The 7 h In e na ional Symposium on Design, Ope a ion and Con ol o Chemical P ocesses (PSE ASIA 2016)
[p ep in ]
INTEGRATION OF POWER RETARDED OSMOSIS IN SOLAR
MULTIEFFECT DESTILLATION
Khaled Toua i, Fe nando TADEO*
Indus ial Eng. School, Uni e si y o Valladolid, D . Me gelina S/N, 47002 Valladolid, SPAIN
e nando@au om.u a.es
ABSTRACT: A Sola -Ene gy Powe ed Desalina ion Sys em is p oposed and e alua ed he e. I is based on he
use o Sola Mul i-e ec Dis illa ion (S-MED) plan s ha in eg a e osmo ic ene gy eco e y sys ems, which
makes i possible o imp o e he e iciency o he p ocess, p o iding a cos -e ec i e app oach o desalina ion
using sola ene gy.
Keywo ds: Osmo ic Powe ; Concen a ed Sola Powe ; Desalina ion.
1 In oduc ion
Wa e sca ci y is among he main p oblems o be aced by many socie ies and he Wo ld in he XXI cen u y.
Wa e use has been g owing a mo e han wice he a e o popula ion inc ease in he las cen u y, and, an
inc easing numbe o egions a e ch onically sho o wa e . Wa e desalina ion is one o he mos impo an
solu ions p o ided o sa is y he wa e demand and one o he mos p omising ields o he applica ion o sola
he mal ene gy due o he coincidence, in many places o he wo ld, o wa e sca ci y, seawa e a ailabili y and
good le els o sola adia ion.
Fo highe desal ing capaci ies, i is necessa y o choose con en ional dis illa ion plan s coupled o a sola
he mal sys em, which is known as indi ec sola desalina ion. Dis illa ion me hods used in indi ec sola
desalina ion plan s a e mul i-s age lash Dis illa ion me hods used in indi ec sola desalina ion plan s a e mul i-
s age lash (MSF) and mul i-e ec dis illa ion (MED). MSF plan s, due o ac o s such as cos and appa en high
e iciency, pushed ou MED sys ems in he six ies, and only small size MED plan s we e buil . Howe e , in his
las decade, in e es in mul i-e ec dis illa ion has been signi ican ly enewed and cu en ly MED p ocess is
compe ing echnically and economically wi h al e na i e echnologies: Recen ad ances in esea ch o low
empe a u e p ocesses ha e esul ed in an inc ease o he desal ing capaci y and a educ ion in he ene gy
consump ion o MED plan s [3], p o iding long- e m ope a ion unde ema kable s eady condi ions. Scale
o ma ion and co osion wi h cu en p ocess a e minimal, leading o excep ionally high plan a ailabili ies o
94% o 96%.
Sola he mal des illa ion is selec ed as he co e echnology due o i s eliabili y, simple ope a ion and
main enance, ma u i y and high pu i y o he p oduced wa e . In pa icula , om he he mal desalina ion
p ocesses, Mul i-e ec Des illa ion (MED) has he highes he mal e iciency and he lowes powe
consump ion, so i is selec ed he e, combined wi h a enewable sou ce o he mal ene gy: Sola ene gy would be
used as his he mal sou ce, as hese S-MED sys ems ha e al eady been shown o be easible and e icien [1].
Mo eo e sola i adia ion is high when wa e demand is high.
Following ecen ad ances in Concen a ed Sola Powe (CSP) [2], and he mal s o age sys ems [3], CSP wi h
he mal s o age is p oposed as he sou ce o he mal ene gy o SED. As has been men ioned, a cen al aspec o
imp o ing he ene gy e iciency o his p ocess, which is unique o his p ojec , is he eco e y o salini y ene gy
om he b ines. Fo his, salini y g adien echniques [4,5] a e included in he p oposal, as hey ha e shown
good pe o mance in ealis ic si ua ions. In pa icula , Powe Re a ded Osmosis (PRO) is selec ed, as he au ho s
o his p oposal ha e al eady shown ha i pe o ms well a he high empe a u es associa ed wi h he b ines o
S-MED sys ems [6].
2 Summa y o he P oposal
The Sola E icien Desalina ion (SED) sys em p oposed he e o enewable desalina ion is schema ized in
Figu e 1: i is based on he use o Sola Mul i-e ec Des illa ion (S-MED) plan s ha in eg a e osmo ic ene gy
eco e y sys ems, which makes i possible o imp o e he e iciency o he p ocess, p o iding a cos -e ec i e
app oach o desalina ion using sola ene gy.
