**1.2. Siderite**

The name of the siderite mineral is derived from the word sideros (σίδηρος), meaning iron in Greek. Technically, siderite minerals contains about 48.02% iron (Fe) and be crystal trigonal (hexagonal scalenohedral) system, mostly rhombohedral crystalline; plate, prismatic, massive;

medium-fine grained; rarely kidney, oolitic crystal habits. Siderite minerals have transparentsemi-transparent appearance and have different colours like yellowish-brown to greyishbrown, pale yellow to tannish, grey, brown, green, red, black and sometimes nearly colourless; tarnished iridescent at times; colourless to yellow and yellow-brown in transmitted light. The

**Countries/region 2011 2012 2013 2014 2015** South Korea 1190.1 1135.3 1081.7 1155.0 1155.7 Czech Republic 663.1 639.8 641.5 678.6 723.9 Japan 546.9 541.1 558.3 574.9 535.7 Germany 561.3 507.3 517.0 530.1 523.9 China 495.4 507.3 562.0 540.6 509.0 Australia 527.1 488.1 475.1 480.4 466.2 Turkey 389.9 404.6 436.9 422.5 464.7 Canada 456.4 496.3 466.8 492.5 412.5 EU (28 countries) 343.0 306.2 311.1 322.0 331.6 North America 267.4 285.2 276.7 311.1 282.9 Asia 256.4 261.7 282.2 277.8 266.1 Middle East 257.6 250.3 248.8 251.9 244.4 World 221.3 223.3 234.5 234.1 224.4 South America 126.4 128.0 132.3 122.8 112.4 Africa 30.1 32.8 35.4 35.4 35.7

Massive siderite is commonly found in layered sedimentary beds, especially in mudstones and marls. In addition, it was found as a gangue mineral in hydrothermal ore vein which contains pyrite, chalcopyrite and galenite. It is also found in basaltic volcanic rocks, sometimes in

Calcination is the breakdown of carbonates and hydrates by the effect of temperature in order to obtain oxide form compounds. Calcination not only involves removing of water in the crystal structure, but also removes carbon dioxide or other chemically bound gases such as

All calcination reactions are endothermic. In terms of thermodynamic rule, the decomposition

and its Mohs hardness is between 3.5 and 4.5.

Calcination and Pelletizing of Siderite Ore http://dx.doi.org/10.5772/intechopen.72808 83

partial pressure. The calcination

→ MeO(s) + CO<sup>2</sup> (1)

specific weight of siderite mineral is 3.96 g/cm<sup>3</sup>

pegmatites and metamorphic rocks.

MeCO3(s)

**1.3. Calcination**

hydrates, carbonates.

A sample of siderite giving large crystals is given in **Figure 1**.

**Table 2.** Crude steel consumption per capita of the country and regions (kg/person) [3].

of a carbonate at a constant temperature is a function of CO2

reaction is given in the following Eq. (1) for carbonate compounds.


**Table 1.** Top 10 countries in world crude steel production (million metric tons) [3].


**Table 2.** Crude steel consumption per capita of the country and regions (kg/person) [3].

medium-fine grained; rarely kidney, oolitic crystal habits. Siderite minerals have transparentsemi-transparent appearance and have different colours like yellowish-brown to greyishbrown, pale yellow to tannish, grey, brown, green, red, black and sometimes nearly colourless; tarnished iridescent at times; colourless to yellow and yellow-brown in transmitted light. The specific weight of siderite mineral is 3.96 g/cm<sup>3</sup> and its Mohs hardness is between 3.5 and 4.5. A sample of siderite giving large crystals is given in **Figure 1**.

Massive siderite is commonly found in layered sedimentary beds, especially in mudstones and marls. In addition, it was found as a gangue mineral in hydrothermal ore vein which contains pyrite, chalcopyrite and galenite. It is also found in basaltic volcanic rocks, sometimes in pegmatites and metamorphic rocks.

