AU2009251075B2 - A method for arsenic removal and phosphorous removal out of iron ore - Google Patents

Abstract

is Abstract A method for arsenic removal and phosphorous removal out of iron ore, the method comprising ore crushing and milling, a preliminarily roasting; leaching arsenic and phosphorous with an inorganic reagent solution; and separating a liquid phase from the solid phase, wherein the crushed and milled iron ore is mixed additionally with a carbon reductant and a carbonate sludge; said mixture is roasted preliminarily in an oxygen-containing environment; and the resulting product is cooled with water or an aqueous solution of alkali and is subjected to a magnetic concentration in the presence of an aqueous solution of an inorganic reagent. 1/] Ore Soda Lime Waiter CausticI zaion CN Mix I ng setng Peal Slud e R sting ( 9 washino Washed Leaching and magnetic concentration Tailings Concentrate (20%) (80%) Na) 1i solution 121i I~l~ D i tI3) %iUH n with As, P and V Service water Ta i lings Concentrate ] ti of As P& V washing washing * -S -i compounds out of concentrate Seaw-ater "o [Sfsltion Tailing S Concentrate to As. P V Alkaline solution to dump bloomery process salt concentrate Fig.1

Description

Rcguliion 3.2 AUSTRALIA PATENTS ACT, 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: CLOSED JOINT STOCK COMPANY "DONE'TSKSTEO IRON AND STEEL WORKS" Actual Inventors: Kovzun 1(GOR; Protsenko IRYNA; Jlberg ZOYA; Filatov YURIY; llyashov MYKI-IAILO; Volovyk VOLODYMYR; Youshkov YEVGE.NIY; and Viter VALERI I Address for service in A J P 3 ARK, Level 11, 60 Marcus Clarke Street, Canberra ACT Australia: 2601, Australia Invention Tide: A METHOD FOR ARSENIC REMOVAL AND PHOSPHOROUS REMOVAL OUT OF IRON ORE The following statement is a full description of this invention, including the best method of performing it known to us, 23401 57-1 2 A METHOD FOR ARSENIC REMOVAL AND PHOSPHOROUS REMOVAL OUT OF IRON ORE The invention relates to the metallurgy field and the metallurgy and mining field and, more specifically, to the physico-chemical processes of the preparation of iron ores, iron ore concentrates, titanomagnetites, iron and manganese ores, iron and chromium ores, manganese ores, and other ores as well as metallurgical sludges before their metallurgical and hydrometallurgical treatment for the purpose of improving quality owing to the removal of undesirable impurities, first of all, arsenic and phosphorous as well as zinc and lead and the isolation of valuable impurities such as vanadium, chromium, nickel, silver, bromine, and others out of these ores, concentrates, and sludges. Iron ores for use in the industry, for example, in a blast-furnace melting, are subjected to concentration to produce concentrates which should meet standard requirements as to both an iron content (between 48 weight percent and 62 weight percent) depending on the ore type and an arsenic content (<0.05 weight percent), phosphorous (<0.25 weight percent) [Ye. F. Vegman (ed.), Blast-Furnace Production, Reference-book, Vol. 1, Ore Preparation and Blast-furnace Process, Moscow, Metallurgy, 1989, p. 496]. Different technologies have been developed for different types of ores both for their concentration and the removal of impurities for the purpose of preparation for metallurgical refining. Substandard ores, mostly, of a sedimentary type, whose quantity in the world reserves approaches 20% and increases all the time are the most attractive among such types of ores. Processing such ores constitutes, therefore, an actual problem for, even though such processing is complicated, is connected with additional costs, it pays its way in conjunction with an increase in the cost of metallurgical raw materials and their shortage. In addition, technologies are possible wherein rare and valuable components such as alloying elements, zinc, lead, bromine, silver, gold, rhodium and others are extracted simultaneously.

