WO2012150873A1

WO2012150873A1 - Method for pollution-free processing of sideritic iron ore

Info

Publication number: WO2012150873A1
Application number: PCT/RU2011/000308
Authority: WO
Inventors: Дмитрий Леонидович ЭРЛИХМАН; Андрей Александрович ХАЛЕВ; Сергей Евгеньевич КУЛЬЧИХИН; Эдуард Шаевич ГЕЛЛЕР; Даниэль Эдуардович ГЕЛЛЕР
Original assignee: Erlikhman Dmitriy Leonidovich; Mikhalyov Andrey Alexandrovich; Kulchikhin Sergey Evgenyevich; Geller Eduard Shaevich; Geller Daniel Eduardovich
Priority date: 2011-05-05
Filing date: 2011-05-05
Publication date: 2012-11-08
Also published as: RU2562016C1; RU2012131031A

Abstract

The invention relates to ferrous metallurgy, and specifically, to methods for preparing and subsequently processing sideritic ores. The sideritic iron ore is prepared for processing by the base ore being crushed, sifted, and decarburized with soaking. A possible alternative for carrying out decarburization under oxidative conditions comprises preparing an aqueous pulp and dividing the latter into an iron ore concentrate and barren rock. The pulp is acted upon by an acid, leaching out magnesium and calcium oxides, and the solution formed is separated from the residue, which is washed and dried, producing a concentrate. Magnesium hydroxide is precipitated from the solution with the addition of milk of lime or dolomitic milk, the magnesium hydroxide then being dried and roasted, producing a magnesite concentrate. The acid is regenerated by feeding sulphuric acid into the solution, wherein the calcium sulphate extracted at the same time as the acid is regenerated is washed and dried, producing commercial gypsum, and the regenerated acid is used repeatedly for leaching out the pulp. The invention is directed towards producing a high-quality iron ore concentrate with a reduction in energy consumption.

Description

METHOD FOR NON-WASTE PROCESSING OF SIDERITE IRON ORE

The invention relates to ferrous metallurgy, namely, the preparation of siderite iron ores for processing and processing prepared siderite iron ores, and can be used in the preparation of siderite iron ores for blast furnace smelting.

It is known that iron ores of siderite composition, unlike other types of iron ores, contain an increased amount of magnesium oxide. The excessive content of magnesium oxide in the ore during its subsequent metallurgical processing (iron smelting, direct iron reduction processes) gives metallurgical slag increased viscosity and refractoriness, which impedes the normal course of the process.

Moreover, in the original siderite, the compounds of iron and magnesium are closely related to each other. In addition, the chemical properties of magnesium carbonate (MgC03) and iron carbonate (FeC03) are very close to each other, because the ionic radii of iron and magnesium are also very close. For this reason, siderite iron ore is not amenable to the classical enrichment methods used in ferrous and non-ferrous metallurgy (magnetic, gravitational, flotation, electrostatic, etc.)

Before enrichment of siderite ore, it is necessary to destroy its structure in order to break up close bonds between minerals of iron and gangue, including magnesium, after which it becomes possible to enrich ore in order to reduce the content of magnesium oxide and other non-metallic components in it.

A known method of preparing lump siderite ores for blast furnace smelting, described in the same as. USSR N2 863682 according to class C22B 1/04, c. 0.6.09.79, op. 09/15/81.

The known method consists in the fact that lumpy siderite ore is crushed in two stages of 40-0 mm, subjected to wet screening in classes 40-10, 10-0 mm, then class

40-10 enrich in heavy suspensions, and the selected concentrate is subjected to oxidative firing at a firing speed of 0.18 - 0.22 t / m ³ -h at 1000-1 100 ° C for 200 - 240 minutes, the calcined concentrate is screened for classes 40 - 8 mm and 8 -0 mm. Slice 40-8 is intended for blast furnace smelting, and seeding of grade 8-0 and raw ore 10-0 are agglomerated.

