Reclaiming of Monoethanolamine (MEA) Used in Post-Combustion CO2-capture with Electrodialysis

AbstractHeat-stable salts (HSS) in amine-based solvents may lead to a long-term performance impairment of post-combustion CO2- capture process system. They can cause a loss of solvent capacity, corrosion, heat exchanger fouling, increased foaming or flooding, etc. The application of electrodialysis (ED) can be a possible cost effective technique for removal of HSS from degraded amine solutions. The paper presents the results of lab-scale ED experiments on HSS removal from synthetic degraded MEA solutions with different HSS content and CO2-loadings. The efficiency of ED-process for reclaiming of MEA solvent is shown. The influence of solvent CO2-loading on the specific energy consumption of ED-process is presented. The lab-scale data have been used for design and manufacturing of a pilot ED plant. Within the OCTAVIUS project it has been planned to test the ED-pilot plant at the EnBW post-combustion CO2 capture pilot plant

Raman Scattering:From Structural Biology to Medical Applications

This is a review of relevant Raman spectroscopy (RS) techniques and their use in structural biology, biophysics, cells, and tissues imaging towards development of various medical diagnostic tools, drug design, and other medical applications. Classical and contemporary structural studies of different water-soluble and membrane proteins, DNA, RNA, and their interactions and behavior in different systems were analyzed in terms of applicability of RS techniques and their complementarity to other corresponding methods. We show that RS is a powerful method that links the fundamental structural biology and its medical applications in cancer, cardiovascular, neurodegenerative, atherosclerotic, and other diseases. In particular, the key roles of RS in modern technologies of structure-based drug design are the detection and imaging of membrane protein microcrystals with the help of coherent anti-Stokes Raman scattering (CARS), which would help to further the development of protein structural crystallography and would result in a number of novel high-resolution structures of membrane proteins—drug targets; and, structural studies of photoactive membrane proteins (rhodopsins, photoreceptors, etc.) for the development of new optogenetic tools. Physical background and biomedical applications of spontaneous, stimulated, resonant, and surface- and tip-enhanced RS are also discussed. All of these techniques have been extensively developed during recent several decades. A number of interesting applications of CARS, resonant, and surface-enhanced Raman spectroscopy methods are also discussed

Gas-Liquid Hollow Fiber Membrane Contactors for Different Applications

Gas-liquid membrane contactors that were based on hollow fiber membranes are the example of highly effective hybrid separation processes in the field of membrane technology. Membranes provide a fixed and well-determined interface for gas/liquid mass transfer without dispensing one phase into another while their structure (hollow fiber) offers very large surface area per apparatus volume resulted in the compactness and modularity of separation equipment. In many cases, stated benefits are complemented with high separation selectivity typical for absorption technology. Since hollow fiber membrane contactors are agreed to be one of the most perspective methods for CO2 capture technologies, the major reviews are devoted to research activities within this field. This review is focused on the research works carried out so far on the applications of membrane contactors for other gas-liquid separation tasks, such as water deoxygenation/ozonation, air humidity control, ethylene/ethane separation, etc. A wide range of materials, membranes, and liquid solvents for membrane contactor processes are considered. Special attention is given to current studies on the capture of acid gases (H2S, SO2) from different mixtures. The examples of pilot-scale and semi-industrial implementation of membrane contactors are given

Interphase Surface Stability in Liquid-Liquid Membrane Contactors Based on Track-Etched Membranes

