Document rxezGrEJ21oV2rmnYbGLVOEkv

Station Heat Balance... Preliminary details oi a new unit In corporating the advantage* f very high steam pressures and temperatures were revealed recently by Philip Spora, President, American Cos and Electric Service Corp, in an article In Electrical World, June 29, 1953, p 72-6. The new 120,000 kw unit will replace Unit No. 1 (40,000 lew, reheat) at the Philo Sta tion of the Ohio Power Co. This unit was installed in 1924. Power's dimetrie schematic sketch, above, shows the preliminary heat-bal ance arrangement being considered as a basis for design. It conforms closely to Cycle VI, which wo were talking about on the preceding page. The plant will use double reheating. Steam con ditions at the throttle and two reheat inlets are (1) 4500 psig, 1150 F (2) 1150 psig, 1050 F and (3) 165 psig, 1000 F. New Footuro*. The throttle pressure Is fust shout duuhle the highest stesm pressure now being used in a few plants. This factor leads to adopting smalldiameter tubing at the high end of the cycle to develop needed strength with an economy of materials. The supercritical steam pressure means elimination of conventional boiler designs. The steam generator needs no drums because boiling is not involved. The unit utilises the onee-through prin ciple of heating. The once-through feature, and utilisa tion of cyelone furnaces, is expected to result in a very compact steam gen erator. Head room needed should he unusually low. The 1150-F throttle temperature demands using austenitic materials at the outlet end of the stcem< generator tubing, steam leads, and front end of the h-p turbine. This tempera ture Is SO F above the highest now being used. The 5500-psig feedwater pressure re quires a new design of pump, perhaps new pump arrangement. Wster o tioning and control of solids E steam generator, turbine and other of tho cycle will have to bo t carefully. There will probably 1 concepts developed in the field of water treatment. Seven stages of feedwater reflect the great economy of lbs r eratiro cycle with the high hest.jj used in ibis plant. Highest aumf heaters used in a few modem P^j today is eight. Deaeration will 1 formed In the fifth heater usioijj psig bleed steam from the msin tt While superior perfoitniwj achieved at the expense of mors! plicated equipment, (his is off*1 " smaller over-all site of the tiesffltf erator, turbine and condenser-JH sketches, lower left ond right PS and 63, show relative sizes fr j'jg I, III and Vf as higher steam cobs' and more complicated eyelet j ENGINEERING AND MANAGEMENT SECTION Feedwater System... Turbine-Generator... Ued s Universal Pressure steam ,r will be built by Babcock & o. This will be the Brel time . . . may use one of two schemes shown above. First scheme uses con ventional barrel-type pumps at constant ... to be built by General Electric Co will be a single-shaft machine run ning at-3600 cpm. A special h-p tur jjj ibis country commercially, nude up of many tubes conparallel, the unit acts as one _ g iube. It takes in 5500-psig KfT'one cod. Continuous beating Ijhe water at It travels through jn| ini it emerges as 4500-psig. Iwteim. There is no boiling. The `per pressure drop through the ineoerstor assures uniform dlstri* lejfjl water In the parallel lubes, lel/mire h-p side of the steam gen- speed to develop 2000 psls through last two healers. Variable-speed b-p pumps boost water out of Iasi heater to 5500 psia. Each of two pump sets will hove single-motor drive. Second scheme uses two pumps In parallel undet deaerator to raise pressure directly to S500 psia for flow through last two heaters of new design for these high pressures. bine in tandlm with reheat turbines of the reverse-flow type and a double-flow l-p turbine make up the unit. Steam at 4500 pel, 1150 F from the steam generator will pass through four steam leads to four pairs of stop and control valves at the front of the tur bine. The throttling control valves vary steam pressure to the first stage of the h-p turbine. Intercept valves in each of the hot reheat lines will protect the tur bine from overspeeding In event of a nest- be made up of small-ditdbing of eensideroble thickness, ompositlon varies with the ternnj, carbon steel at tho feedwater- Kid, and stainless steel at the Jmperalure steam-outlet end. tripout. Stop and control valves, steam leads, flanges end part of the inner shell of the h-p turbine will be mode of austen itic materials. GE is now studying the rotor to see whether it may be mode of rwfr cyclone furnaces will burn uaeasl to fire this unit. Gas leavgyrimary fumoce will be cooled W before entering the conveeJfaces. Recirculated Rue goo will ferritic materials with steam cooling, or whether the hlgh-temperoture parts must be made of more costly austenitic materials. The h-p element will be of double Qeooltnt. This will prevent slagtube convection surfaces. Jeering the convection passes ^tubular-type air heater, the shell construction; the low-temperature parts of the Inner shell and all the outer shell and fittings ore to be of ferritic materials. From the first reheat point SSlfflrsft fans and the stack. Part to the condenser the turbine will lie (as Is recirculated before enter?-*lr healer. No dust removal built entirely of ferritic materials. Two sets of reheat stop and intercept 9nt wiD be installed. valves must be provided. A special Ini. [free pressure of the feed pumps Lthe itesm-generator pressure. I*,*' pressure regulator at the Ftbrdttle controls the pump Performance... ... depends a great deal on the steam rial temperature regulator will sense the steam temperature at the turbine throt tle and will close the control valves if the temperature drops either too low or TJie-tnsin stesm flow and tern- conditions used in a steam plant. At loo fast. This will protect both the ;wfll control the firing rote. 1050 F, with either single or double steam generator and the turbine by pre fn the gas psases will control reheat, little gain in efficiency can be venting a condition Uke water carry nperstures at the two reheat obtained at pressures shove 4000 psig. over should the fire be lost. The pro Boosliag tho temperatures to 1200 F tection scheme is similar to (hat given jtt&i'core oi starting and transient keeps efficiency rising with pressure by an Initial-pressure regulator on a f*c,rcuU,ing valves with increase to shout 7000 psig. Philo Unit conventional boiler. |gn:orlfieei will pau fluid ,0 the No. 6 is expected to run at 8500 Btu Because of limited coolina-waler from the steam generator, per kwhr. This is on over-all thermal availability, and to use existing tunnels, ffrator, in turn, Pimm saturated efficiency of 40.1%, highest to he oi- the main condenser will be of 2-pass fijondenser. ruined so far. design. It must be completely right. fSt-XMlH 1-33 ENGINEERING AND MANAGEMENT SECTION 15 S s