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

5

6

7

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