Document 6Rkg0J8ORayXv47XM2argLxpm

Halliburton ICS Skid Pumps fit nicely into Southern California Edison's pre-operational cleaning plans. CUSTOMER: Southern California Edison Company (Alamitos Steam Station near Long Beach). ASSIGNMENT: Ready new steam generator Unit #5 for start-up by ridding it of iron oxide mill scale deposits. heated to a temperature of 200 F, was circulated throughout the pre-boiler system, the boiler, the super-heat and re-heat sections at a rate of from 1,000 to 4,000 gallons per minute. After chemical cleaning was completed satisfactorily, the entire system was flushed with high purity water. Halliburton moved its skid mounted pumps, power packs, and temporary piping directly into the heart of the unit. Once the acid cleaning station was set up, a cleaning solution consisting of a mixture of hydroxy acetic formic acids was introduced into the piping systems of the steam plant. This solution, POINT TO REMEMBER: What the Halliburton Chemical Cleaning Specialists did for the Southern California Edison Company they can do for your operation -- with the best equipment at lowest costs consistent with excellence. Worth investigat ing, don't you think? COMBUSTION / July 1967 INDUSTRIAL CLEANING SERVICES COMPANY DUNCAN. OKLAHOMA RS400216 1/17/02 NUECES MOTOR A OAMPER FAN C=J AIR INLET A. CONSTANT SPEED FAN WITH DAMPER CONTROL 1 MOTOR FAN AIR INLET VANE B. CONSTANT SPEED FAN WITH VANE CONTROL MOTOR HYD. CPLG. AIR FAN INLET SPEED CONTROLS SCOOP TUBE-'' C. VARIABLE SPEED FAN WITH MOTOR 8 HYDRAULIC COUPLING STEAM turbinI G0 E A FAN R D. VARIABLE SPEED FAN WITH VARIABLE SPEED TUR8INE ORIVE Fig. 1--Methods for driving forced-draft fans t-H-SMITH &-T By R. H. DUNHAM,*/ Tennessee Valley Authority, y N. E. NUTTER and R. W. WILLIAMS, General Electric Company The Application of Steam Turbines for Driving HE methods used to drive steam plant auxiliaries Tcan have significant effects on plant performance in the following areas: 1. Over-all heat rate or elYicienev. 2. Net output power. -- ']. Operating flexibility 4. Evaluated investment cost. 5. Dependence on outside power sources for start-up. As the power requirements for these auxiliaries increase with the use of larger capacity generating units, efficient methods for driving them become more important. Thus, as the rating of turbine-generator units increased above 4IH),1)1)0 kw, separate steam turbines became the predominant method for driving boiler feedpumps. Improvements in plant performance resulting from the application of turbine driven feedpumps have been " Presented at the 20 th Atuui.iI Meeting .,f the American Power C-mfcie:ue. Apul 1\~17. I9i>7 Chicago Him.ns studied extensively and treated in other papers. Since the forced-draft fans have power requirements second only to the boiler feedpumps in the typical fossil fueled generating plant, it follows that the effect on plant per formance of turbine drives for these fans should be studied.1 Methods for Driving Forced-Draft Fans Fig. 1 shows four common methods for driving forceddraft fans and controlling air flow to the boiler. Some of these methods are more efficient than others even when operating at the maximum fan rating or test-block con- 1 It should be noted that, in addition to the fan-drive turbines for the TWA Paradise 3 Plant which are described in this paper, other applications of steam turbine-driven forced-draft fans for generating plants exist. For example, turbine-driven forced-draft fans have been in successful operation for over five rears on the Cleveland l^lcctric Illuminating Company's Lake Shore Unit IS where two 2a00 hp fans are driven in tandem through a reduction gear by a >000 hp turbine. Also.^on the South Carolina Electric and Gas Company's Canaday Unit 3 which is scheduled for operation this year, a single 3700 hp 'team turbine will drive two forced-draft fans through a reduction-geai having a double ended output shaft. 28 RS-000217 July 1967 '/ COMBUSTION 1/17/02 NUECES rig. 2--tosses associated with forced-draft fan drive systems operating at the maximum normal plant condition CONSTANT SPEED FAN WITH DAMPERR CONTR0L 165 HP INPUT EFFICIENCY 60.6% ;=>*AIR HR is~iriTT LOSSES---GGfEN. TRANS. MOTOR FAhN a DAMPER CONSTANT SPEED FAN WITH VANE CONTROL 140 HR INPUT EFFICIENCY 71.5% I AIR HR LOSSES---- Gt 1L MOiTOR FAN 8 VANE VARIABLE SPEED FAN WITH MOTOR a HYD..CPLG. 154 HP INPUT EFFICIENCY 65.1% ----- --<^L. TRkLs. JelrOR lip FAN I AIR HP 'fates for Fig. 2: Input powers shown are turbine shaft powers required to deliver one air horsepower to the draft system. Efficiencies shown are mechanical efficiencies with the illustrated losses considered. Data shown are for maximum normal operating condition of the steam plant, with normal fan shaft input power requirements