• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.481-486
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• 2021

In a hypersonic vehicle to solve the heat problem generated during flight, a cooling technology is being developed which uses the endothermic effect that appears during the decomposition reaction of the mounted fuel. In this study, the decomposition reaction of n-dodecane fuel was performed using HZSM-5 as a catalyst, and the catalyst was coated on metal foam to maximize the endothermic effect of the catalytic decomposition reaction and suppress coke formation. The reactor was a stainless steel flow reactor with a outer diameter of 1.27 cm, and the reaction temperature was 550 ℃, the reaction pressure was 4 MPa, and the flow rate was 12 ml per minute. As a result of the catalytic decomposition reaction using a catalyst coated with HZSM-5 on the metal foam, the heat sink was 2887 kJ/kg as a maximum, the gas phase conversion rate was 34%, and the amount of coke produced on the metal foam decreased by about 56% as the catalyst was coated compared to the uncoated catalyst.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.77-84
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• 2021

To control hot spot in a plug flow reactor (PFR) is important for the yield and purity of products and safety. In this paper, coolant temperature is set as a state variable, and radial distributions of heat and mass are considered to model the PFR more realistic than without considering radial distributions. The model consists of three state variables, reactant concentration, reactant temperature, and the coolant temperature. The flow rate of the isothermal coolant is a manipulated variable. This paper shows that the controller considering the radial distributions of heat and mass is more effective than the controller without them. Assuming that u3,0 is 0.7, the suggested control equation was robust when St is bigger than 1.3, and Ac/A is smaller than 2.0. Under this condition, the hot spot temperature changed within the relative error of one percent when the temperature of input altered within the range of five percent.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.225-232
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• 2012

A chemical reactor network (CRN) was developed for a lean premixed gas turbine combustor to predict the emission of pollutants such as NOx and CO. In this study, the predictions of NOx and CO emissions from lean premixed methane-air combustion in the gas turbine were carried out using CHEMKIN and a GRI 3.0 methane-air combustion mechanism, which includes the four NO formation mechanisms for various load conditions. The calculated results were compared with experimental data obtained from a modified test combustor to validate the model. The contributions of the four NO pathways were investigated for various load conditions. The effects of nonuniformity of the mass flux and of the equivalence ratio of the injector on the NOx formation were investigated, and a method of reducing the pollutant formation was suggested for the development of a sub-10 ppm gas turbine combustor.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.100-105
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• 2006

The photocatalytic activity of phenol degradation was investigated with the variation of operating parameters in $UV/TiO_2$ honeycomb reactor. In the comparison of phenol degradation rates among various $TiO_2$, Ishihara (STS-02)-coated honeycomb exhibited a slightly higher photocatalytic activity than Degussa P25-coated honeycomb. On the other hand, honeycomb coated by alcohol-mixed $TiO_2$ (N Co.) did not exhibit any photocatalytic activity on phenol degradation. With the increase of Degussa P25 coating amounts, the honeycomb reactor exhibited the gradual increase of phenol degradation rates. The degradation rate of phenol over $UV/TiO_2$ (Degussa P25) honeycomb reactor was asymptotically increased up to 500 mL/min, subsequently followed by a slight decrease as the recirculation rate (100~700 mL/min) was increased. UV absorption at 269 nm was high due to partial degradation of phenol at initial reaction time because the honeycomb surface was pre-adsorbed by phenol prior to UV irradiation.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.905-912
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• 2011

In this study, the novel concept catalytic reactor was designed for water-gas shift reaction (WGS) under high pressure. The novel concept catalytic reactor was composed of an autoclave, the catalyst, and liquid water. Cu-ZnO/$Al_2O_3$ as the low temperature shift catalyst was used for WGS reaction. WGS in the novel concept catalytic reactor was carried out at the ranges of 150~$250^{\circ}C$ and 30~50 atm. The liquid water was filled at the bottom of the autoclave catalytic reactor and the catalyst of pellet type was located at the gas-liquid water interface. It was concluded that WGS reaction occurred over the surface of catalysts partially wetted with liquid water. The conversion of CO for WGS was also controlled with changing content of Cu and ZnO used as the catalytic active components. Meanwhile, the catalyst of honey comb type coated with Cu-ZnO/$Al_2O_3$ was used in order to increase the contact area between wet-surface of catalyst and the reactants of gas phase. It was confirmed from these experiments that $H_2$/CO ratio of the simulated coal gas increased from 0.5 to 0.8 by WGS at gas-liquid water interface over the wet surface of honey comb type catalyst at $250^{\circ}C$ and 50 atm.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.446-455
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• 2023

