kudra

Process Intensification for Drying and Dewatering

Marzouk Benali and Tadeusz KudraNatural Resources Canada, CanmetENERGY, Industrial Systems Optimization,Varennes, Quebec, Canada

Background information on process intensification including therationale, basic methods in process engineering, and interactionsbetween material streams and processing methods is given. Thegeneral rules are then examined with respect to heat and masstransfer intensification, and pertinent to drying techniques and tech-nologies (e.g., microwave drying, pulse combustion drying, intermit-tent drying, drying by alternation pressure, etc.) are highlighted.Milk processing for powdery product and bakery production is givenas an example of process intensification with respect to waterevaporation.

Keywords Acoustic drying; Electromagnetic energy; Hybridtechnology; Intensification; Intermittent drying; Pulsecombustion; Pulsed drying

INTRODUCTION

Apart from optimization and system engineering,process intensification (PI) is a growing trend in processengineering, aiming at the improvement of traditionaltechnologies and at the development of new techniques thatwill lead to higher production yield, notable reduction inequipment size (both principal and ancillary), lower energyuse and waste production, and increase product quality andprocessing safety, therefore offering more sustainable tech-nologies.[1–4] The growing interest in process intensificationresulted in a series of international conferences in this area,with the first launched in 1995; a recent one held in NewZealand in 2006[5] was devoted to the intensification ofseparation processes and bioprocesses. Examples of newdevelopments in process engineering intensification are thespinning disc reactor,[2,6,7] multifunctional reactors,[8,9] aswell as heat integration and reactive distillation.[10] Generalissues regarding process intensification such as method-ology, safety, process integration, contribution to sustain-able development, modeling, and others can be found insource books.[11,12]

The importance of process intensification is evidencedby the recent initiative of the European Union and the

Dutch government that resulted in the creation of theEuropean Roadmap for Process Intensification in fourmajor industrial sectors, namely, petrochemicals andbulk chemicals (PETCHEM), specialty chemicals andpharmaceuticals (FINEPHARM), food ingredients(INFOOD), and consumer food (CONFOOD).[13] Among72 typical equipment types and processing methodsidentified at the first step of which 47 technologies werethen reviewed in detail, including microwave heating=drying and the pulse combustion drying.[14] Though thePI Action Plan foresees a 20% reduction in industrialenergy consumption by year 2050 through PI implemen-tation alone,[13] the process intensification might notalways be highly effective but it should at least be con-sidered at the earliest stages of technology development.Whereas process intensification is well advanced in thechemical industry, its implementation in the food industryis far away from maturity, although this concept is suit-able for all operations where heat and mass transferproblems occur, mainly when processing viscous materialsor controlling microorganisms. Key food unit operationsoften require intensification either to minimize theadhesion=cohesion and clogging effects when processingsticky materials by mixing, homogenizing, membraneand contact-equilibrium separation or to shorten contacttime during thermal processes (e.g., pasteurization, evap-oration, drying) to reduce the capital and operating costsof a production system and to fully inactivate the micro-organisms. In addition, a need for process intensificationexists when new products cannot be made in conventionalequipment because, for example, the required puritycannot be achieved (e.g., lactic bacteria) or when thefailed processes do not give reproducible yields in conven-tional equipment (e.g., tomato pastes, soy derivatives).Thus, process intensification in the case of drying can beachieved by enhancing heat transfer and by integration ofthe proven, either new or hybrid, technologies into exist-ing plants. An example is lactose processing through fer-mentation, where the major technology barriers incost-effective production of high-purity lactic acid are theseparation and purification steps. Pal and coworkers[15]

have shown that the production of lactic acid can be

Correspondence: Marzouk Benali, Natural Resources Canada,CanmetENERGY, 1615 Lionel-Boulet Blvd., Varennes, Quebec,Canada J3X 1S6; E-mail: [email protected]

Drying Technology, 28: 1127–1135, 2010

Copyright # 2010 Crown Copyright

ISSN: 0737-3937 print=1532-2300 online

DOI: 10.1080/07373937.2010.502604

1127

intensified in a membrane-integrated process platform andit is economically viable.

