Producing climate-neutral raw materials with sustainable energy

Fuel from wind and water: Porsche and international partners of the operating company Highly Innovative Fuels (HIF) have been producing synthetic fuel since December 2022 in the power-to-X pilot plant Haru Oni in Chile.
Image: Porsche

A publication issued by the German Society for Chemical Engineering and Biotechnology (Dechema) about carbon sources and their integration into power-to-X added value chains focuses on options for separating and using carbon dioxide for sustainable production pathways. The technology is an important part of decarbonising the metal industries.

Steel production is an energy-intensive industrial process and therefore emits CO2, which is a potential source of carbons for PtX.
Image: worldsteel

Steel industry – global projects
The project Carbon2Chem in Germany is intended to produce 75 l/d of raw methanol from blast furnace gases from the steel works of the thyssenkrupp Steel Europe AG in Duisburg. The test phase will continue until May 2024, after which industrial production is supposed to start.
ADNOC has completed the CCUS plant in Al-Reyadah in 2016, which has the capacity to capture 800,000 t of CO2 each year from a production plant owned by Emirates Steel in the United Arab Emirates. The company has plans to increase its separation capacity to approx. 5 million tons per year until 2030.
In another example, Arcelor Mittal Ghent has put a pilot plant into operation which captures about 300 kg of CO2 from the blast furnace every day and transforms it into ethanol. Primetals (Mitsubishi Heavy Industries Engineering) supplied the capture technology and supported the technical studies.

Aluminium industry – potential for carbon capture
Another significant emitter of CO2 and therefore a candidate for carbon capture and utilisation is the aluminium industry. There are three kinds of emissions from aluminium production that were identified:
- Around 62 % are indirect emissions which stem from the use of electricity. These emissions could be avoided through direct use of renewable electricity.
- Around 15 % are direct process emissions from the use of carbon anodes for smelting aluminium. The use of inert anodes is an alternative which leads to avoiding these emissions, however, this technology is still under development and not commercially available.
- Around 16 % are direct energy emissions from burning fossil fuels to directly generate the necessary high temperatures. The use of green hydrogen or other low-emission fuels could contribute to decreasing these emissions.
Hydro Aluminium, for example: Apart from recycling scrap aluminium, the Norwegian producer of aluminium is working on complete decarbonisation by introducing new technologies like carbon capture and storage as well as developing a way to produce primary aluminium with zero emissions.

Carbon dioxide as raw material
Carbon dioxide can serve as a source of carbon for many climate-friendly products made with power-to-X technologies (PtX). The Dechema report “Carbon for Power-to-X – Suitable CO2 sources and integration in PtX value chains” describes point sources and state-of-the-art capture methods. It is the result of Dechema’s cooperation with the International PtX Hub, which supports the development of sustainable power-to-X and hydrogen markets in countries like Morocco, South Africa and Argentina

Carbon-based PtX routes are based on three fundamental elements: Identifying the carbon source, enriching CO2 through separation or capturing processes and the use of CO2 to create a product with added value.
Image: Dechema

The PtX concept combines many different innovative technologies
Climate-neutral raw materials made with sustainable energy – that is what power-to-X (PtX) promises. The PtX concept combines many different innovative technologies to create added value chains which are supplied by sustainable energies. For this reason, PtX is regarded as a relevant contribution to the industrial energy transformation. For many PtX routes, however, carbon is needed to replace raw materials and energy sources which conventionally use fossil resources.
Carbon dioxide (CO2) is a suitable source of carbons, as it can serve as a starting point for the production of fuels, polymers and numerous other basic chemicals. In a current report, which was published in the context of the International PtX Hub, the Dechema German Society for Chemical Engineering and Biotechnology identifies point sources and describes several technologies for capturing CO2. “Today’s value chains of the most commonly used products are defined to a high degree by the petrochemical industry, which supplies basic chemicals like methanol”, says co-author Luisa López. “These molecules, which are based on fossil raw materials, are currently being produced by the megaton. PtX now allows us to create alternative routes of production for these important compounds based on CO2.”

The main cause of the rise in CO2, which is harmful to the climate, are combustion processes. Hydrocarbons react with oxygen and create CO2 and water.
Image: Dechema

Carbon dioxide – mainly considered a waste product today
Currently, CO2 is mainly considered a waste product in many sectors. Worldwide, about 37 gigatons of CO2 are emitted into the atmosphere every year. Although there are efforts underway to minimise these emissions, the remaining CO2 flows could be used as raw materials for PtX production. The report shows that CO2 can be retrieved from the energy and industrial sectors, from biogenic processes, waste and sewage as well as from the atmosphere. Sources which can be traced back to fossil resources have an additional impact on sustainability, and possible lock-in effects must also be taken into consideration. Therefore, CO2 sources with a closed carbon cycle are better suited to reaching sustainability goals. “Biogenic sources and direct air capture (DAC) can serve as sustainable sources of CO2 and they achieve a higher level of acceptance through their closed carbon cycle”, says co-author Dr Chokri Boumrifak. “Biomass is, however, much sought-after in other sectors, and its capacities are limited. DAC, as a theoretically unlimited source, needs large amounts of energy in comparison to other sources, and using it at a large technical scale is still very cost-intensive. Therefore, unavoidable CO2 emissions from the industrial sector should be considered as an additional point source.”

Overview of carbon capture methods.
Source: Dechema

Highly developed technologies for capturing and cleaning CO2
The publication ‘Carbon for Power-to-X’ offers an overview of technologies for capturing and cleaning CO2. These technologies are already well developed, and their application depends on factors like the quality of the gas composition, the efficient use of energy and profitability. Amine gas treatment is the technology that is furthest developed among all carbon capture methods, and it is already being used commercially on a large scale. Several other capture methods, namely cryogenic capture, pressure swing adsorption, vacuum pressure swing adsorption, membrane separation and combustion using the chemical loop process, are used in carbon capture.
For combustion processes, how to apply carbon capture is demonstrated using different methods. The most simple method is direct extraction of CO2 from exhaust gases. There are much more sophisticated methods which either pre-treat the fuel by gasification or burn it with pure oxygen in order to capture CO2 with a higher purity. CO2 can also be directly captured from the atmosphere.
The captured CO2 can be used to produce chemicals, either through already existing production routes or through newly implemented processes. Among the primary production routes using CO2 as a raw material are the synthesis of methanol (as a pre-product for fuels, polymers, acids, etc.), Fischer-Tropsch (production of fuels, waxes, naphtha and methane) and carbonylation processes (for production of Ibuprofen, acrylic glass, etc.). The modification of these production routes to fit a PtX concept requires new technologies to transform CO2 into each required raw material. Among the furthest developed application cases for PtX are power-to-liquid (PtL) processes for the production of synthetic hydrocarbons, for example fuels. According to Dechema, how CO2 will be integrated in future depends on aspects of regulation which clarify which source of carbons can be declared sustainable, and on infrastructure measures to provide carbons where they are needed. These vagaries aside, CO2 will continue to be a key component in promoting PtX products as an alternative to fossil-based raw materials and fuels.
Source: Dechema

Literature
https://dechema.de/-p-20480537-EGOTEC-9e92b4556d8c80b48b939d58642f5b5d/_/CO2-R_03-04-24_f.pdf