New - 4_Flares Final

Flare Systems

Typical Relief System Vent Header

R.V.

RE/U&O Flares-2

Purpose of Flare „

Define Loadings to be Handled –

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Calculate loadings for all contingencies Geographic location of each source Calculate maximum load (power failure,fire case) • Fire case limited to a ground area of 230 - 460 square meters • Calculate maximum back pressure

Major Factors Influencing Flare Design „ „ „ „ „ „ „ „ „ „

Gas Composition Flow Rate Gas Pressure Available Initial Investment Operating Costs Gas Temperature Energy Availability Environmental Requirements Safety Requirements Social Requirements

Main Flare Standards and Recommended Practices „

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API RP 520: Part I – Sizing Selection and Installation of Pressure-Relieving Devices in Refineries – Part I – Sizing and Selection API RP 520: Part II – Sizing Selection and Installation of Pressure-Relieving Devices in Refineries – Part II – API RP 521: Guide for Pressure-Relieving and Depressurizing Systems API Standard 537: First Edition September 2003: Flare Details for General Refinery and Petrochemical Services RE/U&O Flares-5

US EPA Requirements – 40CFR60.18 „

Sizing must also comply with Federal Register (40 CFR 60.18) for maximum velocity of steam-assisted, elevated flares: Net Heating Value of Vent Stream Bv (Btu/scf) 300 300-1000 > 1000

Maximum Velocity Vmax (ft/sec) 60 log10(Vmax) = (Bv + 1214)852 400

It is standard practice to size the flare so that the design velocity of flow rate Qtot, is 80 percent of Vmax: Dmin (in) = 12*[((4/PI)(Qtot/60sec/min))/(0.8*Vmax)]^0.5 Dmin (in) = 1.95 * (Qtot/Vmax)^0.5 „ Where: Qtot = Q + F (measured at stream temperature and pressure) „ Dmin should be rounded up to the next largest available commercial size „ Btu/scf * 0.0373 = MJ/scm and ft/sec * 0.305 = m/s „

Auxiliary Fuel Requirement „

Amount of fuel required (F) is calculated based on maintaining the vent gas stream net heating value at the minimum of 300 Btu/scf (11.2 MJ/SCF) required as described in the United States Federal Register: (Q * Bv) + (F * Bf) = (Q + F)* (300 Btu/scf) Where: — Q = vent stream flow rate, scfm — Bv = Btu/scf of the vent stream — Bf = Btu/scf of the fuel stream Therefore, F (scfm) = Q * (300-Bv)/(Bf-300) The annual auxiliary fuel requirement (Fa) is: Fa (Msfm/yr) = (F scfm) * (60 min/hr) * (8760 hr/yr) Fa (Mscfm/yr) = 526 * F

Elevated Flare System Flare Tip Steam Ring Dry Seal Knockout Drum Pumpout Pump

Flare Knockout Drum

Flare Stack

PI TI Instrument Air Vent Emergency Gas Purge

Switch

LIAH

LGR

Solenoid Valve (With Manual Reset)

RO RO

Purge Gas

Gas To Pilot

PI

TAH

Grade

M

Pilot Ignition Systems Locate At Flare Knockout Drum

Normal Gas Purge Steam

Pressure Relief From Process Units

Slop To Slop Tank

PI

PC

Fuel Gas

Plant Air

Ground Flare System

Flare Knockout Drum

Knockout Drum Pumpout Pump

PI TI

LGR

LIAH

Switch

PI

Instrument Air Vent

Emergency Gas Purge

Solenoid Valve (With Manual Reset)

Ground Flare Retention Dike Burners Grade

M

Stage Header

PO PO Normal Gas Purge

Purge Gas

Main Header PC

Pressure Relief From Process Units

Slop To Slop Tank

Gas To Pilot

PI

Pilot Ignition Systems Locate At Flare Knockout Drum PC

Fuel Gas

Plant Air

Two Stage Flare System (Elevated/Ground) Flare Tip

Seal Flare Stack Flare Knockout Drum

Knockout Drum Pumpout Pump

PI TI

LGR

LIAH

Switch

PI

Instrument Air Vent

Water Seal

Solenoid Valve (With Manual Reset)

Enclosed Ground Plane

Gas To Pilot

M

Pilot Ignition Systems Locate At Flare Knockout Drum

Emergency Gas Purge RO RO

PI Normal Gas Purge

Purge Gas

Pressure Relief From Process Units

PC

Slop To Slop Tank

Water

Fuel Gas

Plant Air

Grade

Flare Stack

Structure „ Self Supporting „ Guy Supported „ Derrick Type

Demountable Derrick Single-Section Riser

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Normal Position is “A” then can be lowered for work on the tip to position “C” Allows for easy replacement of tip