The most common limitations encountered in dryingand dewatering can be categorized as follows:

� Heat transfer (e.g., rheology versus thermalresistance);

� Mass transfer (e.g., interfacial area);� Kinetics (e.g., sugar content versus diffusionmechanism).

The ultimate goal of process intensification in dryingand dewatering is to enhance the water removal rate whilesimultaneously considering either all these limitations ortheir various combinations.

Although process intensification is industrially oriented,its implementation requires profound knowledge in processengineering. Thus, plant managers as well as decisionmakers will likely ask drying experts for assistance, andsuch a demand will initiate new research if the solution isnot readily available. This article aims at guiding scientistsin up-front identification and evaluation of several inten-sification techniques that could lead to the selection ofthe particular techniques best suited to the technology ofinterest and therefore worth studying.

BACKGROUND TO PROCESS INTENSIFICATION

As pointed out in the European Roadmap for ProcessIntensification,[13] the definition of process intensificationchanged over the years from plant miniaturization tosustainability-related issues such as reducing costs, energyconsumption, material usage, and waste generation. Therecently adopted definition reads[16]: ‘‘Process intensifi-cation comprises novel equipment, processing techniques,and process development methods that, compared toconventional ones, offer substantial improvements in(bio) chemical manufacturing and processing.’’

Process intensification is scientifically founded in thefour domains[13] that can easily be spotted in various dryingand dewatering technologies and exploited alone or invarious combinations:

� Structure (spatial domain); e.g., dispersion ofliquids, foaming

� Energy (thermodynamic domain); e.g., targetedenergy transfer, internal heat generation

� Synergy (functional domain); e.g., hybrid technol-ogies, multistage and combined dryers

� Time (temporal domain); e.g., intermittent drying,time-dependent operating conditions.

Regarding the aforementioned definition, it is apparentthat any technological process can be the subject of processintensification as it aims at transforming the raw material(inlet stream), with certain physical–chemical properties,

into a product of required properties (outlet stream). Ingeneral, the inlet and outlet streams are composed of manystreams; for example, in drying, these are the streams of adrying material and drying agent. The transformation of araw material occurs due to sequential or parallel appli-cation of numerous processing methods that involve avariety of external forces. These processing methods canbroadly be categorized into mechanical (M), thermal (T),hydrodynamic (H), acoustic (A), electromagnetic (EM),chemical (Ch), and others (O), which could emerge in yearsto come. Each method is characterized by one or severaloperating parameters that can be relevant to a single pro-cessing method (e.g., heating rate in thermal methods) orseveral methods. An example of the latter is the frequencybeing pertinent to electromagnetic, acoustic, and hydro-dynamic processing methods.

The generic block diagram and the interaction schemefor an arbitrary technology are shown in Figs. 1 and 2. Ingeneral, the symbol ~XX represents a set of inlet materialstreams such as mass or volume (x1, x2, . . . , xn), eachbeing characterized by the set of unique propertiesðak1 ; ak2 ; . . . ; aknÞ, whereas ~YY represents the respective set ofoutlet material streams (y1, y2, . . . , yn) with propertiesðbk1 ; bk2 ; . . . ; bknÞ. In the case of drying, the inlet streamsmay constitute not only the wet material and drying gasbut also supplementary streams like the coating agent indrying of coated granules or webs, inert or active sorbentsin contact-sorption drying, or the bed material in a dryerwith bed mixing.[17] The superscript (k) represents the subsetof parameters or properties (k1, k2, . . . , kn) that selectivelyaffect certain unique properties (ai). Regarding hot air asthe common inlet stream (x1) in convective drying, theunique properties comprise humid heat (a1), enthalpy (a2),humidity (a3), temperature (a4), and others (viscosity, ther-mal conductivity, heat diffusivity, etc.). Temperature (k1)

FIG. 1. Principle of process intensification.

1128 BENALI AND KUDRA

and humidity (k2) can be given as examples of parametersidentified by the superscript (k) because they affect severalunique properties including humid heat and enthalpy. Someparameters such as temperature (k1) can also be consideredas unique properties that are shared by several materialstreams such as the wet material or coating liquid. Also,certain unique properties can encompass other properties;an example is air enthalpy, which depends on humid heat.