July 24-27, 2016, Tokyo, Japan
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Figu e 1: Gene al scheme o he componen s o he p oposed sys em
Sola he mal des illa ion is selec ed as he co e echnology due o i s eliabili y, simple ope a ion and
main enance, ma u i y and high pu i y o he p oduced wa e . In pa icula , om he he mal desalina ion
p ocesses, Mul i-e ec Des illa ion (MED) has he highes he mal e iciency and he lowes powe
consump ion, so i is selec ed he e, combined wi h a enewable sou ce o he mal ene gy: Sola ene gy would be
used as his he mal sou ce, as hese S-MED sys ems ha e al eady been shown o be easible and e icien [1].
Mo eo e sola i adia ion is high when wa e demand is high. Following ecen ad ances in Concen a ed Sola
Powe (CSP) [2], and he mal s o age sys ems [3], CSP wi h he mal s o age is p oposed as he sou ce o
he mal ene gy o SED. As has been men ioned, a cen al aspec o imp o ing he ene gy e iciency o his
p ocess, which is unique o his p ojec , is he eco e y o salini y ene gy om he b ines. Fo his, salini y
g adien echniques [4,5] a e included in he p oposal, as hey ha e shown good pe o mance in ealis ic
si ua ions. In pa icula , Powe Re a ded Osmosis (PRO) is selec ed, as he au ho s o his p oposal ha e al eady
shown ha i pe o ms well a he high empe a u es associa ed wi h he b ines o S-MED sys ems [6].
3 Re iew o echnologies
The main echnologies in ol ed in he p oposed sys em a e now b ie ly p esen ed:
3.1 Mul i-e ec Des illa ion
A ypical o wa d- eed e ically s acked MED plan is schema ized in Fig 1. MED plan s consis mainly o
connec ed elemen s called e ec s ha gene a e simul aneous e apo a ion/condensa ion p ocesses in a
dec easing sequence o p essu es and empe a u es [5,6,7]. The i s e ec has he highe p essu e, an ex e nal
hea sou ce (s eam) makes seawa e boil: The s eam hus gene a ed is used as he hea sou ce o he nex e ec ,
and so on. Each e ec has a p ehea e placed nex o i wi h he aim o inc easing he empe a u e o he eed
seawa e be o e i is in oduced wi hin he i s e ec . Vapou condensed inside each ho izon al ube bundle
om he second o he las e ec s ep esen s mos o he dis illa e p oduc ion o a MED plan . The apou
p oduced in his las e ec is condensed in a inal condense , which is cooled by seawa e . B ine and des illa e
a e hen ex ac ed by pumps.
The 7 h In e na ional Symposium on Design, Ope a ion and Con ol o Chemical P ocesses (PSE ASIA 2016)
[p ep in ]
Fig.1: Schema ic P ocess Diag am o a ypical MED plan
3.2 P essu e Re a ded Osmosis
P essu e e a ded osmosis (PRO) is based on eco e ing he salini y g adien caused by di e ences in he sal
concen a ion be ween seawa e and esh wa e [4]. In a ypical PRO p ocess (p esen ed in Figu e 3), wa e
molecules spon aneously anspo h ough a semi-pe meable memb ane om a low salini y s eam (such as
i e wa e , b ackish o was e wa e ), a ambien p essu e in o a p essu ized high salini y s eam (seawa e o
b ine), wi h he aid o he osmo ic p essu e g adien ac oss he memb ane. The p oduced osmo ic powe is a
p oduc o he ansmemb ane p essu e and wa e pe mea ion a e. This powe is hen con e ed in o elec ici y
by eeding he p essu ized s eam o a hyd o- u bine o used in s anda d ene gy eco e y sys ems [7-9].
Fig.3: Schema ic P ocess Diag am o a PRO sys em.
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4 In eg a ion o P essu e Re a ded Osmosis in o MED desalina ion
The in eg a ion o PRO wi h MED is p esen ed in Figu e 2. The p ocess would ope a e as ollows: he
osmo ic ene gy o he ou le b ine in MED sys em b ine wa e om was ewa e h ough a memb ane (specially
de eloped o PRO p ocesses), gene a ing hyd aulic p essu e; his p essu e is hen ans o med in o elec ici y in
a u bine (i could also be used o assis pumping inside he MED p ocess, by exchanging p essu e using
s anda d hyd aulic ene gy eco e y de ices, bu his possibili y is ou side he scope o his wo k).
