Heavy Gas Leakage And Diffusion Model For Chemical Parks Based On SLAB

The heavy gas refers to kinds of gaseous chemical substances at room temperature, whose density or air mass’density is larger than air. They widely present in all aspects of the chemical industry. Chemical Park is a place where heavy gas is more concentrated, and there is a higher risk to environment. As a result of their higher density, these materials’ leakage and diffusion process is more complex and more dangerous. Some traditional atmospheric dispersion model couldn’t simulate the gravity sedimentation processes, the more applicable model should be used to accomplish this work.Based on the analysis of SLAB model calculation principle, with the dataset of Burro, a foreign experiments on heavy gas releasing, the Error Analysis Method was conducted to characterize the SLAB model’s goodness of fit, which was compared with other two models (ALOHA and HEGADAS) applied for dense gas leakage and diffusion. The result showed the sort of the three models:SLAB> ALOHA> HEGADAS. It can be shown that SLAB model is more advanced in terms of heavy gas leakage and diffusion simulation.The heavy gas releasing experiment was conducted in the Harbor Economic Area with monochlorodifluoromethane (R22). The analysis of the gas samples, which was obtained at downwind different place and different time, was analyzed by the gas chromatograph to form the diffusion curve of R22. The result is quite consistent with the theory, and can provide the base for the parameters optimization of the model.The parameters that need to be optimized was screen out through classifying and analyzing all the parameters for SLAB model, including surface roughness (R), the level of atmospheric stability and the concentration average time (TAV). Regarding the data of R22 releasing experiment as target value, the method that combining objective function and response surface was used to optimize the parameters. The optimized parameters are: R=0.32; Atmospheric stability rating is C; TAV values should be comprehensive determined by the releasing duration (TSD) and the corresponding time for safe exposure standards (TLEVEL).The two forms of hypothetical accident case-benzene leaking by horizontal spraying and chlorine leaking by pool evaporation were simulated respectively by using optimized SLAB model. The accident hazardous zones were divided, using different criteria for safe exposure. The Changes of these hazardous zones’size that under typical weather conditions in different seasons was also analyzed. Based on this, the sensitivity of the hazardous zones’ size to environmental factors were studied, and obtained that:wind speed (S)> Temperature (T)> relative humidity (RH). Therefore, in practical work of emergency management, more targeted emergency plans should be made in advance, based on different environmental conditions.SLAB model can be combined with the Environmental Monitoring System of chemical industry park, it provides decisional information for emergency command of accidents.