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

**Table 14.**

*Properties of sinters with coke substitution.*

**Sinter**

**74**

**Coke powder (100%)**

> Analysis (wt.%)

Fe

FeO

Fe

Mn SiO2

Al

O2 3

CaO MgO

P S K

C

> 25

25–10

10–5

< 5

dA

> Tumbler index (%)

Abrasion index (%)

 + 6.3 mm

 - 0.5 mm

22.88 14.63 22.32 16.71

62

7

40.17

Grain (mm)

O2

0.77 10.29 2.04 0.021 0.024 0.048

0.14

O2 3

66.71 0.07 9.88

50.94

8.35

51.05

5.32 63.22 0.05 10.64

0.72 10.64

2.75 0.026 0.028 0.064

0.23 44.01 15.45 14.28 26.26 16.53

62 10

9

8

58

65

17.64

17.85

17.82

21.45

14.27

11.70

25.55

19.43

42.36

47.42

0.21

0.22

0.050

0.045

0.021

0.022

0.020

12.51 2.16

1.85 0.061

12.54

0.79

1.05

11.65

7.13

0.08

0.06

61.07

67.54

6.76

7.55

50.85

53.43

49.53

6.33 63.79 0.07 10.27

0.68 11.83 2.66 0.024 0.011 0.032

0.14 24.38 22.60 20.38 32.64 13.00

54 10

50.94

5.08

67.24

0.06

11.04

0.69

12.41

2.54

0.042

0.020

0.043

0.18

25.17

16.49

18.53

39.80

12.19

50

11

 **Charcoal (86%)**

 **Nut shells (20%)**

 **Lignin (20%)**

 **Oak sawdust (20%)**

 **Pine sawdust (20%)**

*Iron Ores*

## *1.3.2 The influence of carbonaceous fuels on the quality of the sinter and on the economic and ecological parameters of the sintering of iron ores and concentrates*

minimum of carbonate and silicate phases), they are well reducible (Ri60 below 100 min.) and stable after temperature tests (+6.3 mm above 70%). Sinter grade ores and concentrates are characterized as iron ore raw materials with the required granulometry and chemical and mineralogical composition. 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%). The larger grains of sinter grade ore are practically free of impurities and have a relatively homogeneous structure. In addition to iron oxides, the smaller sinter grade ore grains also contain impurities in the form of silicon and aluminum oxides. Undesirable impurities are mainly sulfur, phosphorus, zinc, lead, arsenic, copper, sodium, potassium, which are chemically

A new direction in the sintering process is showing the replacement of coke with biomass. It is a more environmentally friendly way of production and practice will show that it will also be more economical in the future. It can be seen in some experiments with biomass standard quality parameters on several sinters and lower emissions of COx, NOx and SO2 are achieved. It is possible to substitute about 10– 20% of coke breeze by individual types of biomass in the sintering process. Properties of input iron bearing and basic raw materials are indeed crucial factors that affect the final quality of sinter, but no less important are the properties and the amount of carbonaceous fuel and high-temperature sintering technology. Progress in the production of pig iron in blast furnaces can be achieved by improving the quality of burden, especially iron ores and sinters. A significant improvement in the performance of blast furnaces is currently achieved by using a burden with a modified chemical and particle size distribution, which allows a more complete use

This research was funded by [APVV] Slovak Research and Development

Jaroslav Legemza\*, Róbert Findorák, Mária Fröhlichová and Martina Džupková Institute of Metallurgy, Faculty of Materials, Metallurgy and Recycling, Technical

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

bound in the minerals of the iron ores.

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

**Acknowledgements**

**Conflict of interest**

**Author details**

**77**

University of Košice, Slovakia

provided the original work is properly cited.

of the chemical and thermal energy of the reducing gas.

Agency, Slovak Republic number APVV–16-0513.

The authors declare no conflict of interest.

