Exergy Analysis of Large ME-TVC Desalination System

Transcription

1 Exergy Aalyss f arge ME-V esalat System Awar O. Bamer Water & Eergy Prgram\Research rectrate Kuwat udat fr the Advacemet f Sceces (KAS) he 0 th Gulf Water ferece, -4 Aprl 0, ha- Qatar

2 Outles Itrduct Prcess descrpt hermal aalyss System perfrmace ad mdel valdty Sestvty aalyss cluss.

3 Itrduct * Several ME-V desalat uts have bee stalled recetly mst f the G cutres. * he ttal stalled capacty has creased up t 500 MIG the last decade. 3

4 able: Several prects f ME-V G Year cat utry tal capacty, MIG 99 Jabal haa UAE Umm Al-Nar UAE 7 00 ayyah UAE 0 00 Al-aweelah A UAE Sharah UAE Al-Hdd Bahra Al-Jubal Saud Araba uarah UAE Ras affa Qatar 63 4

5 Graph Sharah 6 ayyah 4 Umm Al-Nar rapa Al-awelah Mrfa Year g. he ut sze capactes f these uts were creased expetally frm t 8.5 MIG a very shrt perd. 5

6 * he ut sze capacty s avalable at 0 MIG, ad t s expected t crease up t 5 MIG the ear future. * he ew tred f cmbg ME-V wth cvetal multeffect ut led t ths crease the ut sze.

7 * mted studes were carred ut ME-V frm exergy pt f vew sce the md f ghtes, but t has bee publshed several wrks recetly. * A mathematcal mdel f ME-V s develped ths study, usg EES Sftware. * hs mdel s used t evaluate the system perfrmace f sme ew cmmercal uts havg capactes f.4, 3.5 ad 6.5 MIG. 7

8 Prcess escrpt g. w detcal ME-V uts are cmbed wth a sgle ME ut. 8

9 hermal aalyss * rst ad Secd aws aalyses are used t develp a mathematcal mdel f the system. * Mass, eergy ad exergy balace s appled t the thermcmpressrs, evapratrs, feed heaters ad ed cdeser. * Assumpts: - Steady state perat, - Neglgble heat lsses t the surrudg, - Equal temperature dfferece acrss effects & feed heaters, - he varats f p & BPE wth the ad salty are eglgble. 9

10 * Eergy balace s appled t each evapratr ME-V uts, rder t fd: B y y f r h h f fd d r s f r B y y )] ) ( ) ( [( 3

11 f r B y y )] ) ( ) ( [( f f B ) ( ) ( f r B y y * Eergy balace s appled t each evapratr ME ut, rder t fd: * he ttal dstllate utput frm all effects s equal t,,...3, 7

12 * Exergy balace s cducted t the therm-cmpressrs, evapratrs, cdeser ad the leavg streams t fd the exergy destruct (I): I S E E 8 ut herm-cmpressr he exergy destruct the therm-cmpressrs I e s h h S S h h S S s d s d r d g d g 9

13 3 f f r e I I B y y I f f r e I B y y I l Effects he exergy destruct the frst, secd ad last effect f f v fd d fd d r s e I S S h h I 0

14 4 deser ad eavg Streams * he exergy destruct the cdeser, c f c f c c M I l c v c v r r I l c v c v f f I l c c B I l * he leavg streams, r,f ad B ca be expressed as:

15 * he heat trasfer area f each effect ca be btaed frm the latet heat f cdesat (thermal lad). 5 e e e A U Q * heat trasfer area fr the st, d ad last effect U h h A d e fd d r s e v e r U y y A ] ) ( ) ( [( ) ( U y y A v e r e

16 System perfrmace * he system perfrmace f the ME-V mdel ca be evaluated terms f : Ga utput rat GOR s Specfc heat csumpt Q d s s Specfc exergy destruct I t I 3 Specfc heat trasfer area At d A e A e A f Ac 4 Specfc exergy csumpt s A h h S S d s fd s fd 6.. 5

17 Mdel Valdty * he valdty f the mdel was tested agast sme avalable data f cmmercal uts havg dfferet capactes: - ABA Bahra.4 MIG, - Umm Al-Nar UAE 3.5 MIG - Al-Jubal KSA 6.5 MIG. * he results shwed gd agreemets 7

