Document KRvnQgRMZwx2gnQ11DwMpBY4Q

i--(jHH-i 1 fimat uttou.. I tSofwi jMjno ivxsm """"----`--^rfiSr-------- | I (--------- ;------------- -^-h7-- FttPwtttr fittfft Va/ 0 "/ prei* taeftr ttttiaiit +/o Q* Fit*, Ifiptr fir H - $rt*m tnlfitlfiJti 01* P* to P- Mtafitft fftllrrt, fin ___i'dzpjjBij** L,,, KL4iJim._____ _____ ___| r _______ t I, I __________* I r -njusjas*------------ 1 , I | HUawnuo riMfaiueiii____ >J I i! sms* 'ms.___ I ,[ KbH ,!1 'fWa* Sr* j#r 1 I i i !" ifcs4* \^V\ i i I8S M- Comparison of Alternate Schemes of Single and Double Reheating Cycles IKyUMvi Turbine-Generator Wllh Ftght SUges ol reed Heating ABCOE w'piiiittft, p*- ........... 11!!!!!!!'!!!!!!' 1!! 1!!!! 1! ^^Si^iAcopjlitePt, tM reheat potnCi ...............................*$&*"*'............................................................ vM*i^ ^ ........................................................................ 'fwtQg^V^ **wn' <on*f,,lo," Thal point) MPteOlire. P*-.................................................................................. yTemp*"*** f :........................................ t)Jj&VJdetkod of reheating.............................. ............................................... tsES&m !"'. ....................................... ................ taa** f ........... ....................................... *rtutor unit h.t Bln p kwhr....................................... BiliDii'iDjliiiiT. *;...................................................................... s^rAuxitorv power demand, kw. . .. ....................................................... Ll''W*ted net *UHon hM> r,la Bin per kwhr..................................... VRedwlion (a net iUUoa heal rate compered to Plan A, Btu pto kwhr. wlpiit, kw......................*................................................. &loid fietor, %........................................................................................... ^Operating hoon pt yi............................... ...................................... wEjtfieiVtf annual dollar laving compand to Plan A............................ k > 'Casltellitd annual saving* al 15%.......................................................... 8400 1050 2400 2400 1050 . 1050 9400 1050 9400 1050 405 487 1000 1000 Boilti Sodiumftm hast xchsn|t ____ --__ 720 1000 Boiler ^ 780 760 1000 1000 Boiler Sodium* ftm heel exchanger 825 1000 Boiler 938 1000 Sodium* rtm heal exchanger 838 1000 Sodium* itm heel exchanger 1.5 S08 7,502 88 7,000 9,167 0 93,000 1.5 508 7,462 88 7,000 9,118 49 93,000 1.5 508 7,293 88 7,000 8,911 956 93,000 1.5 508 7,956 88 7,000 8,866 301 93,000 1.5 508 7,916 88 7,000 8,817 350 93,000 70 8,760 0 0 70 6,760 $11,200 $74,500 70 8,760 $58,300 $388,000 70 8,760 $68,600 $457,000 70 8,760 $79,800 $531,000 msTt (miti r*a i r^jT-^r^T nsTi rsrrr im> rr^tm >* .ks-j k=J k=A k-J r,iLrfS_/Jo L_J. 1__ 4LL------iF^iaao ia* jsxi tsar tear ,s4r Mw ' PLAN 0, DOUBLE REHEAT CYCLE uses the liquid metal, sodium, os heot carrier to reiuperheot steom ot the second reheol point In the turbine circuit- Despite the Increased investment.*^ oddod equipment this cycle may provo o practical postb&t ei.T^.'Fgr lb* single-reheat cycles, A onrl B, EL'iurbiae section efficiencies were ae* molten sodium. From the boiler .the 1200-F sodium flows to the steam ro- r?'Mntd at 85% for first section and 90% superheater, a simple single-pass tube- f^far^the second. For the doublc-reficat. and-shell counterffow unit. For this ... jfJVcjclei'C, D and , the first section was particular application where the sodium- Double Reheat Cycles--the Next Step?] SSaHS stenm heat exchanger is designed for a team-pressure drop of 5 psi, the unit would be about 4 ft in diameter and 20 A* Excises. Feedwater temperature was as- ft long. Rising fuel costs and metallurgtcal limitations led - the swing to reheat cycles. In the drive for more economy the double reheat cycles offer en couraging future possibilities By R H SHANNON United engineers 4 Comtrvctori Inc ond J D SELBY General (Itetrle Company The reheat cycle now used la power plants (1)' increases plant thermal efficiency (2) reduces turbine main* tenonce by lessening moisture in exhaustteam. Using two atages of reheating, instead of one as at present, offers prac tical possibilities of further raising plant thermal efficiency. Instead of piping steam back to the boiler for reheating, a heat-carrying fluid may be used. A liquid metal like odium may circulate between a heater in the boiler gas pass and an exchanger near the turbine where steam emerges for reheating. With the sodlum-steom heat exchanger near the turbine it is proctica! to design for a steam-pressure drop of 5% of reheat pressure leaving the turbine. Study. In life table, op|>oiile page, it has been assumed that norma) re heating In. the boiler causes a pressure drop of 10% of reheat pressure, wWk the heat-exchanger scheme involves ar^ 5% steam-pressure drop. This aeeouidi for the difference in station heat rsto for Flan A va 0, and Plan C vs D vi'lj Al! the plans are baaed on a 100,000* unit with eight stages of feedwater heifr ing. Heat balance for Plan D is |f** in the circuit diagram above. Note'tw* Flan E would use the liquid sodhtfi system at both reheol points. The sodium circuit includes: sodia^, steam heat exchanger, pumps, pipW and valvce, surge and storage totC! purifying equipment, gas pressurUW- apparatus, system healing unha, eqw^ menl for filling system. In addition, *$, emergency heat exchanger allows sodium system to dissipate heat durbfj transient periods of startup ond down and when turbine steam topPitj suddenly ceases. -Ti 508 F for all plans. $While (_h_e_r_e w__o_u_l_d_a_c__tu,,awlly,, sbme all .'difference in auxiliary power needs (or the demand was assumed as fj0!jkw for all. Turbine-shaft glond \*njKvale-leam leakage were taken as y,ro.lhroughout. Water compression ef- . feedwoter was neglected for all fc'$w^'not (feeling the comparisons. Sodium System. In the dieopposite page, soditim enters the Seating section at 900 F and al *200 K. Sodium has favori^f-^orsctaristic, 0s a heat-tranaler j/: : Local heat-transfer coefficients *ube wall and* sodium, equal Btu per hr sq ft per F or greater, ?'!fci**lily och*0?d. Little difficulty p|*~?be experienced in limitimx holler?-T****iS^nfi*'**-*^ teml'eral|,fes to 100 F abovB temperature. ?lr`(uSaf electTomagnetic-lype ^ Mu^d he used for moving the The two pumps would each have a capacity of about #90,000 lb per hr with 100-ft tdh. This provides 100% standby capacity. For electromagnetic pumps about 100 hp at full rating would be needed. Centrifugal pumps need 80 hp or lest. All piping and equipment in the sodium system for superheated steam reheating would be stainless steel. Since sodium reacts with oxygen, a nitrogen pressurixine blanketing system is needed. The sodium-system purify ing, filling and heoling equipment are needed only for initial startups or after prolonged shutdown. Estimated installed cost of the liquidsodium system, including cost ol the Ini tio! sodium charge, is obout $300,000. Economic Evaluation. Corresponding to the heat rotes-shown in table abovo, och cycle has the following thermal efficiency: ,4--37.2%. 0--37.45%. C-- 38J%, D--38.5%, E--38.7%. Table ENOINEERINO AND MANAGEMENT SECTION 1`^MT 1933 PO* J ENGINEERING ANO MANAGEMENT SECTION gives the reduction in heat rate (or each plan or cycle referred to A as the base. These reductions were evaluated as fol lows: 1. Estimated load factor m 70% 2. Fuel cost 40c per million Btu 3. Fixed charges covering amortiza tion, interest, taxes, insurance -- 15% 4. Period hours per year correspond ing to load factor of 70% ~ 8,760 5. Estimated annua) dollar saving -- (Btu per kwhr reduction) (net kw sta tion output) (hr per year) (lead fac tor) (fuel eost per Bto) 6. Capitalized value of ` saving (Estimated annual dollar savlng)/0.15 Example As an example the saving for Plan B over A is 49 Btu per kwhr. then the an nual dollar saving 49x93,000x8760x 0.7x0.4/10* -- $11,200. Then capitalized value of saving -- $11,200/0.15 -- $74,500. The more-developed plans seem to in dicate an adequate margin for any addi tional costs that might be involved bye slightly more.complex turbine structure for the seeond reheat point. This cycle might be a practical answer to what can be done to fight inflationary fuel costs, while steam temperatures are limited.'