Regulating Characteristics Analysis of Boiler Feed-water Pump when 600MW Unit Sliding-pressure Operating

Transcription

1 Aalable onlne at Energy rocea 7 (0 ) Internatonal Conference on Future Electrcal ower an Energy Systems Regulatng Characterstcs Analyss of Boler Fee-water ump when 600MW Unt Slng-pressure Operatng u S-ke Gao u-fenja Xue-jng School of Energy Resources an Mechancal Engneerng Northeast Danl Unersty Jln Cty Chna Abstract Accorng to the characterstcs of utlty-type generator set n arable loa slng-pressure operaton the paper comprehensely analyzes the features of fee-water system n whch arable-spee man fee-water an power freuency booster-pump connect frst n seres an then n parallel. It puts emphass on fttng characterstcs euaton of fee-water pump uner fferent operatons etermnng characterstcs of fee-water ppelne uner slng-pressure operaton corresponng resstance coeffcent an fnally eucng the euaton of lft effcency an rotatng spee when fferent loas an fferent slng-pressures are aapte only by man fee-water pump arable spee ajustng. It takes one power plant 600MW supercrtcal unt for example to compare the energy consumpton of fferent operaton moes an thus puts forwar a more sutable operaton moe uner fferent loas prong theoretcal bass for the practcal applcaton of project. 0 0 ublshe by by Elseer Lt. Lt. Selecton an/or an/or peer-reew uner uner responsblty of anan of [name Unersty. organzer] Open access uner CC BY-NC-ND lcense. Keywors:supercrtcal unt;slng-pressure operaton; fee-water system; pump n seres or parallel; energy consumpton analyss. reface In ew of the current natonal energy polces an the "encouragng great generators shuttng own small generators " ecson as for large thermal power plants wth the ncrease of unt capacty an operatng parameters of boler fee-water pump the absolute amount of energy consumpton s ncreasng as well so the problem of energy sang s partcularly mportant. Although usng slng-pressure operaton wth the aryng loa unts has been wely use yet the operaton of the boler fee-water pump wll be more complex compare to constant-pressure. That s because to meet the nee of pumpng ant-cataton boler water supply system generally aopts the form of connectng steam-ren ngot an electrc fore pump frst n seres an then n parallel. oweer currently there are relately many lteratures on thermal effcency of unts aoptng slp pressure operaton but not many on the operaton wth ublshe by Elseer Lt. Selecton an/or peer-reew uner responsblty of anan Unersty. Open access uner CC BY-NC-ND lcense. o:0.06/j.egypro.0.0.

2 5 u S-ke et al. / Energy rocea 7 ( 0 ) 5 60 fee-water pumps n seres an then parallel an een less for the stuaton that the fore pump aopts freuency spee an only man fee-water pump runs at arable spee to ajust the water loa[]. To ths en ths artcle acaemcally analyzes a seres of contons of boler water supply system through fferent loas an slng own when usng fferent operatng moes whch ams to proe theoretcal bass for a more economc an reasonable operaton n projects. Fgure. rncple water supply system agram of large sets boler;eaerator; electrc power freuency fore pump; ngot-ren arable spee man pump; 5calorfer ;6steam turbne.the relatonshp Between loa Changes an Slng-pressure Operaton Fgure an Fgure respectely ges the prncple water supply system of a 600 MW supercrtcal unt of a power an ts hybr operaton cure n whch t between 90% an 0% of the loa s the slng-pressure operaton. The so-calle slng-pressure operaton refers to the process of ajustng the boler outlet pressure when the turbne nlet ale s fully open an mantanng the man steam temperature unchange n orer to ajust loa wth the turbne at arable loa[]. Fgure. 600MW supercrtcal unt hybr operaton cure.runnng rogramme of Fee-water ump n The Varable Flow Down Fgure s a map ncatng the contons of boler fee-water pump operaton plan wth arable loa. In t I an II respectely represent characterstc cures of the man pump an the fore pump at freuency spee ; I an Irepresent characterstc cures of the man fee-water pump at fferent spees; I+II represents characterstc cure of seres operaton of the man fee-water pump an the fore pump at freuency spee whle I+II represents that of the man fee-water pump at arable spee an the fore pump; (I+II) parallel an(i+ii) parallel represent the characterstc cures of I+II or I+II uner parallel

