*1.2.1 Material-heat balance and thermodynamic study of sinter production*

The course of processes in the sintered material can be evaluated on the basis of changes in the physical and metallurgical properties of the sintering product. The transformation of the components of a material is related to the decrease in Gibbs free energy. It is possible to calculate the maximum work of reactions, i.e. oxidation reactions, reaction in solid state, reactions during formation of a melt and also reactions taking place during the recrystallization and cooling down of sintering products.

Thermodynamic calculations are thus essential when determining the characteristics of a technological process and they enable one to clarify the formation of the major sintering products. By changing the basic condition of the thermodynamic system, it is feasible to find the optimum operating conditions of the sintering process and minimize the consumption of raw materials and energy [11]. laboratory conditions, it was feasible to specify the created model by the following

• calculation of the quantity and chemical composition of sinter,

output enthalpies of individual components.

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

• prediction of the mineralogical composition of sinter at the sintering

• calculation of the mass and thermal balance on the basis of the input and

experiments [9–11], the results of which can be compared with the calculated thermodynamic models. It is apparent that the model calculations of added fuel in charge are highly correlated with the experimentally determined values, **Figure 9a**. A higher correlation was found for the yield of produced sinter (calculation for

The authors of this chapter have already carried out a large number of laboratory

*1.2.2 Specification of the model of laboratory sintering pot and monitoring of the sintering*

*Comparison between the real and simulated added fuel for sintering (a) and real and simulated amount of the*

The sintering process is thermal process used to transform fine particles of iron ore and concentrate into porous product known as sinter. In the sintering process fuel is in the form of coke breeze (or in the form various types of carbon fuels) used for production of iron-ore sinter [10]. In this sintering process are basic materials mixed, granulated, ignited and fired at a temperatures 1200–1380°C. Sintering of materials can take place under the temperature conditions, which allow binding the particles by reaction in solid state, or under the temperature conditions, which allow the origin of the melt acting as a binding phase after its cooling. In the case of sintering with the

presence of the melt, its quantity and chemical compositions is important.

The process of laboratory sinter production is divided into two stages – cold section and hot section, **Figure 10**. In the cold section, the supply of raw materials, adjustment of grain size to the required piece size, averaging of the chemical composition of materials and granulation of the final sintering burden is ensured. The hot section ensures ignition of the sintering charge, sintering of the sintering charge, removal of hot flue gases (subsequent cleaning) and cooling of the sinter.

parameters [11]:

temperatures,

100 kg of charge), **Figure 9b**.

*process*

**Figure 9.**

*sinter (b).*

**67**

For mathematical modeling the basic chemical reactions with standard Gibbs energy and mass and thermal balance were calculated. Thermodynamic data was obtained from the software HSC Chemistry. HSC Chemistry offers powerful calculation methods for studying the effects of different variables on the chemical system at equilibrium. The aim is to get the simplest approach (using this software to calculate equilibrium) which allows one to predict the output parameters (amounts, chemistry, mineralogical composition, and total heat) based on the initial composition analysis [11].

The mathematical model used by the authors in modeling the sintering process allows the calculation of Gibbs equilibrium diagrams, which characterize the change in the equilibrium composition of reactants and reaction products with changes in temperature. Using Kellogs diagrams of stability areas in the considered systems based on the combustion of carbonaceous fuel in the sintering charge, it is also possible to determine the stability of individual phases at different partial pressures of gaseous components. The modeled systems and the results of thermodynamic calculations can specify the influence of the amount and type of fuel used on oxidation–reduction processes. The said model allows the control of the overall thermal effect of the sintering process during individual instances of experimental laboratory sintering while it employed the prediction of sinter phase composition at the sintering temperatures in the calculations. Since the phase composition of the sinter is determined on samples of sinter after cooling, the computational model should bring a new perspective of the processes taking place during sintering [11].

**Figure 8** shows the global method with modeling the mass and thermal balance of the sintering process. Pursuant to the modeling of the sintering process in the

#### **Figure 8.**

*Scheme presenting the global method with modeling the mass and thermal balance (modified by authors according [11]).*

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

laboratory conditions, it was feasible to specify the created model by the following parameters [11]:


The authors of this chapter have already carried out a large number of laboratory experiments [9–11], the results of which can be compared with the calculated thermodynamic models. It is apparent that the model calculations of added fuel in charge are highly correlated with the experimentally determined values, **Figure 9a**. A higher correlation was found for the yield of produced sinter (calculation for 100 kg of charge), **Figure 9b**.

