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使用旋流器对废食用油脱水净化,使用,旋流器,对于,食用油,脱水,净化
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【中文 2860 字】使用旋流器对废食用油脱水净化废物食用油可以作为提炼生物柴油燃料的高质量材料，但是混在油液里边的水滴会影响提炼的过程和提炼出油的质量，现在一项新的使用水力旋流器分离来对油液进行脱水净化的技术方案已经被提出来了，进行的初步工业实验已经证实了使用水力旋流器脱水方案的可行性。现已对如雷诺系数、欧拉数、压降比这几个量对净化过程及结果的影响进行了研究。压降比随雷诺系数增大而降低，欧拉系数随雷诺系数的增大而增大。当雷诺系数在 50005800 这个范围内时，旋流脱水可以使水的浓度降低到 0.5%3.0%每升，有时甚至低于 0.3%。关键词：水力旋流器分离 脱水 废食用油概述欧盟收集起来浪费的食用油估计有 400000 吨，然而,据预测,收集植物油将上升,并可能达到数量有 700000 到 1000000 吨之间,和90%的食用油将被作为垃圾没有收集(世界货币,2007;平托 et al . 2005)。从环保的观点来看，这样把大部分的废食用油倾倒而不被利用是不合理的（除了一小部分废食用油被回收来制作肥皂） ；此外如果大量的废食用油被堆积起来，作为垃圾焚烧处理的话，会产生大量的悬浮颗粒如氮氧化物、二氧化碳、空气污染物和一氧化碳，据报道：二恶英可能会产生致命之毒。另一方面如果废油不做燃烧处理直接一起埋在地上又会污染土地。从餐馆、食品工厂和家庭倾倒出来的废食用油直接排入河流和湖泊也是水污染的主要原因。从这个意义上看，将食用油转化为柴油有利于缓减垃圾处理问题。废食用油主要包括油菜籽油、香油、豆油、玉米油、葵花籽油、棕榈油、棕榈仁油、椰子油、玉米油红花油等，这些一种或集中混合起来并不会影响提炼出柴油的质量，但为保证提炼出柴油的质量，废油中的水含量和固体杂质必须控制在很低的范围内。沉积法是一种典型的对废油脱水的方法，它的主要缺点有两个一是脱水效率低，二是体积比较大，浪费空间。很多学者为废油脱水方法进行研究改进，在方法的改进上有很大的进展，并且取得了很多的研究成果,包括离心机法(王 et al。1997),过滤法(Guu et al。1997;田中,2004;Tirmizi et al。1996),磁处理方法(弗里曼et al。1994;沈 et al。,1990 年),和直流水力旋流器方法(Pratarn et al。2005;Pratarn et al . 2006)。但这些技术在实际的工业生产中很少使用，主要是因为设备的复杂性以及低可靠性。后来一种使用水利旋流器对废油进行脱水的新方法被研究出来了，并且实验已经初步证明了使用水力旋流器对废油进行脱水的可行性，接下来我们在这里介绍一下水力旋流器成功脱水的过程。一、水力旋流器以及它的脱水原理旋流分离原理所谓的水力旋流器，就是一种利用离心技术对流入其中的液体中的杂质进行分离的设备。(Bai et al. 2006; Cullivan, et al. 2003; Firth 2003; Habibian et al. 2008)这些杂质一般是固态，有时也以液态、气态或是其他状态存在。分离主要靠的是水力旋流器使得流进其内部的液体受到离心力的作用，离心力的大小主要取决于组分的密度、大小和形状。水力旋流器和其他离心设备的最主要区别是没有动力设备，离心的主要动力来自液体的高速流入时所具备的的动能。水力旋流器的主筒体由两部分组成，上部分是一个中空的圆柱体，下部分是与圆柱体想通的倒锥体，在对它结构进行设计时既要考虑油和水自然分离又要考虑对废食用油脱水质量的要求。水力旋流器的净化处理主要在是固体悬浮物的分离和澄清的液体阶段。下图 1 所示的设计好的液液分离水利旋流器。在水力旋流器的顶部的以一定速度沿切向注入流体将由于旋流器的结构受到离心力作用使得粒子加速朝向墙壁。由于流体通过通过以螺旋形的旋液分离器，密度比较大或是质量比较大的颗粒将会向着壁面附近一栋并逐渐向地步流出口移动最后排出旋流器和相反密度小和质量比较小的颗粒像旋流器的中心核靠拢向入口处流去并逐渐从溢出口排出，从而实现轻重分离。分流和压降比水力旋流器的流量分离量定义的下溢的体积流量的比率其中 R 是分流量，Qu 和 Qi 是独立的体积流量和溢出量。在正常的操作条件下，有两种截然不同的的压降。水力旋流分离器和其中 P 和，PU 压力分别在混合液中的溢出量和下溢量。两个压力降之间的关系也是很重要的，并且可用于控制的目的。压降比雷诺数水力旋流器特性雷诺数可以描述如下： 其中 D 是水力旋流器直径; 和 是液体的密度和粘度， 是水力旋流速度。欧拉数水力旋流器溢流特性的欧拉数可以描述如下脱水效率水力旋流器的分离能力取决于能力处理的材料数量报告到超大的出油管流体和大小分布的杂质。尽管公称直径是最重要的参数，但是流入量、流出量和溢出量也是影响选了六七分离能力很重要的量。用来计算旋流器脱水效率比较经典的公式是转换到 和是 溢出和流入点的量的体积。0gi二、实验过程实验器材表 1 示出的废食用油的属性。水力旋流器几何尺寸旋流室的水力旋流器的直径 D 为 35 毫米，锥角为 10 度，水力旋流器的尺寸示于表 2。水力旋流器矩形 twosymmetrical 的入口（5mm10 毫米的） 。