RE/U&O Flares-12

Demountable Derrick-Multiple Section Riser

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Riser assembled in sections Designed to accommodate multiple risers Designed so that one flare can be taken out of service while others are still in operation

RE/U&O Flares-13

Conventional Pressure Relief Valve

RE/U&O Flares-14

Balanced-Bellows Pressure Relief Valve

RE/U&O Flares-15

Pop-Action Pilot-Operated Valve (Flowing Type)

RE/U&O Flares-16

7

Radiation Theory

6 5

Exposure Times Necessary to Reach the Pain Threshold

4 Threshold of Pain

3 2

Safe Limit

440 Btu/(hr) (ft)2

1 0

10

550 740 920 1500 2200 3000 3700 6300

30

40

Exposure Time, Sec.

Radiation Intensity Btu/hr-ft2

20

Kilowatts per M2

Times to Pain Threshold (Seconds)

1.74 2.33 2.90 4.73 6.94 9.46 11.67 19.87

60 40 30 16 9 6 4 2

50

60

Contours of Radiant Heat Intensity Safe Boundary (440 Btu/Hr/Sq.Ft.) Boundary for Radiant Heat Intensity (1500 Btu/Hr/Sq.Ft.) - Normally Fenced in with Warning Signal Protection Required for Equipment

Protection Required for Personnel Boundary for Radiant Heat Intensity (3000 Btu Hr/Sq.Ft.)

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Environmentally acceptable combustion Tips normally proprietary in design Flame stability Ignition reliability Exit velocity 1 to 600 ft/s (.3 to 183 m/s) Exit velocity at 50% of sonic velocity Multiple pilot burners Surrounding windshield

Flare Tip

Flare Tip Design

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Flare Tip Design Considerations Design for maximum flow rates – Design for maximum temperatures – Design for wind conditions – Design for minimum flow rates –

Pilot and Ignition Systems

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Continuously burning pilots Flame front generator –

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Fuel gas and air admitted to the ignition pipe in a combustible ratio Gas is ignited by an electric spark Flame travels through the pipe

Flame Front Generator Ignition System

F

Air

B

D

A To Pilot #1

H J Gas

To Pilot #2 To Pilot #3

E C

Gas To Pilots

Pilot Burners

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Automatic systems may be activated by: Thermocouples – Infrared Sensor – Ultraviolet Sensor (ground flare application) –

Installation of Thermocouples Correct Installation

Incorrect Installation

Pilot Windshield

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Allows pilot to operate at wind speeds greater than 100 mph Should always be specified Prevents misreading of the thermocouples

Pilot Gas Requirement „

The average pilot gas consumption based on an energy-efficient model is 70 scf/hr. The annual pilot gas consumption (Fp) is calculated by: • •

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Fp (Mscf/yr) = (70 scf/hr)*(N)*(8,760 hr/yr) Fp (Mscf/yr) = 613*N

N can be calculated from the following table:

Flare Tip Diameter (IN) 1-10 12-24 30-60 >60

Number of Pilot Burners (N) 1 2 3 4

Multiple Pilots „

Multiple pilots allow one pilot to fail

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Most flares have two to four pilots

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Equally spaced around the flare

Troubleshooting Pilots Problem Possible Cause

Corrective Action

Plugged Pilot Tip

Start-up debris left in system

Remove debris manually or by high pressure blowing

Plugged Pilot Tip

Unsaturated Fuel Hydrocarbons

Remove manually or by high pressure blowing then return to fuel gas

Damage Pilot Tip

Pilot tip has increased in size; Pressure drop in pilot decreased; Fuel/Air mixture more lean

Replace pilot tip

Incorrect Fuel

This can be determined by fuel sample; if hydrogen concentration has increased significantly then flashbacks may be audible and visible

Return to design fuel gas; Pilot modifications may include: replace pilot orifice; adjust air door; replace pilot entirely RE/U&O Flares-28

Purging „

Flare purge gas –

Any gas which cannot go to dew point under any condition of operation • • •

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Fuel Gas Inert Gas Nitrogen

Purge Rate •

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Flare Stack — Linear velocity 1FPS to 5FPS (.3 to 1.5 m/s) Flare stack with molecular seal — 0.10 FPS to 0.20 FPS (.03 to 0.06 m/s)

Purge Gas Requirements

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Prevents flashback problems Flare operates at positive pressure Purge all subheaders (upstream) .04 feet per second to 1 feet per second (.01 meters per second to 0.33 meters per second)

F (Mscf/yr) = (0.04 ft/sec)*((PI*D^2/4)/144 ft2))*(3600 sec/hr)*(8,760 hr/yr) F (Mscf/yr) = 6.88*D^2

Dry Seals

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Molecular Seals

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Double Seals

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Fluidic Seals

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Airrestors

Molecular Seal

Flare Assembly

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Molecular Seal Liquid Drain

Prevents explosions Prevents entry of air Reduces purge gas Performs silently with small pressure drop

