Getting iron in two ways. Ferrous metal: basic characteristics, production and use of iron. The oxidation state of iron in compounds

Iron is the eighth element of the fourth period in the periodic table. Its number in the table (also called atomic) is 26, which corresponds to the number of protons in the nucleus and electrons in the electron shell. It is designated by the first two letters of its Latin equivalent - Fe (Latin Ferrum - read as "ferrum"). Iron is the second most common element in the earth's crust, with a percentage of 4.65% (the most common is aluminum, Al). In its native form, this metal is quite rare; more often it is mined from mixed ore with nickel.

In contact with

What is the nature of this connection? Iron as an atom consists of a metallic crystal lattice, due to which the hardness of the compounds containing this element and molecular stability are ensured. It is in this connection that this metal is a typical solid unlike, for example, mercury.

Iron as a simple substance- a silver-colored metal with properties typical for this group of elements: malleability, metallic luster and ductility. In addition, iron is highly reactive. The latter property is evidenced by the fact that iron corrodes very quickly in the presence of high temperature and appropriate humidity. In pure oxygen, this metal burns well, and if you crumble it into very small particles, then they will not only burn, but ignite spontaneously.

Often we call iron not pure metal, but its alloys containing carbon ©, for example, steel (<2,14% C) и чугун (>2.14% C). Also of great industrial importance are alloys in which alloying metals (nickel, manganese, chromium and others) are added, due to which the steel becomes stainless, i.e. alloyed. Thus, based on this, it becomes clear how extensive industrial application has this metal.

Fe characteristic

Iron chemical properties

Let's take a closer look at the features of this element.

Properties of a simple substance

  • Oxidation in air at high humidity (corrosive process):

4Fe + 3O2 + 6H2O = 4Fe (OH) 3 - iron (III) hydroxide (hydroxide)

  • Combustion of iron wire in oxygen with the formation of a mixed oxide (it contains an element with both an oxidation state of +2 and an oxidation state of +3):

3Fe + 2O2 = Fe3O4 (iron scale). Reaction is possible when heated to 160 ⁰C.

  • Interaction with water at high temperatures (600-700 ⁰C):

3Fe + 4H2O = Fe3O4 + 4H2

  • Reactions with non-metals:

a) Reaction with halogens (Important! In this interaction, it acquires the oxidation state of the element +3)

2Fe + 3Cl2 = 2FeCl3 - ferric chloride

b) Reaction with sulfur (Important! In this interaction, the element has an oxidation state of +2)

Iron (III) sulfide - Fe2S3 can be obtained in the course of another reaction:

Fe2O3 + 3H2S = Fe2S3 + 3H2O

c) Formation of pyrite

Fe + 2S = FeS2 - pyrite. Pay attention to the oxidation state of the elements that make up this compound: Fe (+2), S (-1).

  • Interaction with metal salts, standing in the electrochemical series of metal activities to the right of Fe:

Fe + CuCl2 = FeCl2 + Cu - iron (II) chloride

  • Interaction with dilute acids (for example, hydrochloric and sulfuric):

Fe + HBr = FeBr2 + H2

Fe + HCl = FeCl2 + H2

Note that these reactions produce iron in the +2 oxidation state.

  • In undiluted acids, which are the strongest oxidizing agents, the reaction is possible only when heated; in cold acids, the metal is passivated:

Fe + H2SO4 (concentrated) = Fe2 (SO4) 3 + 3SO2 + 6H2O

Fe + 6HNO3 = Fe (NO3) 3 + 3NO2 + 3H2O

  • The amphoteric properties of iron appear only when interacting with concentrated alkalis:

Fe + 2KOH + 2H2O = K2 + H2 - potassium tetrahydroxyferrate (II) precipitates.

Blast furnace pig iron production process

  • Roasting and subsequent decomposition of sulfide and carbonate ores (release of metal oxides):

FeS2 -> Fe2O3 (O2, 850 ⁰C, -SO2). This reaction is also the first stage in the industrial synthesis of sulfuric acid.

FeCO3 -> Fe2O3 (O2, 550-600 ⁰C, -CO2).