流程图图 2 为废食用油连续从水力旋流器的顶部流进，通过旋流器把油液净化后，废水和污染物从水力旋流器的底部排出废水处理设施并流入到下一个装置这一过程的示意图。通过测量流入油液、流出口和溢出口的浓度来测量净化的效率。图（2）图中粗 desaltingdevice 常减压蒸馏装置在常压和正空条件下油液脱水单元三、实验数据结果分析压降比和雷诺系数之间的关系，它们之间的变化关系如下图3，当流量 R 值相同时，压降比会随着雷诺系数的增大而下降。 当雷诺数大于 6000 年,随着雷诺数的增加,压降比的下降时比较平缓的。这说明,这两个压力下降率接近流量的增加率。欧拉系数与雷诺系，它们之间的变化关系如图 4，由图可以看出欧拉系数随雷诺系数的增大而增大，这表明,增加流量增加价值的pio。分离性能 雷诺数对脱水效率的影响，雷诺系数是一个对脱水效率影响比较关键的可控制变量，图 5 反映的是雷诺系数和脱水率之间的关系。当雷诺系数小于 5400 是，脱水量随雷诺系数的增大而增大，当靠近5400 时脱水量达到最大，超过 5400 时，脱水量随雷诺系数的增大反而降低。图4 欧拉数和雷诺数。图5 雷诺数和脱水效率。1.当流率非常高的时候，会发生强烈的乳化作用。这是由于剪切力作用引起液体粒子变小，当发生乳化作用时，水力旋流器的的作用就是从一种密度小的均匀混合物中分离出来密度较大的乳化物质。2.要建立涡旋运动和离心分离势力，必须建立一个最小的流量生长强度随着流量的增加和分离效率的提高而变化。欧拉数在脱水效率中的作用。图6 显示了欧拉数和脱水效率之间的关系。通常, 分离效率随着欧拉数的增加而提高提高，达到最大时的欧拉数是1800。再增加欧拉数将导致分离效率急剧下降。从表 3 的脱水结果中可以看出，,当流量在 2.7 到 3.0 立方米/小时变化时，脱水效率从 80%到 94%范围内变动。水的浓度可以降低到 0.100.30 %每升。 图 6 欧拉系数与脱水率废食用油脱水结果总结在本文中,介绍了一种使用水利旋流器对废食用油进行脱水净化的新技术阶段，已经做了初步的工业试验且验证了该新技术的可行性，并且发现雷诺系数对脱水率有很明显的影响。在雷诺系数小于5400 的范围内，脱水率会随着雷诺系数的增大而提高，在雷诺系数为 5400 的时候脱水率达到最大值，此外继续增大雷诺系数，脱水率反而会降低。当入口时油液的雷诺数为 5000 5800 时，脱水可以使得油液中的含水量降低到 0.5 -3.0 0.30%，这些充分证明水力旋流器可以成功的脱去混在油液中的水。原文下一页开始：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.Preliminaryindustrialexperimentshave beencarriedout toprovethefeasibilityofdehydration 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,andCOturningtoairpollutantsareproduced,anditisreportedthatdeadlypoisonous 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,foodplantsandhomesisactuallydischargedintoriversandlakesand 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 C211 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.Unlikeothercentrifugalmachines,hydrocyclones havenomoving parts.Thesepara-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 onboth the nature ofthe separation and the quality ofeffluentdesired. 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-liquidseparation. Thefluid is injected tangentiallyat thetopofthe 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 HYDROCYCLONES 185Downloaded by Xian Jiaotong University at 00:54 13 March 2013 C1pio piC0 po(2)andC1piu piC0 pu(3)where pi, po, puare the pressure in the feed, overflow, and underflow, respectively.Therelationshipbetweenthetwopressuredropsisalsoimportantandcanbeusedforcontrol purposes. The pressure drop ratio PR C1pio=C1piu.Reynolds NumberThe hydrocyclone characteristic Reynolds