F om he a ailable Salini y G adien app oaches, PRO has been selec ed because he high empe a u e o he
b ine imp o es he pe o mance o PRO p ocesses. In ac , b ines a e equen ly cooled down in MED plan s
using seawa e and a hea exchange . As an al e na i e, he was ewa e ha would be used as eed wa e in he
PRO p ocess can be used in he hea exchange , so ha he PRO p ocess ope a es a he bes ope a ing poin o
each speci ic memb ane.
Figu e 2: De ail o he p oposed SED sys em
4.1 E alua ion o Ene gy Reco e y
The nume ical esul s ob ained using models and da a om he li e a u e [5,9] a e summa ized in Table 1. This
main esul s o he ene gy eco e y sys em, ex apola ed om he labo a o y esul s published in [6] by he
au ho s o his p oposal, co espond o he case s udy p esen ed in Figu e 2. To de i e he da a in Table 1, he
MED plan p esen ed in [7] is used as case s udy, in which he a ailable was ewa e low is assumed o be a
leas 125m3/h (wi h a maximum concen a ion o 1 g/l o dissol ed sal s). Fo he ex apola ion o he esul s,
he PRO memb ane pa ame e s gi en in Table 2 a e used, as hey ep esen he cha ac e is ics o memb anes
expec ed o be comme cially a ailable in he yea 2015. To make he esul s gene al, ou di e en
combina ions o con igu a ions o hea exchange s and b ine empe a u es we e es ed (co esponding o case
s udies 1 o 4).
The 7 h In e na ional Symposium on Design, Ope a ion and Con ol o Chemical P ocesses (PSE ASIA 2016)
[p ep in ]
Table 1: Expec ed ene gy eco e ed using he p oposed sys em o di e en seawa e and eed wa e
condi ions.
4.2 Es ima ion o sa ings
The es ima ion o he wa e cos s was ca ied ou s a ing om he cos s in s a e-o - he-a S-MED plan s, which
a e assumed o be 0.240$ pe cubic me e o desalina ed wa e ( o a 2000m3/day plan ope a ing 24 hou s,
hanks o he mal ene gy s o age). The p oposed SED sys em would eco e a signi ican pa o he osmo ic
ene gy o he b ines as elec ical ene gy, which makes i possible o educe he ope a ing cos s. A summa y o
he es ima ion o cos s a e p esen ed in Table 2 o he ou case s udies p esen ed in Table 1.
Table 2: Expec ed wa e cos s using he p oposed SED sys em o di e en ope a ing
condi ions
Case S udy SED Expec ed Cos s ($/m3)
P edic ed Sa ings wi h SED (%)
#1 0.208
5.5%
#2 0.199
9.5%
#3 0.190
13.6%
#4 0.184
16.4%
Case
S udy
MED B ine
concen a ion
PRO B ine
empe a u e
PRO Feed
wa e
empe a u e
Ope a ing
p essu e
Discha ge
concen a ion Powe
eco e ed
#1 65 g/l 40ºC 35ºC 26.0 ba 46.2 g/l 28.8 kW
#2 65 g/l 50ºC 40ºC 26.8 ba 42.3 g/l 33.5 kW
#3 65 g/l 60ºC 40ºC 27.7 ba 41.8 g/l 38.6 kW
#4 65 g/l 60ºC 50ºC 27.7 ba 42.3 g/l 41.4 kW

July 24-27, 2016, Tokyo, Japan
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5 Conclusions
Based on he esul s ob ained by nume ical simula ions, i can be concluded ha :
• The quan i y (714m3/day) and quali y (WHO s anda ds) o he eshwa e p oduced would be adequa e o
he expec ed applica ion.
• The p oposed ene gy eco e y sys em imp o es he ene gy e iciency by eco e ing a signi ican amoun o
he osmo ic ene gy (up o 41 kW), when ope a ing di ec ly wi h he MED b ine (case s udies #3 and #4),
using he s uc u e p esen ed in Figu e 2. D inkable wa e quan i y and quali y would no be a ec ed.
• The discha ge concen a ion o he p oposed sys em has a concen a ion no e y di e en om ha o
seawa e , signi ican ly educing i s en i onmen al impac .
Acknowledgemen s: Pa ly unded by MiCInn DPI2014-54530-R and H2Ocean p ojec
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