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>

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.

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.

Evaluation of the CO₂ sequestration capacity for coal fly ash using a flow-through column reactor under ambient conditions

Jo, H.Y.,Ahn, J.H.,Jo, H. Elsevier Scientific Pub. Co 2012 Journal of hazardous materials Vol.241 No.-

An in-situ CO<SUB>2</SUB> sequestration method using coal ash ponds located in coastal regions is proposed. The CO<SUB>2</SUB> sequestration capacity of coal fly ash (CFA) by mineral carbonation was evaluated in a flow-through column reactor under various conditions (solid dosage: 100-330g/L, CO<SUB>2</SUB> flow rate: 20-80mL/min, solvent type: deionized (DI) water, 1M NH<SUB>4</SUB>Cl solution, and seawater). The CO<SUB>2</SUB> sequestration tests were conducted on CFA slurries using flow-through column reactors to simulate more realistic flow-through conditions. The CO<SUB>2</SUB> sequestration capacity increased when the solid dosage was increased, whereas it was affected insignificantly by the CO<SUB>2</SUB> flow rate. A 1M NH<SUB>4</SUB>Cl solution was the most effective solvent, but it was not significantly different from DI water or seawater. The CO<SUB>2</SUB> sequestration capacity of CFA under the flow-through conditions was approximately 0.019g CO<SUB>2</SUB>/g CFA under the test conditions (solid dosage: 333g/L, CO<SUB>2</SUB> flow rate: 40mL/min, and solvent: seawater).

Amines immobilized double-walled silica nanotubes for CO₂ capture

Ko, Y.G.,Lee, H.J.,Oh, H.C.,Choi, U.S. Elsevier Scientific Pub. Co 2013 Journal of hazardous materials Vol.250 No.-

Novel silica support has been required for high amine loading and good CO<SUB>2</SUB> molecule diffusion into its pores to increase the performance of CO<SUB>2</SUB> adsorbents. Herein, amine groups supported on double-walled silica nanotubes (DWSNTs) have been prepared via the immobilization of various aminosilanes (primary, secondary, tertiary, di-, and tri-aminosilanes) on DWSNT, and found to be a very effective adsorbent for CO<SUB>2</SUB> capture. Amine groups immobilized DWSNTs captured CO<SUB>2</SUB> reversibly in a temperature swing process at various adsorption temperatures (25<SUP>o</SUP>C, 50<SUP>o</SUP>C, 75<SUP>o</SUP>C, and 100<SUP>o</SUP>C). The amines on modified DWSNTs showed high CO<SUB>2</SUB> capture capacity in the order of tri-, di-, primary, secondary, and tertiary amines. The CO<SUB>2</SUB> capture capacity of all aminosilanes immobilized DWSNTs decreased linearly with the increase of the adsorption temperature. We expect that DWSNT would be able to inspire researchers to use it not only as a support for CO<SUB>2</SUB> capture but also as a promising candidate for various applications.

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.

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.

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.

Total utilization of waste tire rubber through pyrolysis to obtain oils and CO₂ activation of pyrolysis char

Choi, G.G.,Jung, S.H.,Oh, S.J.,Kim, J.S. Elsevier Scientific Pub. Co 2014 Fuel processing technology Vol.123 No.-

Waste tire rubber (WTR) was pyrolyzed in a fixed bed reactor in the final temperature range of 500-800<SUP>o</SUP>C. Pyrolysis oils were analyzed both quantitatively and qualitatively. Pyrolysis chars obtained were activated using CO<SUB>2</SUB> at a final temperature of 950<SUP>o</SUP>C with a final activation time of 1-3h. In addition, the influence of the acid treatment of pyrolysis char on the physicochemical properties was investigated. In the experiments, the yields of pyrolysis oil and pyrolysis char were 30-38 and about 37wt.%, respectively. The pyrolysis oils consisted mainly of limonene, aromatic hydrocarbons such as xylene, and some heteroatom-containing compounds, such as benzothiazole and 2,4-dimethylquinoline. The sulfur contents of the pyrolysis oils were 0.85-0.96wt.%. Most of the sulfur remained in the pyrolysis char. The maximum surface area of the activated char obtained by CO<SUB>2</SUB> activation was 437m<SUP>2</SUP>/g. The acid treatment of the pyrolysis char decreased the ash and sulfur contents, which supported the strong potential of the acid-treated char for use in commercial applications.

Ternary mixed-gas separation for flue gas CO₂ capture using high performance thermally rearranged (TR) hollow fiber membranes

Woo, K.T.,Dong, G.,Lee, J.,Kim, J.S.,Do, Y.S.,Lee, W.H.,Lee, H.S.,Lee, Y.M. Elsevier Scientific Pub. Co 2016 Journal of membrane science Vol.510 No.-

A comprehensive study evaluated the mixed-gas (CO<SUB>2</SUB>/N<SUB>2</SUB>/O<SUB>2</SUB>) separation performance of thermally rearranged polybenzoxazole-co-imide (TR-PBOI-AD5) hollow fiber membranes fabricated in-house (pure-gas CO<SUB>2</SUB> permeance of 481GPU and ideal CO<SUB>2</SUB>/N<SUB>2</SUB> selectivity of 17.7). The criteria for the determining the two major operating conditions (pressure ratio and feed flow rate) were identified in order to deliver optimal separation performance with low process energy consumption. By varying the feed CO<SUB>2</SUB> concentrations, it was found that a single-stage operation using TR-PBOI-AD5 (produced by bis-APAF and DAM as the TR-able and non-TR-able diamines, respectively, based on 6FDA) hollow fiber membranes was not sufficient to meet the required 90% permeate CO<SUB>2</SUB> purity target, while a two-stage operation using the same membranes led to a permeate CO<SUB>2</SUB> purity (81%) closer to the target value. The comparison study among the TR polymer membranes and three other polymer membranes highlighted the significance of an appropriate choice of a mixed-gas separation operating scheme to fully utilize the exceptional permeation properties of the recently developed high performance membranes such as TR polymeric membranes.