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Hydrodynamic Characteristics of a FCC Regenerator
Won, Namkung,Kim, Sung Won,Kim, Sang Done 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.1
The hydrodynamic and gas mixing characteristics have been determined in a FCC regenerator(0.48mI.D.*3.4m high) with FCC particles. Solids holdup in the dense bed decreases with increasing gas velocity, but it increases in the freeboard region. The bubble/void fraction increases with an increases with an increase along the bed height at a given gas velocity and increases with increasing gas velocity at a constant bed height. Backmixed tracer gas at the wall region is higher than at the center region of the bed. The gas backmixing coefficient decreasing gas velocity.
SOLIDS FLOW CHARACTERISTICS IN LOOP - SEAL OF A CIRCULATING FLUIDIZED BED
Kim, Sung Won,Namkung, Won,Kim, Sang Done 한국화학공학회 1999 Korean Journal of Chemical Engineering Vol.16 No.1
The hydrodynamics of solids (FCC) recycle in a loop-seal (0.08 m) at the bottom of the downcomer (0.08 m-I.D.×4.0 m-high) in a circulating fluidized bed (0.1 m-I.D.×5.3 m-high) have been determined. Solid flow rate through the loop-seal increases linearly with increasing aeration rate. At the same aeration rate, the maximum solid flow rate can be obtained at a loop-seal height-to-diameter ratio of 2.5. The effects of solid inventory, solid circulation rate and gas velocity on pressure balance around the CFB have been determined. At a given gas velocity and solid circulation rate, pressure drops across the downcomer and loop-seal increase linearly with increasing solids inventory in the bed. At a constant solid inventory, pressure drops across the riser and the downcomer increase with increasing solid circulation rate but decrease with increasing gas velocity in the riser. The obtained solid flow rate has been correlated with pressure drop across the loop-seal.
Namkung, Hueon,Park, Ju-Hyoung,Lee, Young-Joo,Song, Gyu-Seob,Choi, Jong Won,Kim, Joeng-Geun,Park, Jun-Su,Um, Byung Hwan,Song, Kwang Ho,Park, Se-Joon,Choi, Young-Chan Elsevier 2017 Fuel processing technology Vol.167 No.-
<P><B>Abstract</B></P> <P>The application of biomass resources and sewage sludge is currently the most important issue in the field of coal combustion systems. The main drawback for operating a boiler system is its varied firing characteristics and low heating value. In this study, we have developed new synthetic fuels, namely hybrid sludge fuel (HSF), using coal and sewage sludge impregnated bioliquid (molasses) and evaluated their properties by comparison with conventional fuels. To prepare the HSF, it was treated in a carbonization system at 250°C. Depending on the van Krevelen diagram, the fuel quality of HSF was superior to that of raw bioliquid and sewage sludge. In addition, its fuel characteristic was similar to sub-bituminous and bituminous coal. Thermogravimetric analysis (TGA) indicated only a single-stage combustion pattern for HSF during non-isothermal heating. To clarify the unburned carbon (UBC) content, an ultimate analysis was conducted. The amount of UBC of the HSF was much more than that of sewage sludge, but less than that of coal. To investigate the surface hydrophobicity of HSF, Fourier transform infrared spectroscopy (FT-IR) analysis and a moisture re-adsorption test were carried out. The HSF possessed high hydrophobicity and presented a low moisture re-adsorption rate compared to conventional fuels.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The new synthetic fuel (HSF) using coal and sewage sludge impregnated bioliquid was investigated. </LI> <LI> HSF properties were similar to sub-bituminous and bituminous coal on the van Krevelen diagram. </LI> <LI> HSF showed single-stage combustion characteristics from the thermogravimetric analysis. </LI> <LI> HSF presented higher fuel reactivity in comparison with low reactivity coal. </LI> <LI> HSF had a higher hydrophobicity on the surface. </LI> </UL> </P>
Namkung, Hueon,Lee, Young-Joo,Park, Ju-Hyoung,Song, Gyu-Seob,Choi, Jong Won,Choi, Young-Chan,Park, Se-Joon,Kim, Joeng-Geun Elsevier 2018 Fuel Vol.225 No.-
<P><B>Abstract</B></P> <P>The co-combustion of sewage sludge and woody biomass is a key issue in coal power plants. Different combustion and ash behaviors of sewage sludge and woody biomass cause unpredictable operating concerns. In this study, the combustion and ash agglomeration behavior of blended fuel of sewage sludge and woody biomass (BSW) were investigated while coal co-combusted with it. Thermogravimetric analysis (TGA) revealed that adding a high amount of BSW into the coal lowered volatilization, ignition, and burn-out temperature. The char combustion reactivity of coal differed from that of BSW. The shrinking core model (SCM) and volumetric reaction model (VRM) were used to fit the char combustion reactivity of coal and BSW. In the case of ash agglomeration behavior, BSW addition led to increasing particle agglomeration at fouling temperatures. In particular, phosphorus composition influenced particle growth, which was verified using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) analysis. Furthermore, the ash mixture ratio of BSW and coal changed the intensity of the phosphorus-bearing mineral phase from X-ray diffraction (XRD) analysis, and finally influenced the melting temperature of the ash.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The combustion and ash agglomeration characteristics of coal and BSW mixture were investigated. </LI> <LI> Addition of BSW into the coal lowered the combustion temperature profiles during non-isothermal heating conditions. </LI> <LI> Carbon and reagent gas reaction occurred on exterior and interior of the particle during char combustion. </LI> <LI> BSW containing high phosphorus contents made a high agglomeration tendency and low melting mineral phase. </LI> </UL> </P>
( Hye Won Seo ),( Min Jin Jeong ),( Jung Namkung ),( Chan Joo Kim ),( Ji Young Kwon ) 대한산부인과학회 2017 Obstetrics & Gynecology Science Vol.60 No.6
Peritoneal trophoblastic implant can occur after treatment of ectopic pregnancy. Similarly, after termination of intrauterine pregnancy, trophoblastic implants are rare but can be a complication of perforation during dilatation and curettage. We report an extremely rare case of trophoblastic implant on the myometrium, ovarian surface, and peritoneal wall 4 months after uncomplicated dilatation and curettage. To the best of our knowledge, this is the first case of peritoneal trophoblastic implant following dilatation and curettage without uterine perforation. Knowledge of this case is useful for the management of patients with persistent low-level elevation of serum human chorionic gonadotropin after termination of pregnancy.