The disadvantage of this method is the low strength of the resulting lump concentrate. During firing, siderite decarbonization occurs, which is accompanied by the destruction of the crystal lattice, the formation of a large number of pores, cracks. Due to the low firing temperature, solid-phase sintering of grains in a piece occurs slowly, and even long exposure times at firing temperatures do not lead to a piece with a satisfactory abrasion resistance, which has a value of at least 16%. During blast furnace smelting of such lumpy concentrate, due to the high abrasion resistance index, dust removal increases, thereby increasing iron loss, and the environmental situation at enterprises using this raw material is deteriorating.

A known method of enrichment of siderite ores described in the same patent of the Russian Federation N ° 2283183 class. B03C1 / 00, c. 03/17/05, op. 09/10/2006.

A known method is as follows.

The siderite ore is crushed and screened to a particle size of 6-0 mm, a dry magnetic separation of the initial ore is carried out, then a magnetic firing is performed, and then a dry magnetic separation of the calcined product is carried out, while dry magnetic separation of the initial ore and dry magnetic separation of the calcined product are carried out in a non-uniform magnetic a field in which three zones are created in the direction of flow of the material flow with magnetic field strength varying in them according to the extreme dependence, and with dry magnetic sep of the source ore, the maximum magnetic field strength in the first zone is set equal to 1250-129-kA / m, and in the second and third zones of the magnetic field the maximum intensity is successively reduced relative to the maximum intensity of the first zone in accordance with 1: 0.83: 0.74, with dry magnetic separation of the calcined product, the maximum magnetic field strength in the first zone is set equal to 80-86 kA / m, in the second and third zones it is successively reduced relative to the maximum intensity of the first zone in accordance with 1: 0.78: 0.67 .

The disadvantage of this method is its complexity and energy intensity. In addition, iron hydroxides contained in the ore are not magnetized during oxidative roasting and, therefore, are removed together with gangue during magnetic separation, reducing the iron content in the ore. There is a method of preparing siderite for blast furnace smelting, described in the same patent of the Russian Federation Ns 2041963 according to class. C22B 1/04, c. 04/08/93, op. 08/20/95.

The known method consists in the fact that the ore is crushed, subjected to screening, dressing and conduct oxidative firing in an atmosphere containing not more than 4% oxygen at a temperature of 1200-1350 ° C.

The objective of the known method was the strengthening of lump concentrate due to liquid phase sintering.

The disadvantage of this method is the low quality of the resulting concentrate due to the insufficiently high mass fraction of iron and a significant mass fraction of magnesium oxide in it.

There is a method of preparing siderite ores for blast furnace smelting, described in the book "Guide to the beneficiation and agglomeration of ferrous metal ores", M., "Nedra", 1964 p. 314 and selected as a prototype.

The known method includes crushing the source ore to 60 mm, screening into grades 60-10 and 10-0 mm, oxidizing roasting of lump ore of the class 60-10 mm in shaft furnaces at 900-1000 ° C for 270-300 min, screening the calcined product into classes 60-8 and 8-0 mm, magnetic separation of each class on weak field separators.

Then the lumpy concentrate is sent to blast-furnace smelting, and siderite ore of the class 10-0 mm without enrichment undergoes agglomeration in a mixture with brown iron ore.

The disadvantage of this method is as follows.

Unfinished crushed ore is sent for firing in shaft furnaces, then, during magnetic separation of the fired ore, waste rock is removed, and with it iron hydroxides, which are not magnetized during oxidative firing. In addition, it is impossible to increase the firing temperature at 900 ° C due to the expansion of the shales that make up the gangue and their sticking to the walls of the furnace, enveloping pieces of siderite, which sharply affects the gas permeability of the charge. Moreover, the degree of decarbonization and magnetization of large classes of ore (40-60 mm) is insufficient, which leads to an increase in losses of calcined ore with tailings of magnetic beneficiation and a decrease in the quality of iron ore concentrate.

In addition, the process is very energy intensive due to the high firing temperature, magnetic separation. The task of the claimed group of inventions is to increase the quality of concentrate while preparing ore for processing while reducing energy consumption for subsequent production of high-quality iron ore concentrate and associated high-quality products from waste-free processing from prepared ore.

