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Designing low NOx combustion systems for end port glass melting furnaces using an integrated CFD based approach
Author(s)
Affiliation
1
Primary techniques for NOx containment in a sustainable glass industry The achievements of the Prime Glass Project
Sauro Pasini, Sandro Merlini, Lucia Giovannini – rjc soft
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
Outline
• NOx formation/destruction chemistry
• Modelling approach and calibration
• Case studies
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Time
Temperature Turbulence
The fire triangle The phenomena involved
High temperature furnaces: a complex environment rjc soft®
Large boilers & glass furnaces have similar environments
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
The pollutants of interest
N2 NOx
NITROGEN OXIDES
CO
CARBON OXIDE
NOx formation/destruction mechanismsNOx formation mechanisms for CH4 combustion
REDUCING ATMOSPHERE
OXYCYANOGEN(OCN,HNCO)
NOX
N2
FRAGMENTSHYDROCARBON
CH, CH2
NITRICCOMPOUNDS
SPECIE AMMONIACALI
(NH3, NH2, NH, N)
CYANOGEN(HCN, CN)
HYDROCARBONFRAGMENTS
CH, CH2
NOX
N2
N2O
H
AIR FUEL
A
B
F
F
E
B
D
B D
G
G B
B
BC
B
B
AMMONIACAL SPECIES
(NH3, NH2, NH, N)
THERMALNOX
PROMPTNOX
FUELNOX
OXIDISING ATMOSPHERE
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
NOx reduction options
Reduce the temperature
“Oxidise without oxidising”
Flue gas recirculation
Staging, OFA, Burner Out Of Service, …
Reburning
Lean Reburning
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjc soft®
Low NOx Burners
Outline
• NOx formation/destruction chemistry
• Modelling approach and calibration
• Case studies
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Under contract from Enel, RJC has completed the development of a code capable of managing any typical configuration of boilers and furnaces (opposite wall fired or tangentially fired boilers, glass furnaces, …), any fuel or combustion environment (gas, oil, coal, biomass, reducing environment, oxy-firing, gasification), providing detailed information on fluid flow, heat transfer, combustion efficiency, pollutant emissions, …
An integrated CFD based approach: the IPSE Code
The prediction of NOx emissions under reducing conditions requires the capability of using a complex chemistry: hundreds of radical species and thousands of reactions.
Being the option to incorporate detailed reaction kinetics directly in a 3D CFD code unfeasible, in 2000, together with University of Pisa, the Reactor Network Model was developed, based on the rezoning of the computational volume in a series of simple chemical reactors.
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
The CFD + RNA Modeling Methodology
Reactor Network Analysis (RNA), is a post-processing tools to estimate combustion emissions.
RNA generates an equivalent network of reactor elements extracted from the results of CFD simulations by an automatic zoning algorithm.
Detailed reaction mechanisms are applied over the reactor network and a more accurate calculation of the combustion yields is performed.
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
R1302
R4909
R32900R123524
R2218
R91143
R6951
R8927
R5264
R10344
R7774
R11752
Reaction progress is calculated with DSMOKE, a CHEMKIN like software
Detailed kinetic mechanism by Milan Polytechnic researchers:
A series of hierarchical reaction blocks are disposed, starting from the basic CO/H2 oxidation mechanisms.
Hydrocarbon Combustion Mechanism involves about 200 species and more then 3000 reactions.
Nitrogen sub-mechanism involves about 200 reactions and 40 species.
Detailed Reaction Chemistry Computation
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Inlet Air
Burners
Outlet GlassMeltedLoadDog-House
INLET/OUTLET DUCTS
VAULT
GAS/GUN - BURNERS
GLASS MELTED LOAD“DOG HOUSE”
Calibration: “End-Port” Glass Melting Furnace (2001)The first calibration of the model for glass furnaces was performed by Enel in 2001, together with Stara Glass. In those test campaigns Enel verified the capabilities of the software methodology in this new environment.
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
0 5 10 15 20 25 30 351500155016001650170017501800185019001950200020502100
10 MW furnace
measurements CFD simulation
Tem
pera
ture
(°C
)
measurement positions
CFD simulation against “in flame” measurements
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
1,0 1,2 1,4 1,6 1,8 2,0800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
measured values predicted by RNA (CFD with kinetics)
NO
2 [ m
g/N
m3 @
8%
O2 ]
O2 in exhaust (% dry vol.)
NOx predicted from Reactor Network Model
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
This integrated methodology well performed for glass melting furnaces, resulting in a good agreement between measured and calculated values of temperature and chemical species.
This concept is not restricted to the NOx calculation, it can be used also for any other species for which a detailed reaction scheme is available.
This approach is also a reasonable trade-off between the complexities of the phenomena occurring in reactive flow fields and the engineering demands for addressing the design of practical combustion systems.
