black liquir Recovery

8/10/2019 black liquir Recovery

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Recovery Boiler

Modeling

Process Simulation Ltd.


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Develop modeling tools toimprove existing designs

and operating procedures,and to lower carry overand environmental impact

Analyse performance ofdifferent air systems andliquor firing strategies

Objectives


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Introduction

Process and equipment designwas, until recently, based onexperience

Advances in numerical methodsand computer speed andmemory

increased possibility of usingmore scientific methods,

called mathematicalmodeling, for process designand optimization

Computing Hardware Trends

0.1

1

10

100

1000

10000

1980 1985 1990 1995 2000

Memory(MB)

0.1

1

10

100

1000

S eedMIPS

Memory

Speed


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Mathematical Modeling Applications

in Other Industries

Computer

Jet engines Weather

Automotive

Harrier jet


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Equipment Modeling Capabilities:

MatureDevelopingPreliminary

Time

Bark Boiler

BFB Bark Boiler

Hydrocyclone

Head box

DigesterLime kiln

Gasifier

Recovery Boiler

We have active projects on this equipment

>306411


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Client List

Weyerhaeuser USA

Weyerhaeuser Canada

Canfor

Kvaerner

Scott Paper

Anthony Ross Weldwood


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Why Use Modeling?

Recovery Boiler environment is too severe formeasurement

The model provides comprehensive information

throughout the entire boiler at relatively low cost Can evaluate what if scenarios to improve

operation/design

Supplements steam chief and operator knowledge

of recovery boiler operations Assists mill managers in making informed decisions

regarding boiler refits/replacements


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Details of the Recovery Boiler Model

Liquor Combustion Model

Advanced and verified solution algorithm

Black liquor combustion modelDryingPyrolysis CO, CO2, CH4, H2, H2O

Char gasification Gas phase combustion model

Advanced radiation model

Convective section model

Char bed model


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Issues Addressed by the Model

High excess air

CO, CO2, and other emissions Mechanical carryover & plugging

Bed blackouts

Superheater and waterwall tube thermal

stress failures

Boiler stability and capacity


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Input Data Required

Boiler geometry Bed shape

Convective section layout

Air temperature and flow rate at each port

Liquor characteristics


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Model Predictions

Gas species (e.g. H2,O2,N2,CO,CO2,H2O,CH4)

distributions

Gas flow velocity fields

Temperature distributions and heat transferto wall surfaces

Liquor spray combustionand droplettrajectories.

Carryover characteristics


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Model Validation

Water Model Measurements

Full Scale Measurements

Isothermal flow validation

Hot flow validation

Temperature measurements at bullnose

Carryover prediction trends CO emission trends

Velocity measurements

CE Boiler Model

B&W Boiler Model

Different aspects of model resultshave been validated against datafrom operating boilers


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Recovery Boiler Refit Example

High plugging rates High gas temperature

at superheater

Bed growth control

The Issue:

The Objective:

To recommend modifications toair system


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Tertiary Air Ports (20%)

Secondary Air Ports (30%)

Primary Air Ports (50%)

Base Case Modified Air System

Test Case Geometries


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Secondary Air System Problem and Solution

Jets collide

Carryover

Core forms

Secondaryjets

Liquor guns

Jets Interlace

Uniform flow

Secondary

jets



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Primary

V = 30 m/s

50% Air

T = 423 K

M = 46 kg/s

z = 1.2 m

Liquor Guns

HV=15000 kJ/kg

T = 400 K

M = 18 kg/s

z = 7 m

Base

Case

Secondary

V = 85 m/s30% Air

T = 423 K

M = 27.6 kg/s

z = 3 m

Tertiary

20% Air

V = 50 m/s

T = 423 K

M = 18.4 kg/s

z = 10 m

Modified

Air

SystemTertiary

20% Air

V = 50 m/s

T = 423 K

M = 18.4 kg/s

z = 10 m

Secondary

V = 85 m/s30% Air

T = 423 K

M = 27.6 kg/s

z = 3 m

CommonAir/Liquor

System

Data in

Plan View


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1600

1500

1400

1300

1200

1100

1000

900

800

700

600

T[K]

Base Case

1600

1500

1400

1300

1200

1100

1000

900

800

700

600

T[K]

Modified Air System

Temperature Profiles


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Velocity Profiles

16

14

12

10

8

64

2

0

-2

-4

20m/s

UpwardvelocityW [m/s]

Base Case

16

14

12

10

8

64

2

0

-2

-4

20m/s

UpwardvelocityW [m/s]

Modified Air System


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X

Y

Z

X

Y

Z

---- drying

---- pyrolysis

---- char

---- smelt

Fuel Particle Trajectories



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Y

Z

X

200

160

140

120

10080

60

40

20

5

0Modified Air S ystem

Total Carryoverat Superheater0.03%

Carryovermass flux[g/s/m

2]

Y

Z

X

200

160

140

120

100

80

60

40

20

5

0

Carryovermass flux[g/s/m

2]

Base Case

Total Carryoverat Superheater4.06%

Carryover Mass Flux


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0

2

46

8

10

12

14

16

18

20

Base Case

Modified Air System

Water SmeltPyro. Char

Wall

0

5

10

15

20

25

30


InFlight

0

1

2

3

4

5


Carryover

0

3

6

9

12

15


Bed

Black Liquor Particulate Distribution

(% of total liquor input)


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X

Y

Z

O2

0.16

0.14

0.12

0.1

0.08

0.07

0.06

0.05

0.04

0.02

X

Y

Z

O2

0.16

0.14

0.12

0.1

0.08

0.07

0.06

0.05

0.04

0.02

Oxygen Concentration Distribution



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X

Y

Z

CO

0.10.05

0.01

0.005

0.003

0.001

0.0005

0.0001

5E-05

X

Y

Z

CO

0.10.05

0.01

0.005

0.003

0.001

0.0005

0.0001

5E-05

Carbon Monoxide Concentration Distribution



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Conclusions

The modified air system:

Larger air ports provides better jet penetration.

Increases gas mixing

Breaks up the vertical air core

Significantly reduces plugging rates.

Reduces gas temperatures at superheater

In general, modeling:

Provides detailed data to facilitate efficientoperation of Recovery Boilers.

Helps mill managers make informed decisions

regarding boiler refits/replacements

Documents

black liquir Recovery