In conjunction with this, chemical technologies which are of interest not only for Ukraine but also for Russia, Japan, the United States, China, Germany, Brazil, France, Italy, the United Kingdom, India, the Czech Republic, Canada, Romania, South Korea, Poland, Australia, the Netherlands, Slovakia, and other states are being developing not only in the metallurgy of rare metals and nonferrous metals but also in the ferrous metallurgy. It has been found that, in the chemical processing of ores, phosphorous, arsenic and vanadium are removed together; this is also known from the analysis of iron minerals, silicate minerals and other minerals. In addition, rare and valuable elements are also removed and concentrated [V. F. Gillebrand et al., Practical Guide in Inorganic Analysis, Moscow, Chemistry, 1966, p. I111]. This fact has caused an increasing interest in the chemical processing of iron ores, manganese ores and other ores for the purpose of the removal of undesirable impurities such as arsenic, phosphorous, zinc, lead, silicates and others. An ore containing between 30 weight percent and 48 weight percent of iron, between 0.1 weight percent and 0.4 weight percent of arsenic, between 0.5 weight percent and 1.0 weight percent of phosphorous are customarily processed. Such ores contains oolites and a cementing mass, included therein are hydrogoethite, goethite, magnetite, ferrimontmorillonite, phosphates (apatite, vivianite, and others), arsenic-bearing minerals (realgar, orpiment, mispickel, scorodite, and others), silicates (feldspars, quartz, and others) which are a fine coalescence with admixtures with a minimum particle size of between about 0.05 jim and about 2 pm and a maximum particle size of up to about 0.05 mm. Mechanical methods fail to remove such admixtures down to permissible levels and, therefore, hydrometallurgical technologies of arsenic and phosphorous removal are employed. Known from the state of the art is a method for the removal of arsenic and phosphorous out of iron ore wherein ore crushed and milled to a size of between 0.05 mm and 0.5 mm is treated with a 0.5% to 2% solution of sulfuric acid at a high liquid phase-to-solid phase ratio (L:S) for between about 10 hours and about 25 hours, and 4 then impurities are extracted from the solution by the ion-exchange method [French Patent No. 1.505.100, Cl. C22B 3/06, published in 1963]. The disadvantages of this prior art method include a long duration of the process and large quantity of the liquid phase which requires a large volume of process equipment. Known from the state of the art is also a method for the removal of phosphorous out of iron ore together with sulfur by mixing it with between 6 percent and 7 percent of soda, heating up to 300'C, and washing the mixture with hot water [US Patent Series No. 3.928.024, Cl. C22B I/1 1, published in 1975]. The disadvantages of this prior art method include an insignificant removal (up to 10 percent to 30 percent) of phosphorous, arsenic and other impurities contained in ore. Known from the state of the art is also a method for arsenic removal out of arsenic pyritic which method comprises a preliminary activation of ore by means of milling in a planetary mill at an acceleration of between 40g and 50g for between 5 minutes and 30 minutes, leaching arsenic with a 2% alkaline solution at S:I=1:10 for about 48 hours [T. S. Syrtlanova et al. Proceedings of the Siberian Division of the Academy of Sciences of the USSR, Chemical Science Series, 1979, edn. 3, No. 7, pp.50-5]. In this prior art method, a high degree of leaching arsenic is achieved but this method may only be utilized for pyritic ores; a long duration of the method requires a substantial consumption of alkali (20 percent of the ore weight), and enables a leached material containing between about 0.22 percent and 1.5 percent of arsenic to be obtained. The methods which utilize low processing temperatures and low acid and alkali concentrations are, thus, ineffective and, therefore, a more severe environment of a chemical or heat treatment with 40 percent to 50 percent alkali in autoclaves at between 125 0 C and 140'C or with 60 percent to 70 percent sulfuric acid at between 95 0 C and 100 C are employed [The 8 Ih International Congress for the Beneficiation of Minerals, Vol. 2, Leningrad, Mechanobr Publishers, 1969].

