The document summarizes a presentation given at the IV International Conference on Advances in Energy Research. The presentation was given by Pradip Mondal, a PhD scholar at Bengal Engineering and Science University, and discussed the development of a model for a wood-based indirectly heated combined cycle plant. The presentation provided an overview and introduction on biomass and bioenergy resources in India. It then described the schematic layout of the proposed plant and discussed the modeling methodology, including assumptions made. Results showed the plant could achieve over 37% efficiency at optimal operating conditions. The conclusions highlighted that exergy losses primarily occurred in the gasifier, combustor-heat exchanger, gas turbine, and heat recovery steam generator units.

1. IV th International Conference on Advances in Energy Research
Presented By: P Mondal
PhD Scholar
Co-author: Dr. S Ghosh
Associate Professor
BENGAL ENGINEERING & SCIENCE UNIVERSITY, SHIBPUR
DEPARTMENT OF MECHANICAL ENGINEERING
HOWRAH-711103, W.B.

2. Overview
Introduction and perspective
Schematic of the proposed plant
Model development
Results and discussions
Conclusions

3. INTRODUCTION
AND
PERSPECTIVE

4. Introduction-Present Energy Scenario
4

Energy consumptions in the Asian developing countries are
increasing rapidly.

Indian power sector is strongly dependent on the fossil
fuels.

Reserve of fossil fuels are getting depleted day-to-day.

Burning of fossils fuels is a major source of greenhouse gas
emissions.

Need to pay more attention towards the development of
reliable, economic and environment friendly technologies
in converting the renewable energy resources in useful
work.

5. Introduction-Biomass & Bio-energy
5

Biomass has a very high potential as renewable energy source
in rural India.

Total projected capacity of production/reserve is about 889.71
Million Tones for the year 2010.

Solid biomass is converted into combustible synthetic gas
through it’s gasification.

Major components of synthetic gas are CH4, H2, CO, CO2, H2O
and N2.

Overall efficiency of power production from biomass can be
increased to 35-40% using gas turbine-steam turbine (GT-ST)
combined cycle integrating a gasifier in the system.

6. Introduction-Directly Heated GT Cycle
6
Problems
Tar and
Moisture
Lower in
longevity
of the GT
Particulate
Matter
Sulphur
Content
Corrosion , Erosion
and Deposition on
the turbine bladings

7. Introduction-Indirectly Heated GT Cycle
7
Solutions
No need of
cooling
arrangements
GT bladings
are safe from
corrosion and
erosion
Long ,
Economic and
Reliable
Operation
GT bladings
are safe from
particulate
deposition
Operates on
low cost and
dirt fuels

8. LAYOUT OF THE
PROPOSED
PLANT

9. Wood Based Indirectly Heated Combined Cycle Plant
34
23
Combustor-Heat Exchanger Block
27
1
21
5
20
25
26
30
H
5
31
33
26
22
6
28
28
29
6
2
24
H
32
25
7
3
27
Air Gasifiication Block
Pel =
4
3
9
1
30.00 kW
4
2
Indirectly Heated Gas Turbine Block
35
8
7
14
18
10
17
8
11
H
Superheater
9
16
12
12
21
15
19
H
24
11
15
Evaporator
23
22
13
17
16
10
20
18
14
13
H
Economizer
19
9
Steam Turbine Block

10. MODEL
DEVELOPMENT

11. Model Development
11
Characteristics of fuel used:
Parameter
Ultimate Analysis
Unit
Value
Mass percentage on wet basis
C
%
50
H
%
6
O
%
44
LHV (MJ/kg)
MJ/kg
16.3
Moisture
%
7.2

12. Model Development
12
Assumptions in the present study:

Post combustion temperature is limited to a value about 1300 0C.

The plant component operates at steady state.

No pressure and heat loss is assumed for the tubing and heat exchangers.

The compression and expansion processes are adiabatic (isentropic efficiencies of
90% for topping compressor and gas turbine, while the value is 85% for bottoming
steam turbine).

The inlet steam condition is 10 bar, 3500C. The condenser pressure is 0.1 bar.

For the HRSG, minimum pinch point temperature difference is set to15 0C. The
stack temperature is 1200C.

13. Thermodynamic Analyses-Energy
13
Gasifier Unit:
Gasification reaction:
CH a Ob + m(O2 + 3.76 N 2 ) → X 1H 2 + X 2CO + X 3CO2 + X 4 H 2O + X 5CH 4 + X 6 N 2
Water gas shift reaction and methane reaction:
CO + H 2O → CO2 + H 2
C + 2 H 2 = CH 4
Gasification efficiency:
ηgasi =
m p.g LHV p.g
mbiomass LHVbiomass
Assumptions:

Tar formation is not considered in this model.

