Study On Asphalt Fume Emission Mechanism And Control Methods Of Asphalt Mixing Plants

The dust and flue gas in the production of asphalt mixing plants is an important source of air pollutants,of which asphalt fume affect the environment and human health seriously.It is great significance to strict and effective control of asphalt fume emissions.But at present,due to the lack of systematic research on asphalt fume that produced by asphalt mixing plants,many control methods of asphalt fume are not thorough.Therefore,in order to provide theoretical basis for selection and determination of control methods,this paper will analyze and research the producing principle and total quantity of asphalt fume,and analyze the existing treatment methods.Firstly,this paper analyzes the composition of asphalt,and analyzes the mechanism of asphalt fume generation at the asphalt tanks,mixing tank and discharge port from a microscopic point of view.The main mechanism of asphalt fume production is the volatilization of asphalt in asphalt tanks,asphalt encounters thermal decomposition of hot aggregates in mixer,and the pyrolysis of asphalt under the action of photo-oxygen at the discharge port.In asphalt tanks is mainly based on the"dehydrogenation"oxidation reaction.In mixing tank,the asphalt is mainly based on the"oxygenated"oxidation reaction.At discharge port,the asphalt undergoes photooxidation reaction.Secondly,the composition of asphalt fume and the formation process of asphalt fume from the asphalt pyrolysis are analyzed.The formula for the rate of generation of the asphalt fume was obtained by combining knowledge of heat and mass transfer.According to the formula,the relationship between the amount of asphalt fume generation and the heating temperature,the heating time and the amount of asphalt is discussed.The amount of asphalt fume produced at five temperatures,such as 120°C,140°C and so on,was obtained.In order to verify the theoretical calculations,relevant experiments were conducted.The results show that the theoretical curve and the experimental curve have the same variation trend.In addition,the emission factors of asphalt fume during the production of asphalt mixture were studied,and it is the determined to be 6.65×10^-4kg/t in actual production.The amount of asphalt fume production in recent five years was calculated in China.Finally,the various control methods for asphalt fume are analyzed in theory.A single control method cannot achieve the standard emission of asphalt fume,it is necessary to combine two or more methods.Through analysis and comparison of four control devices in practical engineering applications,it is recommended to use the absorption method combining low-temperature plasma and photo-oxidation catalytic oxidation to treat asphalt fume discharged from asphalt mixing plants.