N EW D EVELOP MEN TS IN FLARIN G P R E S E N T E D B Y E AS T H - - PowerPoint PPT Presentation

N EW D EVELOP MEN TS IN FLARIN G

P R E S E N T E D B Y

E AS T H AR R I S COU N TY AI R P AR TN E R S

Flare Discussion

Types Regulation Operation TCEQ Flare Study Next Steps Anticipated Results

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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

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

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

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Flare Operation

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

• xygen, 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

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Flare Operation

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”

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”

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

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“Over-steamed” Flare

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

Video Source: TCEQ Houston Office

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“Over-steamed” Flare

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

Video Source: TCEQ Houston Office

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TCEQ R12 oversteam video.wmv

Background

16 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

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

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)

Some skepticism about flare DRE arose

TCEQ Flare Study

$2.2 million study conducted in Sept. 2010 Objective to measure DRE at very low turndown

Not emergency flare scenarios

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 Emissions sampler & remote sensing instruments

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Extractive Sampler Parts

Elev a tion Cha in Positioning Cha ins Extra ctiv e Sa m p le Inlet Pitot Flue Ga s Ed uctor GPS Sa m p le Lines

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

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Test Results at Incipient Smoke Point

Test Point A4.6

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

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Test Results with Transparent Flame

Test Point S3.1

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Test Results with Visible Flame

Test Point S3.6

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Effect of Small Increase in Steam

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 22

Why is High DRE Important?

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

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

Third photo has almost 100 times higher emissions compared to first photo 23

TCEQ Flare Test Results Summary

The flares tested were able to achieve greater than 99% DRE for

vent gas streams at low flow rates (high turndown) under certain conditions

For the conditions tested, the highest DRE was achieved at or near

the point when smoke first appeared (incipient smoke point)

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

emissions may or may not minimize emissions

Proper assist rates appear to be key to good DRE under high

turndown conditions

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Flares in your Area

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

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Flares in your Area

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

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Next Steps

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

performance

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

TCEQ is developing flare operator guidance EPA is developing new flare rules Flare vendors are reassessing their designs and operating

recommendations

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Over-Steamed?

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Too Little Assist? “Perfect” Assist?

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Proper Assist = High DRE

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Results

Changes to flare operations will potentially result in:

New visual landscape of small “candles” Likelihood of seeing some short-duration visible emissions

from flares

But also…

Reduced emissions ☺ Improved air quality ☺ Better public health ☺

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