Document ID: EPA-HQ-OAR-2008-0708-0518
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-08-12T04:00Z

----- Forwarded by Melanie King/RTP/USEPA/US on 08/09/2010 11:16 AM
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  |"Bromberg, Kevin L." <kevin.bromberg@sba.gov>                                                                                             
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  |"Higgins, Cortney" <Cortney_Higgins@omb.eop.gov>, "Kymn, Christine J." 
<Christine_J._Kymn@omb.eop.gov>                                    |
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  |"Maresca, Charles A." <Charles.Maresca@sba.gov>, RobertJ 
Wayland/RTP/USEPA/US@EPA, Peter Tsirigotis/RTP/USEPA/US@EPA, "Mancini, Dominic   
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  |J." <Dominic_J._Mancini@omb.eop.gov>, Melanie King/RTP/USEPA/US@EPA                                                                       
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  |08/09/2010 09:15 AM                                                                                                                       
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  |NSCR Catalyst Will not deliver the 97% NOx reductions as estimated by EPA 
for 4SRB Engines                                                |
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Thanks EPA for the reply on Saturday that we’ve reviewed over the weekend, but 
the reply only reinforces our previous conclusion that NOx reductions will be 
seriously eroded in the field by more than a factor of two.  This supports our 
key request that 4SRB catalysts not be required for engines between 500 and 
705 HP.
First, I present a few key summary points.
The perception that large NOx co-benefits will result from the addition of 
NSCR on 4SRB engines is flawed based on the following:

·          NOx performance is very sensitive to the air to fuel ratio
(AFR) and needs to be “more fuel rich” or “air deficient” to achieve NOx 
reductions. This is documented in the graph questioned by Miratech and in the 
Johnson Matthey information.  In addition, the Miratech brochure (page 8/pdf 
page 12 of 65) also shows a VERY NARROW operating band for system performance 
(i.e., from about 0.986 to 0.996).  At leaner operation up to the rich burn 
definition of a stoichiometry of 1.1 (which is ~2% oxygen), NOx reductions in 
the Miratech “cartoon” are diminished (note that the Miratech picture does not 
show actual data, but presents common trends and generally agrees with the 
other two graphs).  Similarly, the MECA brochure supports that conclusion that 
NSCR performance for NOx is very susceptible to the AFR and that CO and 
hydrocarbon performance are better under leaner operation (see page 5, of page 
6 of 17);
·          An AFR set point for engine efficiency (e.g., about 1.05 to
higher) is in contrast with the richer set point requirements for NOx 
emissions reduction (i.e. higher fuel use).  (For example, Waukesha brochures 
indicate an excess air ratio of 1.06 for ”best economy” on rich burn engines 
and 0.99 for “Catalytic Converter Input (3-way)”.
Claim of NOx co-benefits at the leaner AFR set points (still within the common 
operating range for RB engines) is not accurate or supported by the “cartoon 
graphs” of two catalyst vendors (Miratech and Johnson
Matthey) or MECA;
·          Richer AFR set points results in higher operating
temperatures and increased maintenance.  Emissions of CO, hydrocarbon, and 
greenhouse gases (CO2 and methane), as well as ammonia (a particulate 
precursor) are also higher at richer set points).
Formaldehyde compliance (if a catalyst is required) is also assured at the AFR 
of 1.05 and higher.  Thus, there are multiple reasons for an operator to run 
leaner – and multiple benefits (for energy efficiency, engine operability, and 
emissions).
 Claims contrary to these points should be supported with data rather than 
“statements” (without supporting data and emissions warranties) from a vendor 
with obvious financial stakes in the outcome of the regulation. In addition, 
the vendor discusses damage from “over-oxygenation” in its email response to 
EPA.  However, the vendor brochure indicates that this is only in regard to 
NOx reduction (i.e., not formaldehyde performance) per page 11, and occur at 
higher than 2%
O2 (i.e., higher than a stoichiometry of 1.1). So, that discussion appears to 
be over-emphasized in the vendor email communication, but does indicate 
another mechanism for NOx performance to fail (while formaldehyde emissions 
would apparently not be compromised per the vendor brochure).

