MODELING OF THE PERMEATION PROCESS IN THE CROSS-FLOW ULTRAFILTRATION OF PROTEIN SOLUTION TUAN-ANH NGUYEN IN THE PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF DOCTOR OF ENGINEERING (CHEMICAL ENGINEERING) THE GRADUATE SCHOOL OF SCIENCE AND ENGINEERING TOKYO INSTITUTE OF TECHNOLOGY AUGUST 2013 ACKNOWLEDGEMENTS I would like to express my deep gratitude to my supervisor, Assoc. YOSHIKAWA Shiro, for giving me the opportunity to work in a modern technique of separation. The constant guidance and encouragement are also indispensable to me for completing my research. I wish to express my appreciation to Prof.
KURODA Chiaki, Prof. OHTAGUCHI Kazuhisa, Prof. ITO Akira, Prof. SEKIGUCHI Hidetoshi, Assoc.
OOKAWARA Shinichi for their time and effort in evaluating my work. I have benefited from their constructive comments on my report. I want to express my sincere appreciation to the Chemical Engineering Department of Tokyo Institute of Technology, Japan and to the Faculty of Chemical Engineering of Ho Chi Minh University of Technology, Vietnam: for all the best things that they have offered me during my study and research. I would also like to acknowledge JICA project for giving me the chance to improve my knowledge in the doctoral degree and the financial support.
I also would like to thank all my lab-mate and my friends in Japan; for sharing with me their ideas and experience. They are always available whenever I have trouble. Finally, I would like to dedicate my thesis to my family, with love and gratitude. TABLE OF CONTENTS TABLE OF CONTENTS.
i LIST OF TABLES. v LIST OF FIGURES. vi LIST OF NOTATIONS. viii Chapter 1 Introduction .1 Whey protein production and utilization .2 Concentrating Whey—Early Efforts .3 Concentrating Whey—Modern Techniques .2 Classical fouling model .5 Cross-flow versus dead-end configuration .6 Classical filtration model for cross-flow filtration .8 Objective of the study.
13 Chapter 2 Filtration laws and the applicability to cross-flow filtration of protein solution .2 Classical membrane fouling model .3 Compressible cake layer .3 Modification of filtration model to cross-flow operation system .1 Classical fouling model .3 Cross-flow UF apparatus .4 Cross-flow membrane module .5 Results and discussion .1 Complete blocking law .2 Intermediate blocking law .3 Cake filtration model .4 Compressible cake model. 37 Chapter 3 Combination model for permeate flux in cross-flow ultrafiltration of protein solution.1 Combine pore blockage and cake filtration .2 Combined pore blockage and compressible cake layer model in sequent.2 A new combined model which consider pore blockage and compressive cake layer simultaneously .2 Boundary and initial condition .4 Results and discussion .1 Pure water flux .2 Suspension permeation results .3 Comparison of the model with the experimental results .4 Effect of operating conditions. 59 Chapter 4 Estimation of steady state permeate flux in cross-flow ultrafiltration of protein solution.2 Correlation and dimensional analysis .3 Steady state estimation. Results and discussions.1 Comparison with experimental data .2 Effect of operating condition to removal rate or steady state permeate flux .3 Pore blockage coefficient α: .4 Calculation of the permeation process.
