modeling & simulation of direct contact membrane dcmd
TRANSCRIPT
MODELING & SIMULATION OF DIRECT CONTACT MEMBRANE
DISTILLATION(DCMD)
DATE: 11TH MAY 2011
CONTENTS
1. Introduction
2. Literature survey
3. Modeling
4. Results and Discussion
5. Conclusion
6. Sample simulation
References
1. INTRODUCTION
1. Membrane Distillation○ Classification of Membrane Distillation
2. Direct Contact Membrane Distillation(DCMD)
• Advantages of DCMD• Application of DCMD
MEMBRANE DISTILLATION(MD)
Membrane distillation (MD) is a mass transport process of volatile components that takes place across the pores of non-wetted membranes.
In this process, a hydrophobic porous membrane is used, which is in direct contact with a hot feed.
CLASSIFICATION OF MD
Direct contact Membrane Distillation(DCMD)
Air gap membrane distillation(AGMD)
Sweep gas membrane distillation(SGMD)
Vacuum membrane distillation(VMD)
DCMD DCMD is thermally driven process. In DCMD the permeate side is in direct contact with cold
aqueous solution. Trans-membrane temperature difference induces a
vapour pressure difference causing vapour to pass through membrane pores.
Evaporation of volatile component of a feed at warm feed membrane interface.
Transfer of vapour. Condensation of permeate at the other end (distillate
end). Almost negligible pressure difference across the
membrane.
CONFIGURATION OF DCMD
ADVANTAGES OF DCMD Practically complete (100%) rejection of
dissolved non-volatile species. Lower operating pressure than pressure driven
membrane. Reduced vapour space compared to
conventional distillation. Lower operating temperature of feed enables
the utilization of waste heat as a preferable energy resources.
Theoretically almost 100 % of purity is possible.
APPLICATION OF DCMD
Vapor permeation Water purification Fruit juice concentration Concentration of acid solution Waste water treatment
2. LITERATURE SURVEY
Recent studies in DCMD Operating variables affecting DCMD
process Mechanism: Desalination using DCMD Model review from literature Data Collected
RECENT STUDIES IN DCMDYear Topic Researchers
2010 Modeling of Direct Contact Membrane Distillation for Desalination.
Edward Close, Eva Sørensen,Department of Chemical Engineering, University College London (UCL), Torrington
Composite Membranes for Membrane Distillation Desalination Process.
Sai R. Pinappu,Chemical Engineering Department, New Mexico State University
A theoretical study of a direct contact membrane distillation system coupled to a salt-gradient solar pond for terminal takes reclamation.
Francisco Suarez, Scott W. Tyler, Amy E. Childress,University of Nevada, Reno, USA
2009 Surface modification of nanostructured ceramic membranes for direct contact membrane distillation.
Z.D. Hendren, J. Brant, M.R. Wiesner ,Department of Civil and Environmental Engineering, Duke University, Durham, USA
Year Topic Researchers
2008 Solar desalination of brackish water using membrane distillation process.
Shuguang Deng ,New Mexico Water Resources Research Institute, New Mexico State University
2007 The potential of membrane distillation as a stand-alone desalination process.
A.M. Alklaibi Jeddah College of Technology, KSA
2006 A framework for better understanding membrane distillation separation process.
(i) M.S. El-Bourawi , (i)Z. Ding , R. Maa, (ii)M. Khayet (i)State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing ,China (ii)Department of Applied Physics, University Complutense of Madrid, Spain
Year Topic Reseacher
2005 Mass transfer mechanisms and transport resistances in direct contact membrane distillation process
Surapit Srisurichana, Ratana Jiraratananona , A.G. Faneb, King Mongkut’s University of Technology Bangkok, Thailand
2004 Desalination by membrane distillation adopting a hydrophilic membrane
Ping Peng, A.G. Fane, Xiaodong Li UNESCO Centre for Membrane Science and Technology, University of New South Wales, Australia .
