Detailed Chemical Kinetic Modelling of Pollutant Conversion in Flue Gases from Oxycoal Planty

R.K. Robinson and R.P. Lindstedt

Thermofluids Section, Department of Mechanical Engineering,Imperial College London, Exhibition Road,p g , ,London SW7 2AZ

OutlineOutline

Motivation

Model Development

Calculation of Thermodynamic Data

Results, Sensitivities and Product Distributions

Conclusions

Future Work and Acknowledgements

MotivationMotivation

Carbon Capture and Storage (CCS) aims to capture CO2 emissions from large scale energy generators. Strongly corrosive impurities such as oxides f it d l h d t b t d f th h tof nitrogen and sulphur need to be separated from other exhaust gases.

Experimental methodologies to remove these impurities have been developed[1,2] However the chemistry behind these processes is poorlydeveloped . However the chemistry behind these processes is poorly understood.

The current work outlines computational methods that attempt to model the relevant conversion processes and the distribution of subsequent products in flue gases.

1. White V. and Allam R.J., Purification of Oxyfuel-Derived CO2 for Sequestration or EOR, Proceeding of the 8th International Conference on Greenhouse Gas Control Technologies, Trondheim, Norway, (2006).2. Allam R.J., White V. and Miller J., Purification of Carbon Dioxide, US Patent 7,416,716.

BackgroundBackground

The sulphur chemistry is based on detailed high temperature chemical p y g pkinetics obtained from the following studies:

F.G. Cerru, A. Kronenburg and R.P. Lindstedt “A systematically reduced mechanism for sulphur oxidation” Proc Combust Inst 30 (2005) 1227-1235sulphur oxidation Proc. Combust. Inst. 30 (2005) 1227 1235.

F.G. Cerru, A. Kronenburg and R.P. Lindstedt “Systematically reduced chemical mechanisms for sulphur oxidation and pyrolysis” Combust. Flame 146 (2006) 437-455.

The nitrogen chemistry is based on the following studies:

Lindstedt, R.P., Lockwood, F.C. and Selim, M. A., “Detailed Kinetic Modelling of Chemistry and Temperature Effects on Ammonia Oxidation” Combust. Sci. and Technol., 99 (1994), 253-276.

Lindstedt, R.P., Lockwood, F.C. and Selim, M.A., 'Detailed Kinetic Study of Ammonia Oxidation', Combust. Sci. Technol., 108, (1995) 231-254.

In both cases subsequent updates have been performed and validated in combustion applications.

BackgroundBackground

Work has taken place in 3 key areas:p y

Current kinetic models of combustion involving both sulphur and nitrogen species have been extended to low temperature ranges via th dditi f k i d tithe addition of key species and reactions.

An aqueous phase mechanism has been developed to model reactions occurring in solution A mass transfer coefficient has beenreactions occurring in solution. A mass transfer coefficient has been estimated to allow movement of species between the gaseous and aqueous phases.

Accurate quantum mechanical methods have been used to update thermodynamic data for species involved in the model and to calculate new data for aqueous species by taking into account the enthalpy of dissolution.

Model DevelopmentModel Development

The original Sulphur mechanism featured 12 sulphur containing species The original Sulphur mechanism featured 12 sulphur containing species and 70 reversible reactions. The nitrogen mechanism featured 21 species and 95 reversible chemical reactions.

The above mechanisms are here combined with hydrocarbon chemistry for C1-C2 species that permit the additional interactions with burnt gas products such as CO, CO2 and H2O as well as any remaining 2 2hydrocarbon fragments.

16 additional reactions for nitrogen and sulphur gas phase chemistry.

10 mass transfer rates added to allow movement of species between gaseous and aqueous phases.

8 h ti d t t b i h 8 aqueous phase reaction used to create a basic aqueous phase mechanism.

Model DevelopmentModel Development

Additions to reaction Mechanism rates taken from NIST Chemical Kinetics Database or CAPRAM Aqueous Mechanism for Troposheric chemistry or extrapolated there from.

