Thermally rearranged poly(benzoxazole-co-imide) hollow fiber membranes for CO₂ capture

Woo, K.T.,Lee, J.,Dong, G.,Kim, J.S.,Do, Y.S.,Jo, H.J.,Lee, Y.M. Elsevier Scientific Pub. Co 2016 Journal of membrane science Vol.498 No.-

Thermally rearranged poly(benzoxazole-co-imide) (TR-PBOI) hollow fiber membranes were fabricated from a hydroxyl polyimide-co-polyimide (HD5) precursor containing equal molar amounts of non-TR-able DAM and TR-able HAB. A wide variety of spinning conditions were optimized in order to improve the gas permeation properties. A high bore flow rate (DI water) led to lowered gas permeation properties due to the generation of a dense, thick skin layer. The shear rate contributed significantly to manipulate the polymer chain packing density during spinning, therefore, CO<SUB>2</SUB> permeance was critically enhanced in low shear rate. The addition of co-solvent (propionic acid) and pore forming agent (PEG 200) was shown to improve the gas permeation properties. The TR-PBOI hollow fiber membrane fabricated under optimal spinning conditions exhibited an excellent CO<SUB>2</SUB> permeance of 560 GPU and CO<SUB>2</SUB>/N<SUB>2</SUB> ideal selectivity of 16.8. A TR-PBOI hollow fiber module was successfully fabricated with an effective area of 106cm<SUP>2</SUP> for the mixed-gas permeation tests with a ternary gas mixture containing 14% CO<SUB>2</SUB>, 6% O<SUB>2</SUB>, and 80% N<SUB>2</SUB>. The results showed a permeate CO<SUB>2</SUB> concentration around 50% and CO<SUB>2</SUB> permeance of 400 GPU at a pressure ratio of 10.

Selection of suitable aqueous potassium amino acid salts: CH₄ recovery in coal bed methane via CO₂ removal

Park, S.,Song, H.J.,Park, J. Elsevier Scientific Pub. Co 2014 Fuel processing technology Vol.120 No.-

In this study, we identified suitable potassium amino acid salt absorbents for CO<SUB>2</SUB> removal for purposes of recovering CH<SUB>4</SUB> from coal bed methane (CBM). We checked critical concentrations of each blended solvent that did not produce any precipitate during CO<SUB>2</SUB> absorption. From among these, we selected 8 solvents that gave no precipitate. The selected absorbents were assessed in terms of their CO<SUB>2</SUB> loading capacity and absorption/desorption rate in comparison with monoethanolamine (MEA) through a screening test. We regulated a 10% CO<SUB>2</SUB> balance in CH<SUB>4</SUB>, because the feed gas was assumed to approximate the CBM. From the results obtained, it seems that 4M SAR, 1.5M ALA+1M PZ, and 1.5M SER+1M PZ are good CO<SUB>2</SUB> absorbents, because their cyclic CO<SUB>2</SUB> loading (0.223, 0.208, and 0.18mol, respectively, of CO<SUB>2</SUB>/mol of absorbent) is higher than those of other selected solvents (e.g., 4M GLY+1M PZ, which has the lowest cyclic CO<SUB>2</SUB> loading). In addition, we checked that the high concentration of amino acid salts interrupted CO<SUB>2</SUB> absorption, decreasing the solubility. These solvents also have a relatively high surface tension at 25<SUP>o</SUP>C (70.6; 73.3; 68.6mN/m), when compared with pure water it (72.0mN/m). We therefore conclude that the suggested absorbent is adequate for use in the CO<SUB>2</SUB> removal process.

Improving power and desalination capabilities of a large nuclear power plant with supercritical CO₂ power technology

Lee, Won Woong,Bae, Seong Jun,Jung, Yong Hun,Yoon, Ho Joon,Jeong, Yong Hoon,Lee, Jeong Ik Elsevier Scientific Pub. Co 2017 Desalination Vol. No.