for the variablespeed fans being 69% of the fan test-block rating and proportionally more for the constant-speed fan arrangements due to vane and damper losses. -LOSSES CPLG. VARIABLE SPEED FAN WITH TURBINE DRRIIVVE 1.19 HP inr3INPUT EFFICIENCY 84.1% I AIR HR LOSSES -GEAR FAN Forced-Draft Fans--TVA Paradise 3 Steam Plant* dition. The differences in efficiency are more pronounced at lower air flow conditions, such as the maximum normal operating condition of the power plant. The draft sys tem air power requirements (.proportional to the product of draft system head multiplied by the air flow rate) for the maximum normal plant operating condition arc usu ally only Go to 7(> per cent of the power requirements at the fan test-block condition. This fan air power margin is provided for tolerances in; draft system resistance, air flow requirements, and fan performance. The losses caused by reducing the air flow rate for normal plant operating conditions are significant. In the case of the motor-driven variable-speed fan, these losses result from hydraulic coupling slip introduced to control air flow. With the constant-speed fans, the losses are throttling losses caused by the discharge dampers or inlet vanes. The variable-speed turbine drive arrangement has the advantage of operation over wide ranges of air flow rates with small changes in efticiencv Fig. 2 shows the variable-speed turbine-drive svsiem to be the most efficient The next must efficient method. motor-driven fans with vane control, requires approxi mately 18 per cent more turbine output power to de velop a given amount of air power and the motor-hy draulic coupling arrangement requires approximately 2S per cent more turbine output power. As generating plant load is reduced for part load operation, the effi ciency of the auxiliary turbine fan-drive system holds up much better than the other arrangements. Plant Heat Rate and Kilowatt Gains with Auxiliary Turbine Driven Fans Since the turbine-driven fan system offers better efficiency than the other arrangements, a comparison of plant thermal performance for this arrangement and the next most efficient system, motor-driven fans with vane control, is warranted. Consider a steam plant cycle having a forced-draft fan with vane control, driven by a motor. Plant-cycle efficiency improvements and in creases in net station power output can be obtained by re placing the motor drive and vane control with a variablespeed condensing fan-drive turbine, as shown in Fig. ). 27 COMBUSTION July 1967 RS400218 1/17/02 NUECES 29 i iw i ncntiAf Heat Rate and Kilowatt Gains at Constant Main Turbine Throttle Flow Fig. 3--Steam cycle for o fan drive turbine taking steam from the main turbine low-pressure crossover and exhausting to the main condenser O At constant main turbine throttle flow, the flow to the low-pressure turbine is reduced with the turbine-driven fan arrangement since steam is removed from the lowpressure crossover to supply the fan-drive turbine. This reduces the main turbine exhaust loss which together with the increase in fan-drive system mechanical ef ficiency results in approximately equal percentage gains in thermal cycle efficiency and net plant power output. The approximate heat rate and net power gains are shown in Fig. 4 plotted as functions of main turbine parameters which are indicators of exhaust loading and exhaust loss. Fig. 4 shows the heat rate and net kilo watt gains to be greatest when fan-drive turbines are applied to cycles using main turbines with highly loaded exhaust sections operating at low exhaust pressures. Fan system efficiencies and power requirements used for the development of Fig. 4 are average values for systems where turbine drives have been studied by the authors. For a particular application these values may vary, de pending on the fan test-block rating as compared to the maximum normal operating condition, the type of boiler firing, and other variables. Fig. 5 and 6 have been in cluded to allow correction of the heat rate and kilowatt gains for differences in fan system efficiencies and power requirements. The method for using the presented curves is il lustrated by this example. Consider a turbine-generator rated 600,000 kw at 1.5 in. Hg abs and 0 per cent makeup in a plant with a motor-driven forced-draft fan and vane control of air flow to the boiler. The effect of replacing the motor-driven fan with a turbine-driven fan would be as follows: Ni ad A. Basic Data o 1. Main Turbine Type and Performance: Tandem- compound steam turbine with four exhaust ends oc having 222.5 sq ft of total exhaust annulus area, operating at valves wide open and with motor- driven fans to deliver 619,248 net kw (fan and feedpump power considered) at a net heat rate of 7724 Btu/Kw hr with 1.5 ins. Hg abs ex haust pressure. 