Author: Donald Pretty, Project Manager,

Presenter: John Downs, Environmental Manager,

B&W PGG, KVB-Enertec Products

January 29, 2015

May 2007 – Rule was proposed as an amendment to the NSPS Subpart J Rule

December 2008 – Rule was finalized, however with an extension of the stay date

September 2012 – Final rule was promulgated in Federal Register

November 2012 – Effective date of final rule

November 2015 – Compliance date for NSPS Ja

Flare is now an affected facility, not a unit

Interconnected flare gas header system includes each individual flare serviced by the interconnected flare gas header system and the interconnected flare gas header system itself

New flare construction after June 24, 2008

Existing flare modification after June 24, 2008◦ New piping from refinery process unit

◦ Fuel gas system connection

◦ Alterations to increase flow capacity

Flare reconstruction after June 24, 2008

Total Reduced Sulfur (TRS) CEMS◦ Outfitted at flare header

◦ One required per header

◦ Must comply with 40CFR60, Appendix B, Performance Specification 5

Daily Calibrations

Cylinder Gas Audits

RATA

◦ 500lbs SO2 in any 24-hour period requires Root Cause Analysis & Corrective Action

Quality Assurance Requirements◦ Daily Validations

Depending on flare, could require % level H2S Standard for span analysis

Zero can be N2 depending on the CEMS type

◦ CGA

Both Low and Span Standards could require % level gas

◦ Different scenarios present where systems are calibrated locally or remotely through probe (state by state req.)

Quality Assurance Requirement (cont.)◦ Relative Accuracy Audit Tests (RATA)

Must collect samples of flare gas during normal operation

At same time, CEMS must be recording data

Samples are analyzed

Method 16 – directly by a gas chromatograph (GC) for 4 sulfur species (including H2S), consisting of TRS

Method 16A – by removing SO2 with a citrate buffer, then oxidizing leftover TRS compounds, and using Method 6 titration for analysis

Method 16B - by removing SO2 with a citrate buffer, then oxidizing leftover TRS compounds, and then measuring

with a GC

2 Types allowed

◦ Point CEMS

Sample gas is drawn from the flare pipe for external analysis

Ex-Situ direct extractive style

Oxidized sulfur analyzer (UV)

GC with columns for analysis (similar to style to one employed with Method 16

◦ Path CEMS

Sample is analyzed in-situ

TDL cross-stack CEMS

Employs a sample probe for extraction out of a flare line

Uses sample tubing (normally heat-traced) to deliver sample to an analyzer

Uses remote-mounted CEMS away from flare tip

Popular Technologies (GC)

ABB, Ametek, Emerson-Daniel, Siemens◦ Examples, there are other brands out there

◦ Fast-loop sampling systems

◦ Columns used for specific gas

analysis

Gas absorption on the column

(retention) and exit time (elution) of the column

are used for analysis

GC Operational Requirements◦ Utilities

Various Carrier Gas(es)

He, Ar, N2

Instrument Air

Purge air

120VAC

◦ Sample System

Must have pump to drive sample

Many vendors employ their own sample systems

Popular technologies (SO2 Oven):

Thermo Sola II◦ Pyrolyzer combusts

all sulfur species to

create SO2

◦ Pulsed Ultraviolet

Fluorescence (PUVF)

Technology for analysis

Thermo Sola II Operational Requirements◦ Utilities

N2 gas

Carrier gas

Purge gas

Instrument Air

Combustion air

Pneumatic valve actuation

120VAC

◦ Sample System

Must have pump to drive sample

Benefits◦ Remote monitoring away from flare pipe line

◦ Systems can be integrated in a shelter, protected from ambient conditions

◦ Easy data acquisition integration

◦ Reliable technology, analysis techniques have been present for years

Drawbacks◦ A lot of infrastructure (sample line, probe, sample

system)

Expensive

A lot of maintenance

Popular technologies (TDL):

