HYDROMETALLURGICAL METHOD FOR SIMULTANEOUSLY EXTRACTING METALS AND GYPSUM FROM THE DUST OF A STEELWORKS ELECTRIC ARC FURNACE

Abstract

A hydrometallurgical method for simultaneously extracting zinc, lead, silver, iron and calcium from electric arc furnace dust (hazardous waste) produced by the steelmaking industry (steelworks), in the form of industrial products: zinc as zinc sulphate or zinc cathodes; lead and silver as a concentrate of lead and silver; iron as reduced elemental iron for return to the electric arc furnace; and, lastly, calcium as gypsum, without solid waste or liquid effluents being generated relates to the chemical nature of the electric arc furnace dust (complex oxides) changes to a sulfide complex, and eliminating the hazards associated with the generation of fugitive heavy-metal salts. In addition, the hydrometallurgical problem of low recovery of zinc and iron is solved. Consequently, hydrometallurgy is made easier and more environmentally friendly, as condensed water is used as a leachate, the condensed water being continuously regenerated by vacuum evaporation systems without generating effluents.

Claims

1. A hydrometallurgical method for extracting metals and gypsum from any type of dust of a steelworks electric arc furnace, wherein it recovers, by simultaneously extracting, zinc, lead, silver, iron and calcium, in the form of industrial products; zinc as zinc sulphate or zinc cathodes; lead and silver as a concentrate of lead and silver; iron as reduced elemental iron for return to the electric arc furnace; and, lastly, calcium as gypsum, the method including the following steps: 1) conditioning the electric arc dust by homogenizing and identifying the chemical composition of the dust in terms of the content of Zn, He, Cl, Pb, Ca, Ag, Cd and Hg, to know the grade of valuable metals present and of the elements of risk for metallurgical control and balance in the method, this action being performed in an encapsulated mixture which produces the homogeneous mixture, constituting the homogeneous electric arc dust stock which is stored in encapsulated hoppers, which will enter the method after the respective chemical analysis has been performed; 2) scrubbing the dust from step 1) with water, where the dust contains halogens and, consequently, alkalis and alkalines, elements which must be removed from the oxide complex because they are detrimental to the following steps of the method, for which the homogenizsed dust is transported from the encapsulated hoppers to the scrubbing tanks, the water comes from the condensed water feed system having an absence of dissolved gases and salts and enters at the temperature of 80° C. with a mass ratio of 3 to 1; the scrubbing tanks maintain a constant suspension by mechanical agitation for 15 minutes in the first part of the scrubbing, producing a liquid loaded with soluble complexes of Cl, Na, K, Mg, Ca, Ba, which is sent to the liquid purification unit of the method by the liquid/pulp decanting system; the pulp enters a second scrubbing time of 10 minutes, with water of the same characteristics of the method so as to force a second dissolution of halogens, alkalis, alkalines, and, similarly, the decanting system sends the liquid to the liquid purification system, and the previously filtered solids pass to the following step; 3) extensive sulphation by adding sulphuric acid to the solids of the scrubbing phase for the purpose of changing the chemical nature of the electric arc furnace dust from complex oxide compounds to a group of simple and complex reaction sulphates; to generate this reaction, one part dust to 0.87 parts pure acid is mixed by weight in a continuous mixing reactor specially designed for this phase, generating a paste, the reaction is exothermic and carried out in a range of 120° C. to 150° C., to which there is added water at 80° C. from the condensed water generation system, in order to replace the water losses due to evaporation in the reaction and maintain the plastic condition of the paste; 4) drying by drying the sulphated mixture of electric arc furnace dust in the same sulphation reactor, which continues to operate under continuous mixing, with the temperature of the reactor increasing to 200° C., the paste proceeds to dry, losing all the water by evaporation, forming dark grey agglomerated crystals; 5) thermolysis or thermal decomposition, where one part of the complex is converted to a soluble part (essentially zinc) and one part is converted to an insoluble part (essentially iron), and after the drying phase, the temperature of the reactor increasing to a working range of 680° C. to 720° C., depending on the concentration of Zn, Fe, Pb, in the paste, and the mechanical mixing is kept constant such that the crystals formed in the drying phase can increase the temperature homogeneously, the reaction time being 2 hours. 6) aqueous leaching, where two new complexes are obtained in this step, one being liquid with a large amount of zinc and the other one being insoluble and essentially made up of hematite, gypsum and lead oxides plus other minor oxides, being carried out at 260 RPM and 70° C. in encapsulated tanks with an evaporation water vapour extraction system and in a solid/liquid ratio of 1 to 3.6, the leaching time being between 1 hour and 1 hour and 30 minutes; 7) zinc recovery, where zinc is obtained in this step according to two preferred forms to be obtained, the first in the form of zinc sulphate by evaporation and crystallisation, and the second in the form of zinc cathodes by electrodeposition; 8) flotation, where in this step hematite is separated from lead oxides and various metal oxides in a very small amount, such as, for example, cadmium, nickel, arsenic oxides; the solid coming from the leaching phase is insoluble under normal conditions, with a majority composition of hematite and with the minority presence of lead oxides, calcium sulphate (gypsum) and a presence of silver; 9) magnetic separation, where in this step the hematite still contains gypsum (CaSO4.2H.sub.2O), where the gypsum must be separated from the hematite due to the need to use reduced hematite (Fe.sup.O) as electric arc furnace feed material, in order to remove the gypsum, for which magnetic separation is used, taking advantage of the wide delta of magnetic susceptibility existing between hematite (35×10.sup.3 SI) and gypsum (−0.11×10.sup.3 SI), at low speeds between 0.7 feet/min and 0.8 feet/min of the magnetic separator and at a magnetic flux density between 19,000 gauss and 21,000 gauss; 10) a gas recovery system, where the method comprises in this step a conventional catalytic system for SO.sub.3/SO.sub.2 recovery, capturing gases in diluted solutions of H.sub.2SO.sub.4 (at 70%) in the presence of catalysts, the capture solution is added to the sulphuric acid stock of the method, the conventional catalytic system having forced air heat sinks and being encapsulated. 11) gas scrubbing system, where the system gases are essentially air, O.sub.2 and CO.sub.2; however, given the ultrafine nature of the dust, a small portion of said dust is entrained by the streams of said dust, forcing the gas and particles to pass through water mist and sprays under countercurrent (1.2 m.sup.3 per m.sup.3 of gas), repeatedly, with several scrubbing columns and coils, with the gas passing through ultrafine filters before leaving the method so as to ensure that there is no loss of solids; 12) recovery of sludge from the collector, where the loss of dust because of its ultrafine nature is prevented in this step, by handling sludge from these particles from all the reactors and flow systems which are encapsulated and capture fugitive particles which, because the various systems are in a closed circuit, finally produce sludge, as well as of water vapour which also entrains a minimum portion of particles, which are captured in the vacuum evaporation system and sent to the sludge collector; this sludge is filtered by two twin pumps with phenolic resin membranes at a pressure of 3.5 bar, the first with a 5-micron membrane and the second with a 2.5-micron membrane; and 13) liquid purification with a water decontamination unit which receives liquid flows containing anions, cations, suspension of ultrafine solid particles from the dust scrubbing method, gas scrubbing method, sludge collector and liquid flows of the flotation phase (concentrate and tailings) and eventually from the cleaning and maintenance method for any reactor, and includes a chemical ion separation system, high-pressure membrane filtration, vacuum evaporation, returning the clean water to the industrial condensed water method, crystallising the contaminants; the solids are integrated (precipitates, sludge and crystals), homogenised and added to the concentrate of lead/silver for the respective marketing thereof.

