DOI: 10.3303/CET24111121 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper Received: 25 May 2024; Revised: 20 June 2024; Accepted: 19 September 2024 
Please cite this article as: Schiattarella V., Moioli S., 2024, Application of CO2 Removal to Reduce Emissions in a Steel Plant, Chemical 
Engineering Transactions, 111, 721-726  DOI:10.3303/CET24111121 
  

 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 111, 2024 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.cetjournal.it 

Guest Editors: Valerio Cozzani, Bruno Fabiano, Genserik Reniers 

Copyright © 2024, AIDIC Servizi S.r.l. 

ISBN 979-12-81206-11-3; ISSN 2283-9216 

Application of CO2 Removal to Reduce Emissions in a Steel 

Plant 

Valentina Schiattarella, Stefania Moioli* 

GASP - Group on Advanced Separation Processes & GAS Processing, Dipartimento di Chimica, Materiali e Ingegneria 

Chimica “Giulio Natta”, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italia 

stefania.moioli@polimi.it 

The steel industry is one of the major contributors to CO2 emissions due to its energy intensive processes. Steel 

plants operate by converting iron ore into steel through processes like the blast furnace method, resulting in 

substantial emissions, primarily from the combustion of fossil fuels and chemical reactions. In order to manage 

this challenge, Carbon Capture and Storage (CCS) technologies play a pivotal role in mitigating emissions. 

These technologies capture CO2 at the source and prevent it from entering the atmosphere. This work takes 

into consideration a French steel plant, producing 6.6 million tons of steel annually, and aims at designing the 

process of chemical absorption with a 30 wt.% MonoEthanolAmine (MEA) aqueous solution by optimizing it to 

reduce the thermal requirement for regeneration. The parameters that have been optimized are the height of 

the absorption column, the lean loading, the height and the pressure of the regeneration column and the 

temperature of the solvent entering in the regeneration column. Then, an economic analysis and the comparison 

of this technology with another technology for the CO2 removal, the polymeric membrane method, has been 

carried out in order to understand the pros and the cons also taking into account the CO2 purity and the CO2 

recovery ratio that can be achieved with the two technologies. 

1. Introduction 

In the early 19th century, the world annual steel production had been only a few million tons. After the 

breakthrough of new technologies, converter processes, and open hearths, the production increased and 

exceeded 30 Mt in 1900 by reaching its record in 1979 with 749 Mt. The growth then stagnated due to economic 

crises and political changes until the turn of the millennium, when it reached 850 Mt in 2000 (Holappa, 2020). 

Since then, the steel production has doubled and the record has been reached in 2022 with 1,885 Mt (WSA, 

2023). About 70% of global steel is produced through the Blast Furnace and Basic Oxygen Furnace method 

(BF+BOF), which is also responsible for 95% of global iron production (IEAGHG, 2013). The remaining 30% is 

produced via Direct Reduced Iron (DRI) method (Chang et al., 1993), where the steel or solid iron from a DRI 

process is melted by electric power in an Electric Arc Furnace (EAF) (Thompson and Si, 2014, Quader et al., 

2016). Ironmaking is an extremely energy-intensive process, utilizing coal as the main primary energy source 

though the use of natural gas is increasing (Jampani et al., 2019) because of its being the cleaner fossil source 

(Pellegrini et al., 2015, Spatolisano et al., 2023) providing less environmental impact than other fossil fuels. It 

has been estimated that 7–9% of direct emissions from the global use of fossil fuels (WSA, 2020) are related to 

ironmaking. The specific emission has been estimated equal to 1.85 t of CO2/t of steel, corresponding to 3.3 Gt 

CO2 in a year for a steel production rate of 1.8 Gt/y (Holappa, 2020). Nowadays, several technologies are 

available to reduce process plant emissions, such as Carbon Capture, Utilization and Storage (CCUS), that 

have started to be considered also for processes producing biogenic CO2, as in Waste-to-Energy (WtE) plants 

(Pellegrini et al., 2023, Moioli et al., 2024). One of the main techniques for capturing CO2 is the chemical 

absorption with aqueous solution of amines (Pellegrini et al., 2020) that are characterized by a very high 

efficiency though the most commonly used amines are toxic and subjected to degradation. Alternative solvents 

to amines for chemical absorption are being studied and also technologies based on different operations are 

under consideration, as membranes. They are thought more environmentally friendly as for the operation, 

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though being subjected to plasticization at high temperatures and to insufficient thermal and chemical stability 

(Yeo et al., 2012). 

