Monthly Technical Report - aqrp.ceer.utexas.eduaqrp.ceer.utexas.edu/projectinfo/10-022/10-022 Tech Report Apr 201… · 4. Combustion Mechanism Validation (Task 4A) Details given

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

04/23/11

REPORTING

PERIOD

From: 04/01/11.

To: 04/30/11. REPORT

NUMBER

2

Invoice Number that accompanies this Report: CM5086-2

Amount of funds spent during this reporting period: $0.00

Detailed Accomplishments by Task (Include all Task actions conducted during the reporting

month.)

1. Collection of Flare Operation/Design/Performance Data (Task 2, Limited input data

received, waiting for flare performance data & certain geometry data)

Details given in Appendix A

2. New model development protocol received as a guideline for data needs and modeling

cases. Cases selected and model used are described. (Task 2 & 5A)

Details are given in Appendices A & C.

3. Hardware/Software/Data storage (Task 3)

Details given in Appendix B

4. Combustion Mechanism Validation (Task 4A)

Details given in Appendix B

5. Geometry Creation & Boundary Conditions (Task 5A)

Details are given in Appendix C

6. CFD chemistry model selection, and model parameters (Task 5B)

Details are given in Appendix C

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.

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 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. All other tasks are on schedule.

Submitted to AQRP by:

Principal Investigator: Daniel H. Chen.

(Printed or Typed)


Appendix A: April Monthly Report for Task 2

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.

Table A1 & A2 show different cases to be run for CFD simulations

Table A1: CFD cases for steam-based flares

Test Actual Vent Gas (VG) Flow Rates Vent Gas Actual Steam Flow Rates Wind Vel No. Propylene TNG Nitrogen Total LHV Vel Center Upper Total

