bruce c. davis pe, qep consultant - air quality technology...

Review of Comments submitted to EPA

on the Refinery Flare Rules

Bruce C. Davis PE, QEP

Consultant - Air Quality Technology

DuPont Engineering Research & Technology

Houston, TX 77090



Summary of Comments Submitted to EPA on the Flare Provisions of the Refinery Sector Rule Proposal

Purpose

Process

Product

Summarize issues highlighted in the comments to comply

with the proposed flare rules for industry.

Summarize the implications if the EPA uses the same

regulatory approach for the chemical industry as is

proposed for the refining industry.

Summarize the issues raised by commenters on the

Refinery Sector Risk and Technology Review and New

Source Performance Standard Proposed Rule related to

flare provisions.

Review the flare comments submitted by the American

Chemistry Council, the American Petroleum Institute and

selected industry commenters.

The main focus of this presentation is on the ACC

comments since DuPont is not a member of API.



The rule was proposed on June 30, 2014.

The comment period on the rule closed on October 28, 2014.

The rule is subject to a settlement agreement which requires the

rule to be signed by the administrator by June 16, 2015.

The rule, when finalized, will be applicable to refinery flares BUT

Regulatory Schedule



The rule will be the basis for future regulation of flares for other

industry sectors as the MACT and NSPS rules are reviewed and

possibly changed for other industry sectors.

The first set of rules for the chemical industry, where new flare

provisions are expected, is for the ethylene industry.

Regulatory Schedule



The operational requirements for flares are set forth in the

General Provisions at 40 CFR 63.11(b) & 60.18.

• These General Provisions requirements specify that flares shall be:

• Steam assisted, air-assisted, or non-assisted;

• Operated at all times when emissions may be vented to them;

• Designed for and operated with no visible emissions (except for periods

not to exceed a total of 5 minutes during any 2 consecutive hours); and

• Operated with the presence of a pilot flame at all times.

The Current Rules



The General Provisions also specify requirements for both the

minimum heat content of gas combusted in the flare and

maximum exit velocity at the flare tip.

• There are a separate set of provisions for hydrogen rich gases

that require operation > 8 vol % hydrogen and provide maximum

exit velocity limits..

The General Provisions only specify monitoring requirements for

the presence of the pilot flame and the operation of a flare with

no visible emissions.

The current rules exempt periods of start-up, shutdown and

malfunction (SSM) from visible emissions and exit velocity

requirements

The Current Rules



For all other operating limits, Refinery MACT 1 and 2 require an

initial performance evaluation to demonstrate compliance but

there are no specific monitoring requirements to ensure

continuous compliance.

Flare performance tests conducted over the past few years

suggest that the current regulatory requirements are insufficient

to ensure that refinery flares are operating consistently with the

98-percent HAP destruction efficiencies that EPA has

determined to be the MACT floor.

The Current Rules & Reasons for Change



The EPA is doing away with the SSM exemption and is

proposing that the visible emission and exit velocity rules apply

at all times.

• This will require hundreds of new flares and is impractical to say

the least

• The API is working with EPA to establish alternative work

practices that would apply during emergency flaring events.

The Current Rules & Reasons for Change



The proposed refinery performance parameters are one size fits

all (large, medium and small flare systems) and only two flare

category types.

The regulatory parameters will change:

• Current: Spot measurement or calorimeter for BTU/scf and

velocity in flared gas.

What is changing?



Proposed: Continuous monitoring/measurement of BTU/scf, or %

LEL, or % combustible in combustion zone.

• Continuous compliance – startup, shutdown and normal

operations

• Combustion zone parameters mean accounting for steam or air

assist and mean measuring both flared gas flow and steam or air

assist flow. In addition, different measurements (composition

and/or BTU/scf) will be needed to estimate each of the

performance parameters.

Averaging time for the new parameters.

• The EPA is proposing an averaging time of a 15 minute block

average for compliance parameters AND EXIT VELOCITY.

What is Changing



The current steam assisted regulation is to operate > 300

BTU/scf in the flared gas.

The current unassisted flare regulation is operate > 200 BTU/scf

in the flared gas.