In a steel plant, blast furnace gases are estimated to contain about 70% of the CO2 emitted and are the most 

relevant for volumetric flowrate (Ramírez-Santos et al., 2017). Though there is in general an interest towards 

the energy transition from fossil fuels to renewables (Spatolisano and Pellegrini, 2021), the production of gases 

containing CO2 is part of the steelmaking process. Previous works in the literature considered CCS applied to 

steelmaking plants (Goto et al., 2011, Hooey et al., 2013, Arasto et al., 2014), and a review on the integration 

of carbon capture technologies in the Blast Furnace and Basic Oxygen Furnace (BF-BOF) (Perpiñán et al., 

2023) has been published last year. This work presents a detailed assessment of the process design of the 

chemical absorption with a 30% wt. MonoEthanolAmine (MEA) aqueous solution (already considered for the 

CO2 removal from flue gases of power plants (Moioli and Pellegrini, 2020)), that was not found in the previously 

published papers and that aims at better understanding the main factors contributing to the economics of the 

process to remove the carbon dioxide present in the blast furnace gas. An optimization has been carried out 

together with an economic analysis and then the amine-based technology has been compared to the membrane 

technology. 

2. Simulation of the chemical absorption process 

The process design has performed by simulating the chemical absorption process with a 30 wt.% 

monoethanolamine (MEA) aqueous solution in Aspen Plus® V11 software with the ENRTL-RK model, modified 

with the PC-SAFT to describe the vapor phase (Gross and Sadowski, 2000), and by considering the columns 

as rate-base units. 

The blast furnace gas has a flowrate of 550,000 Nm3/h at 1.05 bar and 35 °C with the composition presented in 

Table 1, as the one studied by Ramirez-Santos et al. (2017). This gaseous stream (FLUEGAS) is treated in an 

absorption column with the solvent stream (LEANIN) entering at 1.2 bar and 40 °C. 

Table 1: Blast furnace gas composition (Ramírez-Santos et al., 2017) 

Gas Unit FLUEGAS 

CO2 [% mol] 21.59 

CO [% mol] 23.45 

H2 [% mol] 3.65 

N2 [% mol] 46.51 

H2O [% mol] 4.20 

Ar [% mol] 0.6 

 

The process for the CO2 removal includes three packed columns (Sulzer Mellapak 250X), a process-process 

heat exchanger, a heat exchanger with cooling water and two pumps. The blast furnace gas is fed to the 

absorber in which is treated with the liquid stream of solvent in a counter current configuration. The purified gas 

leaving the absorber (GASOUT), enters the washing section in order to decrease the emissions of MEA. Make-

up water is added to the washing section, in order to control the amine emissions. The CO2-rich solution 

(RICHOUT) is pumped to a process-process heat exchanger that increases its temperature in order to favor the 

desorption. Then, the CO2-rich solution at high temperature (RICHIN) is fed to a regeneration column to separate 

the absorbent and CO2. The concentrated CO2 (CO2OUT) gas leaves the system while the remaining CO2-lean 

solution (LEANOUT) is partially cooled down in the process-process heat exchanger (LEANOUTMT), mixed 

with a make-up (LEANINLP), fed to another heat exchanger and finally it is ready to be recycled back to the 

absorber. Figure 1 shows a schematic of the process. 

3. Results and discussion 

3.1 Design of the process 

In order to investigate the influence of lean loading and packing height on the energy requirement, the packing 

height of the absorption column has been varied from 10 to 26 m and for each of these heights different values 

of the lean loading have been simulated. In the simulations the impurity of 0.6% Ar has been considered as 

0.6% O2, with no influence on the results. In order to reach the desired recovery ratio of CO2, fixed to 90%, it is 

necessary to modify the flowrate of the solvent according to the actual value of the lean loading. At low lean 

loading, more energy is needed to strip the CO2 from the solvent, although less solvent is circulated. At high 

lean loading, a greater solvent flowrate is required, so the energy to heat the solvent to the reboiler temperature 

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is the main contributor the reboiler heat duty (Figure 2a) and the Thermal Energy Requirement (TER) is 

characterized by a minimum, that varies with the height of packing in the absorber. 