  • Burning coke (in excess):

С (coke) + O2 (air) -> CO2 (600-700 ⁰C)

CO2 + C (coke) -> 2CO (750-1000 ⁰C)

  • Carbon monoxide reduction of ore containing oxide:

Fe2O3 -> Fe3O4 (CO, -CO2)

Fe3O4 -> FeO (CO, -CO2)

FeO -> Fe (CO, -CO2)

  • Iron carburization (up to 6.7%) and cast iron melting (melting temperature - 1145 ⁰C)

Fe (solid) + C (coke) -> cast iron. The reaction temperature is 900-1200 ⁰C.

In cast iron, cementite (Fe2C) and graphite are always present in the form of grains.

Characterization of Fe-containing compounds

Let's study the features of each compound separately.

Fe3O4

Mixed or double iron oxide, which contains an element with an oxidation state of both +2 and +3. Also called Fe3O4 iron oxide... This compound is resistant to high temperatures. Does not react with water, water vapor. Decomposed by mineral acids. It can be reduced with hydrogen or iron at high temperatures. As you could understand from the above information, it is an intermediate product in the reaction chain industrial production cast iron.

Directly the same iron scale is used in the production of paints on a mineral basis, colored cement and ceramics. Fe3O4 is what is obtained by blackening and bluing steel. Mixed oxide is obtained by combustion of iron in air (the reaction is given above). The oxide-bearing ore is magnetite.

Fe2O3

Iron (III) oxide, a trivial name - hematite, the compound is red-brown. Resistant to high temperatures. In its pure form, it is not formed during the oxidation of iron by atmospheric oxygen. Does not react with water, forms hydrates that precipitate. Reacts poorly with dilute alkalis and acids. It can be fused with oxides of other metals, forming spinels - double oxides.

Red iron ore is used as a raw material in the industrial production of pig iron by the blast-furnace method. It also speeds up the reaction, that is, it is a catalyst, in the ammonia industry. It is used in the same areas as iron dross. Plus, it was used as a carrier of sound and pictures on magnetic tapes.

FeOH2

Iron (II) hydroxide, a compound with both acidic and basic properties, the latter predominate, that is, it is amphoteric. Substance white, which quickly oxidizes in air, "turns brown" to iron (III) hydroxide. Liable to decomposition when exposed to temperature. Reacts with both weak acid solutions and alkalis. Insoluble in water. In the reaction, it acts as a reducing agent. It is an intermediate product in the corrosion reaction.

Detection of Fe2 + and Fe3 + ions ("qualitative" reactions)

Recognition of Fe2 + and Fe3 + ions in aqueous solutions is carried out using complex complex compounds- K3, red blood salt, and K4, yellow blood salt, respectively. In both reactions, a saturated blue precipitate with the same quantitative composition but different positions of iron with valence +2 and +3 is formed. This sediment is also often referred to as Prussian Blue or Turnbull Blue.

Ionic reaction

Fe2 ++ K ++ 3-  K + 1Fe + 2

Fe3 ++ K ++ 4-  K + 1Fe + 3

Good reagent for detecting Fe3 + - thiocyanate ion (NCS-)

Fe3 ++ NCS-  3- - these compounds have a bright red ("bloody") color.

This reagent, for example, potassium thiocyanate (formula - KNCS), allows you to determine even a negligible concentration of iron in solutions. So, he is capable of researching tap water determine if the pipes are rusted.

Iron is an element of a side subgroup of the eighth group of the fourth period of the periodic system of chemical elements of D.I. Mendeleev with atomic number 26. It is designated by the symbol Fe (Latin Ferrum). One of the most widespread metals in the earth's crust (second only to aluminum). Medium activity metal, reducing agent.

Major oxidation states - +2, +3

A simple substance iron is a malleable metal of a silvery-white color with a high chemical reactivity: Iron corrodes quickly at high temperatures or high humidity in the air. In pure oxygen, iron burns, and in a finely dispersed state it ignites spontaneously in air.

Chemical properties of a simple substance - iron:

Rusting and burning in oxygen

1) In air, iron is easily oxidized in the presence of moisture (rusting):

4Fe + 3O 2 + 6H 2 O → 4Fe (OH) 3

A hot iron wire burns in oxygen, forming scale - iron oxide (II, III):

3Fe + 2O 2 → Fe 3 O 4

3Fe + 2O 2 → (Fe II Fe 2 III) O 4 (160 ° С)

2) At high temperatures (700-900 ° C), iron reacts with water vapor:

3Fe + 4H 2 O - t ° → Fe 3 O 4 + 4H 2

3) Iron reacts with non-metals when heated:

2Fe + 3Cl 2 → 2FeCl 3 (200 ° С)

