• Transactions of the Korean hydrogen and new energy society
• /
• v.9 no.2
• /
• pp.53-64
• /
• 1998

Thermal analysis on a Linde-Hampson hydrogen liquefaction system using cryogenic refrigerators as precooling has been carried out. Three commercially available models of cryogenic refrigerators, such as CTI l020CP, CVI CGR009 and CVI CGR011, are considered in the performance analysis. The effect of ortho-para conversion process during hydrogen liquefaction is also studied in detail. The results obtained indicate that the optimal hydrogen mass flow rate and the optimal compressed pressure exist for the maximum hydrogen liquefaction rate. The optimal compressed pressure is increased in the range of 80 - 120 bar with an increase in the hydrogen mass flow rate. It is also found that better performance could be obtained with a cryogenic refrigerator, which produces high cooling capacity at precooling temperature in the range of 80 - 100 K.

• Transactions of the Korean hydrogen and new energy society
• /
• v.14 no.3
• /
• pp.207-216
• /
• 2003

By using the electrochemical method, the relation between the deformation and the geometrical shape, and the effect of cold work on hydrogen absorption-desorption cycling in palladium were investigated, In order to study this problem, four kinds of the Pd specimens used were plates and bars as cold worked and annealed states. As results, it is found that the deformation of thickness direction in the palladium plates increased whereas other lateral directions decreased. But the palladium bars showed the same deformation ratio in all directions because of uniform distribution of the $\beta$ phase. Grains in the plate specimens were greatly deformed after hydrogenation cycling whereas grains in the bar specimens were pulverized. Also, deterioration of the hydrogen absorption rate of the bar specimen was larger than the plate specimen. And the effect of cold work on hydrogen absorption capacity was relatively small.

• Transactions of the Korean hydrogen and new energy society
• /
• v.14 no.2
• /
• pp.146-154
• /
• 2003

The hybrids of zeolite and metal hydride were prepared to improve the absorption properties as media for hydrogen storage. The zeolites which was deposited on the surface by metal hydride vapor showed excellent absorption properties and sodalite was proved to be better than zeolite-A in the reaction velocity and hydrogen storage capacity. This suggests the metal hydride could be used effectively as catalytic active material for enhancing the hydrogen storage in zeolite containing $\alpha$-cages and furthermore the hydrogen molecules have preference tobe occluded in their cavities containing $\alpha$-cages more effectively than that containing a and $\beta$-cages.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.9-12
• /
• 2006

We performed molecular dynamics simulations on the conventional MOF, IRMOF-14 and the catenated MOF with two MOF chains, IRMOF13, to find out rational design and synthetic strategies toward efficient hydrogen storage materials. The molecular dynamics calculations were done using Universal force fields and the analysis of result was performed during the NVE dynamics after preliminary NVT dynamics at 77K. The results showed the density of adsorbed hydrogen molecules was increased in the various pores created by catenation of MOFs while the large amount of volume in conventional MOF was not effectively utilized to store hydrogen. Those calculation results commonly showed the proper control of pore si Be for hydrogen storage into MOF by catenation would be one of the efficient ways to increase hydrogen capacity of MOFs.

• Applied Biological Chemistry
• /
• v.2
• /
• pp.45-52
• /
• 1961

The decomposition of malathion in dust for mulations prepared from four Korean tales as carriers during storage period has been studied. Amberlite CG-120, a cation exchange resin . which has higher cation exchange capacity than tales, was also used as a carrier in hope of finding out the effect of nagative charge upon the decomposition of malathion. Besides the original talc powders obtained directly from the mines, the hydrogen ion saturated forms were also used as carriers for comparisonal study. The saturated ions for the resin were hydrogen, sodium and magnesium. As the physical properties of the tales, colloid content, water adsorption capacity, PH, specific surface, phosphate fixing capacity and exchangeable canons were determined, and these properties were correlated with the amount of the decomposition. Following results were obtained from the experiment. 1. The malathion in the talc in dust was found to decompose around 10-15% ofthe total withina month. About 50% of the decom position that took place after a month was found to occur within a week. 2. The resin which has higher cation exchange capacity than the tales was highly effective in the decomposition of malathion compared with the tales. 3. In every case the saturation of the exchange complexes with hydrogen ion greatly accelerated the decomposition of malathion. 4. The most highly correlated physical properties with the decomposition were colloid content and specific surface of the tales. 5. The water adsorption and phosphate fixing capacities of the tales were found not to correlate with the amount of malathion decomposed. From the experimental results it was concluded that the active negative spots on the colloidal tales or the resin attract the electropositive phosphorus atom in a malathion molecule thereby inducing the decomposition easier. The presence of hydrogen ion nearby might cause a catalytic effect in the decomposition of malathion.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.746-752
• /
• 2017

High test hydrogen peroxide has been widely developed as green propellant for thrusters. Hydrogen peroxide is decomposed in the catalyst bed to produce the thrust. Catalyst bed design optimization is considered through existing model for catalyst beds. To verify the model, static firing tests were conducted under various conditions using a 100 N scale $H_2O_2$ monopropellant thruster. Temperature and pressure estimations from the model were well correlated to the experimental data. The model is used to obtain optimal design parameters by analyzing the catalyst capacity and pressure drop data for various simulated conditions. Catalyst beds can be optimized from the analysis of the catalyst capacity and pressure drop correlation through catalyst bed modeling.

