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HAWK21M
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Catalytic Converter - AC Packs

Tue Aug 18, 2020 5:10 pm

The Catalytic Converter used in the Air conditioning system of a B757 series , upstream of the Flow control valve
Any idea what is the material used inside the unit that converts Ozone to Oxygen.
I may not win often, but I damn well never lose!!! ;)
 
EssentialPowr
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Re: Catalytic Converter - AC Packs

Tue Aug 18, 2020 9:05 pm

I believe BNSF makes the catalytic converter; my guess is they consist of platinum or palladium. Since those metals aren’t consumed by the reaction, the converters should have a long life. Temps above about 600 degrees F decompose the Ozone as well so my guess is those temps are found upstream of the pack control valves in flight. For ground ops my further guess is the catalytic converter is bypassed.
 
EssentialPowr
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Re: Catalytic Converter - AC Packs

Tue Aug 18, 2020 9:50 pm

The 737 doesn’t have them and so gets routed around hi ozone forecasted areas, typically northern North American ops
 
kalvado
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Re: Catalytic Converter - AC Packs

Tue Aug 18, 2020 11:06 pm

Looks like manganese dioxide is another option. Definitely cheaper than platinum, and likely does CO oxidation as a side job.
http://wcponline.com/2001/03/15/catalyt ... emissions/
 
EssentialPowr
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Re: Catalytic Converter - AC Packs

Wed Aug 19, 2020 1:01 am

kalvado wrote:
Looks like manganese dioxide is another option. Definitely cheaper than platinum, and likely does CO oxidation as a side job.
http://wcponline.com/2001/03/15/catalyt ... emissions/


Noted; that ref shows magnesium dioxide optimal at 22C. The bleed temp prior to the pack is considerably hotter than that; don’t know about its effectiveness as a catalyst at much higher temps.
 
EssentialPowr
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Re: Catalytic Converter - AC Packs

Wed Aug 19, 2020 1:02 am

The company is BASF, not the railroad...
 
kalvado
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Re: Catalytic Converter - AC Packs

Wed Aug 19, 2020 1:40 am

Digging it deeper - I can see 3 patents (now expired) for ozone decomposition catalysts held by BASF or Engelhard (now BASF catalysts). There is a bit of discrepancy with dates as BASF catalysts didn't exist when patents were active, but anyway.
All 3 describe some sort of oxide layer, looks like iron oxide is a must, with platinum or palladium coating
https://patents.google.com/patent/US4343776A/en
https://patents.google.com/patent/US5620672A/en
https://patents.google.com/patent/US5422331A/en
 
EssentialPowr
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Re: Catalytic Converter - AC Packs

Wed Aug 19, 2020 1:47 am

kalvado wrote:
Digging it deeper - I can see 3 patents (now expired) for ozone decomposition catalysts held by BASF or Engelhard (now BASF catalysts). There is a bit of discrepancy with dates as BASF catalysts didn't exist when patents were active, but anyway.
All 3 describe some sort of oxide layer, looks like iron oxide is a must, with platinum or palladium coating
https://patents.google.com/patent/US4343776A/en
https://patents.google.com/patent/US5620672A/en
https://patents.google.com/patent/US5422331A/en


Excellent work, thank you
 
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HAWK21M
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Re: Catalytic Converter - AC Packs

Thu Aug 20, 2020 4:37 pm

kalvado wrote:
Digging it deeper - I can see 3 patents (now expired) for ozone decomposition catalysts held by BASF or Engelhard (now BASF catalysts). There is a bit of discrepancy with dates as BASF catalysts didn't exist when patents were active, but anyway.
All 3 describe some sort of oxide layer, looks like iron oxide is a must, with platinum or palladium coating
https://patents.google.com/patent/US4343776A/en
https://patents.google.com/patent/US5620672A/en
https://patents.google.com/patent/US5422331A/en


Impressive.....I remember someone once mentioning Gold....But I think that would raise the cost of the product significantly.