**Figure 9.**

the major sintering products. By changing the basic condition of the thermodynamic system, it is feasible to find the optimum operating conditions of the sintering process and minimize the consumption of raw materials and energy [11]. For mathematical modeling the basic chemical reactions with standard Gibbs energy and mass and thermal balance were calculated. Thermodynamic data was obtained from the software HSC Chemistry. HSC Chemistry offers powerful calculation methods for studying the effects of different variables on the chemical system at equilibrium. The aim is to get the simplest approach (using this software to calculate equilibrium) which allows one to predict the output parameters (amounts, chemistry, mineralogical

composition, and total heat) based on the initial composition analysis [11].

**Figure 8.**

*Iron Ores*

**66**

*according [11]).*

The mathematical model used by the authors in modeling the sintering process allows the calculation of Gibbs equilibrium diagrams, which characterize the change in the equilibrium composition of reactants and reaction products with changes in temperature. Using Kellogs diagrams of stability areas in the considered systems based on the combustion of carbonaceous fuel in the sintering charge, it is also possible to determine the stability of individual phases at different partial pressures of gaseous components. The modeled systems and the results of thermodynamic calculations can specify the influence of the amount and type of fuel used on oxidation–reduction processes. The said model allows the control of the overall thermal effect of the sintering process during individual instances of experimental laboratory sintering while it employed the prediction of sinter phase composition at the sintering temperatures in the calculations. Since the phase composition of the sinter is determined on samples of sinter after cooling, the computational model should bring a new perspective of the processes taking place during sintering [11]. **Figure 8** shows the global method with modeling the mass and thermal balance of the sintering process. Pursuant to the modeling of the sintering process in the

*Scheme presenting the global method with modeling the mass and thermal balance (modified by authors*

*Comparison between the real and simulated added fuel for sintering (a) and real and simulated amount of the sinter (b).*

### *1.2.2 Specification of the model of laboratory sintering pot and monitoring of the sintering process*

The sintering process is thermal process used to transform fine particles of iron ore and concentrate into porous product known as sinter. In the sintering process fuel is in the form of coke breeze (or in the form various types of carbon fuels) used for production of iron-ore sinter [10]. In this sintering process are basic materials mixed, granulated, ignited and fired at a temperatures 1200–1380°C. Sintering of materials can take place under the temperature conditions, which allow binding the particles by reaction in solid state, or under the temperature conditions, which allow the origin of the melt acting as a binding phase after its cooling. In the case of sintering with the presence of the melt, its quantity and chemical compositions is important.

The process of laboratory sinter production is divided into two stages – cold section and hot section, **Figure 10**. In the cold section, the supply of raw materials, adjustment of grain size to the required piece size, averaging of the chemical composition of materials and granulation of the final sintering burden is ensured. The hot section ensures ignition of the sintering charge, sintering of the sintering charge, removal of hot flue gases (subsequent cleaning) and cooling of the sinter.

#### **Figure 10.**

*Scheme presenting the global method with modeling of the iron sintering process in laboratory conditions in Slovakia.*

Many physico-chemical processes take place during sintering – fuel combustion, drying of components, calcination of carbonates, oxido-reduction processes, melting of grains and solidification.

The authors of this chapter carried out many laboratory experiments [9–13], the results of which can be generalized and used to expand the information database on the use of carbonaceous fuels in the production of sinter. These experiments were carried out in a laboratory sintering pot (LSP), which is located at the Institute of Metallurgy, Faculty of Materials, Metallurgy and Recycling, Technical University of Košice in Slovakia, **Figure 10**.

the combustion zone in the sintered layer during the production of iron ore sinter,

*1.2.3 Technological and ecological aspects of the production of sinters from poor and rich*

As part of the implementation of laboratory experiments on a laboratory sintering pot, the following iron-bearing raw materials were used for sintering,

In the sintering process, standard coke breeze was used as fuel. These raw materials were incorporated in the prepared sintering mixtures, which had a basicity in the range of 1.7–2.8. The next relation was used to calculate the basicity: B = (wt.%CaO + wt.%MgO)/(wt.%SiO2 + wt.%Al2O3). It was therefore the production of highly basic sinters. The produced sinters had content of iron in the range of

In the experiments, the ratio of ferriferous raw materials (Krivbas and Michajlov) – 100% sinter grade ore and 100% concentrate was changed. Concentrate Nižná Slaná was used in mixtures of sinter grade ore/concentrate. In this chapter, primarily the experiments with separate ferriferous raw materials are specified due to the more significant impact of fuel consumption on sinter quality.

