Performance analysis of K-based KEP-CO2P1 solid sorbents in a bench-scale continuous dry-sorbent CO2 capture process

Korea Institute of Energy Research (KIER) and Korea Electric Power Corporation Research Institute (KEPCORI) have been developing a CO₂ capture technology using dry sorbents. In this study, KEP-CO2P1, a potassium-based dry sorbent manufactured by a spray-drying method, was used. We employed a bench-scale dry-sorbent CO₂ capture fluidized-bed process capable of capturing 0.5 ton CO₂/day at most. We investigated the sorbent performance in continuous operation mode with solid circulation between a fast fluidized-bed-type carbonator and a bubbling fluidized-bed-type regenerator. We used a slip stream of a real flue gas from 2MWe coal-fired circulating fluidized-bed (CFB) power facilities installed at KIER. Throughout more than 50 hours of continuous operation, the temperature of the carbonator was maintained around 70-80 °C using a jacket-type heat exchanger, while that of the regenerator was kept above 180 °C using an electric furnace. The differential pressure of both the carbonator and regenerator was maintained at a stable level. The maximum CO₂ removal was greater than 90%, and the average CO₂ removal was about 83% during 50 hours of continuous operation.     

Development of sorbent manufacturing technology by Agitation Fluidized Bed Granulator (AFBG)

Thousands of ppmv of hydrogen sulfide included in coal gas should be reduced to less than a hundred ppmv in the case of IGCC to prevent a gas turbine from being corroded, and few ppmv to prevent the performance of electrodes from declining in the case of MCFC. In the present paper a laboratory scale AEBG (Agitation Fluidized Bed Granulator) is made and improved. The sorbent for the removal of hydrogen sulfide is produced using an agitation fluidized bed granulator (ZnO 1.5 mole+TiO₂ l.0mole+bentonite 5.0 wt%). The techniques for fluidizing fine particles, classified in Geldart C group, in a fluidized bed are developed by installing an agitator blade in a fluidized bed granulator. The fine particles are fluidized and granulated successfully by using the techniques. Statistical, spectral and chaos analyses with granulated sorbent (100-300 Μm) are performed to investigate the hydrodynamics of granulates in a fluidized bed. The average absolute deviation, power spectral density functions, phase space trajectories, and Kolmogorov entropy obtained from pressure fluctuation are plotted as a function of fluidizing velocity. It is shown that the Kolmogorov entropy implying the rate of generation of information can be applied to the control of fluidization regimes.     

Heavy-atomic construction of photosensitizer nanoparticles for enhanced photodynamic therapy of cancer

A new type of heavy-atom-affected Pluronic (F-127) nanoparticle (FIC NP) for photodynamic therapy (PDT) is reported. FIC NPs are formulated with biocompatible constituents, and contain densely integrated iodinated aromatic molecules that form a structurally rigid core matrix and stably encapsulate photosensitizers in a monomeric form. Tiny nanoparticles (≈10 nm) are prepared by aqueous dispersion of photosensitizer-embedded aromatic nanodomains, which self-assemble by phase separation from the Pluronic melt mixture. By using spectroscopic studies and cellular experiments, the following is demonstrated: 1) enhanced singlet-oxygen generation by means of the intraparticle heavy-atom effect on the embedded photosensitizer, 2) facilitated cell uptake due to the small nanoscopic size as well as the Pluronic surface characteristics, and thereby 3) actual enhancement of PDT efficacy for a human breast-cancer cell line (MDA-MB-231), which validates a photophysically motivated nanoformulation approach toward an advanced photosensitizing nanomedicine.     

A model on an entrained bed-bubbling bed process for CO2 capture from flue gas

A simplified model has been developed to investigate effects of important operating parameters on performance of an entrained-bed absorber and bubbling-bed regenerator system collecting CO₂ from flue gas. The particle population balance was considered together with chemical reaction to determine the extent of conversion in both absorber and regenerator. The calculated CO₂ capture efficiency agreed with the measured value reasonably well. Effects of absorber parameters — temperature, gas velocity, static bed height, moisture content of feed gas on CO₂ capture efficiency — have been investigated in a laboratory scale process. The CO₂ capture efficiency decreased as temperature or gas velocity increased. However, it increased with static bed height or moisture concentration. The CO₂ capture efficiency was exponentially proportional to each parameter. Based on the absolute value of exponent of the parameter, the effect of gas velocity, static bed height, and moisture content was one-half, one-third, and one-fourth as strong as that of temperature, respectively.     

Effect of CuO on the Sintering Behavior and Dielectric Characteristics of Titanium Dioxide

The sintering behavior and dielectric characteristics of a titanium dioxide (TiO₂) were investigated by adding CuO. The addition of CuO lowered the sintering temperature of the TiO₂. At a given temperature, the densification and grain growth rate for a TiO₂ with CuO were enhanced, compared with those of pure TiO₂. The results suggest that CuO acts as an activator for the sintering of TiO₂. Dielectric constant and loss were also examined for both pure and CuO added TiO₂ samples. The variations of dielectric constant and loss were discussed in terms of grain size, porosity, and oxygen deficiency.     

