Monthly Technical Report - University of Texas at...
Transcript of Monthly Technical Report - University of Texas at...
1 AQRP Monthly Technical Report Template Revised January 2011
Monthly Technical Report (Due to AQRP Project Manager on the 8th day of the month following the last day of the reporting period.)
PROJECT TITLE Development of Speciated
Industrial Flare Emission
Inventories for Air Quality
Modeling in Texas
PROJECT
NUMBER
10-022
PROJECT
PARTICIPANTS (Enter all institutions
with Task Orders for
this Project)
Lamar University DATE
SUBMITTED
06/05/11
REPORTING
PERIOD
From: 05/01/11.
To: 05/31/11. REPORT
NUMBER
3
Invoice Number that accompanies this Report: CM5086-3
Amount of funds spent during this reporting period: $5,203.74
Detailed Accomplishments by Task (Include all Task actions conducted during the reporting
month.)
1. Collection of Flare Operation/Design/Performance Data (Task 2, waiting for
Comprehensive flare study final report for flare performance data)
Details given in Appendix A
2. Hardware/Software/Data storage (Task 3)
Details given in Appendix B
3. Combustion Mechanism Generation/Validation (Task 4A & 4B)
Details given in Appendix B
4. Geometry Creation & Boundary Conditions (Task 5A)
Details are given in Appendix C
5. Base Case Modeling (Task 6A)
Details are given in Appendix A
Preliminary Analysis (Include graphs and tables as necessary.)
NA
Data Collected (Include raw and refine data.)
1. Collection of Flare Operation/Design/Performance Data (Task 2, see Appendix A for
details)
Identify Problems or Issues Encountered and Proposed Solutions or Adjustments
See Section of the Progress of the Task Order to Date.
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Goals and Anticipated Issues for the Succeeding Reporting Period
Goals for the next reporting period:
1. Combustion Mechanism Generation & Validation (Task 4A & 4B)
2. CFD Modeling (Cases prescribed in the Model Development Protocol, Task 6A)
3. Model calibration with comprehensive flare study and literature (wind tunnel) data (Task
5D)
Detailed Analysis of the Progress of the Task Order to Date (Discuss the Task Order
schedule, progress being made toward goals of the Work Plan, explanation for any delays in
completing tasks and/or project goals. Provide justification for any milestones completed more
than one (1) month later than projected.)
1. Receipt of the flare test data (input & performance) was delayed for roughly 1 month.
2. Task 6A & 6C will be affected by this delay.
3. Geometry creation was impacted by lack of flare tip details and CFD mesh limitations.
4. Task 6A & 6C will be affected by this issue.
5. All other tasks are on schedule.
Submitted to AQRP by:
Principal Investigator: Daniel H. Chen.
(Printed or Typed)
Appendix A: May Monthly Report for Task 2
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CFD Cases
Both the air and steam based cases are broadly divided in 3 sets, based on the 3 different
Lower Heating values (2100, 600 & 350 BTU/SCF) of the fuel used. Each set further has five
cases, with different vent gas velocity, crosswind and other conditions. These CFD cases are
based on the data provided by AQRP to Lamar University and the details were given in the April
monthly report.
CFD Fluent Simulations: Air based flares
Using the geometry provided in Appendix C, CFD Simulations using FLUENT were started.
Due to unusual high flow rate of air (as air-assist), Case A2.1 was taken as the first/base case.
The conditions for the case A2.1 as provided by AQRP in file “Appendix E Tables E-1,
Comprehensive Flare Study QAPP” were used [1].
Table A.I: Conditions used for Case A2.1
Vent gas velocity 0.1656 m/s
Air-assist Velocity 12.99 m/s
Cross wind Velocity 5.74 m/s
Table A. II: Composition of vent gas- Case A2.1
Vent Gas Composition
Species Mass
Fraction
Propylene 1.00
TNG 0.00
Nitrogen 0.00
CFD Model Parameters
In the CFD simulation package, various types of turbulence and chemistry-turbulence interaction
models are available in CFD packages like FLUENT [2-5]. For the flare simulations the
following models were chosen:
Turbulence: k-Epsilon realizable model
The standard k-Epsilon model is a semi-empirical model based on model transport equations for
the turbulence kinetic energy k and its dissipation rate, Epsilon. The model transport equation
for is derived from the exact equation, while the model transport equation for was obtained
using physical reasoning and bears little resemblance to its mathematically exact counterpart.