2. The forced-draft fan shaft power required for the valves wide open condition with a turbine-driven fan is 12,190 hp and the fan efficiency at this RATEP KILOWATTS AT L5 IN.HGA. 0% MAKEUP LAST STAGE ANNULUS AREA IN SQUARE FEET condition is So per cent. The fan turbine has an efficiency of 81.5 per cent and its exhaust pressure is 2.0 ins. Hg abs. The reduction gear fig. 4--Heat rale and net plant kilowatt gains for auxiliary tOrbine-drtven efficiency is 9S.5 per cent. forced-draft fans as compared to motor-driven fans with vane control 3. The motor-driven fan with vane control has an Notes for Fig. 4: efficiency of 75.0 per cent at this condition and A. Gains shown are for the main turbine valves-wide-open operating condition. Heat rote ond kilowott gains are in percent of the base values with motor-driven fans for this condition. 8. Assumed conditions 1. Fan-drive turbine efficiency = 81.5% 2. Fan-drive turbine exhaust pressure -- moin turbine exhaust pressure 4~fX5 in. Hg abs 3. Turbine-driven fan efficiency = 85.0% 4. Turbine-driven fen shoft power required = 1.43% of main unit rating 5. Turbine-drive reduction gear efficiency 98.5% 6. Motor-driven fan efficiency including vane losses = 76.9% 7. Motor efficiency = 95.0% 8. Transformer efficiency = 99.0% 9. Generator efficiency = 98.5% the motor, transformer, and main generator ef ficiencies are 94.5, 99.2 and 9S.2 per cent, re spectively. B. Calculated Heat Rate and Kilowatt Gains with Turbine-Driven Fans 1. The basic gain is read from Figure 4 at the parameters: rated generator output/last-stage annulus area = 600,000/222.5 = 2690 and operating turbine-exhaust pressure = 1.5 ins. Hg abs. The basic gain = +0.33 per cent (interpolated). 30 RS-000219 My 1967 / COMBUSTION 1/17/02 NUECES .03 .02 .01 t are ,<< tine A ind iloare ded res. for :ms ars. dethe iler inatt .ver iltor :up me ing be mids ea, ar:!ld ite '.he en lis as ist ar in ad f- th ie X- at 0 500 IOOO 1500 2000 2500 MAIN TURBINE KILOWATTS UST STft ANNULUS AREA, SQ. FI X EXH. PRES&, IN. HGA Fig. 6--Effect of fan-power requirements on heat rate and kilowatt gains with turbine-driven fans Fig. 5--Effect of fan-system efficiency on heal rate and kilowatt gains with turbina-driven fans Notes for Fig. 6: A. Power corrections should be made on the basis of turbine-driven fan power requirement using a fan efficiency of 85%. B. The base turbine-driven fan shaft horsepower is 1.43% of the main turbine rating. Notes for Fig. 5: A. e motor drive = fan eff (includes effect of vane or damper) X motor eff X transformer eff X generator elf. B. c turbine drive = fan eff X gear eff. able to increase the main turbine throttle flow and re heat turbine flows to bring the low-pressure turbine flow up to its original flow with motor-driven fans. In this manner, the main turbine output can be increased by much more than in the constant throttle flow case, 2. The correction for fan-system efficiency is read although the heat rate improvements will be less. This from Figure 5 at the parameter R = (.75)(.945)- arrangement can be very attractive for units which are (.992) (.982) / (.S5) (.985) = 0.S24. The gain load limited by the flow to the last stage of the low-pres correction for efficiency is +0.05 per cent. sure turbine since it provides more net kilowatts for a 3. The correction for fan power requirements is given main turbine size. However, this increased tur read from Figure 6 at the parameter, (kw)/(sq bine capability may require increased ratings of the ft) (in. Hg abs) = (600,000)/(222.5)(1.5) = boiler, generator, and other station equipment. The 1790. The gain correction for a 5 per cent in increase in net kilowatt capability by this method would crease in fan power is +0.01<$3 per cent. The be approximately three times the Ian power requirements base fan power is (0.0143) (600,000)(.1-34) = at the main turbine valves wide open condition. 11,500 hp. The per cent increase in fan power is (12190-11500)(100)/11500 = 6.0 per cent. The gain correction for fan power = (H01S3) Extracting Steam for Air Preheating from Fan-Drive Turbines (6.0)/(5.0) = +0.022 per cent. If analysis of the power plant heat cycle indicates that 4. The total heat rate and kilowatt gain factor (in steam coil air preheaters are desirable to preheat the air per cent) = 0.33 + 0.05 + 0.022 = +0.402. entering the gas-to-gas air preheater, fan drive turbines Therefore the heat rate and net kilowatt gains offer another possibility for gains in station thermal at main unit valves wide open are as follows: performance. Extraction steam for air preheating Heat Rate Gain (Reduction) = (7724) X should ideally pass from the source (turbine) to the air (0.00402) = 31 Btu/Kw hr. Net Kilowatt preheater with minimum