3 u S-ke et al. / Energy rocea 7 ( 0 ) operaton. I an II represent effcency cures of the man pump an the fore pump n freuency spee g o g o g an g represent the characterstc cures of ppe through operatng ponts o o an to meet corresponng flows o o I an ; sto sto sti an st are fferental statc pressures that unts aopt fferent pressures n fferent loas. Accorng to the gen composton of boler water supply systems an the cure of unthybr operaton n orer to meet the nee of 90% ~ 0% loa slng pressure operaton two operaton schemes can be aopte for fee-water pump. Scheme that s two n-lne systems n parallel operaton: when a unt ecreasng from the rate loa o to ether loa aopts fferental statc pressure slng from the sto to the st so that characterstc cure translates from the ntal lne g o to g an then ntersects at the pont of operaton wth (I+II) parallel the characterstc cure of water pump. Scheme that s a sngle set of n-lne system runnng moe: when the unt loa s smaller than c the maxmum loa that a sngle set of n-lne systems can proe an when fferental statc pressure sles to the st g the ppelne characterstc cure forme after ajustng the openng of the water ale s ntersects at wth I+II the pump s n-lne characterstc cure. Fgure. A arety of programmes operatng agram of boler fee-water pump uner the Conton of Varable Loa Operaton.Fttng Forms of ump Characterstc Euaton As shown n Fgure although the moe number an the parameter of the man pump an the fore pump are all fferent ther characterstcs are smlar. In orer to facltate the analyss of the stuy we wll set the form of ther characterstc euatons uner freuency spee as[]: The characterstc euaton corresponng to the man pump performance cure I I : A0 A A () The characterstc euaton corresponng to the fore pump performance cure II I I :

4 56 u S-ke et al. / Energy rocea 7 ( 0 ) 5 60 B0 B B Where: I II -the lft of the man pump an the fore pump uner freuency spee m O; -pump flow m /h; I II -the effcency of the man pump an the fore pump uner freuency spee%; A 0 A A B 0 B B - the fttng coeffcent of cure I an II characterstc euaton ; -the fttng coeffcent of cure I an II characterstc euaton. (). the etermnaton of the total characterstc euaton corresponng to characterstc cure (I + II)parallel Accorng to the prncple of "eual flow capacty an hea superposton of pumps n-lne operaton" an "parallel runs the pump flow oerlays hea of eualty" [] the cure n Fgure characterstc euaton corresponng to I+II fttng euaton are : ( A0 B0 ) ( A B ) ( A B ) ( ) parallel ( A0 B0 ) ( A B ) ( A B ) (). the etermnaton of the total characterstc euaton corresponng to (I + II) parallel When aoptng arable spee ajustment to aapt the arable loa of the unt ths etermnaton of characterstc cure shoul assume that the fore pump stops runnng an accorng to pump s theory of smlartywe can get the corresponng characterstc euaton when the arable spee of the man pump s n : n n A0 ( ) A ( ) A (5) n n When the fore pump an the man pump at arable spee run n parallel the characterstcs euaton corresponng to I+II may be represente by type (5) an () whch hea an flow characterstc euaton supermpose upon: n n [ A0 ( ) B0 ] [ A ( ) B ] [ A B ] (6) n n The soluton process of the characterstcs euaton corresponng to (I+II) parallel s the same wth that of type () so: n n [ A B A B parallel 0 ( ) 0 ] [ ( ) ] [ A B ] (7) n n The etermnaton of The Resstance Coeffcent an Characterstc Euaton of The pelne As shown n Fgure ntal characterstc euatons of ppelne system a-b-c- n the rate operatng contons can be represente as: g ( a) st Sg 0 p h Sg (8) Where: go -ppelne system resstance m O; sto -fferental statc pressure between boler an eaerator sto = p o h a m O; ()

5 u S-ke et al. / Energy rocea 7 ( 0 ) p o -the operatng fferental pressure between boler an eaerator n rate operatng contonsp o =p -p m O; h a -mountng heght between boler top an eaeratorm; S go -ntal total resstance coeffcent of water supply ppe a-b-c-h /m 5. In orer to etermne the relatons between the total resstance of the ppelne system an the flow the key to gen ppe system s to know ts resstence S go. From (8): g g ( ) st p ha S g (9) It s worth notng that when the loa changes from o to I an thus Scheme s aopte as a result of the unt aoptng slng-pressure operaton operatng fferental pressure between the boler an eaerator changes from p o to p. Although the resstance of the ppelne changes from o to wth the change of flow reference type (8) eres characterstc euaton for ppelnes: g st Sg ( p ha) Sg (0) but the number of ts resstance wll not change. So the characterstc cure of the ppelne wll rop from g o to g When unt operatng pressure contnues to eclne to an thus Scheme s aopte unt operatng fferental pressure wll change from p to p.therefore we shoul frst ajust the openng of s the water ale so that ppelne characterstc cure goes to g o then to g. Thus ther corresponng performance euaton an ppelne resstance can be entfe as: g o then to g. Thus ther corresponng performance euaton an ppelne resstance can be entfe as: g ( p ha ) S g g ( p ha ) () S g The etermnaton of the fee-water pump spee For scheme because of the two systems n parallel operaton we can get the spee rato of each pump by combnng Es () an (): A A0 B0 B A B S g st n ) n A 0 For scheme although t may meet the reurements of the same flow yet t s fferent from the spee rato of man fee pump spee n Es (6). Due to a sngle set of system operaton the spee rato of ts man fee pump shoul be etermne by combnng Es (0) an (5): n A A0 B0 B A B S g st A () n A0 A0 Therefore effcency of o I o II I II I II workng ponts are:

