This document discusses heat recovery steam generators (HRSGs) which recover heat from exhaust gases to generate steam. It describes: 1) The basic types of HRSGs differentiated by flue gas flow direction including vertical and horizontal designs. 2) The main components of HRSGs including evaporator sections, superheaters, and economizers. Common configurations for these components are described. 3) Charts showing how the capacities of gas turbines, compressors, steam turbines, pumps and other parameters vary with increasing plant capacity.

1. Heat Recovery SteamGenerators
P M V Subbarao
Professor
Mechanical Engineering Department
Converts Waste into Power….

2. CC
AIR
INLET
GAS INLET
G
HP IP LP
HRSG
STACK
CONDENSER
PUMP
TURBINE
G
T=5500C
T=8500C
T=1500C
T=500C
T=1000C
T=5000C
T=600C T=500C
T=500C
P=1bar
P=10bar
P=10bar
P=2bar
P=170bar
P=.1 bar P=1bar
COMBINED CYCLE POWER PLANT

3. Cogeneration HRSGs

4. Types of HRSG
• Basic types of standard design of heat recovery steam
generators are differentiated by the direction of the flue gases
flow.
• Vertical HRSG
• Small footprint
• Simple concept of service
• Hanging design of heating surfaces
• Horizontal HRSG
• Small construction height
• High cycling ability
• Operational flexibility
• Hanging design of heating surfaces

5. Vertical HRSG

6. Horizontal HRSG
Vertical HRSG

7. HRSG COMPONENTS

10. ~400C
~5500C
~1000C

11. Schematic Diagram of a Simple HRSG
~5500C
~1000C

12. Super heater configurations
• Three basic super heater designs are:
• Horizontal Tube,
• Vertical Tube, and
• I-Frame

13. Used when gas flow is vertical up at the outlet.

14. Convective Super heater (Horizontal)
S1
S2

15. Used when the gas exits horizontally

16. Convective Superheater (Pendant)
S1
S2

17. Types of Evaporator Sections
• D-Frame evaporator layout
• O-Frame evaporator layout
• A-Frame evaporator layout
• I-Frame evaporator layout
• Horizontal tube evaporator layout

18. •This configuration is very
popular for HRSG units
recovering heat from small gas
turbines and diesel engines.
•It is a very compact design
and can be shipped totally
assembled.
•It is limited, however, since
the bent tube arrangement
quickly causes the module to
exceed shipping limitations for
units having a large gas flow

19. O-Frame evaporator layout.
This configuration has
probably been used for more
years than any of the others.
It has the advantage of the
upper header being configured
as the steam separation drum.
Or, the upper header can be
connected to the steam drum
by risers, allowing more than
one O-Frame evaporator to be
connected to the same steam
drum, resulting in shipable
modules being able to handle
very large gas flows.

20. A-Frame evaporator layout.
This configuration is simply a
variation of the O-Frame
Evaporator.
It was popular for services with
a large amount of ash, since
the center area between the
lower drums could be
configured as a hopper to
collect and remove solid
particles.

21. I-Frame evaporator layout.
In the past twenty years, this
configuration has become the most
popular.
This type module can be built in
multiple axial modules or in multiple
lateral modules, allowing it to be
designed to accept any gas flow.
There are numerous variations of
this design where tube bundles may
contain one, two, or three rows of
tubes per header. It is also,
normally, more economical to
manufacture,
ship and field construct.
The tube bundles may be shipped
to field installed in the modules, or
as loose bundles which are installed
into a field erected shell.

22. Horizontal tube evaporator layout.
The horizontal tube evaporator is used, not only for heat recovery
from Gas Turbine exhaust, but for recovery from flue gases in
Refinery and Petrochemical furnaces also.
It has similar size limitations
due to shipping restrictions
similar to the O-frame
modules.
It is generally a less
expensive unit to
manufacture than the other
configurations.

23. Economizer

31. VARIATION OF GT & COMPRESSOR CAPCITIES WITH
PLANT CAPACITY
0
200
400
600
800
1000
1200
1400
1
0
0
3
0
0
5
0
0
7
0
0
9
0
0
1
1
0
0
PLANT CAPACITY(MW)
CAPACITY(MW)
GT CAPACITY
COMP.CAPACITY

32. VARIATION OFFUEL & AIR FLOW RATES
0
500
1000
1500
2000
2500
1
0
0
3
0
0
5
0
0
7
0
0
9
0
0
1
1
0
0
PLANT CAPACITY (MW)
FLOW
RATE
(Kg/Sec)
MASS OF FUEL
MASS OF AIR

33. VARIATION OF MASS FLOW RATES IN HRSG WITH PLANT CAPACITY
0
50
100
150
200
250
300
350
100 300 500 700 900 1100
PLANT CAPACITY (MW)
MASS
FLOW
RATE
OF
STEAM
(KG/SEC)
HP MASS
IP MASS
LP MASS

34. VARIATION OF ST & PUMP CAPACITIES WITH PLANT CAPACITY
0
50
100
150
200
250
300
350
400
450
500
100 300 500 700 900 1100
PLANT CAPACITY (MW)
CAPACITY
(MW)
STEAM TURBINE
PUMPS

35. CALCULATED VALUES OF HRSG MODULES IN A 101MW CCPP

36. VARIATION OF NUMBER OFTUBES IN HRSG WITH CAPACITY
1000
2000
3000
4000
5000
6000
7000
8000
100 150 200 250 300
CAPACITY (MW)
NO.
OF
TUBES
HP
IP
LP

37. Today’s Limits
• Limits are, in this case, meant to be state of the art
values of key performance factors of a HRSG application
• limits driven by economical and technical considerations.
• Triple Pressure Reheat Drum Type Boilers, natural
circulation: