Certified for Integrated Management System (ISO9001, 14000, 18000), SA 8000, ISMS 27000.
DTP S
Energy efficiency at core.
Dahanu Thermal Power Plant (DTPS)
Background : Function of ID Fan
Thermal power plant has several fans such as Induced draft (ID) fans, Forced draft (FD) Fans, Primary air fans (PA fans). These fans contribute to significant auxiliary power consumption. ID fans alone contribute to about 12% of total auxiliary power consumption
The function of Induced Draft fan is to suck the gases out of furnaces and push them into the stack. Boiler is provided with two nos. of Induced Draft Fans.
Each ID fan is provided with regulating damper control and scoop control for controlling the loading on fans, Inlet/Outlet gates for isolation to facilitate startup/maintenance of fan.
Background : Function of ID Fan MAIN
HYD. COUP AIR
AUX GD-5
GD-9
TE PT 3no s O2 ANA. GD-1
FROM ECO
PT
GD-13 O2 ANA.
MAIN
GD-6
GD-15
GD-10 HYD. COUP
CO ANA.
ID FANB
TE
PT
AUX O2 ANA.
GD-2
TE
PT
GD-3
AIR
GD-19
EP-A
GD-7
GD11
GD-18 PT
APH-B TE 3nos
GD-17
PT
APH-A
TE 3nos
ID FANA
TE
EP-B GD-14
GD-4 PT
TE 3no s
GD-8
GD-12
FLUE GAS PATH
GD-16
GD-20
S T A C K
Technical specification of ID Fan General specification:
Application
: ID Fan
No per boiler
: Two
Type : NDZV 33 Sidor
Medium handle : Flue gas
Orientation
: 45 degree inclined suction horizontal delivery
Fan Design rating:
Capacity
: 258 cu.m /sec
Total head developed
: 496 mmwc
Temp. of medium
: 145 degree C
Speed
: 701 RPM (Max at 100% scoop)
Type of Regulation:Speed & damper Drive Motor:
Motor Make
: BHEL- Haridwar
Rating
: 1850 KW
Speed
: 745 RPM
ENERGY CONSERVATION OPPORTUNITIES FAN LAWS
Flow ∞ Speed
Q1 Q2
=
N 1
SP1
N 2
SP 2
2
N = N 1
kW 1
2
kW 2
3
N = N 1
2
Principle of Hydraulic Coupling
The ID fans are controlled with VFC control.
The variable fluid coupling works on the principle of hydrodynamics.
It consists of an impeller and rotor(runner) enclosed in a Casing. The impeller is connected to the prime mover, while the rotor is connected to the driven machine. The coupling is filled with fluid, usually mineral oil. The speed of the driven equipment is varied by varying the quantity of fluid Supplied between the impeller and the runner.
Principle of Hydraulic Coupling P Pump impeller T Turbine wheel S Scoop chamber 1. Main lube oil pump 2. Input shaft 3. Output shaft 4. Gear 5. Working oil pump 6. Scoop tube (adjustable) 7. Scoop tube control (VEHS)
Hydraulic Coupling Losses:There are two Types of Losses of power in VFC: Hydraulic Losses Mechanical Losses
Mechanical Losses (W. R. T. Speed) )
R( d e e p S
M P
Hydraulic Losses (W.R.T. Slip)
)
%( pi l S
Losses (KW)
Hydraulic Coupling Losses: SLIP
A difference between input & output speed is essential in a fluid coupling in order to enable it to transmit torque. Difference between input & output speed is normally expressed as percentage of the input speed & refereed to as slip.
(I/P speed- O/P speed) Slip % =
x100 I/P speed
Hyd. Loss : Heat Loss Method Total heat loss (KW) =
ECW flow in m3/h x ECW Temp. Gain in °C x 1000 860 Kcal/hr
Hydraulic loss:-
SR. NO.