2003 Experimental study of desalination using direct contact membrane distillation: a new approach to flux
Tzahi Y. Cath, V. Dean Adams, Amy E. Childress University of Nevada, Reno, NV, USA
2002 Mathematical modeling of influence of porous structure a membrane on its vapor-conductivity in the process of membrane distillation
(i)Valery V. Ugrozova, (ii) Inga B. Elkinab (i)Moscow State University of Food Industry, Moscow, Russia (ii)Tufts University, Medford, MA 02155, USA
Year Topic Researchers
2001 DCMD with Crystallization Applied to NaCl Solution.
M. GRYTA, Institute of Chemical Technology and Environmental Engineering, Technical University of Szczecin, Poland
2000 Membrane Distillation: Applications in Technology and Environmental Protection.
M. Tomaszewska Institute of Inorganic Chemical Technology, Technical University of Szczecin, Poland
OPERATING VARIABLES AFFECTING DCMD PROCESS
Feed inlet concentration Feed temperature Cold liquid temperature Feed circulation velocity and stirring rate Permeate velocity Vapor pressure difference Membrane parameter
Pore sizePorosityThickness
MECHANISM: DESALINATION USING DCMD
MODEL REVIEW FROM LITERATURE
From: Edward Close and Eva Sorensen, Modelling of DCMD for Desalination, Department of Chemical Engineering, University College London, Torrington
Rm(t) : membrane resistanceRc(t): concentration polarization resistanceRf(t): membrane fouling resistanceYln: logarithm mean pressure of gas
From: Yanbin Yun, Runyu Ma, Wenzhen Zhang, A.G.Fane, Jiding Li, DCMD mechanism for high Concentration NaCl Solutions, Department of Chemical Engineering, Tsinghua University, Beijing, China
LIST OF DATA USED FROM LITERATURE
Porosity: ԑ = 0.6 Membrane thickness: δ = 100μm Nominal pore size: r= 0.3 μm Tortuosity: τ = 2 (ԑ/τ)δ = 3000 m-1 We are using standard form of
correlation for heat transfer: Nu= 0.023 Re0.8 Pr 0.33
{Duittus-Boiler correlation}
Nu= Nussel number Re= Reynolds number :
1035<Re<5125 Pr= Prendtle number : 2.7<Pr<3.9 For feed side: Ref = 1300
Velocity: uf = 0.1 m/s μ=0.54cp Density of feed: ρ= 1034Kg/m3
Prandtle number: Pr = 3.1
Nu=12.16 Nu=hf.D/K
From experiment we took, D=1.6cm Kwater= 0.58 W/m
Thus, hf=760W/m2K
hm= (ԑkg + (1-ԑ)km )/δ
kg= 0.016
km=0.05 hm=296 W/m2 K
For permeate side: Rep= 676
hp = 222 W/m2K
∆Hv=2270 Joules/Kg
ADDITIONAL EQUATIONS USED
ρf= [(2160 xf+ (1-xf) ]
μcp= C1+ C2exp(x1T) +C3exp(x3m) +C4exp[x3(0.01T+m)] +C5exp[x4(0.01T-m)]
Cpf= (xfCpNaCl/MNaCl) + (1-xf)(a+bT+cT2+ dT3)MNaCl
m= molality of solution = 1000 Xf/58.5
FROM: aOzbek, H., Viscosity of aqueous sodium chloride solutions from 0 - 150oC, Lawrence Berkeley National Laboratory- 09-10-2010http://escholarship.org/uc/item/3jp6n2bfb http://en.wikipedia.org/wiki/Viscosityc Himmelblau David M., Basic principles and calculations in chemical engineering, Sixth Edit-ion, Pearson Education
3. MODELING
Assumptions used in mathematical modeling:
The contribution of Poiseuille flow to mass transfer is neglected.
Kinetic effect at the vapour liquid interface are neglected.
Membrane should not alter vapour liquid equilibrium of different components.
The permeation of vapour through the membrane is regulated by Knudsen-molecular diffusion mechanism.
Mass Transfer in DCMD:
Heat transfer in DCMD:
4. RESULTS AND DISCUSSTION
• Effect of feed flow rate on flux• Effect of salt concentration• Effect of feed temperature on permeate flux• Effect of permeate temperature on flux• Effect of membrane thickness on Flux• Effect of membrane porosity on Flux• Effect of membrane pore diameter on flux• Effect of Feed side Heat transfer coefficient
The computational simulation of each operating parameter v/s permeate flux have been carried out using MATLAB
The experimental data were collected from the following:
1. Stephanie Lacoursiere, Water purification by membrane distillation, McGill University, Montreal, Canada (2005)
2. Dr. Kamalesh K. Sirkar, Dr. Baoan Li, “Novel membrane and device for Direct contact membrane distillation-based desalination process: phase II ”, New Jersey Institute of Technology, Newark, New Jersey (July 2003)
EFFECT OF FEED FLOW RATE ON FLUX
Feed flow rate increases sharply at lower flow rate and reaches asymptotes at higher flow rates.