2. The hydrometallurgical method according to claim 1, wherein step 1) determines the zinc (12% to 35%) and iron (17.26% to 28.26%) grade, in addition to knowing with certainty the content of Cl, Pb, Ca, Ag, Cd and Hg.

3. The hydrometallurgical method according to claim 1, wherein in step 2) a reduction of Cl of more than 95% is obtained, consequently, very high reductions of Na, Mg, Ba are obtained, generally obtaining an average reduction of the 17% by weight of the initial content of dust (depending on the elemental contents in each specific case).

4. The hydrometallurgical method according to claim 1, wherein step 3) lasts for 20 minutes, and vigorous and constant mixing is required, because the paste formed is very viscous, and a complete chemical sulphation reaction and depletion of sulphuric acid must be obtained, so that no free acid solutions are generated in the method.

5. The hydrometallurgical method according to claim 4, wherein step 3) produces no liquids in any form, produces water vapour in a very limited form and very little acid mist, where these vapours and gases go to SO.sub.2/SO.sub.3 recovery systems and re-enter the sulphuric acid stock system of the closed circuit method.

6. The hydrometallurgical method according to claim 4, wherein in step 3), the oxide molecules are broken down, replacing the oxygen in the molecules with the typical compound SO.sub.4.

7. The hydrometallurgical method according to claim 1, wherein step 4) lasts for about 10 minutes and allows for the removal of water to prevent thermal shock in the next step and to ensure the complete reaction of the new sulfide complex.

8. The hydrometallurgical method according to claim 1, Wherein in step 5), the thermolysis reaction (thermal decomposition) of iron sulphate takes place as the main reaction, which produces the formation of hematite, with the corresponding generation of SO2 and O2, according to the reaction: 4FeSO.sub.4=2Fe.sub.2O.sub.3+O.sub.2+4SO.sub.2.

9. The hydrometallurgical method according to claim 8, wherein the reaction is carried out at normal pressure, the generated gases are sent to the gas cleaning and SO.sub.2 capture system, which is added to the sulphuric acid stock of the method, in addition to the thermal decomposition reaction of the iron, where the oxides with lower formation energy in relation to iron are also decomposed, as in the case of Pb, Ag, Si, Mn, P, Sn, Cd, Ni, Bi.

10. The hydrometallurgical method according to claim 8, wherein the hematite formed and all the additional oxides formed are insoluble, while, in contrast, zinc in the form of sulphate has a high solubility, which is sent to an encapsulated hopper and cooled to 70° C.

11. The hydrometallurgical method according to claim 1, wherein in step 6), the leaching water comes from the condensed water system, which is a countercurrent system, such that the solids are solubilised and progressively lose zinc, whereas the solution progressively increases in terms of the content of zinc and, to a lesser extent, in terms of the content of Mn and Ca.

12. The hydrometallurgical method according to claim 11, wherein the water leachate does not contain any type of reactive chemical, which prevents the water leachate from being soluble in the solid essentially made up of hematite, and replaces the water losses due to evaporation.

13. The hydrometallurgical method according to claim 11, wherein the aqueous leaching phase produces the extraction of zinc, producing a solution which, on average, tests 56 g of Zn per litre, with a small amount of other components, where the solids are, for the most part, hematite and other metal oxides such as calcium and lead oxides.

14. The hydrometallurgical method according to claim 13, wherein the solids are very fine and a high-pressure pump filtration system provides an efficient separation of the leached solution, generating two new complexes, one being liquid with a large amount of zinc and the other one essentially made up of hematite, gypsum and lead oxides plus other minor oxides, which are sent to the flotation method, and the liquids are sent to the zinc recovery system (evaporation-crystallisation/electrodeposition), configured to keep the temperature of the liquid flow at 70° C., which is moved by peristaltic impulse.

15. The hydrometallurgical method according to claim 1, wherein, in step 7 (Zn recovery), zinc sulphate is produced, and the liquid containing essentially zinc is previously vacuum-evaporated, this operation being performed in a conventional vacuum evaporator wherein the volume of water is reduced by 96%, sending the water vapour to the condensation system, from where the water is recycled to the various water needs of the method.

16. The hydrometallurgical method according to claim 1, wherein the evaporation method prevents the metal and non-metal ions from leaving the solution, the water vapours do not contain ions, and as the volume of liquid water is reduced, the concentration of zinc increases.

17. The hydrometallurgical method according to claim 15, wherein for producing zinc sulphate, an oversaturated solution of 1,800 g Zn/L is produced, which solution enters the crystallisation method in steps and in countercurrent in the conventional encapsulated reactor with a temperature delta of 40° C.; the first crystals are very pure, and the last crystals that are formed are less pure, which finally produces the crystalliser in a mixture of all these crystals.

18. The hydrometallurgical method according to claim 1, wherein, in step 7 (Zn recovery) zinc cathodes are obtained, for which a subsaturated solution is produced with 60 grams per litre of zinc for the zinc electrodeposition method, by the conventional zinc cathode electrodeposition method from sulphuric solutions.

19. The hydrometallurgical method according to claim 1, wherein the liquids are recycled by vacuum evaporation, and the anode sludge is added to the concentrate of lead-silver.

20. The hydrometallurgical method according to claim 1, wherein in step 8), by using the flotation properties of the lead and silver oxides in the presence of hematite (absence of sulfides), foam flotation operations produce an ore concentrate of commercial-quality lead-silver, and additionally cleans the hematite of heavy metal oxides.

