**1. Introduction**

Iron ores are very important not only in the production of pig iron in blast furnace, but it also in the production of sinter. These are mainly fine-grained iron ores and concentrates. The sinter is a basic input material for the production of pig iron in the blast furnace and plays an important role in the integrated metallurgical cycle. It is produced by high-temperature sintering of fine iron ore, iron ore concentrates and other ferriferous materials (e.g. secondary materials from iron and steel production). The main criterion of the sintering process is the quality produced sinter while maintaining the ecological nature of the production.

#### **1.1 Characteristics of iron ores and concentrates used to produce sinter**

#### *1.1.1 Physical, chemical, mineralogical and metallurgical properties*

Iron ore is very important for iron and steel industries. It is therefore elementary for the production of pig iron in blast furnace. Almost all (98%) iron ore is used in

steelmaking. Iron ore is mined in about 55 countries. The five largest countries together produce about three quarters of world production, **Figure 1** [1]. Australia and Brazil dominate the world's iron ore production. Iron ores are classified according to the nature of the ore mineral and according to the nature of the gangue [1].

very difficult to reduce iron ore. Oxidation of magnetite creates varieties of hematite-martite and semimartite (according to the degree of oxidation). Most of the world's production of pig iron - 90%, is produced from iron ores of an oxidic

**Figure 2** shows some known iron ores from world. The samples come from the Atlas of iron ores, which was created at the VUHŽ Dobrá (Czech republic) research institute [3] and with which the authors of this chapter have collaborated in the past. The evaluation of the properties of iron ores shows that the best ores are from Brazil, Australia and Venezuela, **Table 2** [3]. They have a suitable particle size distribution, excellent chemical and mineralogical composition, they are well reducible and stable after temperature tests. The optimal piece size of raw iron ore for blast furnaces is 10–40 mm and it is necessary to completely exclude dust fractions below 5 mm. Kryvyi Rih ore has an unsatisfactory chemical composition - low Fe content and high SiO2 content, which is unsuitable for the blast furnace process. On the other hand, this ore has good physical properties (eg. strength and stability) and metallurgical properties (reducibility and plasticity). Ore Algeria has a high proportion of large grains (above 40 mm) and lower strength, reducibility is average and plasticity is unsuitable (high temperature range). Indian ore has worse metallurgical properties - lower reducibility and higher plasticity temperature range. The softening onset temperature and the softening interval characterize the plasticity and also affect the position and height of the plastic zone in the blast furnace. The course of softening depends on the type of ore and cannot be influenced. The blast furnace charge should

nature, of which 5% from magnetite ores and 85% from hematite ores.

*Advances in Sintering of Iron Ores and Concentrates DOI: http://dx.doi.org/10.5772/intechopen.94051*

therefore contain a minimum number of different iron ore raw materials.

*Iron ores (the photographs were created from atlas of ores [3] by the authors of this chapter).*

**Figure 2.**

**57**

with the required granulometry, composition and properties. The following

Sinter grade ores and concentrates are characterized as iron ore raw materials

From a chemical point of view, iron ores are divided into groups: anhydrous oxides, hydrated oxides, carbonates and silicates. **Table 1** shows the classification of iron ores according to the type of ore mineral [2]. In practice, given this principle, only a few iron ore minerals out of a total of more than 300 types are considered. They are mainly oxide minerals, such as magnetite - Fe3O4 (72.36% Fe), hematite or martite (pseudomorphism of hematite after magnetite) - Fe2O3 (69.94% Fe), limonite - (62.85% Fe) (mixture of hydrated oxides Fe, mainly goethite with lepidocrocite Fe2O3.nH2O, often with absorbed elements of vanadium, manganese, etc.). Carbonate ores based on siderite - FeCO3 (48.30% Fe) can also be processed, as well as silicate ores (leptochlorites), e.g. chamosite. The highest natural iron content is in magnetite iron ores. Hematite ores are easily reducible. Chamosite is a