The new regulation is either

• >= 270 BTU/scf or

• <= LFLcz 0.15 fraction or

• >= % combustibles 0.18 fraction

The parameters are all combustion zone (Cz) parameters.

Proposed Flare Combustion Zone Performance Parameters



For unassisted flaring, the combustion zone parameters are the

same as the flared gas parameters.

For assisted flaring, the combustion zone parameters need to

account for the steam assist or air assist flow rates

Proposed Flare Cz Performance Parameters



The current flare rule flare categorization scheme

applicable to all industry groups is:

Flare Categories for the Refinery Rule

The EPA proposed refinery rule categorization scheme will be:

• One set of rules for steam, non assisted and hydrogen rich flares with 3

parameter options (CzNHV, % LEL, % Combustible)

• Two sets of parameters are provided for flares with and without

hydrogen olefin interactions applicable to all the flare types

• One set of rules for air assisted flares with 3 parameter options

• Two sets of parameters are provided for flares with and without

hydrogen olefin interactions applicable to all the flare types

• Steam assisted flares

• Non assisted flares

• Hydrogen rich flares

• Air assisted flares

Being

Combined

into 1



There are seven unique types of flares with different

performance criteria.

There are subcategories of each of these.

Flare Categorization

• Steam Assisted

Flares

• Air Assisted Flares

• Non Assisted Flares

• Pressure Flares

• Ground Flares

• Enclosed Flares

• Hydrogen Rich

Flares



The refinery flare categorization scheme of “all flares” and “air

assisted flares” will not work for all of these 7 flare types.

• There needs to be separate criteria for large, medium and small

flares for all of these flare types.

Separate performance criteria is needed for each of these types

of flares.

Flare Categorization



Because of the variety of configurations within each of these

categories, the EPA will need to develop a clear methodology for

an Alternative Means of Emissions Limitation (AMEL) for flares.

An AMEL demonstration should be able to use external data that

is representative of the operating conditions and flare system

details.

Repeated site specific sampling and engineering studies should

not be required if external data is used that has been used for

other AMEL’s or is equivalent to data used to support other

AMEL’s

Alternative Means of Emission Limitation



The EPA proposed combustion zone parameters assume that

the steam is well mixed and is influencing the flame.

Issues with Steam Assisted Flares



Mixing at Low Flared Gas Flows

These two pictures, at low flare flows, show bright, efficient

flames and show that the steam is not influencing the flame.

To add fuel or prevent steam reduction by rule will not effect

flame performance when the steam is not well mixed with the

flame.



Visible Emissions

Is this a “visible emission”?

Answer – no - the combustion zone

extends beyond the visible flame.

The carbon is extinguished before

leaving the combustion zone

Is this a “visible emission”?

Answer – yes - the combustion zone

extends beyond the visible flame.

The carbon has left the combustion

zone and is “trailing” away from the

flare



To enable operation as close to the incipient smoke point as

possible, the following wording changes to Method 22 are

suggested:

• Current Language for Method 22 Section 3.5:

Smoke emissions means a pollutant generated by combustion in a flare

and occurring immediately downstream of the flame. Smoke occurring

within the flame, but not downstream of the flame, is not considered a

smoke emission.

Changes Needed for Method 22



Suggested Method 22 Changes

Not smoking

The puff is extinguished

Smoking -

Need a trailing

smoke plume

Suggested Revised Language for Method 22 Section 3.5:

Smoke emissions means visible emissions persisting beyond

one flame length from the visible flame tip. Smoke occurring

within the visible flame is not considered a smoke emission.



EPA must provide the ability to set site-specific flare tip velocity

evaluations when the equations of proposed §63.670(d) are not

appropriate.

The imposition of an artificial exit velocity restriction should not

be applied to flares as long as they are operated with a stable

flame.

Summary of ACC comments –Flare Tip Velocity Rules



Velocity Limits Set Based on Test Rig

Reference:

FLAME STABILITY LIMITS

AND HYDROCARBON

DESTRUCTION EFFICIENCIES

OF FLARES BURNING

WASTE STREAMS

CONTAINING HYDROGEN

AND INERT GASES

Walsh et. al.

American Flame Research

Committee, 2002 Fall Meeting

The 122 ft/sec upper velocity limit for hydrogen rich

flaring was set based on the capability of the test rig.



