Determination of parameters of non-pump ejector gasoline vapor recovery unit

Oil and oil products evaporation losses accompanied by emission of saturated methane hydrocarbons (ethane, propane, butanes, and pentanes) into the atmosphere result both in financial and environmental damage. In particular, it is related to generation of tropospheric ozone that is a greenhouse gas resulted from chemical reactions assisted by saturated hydrocarbons. Therefore, all measures for limitation of light hydro-carbons vapors emissions into the atmosphere are relevant. One of the efficient facilities for solving the task of evaporation losses reduction is vapor recovery units (VRUs). Ejector VRUs are of particular interest with a gas-liquid ejector being their primary element. There are four types of ejector VRUs: with an intermediate separation tank; with a separator built into a tank; with controlled mass transfer and separation; pumpless. The disadvantage of the units of the first three types is high power consumption. Therewith, pumpless ejector VRUs can be used in the places where a margin of stored energy wasted in the process exists. Such places in the main oil products pipelines operation are branch pipes for pumped petrol discharge into associated petroleum depots. However, the methodology for calculating parameters of pumpless ejector units does not exist today. The authors found new dependencies for calculating ejection coefficient, process fluid flow rates, steam-and-gas mixture compression pressure for an arbitrary number of compression stages. It is demonstrated that during petrol discharge from the main oil products pipeline to associated petroleum depots with the use of a pumpless ejector VRU, compression of a significant volume of steam-and-gas mixture displaced from the tanks can be ensured without additional power consumption (4-6 times with the use of three-stage compression design model).