http://ect.jmcatalysts.com/emission-control-technologies-three-way-catalysts
We gave EPA two sources.  The EPA note describes only one source.  The second 
one from Johnson Matthey Catalysts is above.  I assume that Matthey is showing 
the latest technology on its website.  It also shows that the NOx reductions 
drop sharply for leaner AFR's above 99.8% AFR.
The source below shows that NOx reductions drops above 99% AFR.  The text 
below says that "This chart should be zoomed into a realistic area somewhere 
between 0.96 lambda (1.040 phi) and 0.99 lambda (1.010 phi).
This is an area where the AFR will be operating."  So there is absolute 
agreement between those two sources and the Miratech source that to achieve 
the significant NOx reductions, you need to have the engine operate between 
0.96 and 0.99.  This apparently was true of all the old and new catalysts.  
That is NOT the issue. We agree you can achieve NOX reductions IF you set in 
this region, and we said so.  However, it should also be acknowledged that the 
AFR “operating window” is very narrow, which speaks to our point in the 
difficulty in retaining this performance IF you are targeting NOx reductions.
 However, EPA provided us with a key diagram we didn’t have before showing 
graphically what we had said already – that the HCHO emissions reductions 
increase as you go leaner – and to maximize HCHO emissions you will go beyond 
the 0.96-0.99 area.  This graph (page 8 of the Miratch manual), shows that the 
best removals occur for AFR above .99 thru above 1.10.  Miratech also points 
out that you shouldn’t go above 2% oxygen (1.1 AFR) in order to avoid hurting 
the NOx reductions, but that note doesn't say that it hurts the HCHO 
reductions (the EPA note incorrectly says it hurts the ability to reduce “any 
pollutants” while the manual at page 11 references ONLY NOx).  And the graph 
shows that HC reductions continue to grow as the engine leans out.  It is also 
noteworthy that this is yet another mechanism that can result in performance 
failures for NOx.
 The EPA response appears to focus solely on the ability to meet the NOx
standard and not the ability to meet the HCHO standard.   The issue is
where will the engines be set IF in practice to meet an HCHO standard and will 
NOx reductions occur?  The Miratech and EPA notes do not say where the desired 
AFR window for HCHO is.  We believe that HCHO reductions will occur for AFRs 
that are greater than 100%, where NOx reductions do not occur, which is 
confirmed in the Miratch manual (which is CURRENT TECHNOLOGY).  What stops 
facilities from doing so in order to
reduce CO, ammonia, fuel efficiency, GHGs, and maintenance costs?   This
is the question posed by our earlier comments.  EPA didn’t really get a 
response on the key issue.
 Looking at curve in Figure 2 of the MECA 1997 Report, it appears that the 
NMHC control improves as you move from 99% to above 100%.  To the extent that 
EPA sets an aggressive HCHO standard, the engine is even less likely to 
achieve NOx reductions, because it will stay off the rich side of the rich 
burn engines. This is consistent with the Miratech graph.
 However, EPA does point out this part:  “ shows in Figure 2 that the NMHC 
reductions will decrease as you lean out the engine.”  This implies that you 
can’t go too lean, or you would lose the HCHO emissions also – so is this true 
of other current NSCRs?  And how wide is the lean window where NOX reductions 
won’t occur?  The reduction in HC emission reductions, however, is not shown 
in the Miratech manual. Since the MECA cartoon has little detail, appears to 
present both rich burn and lean burn operating ranges, and is not consistent 
with others, we expect that cartoon is not representing a negative impact on 
HC performance within the “leaner” range for rich burn engines.
 Judging from the graph on page 8 of the Miratech manual, in the desired AFRC 
window for control, which is narrowly centered around 99%, the NOx reductions 
appears around 90%, not 97%, which is only a small reduction from 97%.  But I 
would say the concern is that to get additional HC reductions, you actually go 
past 1.0.  But the mfger says that you can damage the ability to reduce NOx 
permanently if you go beyond 2% oxygen for extended periods of time (A/F ratio 
of 1.1 at 2% oxygen)  But that wouldn’t stop a facility from doing so, because 
he’s setting for HCHO reductions, not NOx.  And if EPA sets an aggressive HCHO 
standard, more facilities will need to go leaner than 99% to get to 
compliance, and will forego some or most of the NOx reductions.  In the 
Miratech graph, the NOx reductions do not go to zero, unlike the Colorado 
State University results.
 In sum, the NOx reductions may not go to zero, but the Actual Data, and MECA 
and Johnson Matthey cartoon graphs all show a steeper decline in NOx 
performance than the Miratech cartoon. In the leaner area more favored by HCHO 
compliance, the NOx reductions go from 97% to somewhat under 10% (according to 
Miratech’s cartoon graph).  So the NOx reductions can easily be cut by half or 
more by going into the lean area according to Miratech’s own brochure. 
Therefore, the EPA response did not rebut our concern - and now we have 
quantified the effect as somewhere between a 95% reduction under optimal NOx 
reductions conditions and maintaining a narrow AFR set point and a no NOx 
reduction for individual engines when operating lean.
   ----- Original Message -----
From: King.Melanie@epamail.epa.gov <King.Melanie@epamail.epa.gov>
To: Higgins, Cortney
Cc: Talcott.Fred@epamail.epa.gov <Talcott.Fred@epamail.epa.gov>; 
Wayland.Robertj@epamail.epa.gov <Wayland.Robertj@epamail.epa.gov>;
horowitz.michael@epamail.epa.gov <horowitz.michael@epamail.epa.gov>