lb/hr lb/hr lb/hr lb/hr Btu/scf fps lb/hr lb/hr lb/hr Mph

S1.5 2337.48 0.00 0.00 2337.48 2145.11 1.52 525.87 3794.01 4319.88 8

S1.8 2338.4 0.00 0.00 2338.4 2145.96 1.5 505.87 7044.07 7549.94 8.6

S 1.9 2336.64 0.00 0.00 2336.64 2144.34 1.5 504.91 7939.33 8444.24 8.8

S 2.2 937 0.01 0.00 937.01 2103.14 0.95 541.62 7769.53 8311.14 10.8

S 2.3 937 0.00 0.00 937 2122.5 0.94 539.31 4761.25 5300.56 7.6

S 3.7 191.29 18.95 715.51 925.74 345.54 0.6 0 227.83 227.83 7.1

S 4.1 490.5 44.96 1799.74 2335.2 349.58 2.0 559.94 536.28 1096.22 5.6

S 4.3 485.21 45.05 1801.62 2331.88 346.37 2.0 567.28 1879.5 2446.77 5.2

S 4.3 500.38 46.62 1802.14 2349.14 355.19 2.0 627.77 2447.42 3075.19 6.6

S 7.3 296.76 29.92 1083.58 1410.26 352.77 1.4 515.59 537.91 1053.51 7.9

S 5.2 319.81 33.78 584.67 938.26 595.36 1.0 454.47 1580.38 2034.85 10.2

S 5.3 312.28 31.73 577.98 921.99 589.58 1.0 481.52 782.52 1264.04 9.3

S 5.4 317.61 32.17 579.44 929.22 595.36 1.0 483.73 1220.85 1704.57 10.9

S 5.6 312.17 31.82 577.17 921.16 590.08 1.0 490.6 462.92 953.53 9.6

S 6.1 826.42 79.13 1455.62 2361.16 608.89 1.9 517.78 1002.85 1520.64 8.8


Table A2: CFD cases for air-assisted flare

Test Actual Vent Gas (VG) Flow Rates Vent

Gas Vel

Air Flow Wind Vel No. Propylene TNG Nitrogen Total LHV rate

lb/hr lb/hr lb/hr lb/hr Btu/scf fps lb/hr mph

A1.1 918.88 0 0 918.88 2107.71 1.4 149173 12.7

A2.1 355.02 0 0 355.02 2125.45 0.5 83818 12.8

A2.3 352.14 0 0 352.14 2108.22 0.5 88791 10.1

A2.4 352.87 0 0 352.87 2112.57 0.5 148799 10

A2.5 354.71 0 0 354.71 2123.55 0.5 119580 13.3

A3.1 181.23 18.77 702.55 902.55 338.67 1.9 19387 10.3

A3.3 181.23 18.37 700.6 900.2 333.86 1.9 60121 11.1

A3.6 181.23 18.76 704.18 904.17 337.55 1.9 47494 11.9

A5.2 72.29 7.69 274.41 354.39 342.86 0.8 75139.77 2.1

A5.3 71.26 7.55 271.37 350.18 341.87 0.8 32876.17 2.5

A4.3 298.74 30.3 591.1 920.14 562.91 1.9 66471.69 10.7

A6.1 117.8 11.86 221.21 350.87 583.73 0.7 11403.53 15.9

A6.4 118.06 12.08 221.25 351.4 584.89 0.7 40583.88 14.1

A6.5 117.85 12.08 221.11 351.04 584.44 0.7 56593.85 15.5

A6.6 118.55 12.44 220.68 351.66 588.07 0.7 146294.6 15

* LHV: Lower heating value; TNG: Tulsa natural gas

Tulsa Natural Gas

The composition of the TNG (Tulsa natural gas) will be taken as:

* The John Zink Combustion Handbook (Pg 163)

Reference

Baukal, C.E & Schwartz, R. E., The John Zink Combustion Handbook, p. 163, CRC Press: Boca

Raton, 2001.

Tulsa Natural Gas (Volumetric Composition)*

CH4 93.40% C2H6 2.70%

C3H8 0.60% C4H10 0.20%

CO2 0.70% N2 2.40%


Appendix B: April Monthly Report for Tasks 3 & 4A

Hardware/Software/Data Storage

All purchased servers (1 Dell PowerEdge R710 & 2 Dell PowerEdge R410) in the high

performance cluster have been successfully networked. The purchased FLUENT/CHEMKIN

HPC licenses were also successfully installed for parallel computing.

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.

Existing 50-Species Mechanism Validation

In the research team’s prior work, a reduced chemical kinetic mechanism for the combustion

of C1-C3 hydrocarbons was generated using a novel algorithm developed on the basis of

sensitivity analysis, quasi-steady state, reaction rates and skeletal approach. The reaction

mechanism file was based on a combined mechanism formed using two widely used chemical

kinetic mechanisms i.e. GRI-3.01 and USC

2. A few aspects of natural gas combustion chemistry

are not described by GRI-Mech 3.0; these include soot formation and the chemistry involved in

selective non-catalytic reduction of NO, which may be important in natural gas reburning at

lower temperatures. The USC mechanism (containing 75 species) was optimized for ethylene

combustion reactions, but the absence of NOx producing species in the mechanism was a

shortcoming. To overcome this problem, both reaction mechanisms were combined so as to yield

a mechanism which could satisfy all the above mentioned criteria. The detailed mechanism,

which has 93 species and 600 reactions, was reduced in a step wise manner to 50 species and 337

reactions.

As often seen in the literature, the fidelity of the mechanism was validated against some

laboratory data3. 4

. The key performance indicators used are laminar burner stabilized flames,

laminar flame speeds, adiabatic flame temperatures, ignition delay test. The following initial

results were submitted in the Quality Assurance Project Plan (Pg. 21~23, Figures 5.1a~5.3b).

Laminar Flame Speed vs. Equivalence Ratio for Methane Air Mixture

Laminar Flame Speed vs. Equivalence Ratio for Propylene Air Mixture

Adiabatic Flame Temperature vs. Equivalence Ratio for Methane

Adiabatic Flame Temperature vs. Equivalence Ratio for Ethylene

Ignition Delay vs. Temperature for Methane

Ignition Delay vs. Temperature for Ethylene

Ignition Delay vs. Temperature for Propylene

The inlet experimental conditions for the CHEMKIN simulation are listed in Table B.1.

Results of various key performance indicators (laminar flame speeds, adiabatic flame

temperature, and ignition delay tests) for methane, ethylene and propylene flames show that the

simulation and experimental literature results are in good agreement for light hydrocarbons.

