Reducing of kinetic scheme for syngas oxidation at high pressure and elevated temperature Bolshova T.A., Shmakov A.G., Yakimov S.A., Knyazkov D.A., Korobeinichev O.P. Institute of Chemical Kinetics & Combustion, Novosibirsk Russia 7th International Seminar on Flame Structure, July , 2011

Introduction SYNGAS, components: H 2 + CO Production technology: –Gasification of fossil fuels (mineral and brown coal) –Processing of natural gas and natural hydrocarbons (catalytic and thermal methods) –Gasification of combustible wastes Spheres of application: –Power engineering –Chemical engineering Problems: –Fire safety –Toxicity –Development of high-tech devices for power chemical engineering (turbines, reactors, etc.)

The scheme of power station with the integrated cycle of gasification. Introduction

The gas turbine Introduction P 0 - up to 40 atm, T 0 - up to 700 о С

Research Objectives Development of the reduced reaction mechanism for syngas oxidation at temperature Т 0 = K and pressure Р=10-30 bar Validation of the proposed reduced mechanism by comparing the simulated burning rate with experimental literature data

Characteristics of Unburnt Gases The fraction of CO in the fuel : а=[CO]/([CO]+[H 2 ])= and 0.75 The dilution ratio: D=[O 2 ]/([O 2 ]+[N 2 ])=0.209 (for fuel/air mixtures). Equivalence ratio was : f=([CO]+[H 2 ])/2[O 2 ], where [O 2 ], [N 2 ], [CO] and [H 2 ] - are concentration of oxygen, nitrogen, carbon monoxide and hydrogen respectively.

Background Literature experimental data

Mechanism for modeling H 2, CO oxidation. Background

Model Sun H., Yang S.I., Jomaas G., Law C.K. (Proceedings of the Combustion Institute 31, 2007) H 2 O 2 H 2 O H O OH HO 2 H 2 O 2 CO CO 2 HCO CH 2 O CH 2 OH AR N 2 HE 16 SPECIES and 48 REACTIONS

R1 H+O2=O+OHR2 O+H2=H+OH R3 O+H2=H+OHR4 H2+OH=H2O+H R9 H2+H2O=H+H+H2OR13 O+H+M=OH+M R14 H+OH+M=H2O+MR15 H+O2(+M)=HO2(+M) R19 H2+O2=HO2+HR21 HO2+H=OH+OH R22 HO2+O=O2+OHR23 HO2+OH=H2O+O2 R1 H+O2=O+OHR2 O+H2=H+OH R3 O+H2=H+OHR4 H2+OH=H2O+H R5 OH+OH=O+H2OR13 O+H+M=OH+M R14 H+OH+M=H2O+MR15 H+O2(+M)=HO2(+M) R19 H2+O2=HO2+H R21 HO2+H=OH+OH R23 HO2+OH=H2O+O2R24 HO2+OH=H2O+O2 R27 H2O2(+M)=OH+OH(+M)R36 CO+OH=CO2+H R37 CO+OH=CO2+HR38 CO+OH=CO2+H The sensitivity coefficients of burning velocity to the reactions rate constants for H 2 /CO/air flame, р=10, 20, 30 bar CO 5% CO 50% T 0 =300 K f=1 R1 H+O 2 =O+OH R15 H+O 2 (+M)=HO 2 (+M) R36+R37+R38 CO+OH=CO 2 +H

The sensitivity coefficients of burning velocity to the reactions rate constants for H 2 /CO/air flame, р= 20 bar  =0.5, T 0 =300 and 700 K,  =0.75 R1 H+O2=O+OH R3 O+H2=H+OH R4 H2+OH=H2O+H R14 H+OH+M=H2O+M R15 H+O2(+M)=HO2(+M) R19 H2+O2=HO2+H R21 HO2+H=OH+OH R36 CO+OH=CO2+H R37 CO+OH=CO2+H R38 CO+OH=CO2+H A rise of initial temperature does not influence on key reactions set

The sensitivity coefficients of burning velocity to the reactions rate constants for H 2 /CO/air flame, р= 20 bar  =0.5, T 0 =300 and 700 K,  =3.5 The most appreciable changes of sensitivity coefficients as T 0 rises from 300 to 700 K are observed in the rich flame for reactions R4 (in 8 times) and R15 (in 2 times). R4 H 2 +OH=H 2 O+H R15 H+O 2 (+M)=HO 2 (+M)

The sensitivity coefficients of burning velocity to the reactions rate constants for H 2 /CO/air flame, T 0 =300K,  =0.5, р= 20 bar R39 HCO+M=H+CO+M R40 HCO+H=CO+H 2 R1 H+O 2 =O+OH R19 H 2 +O 2 =HO 2 +H R21 HO 2 +H=OH+OH The value of sensitivity coefficient to rate constants of the reactions depends on equivalence ratio .

