the parameter to evaluate the efficiency of this stage is the content of zinc soluble in acid (zinc content not leached) discarded in the subsequent stage, which is the separation solid/liquid. The value deemed optimal is ZnH+≦0.5%. The process of integration of the two plants is made through the liquid obtained in the stage of separation solid/liquid (14), which is sent to the neutral leaching (5). The conditions of the neutral leaching operations are the same ones already described in the item “Integration Process I”. The obtained solid residue is sent to the filtration (15) where the residue washing is accomplished to recover the soluble zinc.

The washing is performed in two stages, re-pulping and displacement and the soluble zinc content contained in the discarded residue is lesser than 0.5%.

Integration Process IV—shown in the blocks flowchart of FIG. IV.

FIG. IV shows the integration process which has also been industrially tested and contemplates the calcination of the silicate concentrate, aiming at the decomposition of the organic substances and the carbonates contained in the concentrate. The calcination may be acomplished, by using horizontal or vertical batch or continuous kiln, by using BPF oil of any type, gasogene, natural gas, coal fines, etc. The use of the previously calcinated silicate concentrate eliminates the silicate's pre-leaching step, whose purpose was precisely to promote the decomposition of the carbonates through the chemical process.

The integration of the process can be made:

    • By directly adding the silicate calcinate in the stage of neutral leaching(5), or
    • By adding the silicate calcinate in the acid leaching stage(7), or
    • By adding the silicate calcine in the Precipitation of Iron/Paragoetite phase (11), or
    • By simultaneously adding the silicate calcine in the two or three phases.
    • For all the options above, the silicate calcine may or may not be submitted to the magnesium treatment, jointly with the secondary filtrate from the residue washing or other plant's washing waters. This depends on the plant's magnesium balance. FIG. IV shows the magnesium treatment in all its options.

The operational conditions of the stages where the silicate ore/concentrate is added are the same ones already described in the integration processes I, II, III. The option of using the calcined silicate ore/concentrate is taken in accordance with the cost/benefit studies.

Process for integration and removal of halogens, such as fluorides and chlorides are shown in FIGS. V to VIII, attached. They include implementing additional neutralization steps in general before filtration of the pulp leached of silicates. The basis for removing fluoride is based on precipitation with lime, to form a stable compound of calcium fluoride (CaF2), with a pH of around 4.0 to 4.7. In this case, the pH control must be strict to not pass 5.0 avoiding zinc precipitation and loss of plant yields.

The processes, according to this invention, are illustrated by the non-limitative examples of practical realization hereinafter, and the following data were extracted from pilot tests and/or realizations of industrial scales:

EXAMPLE 1

Integration Process III:

INCREASE OF THE RECOVERY OF THE PLANT WITH THE INTEGRATION BY PROCESS III

The concentrates were treated according to the flowchart of FIG. III.

Treated amounts:

    • Sulphide concentrates=10212.332 t
    • Silicated concentrates=13291.000 t

Leaching efficiency of the silicate concentrate=94.30%

Content of Zn soluble in acid=1.79%

Clear height in the thickening of the leached silicates concentrate=1.4 m

Consumption of zinc powder in relation to the produced cathode=2.94%

Production of cathodes=9641.430 t

Problems occurred with this process:

    • Since the silicate concentrate is obtained by flotation, during the period in which this process was used, an expressive foam during the leaching occurred and the tanks overflew. The way to minimize such overflows was to accomplish a weak leaching, with a greater number of reactors and using floor pump to return the overflow to the origin tanks. Another solution to the problem is the Integrated Process IV.

The current efficiency (Faraday) is decreased when the total content of organic matter exceeds 3 mg/l. This parameter was controlled in the concentration Plant of the minerals of silicates, with more precise controls in the consumption of flotation or implementing the Integrated Process IV (FIG. IV).

Integrated Process IV:

INCREASE IN THE LEACHING EFFICIENCY OF THE CALCINED CONCENTRATES OF ZINC SILICATES AND INCREASE OF LEACHING EFFICIENCY OF THE CALCINE FROM SULPHIDE CONCENTRATES, WITH THE INTRODUCTION OF THE CALCINED SILICATE CONCENTRATE, AT THE END OF THE HOT ACID LEACHING.

