CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 70, 2018 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Timothy G. Walmsley, Petar S. Varbanov, Rongxin Su, Jiří J. Klemeš 
Copyright © 2018, AIDIC Servizi S.r.l. 

ISBN 978-88-95608-67-9; ISSN 2283-9216 

Modelling of Trace Material Flow Distribution in a Melter 

Gasifier based on Thermodynamic Multiphase Equilibrium 

Calculations 

Andreas Spanlanga,*, Bernd Weissb, Johann Wurmb, Walter Wukovitsc 

aResearcher, K1-MET GmbH, Stahlstrasse 14, 4020 Linz, Austria 
bProcess engineer, Primetals Technologies GmbH, Turmstrasse 44, 4031 Linz, Austria 
cUniv. Ass., TU Wien,  Getreidemarkt 9, 1060 Wien, Austria 

 andreas.spanlang@k1-met.com 

In combination with a complex global market environment, the iron and steel industry is dealing with increasing 

demands for reduction of environmental and greenhouse emissions. Alternative iron making technologies such 

as Corex® and Finex® can offer solutions for these challenges. The melter gasifier is the central unit operation 

of these well-established alternative iron making processes. Both offer considerable advantages with respect to 

economic characteristics and environmental emissions.  

Similar to the conventional iron making process of the blast furnace route, a variety of different input materials 

is required for these processes including coal, coke, lump or fine ore, iron ore pellets as well as limestone and 

dolomite. Most of these raw materials also carry minor amounts of unwanted compounds such as alkali or zinc-

based species. The presence of these materials inside a melter gasifier can lead to instability, problematic 

process conditions and refractory damages. A better understanding of the distribution of these problematic 

species is therefore of great importance to plant manufacturers and operators. A variety of different multiphase 

reactions are responsible for the distribution of trace materials within the melter gasifier. In order to get a better 

understanding of the complex nature of these reactions, a thermodynamic investigation was carried out using 

calculation routines of HSC Chemistry and FactSage.  

Based on the findings of this investigation, a multi-zone model was developed using the simulation platform of 

the gPROMS ModelBuilder®. The model is separated into distinct reaction zones across the height of the melter 

gasifier to depict the main iron ore reduction process as well as the governing reactions of trace material 

components. Validation of the model was carried out using reference data of existing plants. The model 

described in this work is used to analyse the behaviour of trace materials within a melter gasifier. Due to the 

highly integrated material flows of the Corex® and Finex® iron making processes, the impact on their operational 

characteristics can be investigated as well. Through this it is possible to optimise the raw material input of these 

processes, potentially leading to reduced fuel demand and environmental emissions. 

1. Introduction 

Iron making can be classified into two different process routes for production of metallic iron. The first category 

of processes is known as direct reduction processes such as Midrex®, HYL® or Finmet®. In these processes 

the oxygen content of iron oxide contained in the raw material is removed leading to the solid product called 

direct reduced iron or DRI (Babich et al., 2008). The second category includes production technologies used to 

produce metallic iron in liquid form, so-called pig iron or hot metal. Of these processes, only a limited number 

was established on an industrial scale. The traditional blast furnace process is by far the most important process 

route while Corex® and Finex® (see Figure 1) represent the only two technological alternatives which are 

commercially available (Hasanbeigi et al., 2014).  

                                

 
 

 

 
   

                                                  
DOI: 10.3303/CET1870114 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Spanlang A., Weiss B., Wurm J., Wukovits W., 2018, Modelling of trace material flow distribution in a melter gasifier 
based on thermodynamic multiphase equilibrium calculations , Chemical Engineering Transactions, 70, 679-684  DOI:10.3303/CET1870114   

679



 

Figure 1: Corex® and Finex® process flow sheets; 1) melter-gasifier, 2) reduction shaft, 3) hot gas cyclone,  

4) process gas scrubber, 5) hot compacted iron bin, 6) fluidized bed reactor (Wieder, et al., 2009) 

Corex® and Finex® are so-called smelting reduction processes which can produce pig iron directly with non-

coking coal. In addition to this they are more flexible with respect to raw material quality and operation conditions 

while having a lower environmental impact than the conventional blast furnace route. Iron ore reduction and 

smelting are separated as reduction of iron ore is moved to a pre-reduction stage represented by a reduction 

shaft or fluidised bed reactors. Gasification of coal to produce reducing gas and heat for smelting as well as 

direct reduction of the pre-reduced iron ore to metallic iron are located in the so-called melter-gasifier 

(Flickenschild, et al., 2012). This melter-gasifier (see Figure 2) therefore acts as the final reduction stage of both 

the Corex® and Finex® processes (Almpanis-Lekkas et al, 2014) 

 

Figure 2: Melter-gasifier device (Almpanis-Lekkas et al, 2014) 

In general iron ores used for iron making contain several trace elements such as potassium, sodium or zinc. If 

such elements transfer to gaseous form in high temperature parts of the blast furnace, ascend to low 

temperature zones and condense, a circle is formed which may lead to accumulation inside the blast furnace. 

