Demulsification of Water-in-Oil Emulsions by Microwave Heating Technology

Transcription

1 Wold Academy of Science, Engineeing and Technology Intenational Jounal of Chemical and Molecula Engineeing Demulsification of Wate-in-Oil Emulsions by Micowave Heating Technology Abduahman H. Nou, Rosli M. Yunus, and Azhay. H. Nou Intenational Science Index, Chemical and Molecula Engineeing waset.og/publication/3899 Abstact The mechanism of micowave heating is essentially that of dielectic heating. Afte exposing the emulsion to the micowave Electomagnetic (EM) field, molecula otation and ionic conduction due to the penetation of (EM) into the emulsion ae esponsible fo the intenal heating. To detemine the capability of micowave technology in demulsification of cude oil emulsions, micowave demulsification method was applied in a % and 0-80 % wate-in-oil emulsions with micowave exposue time vaied fom sec. Tansient tempeatue pofiles of wate-in-oil emulsions inside a cylindical containe wee measued. The tempeatue ise at a given location was almost hoizontal (linea). The aveage ates of tempeatue incease of % and 0-80 % wate-in-oil emulsions ae and o C/sec, espectively. The ate of tempeatue incease of emulsions deceased at highe tempeatue due to deceasing dielectic loss of wate. These esults indicate that micowave demulsification of wate-in-oil emulsions does not equie chemical additions. Micowave has the potential to be used as an altenative way in the demulsification pocess. Keywods Demulsification, tempeatue pofile, emulsion. Micowave heating, dielectic, volume ate. I. INTRODUCTION LECTROMAGNETIC adiation in the fequency ange E 300 MHz-300 GHz ae known as micowaves, micowave enegy is a non-ionizing adiation that causes molecula motion by migation of ions and dipole otations, but does not cause changes in molecula stuctue and wavelengths anging fom a few cm to a few mm []. In the oil field, the two basic types of emulsions ae wate-in-oil () and oil-in-wate (o/w). Moe than 95 % of the cude oil emulsion fomed in the oil field ae of the type [1]. The concept of micowave heating of emulsions was fist suggested by [5] and [14]. In the past 0 yeas, Micowave () enegy has been widely applied in food and chemical pocessing fo heating, thawing (melting), sinteing of ceamics and many othes [3] and [4]. Faste cooking times and enegy savings ove conventional cooking methods ae the pimay benefits. Vaious oil-inwate (o/w) and wate-in-oil () emulsions occu in industial opeations, such as petoleum efining, oil and gas poduction [4] and food pocessing industies. Efficient heating of emulsions is equied fo a faste pocessing based on industial demand. Micowave heating, because of its volumetic heating effects, offes a faste pocessing ate. Authos ae with Faculty of Chemical and Natual Resouces Engineeing, Univesity Malaysia, Pahang-UMP, Malaysia ( nou000_99@yahoo.com). In conventional themal pocessing, enegy is tansfeed to the mateial though convection, conduction and adiation of heat fom the sufaces of the mateial. In contast, micowave enegy is deliveed diectly to mateials though molecula inteaction with the electomagnetic field. In heat tansfe, enegy is tansfeed due to themal gadients, but micowave heating is the tansfe of electomagnetic enegy to themal enegy and is enegy convesion, athe than heat tansfe [13]. This diffeence in the way enegy is deliveed can esult in many potential advantages to using micowaves fo pocessing of mateials. Because micowaves can penetate mateials and deposit enegy, heat can be geneated thoughout the volume of the mateial. The tansfe of enegy does not ely on diffusion of heat fom the sufaces and it is possible to achieve apid and unifom heating of thick mateials. In ecent liteatue, many eseaches epot non-themal phenomena that have been boadly temed micowave effects. Examples fo micowave effect include enhanced eaction ates of themosetting esins duing micowave cuing [10] and faste densification ates in ceamics sinteing [11]. As mateials ae pocessed, they often undego physical and stuctual tansfomations that affect the dielectic popeties. Thus, the ability of micowaves to geneate heat vaies