PARAMETER
UNIT
UNIT-1
UNIT-2
ID FAN-1A ID FAN-1B
AVERAGE
ID FAN-2A
ID FAN-2B
A
Cooling Water Flow of Working Oil Cooler
M3/Hr
104
78
89
105
94
B
Temp. Rise of CW Across WO Cooler
Deg. Celsius
2.2
2.6
3
2.8
2.65
C
Scoop Position
%
55
54
53
54
54
D = (A*B*1000) 860
Total Heat Loss in VFC
KW
266.04
235.81
310.46
341.861
288.54
Validation
SLIP Loss Method
O/P Power I/P Power =
x100 1 - Slip
Validation of Hydraulic loss by slip loss calculation
SR. No.
A
PARAMETER
Motor I/P Power
UNIT
UNIT-1
UNIT-2
AVERAGE
ID FAN1A
ID FAN1B
ID FAN2A
ID FAN2B
KW
1224.00
1243.00
1257.00
1289.00
1253.25
B
ID fan Motor Efficiency
%
96.00
96.00
96.00
96.00
96.00
C
Scoop Position
%
55.00
54.00
53.00
54.00
54.00
D
Motor Speed
RPM
733.00
734.00
731.80
733.50
733.08
E
Fan Speed
RPM
574.00
576.10
568.20
573.00
572.83
%
21.69
21.51
22.36
21.88
21.86
VFC, I/L Power
KW
1175.04
1193.28
1206.72
1237.44
1203.12
Fan Shaft I/L Power
KW
920.15
936.58
936.95
966.67
940.09
VFC Loss
KW
254.89
256.70
269.77
270.77
263.03
F = 100 * (F-G) F
Slip
G = A*B 100 H=G*(1-F/100)
I=G-H
Efficiency Aspect
Efficiency of variable fluid coupling is= 1- slip. Fan driving system efficiency can be improved by regulating fan speed by digital Variable Frequency Drive(VFD) instead of VFC.
Fan driving system efficiency η driving= η motor* η VFC = η motor*(1-slip)
MOTOR
I/P Power = P
ηmotor= 96%
VFC
ηVFC= 1-slip
FAN
I/P Power = P * ηmotor % * ηVFC % at Fan Shaft
Present Efficiency Calculation
Average Slip of VFC =21.86%.
SR. NO.
PARAMETER
UNIT
ηold
A
ηmotor
%
96
B
Slip
%
21.86
C=(1-B/100)100
ηvfc
%
78.14
D=A*C/100
ηdriving
%
75.0144
Recommendation
Installing a Variable Frequency Drive for this variation in flow requirements will result in substantial energy savings. The speed of the fan can be varied to attain the desired flow.
There are two options: 1. To install variable frequency drives for the ID fans with VFC in place. In this case, fan speed is varied by VFD keeping VFC scoop 100% open.Design VFC slip at sc oop 100%: - 3.4%
SR. NO.
PARAMETER
UNIT
ηnew
A
ηmotor
%
96
B
Slip
%
3.4
C=(1-B/100)100
ηvfc
%
96.6
D=A*C/100
ηdriving
%
92.736
2. To install variable frequency drives for the ID fans & remove VFC . In this case VFC slip loss is nil since slip =0
SR. NO.
PARAMETER
UNIT
ηold
A
ηmotor
%
96
D=A*C/100
ηdriving
%
96
Cost-Benefits: (New Efficiency-Old efficiency) % Energy Saving = ------------------------------------------ * 100 New efficiency
SR. NO.
PARAMETER
A
AVERAGE MOTOR I/P POWER
B
ηold
C
UNIT A %
Value 1253.25 75.01 VFD WITH VFC OPERATING AT FULL SPEED (SCOOP=100%)
VFD WITHOUT VFC
ηnew
%
92.73
96
D=100*((C-B)/C)
ENERGY SAVING
%
19.10
21.86
E=A*C/100
KW SAVING
239.48
274.02
KW
In DTPS, there are 4no. ID fans. Above energy saving calculation is for one fan. If cost of unit- 3.50 Rs/KWH & annual Operating Hrs. =8200 Hr, benefit & simple payback period is shown in the following table:
SR. NO.
PARAMETER
UNIT
KW
Value VFD WITH VFC \OPERATING AT FULL SPEED(SCOOP=100%)