#### **1.3. Calcination**

important of the heavy industry sectors, supplies raw materials to many important industries such as construction, infrastructure, automotive, white goods and machinery industry. Therefore, it can be said that industrialization of a country is directly related to its strong iron and steel sector and consumption [2]. **Table 1** gives the top 10 countries producing the crude

Today iron constitutes the basic raw material of the industry and plays an important role in the economic development of the countries. The economic development indicators of countries are also determined by per capita iron and steel consumption. **Table 2** shows the consumption of

In the past, iron ore with the characteristics required for blast furnace charging was met directly from iron mines. The need for iron in the industry has increased rapidly and also the reserve of the iron ore which can be directly loaded into the blast furnace has gradually decreased. Therefore recently, the irons ores with low grade have been started to be evaluated. The crude iron ore reserves and its iron content in the world are given in **Table 3**.

The main raw material of the iron and steel industry is iron ore. It must be economical to operate and use a mine as an ore. It is desirable that the blend grade of the iron ores used in the steel industry is at least 57% Fe grade. The iron ore is found in the form of magnetite

The name of the siderite mineral is derived from the word sideros (σίδηρος), meaning iron in Greek. Technically, siderite minerals contains about 48.02% iron (Fe) and be crystal trigonal (hexagonal scalenohedral) system, mostly rhombohedral crystalline; plate, prismatic, massive;

**No Country 2011 2012 2013 2014 2015 2015 (%)** China 701.9 731.0 822.0 822.8 803.8 49.60 Japan 107.6 107.2 110.6 110.7 105.1 6.48 India 73.4 77.2 81.2 87.2 89.0 5.49 USA 86.3 88.6 88.8 88.1 78.8 4.86 Russia 68.8 70.2 69.0 71.4 70.8 4.36 South Korea 68.5 69.0 66.0 71.5 69.6 4.29 Germany 44.2 42.6 42.6 42.9 42.6 2.62 Brazil 35.2 34.5 34.1 33.8 33.2 2.04 Turkey 34.1 35.8 34.6 34.0 31.5 1.94 Ukraine 35.3 32.9 32.7 27.1 22.9 1.41

> EU (28 countries) 177.7 168.5 166.3 169.3 166.1 10.25 World 1538.0 1560.1 1650.3 1669.8 1620.4 100

**Table 1.** Top 10 countries in world crude steel production (million metric tons) [3].

O), goethite (α-Fe3+O(OH)), siderite (FeCO3

)

), limonite (FeO(OH)⋅nH<sup>2</sup>

steel in the world.

82 Iron Ores and Iron Oxide Materials

steel per capita.

(Fe3 O4

), hematite (Fe<sup>2</sup>

and pyrite (FeS<sup>2</sup>

**1.2. Siderite**

O3

) minerals in the nature.

Calcination is the breakdown of carbonates and hydrates by the effect of temperature in order to obtain oxide form compounds. Calcination not only involves removing of water in the crystal structure, but also removes carbon dioxide or other chemically bound gases such as hydrates, carbonates.

All calcination reactions are endothermic. In terms of thermodynamic rule, the decomposition of a carbonate at a constant temperature is a function of CO2 partial pressure. The calcination reaction is given in the following Eq. (1) for carbonate compounds.

$$\text{MeCO}\_{3} \rightarrow \text{MeO}\_{(6)} \star \text{CO}\_{2} \tag{1}$$


The calcination process for siderite ore aims to remove the bound CO2

. Siderite calcination reactions are given in the following short chemical Eqs. (2)–(4)

FeCO3 → FeO + CO<sup>2</sup> (2)

3 FeCO3 → Fe3 O<sup>4</sup> + 2 CO<sup>2</sup> + CO (3)

3FeO + CO<sup>2</sup> → Fe3 O<sup>4</sup> + CO (4)

lose about 30 wt% of its weight. However, it is necessary to reach a temperature of at least 700°C for this weight loss. The calcination of siderite ore is mostly carried out in rotary kilns. The ore entering the rotary kiln as siderite; leaving the furnace turned into a mixture of hematite, magnetite and maghemite. The distribution of the minerals in this mixture depends on the working temperature of the oven and the duration time. At low temperatures, primarily hematite and then magnetite transformation occurs. However, the mixture is predominantly hematite in every case.