Gaseous Phase Additions with rates shown in modified Arrhenius formPRODUCTS REACTANTS A n Ea

NH3 + NO2 = HNO2 + NH2 ; 2.4510E-03 3.410E+00 1.250E+05;NO2 + N3 = N2O + N2O ; 1.2040E+08 0.000E+00 0.000E+00;NO2 + N3 N2 + NO + NO ; 3 6130E+08 0 000E+00 0 000E+00;NO2 + N3 = N2 + NO + NO ; 3.6130E+08 0.000E+00 0.000E+00; O2 + N3 = N2O + NO ; 3.6130E+01 0.000E+00 0.000E+00;N3 + O = N2 + NO ; 6.7450E+09 0.000E+00 0.000E+00;N3 + N3 = N2 + N2 + N2 ; 9.0330E+08 0.000E+00 0.000E+00;O2 + NO = NO3 ; 3.4030E-16 -1.750E+00 0.000E+00;NO2 + O + M NO3 + M 4 0990E 07 1 500E+00 0 000E+00NO2 + O + M = NO3 + M ; 4.0990E-07 -1.500E+00 0.000E+00;NO2 + O = NO3 ; 3.5240E+09 0.240E+00 0.000E+00;NO2 + NO3 = N2O5 ; 3.7300E+07 0.600E+00 0.000E+00;NO + NO2 = N2O3 ; 1.6050E+06 0.000E+00 0.000E+00;N2O3 + H2O = HNO2 + HNO2 ; 1.2900E+07 0.000E+00 3.717E+04;N2O5 H2O HNO3 HNO3 5 1000E 05 0 000E 00 0 000E 00N2O5 + H2O = HNO3 + HNO3 ; 5.1000E-05 0.000E+00 0.000E+00;NO2 + NO2 = N2O4 ; 6.0220E+05 0.000E+00 0.000E+00;H2O + NO + NO2 = HNO2 + HNO2 ; 5.1530E-10 0.000E+00 0.000E+00;SO3 + H2O = H2SO4 ; 7.2270E+05 0.000E+00 0.000E+00;

Model DevelopmentModel Development

Mass Transfer Rates between Gaseous and Aqueous Phase taken to be 0.01

PRODUCTS REACTANTS A n Ea

kmol m-3 s-1 after sensitivity analysis performed.

Basics Aqueous Phase Mechanism with rates shown in modified Arrhenius form

PRODUCTS REACTANTS A n Ea

SO2 = SO2(A) ; 0.010E+00 0.000E+00 0.000E+00;NO2 = NO2(A ; 0.010E+00 0.000E+00 0.000E+00;NO = NO(A) ; 0.010E+00 0.000E+00 0.000E+00;HNO3 = HNO3(A) ; 0.010E+00 0.000E+00 0.000E+00;HNO2 = HNO2(A) ; 0.010E+00 0.000E+00 0.000E+00;NO3 = NO3(A) ; 0.010E+00 0.000E+00 0.000E+00;N2O5 = N2O5(A) ; 0.010E+00 0.000E+00 0.000E+00;N2O3 = N2O3(A) ; 0.010E+00 0.000E+00 0.000E+00;N2O4 = N2O4(A) ; 0.010E+00 0.000E+00 0.000E+00;H2SO4 H2SO4(A) 0 010E+00 0 000E+00 0 000E+00H2SO4 = H2SO4(A) ; 0.010E+00 0.000E+00 0.000E+00;SO2(A) + H2O(L) = H2SO3(A) ; 6.270E+04 0.000E+00 0.000E+00;NO2(A + NO2(A + H2O(L) = HNO2(A) + HNO3(A) ; 1.000E+08 0.000E+00 0.000E+00;HNO2(A) + HNO2(A) + HNO2(A) = HNO3(A) + NO(A) + NO(A) + H2O(L); 6.000E+00 0.000E+00 0.000E+00;N2O5(A) + H2O(L) = HNO3(A) + HNO3(A) ; 5.100E-05 0.000E+00 0.000E+00;N2O4(A) + H2O(L) = HNO2(A) + HNO3(A) ; 5.100E-05 0.000E+00 0.000E+00;N2O4(A) + H2O(L) HNO2(A) + HNO3(A) ; 5.100E 05 0.000E+00 0.000E+00;HNO2(A) + OH(A) = NO2(A + H2O(L) ; 1.000E+09 0.000E+00 0.000E+00;NO(A) + NO2(A + H2O(L) = HNO2(A) + HNO2(A) ; 1.000E+08 0.000E+00 0.000E+00;NO2(A + NO2(A + NO2(A +H2O(L)= HNO3(A) + HNO3(A) + NO(A) ; 1.000E+08 0.000E+00 0.000E+00;