pressure drop to avoid throt Gain (Increase) = (619,24.x) X (0.0041)2) = tling losses which degrade plant heat rate. However, 21S9 Kw. when steam is extracted from the main turbine for air This method for calculating heat rate and kilowatt gains for fan-drive turbines is similar to a method for predicting the effect of auxiliary turbine-driven boiler feedpumps on plant performance which was presented in a 1966 American Power Conference Paper. See Ref. 0). preheating, consideration must be given to the lowest main turbine load at which the air preheater must func tion on this steam source, since the extraction pressure decreases with main turbine load. Design of the steaineoil air preheater for this minimum main turbine load condition requires that throttling of the air preheating steam be tolerated lor high main-turbine loads; the Heat Rate and Kilowatt Gains at Constant LowPressure Turbine Flow extraction pressure being high. An alternative is the use ot a controlled-pressure extraction on the fan-drive turbine to furnish steam for the air preheater. The con- When replacing the motor-driven fan with a turbine- trolled-extractimi pressure fan-drive turbine maintains driven fan receiving steam from the main turbine low- constant extraction pressure without introducing large pressure crossover, as shown in Fig :>. it mav be desir throttling losses. The method bv which this is ac- N COMBUSTION July 1967 rS-00022 1/1TK NUECES 31 complished is discussed later in this paper. Expansion provide fan power for boiler purging. During a of steam in a turbine to a lower extraction pressure and start of the turbine-generator, it may be possible-to t enthalpy before using it to heat combustion air will re operate the fans on stored boiler steam and deliver suf sult in over-all heat-cycle efficiency improvements; ficient air flow to allow refiring of the boiler; otherwise it ! the degree of improvement depending on the quantity would be necessary to start the auxiliary boiler to supply of extraction steam required and other characteristics of steam for the fan turbine. Turbine-driven fans, like the thermal cycle. turbine-driven boiler feedpumps, reduce the dependence . of the generating plant on outside sources of electric Steam Sources for Fan-Drive Turbines power for startup and increase its potential for getting on If a separate steam turbine is used to drive the forceddraft fans, a logical question is where should steam be taken to supply the fan turbine for optimum cycle ef ficiency. Because of the large throttle flow require ments of the fan-drive turbine, the choices considered will be restricted to the major steam lines in the cycle: the superheater outlet, cold reheat, hot reheat, and lowpressure crossover lines. While the data required to prove the following is too extensive to present here, the general conclusion reached is that gains in station thermal performance will be greatest with the fan-drive turbine receiving steam from the low-pressure crossover line, as shown in Fig. 3. particularly if the main turbine the line, delivering power, during emergency situations. . The use of steam turbines to drive forced-draft fans helps to provide automatic fast response of the air supply system to flow change demands without causing fluc tuations in station auxiliary electric power requirements. The steam turbine, having an oil-relayed speed control system, can change power levels rapidly to accelerate the fan, a high inertia load, and meet air flow demands. The turbine control system can be designed to set turbine speed in response to an input signal proportional to air flow requirements; thus allowing the supply of air to the boiler to be an automated subloop in the plant control system. has a low-pressure section which is highly loaded. How ever, if the low-pressure section is not highly loaded and if the air preheating steam requirements are large enough to justify a controlled extraction on the fan-drive tur bine for air preheating, cold reheat steam may be the best source for the fan-drive turbine. Effect of Turbine Drives for Forced-Draft Fans on Evaluated Plant Investment Costs Turbine drives for forced-draft fans can result in a lower evaluated investment cost on a dollars per kilowatt of station capability basis. The improvement in evalu ated cost depends on the kilowatt and heat rate gains for Startup and Light-Load Operation of Fan-Drive Turbines The use of fan-drive turbines taking steam from either the main turbine low-pressure crossover or the cold reheat for normal operation requires that an auxil iary steam source be provided for these turbines during plant startup and light-load operation of the main tur bine, since the steam pressure at the normal source on the main turbine will not be sufficient