number could be described as follows:Re C26DvC22(4)whereDisthehydrocyclonediameter;C26andC22arethedensityandviscosityofliquid,respectively; and v is the hydrocyclone characteristic velocity4QiC25D2.Euler numberThehydrocycloneoverflowcharacteristicEulernumbercouldbedescribedasfollows:Eu piC0 poC26v2=2(5)UnderflowOverflowFeedInner SpiralOuter SpiralFigure 1 Fluid flow in hydrocyclone.186 BAI, WANG, AND TUDownloaded by Xian Jiaotong University at 00:54 13 March 2013 Dehydration EfficiencyTheseparationcapabilityofahydrocycloneisstronglydeterminedbythecapacityofhandling 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 C0gogi 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 was10C14.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.Material Density/KgC1m-3Viscosity/mm2C1s-1Water concentration /%Waste edible oil 875 (25C14C) 6.21 0.53.0Table 2 Geometry of hydrocyclone.Do/D Du/D Ls/D L/D Lu/D0.429 0.286 0.286 10.88 8.56Note: 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 HYDROCYCLONES 187Downloaded by Xian Jiaotong University at 00:54 13 March 2013 RESULTS AND DISCUSSIONPressure CharacteristicsPressuredropratiovs.Reynoldsnumber. The relationship between pressuredropratioandReynoldsnumberisshowninFigure3.ForthesameflowsplitR,anincreasein 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 ofC1pio.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.Furtherincreasesinthe Reynoldsnumberwill cause performance deterioration. This occurs for thefollowing reasons:Edible oilDehydration edible oilOily wastewaterHydrocycloneFigure 2 Diagram of crude desaltingdevice in atmospheric and vacuum distillation unit.3000 4000 5000 6000 7000 80001.021.031.041.051.061.071.081.09PRReR=1%R=3%Figure 3 Pressure drop ratio vs. Reynolds number.188 BAI, 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 4000 4500 5000 5500 6000 6500 700080010001200140016001800200022002400EuReFigure 4 Euler number vs Reynolds number.4000 4400 4800 5200 5600 6000 64007880828486889092E/%ReFigure 5 Reynolds number vs. dehydration efficiency.DEHYDRATION OF WASTE EDIBLE OIL BY HYDROCYCLONES 189Downloaded 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 thedehydrationefficiencyofthehydrocyclone.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.
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