Apr-2023

DMX CO2 capture technology: an industrial demonstration

An innovative CO2 capture absorption process technology offers improved performance and reduced energy requirements compared with existing solvent.

Christian Streicher
Axens

Article Summary

All scenarios anticipating carbon neutrality by 2050, led by those of the International Energy Agency (IEA), confirm the need to shift to cleaner energy systems to achieve net-zero emissions through a wide range of solutions. Among the transformations proposed for the energy sector, heavy industries and transport, carbon capture and storage is ranked among the top solutions to reach this goal.

Carbon capture is thus due to play a fundamental role in achieving the Net Zero Emissions scenario in 2050: indeed, as stated in IEA's 2020 Global Status of CCS report, "Without CCS, net-zero is practically impossible"

CO2 capture by amine scrubbing is currently considered a suitable technology for sectors with large, fixed CO2 emissions due to its robustness, adaptability, and capability of producing a highly concentrated CO2 stream, suitable for transporting and storing or reuse. Some significant challenges need, however, to be addressed for the industrial deployment of this technology, among which reducing the process energy penalty is critical. Other challenges, such as limiting solvent and VOC emissions, long-term process stability and footprint reduction, also need to be addressed. The DMX Process technology presented in this article provides improved solvent formulation and process configuration to answer those challenges.

Technology presentation
The DMX Process is a CO2 capture process developed by IFP Energies nouvelles (IFPEN), based on CO2 absorption by a demixing solvent. The DMX Solvent consists of a mixture of two organic compounds in an aqueous solution which is demixing under certain conditions of temperature and CO2 partial pressure. Figure 1 illustrates the main steps of the Process. The flue gas (or other types of gas) to be treated is contacted with the solvent in a counter-current absorber. The rich solvent from the absorber bottom is preheated in a lean/rich heat exchanger, which creates conditions for demixing of the solvent. This demixing allows phase separation in a decanter into a lean solvent phase which can be directly recycled to the absorber and a rich solvent phase fed to a thermal regenerator.

The DMX Solvent has a high cyclic capacity (much higher than standard monoethanolamine (MEA), for instance), and only the CO2-rich phase needs to be regenerated, which contributes to reducing the heat requirement for thermal regeneration. Another beneficial feature of the Solvent is its high thermal stability, which allows regeneration at higher temperatures than amine solvents such as MEA. This allows CO2 recovery at higher pressure (up to 5 barg) and contributes to significant CO2 compression cost savings. The Solvent also offers high chemical stability in the presence of oxygen, which is beneficial for all kinds of flue gas applications.

The performance of the DMX Solvent has been assessed through initial laboratory studies and small-scale pilot plant tests through previous collaborative projects like Octavius (Octavius, 2022) and Valorco (Valorco, 2022). Thanks to the Solvent's properties, the Process has great potential for reducing the energy penalty and cost of CO2 capture for a large variety of applications. Compared to the first-generation absorption process using 30 wt% MEA, the DMX Process allows a reduction of 30% on the energy penalty and cost of CO2 capture.

The DMX Solvent is less corrosive than MEA, allowing the use of carbon steel as the principal material, which also reduces the Capex compared to other first-generation solvents.

The performance characteristics of the Process, based on the development carried out at IFPEN, are summarised in Table 1.
DMX appeared as the best rated second-generation solvent for CO2 capture in previous benchmarking studies, such as the one presented by Prachi Singh (IEAGH) at GHGT-11 (Singh and Brilman, 2012).

The DMX Process was originally developed for CO2 capture from coal power station flue gases and gas from steel manufacturing, on which specific experiments have been conducted. However, it is also suitable for capturing CO2 from other emitters, such as refinery FCC units and steam methane reformers (SMR), waste incinerators, cement plants, district heating, and the production of electricity from biomass.

The Process is well adapted to CO2 capture on industrial smoke or industrial gas when the CO2 partial pressures are low to medium. The DMX technology has been developed and optimised to capture CO2 at partial pressures in the range of 0.1-1 bara in flue gas.

Development history
The DMX Process has already undergone 10 years of development from laboratory scale (Raynal et al., 2010) to global optimisation in the power (Raynal et al., 2014, Broutin et al., 2016), and steel industries (Dreillard et al., 2016), and has now reached Technology Readiness Level 4 (TRL4), as shown in Figure 2.

The Octavius project, developed in partnership with ENEL, was aimed at demonstrating integrated concepts for zero-emission power plants covering all components needed for power generation from coal as well as CO2 capture and compression. The Valorco project, coordinated by ArcelorMittal and funded by ADEME, was aimed at reducing and valorising CO2 emissions from the steel industry. Within those projects, experimentation was carried out at IFPEN in Solaize, France, on a small-scale pilot unit (0.2 kgCO2/h). It included parametric studies using representative synthetic gas and a long-duration test (1,500 hours) with the addition of impurities present in real gases to measure the degradation of the DMX Solvent.

The main conclusions drawn from those preliminary studies were:
- That DMX Solvent appears significantly less energy intensive than MEA 30 wt%
- For steel mill applications, it is more cost effective to capture the CO2 directly from the blast furnace gas, rather than from the power station flue gas, due to higher CO2 partial pressures in blast furnace gas.