Air Products’ flares are currently sized for up to Mach 0.4

Hydrogen rich gases will remain completely stable up to sonic

velocity, which for hydrogen is very high (over 4,000 ft/s), with

the flame staying right on the flare tip.

Air Products’ Comments on Hydrogen Rich Flare Velocities



Air Products’ Comments on Hydrogen Rich Flare Velocities

The photograph below shows a pure hydrogen flame from a

horizontal release of 8 kg/s from a 2” straight pipe with 60

barg back pressure.

The flame remains firmly attached to pipe tip. The flame

length is approximately 50 meters.



Multiple emission testing programs have demonstrated that

pressure-assisted flares operate with a high combustion and

destruction efficiency and these flares are designed and

operated to have an exit velocity equal to sonic velocity, which is

~ 700 – 1,400 ft./sec depending on the gas mixture.

The ACC comments include a Dow Chemical Test Report for a

pressure assisted flare and for a small (2 “) steam assisted flare.

Steam Assisted & Pressure Assisted Flare Exit Velocities

The Dow Chemical Flare Test Report is provided in Attachment 1, p. 38 of the ACC Comments



Testing was conducted at the John Zink Co. test facility

Both extractive sampling and PFTIR were used

The pressure-assisted flare test results showed > 99.9 CE at exit

velocities ranging from 669 – 1101 ft/sec

The EPA rule would limit the exit velocity for these flares @ 400

ft/sec without special approval.

Maximum exit velocities should be determined based on flame

stability testing

The Dow Flare Study



Major Findings from the

Dow Flare Study

The key to high combustion

efficiencies and high destruction

efficiencies is a stable flame.

Dow concluded that future tests

should only be for flame stability only

and not attempting to sample and

analyze the flue gas.

There is an effect of heating value on

maximum exit velocity.

Flame stability testing can show what

that limit should be.



Enclosed Flares

Velocity and combustion zone properties for these types of

flares are different than air assisted, non assisted or steam

assisted flares.



In EPA's Applicability Determination Index (ADI), EPA Region 6

determined that an enclosed flare is not the type of flare that is

regulated by the open-flame flare specifications at 40 CFR

60.18.

An enclosed flare is characterized by the flame being totally

enclosed within the enclosed flare's structure and none of the

flame zone is exposed in the atmosphere as it is for an open-

flame flare

Enclosed Flare Regulation

U.S. Environmental Protection Agency, Applicability Determination Index Numbers 0000019, M000002 and

0000068.



The enclosed flare must comply with the testing procedures in

section 60.113b(c) of NSPS Subpart Kb for a closed vent system

and a control device other than a flare

As properly recognized by EPA in this ADI, enclosed flares

are distinguishable from open-flame flares and should not be

included in any future flare regulations.

EPA ADI for Enclosed Flares



Pressure flares and ground flares should be categorically exempt

from the flare standards since they are not similar to any of the

existing categories of flares.

Limits for these devices need to be set on a case-by-case basis.

Any available data, applicable to the flare installation and

operating details, should be able to be used to establish

performance parameters.

Pressure & Ground Flare Regulation



The EPA stated in April, 2012, that there is not enough data to

establish performance parameters for non-assisted flares

For non-assisted flares, the combustion properties in the

combustion zone are the same as the flared gas.

Petroleum refineries do not widely use non-assisted flares.

Approximately 10 % of refinery flares are non-assisted

No change to the non-assisted flare requirements based on data

for steam assisted flares is warranted and

Further it is not appropriate to combine non-assisted flares into

one “all flares" category.

Non Assisted Flares

USEPA, OAQPS, “Parameters for Properly Designed and Operated Flares”, April, 2012, Page 7-1

Comments on non assisted flares are found in Attachment 2, p. 88 of the ACC Comments



One of the data sets EPA used to support the development of

the existing rules was based on 1983 CMA/EPA test work

In the ACC comments, this data was used to assess the

adequacy of the proposed combustion zone parameters

The EPA proposed parameters are calculated for each of the

10 non assisted flare test data sets and compared to the test

data.

