boiler combustion optimization
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NTPC O&M Conference 2016
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Our Target:Boiler Combustion Optimization
with
Get a better view intothe combustion of your boiler !
Presentation
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Boiler Combustion Optimization
UBCOn-line measurement of the unburned carbon in the fly ash
CoalOn-line measurement of the coal mass flow between the mill and the burner
Air/GasOn-line flow measurement of preheated excess air or flue gas
FlowModification of ductwork and flow dampers for better distribution
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VW Golf 1, 70 hp, fuel consumption 10.5 l/100km
Fuel combustion in the old days
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VW Golf 7, 115 hp, fuel consumption 4.3 l/100km
Fuel combustion nowadays
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Difference between Carburetor and Electronic Fuel Injection EFI:
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EFI
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Pressure Drop
Two Phase Flow measurement and control
Coal density damper
Coal Feeder
No individual control
Coal flow
Individual air flowwindbox pressure
Difference between feeder- and windbox controlled combustion, and Directly Controlled Fuel Injection
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Burner excess air ratio of 0.7NOx conversion rate is at minimum
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Individual measurementand control of coal massflow and velocity as wellas air mass flow online measurement
of UBC in fly ash
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Combustion optimization tuning strategy :
•
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Technoligy 1. Coal Mass Flow Balance
•
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CoalMeasurement Principle
Microwave measurement:
2 sensors in one pipe are used to measure the coal concentration over the FULL cross sectional area of the pipe
Easy installation:
The sensors are mounted through easy drill and tap holes (14x1 mm)
Transmitter
Receiver
In case of roping:
cover full
cross section
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Coal flow balancing and measurement systems
Automated Coal Flow Dampers Coal Flow Sensors
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Density Dampers on Classifiers
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Coal Density Dampers
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Adjustment of coal flow velocity
Coal velocity dampers
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Automatic balancing system is successful attaining and maintaining fuel distribution
-25%-20%-15%-10%-5%0%5%
10%15%
Baseline ManualTune
AutoTune
Bur
ner C
oal F
low
Bia
s
Burner C1 Burner C2 Burner C3 Burner C4 Burner C5
Fuel Balancing PLC
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Sensor 2
Air Duct or Pipe
Sensor 1S=const.
ExampleS=54 cmT=26 ms
w=20,8 m/s (average velocity of the air !)
Signal Sensor 1
Signal Sensor 2
“Signature”
Y(t)=X(t-T)X(t)
Time T
correlation “Correlation”
T=-26 ms Optimum ofcorrelation
AirMeasurement Principle: Velocity
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AIR SystemAir
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Technology 2: Individual air flow measurement
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Combustion Engineering CE-RO Burner
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Measurement in the tight anulus of a new Low NOx 80 MW burner
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McON Air measurment for SA, TA
•
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T-Fired Register Burner Retrofit
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Technology 3: Online unburned carbon measurement
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A B
90% separation
90% separation
90% separation
90% separation 90% of the total fly ash
9,0%
0,9%
0,09%
Measurement Cabinet4 Sensors
SensorControl Box
SensorControl Box
SensorControl Box
SensorControl Box
Sensor 1
Sensor 2
Sensor 3
Sensor 4
Digital Input SignalsRelease signals per channelif necessary
PromeconAshFLO Sensors
4-20 mA SignalsUnburned Carbon Signals
0600 1200 1800 2400
3
4
5
6
UBC [%]
Microwave Generator
Microwave Receiver
PLC Unit
Power Supply
Signal Converter
Control Room
Touch ScreenMan Machine Interface
Fault Messages
Maximum Distance: 70 meters
Precipitator
Application of Sensors
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MECONTROL UBC Measurement points
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DCFI results on a boiler
Boiler
Bunker Feed
Coal bunker
Four pulverizers
Burner Air
FD Fan
Burner pipes
Coal
PA
Primary Air
Secondary Air
16 BrennerAirCoal
Coal psa
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Important rules for efficient combustion
Directly Controled Fuel Injection
- Primary air flow needs to be measured and Aircontrolled to a tolerance of 3% of full scale value
- Fuel velocities shall always be higher than 23 m/sec Coal
- velocities shall be balanced to 2 m/sec Coal
- Mill outlet temperature shall be consistent andcontrolled temp to a tolerance of 5 K
- The pulsation rate of the coal mass flow shall be Coalbelow 5% (variance of the actual value to the mean value)
- The coal mass flow distribution shall be within Coala tolerance of 5 %
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Important rules for efficient combustion
- Secondary air distribution controlled Airto a tolerance of 5%
- Overfire air distribution controlled Airto a tolerance of 5%
- Swirl air settings controlled Airto a tolerance of 5%
- Excess air level reduced to the point UBCwhere UBC is below max taget value(usually 5%)
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Velocities
1000
1200
1400
1600
1800
2000
220009
:59
10:1
910
:40
11:0
011
:20
11:4
012
:00
12:2
012
:41
13:0
113
:21
13:4
114
:01
14:2
114
:41
cm/s
ec
Pipe 1Pipe 2Pipe 3Pipe 4
Low velocities cause pulsations in the coal flowResults Coal
Vertical piping
Control of minimum coal velocities
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Control of minimum coal velocities
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Velocities
Velocity Balance
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Example Pipe Arrangement
Coal Valve
Adjustment of coal flow velocity
Adjustment of coal velocities
Coal
Splitter Box
Pulverizer
Burner
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Here a large velocity spread has been corrected by a variable orifice
Adjustment of coal velocities
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Adjustment of mass flow
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Same coal mass flow to every burner
Coal distribution beforethe adjustment
Coal distribution after the adjustment
Adjustment of coal mass flows
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Typical Problems with delta P measurement
15% deviation
Adjustment of SA and OFA
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Windbox Modificationusing CFD modelsAdjustment of SA and OFA
Example:
Partitioning the winbox inlet in order to get a better measurement path for a group of 2 burners per partition.
Better air flow control through better measurement
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O2 set point reduction
Adjustment of O2 set point with UBC value
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UBC Optimisation Results
2
3
4
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8
Time
UB
C[w
t.-%
];
O2
[vol
.-%]
200
220
240
260
280
300
320
340
360
380
400
Seco
ndar
y ai
r x 1
000
[m³/h
r] S
TP
O2 right duct
UBC Basis: ash = 3.6 %
Secondary air Basis: n = 1.259
O2 left duct
Trial run at “Wedel” power plant
Excess Air Reduction
Resulting efficiency increase:0.42 %-pts !
= -0.08 %-ptsUBC: Cabs = -2 %-pts
Excess air: nabs= 7.6 %-pts = 0.5 %-pts
Adjustment of O2 set point with UBC value
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Modification of SA Controls
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NOx optimization
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Boiler efficiency increase
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