In the prior art method, a substantial consumption of reagents results, however, in the cost ineffectiveness and chemical danger thereof. Known from the state of the art is a method for phosphorous removal out of ore by an oxidizing roasting at between 800 0 C and 1000 0 C for 1 hour, by leaching with a 49% sulfuric acid or nitric acid at S:L=l :1-1:2 at between 20'C and 50'C for between 2 hours and 3 hours [Russian Patent No. 2 184 158, Cl. C22131/11, published on 27.06.2002]. The disadvantages of this prior art method include high losses of iron which account for between 4 percent and 8 percent, a high chemical activity of solutions which causes corrosion of equipment. The most similar to a method in accordance with the present invention is a method for arsenic removal and phosphorous removal out of iron ore, the method comprising ore grinding and milling; a preliminarily roasting at between 500'C and 600'C for between 1 hour and 1.5 hours; leaching, out of the roasted iron ore, arsenic and phosphorous with sulfuric acid (between 100 percent and 150 percent of stoichiometry relative to phosphorous) at between 60'C and 80'C, S:L=:3-1:5 , and a leaching duration of between 2 hours and 3 hours [R.D. Dukino, V. M. England. Phosphorous in Iron Ores of the Hainersley Range, the Australian Institute of Mining and Metallurgy (AusIMM) 1997, No. 5, pp.197-202]. The disadvantages of this prior art method include a low extraction of arsenic (up to 30 percent) and phosphorous (up to 60%), a low iron content of the iron ore concentrate; the impossibility to extract zinc and lead, as well as useful and rare elements out of iron ore; and a substantial consumption of acid and alkali. Accordingly, the task to be solved with the present invention is to improve a method for arsenic removal and phosphorous removal out of iron ore wherein mixing a crushed and milled ore with a carbon reductant and a carbonate sludge; a preliminary roasting of the mixture in an oxygen-containing environment; cooling the product so obtained with water and aqueous solution; and a magnetic concentration in presence of an aqueous solution of an inorganic reagent ensure the production of iron ore 6 concentrates suitable in terms of an arsenic content and phosphorous content thus ensuring an increase in iron content with a low content of arsenic and phosphorous, the possibility of extracting additionally zinc and lead harmful for the metallurgical process, as well as useful and rare elements, and reduction in acid and alkali consumption. The set task is solved by a method for arsenic removal and phosphorous removal out of iron ore, the method comprising ore crushing and milling; its preliminarily roasting; leaching out of the roasted iron ore, arsenic and phosphorous with an inorganic reagent solution; and separating a liquid phase from the solid phase, which, in accordance with the invention, is characterized by the following: - Mixing the crushed and milled iron ore with a carbon reductant and a carbonate sludge; - A preliminarily roasting of the mixture so obtained in an oxygen-containing environment; - Cooling of the resulting product with water or an aqueous solution of alkali; and - A magnetic concentration in presence of an aqueous solution of an inorganic reagent. Furthermore, the mixture is preferably roasted at a carbon reductant-to-carbonate sludge-to-ore ratio of (8-12):(1.5-2.5):100, respectively; the carbon reductant comprises peat, coal, or coke; the carbonate sludge comprises a sludge received after filtering an aqueous solution of lime and soda; sodium chloride or seawater is added at the mixing step; the leaching step is carried out using an 8 percent to 12 percent solution of the carbonate sludge filtrate calculated with reference to sodium hydroxide at an initial temperature of between 90 'C and 105 'C with no further heating; the mixing step and the leaching step are accomplished using a solution of lime and soda with a mole ratio of 0.95:(1-1.1), respectively; the sodium hydroxide solution is prepared using seawater; and the lime and soda solution is prepared using seawater. The essence of the present invention will be explained hereinafter with the reference to a process flow diagram of iron ore beneficiation and iron concentrate beneficiation 7 with an alkaline extraction of arsenic and phosphorous and a partial extraction of vanadium shown in Fig. 1. The method in accordance with the present invention may be practiced as follows. Iron ore is crushed and milled and is mixed with a carbon reductant and a carbonate sludge. The carbon reductant comprises peat, coal, or coke this being mixed with the carbonate sludge and the iron ore at a ratio of (8-12):(1.5-2.5):100; and the carbonate sludge comprises a sludge obtained after filtering an aqueous solution of lime and soda. At the step of cooling and mixing a roasted mixture of iron ore, the reductant, and the carbonate sludge, an alkaline solution or a solution formed after mixing a lime suspension in water or seawater with the soda solution at a mole ratio of 0.95:(1- 1.1) is added. Such ratio is determined by that the purity of commercial products accounts usually for 95% this being of a particular importance for soda, because its shortage would result in an incomplete decomposition of Ca(OH) 2 which impairs the leaching process. Where the solution of lime and soda is used, an alkali solution is formed by reaction: Ca(OH)2 + Na 2

CO

3 = CaCO 3 + 2NaOH. After filtering, a fine CaCO 3 with admixtures of Na 2

CO

3 and NaOH- is introduced in the charge this contributing to the formation therein of mixed sodium potassium phosphates and arsenates solved in alkaline solutions. Soda utilization in the method in accordance with the present invention is 100%. The preliminarily oxidizing roasting of the charge of the mixture of iron ore, the carbon reductant preferably taken in a quantity of between 8 weight percent and 12 weight percent of ore, and sodium chloride a quantity preferably of between 0.5 weight percent and 2 weight percent of ore is carried out in flue gas atmosphere at between 805'C and 900'C for between about I hour and about 1.5 hours. Hot water is discharged to a 8% to 12% alkali solution so that a suspension temperature is close to the boiling point and a ratio S:L=1:1-1:1.2.