21. The hydrometallurgical method according to claim 1, wherein due to the ultrafine nature of the particles of all the components, flotation is a virtually artisanal operation that takes two hours, a time that favours the entrainment of lead oxides and heavy metal oxides, using as flotation reagents those from the family of sodium sulfide (Na.sub.2S), in the presence of sodium carbonate and sodium silicate, with the use of xanthate and pine oil, with the hematite additionally needing starch as a depressant.

22. The hydrometallurgical method according to claim 1, wherein step 9) uses magnetic separation steps from lower to higher flux density, obtaining pre-concentrates of hematite which are subsequently mixed in order to be sent to the hematite reduction method in their conventional form to produce reduced iron, which is agglomerated due to its fine nature to finally be returned to the electric arc furnace.

23. The hydrometallurgical method according to claim 1, wherein in step 11), the solids are captured as sludge which is, in essence, electric arc furnace dust or calcine from the thermolysis method, this sludge is sent to the sludge collection system, and the liquid from the gas scrubbing method is sent to the liquid purification unit by impulsion by peristaltic pumps.

24. The hydrometallurgical method according to claim 1, wherein in step 12), the obtained solids are added to the concentrate of lead/silver, thereby preventing the generation of waste, an operation that does not affect the quality of the concentrate, and the resulting liquid has an ionic content, and is sent to the liquid purification unit.

25. The hydrometallurgical method according to claim 1, wherein due to the corrosive nature of the liquids, the agitation systems of the tanks and the line pipes have an anticorrosive coating; and the liquid and pulp impulsion systems are carried out by peristaltic pumps.

26. The hydrometallurgical method according to claim 1, wherein the filtered solids have, on average, 8% humidity, are insoluble solids, and are almost entirely made up of complex metal oxides.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0102] FIG. 1 is a block flow diagram illustrating a detailed embodiment of the invented method, because evaporation offers the flexibility of producing an oversaturated solution of zinc, from which zinc sulphate is produced in crystallisation.

[0103] FIG. 2 is a flow diagram which shows a second additional embodiment of the invented method, as evaporation offers the flexibility of obtaining a subsaturated sulfuric solution in the order of 60 grams per litre, which allows for the use of the normal electrodeposition (EW) method from which zinc cathodes are obtained.

DETAILED DESCRIPTION OF THE DRAWINGS

[0104] Steelmaking companies using electric arc furnaces for producing steels generally have a production which is, on average, a million tons of steel (1,000,000 MT) per year.

[0105] As previously mentioned, per ton of steel produced, 11 kg to 17 kg of electric arc furnace dust are generated, with a content of zinc from 12% to 35%.

[0106] Hence, on average, per million MT of steel produced annually, about 12,000 annual tons of electric arc furnace dust are produced.

[0107] In view of the attached figures, and according to the numbering of the steps of the method used, two non-limiting exemplary embodiments of the present disclosure can be seen therein, with the understanding that the description must be considered as an example of the principles of the disclosure and does not intend to limit the broad scope of protection of the hydrometallurgical method for simultaneously extracting metals and gypsum from the dust of a steelworks electric arc furnace.

[0108] Next, a detail for a typical operation of 40 DMT of electric arc furnace dust based on the described methods and FIGS. 1 and 2 will be described, where the operating detail is the following: [0109] 1. The dust is conditioned without adding any type of substance or liquid, and grades are determined for: Zn, Fe, Pb, Ag, Ca and Cl as follows:

