author: donald pretty, project manager, presenter: john ...€¦ · author: donald pretty, project...
TRANSCRIPT
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