Calculation Method for Thermodynamic dataCalculation Method for Thermodynamic data

Molecular Mechanics Mi i i ti d

Atomization Energies, E th l i d

High Accuracy Q tMinimisation and

Conformational Analysis used to locate starting

structure

Enthalpies and Vibration Frequencies produced in G3B3 log

file

Quantum Mechanics

G3B3/G3MPB3 Energy

Calculation

Program locTorsion ran to locate all

DFT Quantum Mechanics

Program scanCalc ran to harvest internal rotation

data fitran to locate all internal rotations

and create input files

Mechanics used to scan and analyse

Internal Rotations

data, fit V = ½ ∑Vn(1 – cos(nθ)) and calculate IR symmetry

numbers and Moments of Interia

Program polyScript ran to harvest data from G3B3 and scanCalc log files calculate

7 Term JANAF Polynomials

Statistical Mechanics Package PAC 99 usedscanCalc log files, calculate

Enthalpies of Formation and Moments of Inertia, and

produce input for next stage

Polynomials produced by regression of

calculated data

Package PAC 99 used to calculate

thermodynamic values from 200K to 6000K

Examples of NO Thermodynamic DataExamples of NOx Thermodynamic Data

Thermodynamic data calculated for species where data were not Thermodynamic data calculated for species where data were notavailable or required updating and fitted to 7 term JANAF polynomials.

For aqueous species enthalpy of dissolution were taken into account bymodifying the enthalpy of formation at 298K.

NO2(Aq)Calculated Data N2O3 Calculated Data

∆fH298 22.6 kJ/mol

S298 239.9 J/mol/K

C 36 9 kJ/mol

∆fH298 81.7 kJ/mol

S298 317.0 J/mol/K

C 69 2 kJ/molCp298 36.9 kJ/mol Cp298 69.2 kJ/mol

HNO2(A) 200K-6000K REF : R.ROBINSON 03-Dec-08

5.83337654E+00 3.92942470E-03 -1.49885436E-06 2.43940583E-10 -1.45404150E-14-1.64746315E+04 -3.02996870E+00 4.73508766E+00 6.07796919E-03 -2.03586709E-06-9.22492080E-10 6.38649372E-13 -1.61106404E+04 2.90221746E+00

N2O3 200K-6000K REF : G3B3 R.ROBINSON 16-Dec-088.75695849E+00 3.70515651E-03 -1.41680841E-06 2.34798620E-10 -1.42777213E-14

6.73047701E+03 -1.35522821E+01 4.90534181E+00 1.63782898E-02 -2.10621083E-051.70161360E-08 -5.97183185E-12 7.79013682E+03 6.09886939E+00

Examples of NO + SO Thermodynamic DataExamples of NOx + SOx Thermodynamic Data

HNO2 Calculated Data

∆fH298 -76.7 kJ/mol

S 249 3 J/ l/K

HNO2(Aq) Calculated Data

∆fH298 -120.1 kJ/mol

S 249 3 J/ l/KS298 249.3 J/mol/K

Cp298 45.4 kJ/mol

S298 249.3 J/mol/K

Cp298 45.4 kJ/mol

SO2 Calculated Data

∆H 296 8 kJ/ l

SO2(Aq)Calculated Data

∆H 323 8 kJ/ l∆fH298 -296.8 kJ/mol

S298 248.2 J/mol/K

Cp298 39.9 kJ/mol

∆fH298 -323.8 kJ/mol

S298 248.2 J/mol/K

Cp298 39.9 kJ/molp298 p298

Results Experiment 1 Conversion EvolutionResults : Experiment 1 - Conversion Evolution