The accumulation of trace elements in a blast furnace may lead to decreasing productivity, increasing reducing 

agent demand and refractory wear or even to unstable process conditions (Babich et al., 2008). Due to their 

similarity, a comparable situation applies for the melter-gasifier device (Pichler, 2017).  

FINEX® COREX® 

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2. Thermodynamic investigation 

To get a better understanding of the complex nature of trace element reactions and circulating flows inside of 

iron making reactors, Pichler (2017) carried out a thermodynamic investigation of the stability of specific alkali 

components under typical conditions in a blast furnace and a melter-gasifier. The results of this work were 

specific multi-stage models describing the distribution of alkali-components in each reaction zone. Figure 3 gives 

an overview of the structure of the corresponding blast furnace model. The underlying thermochemical 

equilibrium calculations were carried out using the thermochemical program FactSage (Bale et.al., 2016).  

 

Figure 3: Reaction zones of alkali model and general overview of input and output streams (Pichler, 2017) 

The prevalent process conditions like gas composition, temperature and pressure which are required for these 

equilibrium calculations were based on industry and literature data. Both models include alkali components of 

potassium and sodium as well as halogenic components based on chlorine and fluorine. This allows for the 

prediction of alkali enrichment in specific zones and visualization of corresponding material flows inside the iron 

making devices (Pichler et al. 2016).  

As an alternative software program for thermochemical calculations, HSC Chemistry has been used to describe 

iron ore reduction by Zhang et al. (2013) as well as circulating alkali components by Iljana et al. (2013). It was 

also used to provide enthalpy data for the development of a black box melter-gasifier model (Almpanis-Lekkas, 

2012) and other metallurgical unit operations (Almpanis-Lekkas, 2015). To corroborate the results the 

thermochemical modelling approach described by Pichler (2017), the calculated equilibrium compositions of 

different reaction zones of the multi-stage blast furnace model have been compared to results derived from the 

equilibrium module of HSC Chemistry.  

 

Figure 4: Comparison of equilibrium molar flows calculated by FactSage and HSC Chemistry 

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Results of this comparison are given in Figure 4 for selected zones. For zones representing lower parts of the 

blast furnace (zone 7), HSC Chemistry delivers results comparable to the reference values of FactSage. 

Equilibrium zones representing higher parts of the blast furnace (zones 1 and 2) also show similar results for 

liquid and solid components. However, in the case of gaseous components significant differences are visible. 

The deviations observed for gaseous components are related to differences of the underlying enthalpy and 

entropy databases of FactSage and HSC Chemistry.  

3. Modelling 

The melter-gasifier model described in this work is based on a multi-zone model which was developed for the 

simulation platform of the gPROMS ModelBuilder® (Almpanis-Lekkas, 2015). This model was furthermore used 

as a basis to investigate the applicability of FactSage based hot metal / slag equilibrium calculations (Almpanis-

Lekkas et al., 2016). In general, the model is divided into four main reaction zones which are distributed along 

the height of the melter-gasifier. A specific set of chemical reactions is allocated to each of these zones 

corresponding with the actual chemical and metallurgical reactions taking place. The material streams between 

the zones follow a counter-current gas/solid flow scheme. Reactions like drying, pyrolysis, carbon gasification 

and iron ore reduction are included by means of reaction degrees. Equilibrium formulations for gas and solid/gas 

reactions like the homogeneous water-gas-shift reaction and the Boudouard reaction are implemented through 

chemical equilibrium formulations. Empiric element conversion and distribution factors are used for the depiction 

of three-phase metallurgical reactions. 

