Single and dual purpose nuclear desalination

Transcription

1 See discussions, stats, and autho pofiles fo this publication at: Single and dual pupose nuclea desalination Confeence Pape Apil DOI:.9/INREC Souce: IEEE Xploe CIAION READS 6 autho: M. Ragheb Univesity of Illinois, Ubana-Champaign 3 PUBLICAIONS 5 CIAIONS SEE PROFILE All content following this page was uploaded by M. Ragheb on 4 Septembe 4. he use has equested enhancement of the downloaded file.

2 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, SINGLE AND DUAL PURPOSE NUCLEAR DESALINAION Magdi Ragheb Depatment of Nuclea, Plasma and Radiological Engineeing Univesity of Illinois at Ubana-Champaign, 6 albot Laboatoy, 4 South Wight Steet, Ubana, Illinois 68, USA. magheb@illinois.edu ABSRAC he use of single pupose wate poduction and dual pupose electicity and wate poduction plants is discussed. An expession fo the combined wate and electical poduction is deived. he total cycle efficiency appeas as a sum of the electical poduction efficiency and the wate poduction efficiency weighted by the atio of the absolute heat addition tempeatue to the wate cycle to the absolute heat addition tempeatue to the electical cycle. he undelying themodynamic consideations eveal that the wate poduction and electicity poduction pocesses ae competitive athe than complementay pocesses fom the oveall cycle s efficiency pespective. Impoving the wate poduction pocess would be at the expense of the electical poduction pocess, and vice vesa. It follows that a dual pupose plant ejecting heat fom the electical poduction pocess to a wate plant would not necessaily be moe efficient than a single pupose wate poduction plant. his suggests the need fo a close consideation of the needed wate electicity mix fo such plants at the design stage to accommodate diffeent situations.. INRODUCION he fesh wate industy is the thid lagest industy in the wold valued at $3x 9 pe yea by the UK ade and Investment Ministy. Accoding to Fed Peace, New Scientist news edito and autho of: When the Rives Run Dy, : A typical meat-eating, milk-guzzling Westene consumes as much as a hunded times thei own weight in wate evey day. hat is because it takes, tonnes of wate to gow tonne of wheat,,-5, lites of wate to gow one kilogam of ice,, lites to gow the feed fo a cow fo a ¼ pound hambuge, 5 cups of wate fo a teaspoon of suga and 4 lites of wate to poduce one cup of coffee. he wold today gows twice as much food as it did in the 96s but uses thee times as much fesh wate to gow it. wothids of all the wate taken fom the envionment is used in cops iigation. Fed Peace suggests: his is massively unsustainable, and has led many people to conclude that the apocalypse was not aveted, only postponed.. VIRUAL WAER he oveuse of fesh wate does not just apply to food poduction, but also to industial poduction. Evey -shit takes 5 bathtubs of wate to poduce and evey small automobile uses 45, lites. By consuming impoted goods fom othe counties, people ae exploiting ives of fesh wate fom acoss the wold. Wate used fo gowing food and making poducts is designated as vitual wate. ony Allan of the School of Oiental and Afican Studies in London, invented the tem vitual wate. he global vitual wate tade is estimated at aound, cubic kilometes a yea, o Nile Rives flow. wo thids of it is used is in cop poduction, /4 in meat and daiy poducts, and / in industial poduction. he lagest net expote of vitual wate is the USA, which expots in gain and meat aound /3 of all the wate it takes fom the envionment. Canada, Austalia, Agentina and hailand ae similaly net expotes. Impotes of vitual wate, like Japan and the Euopean Union (EU), ae not shot of wate. Fo othes like Ian, Egypt and Algeia, it is a vital impot. Jodan impots 8-9 pecent of its wate in the fom of food []. 3. GLOBAL WAER SHORAGE Accoding to Juliette Jowit of he Obseve: Rainy egions like the Bitish Isles have not escaped a woldwide dought phenomenon. he city of London's long tem aveage ainfall has dopped below that of the cities of Istanbul, Dallas and Naiobi. he UK govenment consideed poposals to intoduce dought odes banning non-essential use of wate. Austalia suffes fom a sevee dought as well. India's wate table is at an all-time low and dopping fast. In some aeas, it has fallen fom to 85 feet below gound level in the last decade. China is suffeing fom annual doughts, with the city of Beijing besieged by sand stoms blowing down fom the eve expanding Gobi Deset. he southwesten USA is stuggling to find enough wate fo its gowing population. Califonia and Nevada ae being paticulaly had hit, and the shotage is getting wose. Rives ae unning dy acoss the wold, fom the Rio Gande in exas to India and Nothen Nigeia. he Aal Sea in cental Asia, whee a thiving fishing industy died as the ives inflow into the sea was dained to feed cotton fams, has shunk in size and the population on its shoe is poisoned by dust stoms of salt and esidual agicultual chemicals. Govenments who concentate on building dams and daining subteanean aquifes need to look fo altenatives. Cops can be INREC-