Fe + S - t ° → FeS (600 ° С)

Fe + 2S → Fe +2 (S 2 -1) (700 ° С)

4) In a series of voltages, it stands to the left of hydrogen, reacts with dilute acids HCl and H 2 SO 4, while iron (II) salts are formed and hydrogen is released:

Fe + 2HCl → FeCl 2 + H 2 (reactions are carried out without access to air, otherwise Fe +2 is gradually transferred by oxygen to Fe +3)

Fe + H 2 SO 4 (dil.) → FeSO 4 + H 2

In concentrated oxidizing acids, iron dissolves only when heated, it immediately passes into the Fe 3+ cation:

2Fe + 6H 2 SO 4 (conc.) - t ° → Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O

Fe + 6HNO 3 (conc.) - t ° → Fe (NO 3) 3 + 3NO 2 + 3H 2 O

(in the cold, concentrated nitrogen and sulfuric acid passivate

An iron nail, immersed in a bluish solution of copper sulfate, gradually becomes covered with a bloom of red metallic copper.

5) Iron displaces metals, standing to the right of it, from solutions of their salts.

Fe + CuSO 4 → FeSO 4 + Cu

The amphotericity of iron is manifested only in concentrated alkalis during boiling:

Fe + 2NaOH (50%) + 2H 2 O = Na 2 ↓ + H 2

and a precipitate of sodium tetrahydroxoferrate (II) is formed.

Technical iron- alloys of iron with carbon: cast iron contains 2.06-6.67% C, steel 0.02-2.06% C, other natural impurities (S, P, Si) and artificially introduced special additives (Mn, Ni, Cr) are often present, which gives iron alloys technically beneficial features- hardness, thermal and corrosion resistance, ductility, etc. .

Blast furnace pig iron production

The blast furnace process for the production of pig iron consists of the following stages:

a) preparation (roasting) of sulfide and carbonate ores - transfer to oxide ore:

FeS 2 → Fe 2 O 3 (O 2, 800 ° C, -SO 2) FeCO 3 → Fe 2 O 3 (O 2, 500-600 ° C, -CO 2)

b) combustion of coke with hot blast:

С (coke) + O 2 (air) → СO 2 (600-700 ° С) СO 2 + С (coke) ⇌ 2СО (700-1000 ° С)

c) reduction of oxide ore with carbon monoxide CO sequentially:

Fe 2 O 3 → (CO)(Fe II Fe 2 III) O 4 → (CO) FeO → (CO) Fe

d) carburization of iron (up to 6.67% C) and melting of cast iron:

Fe (t ) →(C(coke)900-1200 ° C) Fe (w) (cast iron, melting point 1145 ° C)

In cast iron, cementite Fe 2 C and graphite are always present in the form of grains.

Steel production

The conversion of cast iron into steel is carried out in special furnaces (converter, open-hearth, electric), which differ in the way of heating; process temperature 1700-2000 ° C. Blowing oxygen-enriched air leads to the burnout of excess carbon from the cast iron, as well as sulfur, phosphorus and silicon in the form of oxides. In this case, oxides are either captured in the form of waste gases (CO 2, SO 2), or are bound into an easily separated slag - a mixture of Ca 3 (PO 4) 2 and CaSiO 3. To obtain special steels, alloying additives of other metals are introduced into the furnace.

Receiving pure iron in industry - electrolysis of a solution of iron salts, for example:

FeСl 2 → Fe ↓ + Сl 2 (90 ° С) (electrolysis)

(there are other special methods, including the reduction of iron oxides with hydrogen).

Pure iron is used in the production of special alloys, in the manufacture of the cores of electromagnets and transformers, cast iron - in the production of castings and steel, steel - as structural and tool materials, including wear-, heat- and corrosion-resistant.