Some of the unique material properties such as materialmoisture content, for instance, may respond to the proces-singmethods through, for example, their mechanical, acous-tic, thermal, electromagnetic properties marked here by anasterisk (�). When thermal processing (T) is considered indrying, the key material properties (T�) are the heat capacityand thermal conductivity. However, in the case of othermethods, the number of properties to be regarded is muchhigher. For example, the EM� properties receptive toelectromagnetic treatment (EM) are dielectric constant, losstangent, electric and magnetic permittivity, attenuationconstant, ionic conductivity, etc. In ultrasound drying, thekey processing parameters are the frequency, soundintensity, sound pressure, and sound power, whereas thematerial properties susceptible to this processing methodare moisture content and type of moisture in the material(free or bound), surface tension, viscosity, absorption coef-ficient, which depend on both the processing parameters ofultrasound drying and material characteristics.

The degree to which a given property responds to aparticular processing method is different, and for a given

processing method the property may be highly receptiveand therefore of prime importance, whereas for others itis of secondary or tertiary importance. For example, inultrasound drying, water evaporation due to the thermaleffect of energy dissipation can be neglected in favor ofmechanical effects such as increased turbulence, alternatecompression and expansion leading to liquid flow throughcapillaries toward the material surface, directional dif-fusion, etc. Therefore, in ultrasound drying, both liquidviscosity and surface tension are of primary importancein contrast to heat capacity, which can be qualified as theproperty of secondary importance.

Similar levels of importance can also be applied to theprocessing methods. For example, frequency of ultrasoundis of primary importance when treating viscous liquids,whereas for nonviscous liquids this parameter is of second-ary or even tertiary importance. In pulse-fluidization thefrequency is of tertiary importance as it does not affectthe drying process in the range of developed fluidization(see Gawrzynski and Glaser[18]).

At present, there is no method to assign absolute valuesto the levels of importance, so the quantification is basedon the subjective comparison ‘‘less important than’’ and‘‘more important than’’ for a given parameter or property.Moreover, such quantification is not permanent butdepends on the process under examination as exemplifiedby the aforementioned frequency.

The use of various processing methods Ui,x, representedby the symbol ~UUx, allows transformation of the inletstreams ~XX into outlet ones ~YY in the apparatus of designcharacteristics signified by ~KK . The examples of such designcharacteristics are the hybrid and combined technologies,multistage dryers, dryers with varying temperature andhydrodynamic regimes, dryers with pulsating flow, anddryers with localized energy input. Another example is theconfiguration of a drying chamber that, for instance, affectsthe material flow pattern (e.g., in dryers with inert particles)or sound wave propagation (anechoic or reverberationchamber) that could lead to the acoustic resonance, as inthe case of pulse combustion (the so-called resonance-driven drying), or the generation of shock waves.[14,17]

It should be noted here that the overhead arrows atsymbols X ;Y ;U and K do not necessarily express the vectorper se but indicate the direction of material streams andprocessing methods. Figure 2 presents a conceptual gridfrom which the possible interactions between the materialand processing methods for a discretionary technologycould be identified and enumerated. Although arbitrarilyassigned for the illustration purpose, the symbols (þ), (�),and (0) signify the effect of a processing method on thematerial properties. Namely, the neutral symbol (0) indi-cates that a given method (Ux) does not affect the materialproperties. The positive symbol (þ) indicates that a givenprocessing method (Ux) alters the property of interest

FIG. 2. Interaction matrix (adapted from Kardashev[27]).

DRYING PROCESS INTENSIFICATION 1129

toward the desired value and thus intensifies the processunder consideration, so it can be termed the intensificationmethod. By contrast, the negative sign (�) denotes that sucha processing method (Ux) weakens the present susceptibilityof this property and thus impedes the process of interest.When none of these symbols can be assigned explicitly, agiven field remains empty. The symbols less than (<) andmore than (>) indicate that a given method yields inaddition to positive (þ) or negative (�) effects a critical(threshold) value, either the lower or the upper one. Thecombined symbol (< . . .<) points to the existence of bothcritical values for this processing method. These criticalvalues result from the process=material constraints such asthermal stability, runaway effect, breakdown, and others.