#### **Figure 1.**

*Global production of usable iron ore (thousand metric tons) in 2019 [1].*


#### **Table 1.** *Classification of iron ores [2].*

**56**

### *Advances in Sintering of Iron Ores and Concentrates DOI: http://dx.doi.org/10.5772/intechopen.94051*

steelmaking. Iron ore is mined in about 55 countries. The five largest countries together produce about three quarters of world production, **Figure 1** [1]. Australia and Brazil dominate the world's iron ore production. Iron ores are classified according to the nature of the ore mineral and according to the nature

From a chemical point of view, iron ores are divided into groups: anhydrous oxides, hydrated oxides, carbonates and silicates. **Table 1** shows the classification of iron ores according to the type of ore mineral [2]. In practice, given this principle, only a few iron ore minerals out of a total of more than 300 types are considered. They are mainly oxide minerals, such as magnetite - Fe3O4 (72.36% Fe), hematite or martite (pseudomorphism of hematite after magnetite) - Fe2O3 (69.94% Fe), limonite - (62.85% Fe) (mixture of hydrated oxides Fe, mainly goethite with lepidocrocite Fe2O3.nH2O, often with absorbed elements of vanadium, manganese, etc.). Carbonate ores based on siderite - FeCO3 (48.30% Fe) can also be processed, as well as silicate ores (leptochlorites), e.g. chamosite. The highest natural iron content is in magnetite iron ores. Hematite ores are easily reducible. Chamosite is a

of the gangue [1].

*Iron Ores*

**Figure 1.**

**Table 1.**

**56**

*Classification of iron ores [2].*

**A group of iron ores**

*Global production of usable iron ore (thousand metric tons) in 2019 [1].*

Magnetite ore Magnetite Fe3O4 Dark

Martite ore Hematite Fe2O3 Dadrk

Goethite Lepidocrocite

Chamosite ore Chamosite Fe4Al

Limonite ore Hydrohematite

**Mineral Chemical**

**formula**

Semimartite ore Magnetite Fe3O4 Black 5.1–5.2 —

Hematite ore Hematite Fe2O3 Red 5.26 70.0

Siderite ore Siderite FeCO3 Gray 3.9 48.3

(Si3AlO10). (OH)6.nH2O

Fe2O3.nH2O Dark red

**Color Density (g.cm<sup>3</sup> )**

gray

red

Light red Dark brown

Green Black

**Fe content in pure state (wt.%)**

5.17 72.4

— 70.0

3.1–4.4 63.0–69.0

3.03–3.19 38.0

very difficult to reduce iron ore. Oxidation of magnetite creates varieties of hematite-martite and semimartite (according to the degree of oxidation). Most of the world's production of pig iron - 90%, is produced from iron ores of an oxidic nature, of which 5% from magnetite ores and 85% from hematite ores.

**Figure 2** shows some known iron ores from world. The samples come from the Atlas of iron ores, which was created at the VUHŽ Dobrá (Czech republic) research institute [3] and with which the authors of this chapter have collaborated in the past.

The evaluation of the properties of iron ores shows that the best ores are from Brazil, Australia and Venezuela, **Table 2** [3]. They have a suitable particle size distribution, excellent chemical and mineralogical composition, they are well reducible and stable after temperature tests. The optimal piece size of raw iron ore for blast furnaces is 10–40 mm and it is necessary to completely exclude dust fractions below 5 mm. Kryvyi Rih ore has an unsatisfactory chemical composition - low Fe content and high SiO2 content, which is unsuitable for the blast furnace process. On the other hand, this ore has good physical properties (eg. strength and stability) and metallurgical properties (reducibility and plasticity). Ore Algeria has a high proportion of large grains (above 40 mm) and lower strength, reducibility is average and plasticity is unsuitable (high temperature range). Indian ore has worse metallurgical properties - lower reducibility and higher plasticity temperature range. The softening onset temperature and the softening interval characterize the plasticity and also affect the position and height of the plastic zone in the blast furnace. The course of softening depends on the type of ore and cannot be influenced. The blast furnace charge should therefore contain a minimum number of different iron ore raw materials.