8 The range of reductant content (calculated with reference to carbon) of between 8 weight percent and 12 weight percent is determined by that if its content is less than 8 weight percent, reduction is incomplete and, its content is more than 12 weight percent, economic figures are degraded. Roasting in the flue gas oxidizing atmosphere and reduction in the iron ore mass enable the following reactions to occur: As 2

S

3 + C + 502 4 As 2 0 3 + 3SO2 3 + CO (1) 6FeAsS + C + 1502 4 Fe304+ As 2

S

3 + 6 S02 + CO (2) 6FeAsO 4 + C + 902 -> 21304 + 3As 2 0 3 ± CO (3) As 2 0 3 formed thereby sublimes out of the structure of minerals to the surface of iron oxides where it chemisorbs. During the following alkaline treatment, arsenic in the form of sodium arsenites goes to the solution. Where roasting is carried out in an oxidizing environment, the reactions similar to the chemical reactions (1), (2) occur without carbon participation whilst the reaction (3) becomes impossible. Leaching of scorodite (FeAsO 4 21-1 2 0), because of its poor solubility in a weak alkali (between 8 weight percent and 12 weight percent) occurs incompletely and a significant portion of arsenic does not go to the solution. Following roasting, ore is discharged to the alkaline solution from which the magnetic concentration of iron ore is accomplished. Achieved thereby is the utilization of the heat of a hot charge to heat the alkaline solution to a temperature close to the boiling point of the solution, as well as leaching simultaneous with magnetic concentration this excluding the necessity of a repeated heating of the charge: at first, for the magnetic concentration and then heating for the purpose of leaching. In addition, it has been found that the detention of the roasted charge in an alkalescent water during a preliminary magnetic concentration reduces the yield of arsenic and phosphorous to aqueous solutions.