\*Address all correspondence to: jaroslav.legemza@tuke.sk

Starting from an analysis of the considered biofuels (**Table 12**) and proposed methodology for the performance of experiments, coke breeze was partly replaced with a defined quantity of individual biomass types. The materials whose composition is given in the **Tables 5, 10** were used for the experiments. **Tables 13, 14** give characteristics of sinters produced with biomass substitution of coke breeze. It can be seen in some experiments with biomass standard quality parameters on several sinters and lower emissions of COx, NOx and SO2 are achieved. It is possible to substitute about 10–20% of coke breeze by individual types of biomass in the sintering process. Combustion of plant biomass mainly depends on the carbon structure of the cellulose, hemicellulose and lignin, which differ from the amorphous carbon in coke (coke breeze). The maximum temperatures in the sintering process are lower with biomass than with actual coke breeze [11]. Biomass fuels can burn more quickly than coke breeze due to their high porosity and large interface area, while there is a significant increase in the vertical speed of sintering. The combustion of biomass decreases the maximum temperature and abbreviates the holding time at the high temperature. Lower temperatures in the sintered layer observed with the addition of biomass can also be attributed to the condensation of volatile organic compounds [11]. These compounds can eventually be converted into a phase similar to ash and reduce the heat transfer in the direction of burning.

The content of FeTOT in laboratory prepared sinters with biomass does not change considerably compared to the standard (reference – with 100% coke breeze) sinter and is within the interval of about 51–53%. The phase composition (mineralogy) of selected sinters is qualitatively comparable, while the differences are observable in the quantity of individual phases, as shown in **Table 14**. A sinter without biomass contains a higher proportion of iron oxides and sinters with biomass have more silicates and calcium ferrites. Compared to standard sinter, the increase in the share of calcium ferrites can be noticed in selected sinters with biomass. The microstructure of the standard sinter mainly consists of primary magnetite and hematite. Forms of silicoferrites of calcium and aluminum – SFCA are also visible in the microstructure to a small extent. In the microstructure of the sinter with biomass, there is also a visible area of the unsintered surface, which has been identified as lime. Forms of calcium silicates are also visible in the microstructure. The sinter with the substitution of coke breeze by charcoal reached the highest value of reducibility estimated using dR/dt ratio, as seen from **Table 14**. The sinter with the substitution of coke breeze by nutshells has the lowest value of reducibility. Sinters with coke breeze substituted by charcoal and sawdust have a similar reducibility to the reference sinter without any fuel substitution. Higher reducibility relates to sample properties such as its low content of FeO and its high porosity [14], which is related with sinters with the substitution of coke breeze by charcoal and sawdust.

## **2. Conclusions**

In this chapter the properties of iron ores and concentrates were specified. These properties are very important for their efficient processing in the process of sinter and pig iron production. It is important to comprehensively evaluate these raw materials. The evaluation of the properties of iron ores shows that the best ores for blast furnace process have a suitable particle size distribution (10–40 mm), good chemical and mineralogical composition (especially hematite and magnetite,

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

*1.3.2 The influence of carbonaceous fuels on the quality of the sinter and on the economic and ecological parameters of the sintering of iron ores and concentrates*

