Study On Vapor-oil Mass Transfer Behavior And Vapor Emission Characteristics In Sloshing Tank

The oil evaporation and vapor emissions are related to the safety and environmental protection of oil tanker loading operations.In this paper,a three-dimensional numerical model was developed according to the study of the behavior of oil evaporation and oil and gas emission in liquid cargo tanks during loading process.,the theoretical analysis and numerical simulation were used to explore the effects of evaporation of oil and vapor emission from the breather hole caused by the loading rate and sloshing intensity of cargo tank.Firstly,based on the theoretical analysis of oil tanker loading process under the actual sea conditions,the oil tanker type,the sloshing factor and the oil property were determined.The film theory and the theory of disturbance energy were used to describe the phenomenon of oil evaporation,and to analyze the oil evaporation and vapor migration.Considering the laminar flow characteristics of cargo under the static loading condition,a oil evaporation model suitable for lamiar flow was proposed based on Fick's law,VOF multiphase flow model,film theory,and disturbance energy theory.According to the turbulence characteristics of oil in sloshing cargo tank,the dynamic mesh technology was applied to solve the sloshing motion.Secondly,based on the selected numerical model,the oil evaporation and vapor emission problems caused by the loading rate and the sloshing cargo tank were solved respectively.The evaporation model and the numerical methods were verified by the experimental results respectively.Further,the characteristics of vapor field and its influence on gas-liquid mass transfer were analyzed,and the variation characteristics of vapor concentration at the breather hole are analyzed by convection diffusion theory.Thirdly,by analyzing the variation characteristics of the disturbance energy and sloshing intensity per unit volum produced by different loading rates and sloshing strength,and applying to the sloshing intensity of fluid can be measured by sloshing,the energy transfer relationship between disturbance energy and sloshing intensity was obtained,as well as the uniform relationship of generating sloshing energy caused by loading rates and sloshing intensity of liquid cargo.Based on this,the influence characteristics of oil evaporation and tank ventilation were studied,and the evaporation rate was obtained.Furthermore,the influence of oil evaporation and the permeability of cargo tank was investigated.All in all,this paper not only provides a theoretical basis for reducing evaporation loss during the loading of oil tankers,and takes a instructive significance for the safe operation and pollution control of liquid cargoes.