Yong-g Seo

The catalytic heat exchanger using catalytic fin tubes

Abstract The characteristics of a catalytic heat exchanger which integrates heat generation and heat exchange into one equipment have been investigated by the experiment and numerical simulation. The surface of the fin tubes was catalyzed by the formation of the oxide layer and the subsequent washcoating of ZrO2, followed by the impregnation of Pd catalyst. The experimental results showed that the performance of catalytic combustion in the catalytic heat exchanger was more significantly affected by the inlet velocity of the mixture than by its inlet temperature and equivalence ratio. It was also found that the catalytic surface area was a critical parameter to obtain the complete conversion of the mixture. Numerical simulation has been performed with a commercial software FLUENT. The calculated results indicated that the performance of the catalytic combustion was influenced by the catalytic fin configuration as well as the flow pattern of the mixture over the catalytic fins. The results recommend that the number and thickness of catalytic fins should be designed above 6 pieces/inch and less than 1.0 mm to achieve the best performance in the catalytic heat exchanger.

Development of a catalytic burner with Pd/NiO catalysts

Abstract A catalytic burner was studied which can be used as a heater operated at medium temperature. The catalytic combustion was initiated by an igniter which was placed on the exit surface of the catalyst layer. Noble metal catalysts (Pd/NiO) which were supported on alumina washcoated honeycomb were used, whose maximum heat-resisting temperature is about 900°C. The optimal operating conditions for stable catalytic combustion were obtained by means of analyzing the catalytic combustion region, the temperature distribution, and the combustion efficiency.

Studies of surface and gas reactions in a catalytically stabilized combustor

A numerical investigation of a catalytically stabilized thermal (CST) combustor was conducted for a multichannel catalyst bed, and both the catalyst bed and thermal combustor were simultaneously modeled. The numerical model handled the coupling of the surface and gas reaction in the catalyst bed as well as the gas reaction in the thermal combustor. The behavior of the catalyst bed was investigated at a variety of operating conditions, and location of the flame in the CST combustor was investigated via an analysis of the distribution of CO concentration. Through parametric analyses of the flame position, it was possible to derive a criterion to determine whether the flame is present in the catalyst bed or the thermal combustor for a given inlet condition. The results showed that the maximum inlet temperature at which the flame is located in the thermal combustor increased with increasing inlet velocity.

Characteristics of surface reaction and heat transfer in a catalytic heat exchanger

The characteristics of a catalytic heat exchanger which can integrate heat generation and heat exchange were numerically investigated. The catalytic heat exchanger was modeled in a three-dimensional, steady state and laminar flow system, including the surface reaction on catalytic fins. The surface reaction was modeled with one-step reaction incorporating the diffusion effect on the catalysts. The surface reaction on catalytic fins was significantly influenced by the heat transfer rate in fin tubes. In order to achieve both the complete conversion of the mixture and the efficient recovery of heat generated, the results suggest that the surface reaction should be completed in the first stage of the catalytic heat exchanger and the second stage should function only as a heat recovery. The effects of the catalytic fin configuration on the catalytic combustion performance were also investigated at a variety of operating conditions.

Development of a catalytic combustor with heat exchanger

Catalytic combustion is thought to be a considerable improvement on the traditional one under specific conditions. Due to its special features, catalytic combustion has two strong points compared to flame: no NOx emission and high reaction efficiency. However, the preheating process of catalytic combustion is an obstacle that deteriorates profitability in operation. So the HTHE (High Temperature Heat Exchanger) is adapted to the system to reinforce the preheating process, and we show that the catalytic combustion is maintained steadily without exceptional heat injection. As a result, the stability on the catalytic surface is the most important operational factor. To achieve it, both mixture gas property and temperature distribution should be controlled.