Sinter grade ores and concentrates are characterized as iron ore raw materials with the required granulometry, composition and properties. The following

**Figure 2.** *Iron ores (the photographs were created from atlas of ores [3] by the authors of this chapter).*


**Tables 3, 4** provide a basic chemical analysis of some, also used in Slovakia, sinter

to 100% portion of the size fraction below 0.15 mm, from which 75% of the size

**Table 5** shows the chemical composition of iron-bearing raw materials, where the difference in the richness of ores can be seen. **Figure 4** shows the structure of the samples and Energy Dispersive X-Ray Analysis (EDX), **Table 6**. The larger

**Iron ore Fe Mn SiO2 Al2O3 CaO MgO P S Na2O K2O Zn H2O**

Krivbas 64.04 0.02 6.24 0.68 0.05 0.05 0.035 0.014 0.183 0.046 0.002 3.9 Sucha Balka 59.86 0.02 12.10 0.77 0.06 0.14 0.026 0.011 0.148 0.043 0.004 3.8 Zaporozska 62.70 0.06 7.38 0.84 0.52 0.23 0.023 0.020 0.055 0.027 0.004 4.6 Brazil MBR 65.00 0.08 3.50 0.90 0.08 0.06 0.042 0.005 0.005 0.008 0.003 7.4

Liberia 64.50 0.16 6.73 0.96 0.10 0.05 0.047 0.004 0.013 0.015 0.003 7.5 CIL Trinidad 67.57 0.01 1.48 0.47 0.70 0.52 0.001 0.003 0.001 0.001 0.001 4.0 Hope Downs 64.79 0.02 1.36 0.77 0.03 0.07 0.057 0.007 0.016 0.001 0.006 5.5

Central MBC 64.90 0.032 8.49 0.31 0.19 0.35 0.015 0.073 0.038 0.042 0.003 9.3

Kovdor MBC 64.74 0.430 0.42 1.78 0.23 5.49 0.038 0.269 0.026 0.032 0.034 2.7

Venezuela 69.65 0.056 0.97 0.78 0.24 0.13 0.075 0.020 0.011 0.022 0.005 7.0

**(wt.%)**

65.66 0.31 1.16 0.89 0.10 0.05 0.074 0.014 0.013 0.024 0.003 6.8

**Fe Mn SiO2 Al2O3 CaO MgO P S Na2O K2O Zn H2O (wt.%)**

67.50 0.023 5.90 0.15 0.12 0.35 0.010 0.027 0.059 0.014 0.003 10.2

66.36 0.041 6.78 0.18 0.21 0.44 0.014 0.035 0.045 0.049 0.003 8.8

65.68 0.027 7.28 0.25 0.23 0.29 0.013 0.066 0.032 0.042 0.003 9.4

67.79 0.025 4.92 0.14 0.16 0.33 0.011 0.044 0.062 0.035 0.002 9.5

70.78 0.050 0.61 0.25 0.16 0.33 0.021 0.008 0.041 0.045 0.003 2.7

The authors of this chapter used in their research mainly such iron-bearing raw materials as sinter grade ores supplied from Kryvyi Rih and Brazil and concentrates from Michailovsky and Inguletsky MBCs (Mining-Benefeciation Combines), **Figure 3**. The grain size of the sinter grade ores is 90% below 10 mm, the grain size of the iron concentrates is 90% below 0.04 mm. Iron ores and concentrates before sintering are pretreated in the granulation process. The values of specific surface of

.g<sup>1</sup>

, which corresponds

grade ores and concentrates for the production of sinter [4].

*Advances in Sintering of Iron Ores and Concentrates DOI: http://dx.doi.org/10.5772/intechopen.94051*

the granulated materials should not be lower than 2000 cm2

*Chemical analysis of selected sinter grade ores in the delivered state [4].*

*Chemical analysis of selected iron ore concentrates, as delivered [4].*

fraction below 0.04 mm.