74 Chapter 5 Application in design and optimization problem .2 System configuration and model calculation .2 Modeling of module performance .4 Formulizations of the problem.5 Cyclic coordinate method for optimization .7 Results and discussion .1 Effect of recirculation flow rate on the total cost .2 Effect of module inlet pressure operation .3 Effect of module height .4 Effect of module width. 96 Chapter 6 Conclusions and recommendations. 100 iv LIST OF TABLES Table 1.1 Typical chemical composition (g/L) of sweet and acid whey [2] .2 Typical and species retained by MF, UF and RO membrane [7] .1 System parameter representing the ―baseline design configuration‖ .2 Optimum design of membrane module. 94 v LIST OF FIGURES Figure 1.1 Schematic of cheese making process and image of coagulation (http://uktv.uk/food/item/aid/640812 access on 2013/06/03) .2 Liquid whey processing [1] .3 Dead-end mode and cross-flow mode of filtration [25] .1 Fouling mechanisms of porous membrane [18] .2 Relation between volume fraction and yield shear stress [12] .3 Schematic diagram of experimental apparatus .4 Cross sectional drawing of the flat membrane module .5 Fitting results using complete blockage model .6 Fitting results using intermediate blockage model .7 Fitting results using cake filtration model .8 Fitting results using compressible cake filtration model .9 Magnification in the initial period of filtration process .10 Magnification at the initial period using conventional cake layer model .1 Schematic of the developing blockage region .2 Schematic diagram of permeation process .4 Effect of trans-membrane pressure to pure water permeate flux .6 Experimental results at the initial period.7 Comparison between calculation and experiment .8 Magnification at the very initial period .9 Effect of ΔP to fitting parameters .10 Effect of feed flow rate to fitting parameters .1 Comparison between model calculation and experimental data .2 Relation between mass Stanton number and dimensionless group .3 Steady state permeate flux versus cross-flow velocity.4 Relation between protein blocked fraction and dimensionless group .5 Comparison between predicted and calculate pore blockage parameter α .6 Comparison between calculations based on correlation equation and experimental results .1 Schematic of membrane system operational configuration .2 Time value of money and cash flow [8] .3 An illustration of the cyclic coordinate method .4 Effect of recirculation flow rate on the total cost of plant .5 Effect of inlet pressure on the total cost of plant.6 Effect of module height on the total cost of plant .7 Effect of module width on the total cost of plant .8 Behavior of cost per unit flow rate design in optimum condition with plant capacity.
94 vii LIST OF NOTATIONS Terms ANOVA: analysis of variance df: degree of freedom DF: diafiltration ED: electrodialysis MF: microfiltration MS: mean square MWCO: molecular weight cut off NF: nanofiltration RO: reverse osmosis SS: sum square UF: ultrafiltration WPC: whey protein concentrate Nomenclatures A: membrane area (m2) a: fractional area over total area membrane (m2/m2) b: channel height C: protein concentration (g/m3) ϕ=C/ρ D: diffusion coefficient d: diameter f’R’ : growing cake factor (m/kg) J: filtrated flux per unit membrane (m/s) L: channel length P: pressure (Pa) Q: volume metric flow rate (m3/s) R: resistance, (m-1) t: filtration time (s) u: velocity (m/s) V: accumulated filtrate volume per unit membrane (m3/m2) Greek’s letters α: pore blockage parameter (m2/kg) ΔP: trans-membrane pressure (kPa) : shear rate (s-1) η: solution viscosity (kg/m.s) ρ: specific mass of protein (g/m3) υ: removal rate ϕ: volume fraction (m3/m3) Subscript open: open or clean area b: bulk, back block: blocked area viii m: membrane f: fluid phase h: hydraulic properties p: protein particle s: solid phase or protein S: shear induced ss: steady state t: top of the cake layer y: compressive yield stress 0: initial ∞: infinite ix Chapter 1 Introduction 1.1 Whey protein production and utilization Whey is the liquid resulting from the coagulation of milk and is generated from cheese manufacture [1].1 shows the simplified schematic diagram of cheese making process and the image of cheese curding. Sweet whey, with a pH of at least 5.6, originates from rennet- coagulated cheese production such as Cheddar. Acid whey, with a pH no higher than 5.1, comes from the manufacture of acid-coagulated cheeses such as cottage cheese. While both whey types contain approximately the same amounts of whey proteins and lactose, the main difference is found in the calcium and lactic acid contents.