The point where it is estimated that less than 98 %

combustion efficiency is reached is compared to the new

parameters

Non Assisted Flare Performance



The test data and EPA performance parameters are compared

using a flammability diagram

Use of Flammability diagrams to analyze flare data is described

in EPA’s Flare Parameter Report

The approach was originally developed by Shell

Non Assisted Flare Performance



CMA/EPA Test Data for Non-Assisted Flaring

These 10 tests were from

an 8” flare burning an

80/20 propylene/propane

mixture inerted with

nitrogen at zero steam

flow

The tests are at varying

exit velocities

The samples were taken

from an elevated sample

probe located above the

visible flame



Comparison to TCEQ Work @ 350 BTU/scf

@ zero steam

CMA/EPA 1983 Test 11(a)

Propylene/Propane flow – 612 lb/hr Steam flow – 0 lb/hr

Nitrogen flow – 2489 lb/hr Steam/fuel ratio – 0

BTU content – 305 BTU/scf

Velocity – 58.7 ft/sec Flare Diameter – 8 “

CE – 99.8% % at 14.7 % capacity

TCEQ Test S 3.6



EPA Cz Parameters vs.Test Data

Combustion Zone

Parameters for the

CMA/EPA Zero Steam

Test Series

Move to

270 from 200 or

294 from 200 or

393 from 200



Use of Flammability Diagrams to Assess Flare

Performance

• The flammability diagram is a

diagram of flammability of the

fuel in inerts (either N2, CO2

or water (steam)).

• Mixtures above the

flammability diagram are fuel

rich and below the diagram

are fuel lean. Mixtures

without inerts operate on the

y axis.

• The flammability limits on the

Y axis are the LEL and UEL

for the fuel mixture in air.

• The mixtures start out as

mixtures without air and mix

with air and then proceed

through the flammability zone

to infinite dilution in air (0 , 0).At or near flame surface

Infinite dilution away from flame

At the base of the flame

In the stack



Flammability Diagrams for Mixtures

Flammability of CH4 in nitrogen

Cst – Stoichiometric fuel

composition in inert mixture

Inert composition @

Stoichiometric (I*)

UFL & LFL @ Stoichiometric

The flammability diagram for

methane – inert mixtures



Conclusions Non Assisted Flares

The combustion efficiency goal for good performance is

>98%. Emissions are normally calculated assuming a

98% combustion efficiency.

Based on the EPA/CMA test data set, a minimal emission

change is predicted to occur if any of the new parameters

are applied to non assisted flares.



The EPA is proposing to delete the 8% (vol.) requirement for

hydrogen rich flaring in the proposed Petroleum Refinery Sector

Rule.

In addition, the EPA is including hydrogen rich flares in an “all flares”

category in the proposed rule.

Hydrogen rich gas flaring in the chemical industry includes:

• Hydrogenation Reaction off gases

• Syn Gas production off gases

• Air Oxidation production off gases

• Other sources

Hydrogen Rich Flares

Hydrogen Rich Flare comments are found in comment Attachment 3, p. 94 of the ACC Comments



These gases have a low hydrocarbon content, generally <5%,

and usually can be flared without steam assist because these

gases have a low tendency to smoke.

Refiners don’t usually flare hydrocarbon lean, hydrogen rich

streams to non assisted or steam assisted flares

Hydrogen Rich Flares



Typical Air Oxidation Process Off Gas Composition



Comparison of EPA Proposed Cz

Parameters to an 8 % Hydrogen Mixture

The hydrogen rich system BTU/scf parameter approach does not

work. The EPA parameter is greater than 270 BTU/scf. The old

unassisted flare parameter was 200 BTU/scf.

The BTU/scf value at 8% hydrogen is 29 BTU/scf. This behavior is

why DuPont sponsored the flare study to develop an alternate

parameter for this set of flared gases.



Comparison of EPA Proposed CzParameters to an 8 % Hydrogen Mixture Hydrogen Mixture

The LELcz parameter for the 8% hydrogen case is 0.46 fraction.

The EPA parameter for LELcz is <= 0.15. The LELcz parameter here

is above 0.15 fraction.

A change to move to 0.15 fraction (by adding fuel) is not justified and

the LELcz fraction parameter does not appear to work for this

composition set.



