demonstration of hydrogen air-assisted fla
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7/25/2019 Demonstration of Hydrogen Air-Assisted Fla
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Alexis McKittrick, Ph.D.Combustion R&DPraxair, Inc.
June 9, 2009
Demonstration ofHydrogen Use in Steam-and Air-Assisted Flares
www.praxair.com
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Hydrogen as a Fuel
for Flaring
• Current EPA flare complianceoptions
– Non-assisted Flares:
• 200 Btu/scf minimum OR
• 8 volume % hydrogen minimum
– Assisted flares
• 300 Btu/scf minimum
• Natural gas added to “sweeten”low-Btu streams and comply withregulations
• Much less hydrogen than naturalgas is needed to comply with EPArequirements for low-Btu flarestreams
2
• Praxair pursuing modification of 40CFR 60.18 and 40 CFR 63.11 toextend the current specification toinclude steam- and air-assisted flares
• Potential benefits:
– Lower operating cost - 50% to 70%
reduction
– Lower environmental emissions –
CO2, CO, NOx
– Lower net natural gas consumption
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Low-Btu Flaring for
Assisted Flares
WASTE30 Btu
(1000
NATURALGAS
(420 scf)
+
Currently, many flareoperators add natural gas to
the waste stream to complywith 300 Btu/scf regulation
3
GAS scf
cf)
HYDROGEN(130 scf)
+
Using Praxair’s proposedregulation, flare operators
could add Hydrogen to 11.5vol% to comply
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Benefits ExampleAssisted Flare – 100k scfh st
Fuel gas required for compliance (scfh)
Annual fuel costs (24/7 operation, 340 d/y) $4/MMBtu Natural Gas
NOx emissions (ton/yr)
CO emissions (ton/yr)
CO2 emissions (ton/yr)
~$1MM/year in pot4
eam @ 30 Btu/scf
Natural Gas
300 Btu/scf
Hydrogen
11.5 vol.%
Reduction
(%)
42,000 13,000 69
$1,400,000 $425,000 70
11.8 1.9 84
60.2 9.9 84
19,363 2,605 87
ntial annual savings
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Stream assumptions: waste gas volume = 100,000 scfh; waste gas heating
NOx & CO Calculations: Based on Standard Emissions Index from TCEQ’Flares and Vapor Oxidizers, October 2000, RG 109 (Draft) pg 18-19
Thermal NOX – 0.068 lb/MMBTU for steam assisted
CO - 0.3465 lb/MMBTU for steam assisted
CO2 Calculations: Based on 9.5lbs of CO2 for 1lb H2 produced from SMR; 11
Steam-Assisted Flare
Emissions Reduction
0
10
20
30
40
50
60
70
NOx CO
Emiss
ions(ton/ yr)
Natural gas fuel
Hydrogen fuel
5
alue = 30 BTU / scf; H2 volume % required = 11.5%
s Air Permit Technical Guidance for Chemical Sources:
3lbs CO2 for 1000scf of Natural Gas
–
ith Hydrogen
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
CO2
Natural gas fuel
Hydrogen fuel
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Testing Hydrogen A
to Assisted Flares
• Flare testing facility built in Tonawand
NY – 1H 2008 – Variety of fuels
– Assist / non-assist operation
• Goal: Add hydrogen compliance optio
for assisted flares to EPA regulations
• Critical parameters:
– >98% destruction efficiency of
hydrocarbons
– Flame stability
– No visible emissions / smoke
6
dition
,
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Assisted Flare Diagr
AirOutlet
SteamOutlet
Pilot GasInlet
SteamInlet
WasteGasInlet
AirInlet
Pi
Top View9
ms
ilot GasInlet Pilot
ConduitConnection
AirInlet
WasteGas
Inlet
SteamInlet
5’
Side View
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Additional Conside
• Mirrored previous flare studies where
– Flame Stability and Destruction Effici
– Flare diameter – 3 inches