duing the pocess. Shap tansfomations in the ability of micowaves to geneate heat can cause difficulties with pocess modeling and contol. Undestanding the geneation, popagation and inteaction of micowaves with mateials is citical. Because the pocessing equipment detemines the electomagnetic field, the design of micowave equipment is paticulaly impotant. The popeties of the electomagnetic field, chemical composition of the mateial being pocessed, stuctual changes that occu duing pocessing, size and shape of the object being heated and the physics of the micowave/mateials inteactions all complicate micowave pocessing. II. MATERIAL AND METHODS In this study, Elba domestic micowave oven model: EMO 808SS, its ated powe output is 900 watts and its opeation fequency is 450 MHz was used in heating wate-in-oil emulsion samples. A 900 ml gaduated cylindical glass was used as sample containe. The diamete and height of emulsion sample in the containe wee 11.5 and 11 cm espectively. Thee themocouples type (K-IEC-584-3) wee connected to Pico-TC-08 data logging and then connected to micowave oven as shown in Fig. 1. The data logge was connected to PC; with PicoLog R softwae. The themocouples wee inseted to diffeent locations top, middle and bottom of the emulsion sample to measue local tempeatues. Intenational Scholaly and Scientific Reseach & Innovation 4() schola.waset.og/ /3899

2 Wold Academy of Science, Engineeing and Technology Intenational Jounal of Chemical and Molecula Engineeing Intenational Science Index, Chemical and Molecula Engineeing waset.og/publication/3899 A. Sample Pepaation and Pocedues The cude oil samples wee obtained fom Petonas efiney at Malaka city, two types of cude oil wee collected namely, heavy oil and light cude oil and 0-80% wate-in-oil emulsions wee pepaed using the same volumes of oil and wate. Emulsions wee pepaed in 900 ml gaduated beakes, with anges by volume of the wate and oil phase. Fig. 1 Elba micowave oven The micowave adiation was set to its highest powe setting. The wate phase is tab wate. The emulsions wee agitated vigoously using a standad thee blade popelle at speed of 1600 pm and tempeatue 8 C fo 7 min. The concentations of wate in samples wee 0-50% by volume. The containe of emulsion sample was placed in the cente of Elba domestic micowave oven model: EMO 808SS. Thee themocouples wee inseted in the emulsion sample at diffeent locations, top, middle and bottom. The emulsion samples wee heated with micowave adiation fo 0, 40, 60, 80, 100, 10, 140, 160, 180 and 00 sec. Tempeatue pofiles of emulsions inside a cylindical containe duing batch micowave heating at 450 MHz wee ecoded by Pico-TC- 08 data logging. The sufactant used in this study was the commecially available Titon X-100: This Titon X-100 is a non-ionic wate soluble molecule. The emulsifying agent was used as manufactued without futhe dilution. In ode to pepae wate-in-oil emulsions, the agent-in-oil method was followed; that is, in this study, the emulsifying agent (Titon X-100) was dissolved in the continuous phase (oil), then wate was added gadually to the mixtue. The volume of wate settled to the bottom was ead fom the scale on the beake with diffeent times. The amount of wate sepaation in pecent was calculated as sepaation efficiency (e) fom volume of wate obseved in the beake as follows: Pecentage of wate sepaation, e (Vol. of wate laye, ml) = 100 (Oiginal amount of wate, ml) The pepaed emulsion was used to check fo o o/w emulsions. All emulsions investigated wee wate-in-oil () emulsion (oil-continuous). B. Micowave Radiation A numbe of studies wee caied out on Micowave heating () of oil and wate systems. Micowave heating because of its volumetic heating effects, offes a faste pocessing ate. The sepaation of emulsified wate fom cude oil has seveal stages, due to gavity settling, wate doplet/doplet (1) flocculation takes place as wate doplets appoach each othe []. The pupose of heating wate-in-oil emulsions with micowave adiation is to sepaate wate fom oil. When wate-in-oil emulsion is heated with micowave adiation, two phenomena will occu; the fist one is the incease of tempeatue, which causes