Iron (II) oxide F eO ... Amphoteric oxide with a large predominance of basic properties. Black, has an ionic structure Fe 2+ O 2-. When heated, it first decomposes, then forms again. It is not formed when iron is burned in air. Does not react with water. Decomposed by acids, fused with alkalis. Oxidizes slowly in humid air. Reduced with hydrogen, coke. Participates in the blast furnace process of iron smelting. It is used as a component of ceramics and mineral paints. Equations of the most important reactions:

4FеО ⇌ (Fe II Fe 2 III) + Fe (560-700 ° С, 900-1000 ° С)

FeO + 2HC1 (dil.) = FeC1 2 + H 2 O

FeO + 4HNO 3 (conc.) = Fe (NO 3) 3 + NO 2 + 2H 2 O

FеО + 4NаОН = 2Н 2 O + Na 4FeO3 (red.) trioxoferrate (II)(400-500 ° C)

FeO + H 2 = H 2 O + Fe (extra pure) (350 ° C)

FeO + C (coke) = Fe + CO (above 1000 ° C)

FeO + CO = Fe + CO 2 (900 ° C)

4FеО + 2Н 2 O (moisture) + O 2 (air) → 4FеО (ОН) (t)

6FеО + O 2 = 2 (Fe II Fe 2 III) O 4 (300-500 ° С)

Receiving v laboratories: thermal decomposition of iron (II) compounds without air access:

Fe (OH) 2 = FeO + H 2 O (150-200 ° C)

FeCO3 = FeO + CO 2 (490-550 ° C)

Diiron (III) oxide - iron ( II ) ( Fe II Fe 2 III) O 4 ... Double oxide. Black, has an ionic structure Fe 2+ (Fe 3+) 2 (O 2-) 4. Thermally stable up to high temperatures. Does not react with water. Decomposed by acids. Reduced with hydrogen, hot iron. Participates in the blast furnace process of pig iron production. It is used as a component of mineral paints ( iron lead), ceramics, colored cement. Product of special oxidation of the surface of steel products ( blackening, bluing). The composition corresponds to brown rust and dark scale on iron. The use of the gross formula Fe 3 O 4 is not recommended. Equations of the most important reactions:

2 (Fe II Fe 2 III) O 4 = 6FеO + O 2 (above 1538 ° C)

(Fe II Fe 2 III) O 4 + 8HC1 (dil.) = FeC1 2 + 2FeC1 3 + 4H 2 O

(Fe II Fe 2 III) O 4 + 10НNO 3 (conc.) = 3Fе (NO 3) 3 + NO 2 + 5Н 2 O

(Fe II Fe 2 III) O 4 + O 2 (air) = 6Fе 2 O 3 (450-600 ° C)

(Fe II Fe 2 III) O 4 + 4H 2 = 4H 2 O + 3Fе (extra pure, 1000 ° C)

(Fe II Fe 2 III) O 4 + CO = ZFeO + CO 2 (500-800 ° C)

(Fe II Fe 2 III) O4 + Fe ⇌4FеО (900-1000 ° С, 560-700 ° С)

Receiving: combustion of iron (see) in air.

magnetite.

Iron (III) oxide F e 2 O 3 ... Amphoteric oxide with a predominance of basic properties. Red-brown, has an ionic structure (Fe 3+) 2 (O 2-) 3. Thermally stable up to high temperatures. It is not formed when iron is burned in air. Does not react with water, brown amorphous hydrate Fe 2 O 3 nH 2 O falls out of solution. Reacts slowly with acids and alkalis. Reduced with carbon monoxide, molten iron. Alloys with oxides of other metals and forms double oxides - spinels(technical products are called ferrites). It is used as a raw material in the smelting of pig iron in the blast-furnace process, as a catalyst in the production of ammonia, a component of ceramics, non-ferrous cements and mineral paints, in thermite welding of steel structures, as a carrier of sound and images on magnetic tapes, as a polishing agent for steel and glass.

Equations of the most important reactions:

6Fе 2 O 3 = 4 (Fe II Fe 2 III) O 4 + O 2 (1200-1300 ° C)

Fe 2 O 3 + 6HC1 (dil.) → 2FeC1 3 + ЗН 2 O (t) (600 ° C, p)

Fe 2 O 3 + 2NaOH (conc.) → H 2 O + 2 NaFeO 2 (red)dioxoferrate (III)

Fe 2 O 3 + MO = (M II Fe 2 II I) O 4 (M = Cu, Mn, Fe, Ni, Zn)

Fe 2 O 3 + ZN 2 = ZN 2 O + 2Fе (extra pure, 1050-1100 ° C)

Fe 2 O 3 + Fe = ZFeO (900 ° C)

3Fе 2 O 3 + CO = 2 (Fe II Fe 2 III) O 4 + CO 2 (400-600 ° C)

Receiving in the laboratory - thermal decomposition of iron (III) salts in air:

Fe 2 (SO 4) 3 = Fe 2 O 3 + 3SO 3 (500-700 ° C)