3 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, gown with a quate of the wate cuently used using methods such as dip iigation and the lining of wateways to avet wate seepage. Most people do not pay an economic pice fo wate because govenment subsidies keep pices atificially low. Without a pice incentive, they would not cut back on thei usage. he wold's wate pipes ae cumbling whee much of the wate supply leaks into the gound befoe eaching the consumes necessitating epai and eplacement. 4. FRESH WAER RADE hee ae counties that have an ove-abundance of wate with oppotunities fo sale to othe counties. Canada has the same amount of wate as China, but just.3 pecent of its population. Bazil has fa less need of its wate than many of its neighbos. As the value of wate ises, counties like these could conside expoting thei spae eseves to those moe in need and willing to pay. Pipelines ae spinging up, connecting states and counties. ankes may in the futue tanspot wate acoss the sea as often as they do petoleum. he shaping and tugging icebegs fom Antactica to deset aeas of the Middle East has been consideed. Fesh wate is on the move acoss the globe. ukey expots wate to Isael and Cypus in lage floating balloons that can hold up to five million gallons of wate. Singapoe buys pecent of its wate fom pivate secto supplies who have built desalination plants in ode to educe its eliance on Malaysia. Companies in Scandinavia ae investigating the ways in which they can pofit fom thei watey landscapes, such as one company that is consideing the shipping of the equivalent of, Olympic swimming pools of wate to Ian pe day. 5. HE DESALINAION ALERNAIVE In Southen Euope and othe aid egions of the wold, altenatives, such as desalination, ae set fo sustainable gowth. Southen Spain's Andalucía, one of Euope's most aid egions, is also the continent's most poductive agicultual aea. Intensive iigation has seiously depleted its fesh wate esouces. he city of Almeia collects and ecycles all of its wate, using it fo agicultue. he newly ceated Pogama Agua will supply desalinization facilities all along the Mediteanean coast. his is an altenative that has long been consideed too expensive, but that state of affais is changing. Lage amounts of powe ae needed to dive the pumps and the unit costs ae coming down. he taditional playes have been in the Middle East, such as Saudi Aabia, Kuwait, Dubai, and island communities. Malta and the Canaies Islands have been using desalination fo 4-5 decades because it has been thei only souce of wate. Big cities ae beginning to conside it seiously. he city of Peth in Austalia has given the go-ahead fo a lage desalination plant. New wate quality standads ae being put in place in counties such as China and India, which will dive majo new investments in fesh wate poduction, infastuctue, teatment and puification. 6. JUSIFICAION Single pupose wate poduction plants and dual pupose electical and fesh wate poduction plants using nuclea, wind, sola o fossil souces could augment the available wate supplies in aid egions of the wold adjacent to sea shoes, wheneve long distance conveyance of wate is not possible, fo engineeing, economical, o political easons. Fesh wate is inceasingly conceived as the most pecious global esouce fo this centuy, ahead of petoleum, mineals and foests []. As the wold s population gows, the stain on the constant fesh wate supply is inceasing ceating souces of conflict that can be avoided though supply augmentation, in addition to euse and consevation. he need fo fesh wate is accentuated by the inceasing salinization poblems in iigated egions of the wold, tuning fetile agicultual land into salty desets. he poduced electicity would be used fo the pumping of dainage wate and educing the height of the wate table below the citical depth of two metes, educing the salinity level and poviding inceased wate development. Along sea shoes hydogen can be poduced though high tempeatue wate electolysis to be pumped inland poviding electicity fom fuel cells and concuently fesh wate fom the pocess [3. 4]. In the aid egions of the wold, electical poduction plants can be used inland fo the teatment of backish undegound wate supplies using electo dialysis o evese osmosis. Along sea shoes, distillation methods can be used fo the poduction of lage amounts of fesh wate to be used locally o to be pumped inland. Unde consideation, dual pupose plants ae favoed on the tacit assumption that it may be advantageous to be use the heat ejection fom the electical poduction pocess as a souce of lowe gade heat to the desalination pocess [5]. Afte all, the desalination pocess equies low tempeatue opeation to avoid pecipitation of salts at high tempeatue leading to fouling and scaling of the heat tansfe sufaces, as well as clogging of the piping. he dual electicity and fesh wate poduction appoach faces the hudle of poducing lage blocks of electical powe to elatively small gids that could not accommodate them, and to locations whee fesh wate supplies ae needed moe ugently than electical supplies [6-8]. he use of ago industial complexes has been suggested as a means of using the lage blocks of electical powe poduced by the dual pupose plants [9]. he altenative of single pupose plants poducing pimaily fesh wate with a smalle electical component satisfying the plant and local needs is consideed hee/ 7. HERMODYNAMIC CONSIDERAIONS Let us conside the absolute tempeatue = 73 + o C against entopy S diagam modeling a heat addition Q A to an electical poduction model poducing electical enegy in the amount (Fig. ): W = ( ) S () E INREC-