The problem is solved in that:

- in the first embodiment, in the method of preparing siderite iron ore for processing, namely, that the ore is crushed, screened, and siderite is decarbonized, ACCORDING TO THE INVENTION, crushing and screening is carried out to a particle size of 2.0-0 mm, siderite is decarbonized by heating crushed ore to a temperature of 600-700 ° C and holding it at this temperature for 60-120 minutes;

- in the second embodiment, in the method of preparing siderite iron ore for processing, namely, that the ore is crushed, screened, and siderite is decarbonized, ACCORDING TO THE INVENTION, the initial ore is crushed and screened to a particle size of 2.0-0 mm, siderite is decarbonized, heating the crushed ore to a temperature of 100-160 ° C, keeping it at this temperature for 60-240 minutes at a pressure of 1.0-10.0 atm, and passing an oxidizing agent through the ore.

In this case, the oxidation process can be carried out in an aqueous medium or in the absence of water, and air oxygen, industrial oxygen, chlorine, nitrogen oxides, hydrogen peroxide, etc. can be used as an oxidizing agent.

- in the method of non-waste processing of siderite iron ore, namely, that the initial siderite ore is prepared for processing, prepared for processing siderite ore is divided into iron ore concentrate and waste rock, ACCORDING TO THE INVENTION, siderite ore is prepared for processing by one of the methods described above, and To separate the prepared ore into iron ore concentrate and waste rock, water is added to it and a pulp is prepared, which is exposed to acid to leach oxides of m magnesium and calcium, then the resulting solution is separated from the precipitate, which is washed and dried to obtain an iron ore concentrate from it, and magnesium hydroxide is precipitated from the solution by adding lime or dolomite milk, which is then dried and calcined to obtain a magnesite concentrate, after which the acid is regenerated, feeding sulfuric acid into the solution, the calcium sulfate released at the same time as the acid is regenerated is washed and dried to obtain gypsum, and the regenerated acid is reused to leach the pulp.

At the same time, nitric or hydrochloric acids can be used as the acid for leaching oxides of magnesium and calcium.

In the first version of preparing siderite ore for processing, crushing and screening the ore to a particle size of 2.0 mm improves the degree of decarbonization of the ore, which together with decarbonization at a temperature of 600-700 ° C reduces the energy consumption of the method, ensuring high-quality decarbonization for 60-120 minutes , i.e., improving the quality of iron ore concentrate.

In the second variant of preparing siderite ore for processing, crushing and screening the ore to a particle size of 2.0 mm improves the degree of decarbonization of the ore, which, together with heating the crushed ore to a temperature of 100-160 ° C, keeping it at this temperature for 60 -240 minutes at a pressure of 1.0-10.0 atm, provides high-quality decarbonization. Passing an oxidizing agent through the ore ensures the transition of iron from an unstable divalent state to a more stable trivalent state, which also improves the quality of iron ore concentrate and reduces energy consumption for preparing the ore for further processing.

The technical result in both versions is to improve the quality of iron ore concentrate while reducing the energy intensity of the process.

In the non-waste processing method of siderite iron ore, the use for ore processing prepared by the above methods in conjunction with the preparation of pulp from the prepared ore, followed by leaching of oxides of magnesium and calcium from the latter, separation of the iron ore concentrate from the precipitate, precipitation from the solution using lime or dolomite milk of magnesite concentrate and acid recovery with the release of gypsum provides practically waste-free processing ku siderite ore release from it a high-quality iron ore concentrate and preparation of "empty" for the blast furnace rock mineral magnesite concentrate and plaster.

EFFECT: obtaining high-quality iron ore concentrate and associated high-quality products from prepared ore. W

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The claimed group of inventions has novelty in comparison with the prototype, differing from it:

- in the first version of the method of preparing siderite iron ore for processing by the presence of such essential features as crushing and screening to a particle size of 2.0-0 mm, decarbonization of siderite by heating the crushed ore to a temperature of 600-700 ° C and keeping it at this temperature in the course of 60-120 minutes, which together ensure the achievement of a given result;