eduction of viscosity and coalescence. The esult is sepaation of wate without addition of chemicals [6]. Accoding to Stoke s law, if oil is the continuous phase, the settling velocity of wate doplets is given by: ( ρw ρo)gd ν w = () 18μo whee, D is the diamete of the doplets. The viscosity of oil vey sensitive to tempeatue, as tempeatue inceases, viscosity deceases much faste than the density diffeence, (ρ w -ρ o ) does, the esult when viscosity deceases, the doplets size inceases. Theefoe, micowave heating inceases the velocity of wate (v w ) and acceleates the sepaation of emulsion. The second phenomenon is coagulation. The highe tempeatue and lowe viscosity make the coagulation pocess easie. The esults ae lage paticle diamete D and apid sepaation. C. Micowave Powe Geneation Using micowaves as a souce of heat in the pocessing (heating, melting, dying and thawing) of mateials is one of the advantageous because it esults in faste, moe unifom heating than conventional heating does. This study, focus on geneation of micowaves in the oven, tempeatue distibution, micowave powe absoption as well as sepaation of emulsified wate fom cude oil. The vaiables affecting micowave powe absoption by an element ae dielectic constant and dielectic loss, location and micowave powe incident at the load. Fo a sample in cylinde containe, the local micowave powe flux calculated as: ln(m) P = 0 (3) A Whee: m = Mass (g) of the sample A = Sample s containe aea The micowave powe absoption density at any location within the sample is one of the inteesting tems, in this egads, the electic field attenuates (decay) exponentially in x and y diections within the sample due to dissipation as heat and can be expessed as: P z = P 0 e αz (4) whee, P z is micowave powe tansmitted. The attenuation facto can be calculated fom the electomagnetic field theoy given by [15] as: ( ) 1/ 1 tan 1 ' πf ε α E = + δ c (5) Intenational Scholaly and Scientific Reseach & Innovation 4() schola.waset.og/ /3899

3 Wold Academy of Science, Engineeing and Technology Intenational Jounal of Chemical and Molecula Engineeing Intenational Science Index, Chemical and Molecula Engineeing waset.og/publication/3899 The above Eq. 5 will be used fo calculation of volume ate of heat geneation by micowave adiation: q α E z = Pz (6) If the dielectic popeties ae assumed to be independent of tempeatue at fequency 450 MHz, the wavelength λ m and penetation depth D P within a sample fo a adiation of the above fequency (450 MHz) ae elated to dielectic constant ε and dielectic loss ε as follows: and '' ' ε ε ' c ε λ m = f '' ' ε ε ' c ε D p = πf Since micowave heats mateials volumetically, it is possible to calculate the volume ate of micowave heat geneation fom enegy balance equation as: 1/ 1/ 4 ( T m ) 4 -( T ) ha εaσ dt g = ( Tm -T a ) + +ρc p V V dt a The above Eq. 9 assumes that the ate of heat tansfe fom emulsified wate doplets to the continuous phase (oil) is vey apid; theefoe, wate and oil pactically have the same tempeatue. The ight hand side of Eq. 9 compises of thee tems, convective heat tansfe, adiative heat due to micowave and conductive heat in the sample espectively. Fom esults of this study, the effect of adiative tem is vey small as well as convective tem. Since the sample containe (glass) has low dielectic constant, theefoe, its heat geneated assumed to be negligible. Fo calculation of volume ate of heat geneation in Eq. 9, the density (ρ) and (C p ) of the emulsions calculated fom mixing ules as: ρ m =ρ (1 ) wϕ+ρo ϕ (10) (7) (8) (9) Cpm = Cp,wϕ+ C p,o(1 ϕ ) (11) The volume ate of micowave heat geneation of the wate and cude oil calculated fom tempeatue measuements and Eq. 9 ae shown in Table I while heat geneation values fo emulsion samples shown in Table II. Table I and II shows the aw expeimental esults of micowave heating, while Table III and IV shown the calculated values of volume ates of heat geneation. III. RESULTS AND DISCUSSION The micowave heating pocess was examined fo wate, oil and emulsion samples. Tansient tempeatue pofiles of wate-in-oil emulsions inside a cylindical containe duing batch micowave heating wee measued. Thee