Conventional heating principles have been utilized in the heating and/or roasting processes of some raw ores or materials from the past to the present day. There are three basic mechanisms of conventional heating, namely convection, conduction and diffusion. These three heat transfer mechanisms in conventional heating heat the material from the outside to the inside. This method causes large time and energy losses to occur during conduction by conduction into inside of materials. Microwave energy is non-ionizing electromagnetic radiation (radiation) having a frequency in the range of 300 MHz to 300 GHz, with intensive application in the field of communication; only certain frequencies are allowed for industrial, scientific and medical (ISM) applications [6]. Microwave heating is different from conventional heating because it is in the form of electromagnetic energy that can penetrate the depths of the sample [7]. The samples are heated inside to outside in microwave heating systems [8]. The differences between microwave and conventional heating systems and principles are represented in **Figure 2**.

In microwave heating systems, electromagnetic energy is directly converted into heat inside of the material and heating starts inside to outside contrary to the conventional heating. The microwaves propagate at the speed of light and as soon as the source is turned on the electromagnetic wave immediately penetrates to materials and starts to energy conversion. Long heating and cooling phases are not required when the source is turned off, since the heating

Pellets are the oval/spherical shaped pieces of ore having high compression strength which are obtained from fines or from finely ground ores by adding various additives like bentonite

and whose diameter is generally between 8 and 20 mm as shown in **Figure 3**.

composition is removed from the siderite ore structure. So, it

FeCO3

During the calcination process, CO2

process is stopped immediately [10].

**1.5. Pellets**

**1.4. Traditional and microwave heating methods**

in the formation of

85

Calcination and Pelletizing of Siderite Ore http://dx.doi.org/10.5772/intechopen.72808

**Table 3.** Iron ore reserves and its iron content in the world (million metric tons) [4].

The equilibrium constant of the reaction equals the partial pressure of the CO2 if the solids activities are equal to one another. Therefore, the complete decomposition temperature of a carbonate compound is the temperature at which the P0 CO2 pressure equals an atmospheric pressure.

**Figure 1.** Crystal-shaped siderite sample [5].

The calcination process for siderite ore aims to remove the bound CO2 in the formation of FeCO3 . Siderite calcination reactions are given in the following short chemical Eqs. (2)–(4)

$$\text{FeCO}\_3 \rightarrow \text{FeO} \star \text{CO}\_2 \tag{2}$$

$$\text{3FeCO}\_3 \rightarrow \text{Fe}\_3\text{O}\_4 + 2\text{CO}\_2 + \text{CO} \tag{3}$$

$$\text{3FeO} + \text{CO}\_2 \rightarrow \text{Fe}\_3\text{O}\_4 + \text{CO} \tag{4}$$

During the calcination process, CO2 composition is removed from the siderite ore structure. So, it lose about 30 wt% of its weight. However, it is necessary to reach a temperature of at least 700°C for this weight loss. The calcination of siderite ore is mostly carried out in rotary kilns. The ore entering the rotary kiln as siderite; leaving the furnace turned into a mixture of hematite, magnetite and maghemite. The distribution of the minerals in this mixture depends on the working temperature of the oven and the duration time. At low temperatures, primarily hematite and then magnetite transformation occurs. However, the mixture is predominantly hematite in every case.