- in the second version of the method of preparing siderite iron ore for processing by the presence of such essential features as crushing and screening of the original ore to a particle size of 2.0-0 mm, decarbonization of siderite by heating the crushed ore to a temperature of 100-160 ° C, keeping it at that temperature for 60 -240 minutes at a pressure of 1.0 to 10.0 atmospheres, and passing an oxidizing agent through the ore, which together provide the desired result. - in the method of non-waste processing of siderite iron ore by the presence of such essential features as preparing siderite ore for processing by one of the methods described above, preparing pulp to separate the prepared ore into iron ore concentrate and waste rock, exposing the pulp to acid to leach magnesium and calcium oxides, separation the resulting solution from the precipitate, obtained from it by washing and drying iron ore concentrate, precipitation from the solution by adding lime or dolomite mo eye of magnesium hydroxide, obtaining from it by drying and calcining magnesite concentrate, the implementation of acid regeneration by supplying part of the solution obtained from the pulp to extract gypsum from it, obtaining from it washing and drying of gypsum, reuse of regenerated acid to leach the pulp, providing aggregate achievement of a given result.

The applicant does not know the technical solutions possessing the essential features indicated in each of the objects of the group of inventions, which together ensure the achievement of a given result for each object, therefore he believes that each of the claimed inventions meets the criterion of "inventive step".

The claimed invention can find wide application in metallurgy, and therefore meet the criterion of "industrial applicability". The invention is illustrated in the drawing, which presents a functional algorithm for preparing for processing and non-waste processing of siderite iron ore.

The inventive first option, the method of preparing siderite iron ore for processing is as follows.

The original siderite iron ore is crushed and screened. Moreover, crushing and screening lead to a fineness of 2.0 - 0 mm. Then siderite is decarbonized, heating the crushed ore to a temperature of 600-700 ° C and keeping it at this temperature for 60-120 minutes;

The inventive second option, the method of preparing siderite iron ore for processing is as follows.

The original siderite iron ore is crushed and screened. Moreover, crushing and screening lead to a fineness of 2.0 - 0 mm. Decarbonization is then carried out.

siderite, heating the crushed ore to a temperature of 100-160 ° C, keeping it at this temperature for 60-240 minutes at a pressure of 1.0-10.0 atm, and passing an oxidizing agent through the ore.

The method of wasteless processing of siderite iron ore is as follows.

The original siderite ore is prepared for processing by one of the methods described above. The siderite ore prepared for processing is divided into iron ore concentrate and waste rock. To separate the prepared ore into iron ore concentrate and waste rock, water is added to it and a pulp is prepared. Acid is applied to this pulp to leach magnesium and calcium oxides. The resulting solution is separated from the precipitate, which is washed and dried, receiving from it iron ore concentrate. Magnesium hydroxide is precipitated from the solution by the addition of lime or dolomite milk, which is then dried and calcined to obtain a magnesite concentrate. After that, feeding sulfuric acid into the solution, acid regeneration is carried out; calcium sulfate released at the same time as acid regeneration rinse and dry to obtain marketable gypsum. The regenerated acid is reused to leach the pulp.

In this case, nitric or hydrochloric acids can be used as the acid. The inventive method of preparing siderite iron ore for processing according to the first embodiment is as follows.

The initial siderite ore is crushed and screened to a fineness of 2.0 mm. Then the crushed ore begins to heat. Iron carbonate FeC03, when heated at a temperature of about 450 ° C, begins to decompose intensively by the reaction:

FeC03 - »FeO + CC-2

The following factors contribute to this:

1) Instability of iron carbonate already with weak heating (over 250 ° C). Removing CO2 from the reaction sphere shifts the equilibrium to the right, i.e. in a direction favorable for the implementation of the method.

2) Iron (II) oxide formed during decomposition of siderite (wustite) is also thermodynamically unstable in accordance with the iron – oxygen state diagram. At temperatures below 570 ° C, it tends to decompose into Fe304 and Fe203 by reactions (i.e., FeO is disproportioned):

4FeO - »Fe304 + Fe

3FeO - »Fe203 + Fe

3) In addition to decomposition, the iron oxide (I) FeO formed during the decomposition of siderite in the air is intensively oxidized to Fe304 and Fe203 by the reactions:

4FeO + 02 -> 2Fe203

This is due to the fact that in the air (due to the presence of oxygen in the air) the trivalent state of iron is more stable than the divalent one.

