Kyong-Ok Yoo

Optimal temperature of fixed-bed reactor for high temperature removal of hydrogen sulfide

To find optimal temperature of the reaction between H2S gas and ZnO-5 at% Fe2O3 sorbent, the effluent gas from a fixed-bed reactor was analyzed by gas chromatography. The experimental results showed that H2S removal efficiency of sorbent was maximum at 650°C and EDX data were in accordance with this feature. XRD analysis exhibited intriguing phenomenon in that different mechanisms were observed at different temperatures. Chemisorption and chemical reaction was considered to be the main mechanism of H2S removal at 600 C and 650°C, respectively. SEM photographs supported this interesting phenomenon, but unfortunately TGA and DTA results could not distinguish it. To investigate the effect of sorbent deactivation on the reaction rate, deactivating factor was considered.

The system separation method for the optimal target of heat exchanger network synthesis with multiple pinches

This article proposes a new method to the optimal target of a heat exchanger network synthesis problem of which data feature multiple pinch points. The system separation method we suggest here is to subdivide the original system into independent subsystems with one pinch point. The optimal cost target was evaluated and the original pinch rules at each subsystem were employed. The method is illustrated with two examples of which data features two pinch points.

Oxidative regeneration of sulfided sorbent by H2S without emission of SO2

Much SO2, another perilous air pollutant, was emitted during the oxidative regeneration of sulfided sorbent by H2S. In order to prevent emission of SO2, we carried out oxidative regeneration with the physical mixture of CaO and sulfided sorbent and investigated the effect of regeneration temperature and oxygen concentration on the reactivity of CaO with S02. The effluent gases were analyzed by G.C. and the properties of sorbent were characterized by XRD. SEM, TG/DTA and EPMA. Deterioration of reactivity of CaO with S02 resulted in increment of emission of SO12 due to the structural changes of CaO above 750°C and that at 850°C was more severe. Furthermore EPMA and XRD analysis revealed that product layer diffusion through the solid product, CaSO4, was the rate limiting step for CaO sulfidation. The reaction of CaO w:.th SO2 was first order approximately and that was accelerated by high O2 concentration.

Effect of sulfidation/oxidative regeneration cycle on the solid structural changes of sorbent for high-temperature removal of H2S

In order to investigate the effects of sulfidation/oxidative regeneration cycle on the change of structural properties and removal capacity of sorbent, sulfidation/regeneration cycle was carried out up to 15 times in a fixed-bed reactor. The effluent gases from the fixed-bed reactor were analyzed by gas chromatography, and XRD, SEM, and liquid nitrogen physisorption method were used to characterize the reacted sorbents. The sorbent treated first sulfidation/regeneration cycle exhibited maximum specific surface area and the highest H2S removal capacity. Hysteresis of adsorption isotherm of the regenerated sorbent reflected the growth of pores of fresh sorbent and pore size distribution confirmed this fact. Furthermore constant H2S removal capacity was maintained up to 15 times of sulfidation/regeneration cycle.

Correlation of pitzer ion interaction parameters

A new correlation predicting the activity coefficients of aqueous electrolyte solutions between Pitzer ion interaction parameters and ionc properties (ionic charge, radius and entropy) is developed. The substances include uni-uni and uni-bi type of single salts for which data are available. The results of correlation show linear relations for uni-uni type, and quadratic equations for uni-bi type. Many of the trends in the calculated activity coefficients for electrolyte solutions can be correlated with respect to the effect of the ions on the structure of the water and explained by structure-making and -breaking concept. These kinds of correlation may be useful in predicting values for salts that have no measurement of the activity coefficients.