4 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, whee: is the heat addition tempeatue, is the heat ejection tempeatue to the wate cycle, S is the change in entopy. Conside that the electical cycle ejects its heat QR to a wate poduction cycle at the tempeatue. he wok done in the wate cycle would be: whee: W = ( ) S () W is the heat ejection tempeatue to the envionment. he combined electical and wate poduction cycle has a total wok as: Wotal = WE + WW = ( ) S + ( ) S = ( ) S he heat addition to the cycle is: A (3) Q = S (4) he heat ejection fom the combined cycle is: Q = S (5) R he heat ejection fom the electical cycle to the wate cycle can be expessed as: QR ' = S (6) Expessions fo the total cycle efficiency, electical cycle efficiency and the wate cycle efficiency can be witten. he total efficiency is: W ( ) S ( ) W W = = = Q S R ' he goal is to find the elationship between the thee cycle efficiencies. Stating fom Eqn. 7 and substituting fom Eqn. 3 one gets: otal W ( ) S + ( ) S ( ) otal = = = Q S his can be ewitten as: otal A ( ) + ( ) = (9) ( ) ( ), = + Substituting fom Eqns. 8 and 9 yields: whee: = + otal E W = + E =. W () () his suggests that the combined cycle efficiency is equal to the electical cycle efficiency plus the wate cycle efficiency weighed by the facto which the atio of the tempeatue at which the tempeatue at which heat is added to the wate cycle to the tempeatue at which the heat is added to the electical cycle able and Fig. show the vaiation of the wate, electicity and oveall efficiencies fo diffeent tansition tempeatues. 8. LIMIING CASES he facto can vay ove the ange: otal W ( ) S ( ) otal = = = Q S A (7) < < () he electical cycle efficiency is: W ( ) S ( ) E E = = = Q S A he wate cycle efficiency is: (8) Since vaies fom an uppe limit of to a lowe limit of, the uppe limit of is unity, and its lowe limit is equal to the atio of the tempeatue of heat ejection to the envionment to the heat input to the cycle. his suggests a ange of choices in tems of the elative magnitudes of the wate poduction and electicity poduction pocesses. hei exteme cases lead to exclusive wate poduction o exclusive electicity poduction pocesses. INREC-3

5 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, able. Vaiation of the wate, electicity and oveall efficiencies fo diffeent tansition tempeatues,. = 73 + =93 K, = = 593 K. ansition empeatue [K] Wate Efficiency W = Electical Efficiency E = = otal Efficiency otal = Heat Addition QA.8 WE S Heat Rejection QR Efficiencies,.7.6 Ww.5 otal efficiency Heat Rejection QR.4.3 Wate efficiency. ΔS S. Electical Efficiency ansition empeatute [ok] Figue. Single and dual pupose desalination plants Canot Cycle efficiencies absolute tempeatue vesus entopy S diagam. Figue. Wate, electical and total efficiencies and facto as a function of the tansition tempeatue INREC-4