18 able : Mdel results agast the actual data. esalat Plat Alba Umm Al-Nar Al-Jubal Number f effects Ut capacty, MIG Oper. & es. Parameters M A M A M A Mtve pressure, bar p bre temperature, NA Mmum bre temperature, NA Mtve steam flw rate, kg/s NA emperature drp per effect, NA System Perfrmace Ga utput rat NA Specfc heat csumpt, kj/kg 348 NA NA Specfc exergy csumpt, kj/kg 7 NA 74 NA 56 NA Specfc heat trasfer area, m /kg/s 44 NA NA Specfc exergy destruct, kj/kg/s 94 NA 54 NA 4 NA

19 Sestvty aalyss * A sestvty aalyss s carred ut t vestgate the system perfrmace varats f Al-Jubal ut. * hs prect belgs t Marafq mpay ad t s curretly csdered as the largest ME-V plats the wrld, (76 MIG). 9

20 g. 3 Schematc agram f Al-Jubal ME-V ut 0

21 kg/s s r Mtve steam, kg/s g. 4 he effect f mtve steam the dstllate prduct frm the effects.

22 Ga utput rat, GOR GOR MIG stllate prduct, MIG p bre temperature, g.5 he effect f the dstllate prduct ad ga rat.

23 Specfc heat csumpt, Q d kj/kg Q d A d Specfc exergy csumpt, A d kj/kg p bre temperature, 50 g.6 he effect f the specfc heat ad specfc exergy csumpt.

24 900 Specfc heat trasfer area, m /kg/s = 65 = 63 = emperature drp per effect, g.7 he effect f Δ the specfc heat trasfer area at dfferet

25 60 Specfc exergy csumpt, A d kj/kg ABA, =4 Umm Al-Nar, =6 Al-Jubal, = p bre temperature, g.8 he effect f the specfc exergy destruct fr dfferet uts

26 deser 0% eavg streams 6% A-Jubal, 6.5 MIG hermcmpressr 0% Effects 64% g.9 he ma exergy destructs Al-Jubal Ut. herm-cmpressrs ad effects are the ma surces f exergy destruct 6

27 4 th effect 3% ABA 3 rd effect 9% st effect 48% g. 0 he exergy destruct dstrbut the effects. d effect 0% 6th effect % 5th effect % Umm Al-Nar st effect 36% 4th effect % 3rd effect 4% 6 th effect 9% 7 th effect 9% d effect 5% 8 th effect 9% Al- Jubal st effect 3% 5 th effect 0% 4 th effect 0% 3 rd effect % d effect %

28 .5.0 Ras affa 0.5 Ga Output Rat Al-Jubal uarah Al-Hdd 8.5 Sharah Year g. he crease f ga rats the ew prects. 8

29 able 3. Mst ME-V uts perated by PP the ew prects. Plat ABA Umm Al-NAR Al-JUBAI Al-uarah utry Bahra UAE KSA UAE Year f cmmss Surce f steam Bler G-S/HRSG G-S/HRSG G-S/HRSG ype f fuel esel l Natural gas Natural gas Natural gas Pwer apacty, MW esalat ME-V ME-V ME-V ME-V/RO Ut capacty, MIG /RO Number f uts 4 7 /RO tal capacty, MIG Number f effects Water cst, US $/m 3 NA NA Hybrd desalat system s trduced Al-uarah prect ( large ME-V uts f 8.5 MIG wth RO). 9

30 .6.4 Ras Al-Khamah Water cst, US $/m Al-Jubal Al-uarah 0.6 Al-awelah A Year g. he decrease the water cst the last decade (ME-V). 30

31 cluss * he ew tred f cmbg ME-V ut wth a cvetal ME ut has bee used lately several large prects. hs tred prvdes a apprach t crease the ut capacty wth a mre cmpact desg. * Exergy aalyss shws that the specfc exergy destruct ABA ut s almst twce that Umm Al-Nar ad Al-Jubal uts because hgh mtve pressure s used ABA cmpared t lw mtve pressure ther uts. * he aalyss dcates that therm-cmpressrs ad the effects are the ma surces f exergy destruct these uts. * he frst effect f Al-Jubal was fud t be respsble fr abut 3% f the ttal effects exergy destruct cmpared t 48% ABA ad 36% Umm Al-Nar. 3

32 * he specfc exergy destruct ca be reduced by creasg the umber f effects as well as wrkg at lwer tp bre temperatures. * he maufacturer tred t crease the umber f effects gradually (4, 6, 8, etc.) rder t crease the sze f the uts a cmpact desg * Mst f the ew ME-V uts are cmmly perated wth large cmbed cycle pwer plats rder t reduce the pwer ad water cst. 3

33 HANK YOU 33