Comparison of EPA Proposed CzParameters to an 8 % Hydrogen Mixture Hydrogen Mixture

The % combustible EPA parameter is > 0.18 combustible fraction.

The parameter at the 8% hydrogen case is 0.11 fraction.

A change to move this parameter to >.18 by adding fuel is not justified and

the % combustible parameter does not appear to work for this composition

set.



The fuel increase needed to achieve the various EPA performance parameters

To achieve 270 BTU/scf requires 385 ft3 natural

gas per 1000 ft3 of flared gas @ 8% H2

To achieve an LEL fraction of 0.15 requires 333 ft3

natural gas per 1000 ft3 of flared gas @ 8% H2

To achieve a 0.18 fraction combustibles requires

98 ft3 natural gas per 1000 ft3 of flared gas @ 8%

H2

None of these fuel addition measures are

predicted to result in a decrease in emissions.



Hydrogen Rich Gas Shown on a Flammability Diagram



24% Hydrogen Air Oxidation Off Gas Flare at night and during the day



The API provided extensive comments on the flare rules.

The API Comments are ~ 100 pages with numerous attachments

and are too comprehensive to review in 20 minutes

Key Comments are:

• Velocities above 400 ft/sec & smoking do not imply < 98 % CE

• Compliance with smoking and velocity limits during emergencies

can not be accomplished

• API is advocating for a 200 BTU/scf CzNHV for steam assisted

flares

API Concerns with the Proposed Flare Rules



The averaging time should be 3 hours vs. the EPA proposal of

15 min

The cost per ton of VOC and HAP removed are not justified

The combustion zone parameters proposed for flares with and

without hydrogen olefin interactions are not appropriate and are

not supported by available test data

The refinery flare test data does not include test data for a wide

variety of olefins.

The API is advocating that the requirement for automatic pilot re-

ignition systems be dropped.

Key API Comments



There is no new data that shows a need to change the regulatory

limit for:

Non assisted flaring @ 200 BTU/scf

Hydrogen rich unassisted flaring @ > 8 % hydrogen

If the limits are changed, existing data indicates minimal

emission reductions will occur

Separate, different flare performance criteria are needed for each

of 7 different flare types

Conclusions



The devil is in the details and include problems with:

• Visible Emissions

• Exit velocities

• Assist gas mixing with flared gas

• Flare categorization

• Averaging time for compliance parameters

• Time needed to comply with the standards

• Lack of regulations for large, medium and small applications

Conclusions



The devil is in the details and include problems with:

• Lack of a clear means to determine an alternative means of

emission limitation

• The combustion zone parameters expressed as a function of the

hydrogen to olefin ratio

• The EPA Flare NOx Emission factor change from 0.068 to 2.9

lb/MMBTU

Conclusions



ACC Comments are available at: Comment submitted by

Lorraine Krupa Gershman, Director, Regulatory/Technical Affairs,

ACC

• The ACC staff lead for the ACC comments is Lorraine Gershman

The ACC comments were prepared for ACC by Mike Dixon of

Dixon Environmental

The flare comments were prepared by a flare work group of flare

specialists and were reviewed by the ACC Air Issues Group

Acknowledgements/References

http://www.regulations.gov/



Continued

API Comments are available at: Comment submitted by Matthew

Todd, Regulatory & Scientific Affairs API

The Refinery rule proposal is available at: Petroleum

Refinery Sector Risk and Technology Review and New

Source Performance Standards; 40 CFR Parts 60 and 63

Proposed Rule; June 30, 2014 79 FR (2014-12167)

The regulatory docket and rule proposal and 203,000 +

comments are available at this link

Acknowledgements/References





The EPA Link for the Flare NOx Emission Factor comments is at:

• Emission Estimation Protocol for Petroleum Refineries |

Clearinghouse for Emission Inventories and Emission Factors |

Technology Transfer Network | US EPA

The comment period for this effort has been extended until April

20, 2015.

References

http://www.epa.gov/ttn/chief/consentdecree/index_consent_decree.html



Bruce C. Davis PE, QEP

Consultant - Air Quality Technology

DuPont Engineering Research & Technology

Environmental Engineering, Air Technology

Office: 281-586-2536 / Fax: 281-586-2504

Cell - 832-721-0350

[email protected]

mailto:[email protected]

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