**3.1. Milling operation**

The raw siderite ore used in the study was sieved and weighed. The results of the sieve analysis are given in **Figure 7**. When the graph was examined, it was determined that P80 (80% of the feed passed through the sieve) was 7.9 mm and d50 (50% of the feed passed through the sieve) was 5.6 mm.

Grinding operation was done by a laboratory-type ball mill not only to examine the grindability properties of the siderite ore but also to produce fine fractions required for pelletizing.

Calcination and Pelletizing of Siderite Ore http://dx.doi.org/10.5772/intechopen.72808 91

As milling media, four different sizes of balls were charged with diameters of 20, 25, 30 and

**Figure 9** shows the undersize graphs of raw siderite ore grounded at different times.

40 mm and milling parameters are given in **Table 6**.

**Figure 8.** Comparison of raw and calcined siderite cumulative undersize graphs.

**Figure 7.** Cumulative undersize graph of raw siderite.

The raw siderite ore was both directly grounded and calcined before grinding operation. During this calcination process, CO2 is removed by the effect of temperature, causing the capillary cracks in the ore, as a result fragmentation and crumbling is occurred. This situation is evident in the cumulative undersize graph given in **Figure 8** showing that calcination process slightly decreased the particle size of the siderite.


**Table 5.** Chemical analysis of raw siderite ore sample.

**Figure 7.** Cumulative undersize graph of raw siderite.

**Component Concentration (%)**

The raw siderite ore used in the study was sieved and weighed. The results of the sieve analysis are given in **Figure 7**. When the graph was examined, it was determined that P80 (80% of the feed passed through the sieve) was 7.9 mm and d50 (50% of the feed passed through the sieve)

The raw siderite ore was both directly grounded and calcined before grinding operation.

illary cracks in the ore, as a result fragmentation and crumbling is occurred. This situation is evident in the cumulative undersize graph given in **Figure 8** showing that calcination process

is removed by the effect of temperature, causing the cap-

(Fe %) 53.21 (37.25)

MgO 18.88

slightly decreased the particle size of the siderite.

**Figure 6.** Raw siderite (on the left) and calcined siderite (on the right).

O3 0.25 SiO<sup>2</sup> 4.42 SO3 0.84

O 0.81 CaO 9.87 MnO 11.39

**Table 5.** Chemical analysis of raw siderite ore sample.

Fe<sup>2</sup> O3

**3. Experimental part**

90 Iron Ores and Iron Oxide Materials

During this calcination process, CO2

**3.1. Milling operation**

was 5.6 mm.

Al2

K2

Grinding operation was done by a laboratory-type ball mill not only to examine the grindability properties of the siderite ore but also to produce fine fractions required for pelletizing. **Figure 9** shows the undersize graphs of raw siderite ore grounded at different times.

As milling media, four different sizes of balls were charged with diameters of 20, 25, 30 and 40 mm and milling parameters are given in **Table 6**.

**Figure 8.** Comparison of raw and calcined siderite cumulative undersize graphs.

**Figure 9.** Cumulative undersize graphs of raw siderite ore that milled at different times.

The raw siderite was also calcined and then subjected to grinding. The cumulative undersize curves of calcined siderite ore are given in **Figure 10**.

Minimizing the size of raw materials such as ores and rocks also seriously damages the machinery and milling equipments, as well as the enormous energy consumption. Today, about 40% of the energy consumed in mining operations is spent for size reduction. It takes 3.3% of the total electricity energy consumed in the world. This demonstrates the importance

Calcination and Pelletizing of Siderite Ore http://dx.doi.org/10.5772/intechopen.72808 93

**Figure 10.** Cumulative undersize graphs of calcined siderite ore, which were milled at different times.

In this respect, the production of the fine material required for the production of the pellet should be done after the calcination step. In this way it will be possible to save a great deal of energy and extend the life of grinding machines. This is only one of the advantages to be

of energy efficiency in size reduction processes [10, 16].

achieved as a result of making changes in the pellet production process.

**Figure 11.** Cumulative undersize graphs of raw and calcined siderite at equidistant times.

Aforementioned, the cracking occurs in the siderite structure due to CO2 escaping from its body during the calcination process. A similar situation is also in the grinding process. The calcined siderite was ground much easier than raw siderite when the raw and calcined siderite were grounded at the same conditions (90 min) as shown in **Figure 11**.

As can be seen from the above graph, the size fraction of both raw siderite and calcined siderite is quite different with each other after the same milling operation. In the graph, the size of d50 grain for the raw siderite is 66 μm while calcined siderite for d50 is found as 54 μm. Although there are minor differences in the small size fraction, the raw and the calcined siderite are not noteworthy in scale. However, it is not possible to mention about fractions of large grain size from the same situation. The value of P80 for the raw siderite is 4.75 mm while for the calcined siderite this value is 110 μm. P80 value of the calcined siderite is about 43 times smaller than that of the raw siderite. Thus, the grinding effect of the calcination process increases as the size increases. Moreover, calcined siderite has reached these grinding values with a feed of 40% higher than the raw siderite volume.


**Table 6.** Grinding parameters.

**Figure 10.** Cumulative undersize graphs of calcined siderite ore, which were milled at different times.

The raw siderite was also calcined and then subjected to grinding. The cumulative undersize

body during the calcination process. A similar situation is also in the grinding process. The calcined siderite was ground much easier than raw siderite when the raw and calcined sider-

As can be seen from the above graph, the size fraction of both raw siderite and calcined siderite is quite different with each other after the same milling operation. In the graph, the size of d50 grain for the raw siderite is 66 μm while calcined siderite for d50 is found as 54 μm. Although there are minor differences in the small size fraction, the raw and the calcined siderite are not noteworthy in scale. However, it is not possible to mention about fractions of large grain size from the same situation. The value of P80 for the raw siderite is 4.75 mm while for the calcined siderite this value is 110 μm. P80 value of the calcined siderite is about 43 times smaller than that of the raw siderite. Thus, the grinding effect of the calcination process increases as the size increases. Moreover, calcined siderite has reached these grinding values with a feed

escaping from its

**Calcined siderite feed (% volume)**

Aforementioned, the cracking occurs in the siderite structure due to CO2

**Figure 9.** Cumulative undersize graphs of raw siderite ore that milled at different times.

ite were grounded at the same conditions (90 min) as shown in **Figure 11**.

**Real and bulk density (g/cm3 )**

20 32.78 30 7.82–4.57 32 3000 20 28

**Ball charge ratio (% volume)**

**Feed (g) Feed ratio** 

**(% volume)**

curves of calcined siderite ore are given in **Figure 10**.

92 Iron Ores and Iron Oxide Materials

of 40% higher than the raw siderite volume.

**Ball mass (g) Charge** 

**(piece)**

**Ball diameter (mm)**

25 64.00 20 30 110.70 20 40 262.34 17

**Table 6.** Grinding parameters.

Minimizing the size of raw materials such as ores and rocks also seriously damages the machinery and milling equipments, as well as the enormous energy consumption. Today, about 40% of the energy consumed in mining operations is spent for size reduction. It takes 3.3% of the total electricity energy consumed in the world. This demonstrates the importance of energy efficiency in size reduction processes [10, 16].

In this respect, the production of the fine material required for the production of the pellet should be done after the calcination step. In this way it will be possible to save a great deal of energy and extend the life of grinding machines. This is only one of the advantages to be achieved as a result of making changes in the pellet production process.

**Figure 11.** Cumulative undersize graphs of raw and calcined siderite at equidistant times.