– Ethylene used as surrogate HAP
– Use of emissions capture hood
– CO2 used as a tracer to determine a• Simplification of assist – test “worst c
– Steam assist is simple 5 nozzle ring d
– Air assist will not use advanced mixin
• Baseline measurements – Test 300 Btu/scf waste stream for ea
– Replicate non-assisted hydrogen-fuelequivalency of Praxair’s testing
10
rations
er possible
ncy tests
ount of captured flare emissions se scenario”
esign
aides
h assist setting (mimics current operation)
d flare flame stability tests to demonstrate
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Test Variables for
Assisted Flares
Variable
H2 volume %
Hydrocarbon heating value
Velocity
Steam Assist
Air Assist
11
Range / Value Tested
5 - 25%
30, 100, & 200 Btu/scf
20 - 150 ft/s
0.4 lb steam / lb ethylene
20% of stoichiometric airrequirement
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Flame Stability Imag
Flare Pipe
Pilot
FlareTip
(A)
Flare Pipe
Pilot
FlareTip
(A)
Not
Lifted
12
s
Flare Pipe
Pilot
FlareTip
NoFlame
(B)
Flare Pipe
Pilot
FlareTip
NoFlame
(B)
LiftedFlame
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Flame Stability Resu
Air-Assisted Flare
0%
2%
4%
6%
8%
10%
12%
14%
16%
18%
20%
0 50
Exit V
H y d
r o g e n V o l u m
e P e r c e n t ( %
)
13
ts –
100 150 200
locity (ft/s)
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Flame Stability Resu
Steam-Assisted Flar
0%
2%
4%
6%
8%
10%
12%
14%
16%
18%
20%
0 50
Exit V
H y d r o g e n V o l u m e P e r c e n t ( % )
14
ts –
100 150 200
locity (ft/s)
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Flame Stability Resu
• Fitting linear equations to t
results in the following:
• These equations can be usamount of hydrogen requirat a given exit velocity
Air-assisted flare: 04.0(%)2 = X H
Steam-assisted flare: 05.0(%)2 = X H
Where:
=(%)2 H X Hydrogen volume percent i
=) / ( s ft v Exit velocity of the flare (ex
15
ts
e flame stability data
ed to determine thed to ensure a stable flame
3.10) / (*9 +s ft v
83.9) / (*5 +s ft v
the waste gas exiting the flare
luding assist gas), not to exceed 150 ft/s
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Destruction Efficien
Results Using Hydro
eating Value Assist
of Waste Gas Used Runs
(Btu/scf) n Average
30 Steam 3 99.77
100 Steam 4 99.94
200 Steam 3 99.99
30 Air 4 99.26
100 Air 4 99.90
200 Air 3 99.92
Destruc
16
y
en
Exit Flame
Velocity Stability
95% Confidence (ft/s) Ratio
99.61 151 1.03
99.92 150 1.04
99.98 151 1.03
99.02 150 1.02
99.88 150 1.02
99.90 150 1.02
ion Efficiency
(%)
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Assisted Flare Testi
How Much Hydrogen
• Slightly morehydrogen requiredfor assisted flaresthan non-assisted
• These numbers
must be approvedby the EPA
• Assuming any newregulation will beequation-based(similar to currentcompliance options)
25
50
75
100
125
150
Exit Velocity
(ft/s)
17
g Results
?
No Assist Air-Assist Steam-Assist
8.0 11.5 11.3
10.2 12.7 12.7
12.4 14.0 14.1
14.5 15.2 15.6
- 16.4 17.0
- 17.6 18.5
Hydrogen Requirement (vol%)
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Praxair Study Conclu
• Hydrogen use in assisted fl
flare testing as closely as p
• Results established a flameassisted flares over a range
• Destruction efficiencies aboall hydrogen-fueled conditio
• Requesting that 40CFR 60.include hydrogen as a comair-assisted flares based on
18
sions
res study mirrored previous
ssible
stability envelope forof velocities
e 99% were observed fors tested
8 & 63.11 be amended toliance option for steam- andthese findings