tempeatue eadings wee placed at the top, middle and bottom of the sample containe. Figs. and 3 shows tansient tempeatue distibution of and 0-80% wate-in-oil emulsions espectively, fo micowave iadiation time vaies fom 0, 40, 60, 80, 100, 10, 140, 160 and 180 sec. Fom the both Fig. and 3 the tempeatue ise at a given location was almost linea (hoizontal). This indicated that wate-in-oil emulsions wee heated unifomly by micowaves; this was expected esult since the dielectic loss of oil is small. The tempeatue inceasing ates of iadiated samples and thei volume ates of heat geneation wee shown in Table I and espectively. These samples compise wate, cude oil, and 0-80% wate-in-oil emulsions. The tempeatues of emulsions wee obtained fom the aveage values of thee location tempeatue eadings. The ate of tempeatue incease was calculated fom tempeatue incease divided by adiation time. The aveage ates of tempeatue incease of and 0-80% wate-in-oil emulsions ae and C sec 1, espectively. It obseved that, the ates of tempeatue wee deceases at tempeatue inceases: This was the expected esults since the dielectic loss of wate is small. The enegy balance Eq. 9 used to calculate the volume ate of heat geneation: This Eq. 9 included thee tems, convective heat tansfe, iadiative heat tansfe due to micowave and conduction heat tansfe espectively. Fom calculations of this study, the contibutions of convective and iadiation tems ae vey small. Since the sample containe is a glass cylinde (tanspaent to micowave and has vey low dielectic constant), its heat loss assumed to be zeo. The volume ates of micowave heat geneation of wate and cude oil calculated fom the tempeatue measuements and Eq. 9 ae shown in Table I, while fo and 0-80% wate-in-oil emulsions ae shown in Table II. Intenational Scholaly and Scientific Reseach & Innovation 4() schola.waset.og/ /3899

4 Wold Academy of Science, Engineeing and Technology Intenational Jounal of Chemical and Molecula Engineeing Intenational Science Index, Chemical and Molecula Engineeing waset.og/publication/3899 TABLE I EXPERIMENTAL RESULTS OF MICROWAVE HEATING (WATER AND CRUDE OIL) Radiation Rate of Volume ate of time sec incease T, C Inc ease,dt/dt, heat geneation t o=5.6c C/s q,cal/s.c Wate Oil m TABLE II EXPERIMENTAL RESULTS OF MICROWAVE HEATING FOR EMULSIONS Radiation time Incease Rate of Volume ate of heat T, C Incease, geneation q, t, sec t o =5.6C dt/dt, C/s cal/s.cm % % Fig. Tempeatue distibutions of 50-50% emulsions Fig. 3 Tempeatue distibutions of 0-80% emulsions Intenational Scholaly and Scientific Reseach & Innovation 4() schola.waset.og/ /3899

5 Wold Academy of Science, Engineeing and Technology Intenational Jounal of Chemical and Molecula Engineeing Intenational Science Index, Chemical and Molecula Engineeing waset.og/publication/3899 TABLE III VOLUME RATES OF HEAT GENERATION OF WATER AND CRUDE OIL BY MICROWAVE RADIATION Radiatio n Time t, sec inceas e T,C t o =5.6 C Rate of Incea se dt/dt, C/s Vol.Rate of heat geneation q,cal/s.cm 3 Expeimental Calculated Values Values Wate Oil Fig. 4 Sepaation of wate fom 50-50% emulsions In application of Eq. 9 fo detemination of volume ates of heat geneation, the emulsion density (ρ m ) and heat capacity (C p,m ) calculated fom Eq. 10 and 11 espectively. The calculated volume ates of heat geneation of wate and oil fom Eq. 3 though Eq. 11 wee shown in Table III. While fo emulsions illustated in Table IV. It obseved that, fo wate and emulsions, the expeimental esults geate than the calculated, while fo oil the evese, the calculated esults geate than the expeimental, this attibuted due to shotage of oil popeties and used liteatue values. Since the pupose of heating wate-in-oil emulsions with micowave is to sepaate wate fom oil [1], theefoe, the sepaation efficiency of and 0-80% wate-in-oil emulsions calculated by using Eq. 1 wee shown in Figs. 4 and 5 espectively. The same tend was epoted by [8], [9] and [7]. All expeimental esults showed that micowave adiation is vey effective in sepaation of wate-in-oil emulsions. TABLE IV VOLUME RATES OF HEAT GENERATION OF EMULSIONS BY MICROWAVE RADIATION Radiatio n Time t, sec 50-50% 0 Temp. incea se T,C t o =5. 6C Rate of Incease dt/dt, C/s Vol. Rate of heat geneation q, cal/s.cm 3 Expeimental calculated % Fig. 5 Sepaation of wate fom 0-80% emulsions Intenational Scholaly and Scientific Reseach & Innovation 4() schola.waset.og/ /3899