TABLE-US-00005 Zn 19.50% Average content of the blend of fresh and landfill dust. Iron 18.30% Average content of the blend of fresh and landfill dust. Lead  1.60% Average content of the blend of fresh and landfill dust. Silver  3.28 Average content of the Oz/MT blend of fresh and landfill dust. Calcium  2.62% Average content of the blend of fresh and landfill dust. Other metals  0.80% Sum of the content in ppm (PPm) Cr, Sn, P, Ba, Cd, Sb, Sr, Ni, etc. Chlorine  4.50% Average content of the blend of fresh and landfill dust. [0110] 2. 40 MT of a blend of dust are scrubbed in a reactor with 30.23 m.sup.3 of condensed water from the evaporation method at 80° C., which method is carried out at 0.97 atmospheres. 11.70% of the weight of the dust is removed by removing Cl, Na, K, Mg, Ca, Ba, etc., and the solution is sent to DETOX to recover the salts. [0111] 3. The solid part from the scrubbing step enters the extensive sulphation phase, and 35.32 MT of a blend of dust are treated, raising the grade thereof 23.45% due to the weight reduction. 22.96 MT of H.sub.2SO.sub.4 are added until the reaction ends and the reagent is completely consumed (complete stoichiometry), producing an exothermic reaction at 130° C., and 11.48 m.sup.3 of condensed water from the evaporation method is added at 80° C. to replace the water that evaporates and to prevent thermal shock. [0112] 4. In the same reactor, the temperature is increased to 200° C., producing the drying of 47.95 MT of dust paste, a weight that is increased due to the addition of S (SO.sub.4), changing the chemical nature of the dust. [0113] 5. After the drying phase or step, 48.55 MT of dust is obtained due to the change in nature of iron from Fe.sub.2O.sub.3 to FeSO.sub.4, and it is subjected to thermolysis, with the temperature of the reactor increasing to 700° C., depending on the concentration of Zn, Fe, Pb, in the paste. The mechanical mixing is kept constant such that the crystals formed in the drying phase can increase the temperature homogeneously, the reaction time being from 1.8 hours to 2.10 hours. [0114] 6. The solids (dust) obtained from the thermolysis step are subjected to aqueous leaching in encapsulated tanks with 131 m.sup.3 of condensed water coming from the evaporation method at 80° C., in a solid/liquid volumetric ratio of 1 to 3.6, without adding any type of reactive chemical, producing an efficient extraction of zinc, obtaining a solution containing on average 56 g of zinc per litre and an amount of solids, mostly hematite and calcium and lead metal oxides. At this point, there are two new complexes, one being liquid with a large amount of Zn and the other one made up of hematite, gypsum, and essentially lead oxides. The solids are very fine, so they are filtered by means of high-pressure pumps, obtaining 28.65 MT of solid cake, which are sent to the flotation method, and the liquids are sent to the method for recovering zinc (evaporation-crystallisation/electrodeposition). The leaching is performed for a time of 1 hour to 1 hour and 30 minutes, and the flow temperature must be kept at 70° C., said flow being moved by peristaltic impulse at 260 RPM. [0115] 7. From the liquid zinc complex obtained in the leaching step, depending on the form of zinc to be obtained as a final product, said zinc is recovered in two forms: a first form as zinc sulphate and a second form as zinc cathodes. In the first desired form, shown in FIG. 1, the liquid containing essentially zinc is previously vacuum-evaporated, this operation being performed in a conventional vacuum evaporator, wherein the volume of water is reduced by 96%, in the present case 126.89 m.sup.3 of water being evaporated, sending the water vapour to the condensation system, from where the water is recycled to the various water needs of the method. [0116] The evaporation method prevents the metal and non-metal ions from leaving the solution, and the water vapours do not contain ions. As the volume of liquid water is reduced, the concentration of zinc increases. [0117] To obtain zinc sulphate, which gives the highest added value, 4.11 m.sup.3 of oversaturated solution of Zn containing 1,800 g Zn/L is produced, which solution enters the crystallisation method in steps and in countercurrent in a conventional encapsulated reactor with a temperature delta of 40° C., obtaining 33.52 MT of ZnSO.sub.4.7H.sub.2O with an average % of commercial grade Zn of 22.62%, producing an increase in weight due to the hydration water. [0118] The first crystals are very pure, and the last crystals are less pure. This finally produces the crystalliser in a mixture of all these crystals, yielding a typical composition shown in Table 4. [0119] In a second desired form for Zn recovery in the form of cathodes, shown in FIG. 2, a subsaturated solution is produced containing 60 grams per litre of zinc for