Some considerations for glass furnaces
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Outline
• NOx formation/destruction chemistry
• Modelling approach and calibration
• Case studies
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Some low-NOx technologies for EP glass furnaces
In the following a preliminary evaluation of the possible efficiencies of typical low NOxconfigurations applied to glass furnaces has been performed
1 – Baseline (& low NOx burner) 2 - Flue Gas Recirculation
Flue Gas
4 – Over Fire Air
Air
5 – Lean Reburning Gas
3 – Burner Out Of Service
x
x
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Base case: temperature and chemical speciesHorizontal section 18 cm above burners
Mean O2 at exit ~ 2% Mean NOx at exit ~ 850 mg/Nm3
Temperature 800-2000 °C
Oxygen0-12%
NOx0-0.6% w/w
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Base case: temperature and chemical speciesVertical section 60 cm from entrance
Temperature 800-2000 °C
Oxygen0-12%
NOx0-0.6% w/w
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Base case: temperature and chemical species
Temperature 800-2000 °C
Oxygen0-12%
NOx0-0.6% w/w
Vertical section in the middle of the entrance
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
Burner modification: ongoing activity (IFRF data)
Fuel input: 0.5 MW
Combustion Air
o Temperature: 1100° C
o Angle: 20°
o Velocity: 10 m/s
Gas firing modes: Underport, Overport, Sideport, Parallel sideport.
Fuel injection modes: Normal, Annular, Swirled.
rjcsoft®
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
UP 16° 125 m/s
OP 20° 125 m/s
NOx reduction efficienciesBurner modification: IFRF experimental data rjc
soft®
NOx
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
UP 16° 125 m/s OP 20° 125 m/s
Burner modification: IFRF experimental data
Burner geometry and operative conditions are important parameters to be analyzed.Modelling activity ongoing together with prof. Pourkashanian at Sheffield University
rjcsoft®
Flue Gas Recirculation: fundamental concepts
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
External FGR has already shown its potential in many high temperature process applications. Diluted combustion has both a thermal effect, dampening temperature peaks, and a chemical one, reducing flame burning velocity (no effect on CO emissions), with a more pronounced effect for intense flames.
Soft flame Tight flame
CO Iso-surfaces Tight flame
Gas- und Warme-Institute FGR testing results in a semi-industrial test rig.
rjcsoft®
FGR: O2 concentration at the inlet
Base Case, No FGR Base Case, low FGRBase Case, uniform FGR
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
NOx 0-06% w/w
∆NOx = -19 %∆NOx = -14 %
FGR: NOx concentration
Base Case, No FGR Base Case, low FGRBase Case, uniform FGR
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
50,00%
55,00%
60,00%
65,00%
70,00%
75,00%
80,00%
85,00%
90,00%
95,00%
100,00%
Base 21% uniform 21% low
NOx Emissions, %
FGR: reduction efficiency
∆NOx = -14 %∆NOx = -19 %
Flue gas recirculation can reduce NOx linearly, of the same entity of FGR fraction for the “low” configuration
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Burner out of service: comparison with base caseTemperature 800-2000 °C NOx 0-06% w/w
Base Case Burner out of service Base Case Burner out of service
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
NOx 0-0.6% w/w Base Case
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
Burner out of service
rjcsoft®
Burner out of service: comparison with base case
Burner out of service: reduction efficiency
50,00%
55,00%
60,00%
65,00%
70,00%
75,00%
80,00%
85,00%
90,00%
95,00%
100,00%
Base BOOS
NOx Emissions, %
∆NOx = -12 %
Burner Out Of Service can reduce NOx due to the staging of the fuel achieved in the main burner zone
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Fuel staging: comparison with base caseTemperature 800-2000 °C NOx 0-0.6% w/w
Base Case Staging Base Case Staging
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Fuel staging: comparison with base caseNOx 0-0.6% w/w Base Case
Fuel Staging
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
50%
55%
60%
65%
70%
75%
80%
85%
90%
95%
100%
Base Br. 3 Br. 2 Br.1
NOx Emissions, %Fuel staging: NOx reduction efficiencies
∆NOx
-17 %
-25 % -25 %
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
The integrated methodology developed can be efficiently used to calculate NOx reduction efficiencies corresponding to different configurations of the combustion system
Comparison with experimental data has shown good correspondence, on average, between reductions predicted and measured, even if these preliminary calculations have been performed with a not well detailed grid.
Combustion modification is an interesting option to adopt in glass furnaces to reduce NOx, before seeking for expensive flue gas cleaning technologies. The preliminary results obtained confirm the validity of the extensive know-how already developed for p.p. boilers:
Flue gas recirculation can reduce NOx linearly, of the same entity of FGR fraction
Burner Out Of Service has shown a 10 to 15% reduction due to fuel/air staging
Lean reburning realized moving one of the three gas burners to the side wall, has shown a NOx reduction efficiency of about 25%
Some final considerations for glass furnaces
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®
Primary combustion modifications offer a lot of different options, as function of furnace characteristics, baseline NOx emissions, expected reduction efficiencies, investment costs, …. , and glass furnaces are favored over power station boilers, due to the much larger residence times
Designing combustion modifications is the same as sewing a tailor’s dress.
The methodology developed can easily allow any combination of the above mentioned technologies, proving very effective in supporting the definition of the optimal strategy to be adopted as function of the specific case.
Some final considerations for glass furnaces
LIFE12 ENV/IT/001020 - PRIME GLASS Prime Glass Conference
Rapallo (Genova – Italy) – March 30th 2017
rjcsoft®