Based on the results of the thermodynamic investigations described in Chapter 2, the melter-gasifier multi-zone 

model has been extended by several reactions to depict the behaviour of trace elements such as potassium, 

sodium, chlorine and zinc. For each zone it is assumed that the gaseous trace components fully ascend to 

higher zones with the general gas and dust stream while the solid and liquid trace components are descending 

to lower reaction zones with the general solid stream. Figure 5 gives an overview of the additional reactions 

which have been added to each zone of the model. Starting at the bottom zone of raceway and hearth, silicon 

decomposition and direct reduction of alkali components are located leading to liquid alkali oxide and elemental 

alkali gas. Part of the elemental alkali gas reacts with carbon and nitrogen to form gaseous alkali cyanides. 

Volatile chlorine entering the melter-gasifier through the tuyères due to injection of substitute reducing agents 

like pulverised coal (PCI) is forming gaseous hydrogen chloride. In the lower charbed zone solid alkali halides 

are transformed to their gaseous form. Several reactions are added to the upper charbed zone where gaseous 

alkali gas and alkali cyanides form solid alkali carbonates with the carbon dioxide of this zone. The produced 

alkali carbonates are however immediately decomposed forming solid alkali oxides. Parts of these alkali oxides 

react with gaseous hydrogen chloride and hydrogen fluoride to form solid alkali halides. Additionally, solid zinc 

oxide is reduced with carbon monoxide leading to elemental zinc gas. In the current version of the model there 

are no additional reactions allocated to the dome zone. 

 

Figure 5: Trace element reactions of the extended melter-gasifier multi-zone model 

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4. Simulation results 

The preceding model has been validated using data for melter-gasifier operation under different process 

conditions (Almpanis-Lekkas, 2015). The reference values were provided by Primetals Technologies for two 

Corex® processes with different production capacities (C2000, C3000) and for a Finex® process (F2_0M). 

Based on this data, the extended melter-gasifier model was used in this work to calculate the flow distribution 

of the newly added trace components.  

Figure 6 illustrates the calculated mass specific distribution of potassium components across the zones of the 

melter-gasifier model for the F2_0M scenario. Solid raw materials appear to be responsible for the main input 

of potassium related species. On the other hand, the main amount of potassium is discharged as part of the 

slag produced in the process. The highest amount of potassium components can be found at the interface 

between lower and upper charbed due to the counter current flow of gaseous and solid matter. Figure 7 shows 

a comparison of elemental potassium and chlorine flow distribution for the F2_0M, C3000 and C2000 scenarios. 

All three processes lead to a similar distribution pattern in the case of chlorine. For F2_0M however, a minor 

input is visible at the raceway and hearth zone due to injection of pulverised coal which contains small amounts 

of chlorine.  

 

Figure 6: Potassium flow distribution for F2_0M process scenario 

 

Figure 7: Comparison of elemental potassium and chlorine flow distribution for different process scenarios 

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In contrast to chlorine, the differences between the three process scenarios are much larger for the flow 

distribution of potassium. It can be observed, that the input stream of F2_0M exceeds those for C2000 and 

C3000 significantly. This leads to a larger specific output of potassium through slag. The amount of circulating 

matter is increased as well. However, all flow distributions qualitatively appear to follow a similar pattern. 

5. Conclusions and outlook 

The visualization of the flow distribution of specific trace components presented in this work allows for a deeper 

understanding of their behavior in metallurgic processes. With the current version of the model it is possible to 

simulate the flow path of several trace components inside the melter-gasifier. This enables a better assessment 

of their potential influence on operation in different areas of the reactor.  

The extended melter-gasifier model represents the first step of an ongoing effort to simulate the behaviour of 

trace elements in metallurgic processes within gPROMS ModelBuilder®. In the future, further developments are 

envisaged to be made regarding the implementation of trace elements such as lead, mercury, nickel, cobalt and 

copper. In addition to this, other metallurgical devices like a blast furnace, reduction shaft, electric arc furnace 

and basic oxygen converter should be extended in a similar manner. This would lay the ground for a 

comprehensive analysis of trace element flow distributions along all major iron and steel production routes. 

Acknowledgments 

The authors gratefully acknowledge the funding support of K1-MET GmbH, metallurgical competence center. 

The research program of the competence center K1-MET is supported by COMET (Competence Center for 

Excellent Technologies), the Austrian program for competence centers. COMET is funded by the Federal 

Ministry for Transport, Innovation and Technology, the Federal Ministry for Science, Research and Economy, 

the province of Upper Austria, Tyrol, and Styria, the Styrian Business Promotion Agency. 

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