Joo-Hong Choi

The reactivity of V2O5-WO3-TiO2 catalyst supported on a ceramic filter candle for selective reduction of NO

For realizing the environmental issues and constituting an economical treatment system, a catalytic filter based on V2O5/TiO2 supported on tubular filter elements has many advantages by removing NOx and particulate simultaneously from flue gas. In order to improve the activity of a catalytic filter based on V2O5/TiO2 supported on a commercial high temperature filter element (PRD-66), the promoting effects of WO3 were investigated in an experimental unit. PRD-66 presented very good properties for SCR catalyst carrier since it contains much active material such as A12O3 SiO{om2}, and MgO whose contributions were remarkable. For additional catalyst carrier, TiO2 particles were coated in the pores of PRD-66 with relatively good distribution of the particle size less than 1 μm, by a coating process applying centrifugal force. WO3, in the V2O5-WO3-TiO2/PRD-66 catalytic filter system, increased the SCR activity significantly and broadened the optimum temperature window. The catalytic filter shows the maximum NO conversion of more than 95% for NO concentration of 700 ppmv at face velocity of 0.02 m/sec, which is comparable to the current commercial catalytic filters of plate form.

Experimental study on the nozzle effect of the pulse cleaning for the ceramic filter candle

The effects of the nozzle size and its shape for the pulse cleaning of a ceramic filter candle were observed experimentally in the hot and cold bench units using commercial filter elements. The traces of the transient pressure, temperature, and overpressure in the filter cavity were measured to estimate the pulse cleaning effects. At the given pulse cleaning system, the pulse cleaning was optimized by the reciprocal effect of the nozzle size, which increases the primary pulse gas mass and reduces the secondary pulse mass as its size increases. The convergent nozzle showed a higher pulse effect than the straight one due to its concentrating effect, which leads to high pressure of the gas leaving the pulse nozzle.

Production of bio-diesel fuels by transesterification of rice bran oil

Transesterification of rice bran oil was investigated to produce the bio-diesel oil. Experimental conditions included molar ratio of rice bran oil to alcohol (1:3, 1:5 and 1 :7), concentration of catalyst used (0.5, 1.0 and 1.5 wt%), types of catalysts (sodium methoxide, NaOH and KOH), reaction temperatures (30, 45 and 60°C) and types of alcohols (methanol, ethanol and butanol). The conversion of rice bran oil increased with the alcohol mixing ratio and with the reaction temperature. Sodium methoxide was the most effective among the catalysts. The conversion was increased with the concentration of catalyst, but slightly increased over 1.0 wt%. The best conversion was obtained using methanol with sodium methoxide. In that case, 98% conversion was achieved within 1 hr. The physical properties of rice bran oil for diesel fuel can be significantly improved by transesterification reaction.

The preparation of V2O5/TiO2 catalyst supported on the ceramic filter candle for selective reduction of NO

In order to prepare the catalytic filters based on V2O5/TiO2 for the removal of NOx and participate simultaneously from the flue gas stream, the experimental study was carried out. The effective method to support TiO2 layer in the pore of the commercial ceramic filter element was developed. TiO2 layer was supported on the filter element by three methods; impregnation with Ti solution, sol-gel dip coating and sol-gel centrifugal coating. As the model test to check the catalytic activity, NO reduction in the oxidizing stream was investigated. The catalytic filter prepared by applying the centrifugal force showed the best NO conversion more than 90% when the face velocity was 0.02 m/sec. This was a very promising result for the application of catalytic filter for the flue gas control at high temperature. The supporting methods by the impregnation and dip coating were not recommended because the TiO2 layer was concentrated in the exterior layer of the filter element.

The effect of particle shape on the pressure drop across the dust cake

In order to observe the effect of particle shape of poly-dispersed dusts on filter performance, the pressure drop across the dust cakes of fly ashes from a conventional power plant (PC), fluidized bed combustion (FBC), and paint incinerator (FI) was measured over a metal filter element in the accurate conditions. A fluidized bed column was used to prepare the dust feed stream of uniform particle distribution. The fine particles of FI ash have a tendency to be agglomerated at low transport velocity. The aggregates were broken at high velocity of more than 21 cm/sec. FBC ash composed of jagged type particles and containing high concentration of unburned-carbon showed higher pressure drop than that of PC ash composed mostly of spherical particles. FI ash composed of aggregates of very fine carbon particles presented the highest pressure drop among the fly ashes tested. The shape factors of PC, FBC, and FI ash were estimated as 0.91, 0.76, and 0.65, respectively, by the Ergun equation. The results implied that the irregular particle tends to form a higher pressure drop and to be more compressible than spherical one.