Process IV, (attached FIG. IV), was tested at bench, pilot & industrial plant. The obtained results are shown as follows:

RESULTS OF TESTS OBTAINED IN A PILOT PLANT(examples 2 to 8):

EXEMPLE 2

Calcination of Zinc Silicate Concentrate

FIG. IX attached presents the comparative results of the calcination of the concentrate at 900° C. versus raw concentrate as to the parameters loss of ignition, zinc content, carbonate content and foam formation. FIG. IX shows that it was possible to completely eliminate the foam with the increase of the Zn content in the concentrate, from 40% to 44% (in the calcined concentrate) and mass reduction (loss of ignition) of 20%, referring to the elimination of the carbonates (<0.2%) and moisture, either in bench or at industrial tests.

EXAMPLE 3

Effect of Calcination in the Current Process of Magnesium Treatment (MT)

FIG. X shows the results of tests of zinc selective precipitation with silicate calcined concentrate on a zinc solution with the silicates calcined concentrate on a solution of 17 g/l of zinc and 2.1-2.4 g/l of Mg (magnesium). The results demonstrate that, at temperatures of 90-95° C. and residence time of five hours, the zinc precipitates to 2.7-4.3 g/l, which represents an efficiency of about 80% for zinc precipitation (17-{fraction (4/17)}×100), and the magnesium concentration increased from 2.4 to 4.0 g/l, demonstrating an expressive capacity of magnesium purge.

EXAMPLE 4

Effect of Calcination on the Silicates Leaching

FIG. XI shows that the calcination of the silicates concentrate drastically reduced the residence time, during the leaching, due to the reduction in the formation of foam, from 4 to 1 hour and 30 minutes. This rendered it possible to reduce the necessary volume to perform the leaching of the sources of zinc.

EXAMPLE 5

Effect of Calcination on the Purification of the Solution of Zinc Sulphate

FIG. XII attached presents the results of the effect of calcination on the purification of the solutions of zinc sulphate, where there is a reduction of more than 1% in the consumption of zinc dust in relation to the cathode produced when the solution was obtained through the calcined concentrate, from 4.12to 2.95%.

EXAMPLE 6

Leaching and Filtration Efficiency of the Calcined Ore of Zinc Sulphide

FIG. XIII attached presents the leaching and filtration efficiency of the calcined ore of zinc sulphide where it increased from 96% to 99%, according to the results obtained with the feeding of the calcined ore/concentrate of silicates, at the end of the acid leaching or beginning of the neutralization of the iron precipitation. The tests were made on benches, in volumes of 50 liters, according to the operational conditions shown in FIG. XIII.

EXEMPLE 7

Effects of Neutralization on the Reduction of the Fluoride Levels in Zinc Sulphide

The results of the bench test for reducing the fluoride levels from concentrated silicate leaching, can be found in FIG. XIV, attached.

RESULTS OBTAINED IN TESTS OF INDUSTRIAL SCALE (examples 8 to 10)

Calcination of the Silicates concentrates in Rotary Kiln

Temperatures=600-900° C.

Residual content of carbonates=2% or Total Carbon=0.3% maximum

FIG. XV attached presents the results of integration industrial tests where it confirms the performance of zinc selective precipitation, already shown in FIG. X. This figure shows that the zinc content, in the liquid part of the solution was, generally, in an average of 5 g/l when it was used a washing solution with Zn=17-25 g/l and silicate concentrate for the selective precipitation of zinc.

EXEMPLE 9

FIG. XVI attache, presents the results of industrial tests, when it was used the calcined silicate concentrate and the integration process of FIG. IV. The obtained leaching & filtration average efficiency ranged from 95 to 99%, being the main impediments to keep the elevated efficiency were the low efficiency of the press-filters used for the extraction of water-soluble zinc.

EXAMPLE 10

Reduction of the Fluoride Levels in Zinc Sulphide Solutions from Silicate Concentrates

FIG. XVII attached, presents the results of industrial tests to remove fluorides from solutions obtained from leaching de silicate concentrates.

It was found that the level fell from 27 to 17 mg/l, allowing for automatic removal in electrolysis rooms.