the zinc electrodeposition method, by means of the conventional method widely known in the metallurgical industry (zinc cathode electrodeposition method from sulphuric solutions), obtaining 7.55 MT of zinc cathodes with a purity of 98%. In this case, the liquids are recycled by vacuum evaporation, and the anode sludge is added to the concentrate of lead-silver. [0120] 8. The 28.65 MT of cake (dust solids) from the leaching step, which are insoluble under normal conditions, are subjected to a flotation method for a period of two hours for the purpose of separating the hematite that is present mostly from lead oxides, calcium sulphate (gypsum) and silver. [0121] Due to the ultrafine nature of the particles of all the components, the flotation reagents used are those from the family of sodium sulfide (Na.sub.2S), in the presence of sodium carbonate and sodium silicate, with the use of xanthate and pine oil. Additionally, the hematite needs starch as a depressant, which produce an excellent separation of an ore concentrate of commercial-quality lead-silver the typical composition of which is reported in Table 2. In the present example, 1.07 MT of concentrate of lead-silver is obtained, with a content of additional heavy metals, and 27.58 MT of tailings containing Fe.sub.2O.sub.3, CaSO.sub.4, SiO.sub.2 and other minority components. [0122] 9. The 27.58 MT of tailings from the flotation step enter three in-line magnetic separators with a magnetic flux density between 19,000 gauss and 21,000 gauss, for the purpose of separating the gypsum from the hematite. This operation is performed at low speeds between 0.7 feet/min and 0.8 feet/min to prevent the entrainment of gypsum fines, and from a lower to higher flux density. This step obtains 20.92 MT of concentrate of hematite and 8.37 MT of gypsum (CaSO.sub.4.2H.sub.2O), producing an increase in weight due to the hydration water (2H.sub.2O). [0123] 10. The gases which are produced in the different steps of the method are recovered in order to prevent them from being released into the environment through an encapsulated conventional catalytic system with forced air heat sinks for SO.sub.3/SO.sub.2 recovery, capturing the gases and acid mist solutions in diluted solutions of H.sub.2SO.sub.4 (al 70%) in the presence of catalysts, and the capture solution is added to the sulphuric acid stock of the method. In an exemplary embodiment, 8.40 MT of SO.sub.2 are recovered and recycled. [0124] 11. The gases and streams of air generated in the various areas of the method are sent to a liquid purification system for the purpose of making the method efficient and recovering a small portion of dust which is entrained by said gases. The cleaning system used is a countercurrent system, forcing the gas and particles to pass through water mist and sprays under countercurrent (1.2 m.sup.3 per m.sup.3 of gas), repeatedly, with several scrubbing columns and coils, The gas passes through ultrafine filters before leaving the method so as to ensure that there is no loss of solids. In the present exemplary embodiment, 2 MT of method gases (O.sub.2 plus particles) are cleaned by means of commercial reactors, and the solids are captured as sludge which is, in essence, electric arc furnace dust or calcine from the thermolysis method, this sludge being sent to the sludge collection system, and the liquid from the gas scrubbing method is sent to the liquid purification unit (DETOX) by impulsion by peristaltic pumps. [0125] 12. The sludge generated in the various areas of the method is recovered in a sludge collector for the purpose of preventing the loss of dust due to its ultrafine nature. In the present exemplary embodiment, 120 Kg of sludge from the entire method are filtered at 3.5 bar in two twin pumps, the first with a 5-micron membrane and the second with 2.5-micron membrane. The solids obtained are added to the concentrate of lead/silver, and the resulting liquid having an ionic contained is sent to the solution purification system. [0126] 13. The liquid flows containing anions, cations, suspension of ultrafine solid particles from the dust scrubbing method, gas scrubbing method, sludge collector and the liquid flows from the flotation phase (concentrate and tailings) and eventually from the cleaning and maintenance method for any reactor are sent to a liquid purification unit for the purpose of being subjected to a water decontamination method which uses technology available on the market, consisting of a chemical ion separation system, high-pressure membrane filtration, vacuum evaporation, returning the clean water to the industrial condensed water method, crystallising the contaminants, and the solids are integrated (precipitates, sludge and crystals), homogenised and added in a suitable manner to the concentrate of lead-silver for the respective marketing thereof.