9 Quenching the roasted charge from the roasting temperature down to the boiling point of the solution by discharging the roasted material to the alkaline solution or by water application after discharge from the furnace result in the conservation of water solubility of mixed sodium potassium and sodium ferrous phosphates and metaphosphates formed at high temperatures. Likewise, quenching during contact with water impacts on the solubility of arsenic and phosphorous compounds, as well as results in the cracking and disintegration of particle aggregates and the formation, within their structure, of an internal system of large transport pores this facilitating the following process of arsenic removal and phosphorous removal with alkali solutions or acid solutions. A wet magnetic concentration is performed so that a leaching duration is between 1 hour and 3 hours and the final temperature is between 20'C and 50'C. A magnetic product and tailings of beneficiation are filtered, washed with water whose volume is sufficient enough to displace the volume of alkali bonded in a porous space of the cake (magnetic and nonmagnetic). Following the alkaline treatment, the filtrate and washings are mixed and directed to the stage of chemical deposition of salts of arsenic, phosphorous, vanadium and other elements depending on an output composition of ore. The filtrate is fed for the purpose of leaching new portions of the roasted ore. The cakes separated from the filtrate are washed with service water or seawater. Washings are fed to cool the hot roasted ore which is discharged from the furnace whilst steam formed is condensed in a heat exchanger; the condensate is fed for the final washing of the cakes to a washing p-I of between 7.5 and 8.0. The nonmagnetic cake (tailings) goes to the dump or is processed, for example, into building materials or phosphate fertilizers. Following the magnetic concentration, a filter cake is washed at a low filtration rate with 1 percent to 2 percent solution of sulfuric acid or nitric acid so that the duration of contact of the acid solution and the cake is between 15 minutes and 30 minutes and pH of the filtrate flowing out is between 6.5 and 7. The cake is washed with water whose volume is equal to that of water bonded on the porous space of the cake. Following the acid treatment, the filtrate and washings are mixed and fed to remove 10 salts of arsenic, phosphorous, vanadium, chrome, nickel, bromine and other elements (depending on the ore chemistry). If required, the magnetic concentrate is fed additionally to the bloomery process where up to 40 percent of arsenic and up to 30 percent of phosphorous which remained in the concentrate are removed additionally. Phosphorous is contained in ores mostly in the form of vivianite (FePO 4 apatite, phosphorite (Ca 3 (P04) 2 ) as well as, as the recent data say, wavelite (AIFe(PO4)2) The complete disintegration of such minerals in the presence SiO 2 occurs at 1500'C with the formation of phosphorous vapors and slag (calcium silicates), but P 2 0 5 is evaporated as early as at 185 0 C, and, at the higher temperatures (>800'C), the structure of phosphates is inclined to "swinging" this facilitating the proceeding of reactions with NaCl and carbon, for example: FePO 4 +C+NaCl+H 2 0 - FeNaPO 3 + ICI + CO 2 4 (4) FeAsO 4 +C+NaCl+H 2 0 4 FeNaAsO 3 + H Ci + CO 2 (5) Ferrous iron metaphosphate formed in the alkaline solution converts, after being exposed to hydration processes, to a water-solvable form; during hydrolysis provided for the latter, phosphoric acid is bonded with alkali and goes to the solution in the form of sodium metaphosphate. There is required the presence, in the charge, of a small quantity of NaCl which is the catalyst (mineralizer) of processes (4) and (5) and which is added advantageously together with seawater, particularly if the ore deposit in question is near the sea, for example, iron ore of the Kerch Basin. However, an increase in the content of NaCl by more than 2 percent would cause charge caking at over 800'C this complicating the leaching process. Examples of practicing the method in accordance with the present invention by means of a roasting-magnetic concentration and treatment in an alkaline environment and then in an acid environment and of the bloomery process using two types of iron ores from the Kiz-Aul Deposit of the Kerch Basin will be now described in detail: - A yellow-brown, i.e., tobacco-colored clay lean ore No. I which contains (weight percent) Ca(=1 .9; Si0 2 =41.4; Al20 3 =8.8; Mn=0.4; Fe=,29.8; As=0.09; Pn1.05; and V=0.0 ; - A brown iron and manganese ore No. 2 which contains (weight percent): CaO=2.5; Si02=7.1; Al 2 03=4.1; Mn=12.3; Fe=39.1; As=0.33; P=0.58; 1=0.001. These ores may not be concentrated by the gravity method due to the growth of nanometric particles of iron oxide and silicate minerals into each other, therefore, in these experiments, use was made of ores without gravity concentration. EXAMPLE 1 A 10 % solution of alkali was prepared by mixing 200 cm 3 of an aqueous solution of soda (25.5 g) with 18.5 g of lime containing 95 weight percent of Ca(OHI) 2 a mole ratio Ca(OH) 2 :Na 2

CO

3 being 0.95:1. The solution (200 cm 3 ) was separated frorn a precipitate (25 g of CaCO 3 + I g of Na 2

CO

3 + 0.8 g of NaOH), the precipitate was added to 200 g of ore No. 2, to which ore 2 g (1 weight percent) of NaCl and 16g (8 weight percent) of coke were also added. The resulting charge in a fireclay crucible was placed in a muffle furnace in an oxygen-bearing flue gas atmosphere after the combustion of a coal. The muffle furnace was heated for 30 minutes from 600'C up to 805'C and was kept for 1 hour. The roasted charge at 500'C was poured into 200 cm 3 of the 10 % solution of alkali till its boiling. A hot suspension was stirred for 3 hours (in 3 hours, a suspension temperature was 25 0 C). Magnetic particles (77 percent) were separated from nonmagnetic particles (23 percent). After washing the magnetic suspension and nonmagnetic suspension, 200 em 3 of an alkaline solution containing salts of arsenic, phosphorous, and vanadium were obtained. After precipitation with lime, a precipitate (2.2 g) containing (weight percent): Ca=20.6; V=0.62; Mn=5.6; Fe=2.0; Ni=0.03; Cu=0.02; Ge=0.005; As=8.1; 13r=0.65; Sr=9.3; Ag=0.075, P=10.2 was separated from the solution. The magnetic fraction (154 g) was washed on the filter with 200 cm 3 of a 1% 11 2 S04 The resulting filtrate was treated with lime and 9.6 g of a precipitate containing 12 (weight percent): Ca=5.6; V=0.32; Cr=0.26; Mn=21.8; Fe=0.2; Zn=0.12; As=17.4; Br=0.95; Sr=3.3; P=21.3 was obtained. 151 g of the washed concentrate containing (weight percent): Ca=0.59; T1=0.31; V=0.0005; Mn=15.5; Fe=51.1; As=0.015; Sr=0.45; Y=0.06; P=0.20 were obtained. 15 weight percent of coke were added to the concentrate and the mixture was heated in a reducing environment up to 1300'C. Following the separation of the magnetic fraction and nonmagnetic fraction, a bloom containing Fe=79.6 weight percent; As=0.004 weight percent; P=0.12 weight percent; V=0.00l weight percent was obtained the total yield being 81 weight percent. The other examples of practicing the method for arsenic removal and phosphorous removal out of iron ore in accordance with the present invention are set forth in Table I below where the composition of the carbon reductant and mixture roasting in the oxygen-containing environment are shown, and in 'Fable 2 where the yield of roasted ore and the chemistry thereof after the magnetic concentration and bloomery process are presented. In addition, these tables contain an example (No. 0) of practicing the method for arsenic removal and phosphorous removal out of iron ore in accordance with the prototype. Table I Example Ore Carbon Reductant, % Roasting 1bSO 4 , NaOH, CaO1 0 No. No. Ore lea Coke Coal NaCl temperature, S % % Na 2