In the derivation of the - model, the assumption is that the flow is fully turbulent, and the
effects of molecular viscosity are negligible. The standard - model is therefore valid only
for fully turbulent flows
The term "realizable'' means that the model satisfies certain mathematical constraints on the
Reynolds stresses, consistent with the physics of turbulent flows. Neither the standard -
model nor the RNG - model is realizable.
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This model has been extensively validated for a wide range of flows, including rotating
homogeneous shear flows, free flows including jets and mixing layers, channel and boundary
layer flows, and separated flows. For all these cases, the performance of the model has been
found to be substantially better than that of the standard - model. Especially noteworthy is
the fact that the realizable - model resolves the round-jet anomaly; i.e., it predicts the
spreading rate for axis symmetric jets as well as that for plan jets.
Turbulence-chemistry interaction: Eddy Dissipation Concept Model
The eddy-dissipation-concept (EDC) model is an extension of the eddy-dissipation model to
include detailed chemical mechanisms in turbulent flows. It assumes that reaction occurs in small
turbulent structures, called the fine scales. The length fraction of the fine scales is modeled as
where denotes fine-scale quantities and
= volume fraction constant = 2.1377
= kinematic viscosity
The volume fraction of the fine scales is calculated as . Species are assumed to react in the
fine structures over a time scale
where is a time scale constant equal to 0.4082.
In EDC model, combustion at the fine scales is assumed to occur as a constant pressure reactor,
with initial conditions taken as the current species and temperature in the cell. Reactions proceed
over the time scale , governed by the Arrhenius rates of Equation, and are integrated
numerically using the ISAT algorithm. ISAT can accelerate the chemistry calculations by two to
three orders of magnitude, offering substantial reductions in run-times. The source term in the
conservation equation for the mean species , Equation is modeled as
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where is the fine-scale species mass fraction after reacting over the time .
CFD Solver
During the simulations, the Green-Gauss Cell based solver was used. Apart from that, the
discretization method for Pressure equations was changed from standard to PRESTO!, which is
considered as more robust than the standard model.
Under Relaxation Factors
The under relaxation factors are used to stabilize the convergence behavior of the various
discretized equations like Pressure, Density, Turbulence kinetic energy, Energy etc. Since, the
URFs play an important role; these were changed from time to time, depending on the
convergence stage of the problem.
Case A2.1 Results
The preliminary results of the first case including estimated emissions, flare efficiencies, and
temperature/CO2 mass fraction contours are given as follows:
Emissions
Fuel(C3H6) in 360.17 lb/hr
C3H6 out 3.05 lb/hr
CO2 out 1055.12 lb/hr
C in (as C3H6) 308.72 lb/hr
C out (as CO2) 287.76 lb/hr
The two efficiencies were calculated as:
CFD
Simulations TULSA Tests
DRE 99.15% 97.15%
CE 93.21% 95.54%
Destruction and
Removal
Efficiency
=
C3H6 fed - C3H6 out
C3H6 fed
Combustion
Efficiency =
Carbon out as CO2
Carbon fed as fuel
6 AQRP Monthly Technical Report Template Revised January 2011
Figure A.1: Contours of Static Temperature (K)
Figure A.2: Contours of Static Temperature (K) zoomed near the flare
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Figure A.3: Contours of Mass fraction of CO2
Figure A.4: Contours of Mass fraction of CO2 (zoomed in near the flame)
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References
1) Quality Assurance Project Plan, Texas Commission on Environmental Quality
Comprehensive flare Study Project, PGA No. 582-8-862-45-FY09-04, Tracking No. 2008-81
UT/TCEQ/John Zink).
2) ANSYS FLUENT 6.3 User’s Guide, Chapter 12- Modeling Turbulence, Fluent Inc (2006)
3) T.-H. Shih, W. W. Liou, A. Shabbir, Z. Yang, and J. Zhu, A New - Eddy-Viscosity Model
for High Reynolds Number Turbulent Flows - Model Development and Validation. Computers
Fluids, 24(3):227-238, 1995
4) ANSYS FLUENT 6.3 User’s Guide, Chapter 14: Modeling Species Transport and Finite Rate
Chemistry, Fluent Inc (2006).
5) B. F. Magnussen. On the Structure of Turbulence and a Generalized Eddy Dissipation
Concept for Chemical Reaction in Turbulent Flow. Nineteenth AIAA Meeting, St. Louis, 1981
9 AQRP Monthly Technical Report Template Revised January 2011
Appendix B: May Monthly Report for Tasks 3, 4A, & 4B
Hardware/Software/Data Storage
All the input data received and data generated in this report (e.g., mechanism validation) are
properly stored in Servers/computers at Lamar University. The data will be stored in external
hard drives for three years. As mentioned in the QAPP, the data will include various fluent case
runs and excel files containing data analysis.