CVG-Venezuela

**Table 3.**

**Iron concentrate**

Southern MBC

Stoilensky MBC

Inguletsky MBC

Lebedinsky MBC

LKAB magnetic fines

**Table 4.**

**59**

#### **Table 2.**

*Properties of iron ores (according [3]).*

### *Advances in Sintering of Iron Ores and Concentrates DOI: http://dx.doi.org/10.5772/intechopen.94051*

**Tables 3, 4** provide a basic chemical analysis of some, also used in Slovakia, sinter grade ores and concentrates for the production of sinter [4].

The authors of this chapter used in their research mainly such iron-bearing raw materials as sinter grade ores supplied from Kryvyi Rih and Brazil and concentrates from Michailovsky and Inguletsky MBCs (Mining-Benefeciation Combines), **Figure 3**. The grain size of the sinter grade ores is 90% below 10 mm, the grain size of the iron concentrates is 90% below 0.04 mm. Iron ores and concentrates before sintering are pretreated in the granulation process. The values of specific surface of the granulated materials should not be lower than 2000 cm2 .g<sup>1</sup> , which corresponds to 100% portion of the size fraction below 0.15 mm, from which 75% of the size fraction below 0.04 mm.

**Table 5** shows the chemical composition of iron-bearing raw materials, where the difference in the richness of ores can be seen. **Figure 4** shows the structure of the samples and Energy Dispersive X-Ray Analysis (EDX), **Table 6**. The larger


**Table 3.**

**Iron ore**

*Iron Ores*

Analysis (wt.%)

Grain (mm)

Apparent density (g.cm<sup>3</sup> )

Real density (g.cm<sup>3</sup> )

Porosity (%)

Surface (m<sup>2</sup> .g<sup>1</sup> )

Drum strenght (%)

Heat test (%)

Reducibility (%)

Reducibility (min)

Plasticity (°C)

**Table 2.**

**58**

+ 6.3 mm

+ 6.3 mm

Mineralogy XRD Hematite,

*Properties of iron ores (according [3]).*

*Reducibility is according ISO 7992.*

goethite

Martite, hydrogoethite quartz

**Brazil MBR**

**Kryvyi Rih (H)**

**Australia Algeria Venezuela India**

Fe 68.13 47.59 67.20 59.50 65.09 65.50 FeO 1.12 2.00 0.49 0.24 1.08 0.53 Fe2O3 96.16 65.82 95.50 84.81 91.81 93.08 Mn 0.04 0.05 0.05 1.28 0.26 0.08 SiO2 0.53 24.30 1.77 2.85 4.49 2.81 Al2O3 1.61 3.25 1.33 0.65 1.14 2.07 CaO 0.23 0.22 0.28 1.31 0.15 0.35 MgO 0.03 0.20 0.10 0.72 0.19 0.06 P 0.05 0.05 0.02 0.02 0.03 0.03 S 0.01 0.03 0.01 0.03 0.01 0.02 Na2O 0.07 0.14 0.01 0.08 0.07 0.09 K2O 0.04 0.95 0.02 0.06 0.06 0.07

< 1 1.55 2.74 1.92 0 8.03 6.34 < 5 5.64 4.75 5.85 0 13.22 10.30 > 10 81.13 91.40 70.54 98.70 64.16 85.04 > 25 30.18 49.54 14.03 97.15 0.80 47.18 > 40 5.36 23.04 0 84.19 0 16.80 dA 20.46 28.60 16.30 59.85 11.89 25.84

ρ<sup>A</sup> 1.99 1.78 2.22 1.45 2.42 2.15

ρ 5.21 3.85 4.82 4.11 4.95 4.73

P 18.6 7.8 16.2 33.6 12.1 20.9

S 1.22 0.96 1.63 5.00 0.44 6.55

Ri 40 35 42 33 43 30

Ri60 101 110 95 121 100 170

Hematite, goethite, quartz

Pl60 1174–1320 1150–1483 1380–1423 990–1390 1265–1490 1210–1480

Limonite, goethite, hydrogoethite, quartz

Hematite, martite, goethite, quartz

Martite, goethite, hydrogoethite, quartz

78.99 84.63 89.42 75.12 88.94 77.62

76.62 73.04 69.42 85.70 69.32 62.26

*Chemical analysis of selected sinter grade ores in the delivered state [4].*


#### **Table 4.**

*Chemical analysis of selected iron ore concentrates, as delivered [4].*

#### **Figure 3.**

*Iron raw materials for sintering process.*


#### **Table 5.**

*Chemical analysis of selected iron ore materials, as delivered.*

grains of Brazil sinter grade ore are practically free of impurities and have a relatively homogeneous structure. In addition to iron oxides, the smaller sinter grade ore Brazil grains also contain impurities in the form of silicon and aluminum oxides.

