Abstract
Internal floating-roof tanks (IFRTs) are widely used to store light oil and chemical products. However, if the annular-rim gap around the floating deck becomes wider due to abrasion and aging of the sealing arrangement, the static breathing loss from the rim gap will be correspondingly aggravated. To investigate the oil-vapor migration and emissions from an IFRT, the effects of varying both the floating-deck height and wind speed on the oil-vapor diffusion were analyzed by performing numerical simulations and wind-tunnel experiments. The results demonstrate that the gas space volume and the wind speed of an IFRT greatly influence the vapor-loss rate of the IFRT. The larger the gas space volume, the weaker the airflow exchange between the inside and outside of the tank, thereby facilitating oil-vapor accumulation in the gas space of the tank. Furthermore, the loss rate of the IFRT is positively correlated with wind speed. Meanwhile, negative pressures and the vortexes formed on the leeward side of the tank. In addition, the higher concentration areas were mainly on the three vents on the downwind side of the IFRT. The results can provide important theoretical support for the design, management, and improvement of IFRTs.
Highlights
Internal floating-roof tanks (IFRTs) are widely used to store light oil, oil products, and chemical products
To measure the oil-evaporation rate and the wind speed in the tank under different operating conditions, a model IFRT (1000 m3 ) was built according to the length ratio of 32:1, as depicted in where B denotes the total effective ventilation area of the model-tank vents, m2, and D is the inner diameter of the tank, m
The results demonstrate both inside and outside the IFRT in the XY plane are depicted in Figures 10 and 11
Summary
Internal floating-roof tanks (IFRTs) are widely used to store light oil, oil products, and chemical products. These tanks can significantly reduce the evaporating area of the stored liquids owing to the arrangement of a floating deck, thereby effectively restraining oil evaporation and reducing oil-vapor discharge from the tank. Even if an IFRT is equipped with a sealing device on the annular-rim gap between the floating deck and the inner tank wall, the oil surface and the tank gas space cannot be completely isolated for the convenience of the floating deck moving up and down [1]. Oil evaporation from the stored liquid into the tank gas space and vapor emissions from the tank gas space into the atmosphere will cause oil loss, environmental pollution, and potential fire hazards [2].
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