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Review of solvent based carbon-dioxide capture technologies
Kathryn A. MUMFORD, Yue WU, Kathryn H. SMITH, Geoffrey W. STEVENS
Front. Chem. Sci. Eng.. 2015, 9 (2 ): 125-141.
https://doi.org/10.1007/s11705-015-1514-6
Currently, a large proportion of global fossil fuel emissions originate from large point sources such as power generation or industrial processes. This trend is expected to continue until the year 2030 and beyond. Carbon capture and storage (CCS), a straightforward and effective carbon reduction approach, will play a significant role in reducing emissions from these sources into the future if atmospheric carbon dioxide (CO2 ) emissions are to be stabilized and global warming limited below a threshold of 2 °C. This review provides an update on the status of large scale integrated CCS technologies using solvent absorption for CO2 capture and provides an insight into the development of new solvents, including advanced amine solvents, amino acid salts, carbonate systems, aqueous ammonia, immiscible liquids and ionic liquids. These proposed new solvents aim to reduce the overall cost CO2 capture by improving the CO2 absorption rate, CO2 capture capacity, thereby reducing equipment size and decreasing the energy required for solvent regeneration.
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CFD simulation on shell-and-tube heat exchangers with small-angle helical baffles
Minhua ZHANG,Fang MENG,Zhongfeng GENG
Front. Chem. Sci. Eng.. 2015, 9 (2 ): 183-193.
https://doi.org/10.1007/s11705-015-1510-x
Shell-and-tube heat exchanger with helical baffles is superior to that with segmental baffles in reducing pressure drop, eliminating dead zone and lowering the risks of vibration of tube bundle. This paper focused on the small-angle helical baffles that have been merely reported in open literature. These baffles are noncontinuous helical baffles with a helix angle of 10° to 30°, and their shapes are 1/4 ellipse, 1/4 sector and 1/3 sector. To assess the integrative performance, α /?p is employed, and the calculated results show that among the three baffle shapes the heat exchangers with a 1/4 sector helical baffle have the lowest pressure drop. At β = 10° and 20°, 1/4 sector helical baffle heat exchangers show the best integrative performance; at β = 30°, 1/4 ellipse and 1/4 sector helical baffle heat exchangers perform almost the same. For the study of helix angles, we found that 30° has the best integrative performance at low mass flow rate, almost the same as 20° at high mass flow rate.
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Functionalized activated carbon for the adsorptive removal of perchlorate from water solutions
Rovshan MAHMUDOV, Chinglung CHEN, Chin-Pao HUANG
Front. Chem. Sci. Eng.. 2015, 9 (2 ): 194-208.
https://doi.org/10.1007/s11705-015-1517-3
Two types of activated carbon, namely, Filtrasorb 400 and Nuchar SA, were functionalized by quaternary ammonium salts (quats), as to enhance perchlorate adsorption. Results showed that the adsorption of quats on Nuchar SA increased with increase in chain length (hydrophobicity) of quats. Filtrasorb 400, however, had limited uptake of long-chain quats such as dodecyltrimethylammonium and hexadecyltrimethylammoium (HDTMA). Results indicated that perchlorate removal by the functionalized activated carbon was directly related to the chain length of the modifying quats. Perchlorate removal by functionalized activated carbon increased with increase in chain length of the modifying quats and became less pH-dependent. Modified Nuchar SA had higher overall perchlorate removal capacity than the modified Filtrasorb F400, but was more strongly affected by pH than Filtrasorb 400. Activated carbon treated with HDTMA exhibited the best perchlorate removal capacity among all quats studied. Results indicated that tailoring the activated carbon surface with HDTMA rendered the activated carbon surface positively charged, which resulted in substantial increase in perchlorate removal compared to unfunctionalized activated carbons.
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Phosphorous removal from wastewater by lanthanum modified Y zeolites
Weikang ZHANG, Ye TIAN
Front. Chem. Sci. Eng.. 2015, 9 (2 ): 209-215.
https://doi.org/10.1007/s11705-014-1448-4
The adsorption capacities of Y zeolite and La (III)-modified Y zeolite were studied. A series of La(III)-modified Y zeolites with different La/Y zeolite mass ratios were characterized by X-ray diffraction, X-ray fluorescence and Brunauer-Emmett-Teller surface area analysis. Batch experiments were conducted to evaluate the effects of various experimental parameters, such as pH, ionic strength, coexisting anions (C O 3 2 - , Cl- , S O 4 2 - and N O 3 - ) and temperature, on the phosphate adsorption. The capacity of the La (III)-modified Y zeolite to remove phosphate increased as the La/Y zeolite mass ratio increased and after 4 h, a phosphate removal efficiency of 95% was achieved for a La/Y zeolite mass ratio of 0.10. The equilibrium adsorption isotherm data correlated better to the Langmuir model than the Freundlich model and the data followed a pseudo-second-order kinetic equation.
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