1. 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 …..

2. Super Critical Cycle ~ 1990

3. Ultra Supercritical Installations of The World

4. Double Reheat Ultra Super Critical Cycle8

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

6. 21st century Rankine Cycles
Improvement in Efficiency, %

7. Super Critical Cycle of Year 2005

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

9. Advanced 700 8C Pulverised Coal-fired Power Plant Project

10. FUTURE ULTRA SUPERCRITICAL PLANT – UNDER DEVELOPMENT
EFFICIENCY 55 %

11. Nuclear Super Critical Cycles

12. Modular High-Temperature Gas-Cooled Reactor

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

14. Model – 2 :MHTGR

15. 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.

16. 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.

17. Deployment mode of MHTGR SC plant with live steam reheat cycle

18. Steam Generation : Explore more Causes for Wastageh
x=s

19. Look for More Opportunities to Reduce Wastage

20. Follow the Steam Path : Early Stage

21. Follow the Steam Path : Middle Stage

22. Follow the Steam Path : End Stage

23. Follow the Steam Path : The End

24. Save Wastage thru Recycling !?!?

25. Regeneration Cycle with Mixer (Open Feed Water Heater)

26. Synthesis of Rankine Cycle with OFWH5 6 T 6’ 4
p2=p6 3 2 1 7

27. 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:

28. Analysis of Regeneration through OFWH

29. Optimal Location of FWH

30. Performance of OFWH Cycle
~ 12MPa
htotal
pbleed, MPa

31. Performance of bleed Steam
~ 2 Mpa
hbleed
pbleed, MPa

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

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

34. Workoutput of bleed Steam
wbleed
y pregen, MPa

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

36. 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

37. Open (Direct Contact) Feed Water Heater

38. 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…

39. Closed Feed Water Heater (Throttled Condensate)

40. Closed Feed Water Heater (Throttled Condensate)

41. Control of Entropy Generation due to Liquid Heating

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

43. 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.

44. Typical Single Reheat Heater Cycle with HARP

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

46. Double Reheat Cycle with Heater above Reheat Point

48. More FWHs for a Selected Bleed Points

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

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

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

52. 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%.

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

54. 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.