In general, the richness of concentrates is in the range of 65–70%, while sinter grade ores have this interval wider and shifted slightly lower (55–67%).

Taking a closer look at the chemical composition of iron commodities, we can see a fundamental difference in the FeO content of sinter grade ores and concentrates (**Table 5**), which is related to the enrichment processes of concentrate production and mainly the hematite character of the sinter grade ores used, **Table 7**.

The SiO2 content (in the form of quartz) is desirable at a minimum level and depends on the specific ore resp. concentrate. Manganese is also a welcome ingredient and increases the utility value of ore along with titanium and vanadium. Undesirable impurities are mainly sulfur, phosphorus, zinc, lead, arsenic, copper, sodium, potassium, which are chemically bound in the minerals of the ore part of the burden, as well as in the agglomeration fuel.

The form of occurence of harmful elements in iron ores is as follows [5–7]:


Quality sinter grade ores is characterized by a high content of total iron (min. 63%), Al2O3 content max. up to 1.3%, SiO2 up to 6%, P below 0.04% and alkali

**Sinter grade ore Brazil (fine)**

**Wt% Atom % Wt% Atom % Wt% Atom %**

O 18.45 44.13 17.56 41.15 14.49 35.33 Fe 81.55 55.87 75.40 50.62 78.21 54.61 Mn — — 1.56 1.06 — — Si — — 3.00 4.01 5.77 8.02 Al — — 1.85 2.57 0.25 0.36 Ca — — 0.64 0.59 0.57 0.55 Mg — — —— 0.71 1.14

**Concentrate Inguletsky MBC**

content max. up to 0.08% [8].

*EDX analysis of selected iron ore materials.*

*EDX analysis of Brazil iron ore and Inguletsky iron concentrate.*

*Advances in Sintering of Iron Ores and Concentrates DOI: http://dx.doi.org/10.5772/intechopen.94051*

**(coarse)**

**Element Sinter grade ore Brazil**

**Figure 4.**

**Table 6.**

**61**

#### **Figure 4.**

grains of Brazil sinter grade ore are practically free of impurities and have a relatively homogeneous structure. In addition to iron oxides, the smaller sinter grade ore Brazil grains also contain impurities in the form of silicon and aluminum oxides. In general, the richness of concentrates is in the range of 65–70%, while sinter

**Iron ore material Fe FeO Fe2O3 Mn SiO2 Al2O3 CaO MgO P S Na2O K2O**

**(wt.%)**

57.86 0.72 81.94 0.05 15.17 0.74 0.15 0.25 0.05 0.01 0.08 0.05

65.23 0.14 93.12 0.57 2.21 1.32 0.10 0.10 0.05 0.01 0.05 0.05

67.91 28.45 65.57 0.07 4.92 0.18 0.59 0.49 0.02 0.09 0.06 0.07

Taking a closer look at the chemical composition of iron commodities, we can see a fundamental difference in the FeO content of sinter grade ores and concentrates (**Table 5**), which is related to the enrichment processes of concentrate production and mainly the hematite character of the sinter grade ores used, **Table 7**. The SiO2 content (in the form of quartz) is desirable at a minimum level and depends on the specific ore resp. concentrate. Manganese is also a welcome ingredient and increases the utility value of ore along with titanium and vanadium. Undesirable impurities are mainly sulfur, phosphorus, zinc, lead, arsenic, copper, sodium, potassium, which are chemically bound in the minerals of the ore part of

The form of occurence of harmful elements in iron ores is as follows [5–7]:

• Sulfur is present in the form of sulphides such as FeS2 and FeS and of sulphates

grade ores have this interval wider and shifted slightly lower (55–67%).

the burden, as well as in the agglomeration fuel.

