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손재익,선도원,배달희,한근희,Cen,Kefa 한국화학공학회 1999 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.37 No.6
상온 riser와 loop seal로 구성된 순환유동층에서의 수력학적 실험을 통해 입자순환장치(loop seal)의 운전특성과 입자의 흐름 특성을 연구하였다. 0.2 m×0.15 m×0.2 m규격의 상온 loop seal 실험장치를 구성하고 석탄회의 재순환 실험을 수행하였다. 실험을 통해 유동화 공기주입량 및 주입점에 따른 입자흐름 경향을 연구하고, 고체순환속도의 제한조건 및 시스템 압력과의 수학적 관계를 연구하였다. 입자유량은 loop seal 내부 재주입구의 유동화 공기유량의 증가에 따라 증가하였다. 입자유량의 증가에 따라 down comer 고정구간의 차압이 감소하였다. The characteristics of loop seal operation and particle flow were investigated by hydrodynamics study in a cold mode riser and loop seal system. The physical dimension of 0.2 m×0.15 m×0.2 m cold mode loop seal and riser is serially connected to compose a experimental system. A coal ash was used for the experiment. The flow pattern of particle was investigated by variation of quantity of fluidizing air and location of aeration. The mathematical relationship of the limitation of particle flow rate and system pressure was analyzed. The particle flow rate increased by the increase of air flow of return leg. The pressure difference of down comer section was reduced as the increase of the particle flow rate.
Jun Cheng,Zongbo Yang,Junhu Zhou,Kefa Cen 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.2
Residence time of flue gas bubbles with different solution velocities and the influence of NOX and SO2 from flue gas on pH values of culture solutions were analyzed based on large-scale raceway reactors. Microalgal growth and CO2 fixation rates were also investigated with different gas flow rates. Bubble residence time was ~1.1 s when the solution velocity was 20 cm/s. The NOX and SO2 effects on microalgal growth were negligible, although 66% NOX and 95% SO2 were captured by the microalgal solution. Microalgal biomass productivity increased from 10.3 to 14.1 g/m2/d when flue gas flow rate increased from 20 to 50m3/h. CO2 fixation and microalgae biomass productivity increased further from 26.3 to 31.9 g/m2/d and from 14.1 to 17.1 g/m2/d, respectively, upon increase of flue gas flow rate from 50 to 150m3/h.
Direct numerical simulation of a near-field particle-laden plane turbulent jet.
Fan, Jianren,Luo, Kun,Ha, Man Yeong,Cen, Kefa Published by the American Physical Society through 2004 Physical review. E, Statistical, nonlinear, and so Vol.70 No.2
<P>The present study investigates the gas-particle two-phase flow in the turbulent plane jet by solving the two-dimensional and compressible flow fields numerically using direct-numerical-simulation technique. The flow fields are spatially developing, but we focus our study on the evolution of coherent vortex structures and dispersion patterns of particles in the near field at different Stokes numbers. The initial symmetric mode of flow changes its shape to the asymmetric mode after about three convection periods as the flow moves downstream. The concessive paring processes between two and three vortex structures are observed. The predicted mean velocity profiles show self-similar behavior and coincide well with previous experimental data. The profiles of turbulent intensity and Reynolds shear stress also display self-similar characteristics in the further downstream regions. The local-focusing phenomena of particles occur in the quasicoherent dispersion structure of particles. The higher density distribution at the outer boundary of large-scale vortex structure characterizes the dispersion pattern of particles at the Stokes numbers of order of unity. Furthermore, these particles disperse largely along the lateral direction and show the nonuniform distribution of concentration. For the particles at the Stokes number of 0.01, the dispersion along the lateral direction is considerable due to the small aerodynamics response time, but the particles are distributed evenly in the flow field. Particles at the Stokes numbers of 10 and 50 disperse much less along the lateral direction with the even density distribution. These results support the previous conclusions on the dispersion of particles in the free shear flows.</P>
Pyrolysis of wood species based on the compositional analysis
Qian Liu,Kaige Wang,Zhongyang Luo,Kefa Cen,Shurong Wang 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.2
Based on the Van Soest method, the components in Chinese fir and fast-growing poplar were quantified, and the fiber present was separated into three fractions: neutral detergent fiber, acid detergent fiber and strong acid detergent fiber. Microstructure of the fibers was investigated by a Fourier transform infrared spectrometry. Cellulose and hemicellulose both represent the characteristics of polysaccharides, while lignin has dissimilar structure. Pyrolysis of fir, poplar and the detergent fibers was carried out on a thermogravimetric analyzer coupled with FTIR spectrometry. After the removal of extractives and soluble minerals, pyrolysis of NDF shows the haracteristics of the three main components. Hydrocarbons, aldehydes, ketones, acids, alcohols and others are generated due to the primary pyrolysis of hemicellulose and cellulose in single stages. Phenols and alcohols are the dominant volatiles released from pyrolysis of lignin in two successive stages, respectively.
Yumeng Yang,Jianzhong Liu,Xiang He,Zhihua Wang,Junhu Zhou,Kefa Cen 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.4
Same amounts of moisture were removed from Ximeng lignite (XL) with different particle size ranges pretreated at different drying temperatures. The effect of conventional drying on the grindability of the XLs was investigated. Increasing the drying temperature improved the grindability of all the samples. The results of scanning electron microscopy and mercury intrusion porosimetry revealed that the dominant mechanism enhancing the grindability of XL with high moisture was the pore structure destruction induced by the steam jet flow generated with the removal of moisture. Especially, the development of large fractures had a strong connection with the change in the grindability. According to the pore size distribution, the internal structure of the 2.5-4.0mm coal samples did not develop well under high drying temperature because of the exceedingly short heating time. Therefore, coal particle size, drying temperature, and heating time must be coordinated well to achieve the enhanced drying effect. The grindability of XL had a negative linear correlation with the pore volume fractal dimension, revealing the possibility of fractal dimension for the analysis of lignite grindability.
Experimental study of acetone removal by packed-bed dielectric barrier discharge reactor
Chenghang Zheng,Xinbo Zhu,Xiang Gao,Lu Liu,Qianyun Chang,Zhongyang Luo,Kefa Cen 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5
In this study, a packed-bed dielectric barrier discharge (DBD) reactor was developed for acetone removal. The effects of packing materials were investigated in terms of discharge characteristics, removal efficiency and byproducts formation. The identification of organic byproducts was conducted. The results indicated the presence of packing materials enhanced the energy density and exhibited a positive effect on acetone removal, while high oxygen concentration inhibited the removal of acetone. The formations of byproducts were significantly reduced in the presence of packing materials. The degradation pathways and mechanisms were discussed, showing CH3 radicals played a crucial role in the acetone degradation process. Published by Elsevier B.V.