Guiyoung Han

Photocatalytic oxidation of methyl orange in a three-phase fluidized bed reactor

The photocatalytic oxidation of methyl orange under weak illumination conditions was carried out in two different types of fluidized bed reactors. TiO2 powder was employed as the photocatalysts and a 15 W low pressure mercury lamp was used as the light source and the reactor volume was 2.5 l. The parametric study of photocatalytic oxidation of methyl orange in two different types of fluidized beds was investigated; effect of catalyst loadings, pH, air flow rate, initial concentration and oxygen concentration on the oxidation reaction rate. The experimental results were analyzed in conjunction with the characteristics of fluidized bed and the reactor geometry effect on the reaction rate was analyzed.

Characteristics of Slug Flow in a Fluidized Bed of Polyethylene Particles

The slug flow behavior of polyethylene particles was examined in a fluidized bed of 7 cm ID and 50 cm in height. The employed polymer particles were high density polyethylene (HDPE) with the average particle size of 603 μm. The slugging flow of polyethylene particles was analyzed from the measured pressure drop signals by classical statistical methods such as absolute average deviation, probability density function, power spectrum, auto-cor-relation, and cross-correlation. The results show that in spite of high dielectric constant of polymer particles, the slugging phenomena such as incipient slugging velocity, slugging frequency and slugging rise velocity were very similar to the Geldart B type non-polymeric particles. It was observed that slug frequencies decreased with gas velocity and the limiting slug frequency was observed for the gas velocities in this study.

The slug flow behavior of polyethylene particles polymerized by Ziegler-Natta and metallocene catalysts

We investigated the flow behavior of polyethylene particles polymerized by Ziegler-Natta catalyst and Metallocene catalyst. The employed polymer particles were linear low-density polyethylene (LLDPE), and average particle size was 600 Μm. Different flow behavior of polymer particles in a fluidized bed was observed with different polymerization catalysts in the bubbling and slugging flow regimes. The flow behavior determined from the pressure drop fluctuation in the lower and upper section of the bed was analyzed with statistical methods.

Axial Dispersion of Gas in a Circulating Fluidized Bed

An axial dispersion of gas in a circulating fluidized bed was investigated in a fluidized bed of 4.0 cm I.D. and 279 cm in height. The axial dispersion coefficient of gas was determined by the stimulus-response method of trace gas of CO2. The employed particles were 0.069 mm and 0.147 mm silica-sand. The results showed that axial dispersion coefficients were increased with gas velocity and solid circulation rates as well as suspension density. The experimentally determined axial dispersion coefficients in this study were in the range of 1.0-3.5 m2/s.

Slugging bed height of polyethylene particles in a fluidized bed with an expanded section

Slugging experiments were performed in a fluidized bed of 7 cm ID and 50 cm in height to examine the maximum bed height with an expanded section. High-density polyethylene (HDPE) particles of 0.5 mm were employed as the bed materials. The slugging bed height was linearly increased with the gas velocity in the beds of uniform cross section as well as expanded section with different slope. From the results of this study, it was found that the existing correlation to predict the slugging bed height based on the heavier particles for the uniform cross section area was satisfactorily applied for the lighter particles of HDPE and for the expanded section, a slight modification was made for the particle of HDPE in the slugging bed.

Performance comparison of dish solar collector system with mirror arrays and receiver shapes

The thermal performance comparisons of the dish solar collector system are numerically investigated with mirror arrays and receiver shapes. In order to compare the performances of the dish solar collector systems, six different mirror arrays and four different receiver shapes are considered and the radiative heat flux distribution on the inside of the receiver is analysed. The solar irradiation reflected by mirrors is traced using the Monte-Carlo method. The results show that the dome type has the best performance in receiver shapes and the 2AND4INLINE has the best performance in mirror arrays except the perfect mirror.