Smokeless Flare Operation Smokeless Operation

Smoking

US EPA allows smoking for Only 5 minutes per hour

Steam Requirements and Smoke Suppression Methods „

In general, the following equation can be used: Wsteam (lb/hr) = Whc (lb/hr) * [0.68-(10.8/MW)]

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Smoke Suppression Methods – – – –

Steam injection High pressure gas injection Low pressure air Internal energized flare

Automatic Steam Control Field Of View Steam Nozzles

Steam Control Valve

Monitor Flux Density Signal Controller Control Scheme

Automatic Steam Control „

Minimizes steam consumption

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Controlled by the flame appearance

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Calibrated to a particular frequency in the infrared spectrum

Knockout Drums „

Principle Features –

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Complete removal of either slugs or mists of liquid (300 microns to 600 microns) Recovers valuable condensed hydrocarbons Ends maintenance difficulty caused by “Wet” gases Used as the base for the flare riser Ends “Wet Gas” control problems

The allowable vertical velocity in the drum may be based on the necessity to separate droplets from 300-600 microns in diameter.

Truck Loading Vapor Control Flare „

Achieve high destruction efficiencies through the loading cycle

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Systems range in size from 100 BPH to 25,000 BPH

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Enclosed burners can be easily tested for emissions

Troubleshooting Enclosed Flares Problem

Cause

Action

High Frequency Noise

Most likely associated with steam injection

Check steam quality and properties

Combustion Roar (low frequency)

Intense combustion

Check flare gas pressure and steam quality

Visible flame

Excess flow

Check diverting water seal or valve

Smoke

Air starvation

Check wind fence for blockage or is wind condition unusual

Smoke

Low gas pressure

Check bypass relief devices and staging valves

Smoke

Steam/support air shortages

Check steam supply or blowers RE/U&O Flares-39

Coupled Effects of Temperature and Time on Rate of Pollutant Oxidation Pollutant Destruction, %

100 80 60 40

1 sec 1.0 sec 0.01 sec

0.001 sec

Increasing Residence Time

20 0 600

800

1000 1200 1400 1600 1800 2000 Increasing Temperature, °F

Residence time of gases in combustion chamber calculated from: t = V/Q t = Residence Time (s) v = Chamber Volume (ft3) Q = Gas volumetric flow rate at combustion conditions (ft3/s)

Schematic of a Thermal Incinerator Fume

Fuel

Exhaust

Combustion Air (Fume)

Typical Marine Vessel Loading System Product Loading Arm Product from Storage Tanks Vapor Arm

Natural Gas/ Inerting Gas Enriching Gas Detonation Analyzer Arrestor

Vapor Mover

Hydrocarbon Vapor to Control Device

Knockout Drum(s) Discharged Vapors Sump Pump

Ship or Barge Dock Facilities

Condensate to Tanks

Shoreside Facilities

Flare Gas Recovery Compressor

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Flare gas recovery compressor designed to capture flare gases and compress to fuel gas pressure Reduce natural gas purchases RE/U&O Flares-43

Flare Gas Recovery Compressor „ „ „ „

Difficult service for a compressor Wide range in Volumetric flow and MW Dirty Service - water, rust, H2S, CO2 and HCl Corrosion and Fouling

RE/U&O Flares-44

Liquid Ring Compressor Type Operates on the rotary liquid piston principle „ The shaft and the impellers being the only moving parts „ Shaft and impeller assembly is mounted eccentrically relative to the pump casing „ As the impeller rotates the water (which is continually supplied to the pump), is forced outwards by centrifugal force to form a liquid ring revolving concentric to the pump casing „

RE/U&O Flares-45

Source Reduction Program „ „

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Locate relief valve leaks Carryout repairs to reduce amount of gas going to flare Check each relief valve every 3 to 6 months Leakage could occur through normal wear and tear on the valve Leakage could occur due to incomplete closure RE/U&O Flares-46

Source Reduction Program

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Potential Saving of $1,000,000 per year have been recorded Relates acoustic signal level to gas losses for various valve types of different valve sizes and working pressure range

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Device extremely portable

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Can approximate flowrates and associated dollar values

RE/U&O Flares-47

Flare Flow Meters: Ultrasonic “Time of Flight” Technology „ „

Panametrics of Waltham Massachusetts Proprietary algorithm to determine instantaneously the molecular weight and mass flow rate of the flare gas

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Meter is used to conserve energy and reduce product loss by identifying sources of leaks into the flare systems

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Reduces energy usage by accurately controlling the amount of steam fed to the flare tip RE/U&O Flares-48

The End „ „

Next: Good buy! Questions ?

RE/U&O Flares-49