Sent: Fri Aug 06 22:59:07 2010
Subject: Fw: Catalyst windows

Hi Cortney,
I am forwarding the email below in response to SBA's claim that NOx reductions 
would not be achieved through the use of NSCR on 4SRB engines.  This is 
information from Miratech who is a large supplier of catalyst technology.

See also their catalyst manual which is attached, which discusses the 
potential to over-oxygenate the catalyst if you run it at too high of an

O2.  See at the top of p. 11.  According to Miratech, saturating it with

too much O2 would result in the catalyst losing the ability to reduce any 
pollutants.

I would also reference the information on p. 5-6 in the attached report from 
MECA.  It says "NOx conversion efficiency drops dramatically when the engine 
is run in the lean regime, while NMHC and CO conversion efficiency also 
declines somewhat." and shows in Figure 2 that the NMHC reductions will 
decrease as you lean out the engine.
(See attached file: icengine.pdf)(See attached file: Catalyst Operating Manual 
- 012909B.PDF)

Melanie King
Energy Strategies Group
Sector Policies and Programs Division
Office of Air Quality Planning and Standards U.S. Environmental Protection 
Agency

Mail Code D243-01
RTP, NC  27711

Phone:  (919) 541-2469
Fax:       (919) 541-5450
king.melanie@epa.gov
----- Forwarded by Melanie King/RTP/USEPA/US on 08/06/2010 10:38 PM
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  |"Kevin O'Sullivan (MIRATECH)" <kosullivan@miratechcorp.com>
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  |Melanie King/RTP/USEPA/US@EPA
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  |"David Zenthoefer" <dzenthoefer@miratechcorp.com>
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  |08/06/2010 06:04 PM
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  |FW: Catalyst windows
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Melanie –

We haven’t met – and David was tied up so I reached out to one of our experts 
and his abridged response is below.  As you can see, we believe the original 
investigator is dealing with dated and limited material.
I’m not much on sugar coating – so my simple synopsis is if you’re designing 
rules on the information provided us to respond to, there is a

lot more work to be done and more technology to understand than what we were 
presented.

I’d be pleased to discuss this in more detail with you or the investigator.

My best -

Kevin

Kevin R. O'Sullivan, President and Chief Operating Officer,   MIRATECH
Corporation
Primary:  918.628.6110 (Office Direct), Alternate: 918.630.1658 (Cell)

Emission Solutions for Industrial Engines: kosullivan@miratechcorp.com or 
www.miratechcorp.com
Fax: 918.933.6220, 420 South 145th East Avenue, Mail Drop A  Tulsa, OK
74108 - 1305

From our consultant:

I've looked over this BS and it looks to me like whoever submitted this to the 
EPA is banking everything off of data that they have collected years back or 
with catalyst that were manufactured years ago. Looking at

what he is saying, he has a catalyst that is using the older loadings and 
designs that only give 90% reduction. The current 0.5 gram catalyst is 
achieving 96 to 97% reduction.