### **1.4. Traditional and microwave heating methods**

Conventional heating principles have been utilized in the heating and/or roasting processes of some raw ores or materials from the past to the present day. There are three basic mechanisms of conventional heating, namely convection, conduction and diffusion. These three heat transfer mechanisms in conventional heating heat the material from the outside to the inside. This method causes large time and energy losses to occur during conduction by conduction into inside of materials. Microwave energy is non-ionizing electromagnetic radiation (radiation) having a frequency in the range of 300 MHz to 300 GHz, with intensive application in the field of communication; only certain frequencies are allowed for industrial, scientific and medical (ISM) applications [6]. Microwave heating is different from conventional heating because it is in the form of electromagnetic energy that can penetrate the depths of the sample [7]. The samples are heated inside to outside in microwave heating systems [8]. The differences between microwave and conventional heating systems and principles are represented in **Figure 2**.

In microwave heating systems, electromagnetic energy is directly converted into heat inside of the material and heating starts inside to outside contrary to the conventional heating. The microwaves propagate at the speed of light and as soon as the source is turned on the electromagnetic wave immediately penetrates to materials and starts to energy conversion. Long heating and cooling phases are not required when the source is turned off, since the heating process is stopped immediately [10].

### **1.5. Pellets**

**Figure 1.** Crystal-shaped siderite sample [5].

compound is the temperature at which the P0

**Countries Reserves**

84 Iron Ores and Iron Oxide Materials

The equilibrium constant of the reaction equals the partial pressure of the CO2

**Table 3.** Iron ore reserves and its iron content in the world (million metric tons) [4].

Australia 52.000 23.000 Russia 25.000 14.000 Brazil 23.000 12.000 China 21.000 7.200 India 8.100 5.200 Ukraine 6.500 2.300 Canada 6.000 2.300 Sweden 3.500 2.200 United States 3.000 790 Iran 2.700 1.500 Kazakhstan 2.500 900 South Africa 1.200 770 Other countries 18.000 9.500 World total (rounded) 170.000 82.000

ties are equal to one another. Therefore, the complete decomposition temperature of a carbonate

**Crude ore Iron content**

if the solids activi-

CO2 pressure equals an atmospheric pressure.

Pellets are the oval/spherical shaped pieces of ore having high compression strength which are obtained from fines or from finely ground ores by adding various additives like bentonite and whose diameter is generally between 8 and 20 mm as shown in **Figure 3**.

**Figure 2.** Schematic representation of the comparison of the microwave and conventional heating process [9].

Iron ore pellets can be used as a substitute to sinter and calibrated lump ores in the blast furnace burden. Apart from these pellets can be applied to some non-ferrous metal ores such as lead and chromium ores [11].

Since the 1960s, pelletizing technology has been rapidly developed and provided a quality chargeable material for iron making.

According to 2011 data the world pellet production on the basis of countries and regions is given in **Table 4**.

The purpose of the iron pelletizing process is to convert the iron-rich fine-grained minerals into blast furnace charging material, which is defined as pellet, through agglomeration and hardening. The pellets are rigid and generally spherical shape and must have the following properties to be used in the high-temperature furnace:

**a.** must be free from dust and fines.

blast furnace depending on the heating process.

**Table 4.** Pellet production in the world and in the region (million metric tons) [12].

**Iron ore, world pelletizing capacity by content and country in 2011**

Canada 27.5 Mexico 15.0 United States 57.4 Total 99.9

Brazil 56.0 Chile 5.3 Peru 3.5 Venezuela 11.8 Total 76.6

Kazakhstan 8.4 Netherlands 4.4 Russia 31.4 Slovakia 0.4 Sweden 26.0 Turkey 1.5 Ukraine 33.5 Total 105.6

Bahrain 11.0 China 135.0 India 24.0 Iran 12.3 Oman 9.0 Japan 3.0 Total 194.3 *Ocenia, Australia* 4.3 Grand total 480.7

*North America*

*South America*

*Asia*

*Europe and Central Eurasia*

**Rated capacity gross weight (million metric tons)**

Calcination and Pelletizing of Siderite Ore http://dx.doi.org/10.5772/intechopen.72808 87

**b.** must show physical strength against breakage during transportation and storage.

**c.** must be resistant to crumbling which will occur during various reactions occurring in the

The ore to be pelletized may be enriched low-grade iron ore or high-grade powder forms ores which cannot be directly charged into the blast-furnace. The pelletizing process consists


**Table 4.** Pellet production in the world and in the region (million metric tons) [12].

**a.** must be free from dust and fines.

**Figure 3.** The pellets form of iron ore.

lead and chromium ores [11].