Conditions : Pressure - 2 7 Atmospheres Temperature - 300 KConditions : Pressure - 2.7 Atmospheres Temperature - 300 K

Species ppm %

SO2 9 81E+02 0 10% 0 9

1

SO2 9.81E+02 0.10%

NO 3.22E+02 0.03%

NO2 3.58E+01 0.00% 0.7

0.8

0.9

O2 5.50E+04 5.50%

CO 2.00E+02 0.02%

CO2 8.34E+05 82.35% 0.4

0.5

0.6

Con

vers

ion

NH3 1.00E+04 1.00%

N2 9.00E+04 9.00% 0.2

0.3

%

SO2NOxExperimental SO2H2O 1.00E+04 1.00%

H2O Liquid 1.00E+04 1.00% 0

0.1

0 50 100 150 200 250Time (s)

Experimental SO2Experimental NOx

Results Experiment 1 Mass Transfer SensitivityResults : Experiment 1 – Mass Transfer Sensitivity

0.91

0 40.50.60.70.8

ersi

on

00.10.20.30.4

% C

onve

SO2 Mass Transfer x5SO2 Mass Transfer 0.01 kmol3 m3 s-1SO2 Mass Transfer x 0.2

0 50 100 150 200 250Time (s)

0.80.9

1

0.30.40.50.60.7

% C

onve

rsio

n

00.10.20 3

0 50 100 150 200 250

%

Time (s)

NOx Mass Transfer x5NOx Mass Transfer 0.01 kmol3 m3 s-1NOx Mass Transfer x 0.2

Results Experiment 1 NO Ratio EvolutionResults : Experiment 1 – NOx Ratio Evolution

The Ratio of NO to NO2 is known to change from approximately 9:1 to 3:1 after thecompressor/receiver the current model reproduces this affect.

0.9

1

0.7

0.8

0.4

0.5

0.6

Con

vers

ion NO

NO2 Experimental NOExperimental NO2

0.2

0.3

0.4

%

0

0.1

0 50 100 150 200 250Time (s)

Results Experiment 1 NO Ratio Sensitivity Results : Experiment 1 – NOx Ratio Sensitivity

NO2 is more readily absorbed into the aqueous phase due its larger negative enthalpyof dissolution, therefore the ratio of NO to NO2 influences conversion time for NOx.

0 9

1

0.7

0.8

0.9

0.4

0.5

0.6

% C

onve

rsio

n

0.2

0.3

0%

90%-NO 10%-NO275% NO 25% NO2

0

0.1

0 50 100 150 200 250Time (s)

75%-NO 25%-NO250%-NO 50%-NO2

Results Experiment 1 Pressure Sensitivity

NOx conversion also pressure dependent as higher pressures lead to greater conversion

Results : Experiment 1 – Pressure Sensitivity

from NO to NO2 in the gaseous phase.

0.9

1

0.7

0.8

n

0.4

0.5

0.6

% C

onve

rsio

n

0.2

0.3

SO2 All PressuresNOx 1 BarNO 3 B

0

0.1

0 50 100 150 200 250Time (s)

NOx 3 BarNOx 7 bar

Results Experiment 2 Conversion EvolutionResults : Experiment 2 - Conversion Evolution

Conditions : Pressure - 5 Atmospheres Temperature - 300 Kp p

Species ppm %

SO2 7.61E+02 0.08%0 9

1

NO 2.99E+02 0.03%

NO2 3.32E+01 0.00%

O2 5 50E+04 5 50%

0.7

0.8

0.9

O2 5.50E+04 5.50%

CO 2.00E+02 0.02%

CO2 8.34E+05 83.37% 0.4

0.5

0.6

% C

onve

rsio

n

NH3 0.00E+00 0.00%

N2 9.00E+04 9.00%

H2O 9.98E+03 1.00% 0 1

0.2

0.3

%

SO2NoxExperimental SO2

H2O Liquid 9.98E+03 1.00% 0

0.1

0 100 200 300 400 500Time (s)

Experimental NOx

Results Experiment 2 NO Ratio EvolutionResults : Experiment 2 – NOx Ratio Evolution

The Ratio of NO to NO2 is known to change from approximately 9:1 to 3:1 after thecompressor/receiver ,the current model reproduces this affect.