A promising solution for the implementation of extraction processes is liquid–liquid membrane contactors. The transfer of the target component from one immiscible liquid to another is carried out inside membrane pores. For the first time, highly asymmetric track-etched membranes made of polyethylene terephthalate (PET) of the same thickness but with different pore diameters (12.5–19 nm on one side and hundreds of nanometers on the other side) were studied in the liquid–liquid membrane contactor. For analysis of the liquid–liquid interface stability, two systems widely diverging in the interfacial tension value were used: water–pentanol and water–hexadecane. The interface stability was investigated depending on the following process parameters: the porous structure, the location of the asymmetric membrane in the contactor, the velocities of liquids, and the pressure drop between them. It was shown that the stability of the interface increases with decreasing pore size. Furthermore, it is preferable to supply the aqueous phase from the side of the asymmetric membrane with the larger pore size. The asymmetry of the porous structure of the membrane makes it possible to increase the range of pressure drop values between the phases by at least two times (from 5 to 10 kPa), which does not lead to mutual dispersion of the liquids. The liquid–liquid contactor based on the asymmetric track-etched membranes allows for the extraction of impurities from the organic phase into the aqueous phase by using a 1% solution of acetone in hexadecane as an example

Simulation of the Membrane Process of CO₂ Capture from Flue Gas via Commercial Membranes While Accounting for the Presence of Water Vapor

Carbon capture and storage is one of the potential options for reducing CO2 emissions from coal-fired power plants while preserving their operation. Mathematical modeling was carried out for a one-stage membrane process of carbon dioxide capture from the flue gases of coal-fired power plants using commercial gas separation membranes. Our calculations show that highly CO2-permeable membranes provide similar characteristics with respect to the separation process (e.g., a specific area of membrane and a specific level of electrical energy consumption) despite the significant variation in CO2/N2 and H2O/CO2 selectivity. Regarding the development of processes for the recovery of CO2 from flue gas using membrane technology, ensuring high CO2 permeance of a membrane is more important than ensuring high CO2/N2 selectivity. The presence of water vapor in flue gas provides a higher driving force of CO2 transfer through the membrane due to the dilution of CO2 in the permeate. A cross-flow membrane module operation provides better recovery of CO2 in the presence of water vapor than a counter-current operation

Reclaiming of Amine CO₂ Solvent Using Extraction of Heat Stable Salts in Liquid-Liquid Membrane Contactor

Amine CO2 solvents undergo oxidative degradation with the formation of heat stable salts (HSS). These HSS reduce the sorption capacity of amines and lead to intense corrosion of the equipment. In our work, we propose a membrane-supported liquid-liquid extraction of the HSS from alkanolamines. For this purpose, a hollow fiber membrane contactor was used for the first time. A lab-scale extraction system on the basis of a hollow-fiber liquid-liquid membrane contactor with hollow fiber ultrafiltration polyvinylidenefluoride and polysulfone membranes has been studied. The extraction of the HSS-ions from a 30 wt.% solution of monoethanolamine was carried out using a 0.25–1 M solution of OH-modified methyltrioctylammonium chloride in 1-octanol as an extractant. It has been shown that >90% of HSS ions can be extracted from the alkanolamine solvent within 8 h after extraction. The results obtained confirm the possibility of using membrane extraction with a liquid-liquid membrane contactor for the reclaiming of amine CO2 solvents to increase the general efficiency of carbon dioxide capture

Simulation of Convection–Diffusion Transport in a Laminar Flow Past a Row of Parallel Absorbing Fibers

A numerical simulation of the laminar flow field and convection⁻diffusion mass transfer in a regular system of parallel fully absorbing fibers for the range of Reynolds numbers up to Re = 300 is performed. An isolated row of equidistant circular fibers arranged normally to the external flow is considered as the simplest model for a hollow-fiber membrane contactor. The drag forces acting on the fibers with dependence on Re and on the ratio of the fiber diameter to the distance between the fiber axes, as well as the fiber Sherwood number versus Re and the Schmidt number, Sc, are calculated. A nonlinear regression formula is proposed for calculating the fiber drag force versus Re in a wide range of the interfiber distances. It is shown that the Natanson formula for the fiber Sherwood number as a function of the fiber drag force, Re, and Sc, which was originally derived in the limit of high Peclet numbers, is applicable for small and intermediate Reynolds numbers; intermediate and large Peclet numbers, where Pe = Re × Sc; and for sparse and moderately dense rows of fibers

