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Ultrafiltration of Dairy Products As Ache Laboratory Experiment .t311111ij111111§._1a_b_o_r._a_t_o_r.:.y________ ) ULTRAFILTRATION OF DAIRY PRODUCTS AS ACHE LABORATORY EXPERIMENT THOMAS D. CONLEE,1 HELEN C.HOLLEIN, CHARLES H. GOODING,2 C. STEWART 8LATER3 Manhattan College • Riverdale, NY 10471-4099 embrane process experiments involving ultrafil­ nology in the chemical engineering curriculum has been 81 tration (UF) of dairy products have been devel­ addressed in recent articlesY- M oped and classroom tested. These experiments Membrane processes are mass transfer unit operations provide an effective method for integrating membrane sepa­ used for liquid- or gas-stream separations. The family of ration processes into the curriculum while at the same time processes covers a number of operations, including reverse offering learning experiences of broad-based interest to osmosis (RO), nanofiltration, ultrafiltration, microfiltration chemical engineering students through familiar applica­ (MF), dialysis, electrodialysis, gas permeation (GP), and tions such as cheese production and environmental pervaporation (PV)_l9l These processes are not really new, cleanup. UF experiments can be used in conjunction with but are often unfamiliar to the typical chemical engineer due the required unit operations laboratory and mass transfer/ to lack of exposure during his or her education. separation processes courses, or as a component of elec­ RO is in its fourth decade, having been developed in the tive courses in membrane process technology or bio­ early 1960s for industrial operations such as production of chemical engineering. potable water from seawater. UF has been used on a com- Although there has been considerable discussion about revamping the chemical engineering curriculum, topics cov­ Thomas D. Conlee is currently employed as an environmental engineer at Tosco Refining Company, where he is working on ground water compli­ ered in required courses remain fairly uniform throughout ance. His job entails assuring that the refinery is in compliance with local academe. Required separations or mass transfer courses fo­ ground water regulations. He earned his BS degree in chemical engineer­ cus heavily on traditional equilibrium-staged operations, in­ ing from Manhattan College and completed a senior honors project on membrane process technology. 1 cluding distillation, absorption, and extraction.[1 These unit Helen C. Hollein is Professor and Chair of the Chemical Engineering operations are very important in the chemical and petroleum Department, and Director of the Biotechnology Program, at Manhattan College. She earned her MS and DEngSc degrees from the New Jersey industries, but chemical engineering students also need to Institute of Technology and her BSChE from the University of South study separation processes that have become increasingly Carolina. Her research and teaching interests are in biochemical engi­ neering and bioseparations, and she is active in curriculum and laboratory important in other areas, such as food processing, biotech­ development. nology, and environmental engineering. A 1995 undergradu­ Charles H. Gooding is Professor and Chair of the Department of Chemi­ ate survey of chemical engineering programs indicates that cal Engineering at Clemson University. He earned his BS and MS de­ grees from Clemson University and his PhD from North Carolina State there has been little change in topics covered in mass trans­ University. His primary research interets are membrane separation pro­ fer courses other than slight increases in time spent on cesses, including nanofiltration, ultrafiltration, pervaporation, and gas sepa­ ration systems; mathematical analysis of membrane processes; and envi­ adsorption (2.5%) and membranes (2.6%) .tJJ The impor­ ronmental applications of membrane technology. tance of including instruction on membrane process tech- C. Stewart Slater is Professor and Chair of the Department of Chemical Engineering at Rowan University. He received his BS, MS, MPh, and PhD degrees from Rutgers University. His research and teaching interests are in separation and purification technology, laboratory development, and 1 Address: Tosco Refining Company, Linden, NJ 07036 2 investigating novel processes for interdisciplinary fields such as biotech­ Address: Clemson University, Clemson, SC 29634-0909 nology and environmental engineering. 3 Address: Rowan University, Glassboro, NJ 08028- 1701 © Copyright ChE Division of ASEE 1998 318 Chemical Engineering Education mercial scale since the early 197Os, with Rowan University. In addition, a hand-held dairy processing representing one of the larg­ RO system is used in the freshman engineer­ est applications of membrane technology in ... [Membrane ing course at Rowan University.r20·211 the world.