6 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, In pactice, opeation will be at some intemediate value. Howeve it can be noticed that the wate poduction and electical poduction pocesses ae competitive athe than complementay. If one decides to poduce a highe popotion of wate, it is at the expense in tems of enegy expenditue of the electical pocess, and vice vesa. 9. SINGLE PURPOSE WAER CYCLE aking the limit whee = and consequently = yields by substitution in Eqn. and compaison with Eqn. 9: otal ( ) ( ) = + = = ( ), W his suggests a single pupose wate poduction pocess.. SINGLE PURPOSE ELECRICAL CYCLE () aking the limit whee = and consequently = / yields by substitution in Eqn. and compaison with Eqn. 8: pocess. otal ( ) ( ) = + = = ( ), E (3) his suggests a single pupose electicity poduction. WAER AND ELECRICIY MIX An attempt at a close examination of the fesh wate and electicity poduction mix unde diffeent situations is tied. Using Eqns.,, the wate to electicity wok atio can be expessed as: WE W S w ( ) ( ) = = =, S WE ( ) S ( ) Dividing into and using the definition of, yields: whee: ( ) WE = = ( ) =. (4) able and Fig. 3 show values of the wate to electicity poduction atio WE as a function of. Similaly define the electicity to wate poduction atio is: EW WE ( ) S ( ) = = =, S WW ( ) S ( ) ( ) EW = = = ( ) WE (5) able 3 and Fig. 4 show values of the electicity to wate poduction atio as a function of. wo limiting conditions can be noticed hee. If =, =, then EW = fo a dedicated wate geneation pocess. On the othe hand if =, WE = fo a dedicated electical poduction pocess. It can be obseved that the wate to electicity atio WE inceases abuptly as appoaches, o as appoaches unity, coesponding to a situation of a single pupose plant that pimaily poduces fesh wate. A low value of / implies a plant opeating at faily low tempeatue, wheeas a lage value of / coesponds to a plant opeating at high tempeatue. Since the ejection tempeatue is fixed by envionmental consideations, a limitation exists on the feedom of inceasing. o incease the wate to electicity atio WE fo a given heat addition tempeatue, one must incease, up to the point whee = / appoaches unity. Fo instance, at a dedicated plant poducing pimaily wate with / =.5 the wate to electicity poduction atio WE can each a value of 74 when =.99.. DISCUSSION he themodynamic analysis shows that it is not necessay to conside dual pupose desalination plants solely based on the intuitive notion that such an appoach would be themodynamically efficient though using the waste heat ejection fom plants pimaily designed to poduce electicity and conveniently attaching to thei back end wate desalination plants. Instead, the plant must be designed accoding to the elative needs of wate to electicity. INREC-5

7 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, able. Wate to electicity atio WE as a function of = / fo diffeent values of /. = Wate to electicity atio WE =.5 =.5 =.75 = Wate to electicity atio WE /= /=.5 /= = / he wate poduction pocess and the electicity poduction pocess ae themodynamically competitive athe than complementay fom a Canot cycle efficiency pespective. As the wate cycle s efficiency inceases, the electical cycle s efficiency deceases; and vice vesa. Highe efficiencies of eithe pocess can be attained by ejecting the heat at the same ambient tempeatue. his suggests the need fo a close examination of the wate and electicity poduction mix at the design stage of both the powe souce such as a nuclea eacto, and the chosen desalination plant []. A desalination plant cannot just be fitted to the existing design of a powe souce (Fig. 5). Consideing expeience based upon opeating nuclea powe plants limits the tansition tempeatue to 5 o F. Fo electicity poduction, the heat ejection tempeatue cannot appoach geatly lowe sink tempeatues without an incease in cost associated with adding additional tubine stages. Similaly, inceasing the wate poduction efficiency by deceasing would equie an inceasing numbe of desalination stages. In ode to contol scale fomation in the distillation pocess the bine tempeatue will be based on the pessue unde which the distillation pocess eceives the pocess steam fom the eacto. his pessue anges fom.37 MPa to 4. kpa. Figue 3. Wate to electicity atio WE as a function of fo diffeent values of /. INREC-6

8 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, able 3. Wate to electicity atio WE and electicity to wate atio as a function of = / fo / =.5. = Wate to electicity atio WE = Electicity to wate atio EW = WE and EW atios WE, Wate to electicity atio EW, Electicity to wate atio = / Figue 4. Wate to electicity atio WE and electicity to wate atio EW as a function of = /, fo / =.5. INREC-7

9 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, Nuclea plant Steam supply 965 psia 54 o F 37 MW Condensing tubine Sea wate inlet and 36 MW Back-pessue tubine Retun condensate Multistage Flash Evapoatos 5 x 6 gpd Fesh wate poduct Sea wate inlet and bine Figue 5. Configuation of dual pupose plant with an electical powe only section with a condensing tubine and an electical and wate section with a backpessue tubine. 35 o F Nuclea Reacto, MWth 9 o F Bine Heate 7 o F Ven 85 o F Condense Section Evapoato section Rejection to sea Vent Sea wate intake, 6 o F Fesh wate poduct x 6 gpd Makeup wate Bine to sea Figue 6. Low tempeatue single pupose poducing x 6 gpd of fesh wate. INREC-8