All of the above facts contribute to the destruction of siderite structure with the formation of new phases and the release of magnesian compounds, i.e. breaks in their close bonds with iron compounds. Therefore, the processes described above create the prerequisites for subsequent selective extraction (extraction) of magnesium compounds from siderite ore. The decomposition of siderite begins at a temperature of 250 ° C, the process acquires a noticeable speed at 450 ° C. Within 1 hour at a temperature of 600-700 ° C, complete decomposition of siderite into iron oxides and CO2 is achieved. In the second embodiment, the method of preparing siderite iron ore for processing is as follows.

The initial siderite ore is crushed and screened to a fineness of 2.0 mm. Then, the crushed ore begins to be heated to a temperature of 100-160 ° C, keeping it at this temperature for 60-240 minutes at a pressure of 1.0-10.0 atm, and an oxidizing agent is passed through the ore.

In this embodiment, the essence of the method is based on the following.

As indicated above, the trivalent state for iron in an oxidizing medium is more stable than the divalent one. By creating an oxidizing environment, it is possible to achieve oxidation of iron carbonate with the formation of ferric hydroxide. This oxidation process can be carried out both in the aquatic environment and in the absence of water.

In an aqueous medium, the process is carried out in an aqueous pulp (suspension) of finely ground siderite. To do this, a stream of air (oxygen) is passed through the pulp, or an increased pressure of air (oxygen) is created in the pulp loaded into the autoclave. As an oxidizing agent, one can use not only air (oxygen), but also chemical compounds with oxidizing properties (nitrogen oxides, chlorine, hydrogen peroxide, etc.)

The chemical nature of the process can be described by the following scheme:

2FeC03 + [О] + ХН2О - »FezOi * χΗιΟ + 2Сог

The process takes place under mild conditions: temperature 100-160 ° C, pressure - 1, 0-10.0 atm. The temperature in this case is much lower than the thermal decomposition temperature of siderite (<450 ° C).

The siderite oxidation process can be carried out even in the absence of water, but in this case, the temperature of the onset of the process will increase to 250 ° C and the siderite oxidation rate will be noticeably lower than in the presence of water. In both cases (in the aquatic environment and in its absence), the time required to complete the process will be 1-4 hours.

The method of waste-free processing of siderite iron ore is as follows.

The source ore is prepared for processing by one of the methods described above. Then, the prepared ore is separated into iron ore concentrate and “empty” for blast furnace smelting, isolating in the end as finished products iron ore concentrate, magnesite concentrate and gypsum.

The technical essence of the separation method is based on the following.

In the original siderite, the compounds of iron and magnesium are closely related to each other.

In addition, the chemical properties of magnesium carbonate (MgC03) and iron carbonate (FeC03) are very close to each other, because the ionic radii of iron and magnesium are also very close.

Before the siderite structure is destroyed by the above ore preparation methods, the bond between iron and magnesium oxides is broken; in addition, iron carbonate is converted into phases containing ferric iron and therefore possessing completely different physicochemical properties.

This property allows efficient extraction (extraction) of magnesium oxide from decomposition products (destruction) of siderite ore.

Among all the compounds present in siderite ore, magnesium and calcium compounds (oxides and carbonates) possess the most basic properties. Therefore, when exposed to acid products of siderite (nitric, hydrochloric, etc.), the compounds of magnesium and calcium will first interact with them to form water-soluble salts (nitrates, chlorides, etc.), for example:

MgCC-z + 2HN03 - * Mg (NOs) 2 + CO2 + H2O

MgO + 2HN03 - »Mg (Νθ3) 2 + НгО

CaCO3 + 2H s -> Ca (s) 2 + CO2 + H2O

CaO + 2ΗΝ03 - * Ca (W) h) g + Н2О

Ferric compounds in this case do not interact with acids, since Fe304 is a chemically strong compound having a spinel lattice, and Fe203 dissolves in a more acidic medium than Mg and Ca compounds. Therefore, with a correctly calculated dosage of acid, magnesium and calcium will go into solution in the form of salts, and iron in the form of oxides containing ferric iron will remain unaffected by the acid.