Regarding drying and dewatering, ultrasound irradiationis an example of a processing method with the upper criticalvalue because it is widely accepted that intensification ofmass transfer occurs when the sound intensity exceeds thethreshold value of about 140–145 dB.[17] Another exampleof the upper critical value is excessive intensity of evapor-ation as a result of high drying temperature. According tothe drying theory, the rate of drying increases with tempera-ture. However, at excessive drying temperature, a dry layer(the crust) may rapidly be formed on the material surface, sothe drying rate will decrease because the moisture mustdiffuse through this crust.[19–21] The crust formation isspecific to most food products. An example of restrictedevaporation due to crust formation is spray drying ofmilk, where the mix of lactose and protein in rawmilk formsthe shell through the glass transition that limits theevaporation of water from the droplet core. This negativephenomenon can, however, be beneficial as a method ofmicroencapsulation without the deliberately addedshell-forming material.[20]

An example of the lower critical value is the maximumtemperature in biologically enhanced drying (biodrying),where the temperature that enhances the drying rate islimited by microbial activity of bacteria to 48�C(mesophiles) or 68�C (thermophiles).[22,23]

Among several examples of both lower and uppercritical values is the air pulsation frequency in a pulsedfluid bed dryer, because below 4Hz and above 15Hz thisfrequency does not affect the drying rate.[18] Anotherexample is the ultrasound processing time because itspositive effect on water diffusivity during ultrasound pre-treatment prior to osmotic dehydration is insignificantbelow 10min and above 30–45min.[24]

By analyzing such interactions along with the process=apparatus constraints, certain processing methods can beexcluded or others can be considered. Moreover, if a givenprocessing method (Ux) positively affects several materialproperties, it should be subjected to further analysis toselect the property that permits reaching the target, but alsoother parameters of interest; for example, the ones needed

to attain the required moisture content at the maximumyield. Furthermore, sequential or parallel processing meth-ods should be examined, especially when the same materialproperty is receptive to different methods (e.g., distributionof liquid moisture in a drying material affects not only theinternal heat generation during MW drying [EM proces-sing] but also the heat transfer characteristics duringconvective drying [T]). A useful tool to analyze variousoptions for process intensification is the so-called TRIZapproach, which allows creative examination of difficult-to-solve technical problems[25,26] as well as the commerciallyavailable or custom-built databases on physical–chemicalphenomena, apparatus and equipment, material properties,and methods and algorithms for data processing.

Because of complex material properties, it is obvious thatdifferent processing methods intensify a given technology toa different extent. Figure 3 illustrates the degree of processintensification by acoustic and electromagnetic processing,defined as the ratio of a process rate subjected to a givenprocessing method to the rate when this method was notapplied.[27] Whereas the heat and mass transfer processescan be intensified to the same degree by using either the acous-tic or electromagnetic method, acoustic processing is a muchmore effective for mechanical and hydromechanical processesas opposed to chemical and microbiological processes, whichcan be intensified to a greater extent through the EMmethods.

Because drying is the simultaneous heat and masstransfer process, the following effects, induced by variousprocessing methods and modes of applications, result inprocess intensification:

1. Physical effects� Acoustic (infrasound, sound, ultrasound)� Shock waves (pressure, hydraulic)

FIG. 3. Intensification degree of basic processes by using the acoustic

(A) and electromagnetic (EM) processing methods (from Kardashev[27]).


� Cavitations, local turbulence� Resonance (mechanical, acoustic)

2. Nonstationary effects� Pulsation, vibration, oscillation, cycling(thermal hysteresis)

� Acceleration=deceleration, reverse and oppositeflow

3. Energy fields� Magnetic, electric, electromagnetic (IR, UV,RF, MW)

� Electro-technologies (electro-membranes,electro-plasmolysis)

4. Targeted energy supply� Microwave, ohmic heating� Electric discharge (electrohydraulic effect)� Discrete-impulse energy supply

5. Synergistic effects� Hybrid processes=hurdle approach.

With respect to drying, the following process upgrademethods can be considered for process intensification, asidefrom the aforementioned processing methods:

� Reducing resistance to heat=mass transfer(superheated steam, solid inserts)

� Extending interfacial area (foaming, inertparticles)

� Changing the mode of heat=mass transfer (e.g.,adding solid carriers to change liquid materialsinto capillary-porous ones, spraying of partiallyfoamed liquids onto inert particles)

� High-pressure processing and processing usingalternating pressure.

