Dehydration of Waste Edible Oil by Hydrocyclones.pdf

润滑油多场联合净化装备设计

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This article was downloaded by: Xian Jiaotong UniversityOn: 13 March 2013, At: 00:54Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UKInternational Journal of Green EnergyPublication details, including instructions for authors andsubscription information:/loi/ljge20Dehydration of Waste Edible Oil byHydrocyclonesZ. Bai a , H. Wang a & S. Tu aa Key Lab of Safety Science of Pressurized System, Ministry ofEducation School of Mechanical and Power Engineering, East ChinaUniversity of Science and Technology, Shanghai, ChinaVersion of record first published: 07 Apr 2009.To cite this article: Z. Bai , H. Wang & S. Tu (2009): Dehydration of Waste Edible Oil byHydrocyclones, International Journal of Green Energy, 6:2, 184-191To link to this article: /10.1080/15435070902785001PLEASE SCROLL DOWN FOR ARTICLEFull terms and conditions of use: /page/terms-and-conditionsThis article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden.The publisher does not give any warranty express or implied or make any representationthat the contents will be complete or accurate or up to date. The accuracy of anyinstructions, formulae, and drug doses should be independently verified with primarysources. The publisher shall not be liable for any loss, actions, claims, proceedings,demand, or costs or damages whatsoever or howsoever caused arising directly orindirectly in connection with or arising out of the use of this material.DEHYDRATION OF WASTE EDIBLE OIL BYHYDROCYCLONESZ. Bai, H. Wang, and S. TuKey Lab of Safety Science of Pressurized System, Ministry of Education School ofMechanical and Power Engineering, East China University of Science andTechnology, Shanghai, ChinaWaste edible oil is the high quality material from which biodiesel fuels can be made. Thewater droplets in wasted edible oil affect the processing courses and the product quality. Anew process of waste edible oil dehydration based on hydrocyclone technology has beendesigned. Preliminary industrialexperiments have been carried out to prove the feasibility ofdehydration using a hydrocyclone. The effects of several dimensionless units, such asReynolds number, Euler number, and pressure drop ratio, were studied. An increase inReynolds number will decrease the pressure drop ratio. With an increase in the Reynoldsnumber, the Euler number increases gradually. Under the condition that the Reynoldsnumber of inlet is ranging from 5,000 to 5,800, the water concentration can decrease from0.53.0 vol.% to less than 0.30 vol.%.Keywords: Hydrocyclone separation; Dehydration; Waste edible oilINTRODUCTIONThe amount of waste edible oil collected in all the European Union was estimated tobe about 400,000 tons. However, it is predicted that the collection of vegetable oil will riseand may reach amounts between 700,000 and 1,000,000 tons, and 90% of those edible oilswill be dumped as refuse without collection (Ayhan, 2007; Pinto et al. 2005). It isunreasonable from the viewpoint of resource saving that most of the waste edible oil isdumped without being utilized (with the exception that a small percentage of waste edibleoilisrecycledasarawmaterialofsoap).Moreover,whenthewasteedibleoilisincineratedtogether with combustible refuse, a large amount of suspended particulate matter, such asSOx,NOx,CO2,andCO turning to airpollutants are produced,and it isreported that deadlypoisonous dioxin may be produced. On the other hand, when the waste edible oil is buriedtogether with noncombustible refuse, soil pollution occurs. A part of the waste edible oildumpedfromrestaurants,foodplantsandhomesisactuallydischarged intoriversandlakesand is one of the major causes of water pollution.Inthissense,transesterificationofwasteedibleoilstoproducebiodieselcoulddecreasethewastedisposalproblem.Thewasteedibleoilsservingasrawmaterialincludewrapeseedoil, sesame oil, soybean oil, maize oil, sunflower oil, palm oil, palm kernel oil, coconut oil,International Journal of Green Energy, 6: 184191, 2009Copyright ? Taylor & Francis Group, LLCISSN: 1543-5075 print / 1543-5083 onlineDOI: 10.1080/15435070902785001AddresscorrespondencetoH.Wang,SchoolofMechanicalandPowerEngineering,EastChinaUniversityof Science and Technology, 130 Meilong Road, Shanghai 200237, PR China. E-mail: fbaizs184Downloaded by Xian Jiaotong University at 00:54 13 March 2013 corn oil, safflower oil, etc., and either one of them or a mixture of the mentioned oils isemployed as a raw material. There is no particular requirement regarding the quality of oil,but it is generally preferable that the ble oil has low content of water and solid component.The sedimentation method is a typical method of dewatering waste edible oil. Butlow efficiency and large size are great disadvantages to the sedimentation method. Manyresearch efforts have been taken to study the dewatering of waste edible oil and gainedconsiderable progress, including the centrifuge method (Wang et al. 1997), filtrationmethod (Guu et al. 1997; Tanaka, 2004; Tirmizi