• Journal of the Korean Electrochemical Society
• /
• v.3 no.2
• /
• pp.72-75
• /
• 2000

For the purpose of developing the non-stoichiometric Zr-based Laves phase alloy with higher capacity and better performance for electrochemical application, extensive work has been carried out in KAIST. After careful alloy design of $ZrMn_2-based$ hydrogen storage alloys through varing their stoichiometry while susbstituting or adding some alloying elements, the $Zr-Ti-(Lh-V-Ni)_{2.2},\;Zr-Ti-(Mn-V-Cr-Ni)_{1.8\pm0.1}$ with high capacity and better performance was developed. Consequently the $Zr-Ti-(Mn-V-Ni)_{2.2}$ alloy has a high discharge capacity of 394mAh/g and shows a high rate capability equaling to that of commercialized $AB_5$ type alloys. On the other hand, in order to develop the hydrogen storage alloy with higher discharge capacity, the hypo-stoichiometric $Zr(Mn-V-Ni)_{2-\alpha}$ alloys substituted by Ti are under developing. As the result of competitive roles of Ti and $stocihiometry({\alpha})$, the discharge capacity of $Zr-Ti-(Mn-V-Cr-Ni)_{l.8\pm0.1}$ alloys is about 400mAh/g(410 mAh/g, which shows the highest level of performance in the Zr-based alloy developed. Our sequential endeavor is improving the shortcoming of Zr-based Laves phase alloy for commercialization, i.e., poor activation property and low rate capability, etc. It is therefore believed that the commercialization of Zr-based Laves phase hydrogen storage alloy for Ni-MH rechargeable battery is in near future.

• Transactions of the Korean hydrogen and new energy society
• /
• v.30 no.3
• /
• pp.251-259
• /
• 2019

The aim of this study is to evaluate the economic feasibility of domestic on-site steam methane reforming (SMR) hydrogen refueling stations. We evaluated the levelized cost of hydrogen (LCOH) for the SMR hydrogen refueling stations, which have production capacities of 100 kg/day (SMR 100), 200 kg/day (SMR 200), and 500 kg/day (SMR 500) utilizing the scale factor. The main results indicated that the LCOH of SMR 100, SMR 200, and SMR 500 were 14,367 won/kg, 11,122 won/kg, and 8,157 won/kg, if the utilizations of hydrogen stations were 70%. These results imply that the production capacity of the domestic SMR hydrogen station should be greater than 500 kg/day to compete with other hydrogen stations when we consider the current sale price of hydrogen at the hydrogen stations.

• Journal of the Korean Applied Science and Technology
• /
• v.19 no.3
• /
• pp.213-221
• /
• 2002

Activated carbons with high surface area of 2,600 $m^{2}/g$ and high pore volume of 1.2 cc/g could be prepared by KOH activation of rice hulls at a KOH:char ratio of 4:1 and $850^{\circ}C$. In order to increase the adsorption capacity of hydrogen sulfide, which is one of the major malodorous component in the waste water treatment process, various contents of $Na_{2}CO_{3}$ and $KIO_{3}$ were impregnated to the rice-hull activated carbon. The impregnated activated carbon with 5 wt.% of $Na_{2}CO_{3}$ showed improved $H_{2}S$ adsorption capacity of 75 mg/g which is twice of that for the activated carbon without impregnation and the impregnated activated carbon with 2.4 wt.% of $KIO_{3}$ showed even higher $H_{2}S$ adsorption capacity of 97 mg/g. The improvement of $H_{2}S$ adsorption capacity by the introduction of those chemicals could be due to the $H_{2}S$ oxidation and chemical reaction with impregnated materials in addition to the physical adsorption of activated carbon.

• Clean Technology
• /
• v.21 no.2
• /
• pp.108-116
• /
• 2015

Hydrogen sulfide and ammonia are one of the common malodorous compounds that can be found in emissions from many sewages treatment plants and industrial plants. Therefore, removing these harmful gases from emissions is of significance in both life and industry because they can cause health problems to human and detrimental effects on the catalysts. In this work, pyrolytic carbon blacks from waste tires were used to develop adsorbent with good adsorption capacity for removal of hydrogen and ammonia. Pellet-type adsorbents were prepared by a mixture of carbon black, metal oxide and sodium hydroxide or hydrochloric acid, and their adsorption capacities were estimated by using breakthrough curve of a continuous fixed bed adsorption column at ambient condition. The adsorbent manufactured with a mixture of carbon black, iron oxide(III) and sodium hydroxide showed the maximum working capacity of hydrogen sulfide. For ammonia, maximum working capacity was obtained by the adsorbent manufactured with a mixture of carbon black, copper oxide(II) and hydrochloric acid.