Jong-Ho Moon

Simultaneous removal of H2S and COS using Zn-based solid sorbents in the bench-scale continuous hot gas desulfurization system integrated with a coal gasifier

A bench-scale continuous hot gas desulfurization system using Zn-based solid sorbents was developed to remove H2S and COS simultaneously in a 110 Nm3/h of real coal-gasified syngas. The bench-scale unit, which consisted of a fast fluidized-bed type desulfurizer and a bubbling fluidized-bed type regenerator, was integrated with a 3 ton/day-scale coal gasifier installed at the Institute for Advanced Engineering. The solid sorbents, which consisted of 50 wt% of ZnO for sulfides sorption and 50 wt% of supporters for mechanical strength, were manufactured by a spray drying method and supplied by Korea Electric Power Corporation Research Institute. The bench-scale unit was designed to operate at the high temperature of above 500 °C and the high pressure of 19 kgf/cm2 gauge. Integration of the bench-scale unit with a coal gasifier was first performed to investigate the operation stability of the integrated system. And the long-term continuous operation above 30 h was performed to analyze the desulfurization performance of the bench-scale unit. The concentration of both H2S and COS in the syngas was measured by a continuous UV gas analyzer and an online gas chromatograph and that of both H2S and COS after desulfurization was measured by an online gas chromatograph. Through the above 30-h continuous operation, the sulfur removal reached up to 99.9%.

Performance analysis of K-based KEP-CO2P1 solid sorbents in a bench-scale continuous dry-sorbent CO2 capture process

Korea Institute of Energy Research (KIER) and Korea Electric Power Corporation Research Institute (KEPCORI) have been developing a CO2 capture technology using dry sorbents. In this study, KEP-CO2P1, a potassium-based dry sorbent manufactured by a spray-drying method, was used. We employed a bench-scale dry-sorbent CO2 capture fluidized-bed process capable of capturing 0.5 ton CO2/day at most. We investigated the sorbent performance in continuous operation mode with solid circulation between a fast fluidized-bed-type carbonator and a bubbling fluidized-bed-type regenerator. We used a slip stream of a real flue gas from 2MWe coal-fired circulating fluidized-bed (CFB) power facilities installed at KIER. Throughout more than 50 hours of continuous operation, the temperature of the carbonator was maintained around 70-80 °C using a jacket-type heat exchanger, while that of the regenerator was kept above 180 °C using an electric furnace. The differential pressure of both the carbonator and regenerator was maintained at a stable level. The maximum CO2 removal was greater than 90%, and the average CO2 removal was about 83% during 50 hours of continuous operation.

The Characteristics of Attrition of Absorbents for Pre-combustion CO 2 Capture

Attrition characteristics of absorbents for pre-combustion capture were investigated to check attrition loss of those absorbents and to determine solid circulation direction and the better absorbent. The cumulative attrition losses of two absorbents increased with increasing time. However, attrition loss under a humidified condition was lower than that under a non-humidified condition case. Between two absorbents, attrition loss of PKM1-SU absorbent was higher than that of P4-600 absorbent. The average particle sizes of the attrited particles were less than for two absorbents under a non-humidified condition case, and therefore, we could conclude that the main mechanism of attrition for two absorbents is not fragmentation but abrasion. Based on the results from the test for the effect of humidity on the attrition loss, we selected solid circulation direction from SEWGS reactor to regeneration reactor because the SEWGS reactor contains more water vapor than regeneration reactor. Attrition loss and make-up rate of two absorbents were compared based on the results from sorption capacity tests and attrition tests. Required make-up rate of P4-600 absorbent was lower than that of PKM1-SU absorbent. However, more detail investigation on the optimum regeneration temperature, manufacturing cost, solid circulation rate, regeneration rate, and long-term sorption capacity should be considered to select the best absorbent.

Defect‐Free Mixed‐Matrix Membranes with Hydrophilic Metal‐Organic Polyhedra for Efficient Carbon Dioxide Separation

Defect-free mixed-matrix membranes (MMMs) were prepared by incorporating hydrophilic metal-organic polyhedra (MOPs) into cross-linked polyethylene oxide (XLPEO) for efficient CO2 separation. Hydrophilic MOPs with triethylene glycol pendant groups, which were assembled by 5-tri(ethylene glycol) monomethyl ether isophthalic acid and CuII ions, were uniformly dispersed in XLPEO without particle agglomeration. Compared to conventional neat XLPEO, the homogenous dispersion of EG3 -MOPs in XLPEO enhanced CO2 permeability of MMMs. Upon increasing the amount of EG3 -MOPs, the membrane performance such as CO2 /N2 selectivity was steadily improved because of unsaturated CuII sites at paddle-wheel units, which was confirmed by Cu K-edge XANES and TPD analysis. Therefore, such defect-free MMMs with unsaturated metal sites would contribute to enhance CO2 separation performance.

Performance comparison of aqueous MEA and AMP solutions for biogas upgrading

Two different aqueous amine solutions were applied to CO2 removal from simulated biogas in a lab.-scale continuous absorption process that can handle 5Nm3/hr of gas treatment. The effects of the gas-to-liquid ratio in the absorber and of the temperature of the reboiler on the CO2 removal were analyzed in aqueous MEA and AMP solutions. Since the CO2 loading ratio of AMP solutions is larger than that of MEA solutions for the same absorbent concentration, the AMP solutions have higher CO2 removal efficiency than that of MEA solutions for the same gas-to-liquid ratio and reboiler temperature. Also, the 30 wt% MEA solution has a higher CO2 removal efficiency than that of the 20 wt% MEA solution at the same gas-to-liquid ratio and reboiler temperature. To evaluate the feasibility of biogas upgrading, a commercial simulator, Aspen Plus®, was used to analyze the effects of absorbent concentration, absorbent flow rate at the absorption column, and absorber height on CO2 removal and CH4 purity; the regeneration energy was also evaluated. The results were applied to the design of a pilot-scale biogas upgrading plant that can handle 10,000Nm3/day of biogas treatment.

