CFD Combustion Modeling and Validation of a Bagasse Boiler

22 July 2014

Overview

• Why CFD?

• What is Computational Fluid Dynamics (CFD)?

• Industrial Applications

• Case Study – Industrial Watertube Boiler Firing Bagasse

• Combustion

• Turbulence

• Heat transfer

• Validation

• Suction Pyrometer

• Thermal Camera

• Other Example Case Studies

• Conclusion

1. User defines

the problem

4. Solve the

equations

2. Construct

geometry and

mesh

3. Define boundary

conditions and physical

models

5. Interpret

the results

What is Computational Fluid Dynamics (CFD)? ?Process

Dell T7610

workstations

Why CFD?

• Traditional methods

Global combustion reactions

Lumped parameter heat transfer calculations – empirical

simplification

• Not ideal for NEW developments

• Modern standards require a higher

level of detail

• Computer test platform

Industrial Applications

• Improve heat exchanger performance – 3D

• Temperature distribution on walls –stresses

• Flue gas recycling, reduce excess air, control furnace gas

temperatures,

reduce NOX,improve boiler efficiency

• New secondary air systems - increased furnace capacity

• Lower emissions

• Diagnostic tests

• New fuels

• Erosion, fouling, corrosion

• Control

CFD Value Site Data

Superheater outlet temperature 387°C 390°C

Flue CO concentration 214ppm 200-1500ppm

Particle Mass Carry Over 12 725mg/Nm3 12 000mg/Nm3

Case Study – Industrial Watertube Boiler firing bagasse

Superheater Performance

Physics – Combustion / Turbulence

Furnace

Superheater

Air

Fuel

Physics – Heat Transfer

Validation - Suction Pyrometer

SH

Validation - Suction Pyrometer

Suction Pyrometer Data vs CFD

Suction Pyrometer Data vs CFD

Suction Pyrometer Data vs CFD

Species distribution CO and O2

Suction Pyrometer Data vs CFD

240

260

280

300

320

340

360

380

400

420

30 40 50 60 70 80 90 100 110

Ste

am

Te

mp

(d

eg

C)

Load (%)

Superheater Temp vs Load Characteristic

Measurements

CFD

Thermal Camera

Thermal Camera - Front of Superheater

CFD Suction pyrometer

Thermal camera

(R1)

Upper level temperature

in front of superheater

[°C] 1020 1040 1055

Flame Profile CFD vs Camera

nose

nose

Rear Grate Level – Camera vs CFD

Physics – Combustion / Turbulence

• Pilot plant testing

• Model conditions at inlet of

Superheater = critical

• Effect of turbulence on heat

transfer – up to 50% increase

• Why?

• Predicting steam temperature is

not new.

• Cogeneration – higher steam

Temperature = larger superheaters

• More detailed modelling required

Direct Application

More Example Case Studies - Erosion

Conclusion

• CFD = state of the art – combustion modelling

• Advances in computers - accuracy feasible

• Combustion with heat transfer – novel

• IMPERATIVE to understand the physics

of the problem

• Validation = KEY!!!!

• Industrial scale 120MW thermal

(25MW electric) – 28 million cells

• 5 days to solve

THANK YOU