0 9

1

0.7

0.8

0.9

0 4

0.5

0.6

Con

vers

ion NO

NO2 Experimental NOExperimental NO2

0.2

0.3

0.4

%

0

0.1

0 50 100 150 200 250 300 350 400 450Time (s)

Results Experiment 2 Product DistributionResults : Experiment 2 – Product Distribution

700

800 NONO2 500

600 NO(A)NO2(A)

300

400

500

600

700

ppm

NO2SO2

300

400

500

ppm

NO2(A)SO2(A)

0

100

200

300

0

100

200

0 100 200 300 4000 100 200 300 400Time (s)

0 100 200 300 400Time (s)

160180200

0 1

0.1

0.1 N2O4N2O4(A)N2O3N2O3(A)

6080

100120140

ppm

HNO2(A)HNO3(A)

0.0

0.0

0.0

0.1pp

mN2O3(A)

02040

0 100 200 300 400Time (s)

HNO3(A)H2SO3(A)H2SO4(A)

0.0

0.0

0 100 200 300 400Time (s)

ConclusionsConclusions

The current work shows that detailed models based on chemical kinetics The current work shows that detailed models based on chemical kineticscan be of significant help in interpreting experimental data.

The approach of not heuristically fitting individual rate constants allowsthe separation of validation and simulation.

Key sensitivities are also identified as part of the modelling process.

SO2 and NOx conversion predominately occurs in the aqueous phase.

NOx conversion residence times are highly dependent on the initial ratioof NO/NO and the pressure of system while the SO conversion is lessof NO/NO2 and the pressure of system while the SO2 conversion is lesspressure dependent.

Any model needs to simulate both gaseous and aqueous phases and they gdiffering conditions of both the compressor and the receiver.

Future Work and AcknowledgementsFuture Work and Acknowledgements

Mass transfer rates need to be considered in more detail, and are likely to varythroughout the apparatus. Rates may be estimated from interfacial areas.

Currently ionic species are modelled as molecules A detailed aqueous phase Currently ionic species are modelled as molecules. A detailed aqueous phasemechanism would include ionic species and the pH of the system.

Expansion of the aqueous phase mechanism in line with current findings.

We would like to thank Air Products and Doosan Babcock for their support. Also Dr.L.Torrente-Murciano and Prof. D.Chadwick, Imperial College, for the experimentaldata.

Results Experiment 3 Conversion EvolutionResults : Experiment 3 - Conversion Evolution

Conditions : Pressure - 5 Atmosphere

Temperature - 300 KSpecies ppm %

0 9

1

SO2 6.22E+02 0.06%

NO 1.70E+01 0.00%

NO2 1.89E+00 0.00% 0.7

0.8

0.9

O2 5.50E+04 5.50%

CO 2.00E+02 0.02%

CO2 8 34E+05 83 42%0.4

0.5

0.6

% C

onve

rsio

n

CO2 8.34E+05 83.42%

NH3 0.00E+00 0.00%

N2 9.00E+04 9.00%0 1

0.2

0.3

%

SO2

H2O 9.98E+03 1.00%

H2O Liquid 9.98E+03 1.00%

0

0.1

0 50 100 150 200 250 300 350 400 450Time (s)

NOx

Results Experiment 3 Product DistributionResults : Experiment 3 – Product Distribution

600

700 NONO2 450

500 NO(A)NO2(A)

300

400

500

600

ppm

SO2

200250300350400

ppm

( )SO2(A)

0

100

200

0 100 200 300 4000

50100150

0 100 200 300 4000 100 200 300 400Time (s)

0 100 200 300 400Time (s)

120140160180

0.0

0.0

0.0 N2O4N2O4(A)N2O3N2O3(A)

406080

100120

ppm

HNO2(A)HNO3(A) 0.0

0.0

0.0

0 0pp

m

02040

0 100 200 300 400Time (s)

HNO3(A)H2SO3(A)H2SO4(A)

0.0

0.0

0 100 200 300 400Time (s)