In this month, using the software package CHEMKIN 4.1.1, the fidelity of the mechanism

was further validated against Burner Stabilized flame laboratory data reported in the literatures.

The experimental data is obtained from the work of Bhargava et. al.3. The fuel is a mixture of


ethylene, oxygen and argon with ethylene and argon at equivalence ratio of one. A low-pressure

laminar premixed flame stabilized on a 6.0 cm diameter burner was used in the experiment4. The

CHEMKIN model was supplemented with the measured temperature profile. The simulated

species mole fractions along the length of the flame were extracted and compared with

experimental results. Figure B.1 shows the comparison between simulation and experimental

data of the mole fraction of major species, such as C2H4, CO2 and O2. The experimental mole

fractions have an uncertainty of ±10% for the stable intermediates, and a factor of 2 for radicals4.

The USC/GRI mechanism has an uncertainty of 10% for CO, 4% for CO2, 10% for C2H4, 0.005

(mole fraction) for CH4, and 0.004 (mole fraction) for O2,5,6

. Therefore, a good agreement among

the major species is observed. Figure B.2 shows that the reduced mechanism is even capable of

predicting the generation of formaldehyde (a radical producing species in atmospheric

chemistry), which may be important from environmental aspect, with sufficient accuracy. This

comparison thus validates the reduced mechanism against an important aspect of validation,

burner stabilized flame, for ethylene.

Table B.1: Inlet experimental conditions for the model

Species Inlet Composition of

Fuel Mixture (vol%)

Equivalence

Ratio Initial Pressure (atm)

Methane CH4/O2/Ar

(9.1/18.2/72.7) 1 1.8

Ethylene C2H4/O2/Ar

(1/3/96) 1 1

Propylene C3H6/O2/Ar

(3.17/7.83/89) 1 7.9


Figure B.1: Comparison of the Molar Fraction of Major Species in Burner Stabilized

Flame for C2H4/O2/Ar (phi = 1.9)

Figure B.2: Comparison of Formaldehyde Mole Fraction Data for Burner Stabilized Flame


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.

(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

http://ame-www.usc.edu/personnel/wang/index.shtml

http://www.exponent.com/leaders/bios/scott_davis.asp?employeeID=555

http://www.exponent.com/leaders/bios/scott_davis.asp?employeeID=555

http://ame-www.usc.edu/personnel/egolfopoulos/index.shtml

http://ame-www.usc.edu/personnel/egolfopoulos/index.shtml

http://www.princeton.edu/~cklaw/


Appendix C: April Monthly Report for Tasks 5A & 5B

1. Geometry Creation & Boundary Conditions (Task 5A)

The geometry of the air-assisted flare as well as the computational domain is under

construction. As seen in Fig. C.1, the computational domain has a width of 30m and a height of

30 m. The flare has a stack of 10m and is located at 5m from the upstream of the crosswind. In

this way, a sufficient space can be applied to examine the effect of crosswind on the flare profile.

Great effort has been made to create the geometry of the flare burner. Due to the extreme

complicity of the actual structure, it is impossible to simulate the detailed flow from many small

jet holes. Simplification is made to introduce the waste gas and air flow without sacrificing the

major feature of the burner. Nine Spider legs are created for waste gas outlet. Figure C.2 shows

the tip of the flare burner, and both flow rate and the jet velocity will be matched to the actual

test.

Figure C.1: Computational Domain Figure C.2: Flare Burner

After the computational domain is created, the next step is to generate a mesh. In this

study, Gambit 2.3.16 is used for the meshing. Different size functions are used to create the

mesh. The final meshed geometry contains 0.77 million cells and 0.70 million nodes. The

number of the grids is a result after balancing the computational time and the simulation

uncertainty. Figure C.3 shows the general structure of the grids in different directions.

2. CFD chemistry model selection, and model parameters (Task 5B)

Two types of combustion/chemical reaction models are being considered:

Eddy-dissipation finite-rate model and non-premixed combustion (PDF) model.

Waste Gas

Inlet

Air Inlet


Figure C.3: Representation of three dimensional meshed domain

. 2.1 Eddy-dissipation finite-rate model

When the user chooses to solve conservation equations for chemical

species, FLUENT predicts the local mass fraction of each species, Yi, through the solution of a

convection-diffusion equation for the ith species. This conservation equation takes the following

general form:

(C.1)

where Ri is the net rate of production of species by chemical reaction (described later in this

section) and Si is the rate of creation by addition from the dispersed phase plus any user-defined

sources.

