Discussion And Investigation On Gasoline Vapor Condensation Recovery Technique

During the process of oil stockpiling and transportation, a great deal of gasoline vapor will evaporate and emit from the tankers into atmosphere, which will cause serious petrol loss and bring on potential safety risks and environment pollution problems. Gasoline vapor recovery technology not only control oil and gas pollution, but also can produce considerable economic benefits, it is the inevitable requirement for the implementation of national energy-saving and emission-reduction policy. Vapor condensation recovery technique has the advantages of high efficiency, easy maintenance, no secondary pollution, etc. However, most of the existing studies only consider vapor condensing at atmospheric pressure, researches concentrated on the pressurized condensation system are still relatively few. In this paper, the technology of vapor pressurized condensation recovery is discussed and studied in order to meet the national emission requirements and reduce the energy consumption.Firstly, the mathematical models of gasoline vapor condensation recovery process was established and several commonly used real gas equation of state was introduced. The equations of phase equilibrium model for the vapor mixture were presented as well as the thermodynamic parameter models. A vapor condensing recovery simulation program for a representative gasoline vapor sample was programed by Matlab language based on the equations above, and the relationship between vapor condensation characteristics and temperature was analyzed by using the program.Then, three typical types of gasoline vapor samples were selected, whose condensation characteristics and dehydration rate under both atmospheric pressure and high pressure were studied by using the chemical process simulation software Aspen Plus. Result shows that the dehydration efficiency is significantly influenced by system pressure when the pressure is at relatively low level, however, the dehydration efficiency increases slowly when the pressure exceeds a certain point, which is the optimal value for pressurized condensatin system.On the basis of analyzing the different characteristics of direct condensing system (DCS) and pressurized condensing system (PCS), the cooling temperatures were set reasonablely and the refrigeration cycles for the two systems were designed. Comparison of the two systems found mat with the rise of cooling pressure, the total cooling load increases as well as the cooling load undertaken by the air cooler, but the referigartion energy consumption continue to decline since the cooling load undertaken by referigation system decreases. The total energy consumption of the recovery system decreased first and then increased, the minimum valve is between 0.3MPa?0.6MPa, and this value corresponding to the optimal pressure of the pressurized condensing system.Based on the design of vapor pressurized condening recovery system, the investigation of heat recovery device was made as well as the feasibility of heat recovery from the collected liquid. Three kinds of heat recovery methods were proposed, and two of them were mainly analyzed and compared. Results shown that the installation location of heat recovery device has a significant influence on the operating condition and total energy consumption. In terms of the system studied in this paper, it is more appropriate to install the heat recovery devices in front of the pre-cooling stage.