10 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, able 4. echnical chaacteistics of a single pupose nuclea desalination plant []. Nuclea Island Desalinatiom Island Powe,3 MWth Wate poduction x 6 gpd Fuel Natual U, UO Evapoatos Contolled flash evapoation Cladding Al Numbe of evapoatos 8 Modeato/coolant D O Vetical stages pe evapoato Aveage fuel bunup 6. MWd/tonne U Numbe of bine heates 4 Coe fuel inventoy 4 t UO Heat tansfe suface pe 63,5 ft bine heat exchange Reacto vessel mateial Al Pefomance atio 4.76 lbs wate/, BU Vessel height 37 ft Evapoato height 4 ft Vessel diamete 37 ft Evapoato width ft Vessel thickness.5 in Evapoato length.5 in Coe height ft Evapoato mateial Coppe-Nickel Coe diamete ft Coolant flow 7.8 x 3 gpm Pimay coolant pumps 4 Sea wate intake 6 o F tempeatue Coe inlet tempeatue 85 o F Bine heate outlet 9 o F tempeatue Coe outlet tempeatue 35 o F Bine heate inlet 7 o F tempeatue Modeato inventoy.33x 6 lb Coolant loss 6, lb/y Nuclea Plant 7,5 MWth Compesso Back pessue tubine 35 psia Geneato Vapo Compesso Evapoato Exhaust Steam Evapoato High empeatue Electolyze H Fuel cells Sea wate inlet and bine exhaust lines Fesh wate poduct.75x 9 gpd Electicity Figue 7. High tempeatue single pupose desalination plant configuation. INREC-9

11 Poceedings of the st Intenational Nuclea and Renewable Enegy Confeence (INREC), Amman, Jodan, Mach -4, able 4 and Figs. 6 and show the configuations and technical specification of single pupose low tempeatue [] and high tempeatue plants [] designed fo specific applications opeating at low tempeatues and pessues and offeing an even geate level of opeational safety than high tempeatues electical poduction plants may be built with local simple technology and human esouces. hese would also povide ease of siting and constuction using indigenous mateials, while poviding needed fesh wate supplies and insuing the safety of the geneal population and envionment.. REFERENCES [] M. Ragheb, K. oukan, and R. A. Al Weshah, Desalination using Advanced design Nuclea Powe Plants, Poceedings of the Intenational Symposium on Wate Resouces in the Middle East: Policy and Institutional Aspects, Ubana, Illinois, pp. 73-8, 993. [] M. Ragheb and A. Siddique, Single Pupose and Dual Pupose Nuclea Desalination Plants, Poceedings IXth Wold Wate Congess Confeence of the Intenational Wate Resouces Association (IWRA), Monteal, Canada, Septembe -6, 997. [3] M. Ragheb and A. Siddique, hemal and Electical Desalination using Fusion Cycles, 6 th IEEE/NPPS Symposium on Fusion Engineeing, Champaign, Illinois, Sept. 3-Oct. 5, 995. [4] M. Ragheb and A. Siddique, hemodynamic Cycle efficiencies of Single Pupose and Dual Pupose Nuclea Desalination Plants, Fist SS/ASA Intenational Confeence on echnology Paks and ansfe of Knowledge, unis, unisia, July -4, 996. [5] R. W. Schleiche and C. J. Hamilton, Exploiting the Nuclea Option fo both Electicity and Wate, Ameican Powe Confeence 53 d Annual Meeting, Chicago, Illinois, Apil 9- Mayst, 99. [6] S. Postel, Last Oasis: Facing Wate Scacity, he Woldwatch Envionmental Alet Seies, W. W. Noton and Company, New Yok, London, 99. [7] J. Kupitz, Nuclea Enegy fo Seawate Desalination: Updating the Recod, IAEA Bulletin,, pp. -4, 995. [8] Gace M. Uows, Nuclea Enegy fo Desalting, USAEC, Division of echnical Infomation, 967. [9] R. Philip Hammond, Nuclea Desalting fo Agicultual Wate, Nucleonics, Vol. 3, No. 9, pp. 5-55, Sept [] Fedeick E. Ceve, he Pospects fo Dual-Pupose Plants, Nucleonics, Vol. 3. No.9, pp.44-47, Sept [] S. Baon and M. Zizza, Why Not Single-Pupose Reactos fo Desalting?, Nucleonics, Vol. 3. No.9, pp.48-5, Sept [] B. A. Gabaaev, Yu. N. Kuznetzov, A. A. Romenkov, Yu. A. Mishanina, Nuclea Desalination Complex with VK-3 Boiling-ype Reacto Facility, Wold Nuclea association, Annual Symposium, 4. INREC- View publication stats