to meet the fanpower requirements under these conditions. Steam from a station auxiliary boiler can be used to supply the fan turbine during startup and light-load operation. For some applications the fan drive turbines have been the particular application. Generally, the improvement will be greatest for tandem-compound main turbines having highly loaded low-pressure sections and boilers having large fan-power requirements, such as coal-fired, types using cyclone burners. For most applications of turbine-driven fans, the re duction in evaluated investment cost does not result from a lower total equipment cost but from the increase in plant capability and improvement in plant heat rate. These additional kilowatts of capability can be added at a lower cost per kilowatt than that of the base-plant kilo watts. provided with second iidets which receive steam directly Forced-Draft Fan-Drive Turbines for TVA's from the main boiler superheater outlet. In these cases, Paradise 3 Steam Plant the turbine control valves are arranged so that main boiler steam is used onlv when the normal supply from the main turbine is insufficient to meet the fan-power requirements. For these applications, a steam line tie to the station auxiliary boiler is also required to supply fan power for starting the main boiler. The secondary high-pressure steam inlet is verv similar to that provided on dual inlet boiler-feedgiump-drive turbines and allows the auxiliary turbines to operate independent of the main turbine. For the TVA Paradise 3 steam plant, three turbines, each driving a one-third-size forced-draft fan, were ap plied to the heat cycle as shown in Fig. 7; taking steam from the cold reheat line and exhausting to condensers. A constant-pressure extraction for feeding air pre heaters was provided on each fan-drive turbine. This arrangement provides heat rate gains as shown in Fig. S, at the maximum normal main turbine operating condition. Since the low-pressure turbine sections of the main turbine were not highly loaded, and since large Operating Flexibility of Turbine-Driven Forced-Draft Fans quantities of air preheating steam were required, fan tur bines receiving steam from the cold reheat and having The provision of a secondarv inlet on the fan-drive controlled extractions for air preheating yielded better turbine increases its operating flexibilitv. For example, performance characteristics than straight condensing should the main turbine be tripped from operation, the turbines receiving steam from the low-pressure crossover. fan turbine with a high pressure inlet will automatically The heat rate gains vary inversely with the air preheating take steam directlv from the superheater outlet of the requirements, and for a mean air temperature of 57.3 F boiler to maintain fan power which will allow the boiler resulted in a heat rate improvement of approximately to continue to operate If the boiler tires 11111-1 be 11 3 per cent for this application. tru.iped under this condition, the 1.111 turbine can operate The three Ians are driven through reduction gears bv on steam stored m the boiler brum it sunerhealer to -teaui turbines rated 11,75b hp each. The expected fau- 32 RS-000221 July 1967 ! COMBUSTION 1/17/02 NUECES * + + + + STEAM SOURCE FOR LIGHT LOAD OPERATION Fig. 7---TVA Paradise 3 steam plant heat cycle r requirement at the maximum normal operating sponse to an electrical air flow demand signal and main ition of the main turbine is 22.N00 hp, or approxi- tains constant extraction pressure. These control func Iv 1.(1 per cent of the main turbine rating. The tions operate simultaneously as in the following examples: test-block fan-power requirement is 34,731 hp. lal steam supply to the lan-drive turbines is from 1. If the turbine speed is below that necessary to old reheat line; however, a supplementary source is meet the air flow requirements, the speed governor (led from the high-pressure steam line for light-load opens both the extraction and inlet control valves ition and furnace purging after trip-out of the main to allow more steam to pass through the turbine to ue. Auxiliary boilers supply steam to the turbine- increase speed but not affect extraction pressure. n fans and boiler feedpumps for startup. The fan- 2. If the extraction pressure is below the set value, turbines exhaust to individual condensers which the pressure governor opens the inlet valves but to the main condenser and individual air preheaters . . closes the extraction valves to increase the extrac ipplied by the controlled-pressure extraction on each tion pressure while maintaining constant speed. ie. Each air preheater is divided into two operat- ections; one section receiving steam through a The low-pressure inlet and extraction control valves raturc-controlled valve to maintain constant air are multiple valves feeding seetionalized nozzle plates, temperature, and the other coming into service although for simplicity, they have been shown as single uitically. and operating at constant pressure, when valves. Each fan drive turbine has five stages ahead of let air temperature is so low that additional air heat- the extraction and four stages in the exhaust section. irface is required Turbine speeds are adjusted The turbines have rating of 11,750 hp at 5000 rpm and uitically to meet the draft svstem flow demands, drive the tans at a maximum speed of 130S rpm through indent of the extraction flow for air preheating. single-step reduction gears. 