Effect of water pretreatment on CO<Subscript>2</Subscript> capture using a potassium-based solid sorbent in a bubbling fluidized bed reactor

A bubbling fluidized bed reactor was used to study CO₂ capture from flue gas by using a potassium-based solid sorbent, sorbKX35 which was manufactured by the Korea Electric Power Research Institute. A dry sorbent, sorbKX35, consists of K₂CO₃ for absorption and supporters for mechanical strength. To increase initial CO₂ removal, some amount of H₂O was absorbed in the sorbent before injecting simulated flue gas. It was possible to achieve 100% CO₂ removal for more than 10 minutes at 60°C and a residence time of 2 s with H₂O pretreatment. When H₂O pretreatment time was long enough to convert K₂CO₃ of sorbKX35 into K₂CO₃ · 1.5H₂O, CO₂ removal was excellent. The results obtained in this study can be used as basic data for designing and operating a large scale CO₂ capture process with two fluidized bed reactors. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

A model on desulfurization characteristics of an entrained bed-bubbling bed hot gas cleanup system for IGCC

A mathematical model has been developed to predict performance of a continuous entrained-bed and bubbling fluidized-bed hot gas desulfurization system in IGCC. The model combines the particle residence time with the kinetic rate in each reactor. The model has been applied to the KIER’s laboratory scale fluidized bed process. The present model provided a reasonable fit in predicting experimental results that the outlet concentration of H₂S from the desulfurizer and SO₂ from the regenerator increased nearly proportionally to the inlet concentration of H₂S to the desulfurizer. The model also could predict well the outlet concentration of O₂ from the regenerator to decrease as the inlet concentration of H₂S to the desulfurizer increased. The present model predicted with reasonable accuracy mean diameter of bed particles and sulfur content of particles in desulfurizer and regenerator.     

Effect of bed height on the carbon dioxide capture by carbonation/regeneration cyclic operations using dry potassium-based sorbents

The effect of bed height on CO₂ capture was investigated by carbonation/regeneration cyclic operations using a bubbling fluidized bed reactor. We used a potassium-based solid sorbent, SorbKX35T5 which was manufactured by the Korea Electric Power Research Institute. The sorbent consists of 35% K₂CO₃ for absorption and 65% supporters for mechanical strength. We used a fluidized bed reactor with an inner diameter of 0.05 m and a height of 0.8 m which was made of quartz and placed inside of a furnace. The operating temperatures were fixed at 70 °C and 150 °C for carbonation and regeneration, respectively. The carbonation/regeneration cyclic operations were performed three times at four different L/D (length vs diameter) ratios such as one, two, three, and four. The amount of CO₂ captured was the most when L/D ratio was one, while the period of maintaining 100% CO₂ removal was the longest as 6 minutes when L/D ratio was three. At each cycle, CO₂ sorption capacity (g CO₂/g sorbent) was decreased as L/D ratio was increased. The results obtained in this study can be applied to design and operate a large scale CO₂ capture process composed of two fluidized bed reactors. This work was presented at the 7 ^th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

LOFT L9-3 Experiment Simulation Using the SPACE Code

The KHNP （Korea Hydro ＆ Nuclear Power Co.） has developed a multipurpose nuclear safety analysis code called SPACE （the safety and performance analysis code） for nuclear power plants. SPACE code is a best-estimated two-phase three-field thermal-hydraulic analysis code used to analyze the safety and performance of pressurized water reactors. In this paper, LOFT （loss of fluid test） L9-3 experiment using the SPACE code was selected to confirm the capability of SPACE code and the results calculated by the SPACE code are compared with those measured through the experiment. The results were compared with the experimental data and those of the other code simulations. Throughout the simulation result, it was concluded that the SPACE code can effectively simulate LOFT L9-3 experiment.     

Comparison of two different hot-gas desulfurization powder processes: Transport reactor and bubbling fluidized bed

The KIER bench-scale fluidized hot-gas desulfurization process was designed to operate two different configurations. One was a bubbling desulfurizer and a bubbling regenerator, the other was a transport desulfurizer and a bubbling regenerator. Two systems were compared each other in terms of operational parameters, hydrodynamic parameters such as gas flow rate and solid circulation rate, reaction characteristics such as sorbent sulfur sorption capacity and regeneration characteristics. Also, the fresh and used solid samples from two different modes were analyzed for density, sulfur content, size, attrition, and morphology. The transport–bubbling system was simpler and more stable in pressure balance, but a little more unstable in temperature control than the bubbling–bubbling system. The solid residence time in each reactor was 0.68 h for the bubbling–bubbling system, and 0.09 h for the transport–bubbling system.     

Type transition in onset condition of turbulent fluidization

The type transition in onset condition of turbulent fluidization in gas fluidized beds was investigated to obtain the relation representing more precise roles of physical properties of gas and solid particles. The type transition in onset condition of turbulent fluidization occurs at Archimedes number of 20.87 by type transition of bubble breakup. The maximum stable bubble diameter (d _bmax ) is greater than the equilibrium bubble diameter (d _beq ) in the region, Ar< 20.87, but d_beq>d _bmax in the region, Ar>20.87. Therefore, the onset of turbulent fluidization is determined in the region, Ar<20.87, by d _beq and in the region, Ar>20.87, by d _bmax as the limit of bubble growth. The uc decreases in the region, Ar<20.87, but increases in the region, Ar>20.87 as temperature increases.     

Physiochemical and oxidative stability of interesterified structured lipid for soft margarine fat containing Δ5-UPIFAs

Structured lipid (SL) was synthesized from pine nut oil (PNO) and palm stearin (PS). In SL, 8.81% of Δ5-unsaturated polymethylene interrupted fatty acids (Δ5-UPIFAs) were intentionally incorporated into the sn-2 position through acyl migration. The obtained SL contained mostly the β′ form and a wide plastic range with solid fat index of 26.5% at 10 °C to 2.29% at 35 °C, indicating that the obtained SL (containing zero-trans fatty acid) may be desirable for soft (tub) margarine fat. Subsequently, the antioxidative effects of α-tocopherol (α-TOH), ascorbyl palmitate (AP), quercetin (Qu), and combinations thereof on SL were investigated. Results showed that Qu (500 μg/g) showed the most effective antioxidant activity, followed by AP (500 μg/g); while α-TOH with any concentrations (100, 200 and 500 μg/g) did not show significant protective activity in the obtained SL. Each mixture of AP + Qu and α-TOH + AP + Qu also showed effective antioxidant activity in the obtained SL.     

Microstructure and Mechanical Properties of Hybrid Laser-Friction Stir Welding between AA6061-T6 Al Alloy and AZ31 Mg Alloy

For the purpose of improving the strength of this dissimilar joint,the present study was carried out to investigate the improvement in intermetallic layer by using a third material foil between the faying edges of the friction stir welded and hybrid welded Al6061-T6/AZ31 alloy plates.The difference in microstructural and mechanical characteristics of friction stir welded and hybrid welded Al6061-T6/AZ31 joint was compared.Hybrid buttwelding of aluminum alloy plate to a magnesium alloy plate was successfully achieved with Ni foil as filler material,while defect-free laser-friction stir welding(FSW) hybrid welding was achieved by using a laser power of 2 kW.Transverse tensile strength of the joint reached about 66% of the Mg base metal tensile strength in the case of hybrid welding with Ni foil and showed higher value than that of the friction stir welded joint with and without the third material foil.This may be due to the presence of less brittle Ni-based intermetallic phases instead of Al12Mg17.     

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.