86 Iron Ores and Iron Oxide Materials

given in **Table 4**.

chargeable material for iron making.

properties to be used in the high-temperature furnace:

Iron ore pellets can be used as a substitute to sinter and calibrated lump ores in the blast furnace burden. Apart from these pellets can be applied to some non-ferrous metal ores such as

**Figure 2.** Schematic representation of the comparison of the microwave and conventional heating process [9].

Since the 1960s, pelletizing technology has been rapidly developed and provided a quality

According to 2011 data the world pellet production on the basis of countries and regions is

The purpose of the iron pelletizing process is to convert the iron-rich fine-grained minerals into blast furnace charging material, which is defined as pellet, through agglomeration and hardening. The pellets are rigid and generally spherical shape and must have the following


The ore to be pelletized may be enriched low-grade iron ore or high-grade powder forms ores which cannot be directly charged into the blast-furnace. The pelletizing process consists of two main parts: raw pellet (green ball) and product pellet. The raw pellet is obtained by mixing the enriched ore with the binders followed by the agglomeration process, the product pellet is obtained by heating and cooling the raw pellet [13].

The pelletizing process occurs in four basic stages, as shown in **Figure 4**. First, the ore and the various additives are mixed to obtain a homogeneous form. The distribution of the materials forming the pellet cake is of great importance in terms of pellet strength. After mixing operation, the mixture is transferred balling discs to obtain pellet form.

This product is called green pellet. Optionally, the process may be ended at this step depending on the needed or, the pellet is transferred to the next device and subjected to the induration to obtain the product pellet as shown in **Figure 5**. After this process, the cooled material is now named the product pellet.


In the process of obtaining the product pellet, the principle is that the material be heated at a recrystallization temperature according to the compound type. The recrystallization temperature for siderite is about 1300°C. If this temperature level is exceeded too much, liquid phase

In this study, siderite ore was obtained from the Deveci district of Hekimhan Malatya Province. **Figure 6** shows the pictures of the raw siderite ore and the calcined siderite ore used in the

In addition, the bentonite which was used during the pelletizing process was also obtained from

Bentonite, a volcanic mineral formed by the decomposition of volcanic ash in situ and composed of montmorillonite clay mineral of large size which absorbs water and is used commercially in

In the microwave experiment part, sucrose—C12H22O11 (Merck 99.5%) and urea CH<sup>4</sup>

(Merck 99.5%) was used as a thermal auxiliary and consolidate purposes, respectively.

and colours are white, grey, yellow, pink and green.

Calcination and Pelletizing of Siderite Ore http://dx.doi.org/10.5772/intechopen.72808 89

N2 O

formation is occurred and undesirable sintering process starts.

study. The elemental analyses of raw siderite ore is given in **Table 5**.

**2. Materials**

**2.1. Ore and chemicals**

Hekimhan/Malatya. Its density is 2.60 g/cm<sup>3</sup>

**Figure 5.** Schematic of the straight grate process [14].

drilling mud, catalyst, paint, plastic filling works [15].

**Figure 4.** Schematic of a pelletizing plant with wet grinding [14].

**Figure 5.** Schematic of the straight grate process [14].

In the process of obtaining the product pellet, the principle is that the material be heated at a recrystallization temperature according to the compound type. The recrystallization temperature for siderite is about 1300°C. If this temperature level is exceeded too much, liquid phase formation is occurred and undesirable sintering process starts.
