Study On Safety Improvement Of The Hot-air Recirculation Drying Process Based On Nitrogen-oxygen Cntrol

Hot air circulation drying process because of its high efficiency, energy savingand other advantages, is widely used in agricultural products, pharmaceutical,chemical and other fields. But in some chemical paint drying process, the combustiblegas volatile produced may accumulate in the baking tank, once explosion mixtures arereleased or leaked to the workshop,which may lead to an explosion when meet theright source and cause personnel injury and equipment damage Especially in recentyears, hot air circulation drying equipment explosion accidents often occurred, it isnecessary to strengthen the improvement of security of the process.In this paper, a set of hot air circulation drying equipment are selected as theresearch object,to improve the security of the hot air circulation drying process bydeterminating the relationship between the explosion limit of combustible matter andoxygen concentration,analysising the eakage accident consequences and using theinherent safety principles.The results show that:(1)By experimental analysis and calculation of the adiabatic flame temperaturemethod to predict the change law of styrene-N2 explosion limit under differenttemperature and inert gas. and analysis the relationship between the concentration ofoxygen and the explosion limits.find that controlling the oxygen concentration is areliable way to reduce explosion hazard,and the maximum allowable oxygenconcentration to be 5% is determined by experiment and theory analysis.(2)Using the CFD numerical simulation to analysis the drying workshop leakageaccident consequences,and emphatically study the concentration of styrene-N2 diffusion with the leakage duration under the emergency ventilation and windowsopen or closed.Raise the vacuum as the key accidental release measure,andsupplemented by strengthening the emergency ventilation to guarantee the safety ofthe drying process.(3) Using the systems engineerig approach to identify the existence of the riskfactors of drying process, and propose the drying process of vacuum pumping by themeans of nitrogen instead of air though controlling the oxygen concentration andreducing the risk of leakage.(4) IBI method is used to evaluate the essential safety of the improved process,find the safety index(down 1.41)and the health index(down 0.5) are effectivelyimproved.Running the discovery process,the new process promoted significantly onthe energy(down to 3.8 kw.h/units) and drying efficiency(shortened to 3~4 hours),theprocess safety improved effectively.