Generation of Most Eligible Steam for Rankine Cycle P M V Subbarao Professor Mechanical Engineering Department Means to AchieveQualities of Working Fluid Preferred by Sir Carnot …..

Super Critical Cycle ~ 1990

Ultra Supercritical Installations of The World

Double Reheat Ultra Super Critical Cycle 8

Reheater Pressure Optimization for Double Reheat Units 97bar 110bar 69bar

21st century Rankine Cycles Improvement in Efficiency, %

Super Critical Cycle of Year 2005

Double Reheat Super Critical Plants Net efficiency on natural gas is expected to reach 49%. Net efficiency on coal is expected to reach 47%.

Advanced 700 8C Pulverised Coal-fired Power Plant Project

FUTURE ULTRA SUPERCRITICAL PLANT – UNDER DEVELOPMENT EFFICIENCY 55 %

Nuclear Super Critical Cycles

Modular High-Temperature Gas-Cooled Reactor

Modular High-Temperature Gas-Cooled Reactor with Supercritical Rankine Cycle

Model – 2 :MHTGR

Special Features Steam Generator (SG) for the Live Steam Supplier : The SC steam parameters at SG outlet are 25.4 MPa/571°C. For the helium side of SG, the inlet temperature is kept at 750°C to maintain 179°C temperature difference between the helium and the SC steam for effective heat transfer. The outlet helium temperature is designed to 330°C to maintain effective heat transfer between the helium and the feedwater. Although high steam pressure and temperature involves modifications of the once-through SG and relevant pipes, no additional difficulties in design and manufacture are expected.

Reheat Exchanger for Reheat Steam Supply The steam parameters at the inlet of the reheat exchanger are 4.38 MPa/311°C and 4.19 MPa/569°C at the outlet. For the helium side of reheat exchanger, the helium temperature at both inlet and outlet should be 350°C/750°C.

Deployment mode of MHTGR SC plant with live steam reheat cycle

Steam Generation : Explore more Causes for Wastage h x=s

Look for More Opportunities to Reduce Wastage

Follow the Steam Path : Early Stage

Follow the Steam Path : Middle Stage

Follow the Steam Path : End Stage

Follow the Steam Path : The End

Save Wastage thru Recycling !?!?

Regeneration Cycle with Mixer (Open Feed Water Heater)

Synthesis of Rankine Cycle with OFWH 5 6 T 6’ 4 p2=p6 3 2 1 7

Analysis of mixing in OFWH Constant pressure mixing process h6 y Consider unit mass flow rate of steam thru the turbine h2 1-y h3 Conservation of energy:

Analysis of Regeneration through OFWH

Optimal Location of FWH

Performance of OFWH Cycle ~ 12MPa htotal pbleed, MPa

Performance of bleed Steam ~ 2 Mpa hbleed pbleed, MPa

Comparison of Performance of Bleed & Condensing Steams hcond hbleed Pregen, MPa

Gross Workoutput of bleed Steam ~ 12MPa wbleed pregen, MPa

Workoutput of bleed Steam wbleed y pregen, MPa

More Work output with more bleed Steams wbleed y pregen, MPa

Progress in Rankine Cycle Power Plants Year 1907 1919 1938 1950 1958 1959 1966 1973 1975 MW 5 20 30 60 120 200 500 660 1300 p,MPa 1.3 1.4 4.1 6.2 10.3 16.2 15.9 24.1 Th oC 260 316 454 482 538 566 565 FHW -- 2 3 4 6 7 8 Pc,kPa 13.5 5.1 4.5 3.4 3.7 4.4 5.4 h,% ~17 27.6 30.5 35.6 37.5 39.8 39.5 40

Open (Direct Contact) Feed Water Heater

An Impractical Efficient Model for Power Plant Turbine B SG Yj-11,hbj-1 yj, hbj Yj-2,hbj-2 C OFWH OFWH OFWH C 1 ,hf (j) 1- yj hf (j-1) 1- yj – yj-1 hf (j-2) 1- yj – yj-1- yj-2 hf (j-3) n number of OFWHs require n+1 no of Pumps….. The presence of more pumps makes the plant unreliable…

Closed Feed Water Heater (Throttled Condensate)

Closed Feed Water Heater (Throttled Condensate)

Control of Entropy Generation due to Liquid Heating

Effect of no of feed water heaters on thermal efficiency and work output of a regeneration cycle Specific Work Output

Heater Selection and Final Feedwater Temperature In order to maximize the heat rate gain possible with ultra-supercritical steam conditions, the feedwater heater arrangement also needs to be optimized. In general, the selection of higher steam conditions will result in additional feedwater heaters and a economically optimal higher final feedwater temperature. In many cases the selection of a heater above the reheat point (HARP) will also be warranted. The use of a separate desuperheater ahead of the top heater for units with a HARP can result in additional gains in unit performance.

Typical Single Reheat Heater Cycle with HARP

Effect of Final Feedwater Temperature and Reheat Pressure on Turbine Net Heat Rate

Double Reheat Cycle with Heater above Reheat Point

More FWHs for a Selected Bleed Points

New Circuits of Desuperheater for Preheating of Feedwater in Steam Power Plants

New Circuits of Desuperheater for Preheating of Feedwater in Steam Power Plants

New Circuits of Desuperheater for Preheating of Feedwater in Steam Power Plants

Efficiency of Danish Coal-Fired Power Plants Continuous development resulted around the mid 80's in an average efficiency of 38% for all power stations, and best values of 43%. In the second half of the 1990’s, a Danish power plant set a world record at 47%.

Average efficiency, specific coal usage, CO2 emissions h Indian Coal Plants: Efficiency of modern coal power plant = 34-36% Efficiency of old power plant = 20-30%

Expectations from Modern Steam Generator for Higher Efficiency High Main Steam Pressure. High Main Steam Temperature. Double Reheat & Higher Regeneration. Metal component strength, stress, and distortion are of concern at elevated temperatures in both the steam generator and the steam turbine. In the steam generator’s heating process, the tube metal temperature is even higher than that of the steam, and concern for accelerated corrosion and oxidation will also influence material selection.