SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Dynamic Simulation of Oxy Combustion in a Pilot Scale CFB Boiler

Hultgren M (Oulu), Lohiniva L (Oulu), Kovács J (FW), Ritvanen J (LUT) & Tourunen A (VTT)

Matias Hultgren

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Aims of the Simulation Study

• 1-D CFB hotloop model: dynamic & steady-state, Matlab/Simulink

• Main process dynamics of oxy-CFB • Model validation with experimental data,

oxy combustion• Preliminary simulations for pilot tests • Modelling purpose:→ Further simulations to understand the

process, air vs. oxy→Combustion control studies with

traditional & advanced control solutionsModified from: Kuivalainen et al. (2009, 11)

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

The Hotloop Model

• 1-D elements with mass & energy balances solved against time• Gas phase heterogenous reactions: C, H & S• Combined energy equation for temperatures• Phases incompressible and have same T, solids Cp constant• Furnace cooling: Tref, Tfur & Tcyc

• Hydrodynamics, combustion & heat transfer: semi-empirical correlations, empirical vertical density profile

• Turbulent conditions → energy dispersion

HOTLOOP

Fuel

Prim./Sec. oxidant

Solid circulation/ash

Cooling parameters

Flue gas flow

Evaporator heat flux

Separator heat flux

Furnace profiles

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

ACFB furnace block, separator & return leg of the hotloop model

5

Furnace profiles

4

heat flux sep

3

heat flux evap wall

2

Flue gas1

time

fluidvelocities

fluid velocities

rleg

fluegas1furout

fluegas

circulation

Separator

U Y

Selector

slmemoJR

S-Function2

Mux

Mux3

fgprop

Goto

Clock

ACFB

10f_kC

9solid control

8T sep wall

7T furn

6T sloped

5T circulation

4qm circulation

3Secondary gas

2Primary gas

1Fuel

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

• File structure:– Dynamic (.mdl) model:

• hotloop module (furnace, gas-solid separator, solids return system) • external gas mixing module (2-stage mixing of input gases)

– Configuration and statefile (.sim) files– m-files: process inputs, simulation & output handling

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Model Validation

• Measured RFG, pure O2 & air as direct inputs• Anthracite & petcoke mass flows from silo weights• One combined fuel flow input, properties calculated• Flue gas O2 good indicator of combustion, sensitivity• Silo measurement inaccuracies & drifting fuel composition→ Fuel flow correction:• Matching FG O2 to measurements• Corrected fuel input for simulations• Model validation with temperatures, CO2, H2O, etc.

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Model Validation: Fuel Correction

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Air & Oxy Steps, Furnace Temperatures

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Outcomes of the Study

• Model successfully validated for oxy-CFB• Focus on process dynamics• Simulations confirmed measurement conclusions

– Step tests– Ramp tests– Switch tests

• Further development:– Improved modelling accuracy– Multifuel approach to counter changes in fuel composition– Air leakage → effect on flue gas concentrations– Temperature levels → furnace cooling– Oxy combustion control testing → importance

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Thank You for Your attention!

Compostilla power station, Spain

CIUDEN 30 MWth oxy combustion and CCS test facility

Modified from: http://www.vtt.fi/files/sites/flexiburncfb/flexiburncfb_poster.pdf

SYSTEMS ENGINEERING LABORATORYMATIAS HULTGREN, 27.01.2012

Picture References

• Hultgren M (2011) Comparative Study of Oxy and Air Combustion on a Pilot CFB Boiler. Oulu, University of Oulu, Department of Process and Environmental Engineering, Systems Engineering Laboratory. 145 s.

• Kuivalainen R, Pikkarainen T, Leino T, Tourunen A (2009) Development of CFB Technology to Provide Flexible Air/Oxy Operation for a Power Plant with CCS. At: The 34th International Technical Conference on Coal Utilization & Fuel Systems, 31.05. – 04.06.2009, Clearwater, Florida, USA [referenced 17.01.2012]. Foster Wheeler Energia Oy, VTT Technical Research Center of Finland. 13 s.

• VTT (date unknown) Development of High Efficiency CFB Technology to Provide Flexible Air/Oxy Operation for Power Plant with CCS [poster presentation]. FLEXI BURN CFB – EU FP7 I 2009-2012 [referenced 17.01.2012]. VTT Technical Research Center of Finland. Availability: http://www.vtt.fi/files/sites/flexiburncfb/flexiburncfb_poster.pdf