[0127] In the exemplary embodiment, 200 m3/day of liquids are purified.

[0128] Table 5 shows the specification and balance of products of the method for a typical application of 40 TMD of electric arc dust.

TABLE-US-00006 TABLE 5 General balance of the method 40 MT dust produce: CaSO4•2H2O ZnSO4•7H2O Calcium CC Pb Ag Zinc sulphate Fe° sulphate Concentrate of lead- heptahydrate Reduced iron dihydrate silver MT MT MT MT 33.52 7.31 8.37 1.07 Zn 22.61% Fe 93.417% CaSO4 52.26% Pb 52.06% S 11.01% C 3.921% SiO2 18.31% Ag 81.33 Oz/ MT ZnSO4 55.47% Si 1.266% Fe2O3 7.28% Zn 4.88% Cl 0.71% Mn 0.669% ZnO 2.21% Cu 0.59% Fe 71 ppm P 0.049% PbO 1.05% S 3.52% Hg Tr ppm S 0.056% H Me 0.17% in- 5.11% soluble Pb Tr ppm SiO 21.95% H Me 2 ppm Ca 0.68% Mn 0.51% Bi 0.12% Sb 0.26% As 0.08% Mg 0.17% Al 0.41% P 0.19% Cd 117 ppm Ba 437 ppm Sn 370 ppm