A mathematical model for predicting the liquid circulation velocity in an airlift reactor was developed based on the mechanical energy balance of the fluid circulation loop. The model considered the energy loss due to a 90° turn, the energy loss due to friction, and the energy loss due to the change in cross-sectional area at each part of the reactor. The model that separately considered the loss coefficients related to friction, direction change, and cross-sectional area change was able to predict the liquid circulation velocity better than the previous model using lumped parameters. The liquid circulation velocity was measured by the tracer pulse method. Most of our experimental results obtained in external-loop airlift reactors, which had the top and bottom connecting pipes, as well as other investigators' results obtained in various types of airlift reactors, were well predicted by the developed model with an error within 20%. Useful empirical equations for the loss coefficient related to the 90° turn of the circulating fluid were obtained in external and internal-loop airlift reactors and used to predict the liquid circulation velocity.

• Clean Technology
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• v.17 no.1
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• pp.69-77
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• 2011

The intrinsic $CO_2$ separation and hydrogen production system is a novel concept using oxidation and reduction reactions of oxygen carrier for both $CO_2$ capture and high purity hydrogen production. The process consists of a fuel reactor (FR), a steam reactor (SR) and an air reactor (AR). The natural gas ($CH_4$) is oxidized to $CO_2$ and steam by the oxygen carrier in FR, whereas the steam is reduced to hydrogen by oxidation of the reduced oxygen carrier in SR. The oxygen carrier is fully oxidized by air in AR. In the present study, the chemical looping moving bed reactor having 200 L/h hydrogen production capacity is designed and the hydrodynamic properties were determined. Compared with other reactors, two moving bed reactors (FR, SR) were used to obtain high conversion and selectivity of the oxygen carrier. The desirable solid circulation rates are calculated to be in the range of $20{\sim}100kg/m^2s$ from the conceptual design. The solid circulation rate can be controlled by aeration in a loop-seal. To maintain the gas velocity in the moving beds (FR, SR) at the minimum fluidization velocity is found to be suitable for the stable operation. The solid holdup in moving beds decrease with increasing gas velocity and solid circulation rate.

• Journal of the Korean Applied Science and Technology
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• v.23 no.3
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• pp.199-206
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• 2006

Direct decomposition of methane over three types of carbon black (N330-p, N330-f, and HI-900L) was carried out in a fluidized bed quartz reactor. Properties of carbon black before and after reaction were measured and found to be related with surface structure and weight gain. For N330-p and N330-f, some carbon deposit on the surface was considered to be the reason for the increase of BET surface area and pore volume with weight gain. Carbon deposits on the surface and the conglutination of some aggregates may explain the slight increase of particle size. Properties of HI-900L changed much more significantly with weight gain. It is supposed that the increase of aggregate size of HI-900L were due to some unknown oily components. The corresponding agglomeration might be the reason for the decrease of BET surface area with weight gain, as compared with the increase of that for the case of N330 black.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.115-117
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• 2003

No Abstract, See Full Text

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5304-5309
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• 2013

The degradation of methylethylkeone(MEK) was investigated by the continuous single module photocatalytic reactor. Operational conditions were initial concentration of MEK, intensity of photon flux, and activity change according to the long time operation. The photocatalytic degradation was decreased with the increase of MEK concentration, and the degree of decrease was larger at higher flow rate. Removal efficiency of photocatalytic reactor was decreased with the increase of reactor diameter and lamp wavelength under the same residence time condition. Continuous single module photocatalytic reactor was successfully operated without any activity drop during 120hrs operation.