4 (Fe (NO 3) 3 9 Н 2 O) = 2Fе a O 3 + 12NO 2 + 3O 2 + 36Н 2 O (600-700 ° С)

In nature - iron oxide ores hematite Fe 2 O 3 and limonite Fe 2 O 3 nН 2 O

Iron (II) hydroxide F e (OH) 2. Amphoteric hydroxide with a predominance of basic properties. White (sometimes with a greenish tint), Fe - OH bonds are predominantly covalent. Thermally unstable. Readily oxidizes in air, especially when wet (darkens). Insoluble in water. Reacts with dilute acids, concentrated alkalis. Typical reducing agent. Intermediate in iron rusting. It is used in the manufacture of active mass of iron-nickel batteries.

Equations of the most important reactions:

Fe (OH) 2 = FeO + H 2 O (150-200 ° C, in atm N 2)

Fe (OH) 2 + 2HC1 (dil.) = FeC1 2 + 2H 2 O

Fe (OH) 2 + 2NаОН (> 50%) = Na 2 ↓ (blue-green) (boiling)

4Fе (ОН) 2 (suspension) + O 2 (air) → 4FеО (ОН) ↓ + 2Н 2 O (t)

2Fе (ОН) 2 (suspension) + Н 2 O 2 (dil.) = 2FеО (ОН) ↓ + 2Н 2 O

Fe (OH) 2 + KNO 3 (conc.) = FeO (OH) ↓ + NO + KOH (60 ° C)

Receiving: precipitation from solution with alkalis or ammonia hydrate in an inert atmosphere:

Fe 2+ + 2OH (expanded) = Fe (OH) 2 ↓

Fe 2+ + 2 (NH 3 H 2 O) = Fe (OH) 2 ↓+ 2NH 4

Iron metahydroxide F eO (OH). Amphoteric hydroxide with a predominance of basic properties. Light brown, Fe - O and Fe - OH bonds are predominantly covalent. Decomposes when heated without melting. Insoluble in water. It precipitates from solution in the form of amorphous brown polyhydrate Fe 2 O 3 nH 2 O, which, when kept under a dilute alkaline solution or upon drying, transforms into FeO (OH). Reacts with acids, solid alkalis. Weak oxidizing and reducing agent. Sintered with Fe (OH) 2. Intermediate in iron rusting. It is used as a base for yellow mineral paints and enamels, an exhaust gas absorber, a catalyst in organic synthesis.

The compound of the composition Fe (OH) 3 is not known (not obtained).

Equations of the most important reactions:

Fe 2 O 3. nН 2 O → ( 200-250 ° C, -H 2 O) FeO (OH) → ( 560-700 ° C in air, -H2O)→ Fe 2 O 3

FeO (OH) + ZNS1 (dil.) = FeC1 3 + 2H 2 O

FeO (OH) → Fe 2 O 3 . nH 2 O-colloid(NaOH (conc.))

FeO (OH) → Na 3 [Fe (OH) 6]White, Na 5 and K 4, respectively; in both cases, a blue product of the same composition and structure, КFе III, is precipitated. In the laboratory, this sediment is called Prussian blue, or turnbull's blue:

Fe 2+ + K + + 3- = KFe III ↓

Fe 3+ + K + + 4- = KFe III ↓

Chemical names of the starting reagents and the reaction product:

K 3 Fe III - potassium hexacyanoferrate (III)

K 4 Fe III - potassium hexacyanoferrate (II)

КFе III - iron (III) potassium hexacyanoferrate (II)

In addition, a good reagent for Fe 3+ ions is the thiocyanate ion NСS -, iron (III) combines with it, and a bright red ("bloody") color appears:

Fe 3+ + 6NСS - = 3-

This reagent (for example, in the form of a KNCS salt) can even detect traces of iron (III) in tap water if it passes through iron pipes covered with rust on the inside.

  • Designation - Fe (Iron);
  • Period - IV;
  • Group - 8 (VIII);
  • Atomic mass - 55.845;
  • Atomic number - 26;
  • Atom radius = 126 pm;
  • Covalent radius = 117 pm;
  • Distribution of electrons - 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2;
  • melting point = 1535 ° C;
  • boiling point = 2750 ° C;
  • Electronegativity (Pauling / Alpred and Rohov) = 1.83 / 1.64;
  • Oxidation state: +8, +6, +4, +3, +2, +1, 0;
  • Density (n. At.) = 7.874 g / cm 3;
  • Molar volume = 7.1 cm 3 / mol.