Axial voidage profile in a cold model circulating fluidized bed

The axial voidage profile was measured in a cold model circulating fluidized bed (0.38 m in diameter and 9.1 m in height) of sand particles as bed materials. Voidage in the riser column increases along the height above the distributor plate with increasing the gas velocity. However, it decreases with an increase in solid circulation rate in the bed. Model correlations to predict the solid circulation rale and the axial voidage profile in the bed are proposed.     

Antioxidative activities of mao feng tea (Camellia spp.) and kamtae (Ecklonia cava) extracts and their effects on structured lipid from corn and perilla oil

In the study, solvent extracts of kamtae (Ecklonia cava) and mao feng tea (Camillia sinensis) were used for obtaining different fractions of organic solvents (diethyl ether, butanol, and ethyl acetate) and the extracted fractions were studied for their antioxidative activities. The total phenolic contents of the mao feng tea ranged from 1.44 to 5.97 mM GAE/g while kamtae ranged from 1.13 to 4.41 mM GAE/g, respectively. Among them, ethyl acetate fraction showed the highest content of phenolic compounds, resulting in Trolox equivalent antioxidant capacity (TEAC) values as 1,554.54 (from mao feng tea) and 1,097.63 mM Trolox E/g (from kamtae). Also, ethyl acetate fractions from mao feng tea showed the highest DPPH (89.27 RSC%), superoxide anion scavenging activity (46.58%), and ferric reducing antioxidant power (FRAP) (242.2 mg GAE/g) while ethyl acetate fractions from kamtae (K-EA) showed the highest DPPH (82.23 RSC%), superoxide anion scavenging activity (28.82%), and FRAP (162.43 mg GAE/g) among the obtained fractions.     

The effect of CO<Subscript>2</Subscript> or steam partial pressure in the regeneration of solid sorbents on the CO<Subscript>2</Subscript> capture efficiency in the two-interconnected bubbling fluidized-beds system

The effect of CO₂ or steam partial pressure in the regeneration of CO₂ solid sorbents was studied in the two-interconnected bubbling fluidized-beds system. Potassium-based dry solid sorbents, which consisted of 35 wt% K₂CO₃ for CO₂ sorption and 65 wt% supporters for mechanical strength, were used. To investigate the CO₂ capture efficiency of the regenerated sorbent after the saturated sorbent was regenerated according to the CO₂ or steam partial pressure in the regeneration, the mole percentage of CO₂ in the regeneration gas was varied from 0 to 50 vol% with N₂ balance and that of steam was varied from 0 to 100 vol% with N₂ balance, respectively. The CO₂ capture efficiency for each experimental condition was investigated for one hour steady-state operation with continuous solid circulation between a carbonator and a regenerator. The CO₂ capture efficiency decreased as the partial pressure of CO₂ in the fluidization gas of the regenerator increased, while it increased as that of steam increased. When 100 vol% of steam was used as the fluidization gas of the regenerator, the CO₂ capture efficiency reached up to 97% and the recovered CO₂ concentration in the regenerator was around 95 vol%. Those results were verified during 10-hour continuous experiment.     

SOI single-electron transistor with low RC delay for logic cells and SET/FET hybrid ICs

We report on a successful fabrication of silicon-based single-electron transistors (SETs) with low RC time constant and their applications to complementary logic cells and SET/field-effect transistor (FET) hybrid integrated circuit. The SETs were fabricated on a silicon-on-insulator (SOI) structure by a pattern-dependent oxidation (PADOX) technique, combined with e-beam lithography. Drain conductances measured at 4.2 K approach large values of the order of microsiemens, exhibiting Coulomb oscillations with peak-to-valley current ratios /spl Gt/1000. Data analysis with a probable mechanism of PADOX yields their intrinsic speeds of /spl sim/ 2 THz, which is within an order of magnitude of the theoretical quantum limit. Incorporating these SETs as basic elements, in-plane side gate-controlled complementary logic cells and SET/FET hybrid integrated circuits were fabricated on an SOI chip. Such an in-plane structure is very efficient in the Si fabrication process, and the side gates adjacent to the electron island could easily control the phase of Coulomb oscillations. The input-output voltage transfer, characteristic of the logic cell, shows an inverting behavior where the output voltage gain is estimated to be about 1.2 at 4.2 K. The SET/FET hybrid integrated circuit consisting of one SET and three FETs yields a high-voltage gain and power amplification with a wide-range output window for driving the next circuit. The small SET input gate voltage of 30 mV is finally converted to 400 mV, corresponding to an amplification ratio of 13.