The next thing that he is basing his information on is a very narrow operating 
window (lambda window). Most catalyst manufactures today have opened the size 
of the operating window allowing a greater deviation in the AFR control and 
still be within the desired emissions levels.

He is defining a Rich Burn engine as an engine with a Lambda setting of 1.10. 
I believe the EPA defines any engine running with 2 percent of oxygen or less 
to be a rich burn. A few years back they defined it as 4%

or less. Everyone in the free world that has ever seen a catalytic converter 
knows that it must operate at 0.5% or less.

The chart that the guy provided, in my opinion, is not accurate. Of course you 
can get these readings with as large of a swing that they are

inducing on the AFR and catalyst. This chart should be zoomed into a realistic 
area somewhere between 0.96 lambda (1.040 phi) and 0.99 lambda

(1.010 phi). This is an area where the AFR will be operating. The ammonia 
levels that he is showing is higher than anyone would expect.
Typically you start smelling ammonia at about 30 ppm. They are saying that 
this level is showing up at about 0.985 lambda.

Lastly, the AFR issue. If they are testing with a low end system, yes they 
will have problems maintaining the operational window. The better the 
controller, the tighter the hold on the operational window.

The bottom line is, these guys are throwing both the AFR and catalyst under 
the bus with data from only one source. Modern AFR technology and modern 
catalyst technologies are far more superior that the older stuff.

-----Original Message-----
From: David Zenthoefer
Sent: Friday, August 06, 2010 9:19 AM
To: John Sartain; Kevin O'Sullivan (MIRATECH)
Subject: FW: Catalyst windows

Kevin,

Can you take a pass at this for the EPA, this is helping to finalize the

NESHAP rule due out next Tuesday.

David

David Zenthoefer, Vice President - Sales and Service MIRATECH Corporation
Primary: 918.640.1140 (Cell)

Emissions Solutions for industrial engines: dzenthoefer@miratechcorp.com

or www.miratechcorp.com
Fax: 918.933.6236, 420 South 145th East Ave, Tulsa, OK 74145-4712

-----Original Message-----
From: King.Melanie@epamail.epa.gov [mailto:King.Melanie@epamail.epa.gov]

Sent: Friday, August 06, 2010 9:01 AM
To: David Zenthoefer
Subject: Re: Catalyst windows

Hi David,
Thanks so much to you and John for speaking with me this morning.  The issue I 
am trying to resolve is whether you will get NOx reductions from

a 3-way catalyst that is installed on a rich burn engine to meet CO or VOC 
emission standards.  The argument that is being made is that they will set the 
engine up specifically to get the CO/VOC reductions and not

achieve any NOx reductions since they aren't trying to meet a NO limit as 
well.  Below I have copied the information that was sent to us by one

of the interagency stakeholders who is suggesting that little to no NOx 
reductions will be achieved.  From speaking with you this morning, my 
understanding is that running the engine too lean will saturate/poison the 
catalyst and the reductions of all 3 pollutants will be decreased.

Below is the information that was sent to me by the interagency reviewer

to support the claim that little to no NOx reductions will occur:

If you get NOx reduction with NSCR it is usually relatively high – e.g.,

90% or more.  The problem is that the NOx performance is very sensitive to the 
air to fuel ratio (AFR) and the stream needs to be “more rich” (i.e., more 
fuel rich or air deficient).  A lesser NOx reduction (e.g., 20 – 60% NOx 
reduction) with NSCR is typically not seen, because the performance curve 
(versus AFR) is very steep – meaning that you go from no NOx reduction to 
relatively high NOx reduction (e.g., 80% or
more) with very small changes to AFR.  Similarly, if set for “richer”
operation with NOx reduction, relatively small changes in AFR can move the AFR 
more lean and significantly impact NOx performance.  Thus, if an

operator installs NSCR to meet a NOx limit, the set to provide a better 
assurance of emission performance is often accomplished by establishing a 
“richer” set point (which can result in significant ammonia emissions).  In 
this scenario, there is more of an operating window before minor AFR changes 
can move “too lean” and significantly compromise NOx performance.  Those 
richer set point also result in lower

efficiency / higher fuel use, more hydrocarbon (HC) emissions, and hotter 
operation – and these conditions affect maintenance requirements because the 
HC and higher temps impact performance and increase maintenance frequency (and 
related costs).