Iron compounds:

Iron is the most abundant metal in the earth's crust (5.1% by mass) after aluminum.

On Earth, iron in a free state is found in small quantities in the form of nuggets, as well as in fallen meteorites.

Iron is mined industrially at iron ore deposits, from iron-containing minerals: magnetic, red, brown iron ore.

It should be said that iron is a part of many natural minerals, causing their natural color. The color of minerals depends on the concentration and ratio of iron ions Fe 2+ / Fe 3+, as well as on the atoms surrounding these ions. For example, the presence of impurities of iron ions affects the color of many precious and semi-precious stones: topaz (from pale yellow to red), sapphires (from blue to dark blue), aquamarines (from light blue to greenish blue), etc.

Iron is found in the tissues of animals and plants, for example, in the body of an adult there is about 5 g of iron. Iron is a vital element, it is part of the protein hemoglobin, participating in the transport of oxygen from the lungs to tissues and cells. With a lack of iron in the human body, anemia develops (iron deficiency anemia).


Rice. The structure of the iron atom.

The electronic configuration of the iron atom is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2 (see Electronic structure of atoms). In education chemical bonds 2 electrons located on the outer 4s-level + 6 electrons of the 3d-sublevel (8 electrons in total) can participate with other elements, therefore, in compounds, iron can take the oxidation states +8, +6, +4, +3, +2, + 1, (the most common are +3, +2). Iron has an average chemical activity.


Rice. Iron oxidation states: +2, +3.

Physical properties of iron:

  • silver-white metal;
  • in its pure form, it is quite soft and plastic;
  • possesses good heat and electrical conductivity.

Iron exists in the form of four modifications (differ in the structure of the crystal lattice): α-iron; β-iron; γ-iron; δ-iron.

Iron chemical properties

  • reacts with oxygen, depending on the temperature and oxygen concentration, various products or a mixture of iron oxidation products (FeO, Fe 2 O 3, Fe 3 O 4) can be formed:
    3Fe + 2O 2 = Fe 3 O 4;
  • iron oxidation at low temperatures:
    4Fe + 3O 2 = 2Fe 2 O 3;
  • reacts with water vapor:
    3Fe + 4H 2 O = Fe 3 O 4 + 4H 2;
  • finely crushed iron reacts when heated with sulfur and chlorine (ferrous sulfide and chloride):
    Fe + S = FeS; 2Fe + 3Cl 2 = 2FeCl 3;
  • at high temperatures reacts with silicon, carbon, phosphorus:
    3Fe + C = Fe 3 C;
  • with other metals and with non-metals, iron can form alloys;
  • iron displaces less active metals from their salts:
    Fe + CuCl 2 = FeCl 2 + Cu;
  • with dilute acids, iron acts as a reducing agent, forming salts:
    Fe + 2HCl = FeCl 2 + H 2;
  • with dilute nitric acid, iron forms various acid reduction products, depending on its concentration (N 2, N 2 O, NO 2).

Getting and using iron

Industrial iron is obtained smelting cast iron and steel.

Cast iron is an alloy of iron with admixtures of silicon, manganese, sulfur, phosphorus, carbon. The carbon content in cast iron exceeds 2% (in steel less than 2%).

Pure iron is obtained:

  • in oxygen converters made of cast iron;
  • reduction of iron oxides with hydrogen and bivalent carbon monoxide;
  • electrolysis of the corresponding salts.

Pig iron is obtained from iron ores by reduction of iron oxides. Pig iron is smelted in blast furnaces. The blast furnace uses coke as a heat source.

A blast furnace is a very complex technical structure with a height of several tens of meters. It is lined with refractory bricks and protected by an outer steel casing. As of 2013, the largest blast furnace was built in South Korea steel company POSCO at a metallurgical plant in the city of Gwangyang (the volume of the furnace after modernization was 6,000 cubic meters with an annual capacity of 5,700,000 tons).


Rice. Blast furnace.

The process of smelting pig iron in a blast furnace goes on continuously for several decades until the furnace reaches its end of life.


Rice. The process of smelting pig iron in a blast furnace.