The bed temperature of the gasifier is set to 8000C and the oxidant (air)/biomass ratio xOF is 1.8

14. Thermodynamic Analyses-Energy
14
CHX unit:
Combustion equation:
X 1 H 2 + X 2CO + X 3CO2 + X 4 H 2O + X 5CH 4 + X 6 N 2 + m ′(O2 + 3.76 N 2 ) →
X 7 CO2 + X 8 H 2O + ( X 6 + 3.76m′) N 2 + X 9O2
Post combustion temperature:
o
∑ X j ( h fj
j
+ ∆h) producergas + ∑ X j (h o + ∆h)air = ∑ X j (h o + ∆h) fluegas
fj
fj
j
j
Heat exchanging:
4.76m' (∆ h)air = X g ( ∆ h) f .g .m
Where Xg represents the number of moles of hot exhaust gases leaving the combustor
X g = X 6 + X 7 + X 8 + X 9 + 3.76m′

15. Thermodynamic Analyses-Energy
15
Combined cycle unit:
Compressor:
wc = c p,a (Tc,o - Tc,i )
Gas turbine:
wGT = c p,a (TGT,i -TGT,o )
Net GT output:
wnet = ( wGT − wc )η G
Gas mixture:
m f.g,m = m f + ma
m f cΔT + m c a ΔT = m
p, f
p,a
c
ΔT
f.g,m p, f.g,m
Steam generation rate:
m f . g ,m C p. f . g , m ∆T = ms ∆h

16. Thermodynamic Analyses-Energy
16
Steam turbine:
wST = (hST,i - hST,o )η G
Pump:
w p = (hp,o - h p,i )ηp
Net combined output:
wnet = ( wGT − wc )ηG + ( wST − w p )
First law efficiency:
ηCC =
wnet
mbiomass LHVbiomass

17. Thermodynamic Analyses-Exergy
17
Thermo-mechanical exergy:
ei = (hi - ho ) - To (si - so )
Where,
hi - ho =
Ti
∫
To
c p dT
P
dT
si - so = ∫ c p
- Rln i
To
T
P
o
Ti
Fuel exergy:
Ex fuel =mbiomass LHVβ
biomass
Where multiplication factor-β ,
1.044 +0.0160
β=
H
O
H
- 0.34493 (1+0.0531 )
C
C
C
O
1 - 0.4124
C

18. Thermodynamic Analyses-Exergy
18
Specific chemical exergy of producer gas :
X1 + X 2
X1
ch
eH 2 +
+X 3 +X 4 +X 5 +X 6
X1 + X 2
X2
ch
eCO +
+X3 +X 4 +X5 +X 6
X1 + X 2
ch
ebiomass =
X5
ch
eCH 4
+X3 +X 4 +X5 +X 6
Exergetic efficiency:
nexergetic =
Where ,
Exout
Exin
Exin = ∑ ( Exi )in + ∑ (Wi )in
Exout = ∑ ( Exi )out + ∑ (Wi )out

19. RESULTS AND
DISCUSSIONS

20. Results & Discussions
20
Product gas composition of the gasifier
Parameter
Gas Composition( mole fraction)
H2
CO
CO2
N2
CH4
H2 O
Oxidant-fuel ratio (xOF)
LHV of product gas mixture
Gasification efficiency
Unit
Value
%
%
%
%
%
%
MJ/kg
%
20.88
26.78
6.88
40.03
0.3
4.92
1.8
5.44
80.45

21. Results & Discussions
21
Base case performance of the plant
Parameter
Unit
Value
Biomass flow rate
kg/hr
23.4
Topping cycle pressure ratio
-
4
C
1000
kW
30
%
75
ST cycle output
kW
15.56
Combined work output
kW
45.56
Plant efficiency
%
37.383
GT inlet temperature
GT cycle output
Percentage of valve opening to CHX
0

22. Results & Discussions
22
17.0
38.5
16.5
Plant efficiency (%)
38.0
37.5
37.0
36.5
36.0
0
TIT=900 C
0
TIT=1000 C
0
TIT=1100 C
35.5
35.0
4
6
8
10
12
14
16
Topping cycle pressure ratio
Fig: Variation of plant efficiency with
GT block pressure ratio.
Steam turbine electrical output (kW)
39.0
16.0
15.5
15.0
14.5
14.0
0
TIT=900 C
0
TIT=1000 C
0
TIT=1100 C
13.5
13.0
2
4
6
8
10
12
14
16
Topping cycle pressure ratio
Fig: Variation of steam turbine
electrical output with GT block
pressure ratio.

23. Results & Discussions
0
20
18
16
14
12
10
4
6
8
10
12
14
16
Topping cycle pressure ratio
Fig: Variation of specific air flow by
mass with pressure ratio.
CHX (tube side) specefic air flow by volume (m
22
3
TIT=900 C
0
TIT=1000 C
0
TIT=1100 C
24
GT cycle specefic air flow by mass (kg/kWh)
/kWh)
23
20
0
TIT=900 C
0
TIT=1000 C
0
TIT=1100 C
18
16
14
12
10
8
6
4
2
2
4
6
8
10
12
14
16
Topping cycle pressure ratio
Fig: Variation of CHX (tube side)
specific air flow by volume with
pressure ratio.