Whereas some of these intensification methods havebeen studied to a limited extent, others, such as microwavedrying, ultrasound drying, pulse combustion drying, orintermittent drying, have been the subject of extensiveresearch.[28–33] For example, the use of power ultrasoundfor orange peel drying enhances diffusion and mass trans-fer coefficients respectively by 34.10 and 51.85%, whichshortens the drying time by 48.60%.[33] When ultrasoundwas applied to carrot and lemon the drying time was alsosignificantly shortened (35–40%).[32]

As seen in Fig. 1, process intensification encompassesboth equipment (hardware) and methods (software). Indrying, the hardware examples are the pulsed fluid beddryer, impinging stream dryer, or rotating-jet spoutedbed dryer; drying in acoustic or electromagnetic field,

FIG. 4. General process intensification methodology.


drying with shock waves, or sound-assisted drying can begiven as examples of intensification methods. In certaincases, the PI in drying is of a dual nature. An example ispulse combustion drying recognized as a process of pulsedcombustion (effect of sound wave, enhanced turbulence,hydrodynamic dispersion of the feed, and the like) but alsoas an apparatus because pulsed combustion calls for aspecial dryer or, at least, a pulse combustor.[14,17] Anotherexample is drying on inert particles, seen as a processperformed in a specialized apparatus such as jet spoutedbed dryer or modifications of the rotary, fluid bed, andvibrating-fluid bed dryers. Figure 4 depicts the generalmethodology that can be used for process intensification.

POTENTIAL APPLICATIONS OF PROCESSINTENSIFICATION

Dairy Industry

Aside from direct consumption, milk is the raw materialfor the production of a variety of food products made indairy processing plants.[34] These plants are commonlydivided into two categories:

� Milk processing, which involves the pasteurizationof liquid milk for direct consumption, as well asfurther processing into buttermilk, creams, choc-olate, and other types of flavored milk

� Milk conversion, where liquid milk is transformedthrough chemical and biochemical processes intovalue-added products, including cheese, butter, icecream, condensed and evaporated milk, dried milkpowder, yogurt, and other cultured milk products.

The sequence of basic steps in a dairy process is shownin Table 1.

Energy consumption in the food and beverage industryrepresents about 4% of total energy consumed by theCanadian manufacturing sector. Within this subsector,the dairy industry as a whole (i.e., fluid milk processing

and industrial dairy products), the energy consumption ison the order of 12.0 PJ=year. In the case of fluid milkprocessing, the total specific energy consumption in 17plants varies from 600 to 820 kJ=L. Table 2 presents thespecific energy consumption for small, medium, and largedairy plants.[35]

A recent process integration study performed byNRCan=CanmetENERGY in two Canadian dairy plantshas demonstrated potential of fuel savings on the orderof 20 to 30%, corresponding to $0.44 to 1.10 million, aswell as the potential of CO2 emissions reduction of 4,000to 5,000 tons=year.

Figure 5 illustrates a general flowchart of a dairy proces-sing plant. Clearly, homogenization, pasteurization, cool-ing, preheating, evaporation, drying, and agglomerationare the key cross-cutting steps that could be intensified.The analysis of heating and cooling requirements of variousprocess streams reveals that, in an optimal design, no steam,natural gas, or hot air should be used as a heating mediumin processes performed at temperatures below 70�C. In suchan optimal design, glycol, chilled water, or lake watershould not be used to cool a material stream that has a tem-perature higher than 8�C. To achieve an optimal heat recov-ery in the entire production process, all heat exchangersshould have a temperature difference between cold=hotstreams of 5–10�C. The major process inefficiencies spottedin various dairy plants can result from:

� No preheating of the drying air� No energy recovery from the humid air exiting thedryer

� Mixing of drying air at approximately 210�C withdehumidified air at 25–30�C

� No energy recovery from flue gases at the boilerexhaust

� Inefficient preheating of the milk in the upstreamto pasteurization using waste heat recovered fromthe evaporator.