The effect of noncondensable gas on heat transfer in the preheater of the sewage sludge drying system

We used a shell-and-tube type preheater to investigate the effect of noncondensable gas on heat transfer. In the preheater of the drying system, heat is exchanged between steam-air mixed gas which is dryer outlet gas and sewage sludge. To evaluate the performances of the preheater, water was first used in the tube-side material instead of sewage sludge and steam-air mixed gas in the shell-side material. The test variables were as follows: mixed gas inlet temperatures range from 95 to 120 °C; inlet air content, mair/msteam from 55 to 83%; tube-side water flow rate from 42 to 62 kg/h. The shell-side heat transfer coefficient varied from 150 to 550W/m2K, which corresponds to the amount of noncondensable gas in the steam-air mixed gas and the overall heat transfer coefficient varied from 60 to 210W/m2K. Using sewage sludge as a tube-side material the overall heat transfer coefficient varied from 60 to 130W/m2K and the outlet temperature of sewage sludge was above 90 °C, which is high enough for reducing energy consumption in the dryer by preheating the sewage sludge.

CuY zeolite catalysts prepared by ultrasonication-assisted ion-exchange for oxidative carbonylation of methanol to dimethyl carbonate

The influence of ultrasonication treatment on the catalytic performance of CuY zeolite catalysts was investigated for the liquid-phase oxidative carbonylation of methanol to dimethyl carbonate (DMC). The deammoniation method of NH4Y into HY zeolites was optimized and characterized by elemental analyzer, derivative thermogravimetry, Brunauer-Emmett-Teller (BET) analyzer, and powder X-ray diffractometry, revealing that the HY zeolite deammoniated at 400 °C presented the highest surface area, complete ammonium/proton ion exchange, and no structure collapse, rendering it the best support from all the prepared zeolites. CuY zeolites were prepared via aqueous phase ion exchange with the aid of ultrasonication. Upon ultrasonication, the Cu+ active centers were uniformly dispersed in the Y zeolites, penetrating the core of the zeolite particles in a very short time. In addition to enhancing the Cu dispersity, the ultrasonication treatment influenced the BET surface area, acid amount, Cu+/Cu2+ ratio, and also had a relatively small impact on the Cu loading. Consequently, adequate exposure to ultrasonication was able to increase the conversion rate of methanol into dimethyl carbonate up to 11.4% with a comparable DMC selectivity of 23.7%. This methanol conversion is 2.65 times higher than that obtained without the ultrasonication treatment.

Effect of H 2 S on Reactivity of Oxygen Carrier Particle for Chemical Looping Combustion

>> Effect of H2S on reactivity of oxygen carrier was measured and discussed using fluidized bed reactor and SDN70 oxygen carrier. We could get 100% of fuel conversion and CO2 selectivity even though H2S containing simulated syngas was used as fuel for reduction. Absorbed sulfur was released during oxidation and N2 purge step after oxidation as SO2 form. We could get 100% of fuel conversion and CO2 selectivity during cyclic reduction-oxidation tests up to 10th cycle. However, only 6~7% of sulfur can be removed during oxidation and N2 purge step and 93~94% of sulfur was accumulated in the oxygen carrier. Therefore we could conclude that total removal of sulfur was not possible. SO2 emission during oxidation decreased as the number of cycle increased. Therefore we could expect that the reactivity of oxygen carrier will be decreased with time.

Hydrodynamics of a hybrid circulating fluidized bed reactor with a partitioned loop seal system

A circulating fluidized bed (CFB) with a hybrid design has been developed and optimized for steam hydrogasification. The hybrid CFB is composed of a bubbling fluidized bed (BFB) type combustor and a fast fluidized bed (FB) type gasifier. Char is burnt in the combustor and the generated heat is supplied to the gasifier along with the bed materials. Two different types of fluidized beds are connected to each other with a newly developed partitioned loop seal to avoid direct contact between two separate gas streams flowing in each fluidized bed. Gas mixing tests were carried out with Air and Argon in a cold model hybrid CFB to test the loop seal efficiency. Increase in solid inventory in the loop seal can improve the gas separation efficiency. It can be realized at higher gas velocity in fast bed and with higher solid inventory in the loop seal system. In addition, bed hydrodynamics was investigated with varying gas flow conditions and particle sizes in order to obtain a full understanding of changes of solid holdup in the FB. The solid holdup in the FB increased with increasing gas velocity in the BFB. Conversely, increase in gas velocity in the FB contributed to reducing the solid holdup in the FB. It was observed that changing the particle size of bed material does not have a big impact on hydrodynamic parameters.

Analysis of Adsorption Phenomena of Hydrogen on Carbon Nanotube usint Molecular Simulation

Molecular simulation was performed to evaluate the possibility of hydrogen storage of carbon nanotubes. The equilibrium state of hydrogen adsorbed on carbon nanotubes was simulated by grand canonical Monte Carlo method at constant temperature and pressure. The interaction energy between hydrogen molecule and carbon nanotube was calculated by Lennard-Jones potential model. According to the interaction energy calculated, more hydrogen molecules were adsorbed on the inside than the outside of nanotubes. Whereas the adsorption strength was higher outside than inside. Adsorption capacity was investigated for various temperature and pressure. The maximum capacity of carbon nanotube for hydrogen storage was 2.5wt% at 200 K and 200 bar.