Starting from an analysis of the considered biofuels (**Table 12**) and proposed methodology for the performance of experiments, coke breeze was partly replaced with a defined quantity of individual biomass types. The materials whose composition is given in the **Tables 5, 10** were used for the experiments. **Tables 13, 14** give characteristics of sinters produced with biomass substitution of coke breeze. It can be seen in some experiments with biomass standard quality parameters on several sinters and lower emissions of COx, NOx and SO2 are achieved. It is possible to substitute about 10–20% of coke breeze by individual types of biomass in the sintering process. Combustion of plant biomass mainly depends on the carbon structure of the cellulose, hemicellulose and lignin, which differ from the amorphous carbon in coke (coke breeze). The maximum temperatures in the sintering process are lower with biomass than with actual coke breeze [11]. Biomass fuels can burn more quickly than coke breeze due to their high porosity and large interface area, while there is a significant increase in the vertical speed of sintering. The combustion of biomass decreases the maximum temperature and abbreviates the holding time at the high temperature. Lower temperatures in the sintered layer observed with the addition of biomass can also be attributed to the condensation of volatile organic compounds [11]. These compounds can eventually be converted into a phase similar to ash and reduce the heat transfer in the direction of burning. The content of FeTOT in laboratory prepared sinters with biomass does not change considerably compared to the standard (reference – with 100% coke breeze) sinter and is within the interval of about 51–53%. The phase composition (mineralogy) of selected sinters is qualitatively comparable, while the differences are observable in the quantity of individual phases, as shown in **Table 14**. A sinter without biomass contains a higher proportion of iron oxides and sinters with biomass have more silicates and calcium ferrites. Compared to standard sinter, the increase in the share of calcium ferrites can be noticed in selected sinters with biomass. The microstructure of the standard sinter mainly consists of primary magnetite and hematite. Forms of silicoferrites of calcium and aluminum – SFCA are also visible in the microstructure to a small extent. In the microstructure of the sinter with biomass, there is also a visible area of the unsintered surface, which has been identified as lime. Forms of calcium silicates are also visible in the microstructure. The sinter with the substitution of coke breeze by charcoal reached the highest value of reducibility estimated using dR/dt ratio, as seen from **Table 14**. The sinter with the substitution of coke breeze by nutshells has the lowest value of reducibility. Sinters with coke breeze substituted by charcoal and sawdust have a similar reducibility to the reference sinter without any fuel substitution. Higher reducibility relates to sample properties such as its low content of FeO and its high porosity [14], which is related with sinters with the substitution of coke breeze by charcoal

In this chapter the properties of iron ores and concentrates were specified. These properties are very important for their efficient processing in the process of sinter and pig iron production. It is important to comprehensively evaluate these raw materials. The evaluation of the properties of iron ores shows that the best ores for blast furnace process have a suitable particle size distribution (10–40 mm), good chemical and mineralogical composition (especially hematite and magnetite,

and sawdust.

*Iron Ores*

**76**

**2. Conclusions**

minimum of carbonate and silicate phases), they are well reducible (Ri60 below 100 min.) and stable after temperature tests (+6.3 mm above 70%). Sinter grade ores and concentrates are characterized as iron ore raw materials with the required granulometry and chemical and mineralogical composition. 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%). The larger grains of sinter grade ore are practically free of impurities and have a relatively homogeneous structure. In addition to iron oxides, the smaller sinter grade ore grains also contain impurities in the form of silicon and aluminum oxides. Undesirable impurities are mainly sulfur, phosphorus, zinc, lead, arsenic, copper, sodium, potassium, which are chemically bound in the minerals of the iron ores.

A new direction in the sintering process is showing the replacement of coke with biomass. It is a more environmentally friendly way of production and practice will show that it will also be more economical in the future. It can be seen in some experiments with biomass standard quality parameters on several sinters and lower emissions of COx, NOx and SO2 are achieved. It is possible to substitute about 10– 20% of coke breeze by individual types of biomass in the sintering process. Properties of input iron bearing and basic raw materials are indeed crucial factors that affect the final quality of sinter, but no less important are the properties and the amount of carbonaceous fuel and high-temperature sintering technology. Progress in the production of pig iron in blast furnaces can be achieved by improving the quality of burden, especially iron ores and sinters. A significant improvement in the performance of blast furnaces is currently achieved by using a burden with a modified chemical and particle size distribution, which allows a more complete use of the chemical and thermal energy of the reducing gas.

## **Acknowledgements**

This research was funded by [APVV] Slovak Research and Development Agency, Slovak Republic number APVV–16-0513.

### **Conflict of interest**

The authors declare no conflict of interest.