Generation of 50-Species Reduced Mechanism with NO2
The full mechanism was reduced based on the strategy of removing the species of least interest.
The species to be removed were identified depending on their effect of mole fractions on the
species of interest. Initially, the mechanism did not have NO2, but NO2 happens to be one of the
important species to be studied for the emissions analysis. To incorporate NO2 in the mechanism,
we analyzed the mole fractions of Ar and its effect on other species. Since Argon is an inert gas
and was in relatively small concentration, it had least effect on the concentrations of species of
interest. We replaced argon with NO2 and corresponding mechanism data was also incorporated.
Evaluation of the Reduced mechanism
The simulation results of the reaction mechanisms were compared at different conditions as
follows:
The initial conditions for the mechanism simulation were:
Equivalence ratio of fuel to oxidizer 0.5, 1.0, 1.5
Reactor temperature 1700 K
There were three mechanisms under study, viz.
1. Full Mechanism (USC I + GRI) having 93 species
2. Reduced mechanism having 50 species without NO2
3. Reduced mechanism having 50 species with NO2
10 AQRP Monthly Technical Report Template Revised January 2011
The species in these mechanisms are as follows:
Mechanism Number
of
Species
Species list
Full
Mechanism
(USC I + GRI)
93 H2,H,O,O2,OH,H2O,HO2,H2O2,C,CH,CH2,CH2*,CH3,CH4,CO,CO2
,HCO,CH2O,CH2OH,CH3O,CH3OH, C2H,C2H2, H2CC,C2H3,C2H4,
C2H5,C2H6,HCCO, CH2CO, HCCOH, C2O, CH2CHO, CH3CHO,
CH3CO, C3H2, C3H3, pC3H4, aC3H4, cC3H4, aC3H5, CH3CCH2,
CH3CHCH, C3H6, C2H3CHO, C3H7, nC3H7, iC3H7, C3H8, C4H,
C4H2, H2C4O, n-C4H3, i-C4H3, C4H4, n-C4H5, i-C4H5, C4H6,
C4H612, C4H7, C4H81, C6H2, C6H3, l-C6H4, c-C6H4, A1,A1-,
C6H5O, C6H5OH, C5H6, C5H5, C5H4O, C5H4OH, C5H5O, N, NH,
NH2, NH3, NNH, NO, NO2, N2O, HNO, CN, HCN, H2CN, HCNN,
HCNO, HOCN, HNCO, NCO, AR, N2
Reduced
mechanism
without NO2
50 H2, H, O, O2, OH, H2O, HO2, CH, CH2, CH2*,CH3, CH4, CO, CO2,
HCO, CH2O, CH2OH, CH3O, C2H2, H2CC, C2H3, C2H4, C2H5,
C2H6, HCCO, CH2CO, CH2CHO, CH3CHO, C3H3, pC3H4, aC3H4,
aC3H5, C3H6, C3H8, C4H2, n-C4H3, i-C4H3, C4H4, N, NH, NH2,
NO, N2O, HNO, CN, HCN, HNCO, NCO, Ar, N2
Reduced
mechanism
with NO2
50 H2, H, O, O2, OH, H2O, HO2, CH, CH2, CH2*,CH3, CH4, CO, CO2,
HCO, CH2O, CH2OH, CH3O, C2H2, H2CC, C2H3, C2H4, C2H5,
C2H6, HCCO, CH2CO, CH2CHO, CH3CHO, C3H3, pC3H4, aC3H4,
aC3H5, C3H6, C3H8, C4H2, n-C4H3, i-C4H3, C4H4, N, NH, NH2,
NO, N2O, HNO, CN, HCN, HNCO, NCO, NO2, N2
This comparison was done at three different equivalence ratio values 0.5, 1.0, 1.5. The results were studied in terms of Actual error and % error. It was found that at equivalence ratio = 1.0 the mole fractions were close enough to be considered as matching. (Except for the main fuel since the fuel was defined as ethylene). Further comparison was carried out at new values of residence times 0.8 and 1.0
11 AQRP Monthly Technical Report Template Revised January 2011
The plots of mole fractions of species, at various equivalence ratio values are as follows:
* The simulation was carried out considering C2H4 as fuel
* In further simulations, C3H6 will be considered as fuel and the equivalence ratio 0.8 and 1.0
References
(1) Smith, G. P, Golden, G. M, Frenklach, M, Moriarty, N. W, Eiteneer, B, Goldenberg,M,
Bowman, T, Hanson, R. K, Song, S, Gardiner, W. C, Lissianski,V. V and Qin, Z.
