Document ID: EPA-HQ-OAR-2008-0708-0524
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-08-12T04:00Z

----- Forwarded by Melanie King/RTP/USEPA/US on 08/05/2010 04:41 PM
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  |"Bromberg, Kevin L." <kevin.bromberg@sba.gov>                                                                                               
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  |Melanie King/RTP/USEPA/US@EPA, RobertJ Wayland/RTP/USEPA/US@EPA                                                                             
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  |"Higgins, Cortney" <Cortney_Higgins@omb.eop.gov>, "Kymn, Christine J." 
<Christine_J._Kymn@omb.eop.gov>, "Johnson, Nancy"                    |
  |<Nancy.Johnson@hq.doe.gov>                                                                                                                  
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  |08/05/2010 03:45 PM                                                                                                                         
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  |Catalyst Vendor Graph on NSCR sensitivity to AFR                                                                                            
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More information on NOx NSCR sensitivity, confirms earlier information from 
Colorado State University:

Kevin,

As discussed, there is an AFR versus emissions graph at a link from Johnson 
Matthey (catalyst vendor) which is similar to the NSCR graph provided a couple 
of days ago.  It does not include formaldehyde, but shows NOx, hydrocarbon and 
CO. It shows “percent reduction” (the previous graph showed actual post-
catalyst ppm values) but indicates the same technical issue – i.e., that 
reductions of CO and NOx occur over a vary narrow operating window – an AFR 
stoichiometric ratio range of about 0.003 in their graph. Also note that the 
x-axis covers a narrower range than the previous graph provided so the slope 
of the NOx curve is not as steep, but NOx performance is significantly 
impacted over an AFR stoichiometric ratio range of about 0.01.  You will 
recall that the definition of RB engine includes units with an SR of 1.1 or 
lower – so the lean side (on the right) goes much beyond the range shown in 
this graph. As an aside, this graph indicates similar trends as the graph 
provided earlier in the week so it reinforces that point.  The linked graph is 
an example representation from a control technology vendor, and the levels of 
reduction shown on the lean side (e.g., >90% for HC and 99% for CO) should not 
be taken literally.  I doubt that performance guarantees would be offered at 
those levels.

Here is the link:

http://ect.jmcatalysts.com/emission-control-technologies-three-way-catalysts