GIS-BASED TOXIC-GAS-VESSEL LEAKAGE, DISPERSION AND SIMULATIONS

摘要

People have been becoming serious of more and more accidents of toxic-gas-vessel leakage and dispersion (TLD) recently. This paper describes a TLD model derived from Gaussian instantaneous leakage model, and then simulates the process of TLD with GIS. When a high-pressure container or vessel breaks, toxic gas (including gasification of high-pressure liquid gas and low-temperature liquid) will leak, and then the gas cloud will disperse in atmosphere. We can calculate the leakage speed of toxic gas, and decide the primary source of dispersion consequently. Assumed that there are N independent equivalent air masses created during the period of leakage, and every air mass subjects to Gausses instantaneous leakage model. Therefore, the effect of TLD is equivalent to the superposition of the N air masses. Thus, the concentration of toxic gas at certain time, location and weather condition can be calculated. After that, concentration isoline can be traced out. We pay more attention to the concentration isolines at half lethal dose, badly injury dose, middle injury dose, and low injury dose. The relevant areas are called death zone, badly injury zone, middle injury zone, and low injury zone respectively. The dispersion trend and affection range can be predicted by illustrating these zones at different time, wind direction and speed. A decision support system of emergency treatment during TLD can be made together with the data of population distribution, traffic, economy, etc. Besides, it provides an analyze tool to forecast or evaluate casualty in TLD.