The reaction rates that appear as source terms in Equation-1 are computed in FLUENT by one of

three models:

Laminar finite-rate model: The effects of turbulent fluctuations are ignored, and reaction

rates are determined by Arrhenius expressions.

Eddy-dissipation model: Reaction rates are assumed to be controlled by the turbulence,

so expensive Arrhenius chemical kinetic calculations can be avoided. The model is

computationally cheap, but, for realistic results, only one or two step heat-release

mechanisms should be used.


Eddy-dissipation-concept (EDC) model: EDC model is an extension of the Eddy-

dissipation model. Detailed Arrhenius chemical kinetics can be incorporated in turbulent

flames. However, typical reaction mechanisms are invariably stiff and their numerical

integration is computationally costly. Hence, the model should be used only when the

assumption of fast chemistry is invalid, such as modeling the slow CO burnout in rapidly

quenched flames, or the NO conversion in selective non-catalytic reduction (SNCR).

The generalized finite-rate formulation is suitable for a wide range of applications

including laminar or turbulent reaction systems, and combustion systems with premixed, non-

premixed, or partially-premixed flames.

2.2 Non-premixed combustion (PDF) model

Non-premixed modeling involves the solution of transport equations for one or two

conserved scalars (the mixture fractions). Equations for individual species are not solved.

Instead, species concentrations are derived from the predicted mixture fraction fields. The

thermo-chemistry calculations are preprocessed and then tabulated for look-up in FLUENT.

Interaction of turbulence and chemistry is accounted for with an assumed-shape Probability

Density Function (PDF).

The non-premixed modeling approach has been specifically developed for the simulation

of turbulent diffusion flames with fast chemistry. This approach is valid whenever non-

equilibrium effects such as extinction, reignition, lift-off and blow-out are not important, and it

greatly simplifies the chemistry modeling of any combustion system.

For such systems, the method offers benefits over the eddy-dissipation formulation. The

non-premixed model allows intermediate (radical) species prediction, dissociation effects, and

rigorous turbulence-chemistry coupling. The method is computationally efficient in that it does

not require the solution of a large number of species transport equations. This model is

implemented in Fluent such that chemistry calculations are also preprocessed and tabulated.

When the underlying assumptions are valid, the non-premixed approach is preferred over the

eddy-dissipation formulation.

In Non-premixed combustion model, the mixture fraction concept plays a vital role.

Considering certain assumptions, the instantaneous thermo-chemical state of the fluid is related

to a conserved scalar quantity known as mixture fraction f. First, the mass fraction of species can

be defined as

Consider a mixture of pure waste gas, so mass fraction of waste gas propylene C3H6 (w) = 1. The

mass fraction of carbon C (ZC) = 0.86, and the mass fraction of hydrogen H (ZH) = 0.14. The

elemental mass fractions remain constant throughout all the reactions. In non-premixed

combustion model, flame is considered as co-flow of fuel and oxidizer. In such mixture, Mixture

fraction f for element n at a specific point can be given as:


When two equations need to be solved in non-premixed combustion model: Mean mixture

fraction equation , and Mixture fraction variance equation . The conservation equation for

the mean mixture fraction is given below:

The conservation equation for the mixture fraction variance is given below:

where

- User defined source term

- Source term due solely to transfer of mass into the gas phase from reacting particles

The constants , , and are 0.85, 2.86, and 2.0, respectively

After that, the probability density function (PDF), written as can be considered as

the fraction of time that the fluid spends in the vicinity of the state f.

where is the time scale, and is the amount of time that f spends in the band. The shape

of the function depends on the nature of the turbulent fluctuations in f. In practice, is

unknown and is modeled as a mathematical function that approximates the actual PDF shapes

that have been observed experimentally.

Figure C.4: Graphical description of the probability density function,

Documents

Monthly Technical Report - aqrp.ceer.utexas.eduaqrp.ceer.utexas.edu/projectinfo/10-022/10-022 Tech Report Apr 201… · 4. Combustion Mechanism Validation (Task 4A) Details given