The proposed method also provides for the extraction of magnesium oxide contained in the ore and its conversion into commercial products with the simultaneous regeneration of the acid used in the process by means of sulfuric acid, which is a cheap and affordable substance obtained from non-ferrous metal ores along with the main metallurgical production. This stage of the proposed method is carried out according to the following scheme:

Calcium oxide is obtained by calcining limestone, chalk or dolomite at temperatures> 1000 ° C.

t> 1000 ° C

CaCO3 - * CaO3 + CO2

Next, the resulting product is "quenched" with the formation of calcium hydroxide:

CaO + SHO - * Ca (OH) g The obtained lime (dolomite) milk in a calculated proportion is poured into a solution containing magnesium and calcium ions. The following chemical reaction occurs:

Mg (N0s) 2 + Ca (OH) 21 -> Ca (S03) g + Mg (OH) 2 1

The process equilibrium is shifted to the right, because the solubility product of magnesium hydroxide is much lower than calcium hydroxide. Next, magnesium hydroxide is washed from impurities of water-soluble compounds, dried and calcined to obtain marketable magnesium oxide

t

Mg (OH) 2 - * MgO + H2O

When using dolomite, the magnesium oxide contained in dolomite is attached to magnesium oxide extracted from siderite, thereby increasing the yield of the product.

An example implementation of the method.

The chemical composition of the original ore, wt.%:

Fe -30.3;

S1O2 6.2;

CaO -3.0;

MgO - 15.2;

p.p.p. - 33.1 - the rest. Ore in the amount of 100 kg is calcined at a temperature of 600 ° C for 1 hour. In this case, siderite is decarbonized and the 2-valence iron is oxidized to the 3-valence state.

After calcining 100 kg of ore, we obtain 67 kg of industrial product material (intermediate product) of the following chemical composition, wt.%:

Fe - 45.2

Si02- 9.3

CaO - 4.5

MgO - 15.2.

Next, the calcined material is mixed with an aqueous solution of nitric acid. The amount of acid in the solution is calculated so that the degree of extraction of magnesium oxide from the concentrate is 80%. When calculating the amount of acid, it is necessary to take into account the dissolution in it of calcium oxide, which has more pronounced properties than magnesium oxide, and therefore will dissolve in the first place. The degree of its extraction in the calculations is taken equal to 100%.

Magnesium oxide, which is part of the intermediate product in the form of carbonate, will interact with nitric acid in accordance with the following equation of the chemical reaction:

MgC03 + 2HN03 Mg (N03) 2 + Н2О + СО2 † (1)

Calcium oxide, which is also in the composition of the intermediate product in the form of carbonate, will dissolve in the same way:

CaCO3 + 2HN03 - »Ca (N03) 2 + H2O + CO2 † (2)

We calculate the amount of nitric acid necessary for the dissolution of calcium and magnesium oxides.

First, we calculate the amount of calcium and magnesium oxides extracted from the intermediate product.

m (CaO) = 67 kg x [4.5% / 100%] = 3.0 kg m (MgO) = 67 kg x [15.2% / 100% x 80% / 100%] = 8.1 kg. Next, we recalculate the oxides of calcium and magnesium on carbonates: m (CaCO3) = m (CaO) x [M (CaCO3) / M (CaO)] = 3.0 x 100.1 / 56.1 = 5.4 kg m (MgC03 ) = m (MgO) x [M (MgC03) / M (MgO)] = 8.1 x 84.3 / 40.3 = 16.9 kg, where m is the mass of the substance indicated in brackets.

And after that, in accordance with reaction equations (1) and (2), we calculate the amount of nitric acid necessary for processing the intermediate product:

(1) => mi (HNO3) = m (MgCC-h) x [2M (HN03) / M (MgC03)] = 16.9 x 2 x 63 / 100.1 = 25.3 kg

(2) => m2 (HN03) = m (CaCO3) x [2M (Oz) / M (CaCO3)] = 5.4 x 2 x 63 / 100.1 = 6.80 kg, where: m is the mass of the substance indicated in parentheses.

M is the molar mass of the substance indicated in parentheses.