6 58 u S-ke et al. / Energy rocea 7 ( 0 ) 5 60 () Total axs power of fee-water pump n Scheme : ) ( g (5) Total axs power of fee-water pump n Scheme : ) ( g (6) 5.The Determnaton of The Effcency an ower of The ump Operatng ont The relate consumpton rato of these two schemes: 00% (7) 6.Engneerng Calculaton Example As shown n Fgure takng a 600MW supercrtcal generators n 90% ~ 0% loa use pressure operaton for example we contrast the power consumptons of the boler fee-water pump n fferent operaton moes an summarze calculaton results n table. What s known nclues the unt loa ratngs o =008m /h workng pressure p =5.Ma50m Oeaerator pressure p =.0Ma 00m O corresponng saturate water temperature t=8ensty=787kg/m ;As s also known the heght fference between the top of the boler an the nstalle pump s h c =65m whle that between the eaerator an the pump s h ab =5m. Thus sto =90m Owater supply ppe resstance number S go =.0-5 h /m 5 the freuency spee sngle-set of the crtcal loa of water supply systems c =065.7m /h5.% of the total loa. The man fee-water pump an the fore pump n freuency spee characterstc euaton fttng as follows. The characterstc fttng euaton of man fee-water pump T00-0-5s+k (freuency spee n o =576r/mn) s: (The characterstc fttng euaton of the fore pump ZB5-60 (freuency spee no=87r/mn s: From the calculaton results n table t s note that for Scheme ts man fee-water pump spee hea effcency an shaft power ecrease wth the loa. oweer the fore pump has an narable

7 u S-ke et al. / Energy rocea 7 ( 0 ) spee an ecreasng effcency an shaft power wth unt loa reucton ts hea ncreases as the loa ecreases untl reachng the maxmum alue when the loa s 0%. Neertheless the scheme's total lft system an total shaft power ecrease as the loa ecreases. As for Scheme II snce the possble maxmum loa proe by ths scheme s only 5.% of the total loa we hae to contrast an analyze strctly 50% ~ 0% of the loa n table. The araton regularty of eery parameter corresponng to the loa s smlar to Scheme wth fferent specfc alues. Wth 50% of the loa the total shaft power of Scheme II s hgher than that of Scheme.75% accorng to type (); oweer wth 0% an 0% of energy consumpton t s lower by respectely 9.75% an 6.9% because man pump effcency of Scheme II s much hgher than that of Scheme It can therefore be conclue that we shoul aopt Schemewhen unts change wthn 90% ~ 50% of the loa an aopt Scheme II wthn 0% ~ 0%. TABLE. 600MW UNIT ARAMETERS CALCULATION ABOUT TE BOILER FEEDWATER UM MORE ROGRAMMES OERATING UNDER SLIDING RESSURE OERATION System operaton moe The two systems n parallel operaton (programme ) Sngle set of system operaton (programme ) Loa percentage (%) Varable contons System total flow /(m /h) Slng statc fferental pressure st /m O Sotatng spee n /(r/mn) umpng hea The man I /(m O) fee-wate Effcency r pump I / (%) Brake horsepower I /(kw) Sotatng spee n /(r/mn) umpng hea II /(m O) The forepump Effcency II / (%) Brake horsepower II /(kw) The total number of water supply ppe resstance S/ h /m Total lft pump I+II /(m O) Total axs power fee water pump I+II /(kw) Conclung Remarks Wth "energy-sang emsson reucton" an "encouragng great generator shuttng own a small generator" the electrc power nustry the power plants wth 600MW unt as the man unt freuently shouler the responsblty of ajustng the loa. Although the current slng-pressure operaton s better than the constant pressure n terms of the thermal effcency yet t s a more complex process to ajust to guarantee the economcal operaton of fee pumps. focusng on ths stuaton an takng 600MW

8 60 u S-ke et al. / Energy rocea 7 ( 0 ) 5 60 supercrtcal unt for example ths artcle comprehensely analyzes the pump s seres an parallel combnatons of the boler water supply system an then eres seeral euatons of the effcency spee an the total hea of system corresponng to arous loas an slng pressures that the man pump alone s use to satsfy. an also ges a more reasonable operaton of fferent loas through examples. The analyss an concluson n ths paper hae proe reference for the practcal applcaton of the large-scale projects. Reference [] Ye Tao. Thermal ower lant (the Secon Eton). Chna Electrc ower ress :7-78. [] Chen Ru-ng. rncples an Operaton of Steam Turbnes. Chna Electrc ower ress : 6-. [] u S-ke L Ta Ba Jng-ru. Energy Consumpton Analyss of arallel ump of Open System for Non-synchronous Spee Control Operaton. 00.:8-. [] Yang Sh-chengWang X-ku. ump an Fan (the Secon Eton). Chna Electrc ower ress.00.8: