advanced process modeling improves efficiency process simulations ltd. 206-2386 east mall,...

Advanced Process ModelingImproves Efficiency

Process Simulations Ltd.206-2386 East Mall, Vancouver, BC, V6T 1Z3

www.psl.bc.ca

Dave Stropky and Jerry Yuan

Contents

Introduction to Process Modeling

Examples Recovery and Power Boilers Lime Kilns Aerated Wastewater Lagoons Precipitators

Process Modeling

Principle of Conservation

MassMomentum

Energy…….

IN = OUT

ININ

OUTOUT

OUTOUT3D CFD

CFD Modeling Examples

Building StructuresJet engines

Weather

Aircraft

Industrial Equipment

Process Modeling

IN IN PROGRESSPROGRESS

INDUSTRIALINDUSTRIALAPPLICATIONAPPLICATION

Literature review

Plant\Mill interaction

Process knowledge

Commitment of industry

Physical model

Numerical model

Model development

Model validation

Industrial testing

Parametric studies

Problem Solving

Model proposed retrofits

Equipment Optimization

Cost Reduction

INITIALINITIALSTAGESTAGE

Pulp and Paper Modeling Applications

RecoveryandBark

Boilers

Analyze the existing air and fuel system Improve gas mixing and combustion effectiveness Lower excess air necessary for complete combustion Minimize particulate carryover and unburned char Minimize emissions of CO2, CO, TSR, and NOx Increase the range of operational conditions Improve overall thermal efficiency Optimize firing strategies for different loads/fuels Increase the capacity of the boiler Improve the stability of the boiler Minimize the danger of bed blackouts Minimize the danger of waterwall tube failure Provide valuable operational information for mill personnel

Boilers

Boilers

Air System Evaluation

B u rn er P o rts

O v e rfire A irD is tr ib u to r P or ts U n d er D is t. P o rts

U n d erg ra te A ir

Va llian t B a rk B o ile r

0.150.10.050.040.030.020.010.0010

O 2massfraction

0.050.040.030.020.010.0050.0010

CH 4massfraction 1600

150014001300120011001000900800700600

Temp.T [oC]

July 24 CaseGas 1,430 lb/hrHog Fuel 157,000 lb/hr

101123

170

105125

160

020406080

100120140160180

Feb 4 Feb 12 July 24

NO

x E

mis

sio

n (lb

/hr) pre dic te d

m easured

Boilers

Emission Control

Boilers

Efficiency Improvements

Parameter Units 2002 2003 Comments/ChangeDry-Solids Load KPPH 59.63 63.92 7.2% increase

TRS PPM 3.7 3.1 16.2% decreaseChemical Reduction Efficiency % 81 90.8 12.1% increase

Carryover physical test Grams/5-minutes 164.7 49.8 69.8% decreaseFiring % Solids % 68.2 67.8Steam Temp Deg-F 727 728

# Chill & Blows # 3 1 66.6% decreaseChill & Blow Downtime HRS 31 12 61.3% decrease

Steam Flow KPPH 229.4 229.8 Low press P/S air closed Natural Gas Flow MSCF/HR 25.11 1.67 93.3% decrease

GL Density % 18.3 18.9 3.2% increaseFurnace outlet Flue Gas Temp Deg-F 1609.9 1438.4 10.6% decrease

Lime Kilns

Reduce fuel consumption. Improve Efficiency Adjust primary/secondary air and fuel ratios and burner

settings to maximize kiln efficiency Identify and eliminate thermal hot spots that lead to

reduced brick liner lifetime Develop strategies for reducing ring formation Identify and fix problems with kiln performance due to

hood shape and secondary air ports location and size Evaluate NCG injection alternatives - optimize injection Evaluate alternative fuels Minimize emissions Optimize heat transfer to mud Improve combustion stability through retrofit and

adjustment of the burner and burner structure

Lime Kilns

Lime KilnsGas Temperature

Brick Temperature

0

50

100

150

200

250

300

0 50 100 150 200 250 300Axial Distance (ft)

T( C

)

ModelShell Scan

Lime Kilns

Distance from Kiln Hood [m]

Tem

pera

ture

ofG

asan

dLi

me

[K]

Volu

me

Frac

tion

ofO

2,C

O2,

H2O

inFl

usG

as[v

ol%

]

Em

issi

onof

NO

inFl

ueG

as[p

pmv]

Mas

sFr

actio

nof

Lim

eC

ompo

nent

s[w

t%]

0 20 40 60 80 100

500

1000

1500

2000

0

5

10

15

20

25

30

35

40

010

020

030

040

050

0

0

10

20

30

40

50

60

70

80

90

100

Feed

End

Fire

End

Tgas

CaCO3

CaO

Tck

NO

CO2

O2

H2O

Predicted Axial Profile Data

Lime KilnsHeat Loss Through Shell 3.0 MW

Natural gas flow rate 0.6291 kg/sNatural gas high heating value 54.45 MJ/kgChemical enthalpy from natural gas 34.26 MW Product temperature 1116.5 KNatural gas composition by wt% Product CaCO3 flowrate 0.213 kg/sCO2 0.37% Product CaO flowrate 4.358 kg/sCH4 97.92% Product Inerts flowrate 0.17 kg/sN2 1.71% Physical enthalpy from product 3.60 MWFuel temperature 310.9 K Energy absorbed by calcination 13.06 MWPhysical enthalpy from natural gas 0.05 MW Total enthalpy from product 16.66 MWTotal enthalpy from natural gas 34.31 MW

Total Energy In 38.43 MWProduct Energy Out + Heat Loss 19.66 MW

CaCO3 flow to kiln 7.995 kg/s Energy taken away by flue gas 18.77 MWInerts flow to kiln 0.166 kg/sMaterial temperature to kiln 616.5 K Flue gas CO2 mass flowrate 5.120 kg/sPhysical enthalpy from feed 2.77 MW Flue gas N2 mass flowrate 9.447 kg/s

Flue gas H2O mass flowrate 1.607 kg/sFlue gas O2 mass flowrate 0.354 kg/s

Air composition by wt% Physical enthalpy from flue gas 18.77 MWO2 22.59% Flue gas energy balance check 0.00 MWN2 75.64% Flue Gas Temperature 1029.2 KH2O 1.77%Discharge grate air flowrate 0.602 kg/sDischarge grate air temperature 522.0 KDischarge grate air physical enthalpy 0.18 MWHood leakage air flowrate 8.465 kg/sHood leakage air temperature 310.9 KHood leakage air physical enthalpy 0.70 MWBurner axial air flowrate 2.651 kg/sBurner axial air temperature 366.5 KBurner axial air physical enthalpy 0.37 MWBurner spin air flowrate 0.468 kg/sBurner spin air temperature 322.0 KBurner spin air physical enthalpy 0.04 MWNCG air flowrate 0.289 kg/sNCG air temperature 400.0 KNCG air physical enthalpy 0.05 MWTotal enthalpy air 1.35 MW

Kiln Efficiency 7.09 GJ / tonne

Product

Fuel

Feed

Air

AeratedWastewater

Lagoons

Aerated Wastewater Lagoons

Improve efficiency of waste treatment (BOD removal) by optimizing number and placement of mechanical aerators.

Reduce power consumption from mechanical aerators by either minimizing the number of aerators required or reducing the power load per aerator.

Reduce nutrient supplementation (added phosphorus and nitrogen)

Reduce dredging frequencyImprove design of lagoon basins

Aerated Wastewater Lagoons

Hydraulic Flowand

Residence Time

Side View

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0 5 10 15 20 25 30 35 40

T(Days)

E(T)

Aerated Wastewater Lagoons

Predicted RTD Curves

Tpeak / Tmean = 0.74Tmedian / Tmean = 0.91

Aerated Wastewater Lagoons

Predicted Biology

Precipitators

Precipitators

Improve precipitator efficiency by redistributing gas flow

Improve duct designsOptimize porous distribution on

perforate plates and locations of platesOptimize baffle and vane designs

Precipitators

V/Vavg [-]: -0.25 -0.15 -0.05 0.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 1.05 1.15 1.25 1.35 1.45 1.55 1.65 1.75 1.85 1.95

Normalized Axial Velocity on a Vertical SectionNew Design 1 of Outlet Perforated Plate

Precipitators

-10%

0%

10%

20%

30%

40%

50%

60%

70%

80%

Outlet Velocity Profile Factor

% R

educ

tion

in P

artic

ulat

e E

mis

sion

s

Modified InletUnmodified Inlet

Conclusions The performance of many pulp and paper

processes is governed by the fluid dynamics, heat transfer, and chemical reactions in the associated equipment.

Much of this equipment was and still is designed and troubleshot using traditional methods. We know what goes in and comes out, but we normally don’t know clearly and in detail what is going on inside.

Advanced three-dimensional process modeling provides a clearer picture of the process dynamics. This knowledge helps mill engineers and operators improve process efficiency and reduce costs.