CO

3 0 N2 100 - - - - 805 1:3 0.5 0 1 M42 91 - 8 - 1 805 1:1 1 12 0.95:1 2 N2 87 - 12 - 1 805 1:1 1 8 0,95:1 3 N12 89.5 .- 10 - 0.5 900 1:1.2 1L | 10 1:1 4 N22 89 10 - - 1 900 1:1 0.5 10 1:1.1 5 N22 88 10 - 2 900 1:1 0.5 10 0.95:1 a N22 89 - - 10 1 900 1:1 1 | 10 7 1l 89 - 10 - 1 900 1:1.2 1L | 10 8 Nel 94 - 5 - 1 900 1:1.2 1 10 9 Ne1 89 10 - 1 615 1:1.2 1 10 10 N1l 88 10 2 900 1:1.2 2 10 0.95:1 11* Sudge 89.8 - 8.8 - 2 805 1:1.2 2 10 - 13 Table 2 Example No. After Magnetic Concentration After Bloomery' Process Yield, % Fe, As, J), Yield, % Fe, As, P, w/wL %ww %w/w %V0 w/Iw w/w % w/w %l w/w w/w 0 68 442 0.27 0.35 - | 77 51.1 0,015 0.20 81 79.6 0.004 0.12 2 78 50.9 0.014 0.19 - - 3 75 51.4 0.016 0.21 - - - 4 77 51.3 0.014 0.24 - - - 5 75 50.8 0.017 0.25 - - - 6 76 50.8 0,014 0.22 - - 7 67 49.3 0.001 0.20 79 74.2 0,000 0.13 8 59 48.1 0.015 0.30 - 9 61 46.5 0.025 0.37 - - - 10 60 49.9 0.005 0.21 11* 79 60,5 0.001 0.11 - - - where 11* is metallurgical sludge containing (weight percent): Fe=44.3; SiO2=5.7; MgO=3.7; CaO=8.9; MnO=0.55; C=8.8; As=0.081; P=0.27; Zn=0.41; Pb=0.11. Based on the analysis of the results in the above tables, it may be concluded as follows: The optimum roasting temperature is between 805'C and 900'C; the alkaline solution concentration (calculated with the reference to NaOH) is between 8 percent and 12 percent; the acid concentration is up to 2 percent. Any increase in temperature over 900'C results in a non-productive heat consumption and any increase in the concentration of acid and alkali over 2 percent and 12 percent, respectively, does not result in any improvement provided for the process parameters during an overconsumption of the reagents. Moreover, at an acid concentration of over 2 percent, iron leaching would increase; for the same reason, the minimum S:L ratio is 1:1.2 because in the event of a higher consumption of liquid a reagent consumption increases as well. As can be seen from Example 11*, the method in accordance with the present invention may process effectively metallurgical sludges (beneficiation tailings) from which one manages, subject to obtaining a saleable product, to extract substantially all arsenic and phosphorous, as well as zinc and lead; furthermore, useful admixtures (Cr, Ni, Cu, V, Ag, and others) which may be later extracted by chemical methods known to those skilled in the art may also be extracted to the solution.

