Document ID: EPA-HQ-OAR-2008-0708-0520
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 11:58 AM
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  |Melanie King/RTP/USEPA/US                                                                                                                 
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  |Cortney_Higgins@omb.eop.gov                                                                                                               
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  |Fred Talcott/DC/USEPA/US@EPA, RobertJ Wayland/RTP/USEPA/US@EPA, Michael 
Horowitz/DC/USEPA/US@EPA                                          |
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  |08/06/2010 10:59 PM                                                                                                                       
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  |Fw: Catalyst windows                                                                                                                      
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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"
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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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