EFFECT OF SALT CONCENTRATION
Slight decreases in flux is observed with increase in feed concentration
EFFECT OF FEED TEMPERATURE ON PERMEATE FLUX
Flux increases exponentially with increase in feed temperature
EFFECT OF PERMEATE TEMPERATURE ON FLUX
Decrease in flux observed on increase in permeate temperture
EFFECT OF MEMBRANE THICKNESS ON FLUX
Flux decreases sharply with increase in membrane thickness
EFFECT OF POROSITY ON FLUX
A steep increase in flux is observed on increasing the porosity
EFFECT OF PORE DIAMETER ON FLUX
Flux increases almost linearly on increase in pore diameter
EFFECT OF FEED SIDE HEAT TRANSFER COEFFICIENT
Flux increases linearly with increase in feed side heat transfer coefficient
5. CONCLUSION
Close relation was found between the results given by the model and actual experiments presented in the literature.
Using this model, we can now determine the optimal operation and design of this unit.
Where there were conflicting results in the literature regarding the effect of the variables on the flux, the model was able to provide an explanation.
6. SAMPLE SIMULATION IN MATLAB
Thickness v/s Flux
d2=[.000025 .000045 .000056 .000098 .000150 .000250 .000350];
for i=1:7
Tf=323;
Tp=298;
E=0.6;
M=.018;
M1=.0585;
R=8.314;
d1=3.*10.^-7;%pore dia
D=.016;%dia of duct
Pt=(1.01).*(10.^5);
t=2;%totiosity
Ks=0.05;
Kg=0.0235;
Kf=.58;
Kp=.58;
Km=((E).*(Kg)+((1-E).*(Ks)));
Hm=((Km)./(d2(i)));
Xf=.03;
Xfm(1)=Xf;
m=(Xf.*1000)./(58.5);
Tfm(1)=Tf;
Tpm(1)=Tp;
%Reynolds Number Feed Side
df=(Xf.*((2.16).*(10.^3))+(1-Xf).*((999.8395)./(1+0.0002.*(Tf-273))));
Vf=.1;
A11=0.1256735+(1.265347).*exp((-0.04296718).*(Tf-273))-(1.105369).*exp((0.3710073).*m);
B11=(0.2044679).*exp(0.4230889.*((0.01).*(Tf-273)+m))+(1.308779).*exp((-0.3259828).*((0.01).*(Tf-273)-m));
Uf=(A11+B11).*(10.^-3);
Ref=(df.*Vf.*(D))./(Uf);
%Reynolds Number Permeate Side
Vp=.1;
dp=(999.8395)./(1+0.0002.*(Tp-273));
Up=((2.414).*(10.^-5).*10.^((247.8)./(Tp-140)));
Rep=(dp.*Vp.*(D))./(Up);
%Feed side Cpf
Aa=18.2964;
Bb=(47.212).*(10.^-2);
Cc=(-133.88).*(10.^-5);
Dd=(1314.2).*(10.^-9);
Cpf=(Xf.*50.*(M1.^-1)+(1-Xf).*(Aa+(Bb.*Tf)+(Cc.*(Tf.^2))+Dd.*(Tf.^3)).*(M.^-1));
% permeate side Cpp
Cpp=(Aa+(Bb.*Tp)+(Cc.*(Tp.^2))+Dd.*(Tp.^3)).*(M.^-1);