TABLE 1Dairy industry: Key processing steps

Steps Processes

1. Transfer of momentum Pumping and flow of all materials and ingredients2. Heat transfer Heating and cooling3. Mixing Stirring, atomization, homogenization, and recombination4. Phase separation Skimming, separation of milk powder from drying air, churning5. Molecular separation Evaporation, drying, membrane processes (ultrafiltration,

nanofiltration, etc.), and crystallization6. Physical transformation Gel formation, butter making, and ice cream7. Microbiological and enzymatic transformation Production of fermented products, cheese, and ripening8. Stabilization Pasteurization, sterilization, cooling, and freezing


The inefficiencies can also result from the equipment andapparatus. For instance, on the cheese production line, theheat exchanger that transfers energy between the whole milkand the pasteurized milk is not often optimally placed fromthe energy recovery viewpoint. A redesign of the presentenergy regeneration system is, however, technically feasibleand economically viable; integration of four additional heatexchangers linked with milk pasteurizing, cream cooling,whey cooling, and milk vats would offer the respectiveannual energy savings of 540, 113, 450, and 163 kW.

Bakery Industry

The bakery industry is one of the major energy-intensivefood processing industries. In 2007, Canadian bakeriesconsumed 10.5 PJ of energy supplied by electricity (41.3%)and natural gas (58.7%). In bakeries, about 80–85% of thetotal energy is consumed for the baking process as thermalenergy at 180–360�C,[36] of which a great fraction is usedfor water evaporation. Radio frequency (RF) heatinghas recently found use as intensification technique in thefood industry for cooking, baking, and drying applications.The main reasons for the use of radio frequency electro-magnetic field instead of microwaves are (1) lower attenu-ation of the electromagnetic wave by the processedmaterial and therefore more uniform heating, (2) largercontribution of power absorption by ionic conductionthan dipoles rotation, and (3) safety, simplicity, andflexibility of the RF system, especially if 50-ohmtechnology is used.[17]

In the food industry, RF heating has already foundapplications in after-baking drying of cookies, crackers,

FIG. 5. Simplified diagram of generic dairy process equences.

TABLE 2Average energy profile of 17 Canadian dairy plants

Throughput(106 L=year)

Specific energyconsumption (106 J=L)

20–50 0.8250–100 0.60>100 0.73


and pasta.[37] Accepting that high-temperature heatingis needed to accomplish certain transformations (e.g.,conversion of starch, caramelization of sugars), theaddition of heat through RF irradiation enhances waterevaporation and consequently shortens time of baking.As indicated by Clark,[38] by integrating RF heating, thethroughput of the baking production line can be increasedby 30 to 40%.

Even though in the food sector energy consumption isnot a major component of costs, rising energy prices willforce companies to consider savings through process inten-sification aside from higher yields, product quality, andfood safety. The potential benefits of PI that have beenidentified in the food sector roadmap include[13]:

� Higher energy efficiency in water removal leadingto 25% of energy savings in the short-=mid-term(5–10 years) and 75% in the long-term (10–15years; INFOOD)

� Lower costs through intensified processesthroughout the value chain: 30% (in 10 years)and 60% (in 30–40 years; INFOOD)

� Higher energy efficiency in preservation processesamounting to 10–15% (in 10 years) and 30–40%(in 40 years) of energy savings that comprises a60% through capacity increase and 30% (in 40years) through the transfer the mode of operationfrom batch to continuous processes (CONFOOD).

The realization of the PI-forecasted benefits will requireendeavors varying from technology R&D to scale-up andindustrial implementations.

CONCLUSIONS

The application of various techniques for processintensification can result in appreciable technical andeconomic benefits due to enhanced heat and mass transfercoefficients, internal heat generation, combined drivingforces, and others. Based on food processing data, thepotential use of alternative sources of energy as a methodfor process intensification appears to be very promising.For example, the application of power ultrasound andradio frequency heating leads to enhanced diffusion andmass transfer coefficients by 34.10 and 51.85%, respect-ively, which shortens the drying time by 35–40%.