The rate of production of H in H 2 /CO/air flame, T 0 =700K,  =0.5, р= 20 atm.  =0.3  =4.5 R4 H 2 +OH=H 2 O+H R3 H2O+H2=H+OH R37+R38 CO+OH=CO 2 +H R1 H+O 2 =O+OH R15 H+O 2 (+M)=HO 2 (+M) R4 H 2 +OH=H 2 O+H R3 H 2 O+H 2 =H+OH R1 H+O 2 =O+OH R15 H+O 2 (+M)=HO 2 (+M) R21 HO 2 +H=OH+OH

The rate of production of CO in H 2 /CO/air flame, T 0 =700K,  =0.5, р= 20 atm.  =0.3  =12 R36+R37+R38 CO+OH=CO 2 +H R39 HCO+M=H+CO+M R35 CO+HO 2 =CO 2 +OH R47 HCO+O 2 =CO+HO 2

Н 2 Н+OH H 2 O+H +O +OH 74% 25% CO 2 2 +H +O +OH 94% 5% Н 2 Н+OH H 2 O+H +O +OH 77% 23% CO 2 2 +H +O +OH 85% 6% +H HCO 9% Н 2 Н+OH H 2 O+H +O +OH 83% 17% CO 2 2 +H +O +OH 56% 5% +H HCO 39%  =0.75 =2.0=2.0 =4.0=4.0 The main pathways for H 2 and CO consumption in H 2 /CO/air flame, р= 20 atm, T 0 =300K,  =0.5

A reduced reaction mechanism for oxidation of H 2 /CO/O 2 № Reartion A*A*nEa*Ea* S1.H+O 2 =O+OH6.73e S2.O+H 2 =H+OH5.06E S3.H 2 +OH=H 2 O+H1.168E S4.OH+OH=O+H 2 O3.348e S5.H+H+M=H 2 +M7.00E S6.H+OH+M=H 2 O+M2.212E S7.H+O 2 (+M)=HO 2 (+M)4.65E S8.H 2 +O 2 =HO 2 +H7.395E S9.HO 2 +H=OH+OH6.0E S10.HO 2 +OH=H 2 O+O 2 5E S11.CO+O+M=CO 2 +M3.0E S12.CO+OH=CO 2 +H1.8E S13.HCO+M=H+CO+M4.0E S14.HCO+H=CO+H E * – In: cm 3, mole, s, cal; rate constant expressed as k=A T n exp (-Ea/RT) 13 species (H 2, O 2, H 2 O, H, O, OH, HO 2, CO, CO 2, HCO, Ar, He and N 2 ) and 14 reactions

Flame speed of CO/H 2 /Air mixtures as function of equivalence ratio at P=10-30 atm,  =0.05, 0.5, Thin lines: model of Sun H. et al., lines with symbols: reduced mechanism Testing of the reduced mechanism

Flame speed of CO/H 2 /O 2 /He mixtures as function of equivalence ratio Testing of the reduced mechanism Triangles: experimental data of Sun et al., dashed line: mechanism of Sun et al., circles: reduced mechanism P=20 bar P=10 bar

Testing of the reduced mechanism Flame speed of CO/H 2 /O 2 /He mixtures as function of equivalence ratio P=40 bar Triangles: experimental data of Sun et al., circles: reduced mechanism

Diamonds and triangles : experimental data of Natarajan et al, circles: reduced mechanism Testing of the reduced mechanism Flame speed of CO/H 2 /O 2 /He mixtures as function as function of  at P=15 atm, T 0 =300K. (  =[CO]/([CO]+[H 2 ])  =0.6  =0.8

Lines: mechanism of Sun et al., symbols: reduced mechanism Testing of the reduced mechanism Temperature and concentration profiles in CO/H 2 /Air flame (  =0.5, Р=20 atm, T 0 =300K,  =1)

Summary 1.Developed reduced reaction mechanism for syngas oxidation (14 steps, 13 species) satisfactorily predicts burning velocity at P=10-30 atm, T 0 = K, and  0.05  Developed reduced reaction mechanism for syngas oxidation (14 steps, 13 species) satisfactorily predicts burning velocity at P=10-30 atm, T 0 = K, and  = 0.05  In H 2 / CO mixtures with с  =0.05 the reaction from H 2 oxidation were shown to be key reactions; at  =0.5 and higher the role of reaction CO+OH=CO2+H appreciably increases. 3.Pressure rise from 10 to 30 atm was not shown to influence the set of key reactions. 4.HCO-involving reactions were shown to play a noticeable role in sybgas oxidation only in rich mixtures or at high CO content in syngas.