(2000).http://www.me.berkeley.edu/gri_mech/. Accessed 03 October 2010.
(2) Wang, H. and Laskin, A. (1998). A comprehensive kinetic model of ethylene and acetylene
oxidation at high temperatures, Combustion Kinetics Laboratory, Document, Internal report.
0.000E+00
5.000E-05
1.000E-04
1.500E-04
2.000E-04
2.500E-04
3.000E-04
Mole fraction CH2O
Mole fraction C2H4
Reduced with NO2, ER=0.5
Full mechanism, ER=0.5
Reduced with NO2, ER=1.0
Full mechanism, ER=1.0
Reduced with NO2, ER=1.5
Full mechanism, ER=1.5
0.000E+00
5.000E-10
1.000E-09
1.500E-09
2.000E-09
2.500E-09
Mole fraction C3H6
0.000E+00
2.000E-04
4.000E-04
6.000E-04
8.000E-04
1.000E-03
1.200E-03
1.400E-03
1.600E-03
1.800E-03
Mole fraction NO
0.000E+00
2.000E-08
4.000E-08
6.000E-08
8.000E-08
1.000E-07
1.200E-07
1.400E-07
1.600E-07
1.800E-07
Mole fraction NO2
0.000E+00
2.000E-02
4.000E-02
6.000E-02
8.000E-02
1.000E-01
1.200E-01
1.400E-01
Mole fraction CO
Mole fraction CO2
12 AQRP Monthly Technical Report Template Revised January 2011
(3) Anuj Bhargava abd Phillip R. Westmoreland, Measured Flame Structure and Kinetics in a
Fuel –Rich Ethylene Flame, COMBUSTION AND FLAME 113: 333-347, 1998
(4) Davis, S. G. and Law, C. K. (1998), "Determination of and Fuel Structure Effects on Laminar
Flame Speeds of C1 to C8 Hydrocarbons", Combustion Science and Technology, 140(1), 427-
449.
(5) R.S.Barlow,A.N.Karpetis, J.H.Frank, J.Y. Chen,”Scalar Profiles and NO formation in
laminar opposed flow partially premixed methane/air flames” Combustion and flame, 2001.
(6) Hai Wang, Xiaoqing You, Ameya V. Joshi, Scott G. Davis, Alexander Laskin, Fokion
Egolfopoulos & Chung K. Law, USC Mech Version II. High-Temperature Combustion
Reaction Model of H2/CO/C1-C4 Compounds. http://ignis.usc.edu/USC_Mech_II.htm, May 2007
13 AQRP Monthly Technical Report Template Revised January 2011
Appendix C: May Monthly Report for Task 5A
Air assisted flare (Geometry & Boundary Conditions, Task 5A)
In order to match the waste gas flow rate the geometry of flare tip has been modified.
However, no change was taken place in computational domain. The finalized geometry contains
the following key features. Domain is made up of 30 m × 30 m enclosed box. The Flare stack is
placed 5 m away from the left of the domain and its height is 10 m. The big domain has been
chosen to consider the entire flame structure.
Fig C.1: Computational Domain
At the left side of domain, the velocity inlet boundary condition is applied, which considers the
effect of cross wind in the computation. At the bottom of the domain, slip wall boundary
condition is applied to simulate a smooth flow. The boundary conditions on all other sides are
given as pressure outlet.
In this simulation the spider shaped burner is considered as given in the comprehensive
flare study document. Rectangular slit is created for waste gas flow to match the exact waste gas
outlet area. Flare tip is divided in three parts:
1. Fuel/waste gas outlet
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2. Air outlet
3. Spider wall
Velocity inlet boundary condition is applied at the flare tip for fuel and air flows and the
rest of the portion is defined as spider wall.
Fig C.2: Flare Stack and Flare Tip
[Ref: Quality assurance project plan Drawing number TCEQ LHTS-24]
15 AQRP Monthly Technical Report Template Revised January 2011
The structure of flare tip is as shown below:
Fig C.3: Computational Domain of the Flare Tip
Meshing:
In this study, Gambit 2.3.16 is used for the meshing. Firstly, the base of the domain is
meshed. Different size functions are used to create structure and linked mesh. Then the meshed
base is extended up to the tip of the flare. The entire volume is meshed using cooper algorithm.
The tip of flare meshed using very refined mesh. Meshing is done in such a way that the aspect
ratio will be equal to one at tip of flare. Total nine spiders are created for fuel outlet. The meshed
tip of flare is shown as below:
Fuel
Outlet
Spider Wall
Air Outlet