 

 

Figure 1: Process flow diagram of the MEA-based chemical absorption 

 

a) b) 

Figure 2: Variation of the reboiler duty with a) the absorber packing height and the lean loading and b) the 

packing height of the regeneration column 

The objective of the regeneration column section is to regenerate the solvent and extract CO2 from the rich 

solution by generating a vapour stream rich in water in the reboiler connected to the bottom of the column. For 

the optimum values of the absorber packing height and lean loading, the regeneration column packing height 

has been varied from 6 to 14 m. However, the reboiler duty increased significantly with lower packing heights 

(Figure 2b). So, 12 m is the optimal height that has been chosen for the regeneration column, because it is the 

first value that allows the reboiler duty to be nearly constant. Based on the process conditions reached after the 

optimization of regeneration column packing height, the regeneration column pressure has been varied in the 

range of 0.2 - 2.5 bar (absolute). All the other settings (absorber and regeneration column packing height, lean 

loading and absorber diameter) for the plant operation have been kept constant. As consequence of the variation 

of the regeneration column pressure, the mass flowrate of the absorbed CO2 and thus the regeneration energy 

requirement change. Increasing the regeneration column pressure leads to a rise in the regeneration column 

temperature as can be seen in Figure 3a and the equilibrium isotherms of the CO2 solubility shift to lower 

loadings at constant CO2 partial pressure which means that the regeneration is easier and the regeneration is 

more effective with increasing the regeneration column pressure. Therefore, the reboiler duty for the solvent 

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R
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Lean loading [mol CO2/mol MEA]

H=26 m

H=22 m

H=20 m

H=18 m

H=16 m

H=12 m

H=10 m

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regeneration decreases with a higher regeneration column pressure as can be seen in Figure 3b because less 

stripping steam is required for the separation task. The specific energy requirement to heat up the solvent 

flowrate is increasing with an increase in the regeneration column pressure because of the higher temperature 

at the reboiler. By considering the energy required by the reboiler, 1.8 bar has been chosen as the optimal 

pressure. 

 

a) b) 

Figure 3: a) increase of the LEANOUT temperature as the regenerator pressure increases due to the different 

equilibrium conditions; b) decrease of the reboiler duty as regenerator pressure increases due to the less 

required stripping steam. 

Based on the process conditions reached after the optimization of the pressure of the regeneration column, the 

solvent temperature has been varied in the range from 30 °C to 50 °C with all the other plant settings constant. 

In this study the influence of the solvent temperature on the reboiler duty has also been analyzed, though not 

reported here for reasons of space. As a result, the reboiler duty decreases as the solvent temperature increases 

because of the decrease in the amount of CO2-rich solution that reaches the regenerator, which in turn is due 

to a greater vaporization of the water in the absorber. The optimized values for the process based on absorption 

are collected in Table 2. For these operating conditions, the absorption column operating at 1.02 bar is 

characterized by a temperature trend from 35 °C to a bulge and the regeneration column has a temperature 

profile from 30 °C at the top to 119.30 °C at the bottom. 

Table 2: Design parameters of the optimized process 

 Unit Value 

Absorber height [m] 18 

Lean loading [-] 0.19 

Regenerator height [m] 12 

Regenerator pressure [bar] 1.8 

Solvent temperature [°C] 35 

 

3.2 Economic analysis 

The two main contributions to the plant total costs are the capital costs, related to the construction of a new 

chemical plant or modifications to an existing plant, and the operating costs involved in the daily operation of 

the plant. The Bare Module Cost accounts for both direct and indirect costs related to the project. Direct costs 

include the material needed for installation (piping, insulating material, structural support, etc.) and the cost of 

the equipment. Indirect costs include transport and insurance costs to the plant site with taxes, labour costs for 

installation and costs for engineering and supervision of the project. Also the estimation of the Cost of 