A Study on Insulation Characteristics of Laminated Polypropylene Paper for an HTS Cable

Studies on developing an HTS (High-Temperature Superconducting) power cable with high transmission capacity and less loss are actively being performed worldwide. In Korea, an HTS power cable is being developed which applies cold dielectric type that a cable core wrapped by insulating papers is impregnated in liquid nitrogen. The insulating paper used in cold dielectric type is LPP (Laminated Polypropylene Paper) which has less dielectric loss and a superior dielectric property. In this paper, AC and lightning impulse breakdown strength and V-t characteristics with mini-model cables which were manufactured as the same structure with an HTS power cable were researched. Also, a thickness of insulation layer for a 154 kV class HTS power cable was designed as a result.

Pt-V2O5-WO3/TiO2 catalysts supported on SiC filter for NO reduction at low temperature

The catalytic filter, V2O5-WO3-TiO2 supported on a ceramic filter, is known as a promising material for treating particulates and NOx simultaneously at optimum temperatures around 320°C. In order to improve its catalytic activity at low temperatures, the effect of Pt addition on the catalytic filter has been investigated. Catalytic filters, Pt-V2O5-WO3-TiO2/SiC, were prepared by co-impregnation of Pt, V, and W precursors on TiO2 coated-SiC filter by vacuum aided-dip coating. The Pt-added catalytic filter shifted the optimum working temperature from 280–330°C (for the non Pt-impregnated filter) to 180–230°C, providing Nx slip concentration less than 20 ppm for the treatment of 700 ppm NO at a face velocity of 2 cm/s with the same value over the non Pt-added catalytic filters. The promotional effect following the addition of Pt is believed to result from electrical modification of the catalyst maintaining a high electron transfer state. Ammonia oxidation was also observed to be dominant above the optimal temperature for SCR.

Experimental Investigation into Compression Properties of Integrated Coal Gasification Combined Cycle Fly Ashes on a Ceramic Filter

The compression properties of IGCC (integrated coal gasification combined cycle) fly ash cake on a ceramic filter were carefully investigated under well-controlled conditions. Overall cake porosity and pressure drop of dust cake of three different particles of geometric mean diameters of 3.7, 6.2, and 12.1 Μm, and dynamic shape factors of 1.37, 1.57 and 1.65, respectively, were investigated, at face velocities of 0.02-0.06 m/s. Overall cake porosity was strongly dependent on face velocity, mass load, and particle size. The expressions for overall cake porosity, considering the compression effect, and pressure drop across the dust cake were developed with good agreement with experimental results.

Optimization of Nozzle Design for Pulse Cleaning of Ceramic Filter

Abstract The experimental study was carried out to optimize the nozzle shape and dimension for the pulse cleaning of a ceramic filter candle. A bench scale unit of ceramic filter consisting of four commercial filter elements was used to measure the traces of the transient pressure around the nozzle and the overpressure in the filter cavity during the pulse-jet injection of pulse gas. Overpressure in the filter cavity is related to the pulse cleaning force. Nozzle design is concerned to increase the overpressure at the open end of filter element of pulse cleaning inlet, as well as to minimize the consumption of pulse gas. Convergent nozzle induces more secondary flow and generates higher pulse cleaning effect than straight nozzle. Nozzles of different convergent ratio (ratio of outlet to inlet diameter of nozzle) by changing the convergent angle and height were tested. The outlet diameter of convergent nozzle seriously influences the cleaning effect. The optimum convergent ratio increases with the increase of pulse gas pressure. The nozzle position (distance of nozzle tip from the open end of filter inlet) is also important to decide the nozzle dimension. Nozzle of large outlet diameter accepts high pressure of pulse gas to provide large overpressure in the filter cavity of top position by applying long distance.

Particle Size Effect on the Filtration Drag of Fly Ash from a Coal Power Plant

In order to investigate the filtration properties of fly ash from a conventional coal power plant, the filtration drag across the dust cake over an absolute fiberglass filter element was measured. A fluidized bed column was utilized to obtain a well characterized particle stream. The cake resistance coefficient was analyzed by the equation proposed by Endo et al. [1998] in order to observe the effect of particle size and polydispersity. The filtration drag was measured for three kinds of particle stream having the geometric mean particle size of 3.15, 6.07, and 7.83 μm and the geometric standard deviation less than 1.44 in the practical operation conditions for the field applications of face velocity of 0.03–0.06 m/s and area dust load up to 0.2 kg/m2. A dust cake of smaller particle size showed larger pressure drop even though the porosity was higher and presented high compressibility according to the face velocity. The particle polydispersity was also a dominant factor affecting the compressibility of the dust cake.