et al. 1996), magnetic handling method(Freeman et al. 1994;Shen et al., 1990), and direct current hydrocyclone method (Pratarnetal.2005;Pratarnetal.2006).Butthosetechniqueswerelessusedinindustrialproductionbecause of the complexity of the equipment and low reliability.Then a new process of waste edible oil dehydration that is based on hydrocyclonetechnology was designed. Preliminary experiments have been carried out to prove thefeasibility of dehydration using hydrocyclone. We demonstrate here that water was beingremoved successfully in waste edible oil through hydrocyclones.FUNDAMENTALS OF DEHYDRATION WITH HYDROCYCLONEPrinciple of Hydrocyclone SeparationA hydrocyclone is a device that causes the centrifugal separation of materialscontained in the liquid fed to it (Bai et al. 2006; Cullivan, et al. 2003; Firth 2003;Habibian et al. 2008). These materials are normally in the form of solid particles but mayalso be gas bubbles, oil, or others. The feeds are separated by the induced centrifugal forceinside the hydrocyclone body and mainly according to their density, size, and shape.Unlike other centrifugal machines, hydrocyclones have no moving parts. The separa-tion driving force comes from the transformation of the static energy of the fluid (fluidpressure) into dynamic energy (fluid velocity).A hydrocyclone body consists of two parts: a cylindrical part and a conical part.Design depends on both the nature of the separation and the quality of effluent desired. Theapplications of hydrocyclones are principally the separation of solid suspended matter andthe clarification of liquid phases. Figure 1 shows the operation of a hydrocyclone designedfor liquid-liquid separation. The fluid is injected tangentially at the top of the hydrocycloneand cause centrifugal forces to accelerate particles toward the walls. As the fluid passesthrough the hydrocyclone in a spiral fashion, large or dense particles are forced against thewallandmigratedownwardstotheunderflow.Fineorlowdensityparticlesaresweptintoasecond inner spiral that moves upward to the overflow.Flow Split and Pressure Drop RatioFlow split of the hydrocyclone is defined the ratio of the volume flow of the under-flow to feed, i.e.,R Qu=Qi 100%(1)where R is the flow split, and Quand Qiare individually the volume flow of the underflowand feed. Under normal operating conditions, there are two distinct pressure drops acrossthe hydrocyclone separator:DEHYDRATION OF WASTE EDIBLE OIL BY HYDROCYCLONES185Downloaded by Xian Jiaotong University at 00:54 13 March 2013 ?pio pi? po(2)and?piu pi? pu(3)where pi, po, puare the pressure in the feed, overflow, and underflow, respectively.The relationshipbetweenthe twopressure drops is also important and canbe used forcontrol purposes. The pressure drop ratio PR ?pio=?piu.Reynolds NumberThe hydrocyclone characteristic Reynolds number could be described as follows:Re ?Dv?(4)where D isthe hydrocyclone diameter; ? and ? are the density and viscosityof liquid,respectively; and v is the hydrocyclone characteristic velocity4Qi?D2.Euler numberThehydrocycloneoverflowcharacteristicEulernumbercouldbedescribedasfollows:Eu pi? po?v2=2(5)UnderflowOverflowFeedInner SpiralOuter SpiralFigure 1 Fluid flow in hydrocyclone.186BAI, WANG, AND TUDownloaded by Xian Jiaotong University at 00:54 13 March 2013 Dehydration EfficiencyThe separationcapability of a hydrocyclone isstronglydetermined by the capacity ofhandling the amount of material reporting to the oversize flowstream and the size distribu-tion of the feed. Although the nominal diameter is the most important parameter inhydrocyclone separation efficiency, the other parameters such as feed diameter, overflowdiameter, and underflow diameter still influence the separation efficiency.The expression used to calculate the overall separating efficiency for W/O separa-tions with classical hydrocyclones isE 1 ?gogi 100(6)where goand giare the volumetric fraction of water in the overflow and feed, respectively.EXPERIMENTALMaterialsTable 1 shows the properties of waste edible oil.Hydrocyclone GeometryThe swirl chamber diameter D of the hydrocyclone was 35 mm, the cone angle was10?.DimensionsofhydrocycloneisshowninTable2.Hydrocyclonehavetwosymmetricalrectangular inlet (5mm 10mm).Flow DiagramThe schematic diagram of the experimental apparatus is illustrated in Figure 2.Wastewater and contaminants are discharged from the bottom of hydrocyclones to thewastewater treatment facility. The dehydration edible oil is continuously drawn from thetop of hydrocyclones and sent to the next procedure. Dehydration efficiency was deter-mined by measuring water concentration in the feed dispersion as well as in the overflowand underflow.Table 1 Properties of edible oil.MaterialDensity/Kg?m-3Viscosity/mm2?s-1Water concentration /%Waste edible oil875 (25?C)Table 2 Geometry of hydrocyclone.Do/DDu/DLs/DL/DLu/D0.4290.2860.28610.888.56Note: 1. D, Do, Durefer to the diameters of swirl chamber, tail pipe, and underflow orifice respectively.2. Ls, L, Lurefer to the lengths of swirl chamber, taper, and tail pipe