Chemical utilisation of steel mill gases for the production of sustainable chemicals and fuels (Carbon2Chem®)

This innovative approach consists in the chemical utilisation of steel mill gases (SMGs) to produce sustainable chemicals and fuels, especially methanol, ammonia and sustainable aviation fuel (SAF). This is developed by thyssenkrupp in the project Carbon2Chem® to demonstrate the technology on a pilot scale at thyssenkrupp’s steel plant in Duisburg. The project is financed (€ 50 millions) by the Federal Ministry of Research, Technology and Space in Germany.

TECHNICAL DESCRIPTION
A general process flow diagram for the chemical utilisation of SMGs to produce methanol is provided in the supplementary information attached.
Briefly, in the Carbon2Chem® approach, both blast furnace gas (BFG) and basic oxygen furnace gas (BOFG) serve as carbon source for production of chemicals and fuels. In the case of BFG, a gas cleaning or CO2 capture step is carried out (CO2 removal) while for the BOFG only a cleaning step is necessary. In addition, post combustion capture (PCC) of CO2 from the powerplant is also considered as a carbon source. The gas cleaning, which can typically be adsorptive, absorptive or reactive, is used to remove any trace compounds in the gases which might affect the activity of the catalysts involved or the product quality. The CO2 capture is one of several different approaches that can be used to change the composition of the main components in the gas, which can involve pressure-swing-adsorption, water gas shift or CO2 adsorption in a solvent, typically amines.
The lack of H2 to provide synthesis gas from BFG, BOFG and captured CO2 can be compensated by adding H2 produced by water electrolysis using renewable energy or separated from the COG using a pressure swing absorption (PSA) process. The COG consists of about 60 % H2 and 20 % CH4 providing a limited but suitable source of H2. The off gas from the PSA process obtained after H2 separation contains mainly CH4 and can be used as an energy source in the power plant.
The production of methanol from capture of CO2 from BFG and PCC from power plant was investigated within the Carbon2Chem® project. The advantage of the direct use of BFG and BOFG as carbon source to produce methanol is the significantly lower energy demand compared to the production of methanol from CO2. The Carbon2Chem® concept not only reduces climate change impacts via not combusting SMGs but also avoids the use of fossil resources in the production of methanol using conventional methods based mainly on natural gas feedstock.

DEGREE OF MATURITY
The conversion of SMGs to chemical products comprises different individual process steps, which are combined together.
• The cleaning of the SMGs is estimated to have a TRL of 7/8. Several experimental campaigns in the Carbon2Chem® technical centre have proven its ability to reliably remove trace compounds from different steel mill gases and their mixtures in the order of 50-100 Nm3/h over thousands of operating hours.
• The gas conditioning steps like water gas shift, CO2 removal or methanation have been carried out in Thyssenkrupp’s worldwide state-of-the-art chemical plants with feed gases of different composition, the TRL is estimated to be around 8.
• The chemical synthesis of ammonia is a well characterised process with high TRL (9).
• The methanol synthesis varies between 7 and 9, depending on the type of feed gas which is used.

BARRIERS TO IMPLEMENTATION
The regulatory framework for the production of sustainable fuels such as biofuels, RFNBOs (Renewable Fuels of Non-Biological Origin), RCFs (Recycled Carbon Fuels) and low carbon fuels (LCFs) is regulated through several EU Directives and Regulations. However, in the case of the production of synthetic fuels using BFG and BOFG, adapting the regulatory framework could provide more incentives for investing in technologies such as the one developed in the Carbon2Chem® project.
Key issues that may need to be clarified are as follows:

 The fact that the Delegated Act (EU) 2023/1185 only allows the use of captured fossil CO2 for production of RFNBOs, RCFs and LCFs until 2041 might make the construction of plants for production of synthetic fuels using captured fossil CO2 economically unattractive, as chemical plants are operated over more than twenty years and the availability of feedstocks must be ensured.
 The direct conversion of BFG and BOFG is permitted after 2040, but the quantification of CO2 emissions and distribution between the steel mill and the fuel production is not sufficiently regulated. These gases also contain CO, which is not defined as a greenhouse gas and can be converted to zero rated RFNBOs and RCF according to Commission Implementing Regulation (EU) 2024/2493. This means that the emissions of CO-based RFNBOs and RCFs are currently not counted either for the steel mill or for the fuel producer. This results in an underestimation of total CO2 emissions because emissions from CO based fuels are not counted anywhere.

Basic information about the technique

Participant Companies