The analysis on calculation model of heat-wave velocity during the process of crude oil storage tank fire
The formation mechanism of boilover fire in crude oil storage tank is very complex and harmful. Heat-wave velocity is an important research topic in the boilover fire. After introducing boilover mechanism, the models of heat transfer and heat-wave velocity was built by heat transfer analysis for oil layer. Comparing the calculation results of model with the experimental data, this heat-wave speed calculation model is reasonable. Through the research, several conclusions were found: the main factors that impact heat-wave rate are the viscosity and component of oil, heat of heat-wave comes mainly from thermal radiation of flame; Emulsified water in the oil will not trigger boilover fire normally. Only the heat-wave encountered bottom water cushion at the bottom of the tank, did boilover fire take place. In practice, the heat-wave moving speed can be valued 1m/h to estimate the occurrence time of boilover. The results of this study are important for control and security of boilover fire accident.
Burning of weathering and emulsified oil spills
Abstract In previous works, we described small-scale experiments that dealt with the combustion of fuel slicks on water and provided some features of the events that can lead to boilover. The experiments showed that the violent-eruptive vaporization may be due to boiling nucleation near the heating fuel/water interface that has been superheated, and the mechanisms causing this phenomenon to occur have been discussed. If an attempt is made to burn crude oils, which are multicomponent fuels, the problem becomes complicated with the “weathering” of slicks (progressive evaporation of lighter volatiles) and the possibility to have water-in-oil emulsions. The objective of the present work is to study how the combustion of crude oil-layers floating on water is influenced by the aging of oil (degree of oil evaporation) and the formation of emulsions. The experiments are dealing with burning rate, time to the start of boilover, burned mass ratio and boilover intensity. The results are discussed in relation to the main factors influencing the phenomenon: initial oil-layer thickness and pool diameter. The behavior of weathered crude oil agrees closely with the general behavior of single oils with increasing boiling point (the surface temperature will increase with weathering as the residual crude oil becomes less volatile). In contrast, the case of emulsions is more complex and somewhat difficult to model (thermal breakage of emulsified layers, boilover difficult to discern). Finally, the work is complemented by a study of smoke production during the pre-boilover phase. The procedure permits measurements of exhaust gas composition by means of a flow-through system. Results show that weathering increases both yield of soot and CO but that emulsification decreases these yields. The former effect is due to a residual liquid progressively less volatile, the later to vaporised water interacting chemically in the flame.
Anomalous Annealing Behavior of Arsenic Implanted Silicon as a Function of Dose and Energy
Anomalous annealing behavior of damage in As implanted Si has been investigated by channeling effect measurements. Room temperature As implants with doses from 1014 to 2 × 1016cm-2 at energies ranging from 50 to 250 keV into Si were annealed over the range of 600°C to 1100°C. Anneal temperatures ≥ 950°C reduce the disorder for ion doses of 0.5 to 1 × 1016 cm-2 at energies between 50 and 250 keV. Anomalously high residual disorder was found for the intermediate doses of 2 × 1014 to 2 × 10/cm2 implanted above 100 keV. For this intermediate dose, annealing of implants performed at liquid nitrogen temperatures did not show significant reduction in this damage. However implants at 200° to 300°C indicate a lower amount of damage compared to the room temperature implants.