NEW DEVELOPMENTS IN FLARING - deerparkcac

NEW DEVELOPMENTS
IN

FLARING

PRESENTED BY

EAST HARRIS COUNTY AIR PARTNERS

Flare Discussion

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y Types
y Regulation
y Operation
y TCEQ Flare Study
y Next Steps
y Anticipated Results

What do you know about flares?

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?

Types of Flares

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Staged Flare Single Point Flare

Types of Flares

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Air-assisted Flares

Types of Flares

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Multi-point Ground Flare

Types of Flares

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Enclosed Ground Flare and Tips

Types of Flares

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Enclosed Ground Flare and Flare Tips (from inside)

Types of Flares

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Steam-assisted Flares

Types of Flares

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Elevated Flare Ground Flares

Flare Operation

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y Primary function is as a safety device

Protect equipment from catastrophic failure (pressure relief)
Protect employees/community from exposure to pollutants
Designed with safety in mind: big enough to handle the largest
release

y Over the years, flare operations have evolved

Initially designed only for emergencies (safety devices)
Then became “dump” for waste gases, off-spec materials, etc.
Later used as alternative to venting directly to atmosphere
Today used as emissions control devices for most process vents

Flare Operation

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y In addition to process gases, purge gas and assist gas
are often routed to flares

Purge gas (usually natural gas) sweeps the flare header of
oxygen, corrosives, reactives, and inerts

Assist gases (usually steam or air) improve mixing for better
combustion, help protect the flare tip from heat damage, and
help minimize visible emissions

Flare Operation

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y Flare operators have been trained to add sufficient steam
(or air) to prevent visible emissions

Over the years this has translated into “more is better”

y Many facilities have reduced continuous flaring, resulting
in flares that operate well below their design capacities

Operating at <1% of design capacity is known as “high turndown”

y Some recent study data indicate that this combination of
high flare turndown + increased assist rate may be
contributing to lower flare destruction efficiency (DRE)

DRE = how well a flare destroys the materials being burned

“Over-steamed” Flare

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Good looking flare? Here’s what’s really going on!!

Video Source: TCEQ Houston Office

“Over-steamed” Flare

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TCEQ R12 oversteam video.wmv

Qualitative Test with IR Camera Shows Significant Flare Hydrocarbon Emissions
In the Presence of Visible Steam

Video Source: TCEQ Houston Office

Background

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y EPA regulates flares through a rule called “60.18”

Visible emissions limited to 5 minutes in 2 hours
Flame must be present at all times
Limits on minimum net heating value and maximum gas exit velocity
Monitor to ensure the above conditions are met

y Flares meeting all 60.18 requirements assumed to have a 98% destruction
and removal efficiency (DRE)

For every 100 pounds VOCs fed to the flare, 98 pounds will be destroyed and only 2 pounds
will be emitted

y Air quality studies raised questions about differences in measured air
quality vs. estimated emissions

Texas 2000 Air Quality Field Study
2006 Texas Air Quality Study (TexAQSII)
Numerous Houston-area flyovers
2009 Study of Houston Atmospheric Radical Precursors (SHARP)

y Some skepticism about flare DRE arose

TCEQ Flare Study

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y $2.2 million study conducted in Sept. 2010

y Objective to measure DRE at very low turndown

Not emergency flare scenarios

y Limited test conditions

Vent gas was simple mixture of propylene, natural gas,
and nitrogen
Test conditions met 60.18 requirements
Assist gas rates varied from zero to point of snuffing out
flare flame

y Emissions sampler & remote sensing instruments

Extractive Sampler Parts

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Flue Gas
Eductor

Pitot GPS

Extractive
Sample
Inlet

Positioning Sample
Chains Lines

Elevation
Chain

Forced Air Device Positioned with Crane while Extracting Samples of Flare Emissions

Test Results at Incipient Smoke Point

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Vent Gas Btu/scf DRE (%)
937 lb/hr 350 Btu 99.4

Test Point A4.6

Test Results with Transparent Flame

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Test Point S3.1

Test Results with Visible Flame

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Test Point S3.6

Effect of Small Increase in Steam

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Test Point S4.2 Test Point S4.7 Test Point S4.3

Visible Flare and Invisible Steam Result in >99% DRE
Visible Steam Results in Rapidly Falling DRE

Why is High DRE Important?

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Test Point S4.2 Test Point S4.7 Test Point S4.3

At 99.2% DRE, At 90.6% DRE, At 27.3% DRE,
20,000 pounds of flare gas 20,000 pounds of flare gas 20,000 pounds of flare gas
results in (0.008 x 20000) = results in (0.094 x 20000) = results in (0.727 x 20000) =
160 pounds of unburned flare gas 1880 pounds of unburned flare gas 14,540 pounds of unburned flare gas

Third photo has almost 100 times higher emissions compared to first photo

TCEQ Flare Test Results Summary

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y The flares tested were able to achieve greater than 99% DRE for
vent gas streams at low flow rates (high turndown) under certain
conditions

y For the conditions tested, the highest DRE was achieved at or near
the point when smoke first appeared (incipient smoke point)

y Low DRE occurred with invisible flames
y Operating the flare within legal requirements of 60.18 and no visible

emissions may or may not minimize emissions
y Proper assist rates appear to be key to good DRE under high

turndown conditions

Flares in your Area

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y Plant Managers have provided a brief summary of
the number & types of flares they have

Emergency-only flares
Process-only flares
Combination emergency & process flares

Flares in your Area

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y Summary of DPCAC Flare Survey

7 of 14 DPCAC plants have flares
50 flares among the 7 plants
3 of the 50 flares are emergency only flares
24 of the 50 flares are process only flares, with continuous flow
10 of the 50 flares are process only flares, with intermittent flow
13 of the 50 flares are combination flares
13 of the 50 flares are steam-assisted
5 of the 50 flares are air-assisted
12 of the 50 flares have no assist
1 plant of 7 (Shell) has flare gas recovery

Next Steps

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y TCEQ, EPA, and Industry are working to better understand flare
performance

y Industry is examining its current flare operating practices to find
improvements

Looking at manual assist rates
Exploring better controls, monitoring equipment, and alternative emissions
control technology that might be implemented in some cases

y TCEQ is developing flare operator guidance

y EPA is developing new flare rules

y Flare vendors are reassessing their designs and operating
recommendations

Over-Steamed?

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Too Little Assist? “Perfect” Assist?

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