14 The comparison of the method in accordance with the present invention with its prototype also shows that, in all of the events except for Example 8 with a low alkali concentration (5 percent) and Example 9 with a low roasting temperature (615'C), better results are achieved: phosphorous extraction and arsenic extraction are by 50 percent to 70 percent higher than whilst a reagent consumption is the same as in the prototype. The consumption of alkali although the latter is used in the form of 8 percent to 12 percent solutions is also insignificant because, following the removal of arsenic, phosphorous , vanadium, zinc, lead, and others out of the used alkaline solution, the latter is returned to the leaching process, and thereby alkali is only lost with washings; but, since such washings are fed to cool the roasted charge by the "quenching" method, alkali from the washings enters the process once more. Our studies have proved that losses of alkali per a cycle do not exceed 0.3% to 0.5%. In addition, the cost of alkali is significantly (1.5 times) reduced owing to the utilization of a mixture of lime and soda; and sludge from their interaction goes to the charge for roasting. The weak-acid and low-alkali solutions are mixed this providing for an additional extraction of rare elements such as Ag, Rh, and others whilst effluents are neutralized. Therefore, the method for arsenic removal and phosphorous removal out of iron ore in accordance with the present invention has a number of advantages over the nearest prototype thereof, namely: 1. A specification product is obtained which product contains between 60 weight percent and 80 weight percent of iron and has a low content of arsenic (0.015 weight percent) and phosphorous (between 0.20 weight percent and 0.25 weight percent) with the possibility of extracting additionally zinc and lead harmful for the metallurgical process, as well as useful and rare elements such as V, Ni, Cr, Zr, Cu, Ag and others); 2. Power requirements do not exceed those of the magnetic concentration process for, during the leaching step, the heat of the magnetizing roasting is used; and 15 3. The consumption of acid and alkali is insignificant and justified technologically and economically: the computations show that, in the event of the optimum consumption of reagents, the extraction of vanadates, phosphates, and arsenates out of alkali to solid products generates profit of up to U.S.$3 per 1 MT of ore. Currently, the method in accordance with the present invention is under bench tests for the purpose of designing a commercial beneficiation plant for a lean ore from one of the iron ore deposits of Ukraine of 6 million MT per year in capacity. The term "comprising" as used in this specification means "consisting at least in part of". When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

Claims (10)

1. A method for arsenic removal and phosphorous removal out of iron ore, the method comprising ore crushing and milling; preliminary roasting; leaching arsenic and phosphorous with an inorganic reagent solution; and, separating a liquid phase from a solid phase, characterized in that crushed and milled iron ore is mixed additionally with a carbon reductant and a carbonate sludge; said mixture is roasted preliminarily in an oxygen-containing environment; and a resulting product is cooled with water or an aqueous solution of alkali and is subjected to magnetic concentration in the presence of an aqueous solution of an inorganic reagent.

2. The method as claimed in Claim 1, characterized in that the mixture is roasted at a carbon reductant-to-carbonate sludge-to-ore ratio of (8-12):(1.5-2.5): 100, respectively.

3 The method as claimed in Claim 1 or Claim 2, characterized in that the carbon reductant comprises peat, coal, or coke.

4. The method as claimed in Claim 1 or Claim 2, characterized in that the carbonate sludge comprises sludge obtained after filtering an aqueous solution of a lime and soda mixture.

5. The method as claimed in Claim 1, characterized in that sodium chloride or seawater is added additionally at the mixing step.

6. The method as claimed in Claim 1, characterized in that the leaching step is carried out using an 8 percent to 12 percent solution of the carbonate sludge filtrate calculated with reference to sodium hydroxide at an initial temperature of between 90 'C and 105 "C with no further heating.

7. Thc method as claimed in Claim 1, characterized in that the mixing step and the leaching step are accomplished using a solution of lime and soda within a mole ratio of 0.95:(1-1A1), respectively.

8. The method as claimed in Claim 6, characterized in that the sodium hydroxide solution is prepared using seawater. RECEIVED TIME 8.MAR. 23:32 17

9. The method as claimed in Claim 4, characterized in that the lime and soda solution is prepared using seawater.

10. A method for arsenic removal and phosphorus removal out of iron ore, the method substantially as herein described with reference to any embodiment shown in the accompanying figure.