Siemens Ltd. The research was performed under financial support of Siemens Ltd. under agreement #035-СT/2008 Thank you!

Flammability concentration limits for CO/H2/Air mixtures as functions of initial temperature (  =0.5, p=1 bar) calculated using mechanism [1] - circles, reduced mechanism (var. #9) - triangles and literature data [Wierzba I., 2005] - squares. Testing of the reduced mechanism

O 2 +3H 2 = 2H 2 O+2H(I)* 2H+M  H 2 +M (II)* CO+H 2 O=CO 2 +H 2 (III)* * Wang W., Rogg, B., and Williams F.A. in Reduced Kinetic Mechanism for Application in Combustion Systems (Peters, N., Rogg, B., Eds.), Springer-Verlag, Berlin, p.48, 1993, pp Проверка механизма горения сингаза на основе брутто-реакций Зависимость скорости реакций от температуры трех эффективных стадий для пламени СО/H 2 /Air (a=0.5, f=1.0, P=20 atm, T 0 =300K, D=0.209).

Аррениусовские параметры констант скоростей реакций для трех эффективных стадий в пламени СО/H2/Air (a=0.5, P=20 atm, T 0 =300K, D=0.209) f IIIIII AE a, cal/molA A Set#    Set#    Set#    Set#    Проверка механизма горения сингаза на основе брутто-реакций Скорость распространения пламени СО/H 2 /Air (a=0.5, P=20 atm, T 0 =300K, D=0.209) от f, рассчитанная с использованием детального механизма реакций Sun H et al, сокращенного механизма и трехстадийного механизма реакций на основе эфективных стадий с различными наборами кинетических параметров констант скоростей

Механизм реакций окисления H 2 /CO/O 2 * размерность констант скоростей см 3, моль, сек, кал, К, k = AT n exp(-E a /RT). NoРеакцияA*A*nEa*Ea* 1H + O 2 = O + OH 6.73  O + H 2 = H + OH 3.82  O + H 2 = H + OH 8.79  H 2 + OH = H 2 O + H2.17E OH + OH = O + H 2 O3.35E H 2 + M = H + H + M2.23E H 2 + H 2 = H + H + H  H 2 + N 2 = H + H + N  H 2 + H 2 O = H + H + H 2 O 8.43  O + O + M = O 2 + M 6.16  O + O + AR = O 2 + AR 1.89  O + O + HE = O 2 + HE 1.89  O + H + M = OH + M 4.71  H + OH + M = H 2 O + M 2.21  H + O 2 (+M) = HO 2 (+M) k ∞ 4.65  H + O 2 (+Ar) = HO 2 (+Ar) k ∞ 4.65  H + O 2 (+He) = HO 2 (+He) k ∞ 4.65  H + O 2 (+H 2 O) = HO 2 (+H 2 O) k ∞ 4.65  H 2 + O 2 = HO 2 + H 7.40  HO 2 + H = H 2 O + O 1.44  HO 2 + H = OH + OH 6.00  HO 2 + O = O 2 + OH 1.63  HO 2 + OH = H 2 O + O 2 l.00  HO 2 + OH = H 2 O + O  NoРеакцияA*A*nEa*Ea* 25HO 2 + HO 2 = H 2 O 2 + O  HO 2 + HO 2 = H 2 O 2 + O  H 2 O 2 (+M) = OH + OH(+M) k∞ 3.00  H 2 O 2 + H = HO 2 + H  H 2 O 2 + H = H 2 O + OH 1.02  H 2 O 2 + O = OH + HO  H 2 O 2 + OH = HO 2 + H 2 O 1.70  H 2 O 2 + OH = HO 2 + H 2 O 2.00  CO + O(+M) = CO 2 (+M) 3.00  CO + O 2 = CO 2 + O 2.53  CO + HO 2 = CO 2 + OH 1.15  CO + OH = CO 2 + H l.00  CO + OH = CO 2 + H 9.00  CO + OH = CO 2 + H 1.01  HCO + M = H + CO + M 4.00  HCO + H = CO + H  HCO + O = CO + OH 3.00  HCO + O = CO 2 + H 3.00  HCO + OH = CO + H 2 O 1.02  HCO + HO 2 = CO 2 + OH + H 3.00  HCO + HCO = H 2 + CO + CO 3.01  HCO + HCO = CH 2 O + CO 2.70  HCO + O 2 = CO + HO E  HCO + O 2 = CO + HO  Sun H., Yang S.I., Jomaas G., Law C.K., High-pressure laminar flame speeds and kinetic modeling of carbon monoxide/hydrogen combustion Proceedings of the Combustion Institute 31 (2007) 439–446