S=(2.303).*(8.3144);Ppm(1)=exp(23.238-(3841./(Tpm(1)-45)));Pofm(1)=exp(23.238-(3841./(Tfm(1)-45)));Pfm(1)=(1-Xfm(1)).*(1-0.5.*(Xfm(1))-10.*(Xfm(1).^2)).*(Pofm(1)); Tm(1)=((Tfm(1)+Tpm(1))./2); Dab(1)=(((1.895).*(10.^(-5))).*(Tm(1).^2.02))./(Pt); SS(1)=((1.895).*(10.^(-5))).*(Tm(1).^2.02); YY(1)=(Pt-Pfm(1));Y(1)=(YY(1))./(SS(1)); X(1)=(Pt-Ppm(1))./SS(1);C(1)=((.75)./d1).*((((6.28).*M)./(R.*Tm(1))).^(0.5));B(1)=(E./(t.*d2(i))).*(SS(1)./(R.*Tm(1))).*log((X(1)+C(1))./(Y(1)+C(1)));for j=1:10Z(j)=(Pfm(j)./Ppm(j));a(j)=(Tpm(j).^(-1));b(j)=Tfm(j).^(-1);TT(j)=((a(j))-(b(j))).^(-1);A(j)=(S).*(log10(Z(j))).*(TT(j)).*((.018).^-1)./(10.^3);%heat of vaporisation Dab(j)=(((1.895).*(10.^(-5))).*(Tm(j).^2.02))./(Pt); % Schmidt NumberScf(j)=(Uf)./((df).*(Dab(j))); %Pradetal Number of Feed SidePrf(j)=((Uf.*Cpf)./(Kf)); %Prandetal Number of permeate sidePrp(j)=((Up.*Cpp)./(Kp)); %Nusselt Number for feed sideNuf(j)=(0.023).*((Ref).^0.8).*((Prf(j)).^0.3); %Nusselt Number for Permeate sideNup(j)=(0.023).*((Rep).^0.8).*((Prp(j)).^0.3);% Feed side Heat transfer coefficientHf(j)=((Kf).*(Nuf(j)))./(D); Ks(j)=((0.023).*((Ref).^0.8).*((Scf(j)).^0.33).*(Dab(j)))./(D); %Permeate side Heat transfer coefficientHp(j)=((Kp).*(Nup(j)))./(D); Tfm(j+1)=(Hm.*(Tp+Tf.*(Hf(j)./Hp(j)))+Hf(j).*Tf-(B(j)).*(A(j)))./(Hm+Hf(j).*(1+Hm./Hp(j)));
pm(j+1)=(Hm.*(Tf+(Tp.*(Hp(j)./Hf(j))))+Hp(j).*Tp+(B(j)).*(A(j)))./(Hm+Hp(j).*(1+(Hm./Hf(j))));Xfm(j+1)=(Xf).*exp((B(j))./((Kf).*(df)));Ppm(j+1)=exp(23.238-(3841./(Tpm(j+1)-45)));Pofm(j+1)=exp(23.238-(3841./(Tfm(j+1)-45)));Pfm(j+1)=(1-Xfm(j+1)).*(1-0.5.*(Xfm(j+1))-10.*(Xfm(j+1).^2)).*(Pofm(j+1)); Tm(j+1)=((Tfm(j+1)+Tpm(j+1))./2);SS(j+1)=((1.895).*(10.^(-5))).*(Tm(j+1).^2.02);YY(j+1)=(Pt-Pfm(j+1));Y(j+1)=(YY(j))./(SS(j)); X(j+1)=(Pt-Ppm(j+1))./SS(j+1);C(j+1)=((.75)./d1).*((((6.28).*M)./(R.*Tm(j+1))).^(0.5));B(j+1)=(E./(t.*d2(i))).*(SS(j+1)./(R.*Tm(j+1))).*log((X(j+1)+C(j+1))./(Y(j+1)+C(j+1))); if B(j+1)<B(j) AA(j+1)=B(j+1); BB(j+1)=B(j); else AA(j+1)=B(j); BB(j+1)=B(j+1); end FF(j+1)=((.05).*(B(j+1))); if le((BB(j+1)-AA(j+1)),FF(j+1))==1 V(i)=B(j+1); break endendh1=plot(d2,V);set(h1,'marker','<','markerFacecolor','g','linewidth',2)title('Graph-Thickness v/s Flux','fontsize',20)xlabel('Thickness (micro meter)')ylabel('Flux(N) [Kg.m^-2.Sec^-1]') hold onV=[.0845 .0754 .0689 .0468 .0465 .0298 .0197];h2=plot(d2,V,'linestyle','none');set(h2,'marker','s','markerFacecolor','r') legend('Theoritical Data','experiment Data') hold off
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