The molar masses of substances are taken on the website www.xumuk.ru or in chemical directories.

The total amount of nitric acid will be equal to: m (HN03) = mi (HN03) + g (HNO3) = 25.3 kg + 6.80 kg = 32.1 kg The total mass of a solution of nitric acid of 20% concentration will be equal to:

25, 3 kg x 100% / 20% = 126.5 kg

In accordance with the above calculations, 126.5 ~ 127 kg of a 20% aqueous nitric acid solution is prepared.

The acid solution is poured into an autoclave with a propeller stirrer; while mixing the solution, calcined siderite is poured into it in small portions.

Chemical reactions (1) and (2) begin already at room temperature.

The autoclave is turned on and heated to a temperature of 100 ^° C at atmospheric pressure for 30-60 minutes. Then the autoclave is sealed and heated for 30-60 minutes to a temperature of 120-160 ^° C. After reaching the required temperature, the contents of the autoclave are isothermally aged for 30 minutes.

At the end of the process, the autoclave is allowed to cool to a temperature of 100-90 ° C, the pulp is poured out of it, which is separated into a solid phase (finished iron ore concentrate) and a solution containing calcium and magnesium nitrates by filtration with washing of the precipitate from salts.

For the separation of calcium and magnesium compounds, as well as the regeneration of nitric acid, the dolomite mineral Ca Mg (CO 3) 2 of the Satka deposit is used.

Initially, dolomite is fired for its decarbonization at a temperature of 1,100-1,200 ° C for 2 hours:

Ca Mg (CO 3) CaO + MgO + 2CO 2 T Next, the calcined dolomite is quenched with water to produce dolomite milk. In this case, calcium oxide is hydrated with the formation of Ca (OH) 2, MgO - is not hydrated. Dolomite milk is prepared in such a way that the ratio of liquid to solid (W: T) is 2.0 ... 2.5: 1.

Cooked dolomite milk is mixed with a solution of calcium and magnesium nitrates. In this case, a chemical reaction occurs:

Mg (N03) 2 + Ca (OH) 2j -> Mg (OH) 2j + Ca (Na2) 2 (3)

This reaction goes from left to right almost to the end, because the solubility product of Mg (OH) 2 is much smaller than the solubility product of Ca (OH) 2.

The process of precipitation of magnesium hydroxide from a solution of salts with dolomite milk is carried out at a temperature of 20-40 ° C for 1-2 hours with continuous stirring of the reaction medium. As a result of chemical reaction (3), magnesium ions from the solution precipitate in the form of Mg (OH) 2, and the calcium contained in dolomite milk goes into solution, replacing magnesium in it. Therefore, at the end of the process, almost all calcium (in the form of nitrate) is in solution, and magnesium (in the form of hydroxide and oxide) is in the precipitate.

The precipitate is separated from the solution with its additional washing from soluble salts, dried and calcined, resulting in a commodity magnesite. W

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A solution containing Ca KOC) 2 is treated with sulfuric acid to regenerate nitric acid. The process proceeds in accordance with the equation of the following chemical reaction: Ca (NaO3) 2 + H2SO4 - »CaSO | + 2HNC-3

Calcium sulfate as a poorly soluble compound precipitates. The precipitate is separated from the solution by filtration with additional washing. After drying, the precipitate is a commercial gypsum, which is also a valuable commercial product for the production of building materials and products.

The solution containing nitric acid is returned to the process for processing a new portion of burnt siderite.

The calculations of the reagents involved in the technical process are based on the following.

In accordance with the law of equivalents, all substances interact with each other in equivalent amounts.

Therefore, the amount of CaO in dolomite spent on the deposition of Mg (OH) 2 from a solution of calcium and magnesium nitrates will be equivalent to the amount of MgO extracted from the calcined siderite with acid. Since the valencies of calcium and magnesium are the same, these amounts will also be equimolar.

Hence, the amount of CaO in dolomite should be equal to: w (CaO) dolomi = m (MgO) x [m (CaO) / m (MgO)] = 8.1 kg x 56.1 / 40.3 = 11.3 kg, Dolomite of the Satka deposit has the following chemical composition, wt.%: MgO - 21.5;

CaO -29.6;

S1O2 - 1, 6;

The rest is CO2 and impurities undetermined by chemical analysis.