In drying it is a common to work on advanced technol-ogies by a priori selection of the apparently suitable inten-sification method. However, up-front identification andevaluation of possible intensification methods could leadto the selection of a particular method best suited to thedrying technology to be intensified. Such identificationand evaluation could be accomplished with the guidelinespresented in this article.

NOMENCLATURE

EM ElectromagneticGHG Greenhouse gasIR InfraredMt CO2-eq Mega tones of CO2 equivalentMW MicrowavePI Process intensificationPJ Peta joules (1015 J)PSE Process systems engineeringRF RadiofrequencyUV Ultraviolet

REFERENCES

1. Jachuck, R.J.; Lee, J.; Kolokotsa, D.; Ramshaw, C.; Valachis, P.;

Yanniotis, S. Process intensification for energy saving. Applied

Thermal Engineering 1997, 17, 861–867.

2. Aoune, A.; Ramshaw, C. Process intensification: Heat and mass

transfer characteristics of liquid films on rotating discs. International

Journal of Heat and Mass Transfer 1999, 42, 2543–2556.

3. Ramshaw, C. Process intensification and green chemistry. Green

Chemistry 1999, 1, G15–G17.

4. Stankiewicz, A.I.; Moulijn, J.A. Process intensification. Industrial &

Engineering Chemistry Research 2002, 41 (8), 1920–1924.

5. Tsouris, C.; Weatherley, L. Process intensification and innovation

process (PI) 2 conference II—Cleaner, sustainable, efficient technolo-

gies for the future. Chemical Engineering Journal 2007, 135, 1–2.

6. Boodhoo, K.V.K.; Jachuck, R.J. Process intensification: Spinning disc

reactor for styrene polymerisation. Applied Thermal Engineering

2000, 20 (12), 1127–1146.

7. Brechtelsbauer, C.; Lewis, L.; Oxley, P.; Ricard, F. Evaluation of a

spinning disc reactor for continuous processing. Organic Process

Research & Development 2001, 5, 65–68.

8. Dautzenberg, F.M.; Mukherjee, M. Process intensification using

multifunctional reactors. Chemical Engineering Science 2001, 56,

251–267.

9. Nigam, K.D.P.; Larachi, F. Process intensification in trickle-bed reac-

tors. Chemical Engineering Science 2005, 60, 5880–5894.

10. Stankiewicz, A.I. Reactive separations for process intensification: An

industrial perspective. Chemical Engineering and Processing 2003, 42

(3), 137–144.

11. Stankiewicz, A.I.; Moulijn, J.A. Re-Engineering the Chemical

Processing Plant: Process Intensification; Marcel Dekker: New York,

2004.

12. Keil, J.F., Ed. Modeling of Process Intensification; Wiley-VCH Verlag

GmbH&Co. KGaA: Weinheim, Germany, 2007.

13. Creative Energy. European Roadmap for Process Intensification; The

Netherlands. Available at: http://www.creative-energy.org (accessed

August 2009).

14. Kudra, T. Pulse-combustion drying: Status and potentials. Drying

Technology 2008, 26 (12), 1409–1420.

15. Pal, P.; Sikder, J.; Roy, S.; Giorno, L. Process intensification in lactic

acid production: A review of membrane based processes. Chemical

Engineering and Processing: Process Intensification 2009, 48

(11–12), 1549–1559.

16. Moulijn, J.A.; Stankiewicz, A.; Grievink, J.; Gorak, A. Process

intensification and process systems engineering: A friendly symbiosis.

Computers and Chemical Engineering 2008, 32 (1–2), 3–11.

17. Kudra, T.; Mujumdar, A.S. Advanced Drying Technologies, 2nd Ed;

CRC Press: Boca Raton, 2009.

18. Gawrzynski, Z.; Glaser, R. Drying in pulsed-fluidized bed with

relocated gas stream. Drying Technology 1996, 14 (5), 1121–1172.