6 Wold Academy of Science, Engineeing and Technology Intenational Jounal of Chemical and Molecula Engineeing The wavelength (λ m ) and penetation depth (D p ) wee found 1.39 and 3.47 cm espectively. Fig. 8 shows the heating ate of tempeatue incease fo wate, oil and emulsions vesus the adiation time. Intenational Science Index, Chemical and Molecula Engineeing waset.og/publication/3899 Fig. 6 Rates of tempeatue incease fo wate and oil Fig. 7 Rates of tempeatue incease fo wate and oil Fig. 8 Rates of tempeatue incease fo and 0-80% Fig. 9 Heating ate vs. adiation time fo wate, oil and emulsions Figs. 4 and 5 showed that, micowave adiation can aise the tempeatue of emulsion, educe the viscosity and acceleate sepaation pocess as suggested by Eq.. The ates of tempeatue incease wee decease at highe tempeatues, Fig. 6 shows the phenomenon fo wate and oil, while Fig. 7 shown the same phenomenon fo and 0-80% wate-inoil emulsions espectively. IV. CONCLUSION The micowave heating pocess was examined fo wate, oil and emulsion samples. Results of this study showed that, micowave adiation is a dielectic heating technique with the unique chaacteistics of fast, volumetic and effective heating is feasible and has the potential to be used an altenative way in the demulsification of wate-in-oil emulsions. Fom tempeatue distibution pofiles of iadiated emulsion, it appeas wate-in-oil emulsion has been heated quickly and unifomly by micowaves athe than by conventional heating. This new sepaation technology does not equie chemical addition. Futhemoe, micowave adiation appeas to povide faste sepaation than the conventional heating methods. REFERENCES [1] Ali, M.F. and M.H. Alqam, 000. The ole of asphaltenes, esins and othe solids in the stabilization of Wate-in-Oil Emulsions and its effects on oil poduction in Saudi oil fields. Fuel,79: DOI: /S (99) [] Ayappa, K.G.; Chattejee,A and Basak, T. (1998). Analysis of Micowave Sinteing of Ceamics. AIChEJ. [3] Ayappa, K.G.; Davis, H.T.; Davis, E.A.; and Godon, J. (199). Two Dimensional Finite Element Analysis of Micowave Heating. AIChEJ. [4] Kim, Y.H. et al., Demulsification of wate-in-cude oil emulsions. Effects of film tension, elasticity, diffusivity and intefacial activity of demulsifie individual components and thei blends. Dispes. Sci. Technol., 17: [5] Klaila, W.J Method and appaatus fo contolling fluency of high viscosity hydocabon fluids. U.S. Patent 4, [6] Fang, C.S., B.K.L. Chang, P.M.C. Lai and W.J. Klaila, Micowave demulsification. Chem. Eng. Commun.,73:7-39. [7] Fang, C.S. and P.M.C. Lai, Micowave heating and sepaation of wate-in-oil emulsions. J. Micowave Powe Electomagnet. Eneg., 30: [8] Fang, C.S.; Lai, P.M.C.; Chang, B.K.L.; Klaila, W.J Oil ecovey and waste eduction by micowave adiation. Envion.Pog [9] Chan, C.C. and C.C. Yeong, 00. Demulsification of wate-in-oil emulsions by micowave adiation. Sep.Sci.Technol.,37: [10] Maand, E.; Bake, HR.; and Gaybeal, JD. (199). Compaison of eaction mechanisms of epoxy esins undegoing themal and micowave cue fom insitu measuements of micowave dielectic popeties and infaed spectoscopy. Macomolecules. 5 :4-5. [11] Janney, MA.; and Kimey, HD. (1991). Diffusion-contolled pocesses in micowave fied oxide ceamics. In : Snyde J. WB, Sutton WH, Iskande MF, Johnson DL Editos. Micowave pocessing of mateials II, Mateials eseach society poceedings, 189. pp.15-7 [1] Tanmay, B. and K.G. Ayappa, Analysis of micowave thawing of slabs with effective heat capacity method. J. Am. Inst. Chem. Eng., 43: [13] Thostenson, E.T.; and Chou, T.W. (1999). M icowave pocessing: Fundamentals and Applications. Composite, pat A.30, [14] Wolf, N.O., Use of micowave adiation in sepaating emulsions and dispesions of hydocabons and wate. US Patent, [15] Hippel, A.R Dielectic Mateials and Applications. MIT Pess. Cambidge. MA. Intenational Scholaly and Scientific Reseach & Innovation 4() schola.waset.og/ /3899