[I OJ The earliest commercial appli­ process The authors have previously outlined UF cation of UF was the concentration of pro­ experiments experiments for separation and concentration teins from whey, a milk by-product gener­ involving of protein and enzyme mixtures, experiments ated during the traditional coagulation pro­ that are used to supplement an elective course cess for cheese production.[l oJ Similarly, UF ultrafiltration] 15 22 231 in biochemical engineering at MC. · • Other is used to remove lactose and milk pro­ can be used in professors have reported on UF experiments teins from whey wastewater streams prior conjunction for concentration and separation of polyeth­ to disposal, i.e., for environmental treat­ ylene glycol and of protein mixtures, adapted ment. In newer processes for manufacture with the to the unit operations laboratory and a bio­ of soft cheeses, yogurt, ice cream, and required unit technology laboratory, respectively.l24·251 other dairy products, UF is used to operations preconcentrate whole or skim milk prior SEPARATION PRINCIPLES to entering the production chain.r1o- i5J laboratory and Ultrafiltration is one of a group of mem­ This paper discusses laboratory experi­ mass transfer/ brane filtration processes that depends on pres­ ments on ultrafiltration of dairy products that separation sure as the driving force for separation. The may be used to increase coverage of mem­ processes average pore size in UF membranes varies brane processes in the chemical engineering from 300 to 300,000 Daltons (ranges vary curriculum and gives typical results from courses, or as a depending on source), which will retain mac­ experiments run by students at Clemson Uni­ component of romolecules such as milk proteins while pass­ versity (CU) and Manhattan College (MC). elective ing inorganic salts and small organic mol­ At CU, a spiral-wound UF system manu­ ecules such as lactose (C 12H220 11 ) through factured by Koch Membrane Systems, Inc., courses in the membrane. The key proteins in milk are has been used to concentrate various dairy membrane caseins, which form large micelles (10 to 300 products in the experimental component of process nm), a -lactalbumin and ~ -lactoglobulin. The an elective course on membrane separation a-lactalbumin has a molecular weight of processes and in the senior unit operations technology or 18,300, while ~-lactoglobulin exists as a laboratory. L6J The CU experiments focus on biochemical dimer with a molecular weight of 36,000; application of the UF process for environ­ engineering. therefore, a membrane with a molecular mental cleanup of rinse waters from dairy weight cutoff (MWCO) of 10,000 is needed operations, e.g., a whole-milk pasteurization to insure complete retention of milk pro­ system, an ice-cream freezing unit, and a teins. L101 A polysulfone membrane with a chocolate-milk production system.r16J At MC, a Millipore MWCO of 20,000 is generally used for milk ultrafiltration, Model TCFlO thin-channel UF system (formerly manufac­ with an elevated operating temperature (52°-54°) and trans­ 111 tured by Amicon) is used in the unit operations laboratory membrane pressures of 170-310 kPa. r The membrane origi­ 14 course for an experiment on milk concentration. nally used for this application was cellulose acetate .L J Based on the authors' . experiences, the milk experiments The molecular weight cutoff of a membrane may be de­ have an intrinsic appeal to all of the chemical engineering fined as the molecular weight that is 90% rejected by the students and instructors, not just the biochemical engineers membrane (some manufacturers use a different percent, e.g., and membrane specialists. Interest is heightened by employ­ 95% ), which indicates that a 10,000 MWCO membrane will ing a typical local application; for example, UF is one of the reject 90% of solutes having a MW more than 10,000. Re­ steps used in cheese production at Kraft Foods Inc. in jection is actually a function of the size, shape, and surface­ Tarrytown, New York (an industrial site near MC). binding characteristics of the hydrated molecule, as well as the pore-size distribution of the membrane; therefore, mo­ The UF experiments discussed in this paper are but one lecular weight cutoff values can be used only as a rough component of an array of membrane process experiments guide for membrane selection. that can be employed to enhance the chemical engineering curriculum. RO, GP, MF, and PV experiments are also in­ System performance is usually defined in terms of perme­ 19 cluded in the courses at CU and MC. <5·6·17- l Several mem­ ate flux, J, with dimensions of (volume/area-time), i.e., typi­ 2 brane process experiments will be integrated into the re­ cal units are (L/m -h). Flux can be determined by measuring quired mass transfer
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