Calculation of concentrational inflammability limits of individual compounds and their mixtures used in the pharmaceutical industry. IV. Lower imflammability limits of the ethanol-dichloromethane-air system

Abstract

In the present work, we present the results of the experimental investigation of the lower concentrational inflammability limits (Clo w) of the dichloromethane--ethanol--air system. The dependence of the Clo w values on the concentration of dichloromethane has been analytically described on the basis of the assumption of a two-stage oxidation of the components in the flame and the kinetics of the oxidation reactions of carbon monoxide. The Clo w of the ethanol-dichloromethane--air mixtures was experimentally studied at the temperature of the reaction tube of 100~ As the reaction vessel, we used a tube made of a thermostable glass, 60 mm in diameter and 500 mm high. The vapor-air mixture was ignited at the open lower part of the tube. To ensure that the tests would be carried out at elevated temperatures, the reaction tube and the connecting tubes were heated by an electric spiral, placed into an asbestos fettling. The flame propagation in the tube was observed visually through a narrow slit in the fettling, and the lower concentrational inflammability limits were experimentally determined by the "weighed sample" method. A fixed amount of dichloromethane vapors was admitted into a preliminarily evacuated reaction tube. The concentration of these vapors was controlled by a manometer. A calculated weighed sample of ethanol was placed into a small glass container fitted with a spiral tube, and the container into a liquid thermostat whose temperature was maintained at 50-60~ Purified air was passed through this container with the weighed sample of ethanol. The temperature of the thermostat and the flow rate of the air were selected so that a complete evaporation of the sample was ensured up to the end of the filling of the reaction tube. The completeness of the evaporation of the sample was controlled by weighing. After the tube had been filled, the mixture was left to stand for i0 min for more complete mixing of the mixture of ethanol vapors and air with the dichloromethane vapors, and the vapor-air mixture was ignited by an electric spark. In case of failure, the ethanol sample was increased. After the inflammability limit had been obtained, the concentration of dichloromethane was changed, and the experiments were repeated. The volume of the ethanol vapors (Vet) at the temperature of the reaction tube was calculated from the formula Oet'Vo'Po'r (i) Vet = Patm.To.Met ,