CO2 absorption rate in semi-aqueous monoethanolamine. (8th June 2018)

• Record Type: Journal Article
• Authors: Yuan, Ye; Rochelle, Gary T.
• Is Part Of: Chemical engineering science. Volume 182(2018)
• Page Start: 56
• Page End: 66
• Publication Date: 2018-06-08
• Subjects: Monoethanolamine -- CO2 capture -- Semi-aqueous -- Amine activity -- Physical solubility -- Mass transfer modeling; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2018.02.026
• Languages: English
• ISSNs: 0009-2509

Abstract

Highlights: CO2 absorbs faster into MEA/NMP (or CARBITOL™)/water than MEA (aq) or PZ (aq). CO2 physical solubility and MEA volatility were measured in CO2 -MEA-NMP-water. A kinetic model was built in MATLAB® to explain the rate behavior. Amine/physical solvent/water is promising for CO2 capture. The volatility and viscosity of the solvent may limit its usefulness. Abstract: Post-combustion CO2 capture using amine scrubbing is the most promising technology to reduce CO2 emissions from coal- or gas-fired power plants. Increasing CO2 absorption rate (kg ′) reduces the absorber capital cost, which is the cost center of the capture plant. By partially replacing water with N-methyl-2-pyrrolidone (NMP) in 7 m (30 wt%) aqueous monoethanolamine (MEA), the CO2 absorption rate (kg ′) is significantly enhanced because of lower CO2 loading/higher free MEA at the same CO2 partial pressure (P∗CO2 ), greater CO2 physical solubility, and greater MEA activity. At 40 °C, in the operating range of 100–5000 Pa P∗CO2, the average kg ′ of 7 m MEA in 3 water/1 NMP, 1 water/3 NMP, and 1 water/19 NMP is 1.1 times, 2 times, and 5 times that of 7 m aqueous MEA, respectively. CO2 physical solubility, solvent viscosity, and MEA activity were measured. A kinetic model was built in MATLAB® to better understand the mass transfer of CO2 into semi-aqueous MEA (MEA-NMP-water). The model suggests that the diffusion and reaction of CO2 into aqueous MEA can be approximated by pseudo-first-order (PFO) behavior and adding NMP causes deviation from PFO by the depletion of MEA at the surface. The semi-aqueous solvent provides an excellent rate of CO2 absorption, but the increased viscosity reduces normalized capacity and the volatility of the physical solvent must be addressed.