Young-Do Jo

Explosion Characteristics of Hydrogen-Air Mixtures in a Spherical Vessel

Hydrogen has been proposed as a potential fuel to replace fossil fuels and to reduce carbon emissions. This paper presents experimental data on the explosion characteristics of hydrogen‐air mixtures in a 20‐L sphere. This includes the maximum explosion pressure, deflagration index, the exponent parameter of the burning velocity, and the burning parameter. Methods and equations are provided to estimate these parameters.

Dynamic management of human error to reduce total risk

Abstract Safety management in companies at the limit of risk criteria must be implemented in order to survive in the very aggressive and competitive environment of modern society. It implies that the risk in process industries is crossing the limit of safe practices. Most major accidents consist of human errors and mechanical component failures, and cannot be explained by a stochastic coincidence of independent events. This work focuses on the coincidence of human error and mechanical failure to introduce a concept of dynamic management of human error. By the dynamic management of human error during a short period, when a mechanical component is temporarily unavailable during periodic testing or maintenance, the probability of a major accident may be reduced significantly without additional investment on improving safety. For the periodically-tested standby component, the majority of total average unavailability of the component may be recognized by operators or workers as well as maintenance mechanics. During this short period, an appropriate dynamic management of human error for improving human performance temporarily may be very effective in reducing total risk in industries. The dynamic management of human error may be a useful method to prevent loss effectively in the process industries

Flame growth model for confined gas explosion

Large quantities of flammable gases are used in both commercial and residential applications. The risk associated with the use of these materials depends on an understanding of the impacts of an explosion, particularly the pressure‐time history during the explosion. This work provides a model to calculate the pressure‐time history for an explosion in a closed, spherical vessel. The model is expected to be of great benefit for characterizing these explosions and also for the design of explosion vents and other explosion protection systems.

Minimum amount of flammable gas for explosion within a confined space

Leaking of flammable gas in a confined space creates a flammable atmosphere, giving rise to a potential explosion. Accident analysis suggests that some explosions are caused by a quantity of gas significantly much less than the lower explosion limit amount required to fill the whole confined space, which might be attributed to inhomogeneous mixing of the leaked gas. The minimum amount of leaked gas for an explosion is highly dependent on the degree of mixing in the confined space. This paper proposes a method for estimating the minimum amount of flammable gas for explosion, referred to as the Gaussian distribution explosion model (GDEM). The GDEM assumes Gaussian distribution of flammable gas along the height of an enclosure, combustion of gas within flammable limits, and adiabatic mixing in the enclosure. The predicted gas volume for an explosion is tied to the explosion pressure that results in a given building damage level. The results can be applied to estimate the minimum amount of flammable gas and ventilation rate to mitigate the explosion hazard. The GDEM shows that only a very small amount of gas remaining in the confined space may result in a serious gas explosion accident. The results could be applied not only to set the leaking criteria for developing a gas safety appliance but also to determine the ventilation rate and investigate gas accidents under certain conditions.

Explosion hazard analysis in partially confined area

A fuel gas leak in a partially confined area creates a flammable atmosphere and gives rise to an explosion, which is one of the most common accidents in a chemical plant. Observations from accidents suggest that some explosions are caused by a quantity of fuel significantly less than the lower explosion limit (LEL) amount required to fill the whole confined area, which is attributed to inhomogeneous mixing of leaked gas. The minimum amount of leaked gas for explosion is highly dependent on the mixing degree in the area. This paper presents a method for analyzing the explosion hazard in partially confined area with very small amount of leaked gas. Based on explosion limit concentration, the Gaussian distribution model is used to estimate the minimum amount of leak which yields a specified explosion pressure. The method will help in analyzing hazards to develop new safe devices as well as for investigating accidents.

Mechanistic study of hydrogenation of cyclohexene catalyzed by polymer-supported palladium(II) complex in various solvents

Gelular poly(vinylpyridine)-supported palladium catalysts and their analogue have been prepared, and used to study the mechanism of hydrogenation and the solvent effect on catalytic activities. When the polymer-supported Pd catalyst was used in the hydrogenation of cyclohexene, an induction period is observed. The hydrogenation occurs via heterolytic activation of hydrogen. The relationship between the rate of hydrogenation and the solubility parameter of the solvent shows a concave curve with a minimum value at which point the polymer and solvent have similar solubility parameters. The mechanism of hydrogenation of cyclohexene has been suggested.

Hydrogenation of olefins over palladium(II) complexes supported on a modified macroporous polymer bead

Gellular and macroporous polymer supports have been prepared. A modified polymer support has also been prepared by coating the internal pore wall of macroporous poly(styrene-co-divinylbenzene) with lightly crosslinked polymer containing functional groups. The supports were phosphinated and PdCl 2 was supported on them. The supports and catalysts were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. The polymer-supported Pd catalysts were used in the hydrogenation of olefins. The effects of the support structure and solvent were also studied.

HOLLOW GELULAR BEADS OF STYRENE-DIVINYLBENZENE COPOLYMER PREPARED BY SUSPENSION POLYMERIZATION

Hollow gelular beads of styrene-divinylbenzene copolymer have been prepared only by controlling the polymerization temperature and the amount of initiator. A mechanism for the formation of hollow beads is described.

Effect of active site distribution on liquid-phase olefin hydrogenation over polymer-supported palladium complex

Chloromethylated polystyrene beads with different distributions have been prepared and phosphinated. PdCl2 was supported on the phosphinated supports to give polymer-supported Pd complex catalysts with different active site distributions. The effect of active site distribution on catalytic activity was investigated in the hydrogenation of olefins.

ISOMERIZATION OF 1-HEXENE CATALYZED OVER POLYMER-SUPPORTED RUCL2(PPH3)3

Polymer-supported ruthenium catalyst was prepared by anchoring dichlorotris(triphenylphosphine)ruthenium, RuCl2(PPh3)3, onto the phosphinated polystyrene bead. The polymer-supported RuCl2(PPh3)3 could be reused several times with only small loss of catalytic activity in the isomerization of 1-hexene. The activity rather increased during the few initial runs. In both homogeneous and heterogenized catalysts, an induction period was required to initiate the isomerization. The catalyst efficiency was promoted in the mixture of good swelling solvent and potent hydrogen donor. Upon heterogenizing, the activity was reduced by a factor of 2.0-8.2.