  • beneficiated ores (magnetic, red, brown iron ore) and coke are poured through the top, located at the very top of the blast furnace;
  • the processes of iron reduction from ore under the influence of carbon monoxide (II) occur in the middle part of a blast furnace (mine) at a temperature of 450-1100 ° C (iron oxides are reduced to metal):
    • 450-500 ° C - 3Fe 2 O 3 + CO = 2Fe 3 O 4 + CO 2;
    • 600 ° C - Fe 3 O 4 + CO = 3FeO + CO 2;
    • 800 ° C - FeO + CO = Fe + CO 2;
    • part of the bivalent iron oxide is reduced by coke: FeO + C = Fe + CO.
  • in parallel, there is a process of reduction of silicon and manganese oxides (included in iron ore in the form of impurities), silicon and manganese are part of the cast iron:
    • SiO 2 + 2C = Si + 2CO;
    • Mn 2 O 3 + 3C = 2Mn + 3CO.
  • during thermal decomposition of limestone (introduced into a blast furnace), calcium oxide is formed, which reacts with silicon and aluminum oxides contained in the ore:
    • CaCO 3 = CaO + CO 2;
    • CaO + SiO 2 = CaSiO 3;
    • CaO + Al 2 O 3 = Ca (AlO 2) 2.
  • at 1100 ° C, the iron reduction process stops;
  • below the shaft is the steaming, the widest part of the blast furnace, below which follows a shoulder, in which the coke burns out and liquid products of smelting are formed - pig iron and slag, accumulating at the very bottom of the furnace - the hearth;
  • in the upper part of the hearth at a temperature of 1500 ° C in a stream of blown air, intensive combustion of coke occurs: C + O 2 = CO 2;
  • passing through the red-hot coke, carbon monoxide (IV) is converted into carbon monoxide (II), which is a reducing agent for iron (see above): CO 2 + C = 2CO;
  • slags formed by calcium silicates and aluminosilicates are located above the cast iron, protecting it from the action of oxygen;
  • through special holes located at different levels of the hearth, cast iron and slag are discharged outside;
  • Most of the pig iron goes for further processing - steel smelting.

Steel is smelted from cast iron and scrap metal by the converter method (open-hearth is already obsolete, although it is still used) or by electric melting (in electric furnaces, induction furnaces). The essence of the process (redistribution of cast iron) is to reduce the concentration of carbon and other impurities by oxidation with oxygen.

As mentioned above, the carbon concentration in steel does not exceed 2%. Due to this, steel, in contrast to cast iron, is quite easily forged and rolled, which makes it possible to manufacture various products from it with high hardness and strength.

The hardness of steel depends on the carbon content (the more carbon, the harder the steel) in a particular steel grade and heat treatment conditions. When tempered (slow cooling), the steel becomes soft; when quenched (quickly cooled), the steel is very hard.

To give the steel the desired specific properties, ligating additives are added to it: chromium, nickel, silicon, molybdenum, vanadium, manganese, etc.

Cast iron and steel are the most important structural materials in the overwhelming majority of sectors of the national economy.

The biological role of iron:

  • the body of an adult contains about 5 g of iron;
  • iron plays an important role in the work of the hematopoietic organs;
  • iron is a part of many complex protein complexes (hemoglobin, myoglobin, various enzymes).

Iron (II) compounds

Iron compounds with iron oxidation state +2 are unstable and easily oxidized to iron (III) derivatives.

Fe 2 O 3 + CO = 2FeO + CO 2.

Iron (II) hydroxide Fe (OH) 2 freshly precipitated has a grayish-green color, does not dissolve in water, decomposes at temperatures above 150 ° C, quickly darkens due to oxidation:

4Fe (OH) 2 + O 2 + 2H 2 O = 4Fe (OH) 3.

Shows mild amphoteric properties with a predominance of basic ones, easily reacts with non-oxidizing acids:

Fe (OH) 2 + 2HCl = FeCl 2 + 2H 2 O.

Interacts with concentrated alkali solutions when heated to form tetrahydroxoferrate (II):

Fe (OH) 2 + 2NaOH = Na 2.

Shows reducing properties, when interacting with nitric or concentrated sulfuric acid, iron (III) salts are formed:

2Fe (OH) 2 + 4H 2 SO 4 = Fe 2 (SO 4) 3 + SO 2 + 6H 2 O.

It is obtained by the interaction of iron (II) salts with an alkali solution in the absence of atmospheric oxygen:

FeSO 4 + 2NaOH = Fe (OH) 2 + Na 2 SO 4.