*Chemical analysis of selected iron ore materials, as delivered.*

**Figure 3.**

*Iron Ores*

*Iron raw materials for sintering process.*

Sinter grade ore Krivbas

Sinter grade ore Brazil

Concentrate Inguletsky MBC

**Table 5.**

• Lead occurs in the form of galena.

such as CaSO4, MgSO4, BaSO4.

**60**

• Arsenic is present in arsenopyrite or arsenolite.

• Zinc is present in the form of smithsonite or sphalerite.

• Phosphorus forms phosphite, which is a part of apatite.

• Copper can be present in the form of chalcopyrite or chalcosine.

*EDX analysis of Brazil iron ore and Inguletsky iron concentrate.*


#### **Table 6.**

*EDX analysis of selected iron ore materials.*

Quality sinter grade ores is characterized by a high content of total iron (min. 63%), Al2O3 content max. up to 1.3%, SiO2 up to 6%, P below 0.04% and alkali content max. up to 0.08% [8].


**Table 7.**

*RTG analysis of selected iron raw materials.*

From the mineralogical point of view, it is important to know the ore texture and structure that characterizes the distribution of individual mineralogical components, respectively indicates the shape and size of the mineral components and the nature of their structure. The mineralogical composition of Fe ores is characterized by the majority shape of the grain in terms of their structure, **Table 8** [2].

distribution will be related to the processing and treatment of extracted ore or the production of iron concentrate. Fine-grained concentrates are the product of flotation enrichment of ores and their predominant grain size is about 0.04 mm. The granularity is also directly related to the mineralogical composition and structure of the ore. The concentrates used in the sintering process have an overall wide grain size range. Most Ukrainian and Russian concentrates are very fine-grained in nature, where the extracted magnetite quartzite is crushed and ground below 0.075 mm and enriched by magnetic separation into a concentrate with Fe content up to 68%. Swedish magnetite concentrate, on the other hand, has only about 4% of the fraction below 0.1 mm at a richness of about 70%. Canadian magnetite concentrates have a proportion below 0.1 mm of about 15%, while the upper grain limit does not exceed 1 mm.

*Distribution of grain in iron concentrates. (a) Concentrate Kovdor MBC, (b) concentrate Lebedinsky MBC.*

The results of analysis of the selected concentrates are given in **Figure 6**.

*the sinter and on the production of pig iron*

*Advances in Sintering of Iron Ores and Concentrates DOI: http://dx.doi.org/10.5772/intechopen.94051*

production is characterized:

**Figure 6.**

of ores must ensure:

impurities,

**63**

*1.1.2 The influence of the properties of iron ores and concentrates on the final quality of*

The operation of the blast furnace and the results of its work are most often evaluated according to the output and consumption of coke. Changes in the chemical composition and particle size distribution of the iron-bearing materials significantly affect their technological properties and thus the balance of components and the course of the blast furnace process. The development of iron metallurgy is conditioned by the quantity and quality of iron ores. The raw material base for iron

• lack of high-quality natural ores - only 10–12% of the world's iron ore reserves

To meet the requirements of the metallurgical industry, mined ores are increasingly treated and processed before being used in blast furnaces, and the treatment

meet the current requirements of blast furnace practice,

• uneven distribution of world stocks in individual countries,

• use of high-performance equipment in ore mining and enrichment.

• an increase in the iron content and removal of harmful and unwanted

• low content of metal-bearing substance in mined ore,

Some iron bearing materials were evaluated prior to laboratory experiments and the grain shape factor was determined [9]. The grain shape factor specifies calculation a grain periphery, which differs from the circle (for circle is shape factor = 1). The iron ore shown in **Figure 5a** consists the grains with polyhedron shape (shape factor = 0.59) in a size of 5–40 μm. The iron ore shown in **Figure 5b** consists of the grains with polyhedron shape (shape factor = 0.94) with smooth surfaces in a size of 10–50 μm. In this case, the hematite grains are clearly visible. The iron ore shown in **Figure 5c** consists of the grains with partially smoothened edges of polyhedron shape (shape factor = 0.78) in a size of 10–100 μm. The iron ore shown in **Figure 5d** consists of the grains with lamellas shape (shape factor = 0.70) in size of 10–250 μm. The hematite grain can be seen at the top.