19. Dolinsky, A. Theory and Practice of Processes of Spray Drying;

Institute of Engineering Thermophysics, Ukrainian Academy of

Sciences: Kiev, 1989.

20. Gharsallaoui, A.; Roudaut, G.; Chambin, O.; Voilley, A.; Saurel, R.

Applications of spray-drying in microencapsulation of food

ingredients: An overview. Food Research International 2007, 40,

1107–1121.

21. Young, S.L.; Sarda, X.; Rosenberg, M. Microencapsulating properties

of whey proteins. 1. Microencapsulation of anhydrous milk fat.

Journal of Dairy Science 1993, 76, 2863–2877.

22. Krzystek, L.; Zawadzka, A.; Ledakowicz, S. Biodrying of organic

fraction of municipal solid waste. In Proceedings of the 8th World

Congress of Chemical Engineering, Montreal, Canada, August

23–27, 2009 (on USB).

23. Navaee-Ardeh, S.; Bertrand, F.; Stuart, P.R. Emerging biodrying for

the drying of pulp and paper mixed sludge. Drying Technology 2006,

24 (7), 863–878.

24. Fabiano, A.; Fernandes, N.; Rodrigues, S. Application of ultrasound

and ultrasound-assisted osmotic dehydration in drying of fruits.

Drying Technology 2008, 26 (12), 1509–1516.

25. Altshuller, G.S. Creativity as an Exact Science; Gordon and Breach

Science Publishers: New York, 1984.

26. Srinivasan, R.; Kraslawski, A. Application of the TRIZ creativity

enhancement approach to design of inherently safer chemical

processes. Chemical Engineering and Processing 2006, 45, 507–514.

27. Kardashev, G.A. Physical Methods of Process Intensification in

Chemical Technology; Khimia: Moscow, 1990 (in Russian).

28. Chua, K.J.; Mujumdar, A.S.; Chou, S.K. A review on intermittent

drying processes. Bioresource Technology 2003, 90, 285–295.

29. Dev, S.R.S.; Padmini, T.; Adedeji, A.; Gariepy, Y.; Raghavan, G.S.V.

A comparative study on the effect of chemical, microwave, and pulsed

electric pretreatments on convective drying and quality of raisins.


30. Feng, H.; Tang, J. Microwave finish drying of diced apples in a

spouted bed. Journal of Food Science 1998, 63 (4), 679–683.

31. Garcia-Perez, J.V.; Carcel, J.A.; Riera, E.; Mulet, A. Influence of the

applied acoustic energy on the drying of carrots and lemon peel.


32. Garcia-Perez, J.V.; Carcel, J.A.; Benedito, J.; Mulet, A. Power ultra-

sound mass transfer enhancement in food drying. Transactions of the

Institution of Chemical Engineers, Food and Bioproducts Processing

2007, 85 (C3), 247–254.

33. Ortuno, C.; Perez-Munuera, I.; Puig, A.; Riera, E. Influence of power

ultrasound application on mass transport and microstructure of

orange peel during hot air drying. Physics Procedia 2010, 3, 153–159.

34. Speer, E. Milk and Dairy Product Technology; Marcel Dekker:

New York, 1998.

35. Energy Performance Indicator Report: Fluid Milk Plants; Natural

Resources Canada, Cat. No.: M92–228=2001E. Natural Resources

Canada Office of Energy Efficiency: Ottawa, Ontario, 2001.

36. Kannan, R.; Boie, W. Energy management practices in CME—Case

study of a bakery in Germany. Energy Conversion & Management

2003, 44, 945–959.

37. Orsat, V.; Raghavan, G.S.V. Radio frequency processing. In Emerg-

ing Technologies for Food Processing; Sun, D.W., Ed.; Elsevier

Academic Press: Amsterdam, 2005; 445–468.

38. Clark, P. Pulsed electric field processing. Food Technology 2006, 60,

66–67.


Copyright of Drying Technology is the property of Taylor & Francis Ltd and its content may not be copied or

emailed to multiple sites or posted to a listserv without the copyright holder's express written permission.

However, users may print, download, or email articles for individual use.

Documents

kudra