An example of NOx (post NSCR catalyst) versus AFR for a RB with NSCR is 
provided here. Note the “stoichiometric ratio” (SR) is the theoretical amount 
of air relative to the amount required to burn all of the fuel – i.e., at 1.00 
there is just enough air to burn all the fuel.  From the scale on the x-axis, 
a change in the amount of air by 1 or 2% dramatically changes the NOx 
emissions (and ammonia and CO emissions).
This level of AFR control is difficult to maintain on a continuous basis. It’s 
also not reasonable to operate in a region of the “NOx curve” that provides 
intermediate levels of NOx reduction so in general NOx reduction with NSCR 
close to an all or nothing proposition. Also – as a reminder, the definition 
of “rich burn” is an engine with a stoichiometric ratio up to 1.10 (beyond the 
scale of this graph).  As you can see from the graph, the NOx emissions on the 
right side of the graph (from SR of about 0.99 or higher) have high NOx 
indicative of very

little or no NOx reduction.  This relates to our discussion that NOx 
reductions cannot be presumed with NSCR – and operators can achieve better 
efficiency, lower fuel use, and lower greenhouse gas emissions by

running leaner where NSCR will not reduce NOx.

Also for the NOx data – the marginal relative change in the 3 data points to 
the right (from about 2100 to about 2650 ppmv) is due to changes in the inlet 
NOx and not from NSCR reduction – i.e., the inlet NOx versus AFR is also 
dependent on AFR at this operating threshold where you cross from “rich” to 
“lean”, and the NOx reduction across the catalyst is insignificant.  Note that 
the one NOx point at about 850 ppmv is 58% reduction and the three low NOx 
points on the left are about

98% reduction for these tests.

(Embedded image moved to file: pic10264.gif) Since facilities will be 
attempting to meet an air toxics standard, the preferred operation will use a 
stoichiometric ratio of 0.99 or more, which would be on the “fuel lean” side 
(right hand side) of the graph.
However, the NOx reductions will only occur on the rich side (left hand
side) of the graph – in this case approximately 0.98 or less.  In addition to 
good HCHO emissions performance, there are additional reasons for being on the 
lean side of the curve – reduced fuel consumption, associated reductions in 
greenhouse gas emissions (i.e., lower CO2 and methane), reduced maintenance, 
and avoidance of ammonia and CO emissions.  The NOx reductions go very quickly 
from roughly 98% to 0% once you move from richer settings to leaner operation 
above about

0.98.   Also, the air to fuel ratio differences are very small and given

some instability of the settings of these engines, maintaining a precise

setpoint is difficult and you will need to set an even leaner setting optimize 
engine operability and effieciency – or, conversely, set a
richer setting to ensure NOx reductions.   The above graph is from a
rich burn engine tested by Colorado State University. Unless EPA is also

setting a NOx limit with the HCHO limit, these desired NOx reductions are 
unlikely to occur.

EPA may wish to review additional data to see how under what AFR ratios,

both the HCHO number and the desired NOx reductions can occur (by how much and 
whether these overlap), although I don’t know how this result can be achieved 
under the current standard.

Melanie King
Energy Strategies Group
Sector Policies and Programs Division
Office of Air Quality Planning and Standards U.S. Environmental Protection 
Agency

Mail Code D243-01
RTP, NC  27711

Phone:  (919) 541-2469
Fax:       (919) 541-5450
king.melanie@epa.gov

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  |"David Zenthoefer"
<dzenthoefer@miratechcorp.com>
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  |Melanie
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  |08/06/2010 09:39
AM
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  |Catalyst
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David

David Zenthoefer, Vice President - Sales and Service MIRATECH Corporation
Primary: 918.640.1140 (Cell)

Emissions Solutions for industrial engines: dzenthoefer@miratechcorp.com

or www.miratechcorp.com
Fax: 918.933.6236, 420 South 145th East Ave, Tulsa, OK 74145-4712 [attachment 
"Catalyst Operating Manual - 012909B.PDF" deleted by Melanie

King/RTP/USEPA/US]

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