. To prepare dolomite milk, you must use the following amount of dolomite:

m dolomite = [w (CaO _D olomite) / 29.6%] x 100% = 1.3 kg x 100% / 29.6% = 38.2 kg.

This amount of dolomite will contain MgO:

m (MgO / dolomite) = 38.2 kg x [21.5% / 100%] = 8.2 kg. When Mg (OH) 2 is precipitated from a solution, this magnesium oxide will attach to it. As a result, we get the amount of sediment in terms of MgO equal to: m (MgOz) = 8.1 kg + 8.2 kg = 16.3 kg.

In solution, we will have the amount of calcium ions in terms of CaO equal to: m (CaOi) = 1 1.3 kg +3.0 kg = 14.3 kg

During the regeneration of nitric acid, the amount of sulfuric acid will be equimolar to the amount of calcium in solution in terms of CaO. Therefore, the amount of sulfuric acid in terms of 100% sulfuric acid H2SO4 for the regeneration of nitric acid will be: m (H2SO4) = m (CaO) x [m (H2S04) / m (CaO)] = 14.3 kg x 98 / 56.1 = 25, 0 kg.

In the process of nitric acid regeneration, we also get calcium sulfate (gypsum) in an amount: m (CaS04) = m (H2SO4) x [m (CaS04) / w (H2SO4)] = 25, 0 kg x 136.2 / 38 = 34, 7 kg

Compared with the prototype, the claimed inventions make it possible to obtain higher-quality iron ore concentrate at lower energy costs in preparing both siderite iron ore for processing, and further processing provides a waste-free technology for producing high-quality basic (iron ore) and high-quality secondary (magnesite concentrate and building gypsum) products.

Claims

O 2012/150873 17 FORMULAS OF THE INVENTION

1. A method of preparing siderite iron ore for processing, namely, that the initial ore is crushed, subjected to screening, and siderite is decarbonized, characterized in that the initial ore is crushed and screened to a particle size of 2.0 - 0 mm, siderite is decarbonized, heating the crushed ore to a temperature of 600-700 ° C and keeping it at this temperature for 60-120 minutes.

2. A method of preparing siderite iron ore for processing, namely, that the initial ore is crushed, screened, and siderite is decarbonized, characterized in that the initial ore is crushed and screened to a particle size of 2.0-0 mm, siderite is decarbonized by heating crushed ore to a temperature of 100-160 ° C, keeping it at this temperature for 60-240 minutes at a pressure of 1.0-10.0 atm, and passing an oxidizing agent through the ore.

3. The method according to claim 2., Characterized in that the oxidation process is carried out in an aqueous medium.

4. The method according to claim 2., Characterized in that the oxidation process is carried out without water.

5. The method according to claim 2, characterized in that oxygen is used as an oxidizing agent.

6. The method according to claim 2, characterized in that chlorine, nitrogen oxides, hydrogen peroxide, and the like are used as an oxidizing agent.

7. A non-waste processing method for siderite iron ore, namely, that the initial siderite ore is prepared for processing, prepared for processing siderite ore is separated into iron ore concentrate and waste rock, ACCORDING TO THE INVENTION, siderite ore is prepared for processing using one of the methods described above, and to separate the prepared ore into iron ore concentrate and waste rock, water is added to it and a pulp is prepared, which is exposed to acid to leach oxides of magne and calcium, then the resulting solution is separated from the precipitate, which is washed and dried to obtain an iron ore concentrate from it, and magnesium hydroxide is precipitated from the solution by adding lime or dolomite milk, which is then dried and calcined to obtain a magnesite concentrate, after which the acid is regenerated, feeding sulfuric acid into the solution, the calcium sulfate emitted at the same time as acid regeneration is washed and dried, obtaining marketable gypsum, and the regenerated acid is reused to leach the pulp.

8. The method according to claim 7., Characterized in that the pulp is exposed to nitric acid.

1 1. The method according to claim 7., Characterized in that the pulp is exposed to hydrochloric acid.