respectively.DEHYDRATION OF WASTE EDIBLE OIL BY HYDROCYCLONES187Downloaded by Xian Jiaotong University at 00:54 13 March 2013 RESULTS AND DISCUSSIONPressure CharacteristicsPressure drop ratio vs. Reynolds number. The relationship between pressuredropratio andReynoldsnumberisshowninFigure3. Forthe same flowsplit R,an increasein the Reynolds number will decrease the pressure drop ratio. When a Reynolds number ismore than 6,000, as the Reynolds number increases, the decrease in pressure drop ratio isgentle. This shows that the value of two pressure drops is approaching with the increase offlow rate.Euler number vs. Reynolds number. The relationship between Euler numberand Reynolds number is shown in Figure 4. As can be seen, with an increase in Reynoldsnumber, Euler number increases gradually. This shows that an increase of flow rate willincrease the value of ?pio.Separating PerformanceEffect of Reynolds number on dehydration efficiency. The Reynolds num-berisakeyoperatingcharacteristicandhasadistincteffectonthedehydrationefficiencyofthe hydrocyclone. Figure 5 shows the relationship between the Reynolds number anddehydration efficiency. Under the condition that the Reynolds number is less than 5,400,an increase in Reynolds number will improve the separating efficiency. The separatingefficiency will reachits maximum when the Reynolds number is close to 5,400.Furtherincreases in the Reynolds number will cause performance deterioration. This occurs for thefollowing reasons:Edible oilDehydration edible oilOily wastewaterHydrocycloneFigure 2 Diagram of crude desaltingdevice in atmospheric and vacuum distillation unit.3000400050006000700080001.021.031.041.051.061.071.081.09PRReR=1%R=3%Figure 3 Pressure drop ratio vs. Reynolds number.188BAI, WANG, AND TUDownloaded by Xian Jiaotong University at 00:54 13 March 2013 1. Atveryhighflowrates,intenseemulsificationoccurred.Itisattributedtotheshearforcethat caused size reduction among the liquid particles. When emulsification occurs, thefunction of the hydrocyclone is reduced to separating a dense emulsion from a lighteremulsion of an essentially homogeneous mixture.2. A certain minimum flow rate is necessary to set up the vortex motion and to establishcentrifugal separation forces that grow in intensity as the flow rate increases andimprove the separating efficiency.Effect of Euler number on dehydration efficiency. Figure 6 shows the rela-tionship between Euler number and dehydration efficiency. Typically, as the Euler numberincreases, the efficiency of separation increases and reaches maximum when Euler numberis 1,800. Further increases in Euler number will eventually cause the efficiency to dropsharply.From the results of dehydration present in Table 3, it can be seen that dehydrationefficiency range from 80% to 94% with a feed flow rate of 2.7,3.0 m3/h. The waterconcentrations can be reduced to the range of 0.100.30 vol.%.3500 40004500 5000 5500 60006500 700080010001200140016001800200022002400EuReFigure 4 Euler number vs Reynolds number.40004400480052005600600064007880828486889092E/%ReFigure 5 Reynolds number vs. dehydration efficiency.DEHYDRATION OF WASTE EDIBLE OIL BY HYDROCYCLONES189Downloaded by Xian Jiaotong University at 00:54 13 March 2013 CONCLUSIONSIn the present article, a new process of waste edible oil dehydration based onhydrocyclonetechnologyisdesigned.Preliminaryindustrialexperimentshavebeencarriedout to verify the process. It is found that the Reynolds number has a distinct effect on thedehydrationefficiencyofthe hydrocyclone.UndertheconditionofaReynoldsnumberlessthan 5,400, an increase in Reynolds number will improve the separating efficiency. Theseparating efficiency reaches its maximum when the Reynolds number is close to 5,400,beyond which further increases in Reynolds number will cause performance deterioration.Under the condition that the Reynolds number of inlet is ranging from 5,000 to 5,800, thewater concentrations can decrease from 0.53.0 vol.% to less than 0.30 vol.%. It isdemonstrated that the water can be removed successfully from waste edible oil throughhydrocyclones.REFERENCESAyhan, D. 2007. Recent Developments in Biodiesel Fuels. International Journal of Green Energy 4(1): 1526.Bai,Z.-andH.Wang.2006.Theexperimentsfordesaltinganddewateringofcrudebyhydrocyclones.Chinese Acta Petrolei Sinica 22 (4): 5660.Cullivan, J. C., R. A. Williams, and C. R. Cross. 2003. New insights into hydrocyclone operation.Particulate Science and Technology 21: 83103.Firth, B. 2003. Hydrocyclones in dewatering circuits. Minerals Engineering 16: 115120.800 1000 1200 1400 1600 1800 2000 2200 2400707580859095E/%EuFigure 6 Euler number vs dehydration efficiency.Table 3 Results of waste edible oil dehydration.No.Qi/m3?h-1gigoE/%12.960.80.108822.811.60.159132.922.70.159442.852.30.29152.932.50.2490190BAI, WANG, AND TUDownloaded by Xian Jiaotong University at 00:54 13 March 2013 Freeman, R. J., N. A. Rowson, T. J. Veasev, and I. R. Harris. 1994. Development of a magnetichydrocycloneforprocessingfinely-groundmagne
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