Decarbonisation Technology - February 2023

Capture option

Separation

Method

Applications

technology Post-conversion • Absorption by

• Amine-based solvent e.g. monoethanolamine

Power plants; iron and steel industry; cement industry; oil refineries

chemical solvents

(MEA), b diethanolamine (DEA), and hindered amine (KS-1)

• Alkaline solvents, e.g. NaOH and Ca(OH) 2 • Ionic liquids • Amine-based solid sorbents • Alkali earth metal-based solid sorbents, e.g. CaC0 3 • Alkali metal carbonate solid sorbents, e.g. Na 2 CO 3 and K 2 CO 3 • Porous organic frameworks - polymers • Polymeric membranes, e.g. polymeric gas

• Adsorption by solid sorbents

No application reported

Power plants

•Membrane separation

Power plants; natural gas sweetening

permeation membranes b • Inorganic membranes, e.g. zeolites • Hybrid membranes

• Cryogenic separation • Cryogenic separation • Pressure/vacuum • Zeolites b

Power plants

Power plants; iron and steel industry Power plants (IGCC)

swing adsorption

• Activated carbon b • Selexol, Rectisol

Pre-conversion • Absorption by

physical solvents • Absorption by chemical solvents • Adsorption by porous organic frameworks • Separation of oxygen from air

• Amine-based solvent e.g. MEA

Ammonia production

• Porous organic frameworks membranes

Gas separations

Oxy-fuel combustion

• Oxy-fuel process

Power plants; iron and steel industry; cement industry c Power plants

• Chemical looping combustion • Chemical looping reforming

Power plants; syngas production and upgrading

a Mature technology. b Commercially available. c May become available in the long term (>2030).

Table 1 Carbon capture options and applications

Source: Cuellar-Franca and Azapagic, 2014

have shown incredible potential for CO 2 absorption, have negligible vapour pressure, have adjustable structures, and are eco- friendly (Yan, et al., 2018), (Hasib-ur-Rahman, Siaj and Larachi, 2010). Techniques used in other commercial gas separations, such as solid sorbents, membranes, and cryogenic separation, may be applied to carbon capture. Electrochemical carbon capture and the co- production of hydrogen with carbon capture are two alternative paths under development. Application of ‘green/new solvents’ A solvent can be the key to a good chemical process, as it determines the solubility and the stability of excited states, thus affecting the potential-energy curves of activation. Over the past two decades, the applications of green chemistry have led to improvements in the capabilities of conventional solvents, with a new class of so-called master solvents, also termed ‘green’ or ‘designer’ solvents (Nematollahi and

Carvalho, 2019). By definition, an ideal fully sustainable green solvent would not have an ecological impact at any stage and would ease process conditions, making them milder and more sustainable. Such solvents are likely to provide productivity and economic and environmental benefits (Hessel, et al ., 2021). Water is considered to be nature’s ‘green solvent’ for its bio-catalytic processes. Green solvents considered include ILs and supercritical CO 2, as well as deep eutectic, theomorphic and fluorous solvents. Some green solvents, such as ILs, are widely used commercially, while others, such as flouros and supercritical CO 2, have more specific uses. Figure 1 summarises green solvents for CO 2 sorption and CCUS technologies. Ionic liquids (ILs) as green solvents ILs comprise a large category of salts that, due to differences in their cation and anion sizes, are normally liquids at a temperature less