Iron (II) salts. Iron (II) forms salts with almost all anions. Usually salts crystallize in the form of green crystalline hydrates: Fe (NO 3) 2 6H 2 O, FeSO 4 7H 2 O, FeBr 2 6H 2 O, (NH 4) 2 Fe (SO 4) 2 6H 2 O (salt Mora), etc. Salt solutions have a pale green color and, due to hydrolysis, an acidic environment:

Fe 2+ + H 2 O = FeOH + + H +.

Show all the properties of salts.

When standing in air, they are slowly oxidized by dissolved oxygen to iron (III) salts:

4FeCl 2 + O 2 + 2H 2 O = 4FeOHCl 2.

Qualitative reaction for cation Fe 2+ - interaction with potassium hexacyanoferrate (III) (red blood salt):

FeSO 4 + K 3 = KFe ↓ + K 2 SO 4

Fe 2+ + K + + 3- = KFe ↓

as a result of the reaction, a blue precipitate is formed - iron (III) - potassium hexacyanoferrate (II).

The oxidation state +3 is typical for iron.

Iron (III) oxide Fe 2 O 3 - brown substance, exists in three polymorphic modifications.


Shows mild amphoteric properties with a predominance of the main ones. Reacts easily with acids:

Fe 2 O 3 + 6HCl = 2FeCl 3 + 3H 2 O.

It does not react with alkali solutions, but upon fusion it forms ferrites:

Fe 2 O 3 + 2NaOH = 2NaFeO 2 + H 2 O.

Shows oxidizing and reducing properties. When heated, it is reduced with hydrogen or carbon monoxide (II), exhibiting oxidizing properties:

Fe 2 O 3 + H 2 = 2FeO + H 2 O,

Fe 2 O 3 + CO = 2FeO + CO 2.

In the presence of strong oxidants in alkaline environment exhibits reducing properties and is oxidized to iron (VI) derivatives:

Fe 2 O 3 + 3KNO 3 + 4KOH = 2K 2 FeO 4 + 3KNO 2 + 2H 2 O.

At temperatures above 1400 ° C, decomposes:

6Fe 2 O 3 = 4Fe 3 O 4 + O 2.

It is obtained by thermal decomposition of iron (III) hydroxide:

2Fe (OH) 3 = Fe 2 O 3 + 3H 2 O

or by oxidation of pyrite:

4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2.

FeCl 3 + 3KCNS = Fe (CNS) 3 + 3KCl,

It is one of the most abundant elements in the earth's crust.

Physical properties of iron.

Iron- malleable metal of silvery-white color with high chemical resistance. It tolerates high temperatures and humidity well. Quickly fades (rusts) in air and water. Very flexible, good for forging and rolling. Possesses good thermal and electrical conductivity, excellent ferromagnet.

Chemical properties of iron.

Iron transition metal. It can have an oxidation state of +2 and +3. Reacts with steam:

3 Fe + 4 H 2 O = Fe 3 O 4 + 4 H 2 .

But in the presence of moisture, iron rusts:

4 Fe + 3 O 2 + 6 H 2 O = 4 Fe(OH) 3 .

2 Fe + 3 Cl 2 = 2 FeCl 3 .

Fe + H 2 SO 4 = FeSO 4 + H 2 .

Concentrated acids passivate iron in the cold, but dissolve when heated:

2Fe + 6H 2 SO 4 = Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O.

Iron hydroxide (II) is obtained by the action of alkali on iron (II) salts without oxygen access:

F 2 SO 4 + 2NaOH = Fe (OH) 2 + Na 2 SO 4.

A white precipitate is formed, which quickly oxidizes in air:

4Fe (OH) 2 + O 2 + 2H 2 O = 4Fe (OH) 3.

This hydroxide is amphoteric; when heated, it dissolves in alkalis to form hexahydroferate:

Fe (OH) 3 + 3KOH = K 3.

Iron forms two complex iron salts:

  • Yellow blood salt K 4 [ Fe(CN) 6 ];
  • Red blood salt K 3 [ Fe(CN) 6 ].

These compounds are qualitative for the determination of iron ions. Compound Prussian blue:

K 4 + Fe 2+ = KFe III + 2K +.

The use of iron.

Iron is an essential component of the respiration process. It is part of the hemoglobin of the blood, is involved in the transfer of oxygen from the lungs to the tissues. In nature, iron is found in ores and minerals.



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