24. Results & Discussions
24
Percentage of valve opening to CHX
Turbine Inlet Temperature
(0C)
Percentage of valve opening
(%)
900
1000
1100
58
75
97

25. Results & Discussions
25
4.22%
7.72%
35.86%
6.62%
3.92%
1.35%
3.43%
17.84%
19.04%
CHX
Gasifier
Condenser
Compressor
Stack
GT &ST
HRSG
Auxaliaries
Useful
Fig: Component exergy loss and useful exergy of the
plant at TIT=10000C.

26. Results & Discussions
26
120
0
TIT=900 C
0
TIT=1000 C
0
TIT=1100 C
Exergetic efficiency (%)
100
80
60
40
20
0
1
2
3
4
1: CHX 2: Gasifier 3: HRSG 4: GT & ST
Fig: Exergetic efficiency of the plant components at different TIT’s.

27. CONCLUSIONS

28. Conclusions
28
Thermodynamic analyses of a novel configuration (biomass
based indirectly heated combined cycle ) has been carried out in
this paper.
The efficiency of the proposed plant attains a maximum at
particular pressure ratio range (6-9) and individual turbine inlet
temperature (TIT).
For a particular pressure ratio the efficiency value increases at
higher TIT.
Size of the topping cycle components as well as CHX unit
decreases as pressure ratio increases at individual TIT. Also the
size of the said units are getting lowered at higher TIT’s

29. Conclusions
29
Major exergy losses occur at the gasifier, CHX unit, GT & ST
unit and HRSG unit for the plant.
Exergy loss for the other plant components are insignificant.
The exergetic efficiency of the gasifier and the CHX unit are
lower than that of other plant components due to the chemical
reactions takes place at the said units.
The exergy efficiency value of CHX unit is above 90% for the
plant at higher TIT.

30. References
30
1. Syred C., Fick W., Griffiths A.J., Syred N. (2000) Cyclone gasifier and cycle
combustor for the use of biomass derived gas in the operation of a small gas turbine in
co-generation plant, Fuel, 83, pp. 2381-2392.
2. Cycle-Tempo Software, (2012) Release 5 (TU Delft) (Website: http://www.cycletempo.nl/.)
3. Datta A., Ganguli R., Sarkar L. (2010) Energy and exergy analyses of an externally
fired gas turbine (egft), cycle integrated with biomass gasifier for distributed power
generation, Energy, 35, pp. 341-350.
4. Vera D., Jurado F., Mena de B., Schories G. (2011) Comparison between externally
fired gas turbine and gasifier-gas turbine system for the olive oil industry, Energy, 36,
pp. 6720-6730.
5. Barman N.S., Ghosh S., De S. (2012) Gasification of biomass in a fixed bed
downdraft gasifier-A realistic model including tar, Bioresource Technology, 107, pp.
505-511.
6. Ghosh S., De S. (2004) First and second law performance variations of coal
gasification fuel-cell based combined cogeneration plant with varying load, Proceedings
of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy,
pp. 477-485.

31. References
31
7. Roy P.C. (2013) Role of biomass energy for sustainable development of rural India:
case studies, International Journal of Emerging Technology and Advanced Engineering,
Special Issue 3, ICERTSD 2013, pp. 577-582.
8. Energy Statistics (2012, Nineteenth Issue), Ministry of Statistics and Programme
Implementation, Govt. of India, 2012 (Website:
http://mospi.nic.in/Mospi_New/site/home.aspx).
9. Datta A., Mondal S., Dutta Gupta S. (2008) Perspective for the direct firing of
biomass as a supplementary fuel in combined cycle power plants, International Journal
of Energy Research, 32, pp. 1241-1257.
10. Soltani S., Mahamoudi S.M.S., Yari M., Rosen M.A. (2013) Thermodynamic
analyses of an externally fired gas turbine combined cycle integrated with biomass
gasification plant, Energy Conversion and Management, 70, pp. 107-115.
11. Fracnco A., Giannini N. (2005) Perspective for the use of biomass as a fuel in
combined cycle power plants, International Journal of Thermal Sciences, 44, pp.163177.
12. Bhattacharya A., Manna D., Paul B., Datta A. (2011) Biomass integrated
gasification combined cycle power generation with supplementary biomass firing:
Energy and exergy based performance analysis, Energy, 36, pp. 2599-2610.

32. Pradip Mondal
PhD Scholar
Dept of Mechanical Engineering
Bengal Engineering and Science University, Shibpur
Howrah-711103, West Bengal
e-mail: mondal.pradip87@gmail.com