<P><B>Abstract</B></P> <P>To response to the increasing demands for clean water, a large pressurized water reactor (PWR) with a desalination capability has been studied and demonstrated its potential so far. However, the electricity production of the large nuclear reactor decreases by 10% due to steam bypass for desalination. In this study, the authors evaluate the possibility of a large PWR with a capability of producing both electric power and clean water by using the supercritical CO<SUB>2</SUB> (S-CO<SUB>2</SUB>) Brayton cycle technology. The S-CO<SUB>2</SUB> power technology is adopted to minimize the decrease in the electricity production capacity due to desalination process. Two concepts which replace the existing steam based power conversion system with a S-CO<SUB>2</SUB> Brayton cycle were proposed. The first concept is that the low pressure steam turbine section of the power conversion system is replaced with the S-CO<SUB>2</SUB> Brayton cycle. The second concept is that the whole steam based power conversion system is replaced with the S-CO<SUB>2</SUB> Brayton cycle. Several S-CO<SUB>2</SUB> cycle options were considered in terms of power production and the desalination capacity and conducted a comparative analysis of selected layouts and the optimal operating conditions of the suggested layouts were identified.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The applicability of S-CO<SUB>2</SUB> Brayton cycle for a large nuclear power plant is assessed. </LI> <LI> Various S-CO<SUB>2</SUB> Brayton cycles are evaluated for co-generating nuclear power plant. </LI> <LI> The co-generating nuclear plant performance is improved with the S-CO<SUB>2</SUB> power cycle. </LI> </UL> </P>

PEDOT-PSS embedded comb copolymer membranes with improved CO₂ capture

Lee, J.H.,Jung, J.P.,Jang, E.,Lee, K.B.,Hwang, Y.J.,Min, B.K.,Kim, J.H. Elsevier Scientific Pub. Co 2016 Journal of membrane science Vol.518 No.-

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS) is a widely used conductive polymer in various electronic devices. Here we report the first use of PEDOT-PSS to enhance CO<SUB>2</SUB> capture performance of all-polymeric membranes. Specifically, an amphiphilic comb copolymer, i.e. poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate)-poly(oxyethylene methacrylate) (PBEM-POEM or PBE), was synthesized to disperse PEDOT-PSS chains. Isolated and aggregated PEDOT-PSS transformed into an interconnected network structure upon combination with PBE, due to specific interactions. Incorporation of PEDOT-PSS generated a facile pathway for enhanced diffusive transport, resulting in improved CO<SUB>2</SUB> and N<SUB>2</SUB> permeability. However, CO<SUB>2</SUB> permeability increased more significantly due to enhanced CO<SUB>2</SUB> solubility, resulting in slight increase in CO<SUB>2</SUB>/N<SUB>2</SUB> selectivity. The PBE membrane containing PEDOT-PSS 5wt% showed the highest performance with a CO<SUB>2</SUB> permeability of 59.6 Barrer and CO<SUB>2</SUB>/N<SUB>2</SUB> selectivity of 77.4. The performance of PBE/PEDOT-PSS membranes was very close to the 2008 Robeson upper bound and much higher than those of PBE/PEDOT, PBE/PSS and commercial PEBAX membranes.

A single catalyst of aqueous Co^III for deodorization of mixture odor gases: A development and reaction pathway study at electro-scrubbing process

Govindan, M.,Moon, I.S. Elsevier Scientific Pub. Co 2013 Journal of hazardous materials Vol.260 No.-

A constant generation of aqueous Co<SUP>III</SUP> active catalyst and its utility on various odor gases deodorization at electro-scrubbing process is the primary investigation. The Co<SUP>III</SUP> activation and regeneration for continuous use is established by electrochemical undivided cell in H<SUB>2</SUB>SO<SUB>4</SUB> medium. The generated aqueous Co<SUP>III</SUP> is then applied to simultaneous deodorization of simulated odor gases, namely, ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan, and acetaldehyde, for municipal waste treatment plant emissions. The electro-scrubbing process results indicated that deodorization is almost complete at a low gas flow rate of 30Lmin<SUP>-1</SUP>. FTIR and pH studies demonstrated that amine compounds are removed via complex formation with H<SUB>2</SUB>SO<SUB>4</SUB> and Co<SUP>III</SUP>. In the case of sulfur compounds, deodorization of methyl mercaptan and hydrogen sulfide are removed by the Co<SUP>III</SUP>-MEO (Co<SUP>III</SUP>-mediated electrocatalytic oxidation) process via the formation of acetic acid as intermediate and SO<SUB>4</SUB><SUP>2-</SUP> as a product. Also, acetaldehyde deodorization results obtained by pH, total acidity and CO<SUB>2</SUB> analyses evidence the process follow Co<SUP>III</SUP>-MEO. The constant generation of aqueous active Co<SUP>III</SUP> and an electro-scrubbing process offers promise as a means of removing odorous waste gases from gaseous emissions.

Utilization of rice husk ash as silica source for the synthesis of mesoporous silicas and their application to CO₂ adsorption through TREN/TEPA grafting

Bhagiyalakshmi, M.,Yun, L.J.,Anuradha, R.,Jang, H.T. Elsevier Scientific Pub. Co 2010 Journal of hazardous materials Vol.175 No.1

Mesoporous MCM-41, MCM-48 and SBA-15 were synthesized using Rice husk ash (RHA) as the silica source and their defective Si-OH sites were functionalized by 3-cholropropyltrimethoxysilane (CPTMS) which was subsequently grafted with amine compounds, Tris(2-aminoethyl)amine (TREN) and Tetraethylenepentamine (TEPA). X-ray powder diffraction (XRD) and BET results of the parent mesoporous silica suggested their closeness of structural properties to those obtained from conventional silica sources. CO<SUB>2</SUB> adsorption of branched amine TREN and straight chain amine TEPA at 25, 50 and 75<SUP>o</SUP>C was obtained by Thermogravimetric Analyser (TGA) at atmospheric pressure. TREN grafted mesoporous silica showed 7% of CO<SUB>2</SUB> adsorption while TEPA grafted mesoporous silicas showed less CO<SUB>2</SUB> adsorption, which is due to the presence of isolated amine groups in TREN. TREN grafted mesoporous silicas were also observed to be selective towards CO<SUB>2</SUB>, thermally stable and recyclable. The order of CO<SUB>2</SUB> adsorption with respect to amount of amine grafting was observed to be MCM-48/TREN>MCM-41/TREN>SBA-15/TREN.

Performance of a slurry bubble column reactor for Fischer@?Tropsch synthesis: Determination of optimum condition

Woo, K.J.,Kang, S.H.,Kim, S.M.,Bae, J.W.,Jun, K.W. Elsevier Scientific Pub. Co 2010 Fuel processing technology Vol.91 No.4

The CO conversion and selectivity to C<SUB>1</SUB> and C<SUB>11</SUB> wax products over Co/Al<SUB>2</SUB><SUB>3</SUB>as well as Ru/Co/Al<SUB>2</SUB><SUB>3</SUB>Fischer-Tropsch (F-T)catalysts were investigated by varying reaction temperature (210-250 <SUP>o</SUP>), system pressure (1.0-3.0 MPa), GHSV (1000-6000 L/kg/h), superficial gas velocity (1.7-13.6 cm/s) and slurry concentration (9.09-26.67 wt.%) in a slurry bubble column reactor (0.05 m diameterx1.5 m height) to determine the optimum operating conditions. Squalane or paraffin wax was used as initial liquid media. The overall CO conversion increased with increasing reaction temperature, system pressure and catalyst concentration. However, the local maximum CO conversion was exhibited at GHSV of 1500-2000 L/kg/h and superficial gas velocity of 3.4-5.0 cm/s. The CO conversion in the case of Ru/Co/Al<SUB>2</SUB><SUB>3</SUB>was much higher and stable than that in the case of Co/Al<SUB>2</SUB><SUB>3</SUB> The selectivity to C<SUB>11</SUB> wax products increased slightly with increasing GHSV; on the other hand, it decreased with increasing reaction temperature, system pressure, and solid concentration in a slurry bubble column reactor. It could be concluded that the optimum operating conditions based on the yield of hydrocarbons and wax products were; U<SUB>G</SUB>6.8-10 cm/s, Cs=15 wt.%, T=220-230 <SUP>o</SUP>, P=2.0 MPa in a slurry bubble column reactor for F-T synthesis.