In addition to the chemical-mineralogical composition of sinter grade ores and concentrates, it is also necessary to know their granulometry. The grain size


#### **Table 8.**

*Major grain shape types of iron ores [2].*

**Figure 5.** *Microstructures of iron ores with various shape factors [9]. (a) 0.59, (b) 0.94, (c) 0.78, (d) 0.70.*

*Advances in Sintering of Iron Ores and Concentrates DOI: http://dx.doi.org/10.5772/intechopen.94051*

**Figure 6.**

From the mineralogical point of view, it is important to know the ore texture and structure that characterizes the distribution of individual mineralogical components, respectively indicates the shape and size of the mineral components and the nature of their structure. The mineralogical composition of Fe ores is characterized by the majority shape of the grain in terms of their structure, **Table 8** [2].

**Sinter grade ore Krivbas**

Hematite 72.50 75.48 — Magnetite — — 89.70 Goethite 15.20 18.73 — Mayenite — 1.23 — Quartz 12.30 4.56 10.30

**Content of phase (wt%)**

**Concentrate Inguletsky MBC**

**Sinter grade ore Brazil**

Some iron bearing materials were evaluated prior to laboratory experiments and the grain shape factor was determined [9]. The grain shape factor specifies calculation a grain periphery, which differs from the circle (for circle is shape factor = 1). The iron ore shown in **Figure 5a** consists the grains with polyhedron shape (shape factor = 0.59) in a size of 5–40 μm. The iron ore shown in **Figure 5b** consists of the grains with polyhedron shape (shape factor = 0.94) with smooth surfaces in a size of 10–50 μm. In this case, the hematite grains are clearly visible. The iron ore shown in **Figure 5c** consists of the grains with partially smoothened edges of polyhedron shape (shape factor = 0.78) in a size of 10–100 μm. The iron ore shown in **Figure 5d** consists of the grains with lamellas shape (shape factor = 0.70) in size of 10–250 μm.

In addition to the chemical-mineralogical composition of sinter grade ores and

concentrates, it is also necessary to know their granulometry. The grain size

**Mineralogical composition Shape of grain** Magnetite, pyrite, quartz Spherical, cubic Magnetite, hematite, goethite, quartz Cubic, platelet-shaped Hematite, goethite, quartz, kaolinite Platelet-shaped, fragmentary Hematite Polyhydral, plate-shaped

*Microstructures of iron ores with various shape factors [9]. (a) 0.59, (b) 0.94, (c) 0.78, (d) 0.70.*

The hematite grain can be seen at the top.

*Major grain shape types of iron ores [2].*

*RTG analysis of selected iron raw materials.*

**Mineralogical phase**

*Iron Ores*

**Table 7.**

**Table 8.**

**Figure 5.**

**62**

*Distribution of grain in iron concentrates. (a) Concentrate Kovdor MBC, (b) concentrate Lebedinsky MBC.*

distribution will be related to the processing and treatment of extracted ore or the production of iron concentrate. Fine-grained concentrates are the product of flotation enrichment of ores and their predominant grain size is about 0.04 mm. The granularity is also directly related to the mineralogical composition and structure of the ore. The concentrates used in the sintering process have an overall wide grain size range. Most Ukrainian and Russian concentrates are very fine-grained in nature, where the extracted magnetite quartzite is crushed and ground below 0.075 mm and enriched by magnetic separation into a concentrate with Fe content up to 68%. Swedish magnetite concentrate, on the other hand, has only about 4% of the fraction below 0.1 mm at a richness of about 70%. Canadian magnetite concentrates have a proportion below 0.1 mm of about 15%, while the upper grain limit does not exceed 1 mm. The results of analysis of the selected concentrates are given in **Figure 6**.
