| With the increase of the number of sewage treatment plants,the problem of volatile organic compounds(VOCs)escaping is becoming more and more serious.In order to reduce the harm to human body and environment caused by VOCs volatilization from waste liquid/waste water into the atmosphere,the method of installing a gas collection hood is usually used in industry.At the same time,in order to prevent the explosion caused by excessive VOCs concentration in the hood,a certain flow rate of ventilation is needed.For this system,most scholars still study the open level volatilization model of organic compounds in water,while there are few reports about the closed model of ventilation of waste water pond and gas collection hood in literature.In this thesis,in order to provide theoretical guidance for the design of actual waste liquid/waste water pond and VOCs treatment method,the volatilization of organic compounds in water in the closed model of ventilation of waste water pond and gas collection hood has been studied experimentally.Moreover,relevant physical parameters related to volatilization and micro-interaction energy have been simulated and analyzed by ASPEN and COSMOthermX.In this thesis,by using the law of conservation of mass,the measurement expression of volatilization rate has been obtained by establishing the differential equation and the effect of six factors on the volatilization rate of ethyl acetate,acetone and pyridine have been studied.It has been found that the disturbance of liquid phase has a greater effect on the volatilization rate of the substance with high Henry coefficient;the volatilization rate increases linearly with the air exchange times and the liquid content;the volatilization rate increases exponentially with temperature.The volume of liquid phase has no effect on the volatilization rate and the volatilization rate decreases linearly with the height of the inlet hole from the liquid level.The pressure in the gas phase space in the pool decreases linearly with the increase of the air exchange times and the change is small relative to the atmospheric pressure.The Henry coefficient,the strength of hydrogen bond with water and the hydrogen bond interaction in water of ethyl acetate,acetone,pyridine,benzene and toluene have been simulated and analyzed by COSMOthermX.It has been found that the higher the Henry coefficient is,the higher the volatilization rate of the substance is.The stronger the hydrogen bond formed between organic compounds and water is and the greater the hydrogen bond interaction energy in water is,the lower the volatilization rate is.These are consistent with the preliminary study on volatilization rate of benzene and toluene.In this thesis,Fick's law is used as the expression of diffusion flux and the volatilization rate expression of the closed model of ventilation of waste water pond and gas collection hood is still established based on the two-film theory.When the liquid content is not too high,the experimental study has found that the total volatilization coefficient can be regarded as a constant of temperature only by using the partial pressure of vapor phase which is balanced with the content of liquid phase as the driving force of mass transfer.And the specific expression of the total volatilization coefficient has been fitted accordingly.In the range of liquid phase disturbance linear velocity 0?2.214 m/s,air exchange times 5?80 time/h and temperature 5?35?,when the molar fraction of ethyl acetate in liquid phase is not more than 0.0231%,the total average relative error of the fitting expression of volatilization coefficient is 14.29%.When the molar fraction of acetone in liquid phase is not more than 0.0122%,the total average relative error of the fitting expression of volatilization coefficient is 12.72%.When the molar fraction of pyridine in liquid phase is not more than 0.0231%,the total average relative error of the fitting expression of volatilization coefficient is 7.72%. |
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