Toshimitsu Ichinose

Effects of high expansion foam dispersed onto leaked LNG on the atmospheric diffusion of vaporized gas

When LNG leaks from a storage tank, the LNG vapourizes vigorously above the adiabatic concrete floor inside the safety dike and the cryogenic methane diffuses in the atmosphere. It is well known that as the density of a vapourized gas drops, the atmospheric diffusion is enhanced due to buoyancy, and the concentration of vapourized gas along the ground decreases. The present paper is concerned with the ability of Hi-Ex (High Expansion Foam) to raise the temperature (decrease the density) of vapourized cryogenic gas, since the Hi-Ex system is usually applied as a fire protection system at LNG facilities. In the experiments, the liquid nitrogen pool was used to simulate LNG leakage, because the boiling point of liquid nitrogen is close to that for LNG. The small difference in the heat capacity of vapourized gas was taken into account in the evaluation of experimental results. The temperature variations with time of the vapourized gas which penetrated through the Hi-Ex layer were measured. Furthermore, the solidification of the Hi-Ex layer and the formation of flow passages in the Hi-Ex layer, and the change of evaporation rate of liquid after the dispersion of Hi-Ex onto it were examined in detail. Based on these experimental results, the heat balance among Hi-Ex, liquid, and vapourized gas was discussed, and the amount of Hi-Ex required to keep raising the temperature of vapourized cryogenic gas to that at which the density was almost the same as that of atmosphere was estimated.

Evaporation rates of liquid hydrogen and liquid oxygen spilled onto the ground

Abstract The evaporation rates of liquid hydrogen and oxygen spilled onto the ground surface were measured in laboratory tests. To simulate the ground, concrete, dry sand and wet sand layers were used in a vacuum-insulated cylindrical glass vessel. Based on the temperature variations within the layer and detailed observation through the side of the vessel, the heat transfer modes controlling the evaporation phenomenon were elucidated. When a wet sand layer was used, the liquid oxygen or hydrogen did not soak into the layer, because the frozen layer of water between the liquid and the sand layer acted as a barrier. When a concrete layer was used, the liquid vaporized above the layer. In these cases, the evaporation rates were inversely proportional to the square root of the time, except in the early stage just after the start of vaporization. This relationship could be predicted by a simple calculation of heat conduction within the layer. On the other hand, when a dry sand layer was used, liquid oxygen was observed to vaporize while constantly soaking into and rolling up the upper section of the layer. In this case, the evaporation rate was determined simply by the velocity of liquid penetration downward through the sand layer. When liquid hydrogen was used, the liquid did not soak into the dry sand layer, and the evaporation mechanism seemed to be the same as that for the wet sand layer, because the air contained within interparticle cavities in the dry sand layer solidifies at the boiling point of liquid hydrogen.

Biomethanol Production from Forage Grasses, Trees, and Crop Residues

About 12 billion tons of fossil fuels (oil equivalent) are consumed in the world in 2007 (OECD 2010) and these fuels influence the production of acid rain, photochemical smog, and the increase of atmospheric carbon dioxide (CO2). Researchers warn that the rise in the earth’s temperature resulting from increasing atmospheric concentrations of CO2 is likely to be at least 1°C and perhaps as much as 4°C if the CO2 concentration doubles from preindustrial levels during the 21st century (Brown et al. 2000). A second global problem is the likely depletion of fossil fuels in several decades even though new oil resources are being discovered. To address these issues, we need to identify alternative fuel resources. Stabilizing the earth’s climate depends on reducing carbon emissions by shifting from fossil fuels to the direct or indirect use of solar energy. Among the latter, utilization of biofuel is most beneficial because; 1) the solar energy that produces biomass is the final sustainable energy resource; 2) it reduces atmospheric CO2 through photosynthesis and carbon sequestration; 3) even though combustion produces CO2, it does not increase total global CO2; 4) liquid fuels, especially bioethanol and biomethanol, provide petroleum fuel alternatives for various engines and machines; 5) it can be managed to eliminate output of soot and SOx; and 6) in terms of storage, it ranks second to petroleum and is far easier to store than batteries, natural gas and hydrogen. Utilization of biomass to date has been very limited and has primarily included burning wood and the production of bioethanol from sugarcane in Brazil or maize in the USA. The necessary raw materials for bioethanol production by fermentation are obtained from crop plants with high sugar or high starch content. Since these crops are primary sources of human nutrition, we cannot use them indiscriminately for biofuel production when the

Fundamental experiment on the combustion of coal-water mixture and modeling of the process

A fundamental study of the combustion process of coal-water mixtures has been performed. The surface and center temperatures and the weight change of a single droplet under combusion were measured in detail, where the water content, properties of coal, initial diameter of droplet, and external heat flux were parameters. In the experiments, an infrared intensive laser was used as the external heat source to simulate the conditions around the droplets atomized in an actual furnace. Based on the data obtained, the reaction rates in the processes of water vaporization, devolatilization, and char combustion were formulated. For the devolatilization stage, the activation energy derived by assuming a first-order reaction was almost the same as that for the mother coal, but the apparent frequency factor was much, smaller than that for the mother coal by 1/140-1/50. For the stage of char combustion, also, the apparent frequency factor was much smaller. The specific surface area and the micropores in the coal particle were much reduced after undergoing processes of water vaporization and devolatilization. Its possible that the pore would be masked when the water trapped in the pore was escaping from it with the agglomeration of coal particles proceeding. According to the data obtained and the combustion model proposed here, computer simulation codes for the combustion of a single droplet and for the combustion process in a furnace, were written. The calculated results for the temperature variation and the concentrations of oxygen and unburned carbon in the exhaust gas agreed well with the experimental data obtained using a one-dimensional test furnace. This confirms the validity, of the combustion model and reaction data.