Tunable Diode Laser◦ Laser absorption

spectroscopy

◦ Tuned to achieve best

measurement by

narrowing absorption

intensity for specified gas

TDL Operational Requirements◦ Utilities

Instrument Air

Lens purge air

Ports in the same plane 180deg apart

120VAC

◦ Sample System

No sample system required – direct measurement

Benefits◦ Little infrastructure

Ease of maintenance

Less costly than path CEMS

◦ Easy data acquisition integration

Drawbacks◦ Specialized installation, lined-up laser installation

◦ System serviced in ambient conditions

Potential human safety factor

Hydrogen Sulfide (H2S) CEMS◦ Outfitted at flare header

◦ One required per header

◦ Must comply with 40CFR60, Appendix B, Performance Specification 7

Daily Calibrations

Cylinder Gas Audits

RATA

◦ 162ppm H2S 3-hour rolling average limit (no long term H2S limit)

Gas chromatographs are the preferred method of H2S analysis◦ Because of Subpart J, many systems exist at

refineries already

◦ Many installations use the existing infrastructure to support TRS CEMS

May use the existing GC and upgrade it for TRS measurement

◦ Many of the same QA requirements

◦ Many GCs also provide a carbon-content/BTU measurement

Flare Flow Measurement◦ Outfitted on flare piping

◦ One required per flare entry line (or one at line exiting flare tip)

◦ No CEMS QA requirements

◦ Infrastructure and operation do not allow for a flow RATA

Flare flow normally very low (<1000 scf/day)

Flaring events are uncontrolled, potentially unsafe to have testers in place

◦ 500,000 scf/day above baseline flow requires Root Cause Analysis & Corrective Action

Popular technologies (Ultrasonic):

Ultrasonic wave attenuation◦ Doppler effect for flow

measurement

◦ Pressure and temperature

compensated flow

Other technologies:

Thermal Dispersion Model◦ Uses heat dissipation to determine

gas flow through flare

Optical Flow Measurement◦ Uses optical dispersion through

a laser to determine mass

flow

Flow Operational Requirements◦ Flare tap(s)

Must be in line for transducer pieces

Ports in the same plane (angle offset can vary)

Some vendors provide a prefabricated spool piece, supplied for insertion into the flare line

Taps should be in place for temperature and pressure sensors

Could reuse existing transmitters if already outfitted

120VAC

Housing for electronics

Only some models can sit outdoors

Equipment safety◦ Carbon-based gases have explosion potential

Normally classified as Class 2

Gas not present during normal conditions

◦ NFPA requirements dictate electrical classifications for Class 1, Div 2.

Various groups A-D (Acetylene; Hydrogen; Ethylene/CO; Propane/Methane/Acetone)

◦ Compliance

Special electrical equipment required (explosion-proof)

40CFR60, App B, PS-5, Section 5◦ This performance specification may involve hazardous materials,

operations, and equipment. This performance specification may not address all of the safety problems associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and determine the applicable regulatory limitations prior to performing this performance specification. The CEMS users manual should be consulted for specific precautions to be taken with regard to the analytical procedures.

In short – Safety is a Site-Specific Issue

Human safety concerns, not equipment safety

Flare Line Pressure◦ Based on relief valve pressure, could run 1 – 20 psi

Flare Line Temperatures◦ Temps could run 200 – 1000+ degF

Flare Line Velocities◦ Based on feeding process lines and size of flare tip,

velocities upwards of 50+ft/sec

Hazardous Gas

Flare gas by nature is high BTU content and potentially high sulfur◦ Carbon-rich gas

500 to 1500 btu/scf

C, C2,C3 and C4 chains (C5 potential)

◦ H2S

Concentrations upwards of 50%

Ways to mitigate risk

◦ Actively purging sample path CEMS

Use N2 gas for sample purging

Sample line, sample system, analyzer measuring bench

◦ Remote extraction points

For RATA testers when pulling samples

Pre-set taps with valves for safe extraction

◦ Training site personnel – knowledge is power

Regardless of technology, TRS CEMS must meet QA requirements◦ H2S measurement (potentially % level)

Flares have inherently dangerous potential◦ Temperature, pressure, flow, gas type

Explosion-proof atmosphere◦ Proper electrical equipment specifications