Compositional ranges of each are shown in Table 1. Milk Pasteurization Cultural, Additive Coagulant Curding Draining Cheese Whey Figure 1.1 Schematic of cheese making process and image of coagulation (http://uktv.uk/food/item/aid/640812 access on 2013/06/03) 1 In general, about 9 liters of whey is generated for every kilogram of cheese manufactured, and a large cheese making plant can generate over 1 million liters of whey daily ([2]). Due to the large amount and its low concentration, whey has been viewed until recently as one of the major disposal problems of the dairy industry. Whey not used for humans was fed to pigs or other livestock, spread to the field as fertilizer, or simply thrown out.
However, whey is a potent pollutant with a high biological oxygen demand (BOD) of 35-45 kg/l; 4,000 l of whey, the output of a small creamery, has the polluting strength of the sewage of 1,900 people [3]. Therefore, whey constitutes a major ecological burden as well as severe odor problem if disposed as a waste material or spraying onto field. The high BOD of whey also leads to an over load of waste treatment facilities and make this approach seldom practiced.1 Typical chemical composition (g/L) of sweet and acid whey [2] Beside the environmental effect, nowadays whey is evolving into a sought-after product because of the lactose, minerals, and proteins it contains as well as the functional properties it imparts to food. A number of products are obtained from whey processing, as shown in Figure 1.2 Liquid whey processing [1] 1.2 Concentrating Whey—Early Efforts The health benefits of whey led to the development of processes to isolate the solids by concentration and drying.
The initial industrial attempts were based on heat process: concentration and drying. The multiple-effect evaporator, which boils water in a sequence of tanks with successively lower pressures, is the conventional method for whey concentration. Since the boiling point of water decreases as pressure decreases, the vapor boiled off in one vessel is used to heat the next and an external heat source is needed for the first vessel only and thus this method can reduce the high energy cost for concentration. However, concentrated whey is a supersaturated lactose solution and, under certain conditions of temperature and concentration, the lactose can sometimes crystallize before the whey leaves the evaporator.
At concentrations above a dry material content of 65%, the product can become so viscous that it no longer flows. Roller drying is a process in which whey is dried on the surface of a hot drum and removed by a scraper. Although it is the cheapest drying technique, it may cause undesirable heat damage 3 for most functional applications of whey products. In addition, it is difficult to remove the dried whey from the drum surface and filler such as wheat need to be mixed before drying.
Spray drying is the most common technique for drying whey. In this process, the lactose, which is amorphous and hygroscopic, is cooled and crystallized to nonhygroscopic α-lactose monohydrate. The concentrated whey is then dispersed by a rotary wheel or nozzle atomizer into a drying chamber through a hot-air stream, producing a powder with 10–14% moisture. The evaporation keeps the temperature down and preventing denaturation [4].
The wet powder is dried to 3–5% moisture in a vibrating fluid bed [5].3 Concentrating Whey—Modern Techniques Until the 1970s whey protein was available only in the heat-denatured form, a water- insoluble, gritty, yellowish-brown powder that found limited use ([6]). Membrane filtration then arrived, which allowed for the separation and fractionation of whey proteins at ambient temperature and therefore retaining their solubility. A membrane is a barrier which separates two phases and restricts the transport of various chemical species in a rather specific manner. The driving forces arise from a gradient of chemical potential or electrical potential.
The permeability of the species depends on the membrane/solute/solvent interaction. The permeate flows through the membrane while passage of the retentate is blocked. In membrane filtration, the mobility of the species is primarily determined by the molecular size and the structure of membrane material. The dividing line between permeate and retentate is also expressed as the molecular weight cut off (MWCO).
Based on the pore size and species retained, membrane filtration usually classified as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) and microfiltration (MF) as shown in Table 1.2 Typical and species retained by MF, UF and RO membrane [7] The principle of membrane filtration was developed for water desalinization in the 1950s and applied to food processing starting in 1965. Whey processors employ these types of membrane filtration and electrodialysis (ED) and combination of these processes.
