Research On Accounting And Influencing Factors Of Oil Storage Tank VOCs Emissions

In recent years,with the increasingly strict environmental protection policy requirements of "controlling the emissions of volatile organic compounds" in our country,the unorganized emissions of oil storage tanks has become the focus of management and control of petroleum and petrochemical enterprises,scientific and accurate accounting of VOCs emissions become the important premise for further effective governance.VOCs in oil tank area mainly come from breathing loss.The current calculation methods at home and abroad were extensively investigated,according to the principle of breathing loss,and combination with engineering examples,the different methods were used to calculated annual breathing loss of floating roof tank and ordered by accuracy.According to the four calculation methods at home and abroad,the sensitivity analysis of the parameters affecting the amount of breathing loss in the storage tank is carried out,the main and secondary influencing factors are determined,and the accuracy and applicability of the four methods are analyzed.Simulation software was used to simulate the wind pressure distribution around the floating roof tank under different wind speeds.It was shown that the stronger the wind,the greater the pressure difference will be,and the more favorable the oil and gas concentration will be.When the wind speed increased from 2 m/s to 20 m/s,the inner wall pressure difference on the upper and lower windward side of the tank increased from 2.2 Pa to 34 Pa.By studying the wind pressure distribution above the floating surface at different storage levels,it was found that when the liquid level increased from 10 m to 18 m,the pressure difference on the upper and lower windward side increased from 12 Pa to 26 Pa.This indicates that the oil level has a great influence on the pressure distribution above the floating roof and further affects the oil and gas diffusion.The oil and gas diffusion in the dome roof tank at different oil inlet speeds is simulated.It shows that the faster the oil inlet speed,the faster the growth of oil and gas volume fraction at the breathing valve.When the oil inlet rate increases from 0.01 m/s to 0.03 m/s,the oil and gas volume fraction at the breathing valve reached 50% time decreased from 183 s to 80 s.At a constant oil inlet speed,by studying on oil and gas diffusion under different initial oil and gas concentrations,it was found that when the initial oil and gas concentration increased from 0% to 30%,the oil and gas volume fraction at the breathing valve reached 50% time decreased from 183 s to 66 s.It shows that the initial oil and gas concentration in the tank also effected on the oil and gas diffusion in the dome roof tank.According to the sequence of the four methods for calculating the annual breathing loss of tanks and the influence rule of the main factors on the oil and gas emissions of tanks obtained from the simulation.It is concluded that the domestic method should be the first choice for VOCs loss accounting of tanks in China.And suggested that the oil level and initial oil and gas concentration should be taken as the parameters of the accounting method,so as to provide a scientific basis for the accounting of VOCs emissions in the tank area.