Plasma-assisted catalytic methanation of CO and CO₂ over Ni-zeolite catalysts

Jwa, E.,Lee, S.B.,Lee, H.W.,Mok, Y.S. Elsevier Scientific Pub. Co 2013 Fuel processing technology Vol.108 No.-

This work investigated the hydrogenation of carbon oxides (CO and CO<SUB>2</SUB>) into methane (''methanation'') in a dielectric barrier discharge (DBD) plasma reactor packed with Ni/zeolite pellets. For the present investigation, plasma-assisted catalytic hydrogenation and conventional catalytic hydrogenation were examined for a temperature range of 180-360<SUP>o</SUP>C by varying nickel loading up to 10wt.%. In the catalysis-alone case, the conversions of CO and CO<SUB>2</SUB> were less than 15%, regardless of nickel loading, indicating that thermal activation of the catalyst was not enough to achieve significant methanation rate for the temperature range explored. On the other hand, with nonthermal plasma created in the catalyst bed, a precipitous rise in the conversion of more than 95% was observed for either CO or CO<SUB>2</SUB>. It is inferred that reactive species generated in the plasma reactor can speed up the rate-determining-step of the catalytic hydrogenation. The catalyst characterizations by using X-ray diffraction and transmission electron microscope analyses revealed that Ni particles got smaller and were more uniformly dispersed over the support material after the plasma reaction, leading to increased conversion efficiencies of carbon oxides.

Burning characteristics of single particles of coal and wood mixtures for co-firing in an upward-flowing hot gas stream

Mock, C.,Lee, H.,Choi, S.,Yang, W.,Manovic, V. Elsevier Scientific Pub. Co 2017 Fuel processing technology Vol.163 No.-

This study presents the comparative burning behaviours of single solid particles of coal and biomass mixtures for co-firing. In this experimental investigation, a direct observation approach was used to investigate the ignition, flame characteristics and combustion times by means of high-speed photography at 7000 frames per second. Single particles were entrained into a hot gas stream at 1340K and a rapid heating rate of 10<SUP>4</SUP>-10<SUP>5</SUP>K/s. The apparent volatile flames from the prepared particle size groups were observed within 20-50ms. To assess the effect of oxygen concentration, particles were burned for their flame characteristics in a range of 10%-40% O<SUB>2</SUB>. The test particles were sieved into three size groups (215-255μm, 255-300μm and 300-350μm) to assess the effect of particle size. Special particles for the co-firing effect were collected individually from two types of mixed pellet: 20:80 and 50:50 coal/wood. Pure sub-bituminous coal and wood particles were also prepared in order to compare their combustion behaviours. In the experimental setup with a cross-injection configuration, sequential combustion processes were effectively and clearly described in terms of particle displacement with time. The experimental results showed distinguishable flame characteristics from single particles of coal, 50:50 coal/wood, 20:80 coal/wood and wood, including soot flame size and intensity. The impact of high coal-blending ratio caused an increase in the flame size and intensity and the ignition time was close to that of pure coal particles. Quantitative measurements of combustion events on co-firing particles were also discussed in relation to significant impacts of the particle size and the oxygen concentration.

Side-chain engineering of ladder-structured polysilsesquioxane membranes for gas separations

Park, S.,Lee, A.S.,Do, Y.S.,Kim, J.F.,Hwang, S.S.,Lee, Y.M.,Lee, J.H.,Lee, J.S. Elsevier Scientific Pub. Co 2016 Journal of membrane science Vol.516 No.-

A comprehensive and fundamental gas transport study of ladder-structured polysilsesquioxanes (LPSQs) was systematically performed by investigating the effects of various alkyl substituents, different copolymer ratios, and UV-irradiation induced photo-crosslinking on gas separations. Overall, LPSQ membranes are more suitable for CO<SUB>2</SUB>/N<SUB>2</SUB> and CO<SUB>2</SUB>/H<SUB>2</SUB> separations due to a relatively high affinity towards CO<SUB>2</SUB> as well as rubbery polymer properties. The gas transport in LPSQ membranes was well interpreted by two important parameters, the inter-chain distance and the side chain mobility. A combination of larger inter-chain distance and higher side chain rigidity tends to increase the fractional free volume, resulting in higher gas permeability. Also, it was successfully demonstrated that the separation performance of LPSQ membranes can be predicted by using a logarithmic permeability relationship based on the transport characterization for a series of ladder-structured poly(phenyl-co-methacryloxypropyl)silsesquioxanes. Lastly, the UV-curing process reduced the permeability of LPSQ membranes, increasing the selectivity due to the restricted chain mobility.