Manufacturing (COM) is required before the economic feasibility of a proposed process is assessed. There are 

many different factors affecting the cost of manufacturing a chemical product, that can be classified into three 

main categories being direct manufacturing costs, fixed manufacturing costs and general expenses. The Cost 

of Operating Labor is part of the COM. The computation of the operational expenses associated with a utility 

supply is performed by accounting only for the costs associated to the utility generation according to Turton et 

al. (2012) (Turton et al., 2012). The raw material used in this simulation are demi water and the solvent (MEA), 

with their costs estimated on the basis of the values excerpted from Moioli et al. (2019) (Moioli et al., 2019) and 

Mistral Industrial Chemicals (MIC). Moreover, large seasonal price fluctuations may exist for certain chemicals, 

60

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0.0 0.5 1.0 1.5 2.0 2.5 3.0

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e

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 [

°C
]

Regenerator pressure [bar]

0

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1000

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3500

4000

0.0 0.5 1.0 1.5 2.0 2.5 3.0

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Regenerator pressure [bar]

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and therefore the average price over a period of several months should be considered in this case. Furthermore, 

the raw material cost includes the cost of solvent make-up due to losses and degradation. The investment costs 

related to the main units result to be equal to 25.39 M$ for the absorber, 13.17 M$ for the regeneration column, 

8.67 M$ for the heat exchangers and 0.82 M$ for the pumps. The costs are annualized supposing a 25 year of 

life plant (Table 3). 

Table 3: Total cost 

Plant Total Cost Unit Value 

Plant Life [y] 25 

Fixed Capital Investment (FCI) [M$] 96.07 

Fixed Capital Investment [M$/y] 3.84 

Cost Of Manufacturing (COM) [M$/y] 27.21 

Total Cost during all the period [M$/y] 31.05 

Cost of removed CO2 [$/t CO2] 18.69 

FCI per ton of removed CO2 [$/t CO2] 2.31 

COM per ton of removed CO2 [$/t CO2] 16.38 

 

3.3 Comparison with membrane technology 

The main characteristics (CO2 recovery, CO2 purity in the CO2-rich stream and total cost per ton of CO2 

removed) of the chemical absorption technology has been compared with the ones obtained with the polymeric 

membrane (Table 4) and presented by Ramirez-Santos et al. (2017). Differently from chemical absorption, the 

membrane technology is generally more suitable from bulk removal operations since the separation is based 

on a difference in a rate of permeation rather than on an absolute barrier to one component (Kohl and Nielsen, 

1997). Though the chemical absorption has the disadvantage of using MEA as a solvent as it turns out to be 

corrosive and degrades at high temperatures and concentrations, this technology is less expensive and it is not 

characterized by modularity, favoring its application for high gaseous flowrates, like the one in the steel plant 

analyzed in this work. In the chemical absorption process the flowrate of solvent increases for a higher target 

CO2 recovery (Moioli, 2023), with an increase of the costs, as in the case of the CO2 removal process based on 

membranes. However, the CO2 purity of the CO2-rich stream exiting from the regeneration section does not 

vary, differently from the ones reported in (Table 4) for the membrane technology, that significantly decreases. 

Table 4: Cost comparison 

Technology CO2 recovery [%] CO2 purity [%] Cost  Source 

Chemical absorption 90 95 18.69 [$/t CO2] This work 

Membrane 90 91.14 23.10 [€/t CO2] Ramirez-Santos et al. (2017) 

Membrane 95 87.91 25.70 [€/t CO2] Ramirez-Santos et al. (2017) 

Membrane 99 81.05 33.20 [€/t CO2] Ramirez-Santos et al. (2017) 

4. Conclusions 

This work has focused on the study of CO2 removal within the context of a steel plant. The utilization of chemical 

absorption, using MEA as the solvent, has been analyzed and optimized through simulation, offering insights 

into the performance and the economic viability of this technology. The parallel investigation, based on a case 

study of the same steel plant utilizing polymeric membranes for CO2 removal, provides a valuable comparative 

perspective from which it is possible to outsource that, for the industrial plant considered in this work, the 

chemical absorption process can provide a reduction of greenhouses gas emissions at lower cost favoring the 

application of CO2 removal to this type of production plants that emit relevant amounts of greenhouse gas. The 

future developments of this work could be the sensitivity analysis of the input variables and the study of CO2 

removal through an absorption process in which the solvent is more environmentally friendly than the MEA one. 

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