9 is an elementarv schematic of the Paradise 3 In the course of the forced-draft fan-drive study for ive turbine. The turbine is divided into two sec- Paradise lnit 3. several arrangements were considered; hv an extraction valve gear which controls the ex- lor example: four tans with individual motor drives, 'ii pressure bv regulating steam (low to the exhaust lour fan-- with individual turbine drives, two turbines i. The turbine control svstem sets speed in re each driving two fans, extraction turbines integrated into USTION , July 1967 RS-000222 1/17/02 NUECES 33 9 j Since [second fueled lit per|uld be forcedSome jn when ci k con- r the TV A is of s.te.n; j example. |r over rive re Unit l> I by ^ ompanv e 3700 hp sir having USTION AMBIENT AIR TEMPERATURE, F fig. 8--TV A Paradise 3; heal rate gains for fan-drive turbines with controlled extraction for air preheating, as compared to motor-driven fans with air preheating steam taken from the main turbine low-pressure crossover Fig. 9-M-Schema1k of forced-draft fan-drive turbine with controlled extraction for air preheating the feedwater cycle, and straight condensing turbines with various methods of air preheating. From the view point of plant performance factors such as thermal ef ficiency, net station power output capability, operating flexibility, and plant evaluated investment cost, the three fans with individual turbine drives having controlled ex tractions for air preheating proved to be the most attrac For some main turbines where the low pressure sec tions are not highly loaded, condensing fan drive turbines taking steam from the cold reheat line and supplying air preheating steam from a constant pressure extraction may offer better heat rate gains than straight condensing turbines taking steam from the low-pressure crossover line. The effect of the fan drive turbine's location in the tive arrangement. steam cycle should be investigated for each application Conclusions to assure optimum performance gains. The use of turbines to drive fans reduces the depend Steam-turbine drives for forced-draft fans can offer improvements in power plant performance in the areas of : (1) thermal cycle efficiency, (2) net station output power, (3) operating flexibility, (4) evaluated investment cost and (5) reduction of station dependence on outside power sources for startup power. The extent of heat rate and kilowatt gains and reduc tion in evaluated equipment cost depends on the power requirements of the fans and will be greatest for plants using coal-fired boilers with cyclone burners since this arrangement requires large quantities of fan power. Also, the use of main turbines having highly loaded lowpressure sections operating at low exhaust pressures will ence of the power plant on outside sources of power for plant startup and together with turbine-driven boiler feedpumps can affect major reductions in outside power requirements. In a similar manner, its ability to maintain fan opera tion for boiler purging after trip-out of the main turbine is another step toward reducing station dependence on outside power sources. It is not the intent of this paper to imply that turbines will be the best method for driving forced draft fans in all generating stations, but is to show that, when fan power requirements are large, considerations should be given to turbine drives for these auxiliaries. increase the heat rate and kilowatt gains to the range of '/< to V2 per cent on a constant throttle flow basis On a constant low-pressure turbine flow basis, the heat rate gains will be less, but the kilowatt gains will be.approxi mately three times the fan power. The above gains are REFERENCE on the basis of straight condensing fan-drive turbines taking steam from the low-pressure crossover as com pared to motor-driven fans with vane control. (1) "Heat Rate Gains in Utility Power Plants with Condensing Auxiliary Turbine Drives." R. C. Spencer, H. A. Mayor and S. Styrna, The American Power Conference, April 1960, Chicago, Illinois. RS-000223 1/17/02 NUECES 34 July 1967 / COMBUSTION