https://doi.org/10.1016/j.ijggc.2022.103771
“Solvent development has historically focused on reducing the enthalpy of absorption, increasing the absorption capacity, and enhancing the reaction kinetics by blending and synthesizing new amines. However, this approach has not yielded any major breakthroughs, because, as illustrated in Fig. 1, the same physical property space has been repeatedly explored for over a century. Methanol- and hot potassium carbonate-based separation processes were deployed in the late 19th century for acid gas separation in order to produce carbonic acid (Henry, 1904). By the 1930s, this process was adopted for natural gas sweeting (Bottoms, 1930; Allen and Arthur, 1933) using aqueous alkanolamines, including monoethanolamine (MEA) and diethanolamine (DEA). The development of solvent technologies continued, with sterically hindered amines and activated blends introduced in the 1970s (Appl et al., 1982; Sartori and Savage, 1983) and aimed at increasing the absorption capacity and reaction rate compared to the single-amine solvents, e.g., blending sterically hindered 2-amino-2-methyl-1-propanol (AMP) with rate-promoter piperazine (PZ). A common characteristic of the solvent classes enumerated here is their relatively dilute nature – they are overwhelmingly composed of water, introducing an inherent inefficiency to this technology.”
“Fig. 1. Timeline of solvent development including total heat of absorption, kinetics (colour scale; red = fast, blue = slow), and VLE (size; high capacity = large, low capacity = small). Comparison at pCO2=10 kPa and 40 °C. List of abbreviations and data sources are described in Supplementary Material. The text labels with rectangular borders correspond to the amine solvents evaluated in this study in terms of capture costs (Fig. 5).”
“It is therefore crucial to clarify if further solvent development is capable of achieving anticipated cost reduction targets (US Department of Energy, 2020), or if setting unachievable targets is essentially a potential distraction from the urgent need to deploy CCS technology. In this contribution, we present a thought-experiment which identifies the limits of solvent development via a hypothetical ideal solvent. To understand how physical properties of solvents can translate to cost reductions, we evaluated MEA, (primary), DEA (secondary), MDEA (tertiary), AMP (sterically hindered), PZ (heterocyclic (di)amines), and CESAR1 (performance benchmark) as representative solvents, as they cover a wide range in kinetics, vapour–liquid equilibrium (VLE), and enthalpy of absorption. This study focuses on the application of amine-based absorption systems for post-combustion capture of CO2 from a range of flue gases with CO2 concentration ranging between 1 mol% and 30 mol%.”