**Figure 13**.

**Figure 13.**

**Figure 11.**

**Figure 12.**

*Thermal imaging of a laboratory sintering pot.*

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

*Thermal imaging of the surface of the burden after ignition.*

**Table 10**.

about 46–52%.

**69**

*iron-bearing materials*

*Course of sintering and moving of sintering zone.*

In order to simulate the production of sinter close monitoring of the sintering process is necessary. Laboratory sintering pot is fully equipped with measuring devices and analyzers. The temperature was measured by thermocouples. For the high temperature range in the sintered layer, three thermocouples of the PtRh10-Pt type were used. The flue gas temperature was read at two levels by NiCr-Ni type thermocouple. Chemical composition and temperature of the flue gas were analyzed by TESTO 350 device. The differential pressure was measured by Annubar type probe, which served for calculating the amount of sucked air (or flue gas). All quantities were read at 15-second intervals and collected in a logger. After each experiment, the collected data were transformed into a form usable on a personal computer.

Implementation of an experimental sintering model is also possible using the monitoring of the temperature field of the sintering pot by a thermal imaging camera. With the help of the sensed thermal imaging profile of the sintering pot (**Figure 11**), it is possible to monitor the displacement of the fuel combustion zone in the sintering layer. By sensing the surface of the layer after ignition of the burden, (**Figure 12**), it is possible to monitor the inhomogeneity of the temperature field of the sintered layer. The thermal profile of thermal imaging monitoring indicates different conditions of fuel combustion in the volume of the layer, which may be caused by heterogeneity of fuel distribution. The model of LSP has been innovated by a transparent high-temperature wall that allows visual monitoring of

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

#### **Figure 11.**

Many physico-chemical processes take place during sintering – fuel combustion, drying of components, calcination of carbonates, oxido-reduction processes,

*Scheme presenting the global method with modeling of the iron sintering process in laboratory conditions in*

The authors of this chapter carried out many laboratory experiments [9–13], the results of which can be generalized and used to expand the information database on the use of carbonaceous fuels in the production of sinter. These experiments were carried out in a laboratory sintering pot (LSP), which is located at the Institute of Metallurgy, Faculty of Materials, Metallurgy and Recycling, Technical University of

In order to simulate the production of sinter close monitoring of the sintering process is necessary. Laboratory sintering pot is fully equipped with measuring devices and analyzers. The temperature was measured by thermocouples. For the high temperature range in the sintered layer, three thermocouples of the PtRh10-Pt type were used. The flue gas temperature was read at two levels by NiCr-Ni type thermocouple. Chemical composition and temperature of the flue gas were analyzed by TESTO 350 device. The differential pressure was measured by Annubar type probe, which served for calculating the amount of sucked air (or flue gas). All quantities were read at 15-second intervals and collected in a logger. After each experiment, the collected data were transformed into a form usable on a personal

Implementation of an experimental sintering model is also possible using the monitoring of the temperature field of the sintering pot by a thermal imaging camera. With the help of the sensed thermal imaging profile of the sintering pot (**Figure 11**), it is possible to monitor the displacement of the fuel combustion zone in the sintering layer. By sensing the surface of the layer after ignition of the burden, (**Figure 12**), it is possible to monitor the inhomogeneity of the temperature field of the sintered layer. The thermal profile of thermal imaging monitoring indicates different conditions of fuel combustion in the volume of the layer, which may be caused by heterogeneity of fuel distribution. The model of LSP has been innovated by a transparent high-temperature wall that allows visual monitoring of

melting of grains and solidification.

Košice in Slovakia, **Figure 10**.

computer.

**68**

**Figure 10.**

*Iron Ores*

*Slovakia.*

*Thermal imaging of a laboratory sintering pot.*

**Figure 12.** *Thermal imaging of the surface of the burden after ignition.*

**Figure 13.** *Course of sintering and moving of sintering zone.*

the combustion zone in the sintered layer during the production of iron ore sinter, **Figure 13**.
