| The evaporation loss of light fuel oil results in energy waste, environmental pollution,health hazards, safety hazards and oil quality reduction. First, in this paper the soft-floatingroof tank technology about the evaporation loss of light fuel oil regarded as the object of study,relevant theoretical and experimental researches were done for the two main influencingfactors of oil evaporation loss, i.e. oil evaporation surface area and the oil surface temperature.Secondly, surface fluorination property, hydrophobic property, oleophobic property and otherbarrier properties of the soft-floating roofs were systematically studied. Then the process ofbreathing loss reduction by the soft-floating roof was analyzed through a phase-changingtemperature control test. Finally, independence-designed gas chromatographic oil-gas onlinedetection system and the soft-floating roof simulation tank were used indoors and outdoors tostudy the actual effect of the soft-floating roof tank technology in controlling the evaporationloss of light fuel oil.1. In line with essential and influencing factors of the evaporation of light fuel oil,distribution of the oil-gas concentration in the gas space of a tank was analyzed. A evaporationloss correction formula based on surface coverage was deducted. According to the result ofcomparison between the example verification result and the practical loss, the loss calculatedthrough the Waliophsis formula and the practical loss had a difference of21%; the losscalculated through the deduced formula and the practical loss had a difference of7.7%,presenting a difference smaller than the difference based on the original formula. Thedifferences between the losses obtained through calculation and the practical loss were mainlybecause of a non-stable state of physical quantities of substances such as mediums in the tank.2. The24-hour temperature changes of all positions of each vertical tank on the airfieldbelong to jinan air force were measured. The tank wall temperature remained basicallyunchanged. There is a temperature difference of4.5oC in the top oil, and no temperaturedifference below the oil line about10cm. There ia a temperature difference up to32oC in themetallic surface of the tank top. The temperature difference in the oil-gas space dropped in agradient way, which was about20oC at the top, about17oC in the middle and about13oC atthe bottom. According to the experiment result, temperature change of the oil-gas space of thevertical metallic tank was mainly contributed by solar radiation and seasonally influenced bythe atmospheric environment, the tank wall and the tank wall foundation. Matlab curve fittingwas done for the internal oil-gas temperatures of tanks of the airport oil terminals of Air Forceof the Jinan Military Area Command and Air Force of the Chengdu Military Area Command. According to the curve fitting result, the oil-gas temperatures showed a cosine change law andthe correlation coefficient was about0.8. The initial phase between the air temperature and thetank gas temperature is about-0.4for the tanks on the airport oil terminal of Air Force of theJinan Military Area Command, or about-0.8for the tanks on the airport oil terminal of AirForce of the Chengdu Military Area Command. Through ANSYS, a one-dimensional steadyheat transfer model was established and a temperature change equation was obtained. Thedistribution law of internal temperature field of the tank was obtained through a trendapproaching method. According to the model, the oil-gas temperature and the oil temperaturein the tank have a linear relation in the vertical direction; the oil-gas temperature is greatlylinearly graded; the oil surface temperature is mainly influenced by the oil-gas temperature.3. Chemical functional group and surface properties of the soft-floating roof hollow ballswere analyzed with the help of an FTIR (FT-IR) spectrometer, a scanning electron microscopy(SEM), an X-ray photoelectron spectroscopy (XPS) analyzer and a contact angle (CA) analyzer.A room-temperature barrier test and a temperature-rising barrier test were done to check barrierproperty of the soft-floating roof hollow ball. According to the analysis and test results, afterthe soft-floating roof HDPE hollow balls were directly fluorinated, characteristic absorptionpeak of the carbon-fluorine (C-F) bond would appear in the position of1,000-1,200cm-1and afluorinated layer, a boundary layer and an un-fluorinated layer would appear on the surfacelayer; with increase of concentration, temperature and time of the fluorination, the fluorinatedlayer increased non-linearly, but excessive increases of concentration and temperature of thefluorination would result in uneven thickness and poor smoothness of the fluorinated layer;after the direct fluorination, the fluorinated HDPE surface had a larger F/C ratio and becamemore hydrophobic and the contact angle increased from78.5°to90.0°. Meanwhile, withincrease of the fluorinated thickness from5.07μm to7.86μm, the contact angle furtherincreased from90.0°to104.5°. According to results of the room-temperature barrier test andthe temperature-rising barrier test, with increase of its fluorine content, the fluorinated layerhad better penetration resistance and less frequent hardness change.4. Temperature change of the oil surface was suppressed, breathing loss and theevaporation loss of the light fuel oil was reduced with the help of the phase-changing materialsadded in the soft-floating roof hollow balls. Compared with data of the blank test, the heatingcurve added with soft-floating changed dramatically at about28oC; the cooling effect was alittle better with rise of the bath temperature (the higher the external temperature, the better thecooling effect would be); increase of quantity of the breathing floating roof hollow balls didnot reduce the evaporation loss significantly; when temperature of the constant temperaturebath kept at35oC to45oC, the oil temperature dropped by1.5oC to4.1oC at most in the same heating condition.5. A gas chromatographic oil-gas online detection system was established and tests weredone with it in the conditions of room temperature, constant temperature, controlledtemperature, changing temperautre, etc. According to the test results, in the constanttemperature condition, the oil-gas content change curve showed a linear relation; in thecontrolled temperature condition, the curve was S-shaped; in the room temperature conditionor the changing temperature condition, the curve showed a cosine relation. Time efficiency wascalculated when oil vapor was saturated in the soft-floating roof simulation tank covered withhollow balls: It was71%at a constant temperature of30oC, or62%at a constant temperatureof50oC, or71%in the controlled temperature condition. The oil temperature and the oil-gasevaporation was directly proportional: posterity of the oil temperature resulted in posterity ofthe oil-gas content.6. Evaporation suppression effect of soft-floating roofs for light fuel oil was studied inreal outdoor conditions (such as temperature, humidity and air pressure) through a soft-floatingroof simulation tank detection system. According to the test data, the simulation tanks coveredwith the floating roof hollow balls showed an obvious effect in suppressing the oilevaporation loss, the maximum value of oil evaporation supperession rate was71.4%and thefinal value was kept on around30%after dropping with decrease of light component in the oil.In outdoor conditions, the simulation tanks were mainly influenced by factors such as solarradiation and temperature difference. |
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