Gas-Liquid Hollow Fiber Membrane Contactors for Different Applications

Gas-liquid membrane contactors that were based on hollow fiber membranes are the example of highly effective hybrid separation processes in the field of membrane technology. Membranes provide a fixed and well-determined interface for gas/liquid mass transfer without dispensing one phase into another while their structure (hollow fiber) offers very large surface area per apparatus volume resulted in the compactness and modularity of separation equipment. In many cases, stated benefits are complemented with high separation selectivity typical for absorption technology. Since hollow fiber membrane contactors are agreed to be one of the most perspective methods for CO2 capture technologies, the major reviews are devoted to research activities within this field. This review is focused on the research works carried out so far on the applications of membrane contactors for other gas-liquid separation tasks, such as water deoxygenation/ozonation, air humidity control, ethylene/ethane separation, etc. A wide range of materials, membranes, and liquid solvents for membrane contactor processes are considered. Special attention is given to current studies on the capture of acid gases (H2S, SO2) from different mixtures. The examples of pilot-scale and semi-industrial implementation of membrane contactors are given

Membranes Based on PTMSP/PVTMS Blends for Membrane Contactor Applications

In this work, perspective polymeric materials were developed for membrane contactor applications, e.g., for the dissolved oxygen removal from amine CO2 capture solvents. Several polymeric blends based on poly[1-trimethylsilyl-1-propyne] (PTMSP) and poly[vinyltrimethylsilane] (PVTMS) were studied. The gas and water vapor sorption and permeability coefficients for the PTMSP/PVTMS blend membranes at different PVTMS contents (0–100%) were obtained under temperatures of 30 and 60 °C for the first time. As the PVTMS content increases, the O2 and CO2 permeabilities decrease by 160 and 195 times at 30 °C, respectively. The fractional accessible volume of the polymer blends decreases accordingly. The transport of the CO2 capture solvent vapors through the PTMSP/PVTMS blend membranes were determined in thermo-pervaporation (TPV) mode using aqueous monoethanolamine (30%), N-methyldiethanolamine (40%), and 2-amino-2-methyl-1-propanol (30%) solutions as model amine solvents at 60 °C. The membranes demonstrated high pervaporation separation factors with respect to water, resulting in low amine losses. A joint analysis of the gas permeabilities and aqueous alkanolamine TPV data allowed us to conclude that the polymer blend composition of PTMSP/PVTMS 70/30 provides an optimal combination of a sufficiently high oxygen permeability and the pervaporation separation factor at a temperature of 60 °C

Interphase Surface Stability in Liquid-Liquid Membrane Contactors Based on Track-Etched Membranes

A promising solution for the implementation of extraction processes is liquid–liquid membrane contactors. The transfer of the target component from one immiscible liquid to another is carried out inside membrane pores. For the first time, highly asymmetric track-etched membranes made of polyethylene terephthalate (PET) of the same thickness but with different pore diameters (12.5–19 nm on one side and hundreds of nanometers on the other side) were studied in the liquid–liquid membrane contactor. For analysis of the liquid–liquid interface stability, two systems widely diverging in the interfacial tension value were used: water–pentanol and water–hexadecane. The interface stability was investigated depending on the following process parameters: the porous structure, the location of the asymmetric membrane in the contactor, the velocities of liquids, and the pressure drop between them. It was shown that the stability of the interface increases with decreasing pore size. Furthermore, it is preferable to supply the aqueous phase from the side of the asymmetric membrane with the larger pore size. The asymmetry of the porous structure of the membrane makes it possible to increase the range of pressure drop values between the phases by at least two times (from 5 to 10 kPa), which does not lead to mutual dispersion of the liquids. The liquid–liquid contactor based on the asymmetric track-etched membranes allows for the extraction of impurities from the organic phase into the aqueous phase by using a 1% solution of acetone in hexadecane as an example