Environmental Engineering Reference
In-Depth Information
Reaction mercury model
The reaction mercury model was not excluded in the FLUENT6.2 software. It was
imperative to introduce a sub-model to FLUENT6.2 by providing the database of
mercury components concerned. General speaking, the main forms of mercury
during coal combustion were gaseous Hg 0 , HgCl 2 , HgO and HgCl. According to
US-NIST and the NASA database, the thermodynamic parameters such as thermal
conductivity, specific heat volume , enthalpy, entropy, viscosity were calculated and
generated from the thermo.db database by FITDAT tool of CHEMKIN3.7. Flow
and energy processes in the furnace had been simulated by standard CFD tech-
niques, incorporating a sub-mercury model. Predictions had been validated to a
reasonable degree of agreement against real data taken at the full-scale boiler. Then
thermo.db as sub-model was injected into the turbulence reaction model. The nu-
merical simulation of the 410 tons/h tangentially coal-fired furnace was presented
using a combined simulation method with the sub-reaction mercury model.
HG HG 1 G 300.000 1500.000 1500.00 1
0.24511171E+01 0.00000000E+00 0.00000000E+00 0.00000000E+00 0.00000000E+00 2
-0.38972327E+03-0.41051658E+01 0.13584232E+01 0.14054719E-01-0.31908790E-04 3
0.26032205E-07-0.71216394E-11-0.79587207E+03-0.15716494E+01 4
HGCL HG 1CL 1 G 300.000 1500.000 1500.00 1
0.46327644E+01 0.00000000E+00 0.00000000E+00 0.00000000E+00 0.00000000E+00 2
0.79568299E+04 0.46911341E+01 0.39866342E+01 0.19907714E-02-0.27720864E-05 3
0.18025373E-08-0.43188065E-12 0.81795871E+04 0.80676115E+01 4
HGCL2 CL 2HG 1 G 0300.00 5000.00 1000.00 1
0.07251461E+02 0.03082143E-02-0.14475549E-06 0.02958294E-09-0.02201214E-13 2
-0.01981231E+06-0.06061846E+02 0.06249130E+02 0.03221572E-01-0.02109668E-04 3
-0.07713536E-08 0.08526178E-11-0.01958242E+06-0.10156133E+01 4
HGO HG 1O 1 G 0300.00 5000.00 1000.00 1
0.04192035E+02 0.04176083E-02-0.16589761E-06 0.03318184E-09-0.02429647E-13 2
0.03713109E+05 0.04621457E+02 0.03235991E+02 0.03067170E-01-0.01992628E-04 3
-0.04378690E-08 0.06018340E-11 0.03950193E+05 0.09495331E+02 4
The thermo.db was provided from CHEMKIN3.7 and injected into FLUENT6.2
code, which included a series of thermodynamic coefficients, the thermal
conductivity ( T ), the specific heat capacity Cp ( T ), the enthalpy H ( T ), the entropy
S ( T ), the viscosity ( T ) and the other thermodynamic parameters, which were fitted
polynomially from the standard thermodynamic databases from NIST and NASA.
The coefficients could be generated by FITDAT tool of CHEMKIN3.7. Several
major forms of mercury, Hg, HgCl, HgCl 2 , HgO were taken into account. The
reaction model was, as with pulverized coal combustion, the equilibrium reaction
model. The typical simulation of temperature, velocity, component distributions of
pulverized coal combustion in a three dimensional model at full scale were
presented at first, regardless of Hg and Cl species contained in the coal. Because
both are trace elements, mercury concentration in the furnace is at a magnitude of
1×10 -9 at the most, chlorine is about 500 ppm. Unfortunately, the mercury
sub-model could not cope with the FLUENT6.2 code after the initial simulation
converged. This led to a severe truncation error resulting from the limitation of
memory in the computer. There was an effective alternative way to have the Hg
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