And to mention there is no Bypass to the Catalytic converter for Ground mode on the B757 ,All Pack inlet Airflow to the FCSOV has to go thru it.
I may not win often, but I damn well never lose!!! ;)
 
kalvado
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Re: Catalytic Converter - AC Packs

Thu Aug 20, 2020 4:48 pm

HAWK21M wrote:
kalvado wrote:
Digging it deeper - I can see 3 patents (now expired) for ozone decomposition catalysts held by BASF or Engelhard (now BASF catalysts). There is a bit of discrepancy with dates as BASF catalysts didn't exist when patents were active, but anyway.
All 3 describe some sort of oxide layer, looks like iron oxide is a must, with platinum or palladium coating
https://patents.google.com/patent/US4343776A/en
https://patents.google.com/patent/US5620672A/en
https://patents.google.com/patent/US5422331A/en


Impressive.....I remember someone once mentioning Gold....But I think that would raise the cost of the product significantly.

And to mention there is no Bypass to the Catalytic converter for Ground mode on the B757 ,All Pack inlet Airflow to the FCSOV has to go thru it.

Gold doesn't work great as a solid state catalyst. And platinum group is as expensive, if not more expensive than gold anyway,
 
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HAWK21M
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Re: Catalytic Converter - AC Packs

Thu Aug 20, 2020 5:11 pm

Understandable Cost factor matters....So a less valuable , more effective metal that would be preferred to convert Ozone to Oxygen
I may not win often, but I damn well never lose!!! ;)
 
kalvado
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Re: Catalytic Converter - AC Packs

Thu Aug 20, 2020 6:11 pm

HAWK21M wrote:
Understandable Cost factor matters....So a less valuable , more effective metal that would be preferred to convert Ozone to Oxygen

We're talking maybe a few thousand dollars worth of metal, if not less. Not really a cost factor for an airplane.
Car converters use single-digit number of gramms of Pd, and probably have similar geometry.
If anything, weight would be a bigger consideration as that directly translates into fuel burn.
 
EssentialPowr
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Re: Catalytic Converter - AC Packs

Thu Aug 20, 2020 6:54 pm

HAWK21M wrote:

And to mention there is no Bypass to the Catalytic converter for Ground mode on the B757 ,All Pack inlet Airflow to the FCSOV has to go thru it.


Ok. Didn’t have a diagram handy; Sounds like your question is answered.
 
strfyr51
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Re: Catalytic Converter - AC Packs

Thu Aug 20, 2020 8:38 pm

kalvado wrote:
HAWK21M wrote:
kalvado wrote:
Digging it deeper - I can see 3 patents (now expired) for ozone decomposition catalysts held by BASF or Engelhard (now BASF catalysts). There is a bit of discrepancy with dates as BASF catalysts didn't exist when patents were active, but anyway.
All 3 describe some sort of oxide layer, looks like iron oxide is a must, with platinum or palladium coating
https://patents.google.com/patent/US4343776A/en
https://patents.google.com/patent/US5620672A/en
https://patents.google.com/patent/US5422331A/en


Impressive.....I remember someone once mentioning Gold....But I think that would raise the cost of the product significantly.

And to mention there is no Bypass to the Catalytic converter for Ground mode on the B757 ,All Pack inlet Airflow to the FCSOV has to go thru it.

Gold doesn't work great as a solid state catalyst. And platinum group is as expensive, if not more expensive than gold anyway,

I don't think it's the expense as much as the longevity of the unit. They're rarely replaced for anything other than cleaning I can only remember one ever having been replaced on the line and that was a bird strike that entered the pack inlet and fouled the entire pack system so it had to be removed to be sent to the shop for cleaning.
I've never seen one removed for any other reason though..
 
kalvado
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Re: Catalytic Converter - AC Packs

Thu Aug 20, 2020 8:56 pm

strfyr51 wrote:
kalvado wrote:
HAWK21M wrote:

Impressive.....I remember someone once mentioning Gold....But I think that would raise the cost of the product significantly.

And to mention there is no Bypass to the Catalytic converter for Ground mode on the B757 ,All Pack inlet Airflow to the FCSOV has to go thru it.

Gold doesn't work great as a solid state catalyst. And platinum group is as expensive, if not more expensive than gold anyway,

I don't think it's the expense as much as the longevity of the unit. They're rarely replaced for anything other than cleaning I can only remember one ever having been replaced on the line and that was a bird strike that entered the pack inlet and fouled the entire pack system so it had to be removed to be sent to the shop for cleaning.
I've never seen one removed for any other reason though..

As a guess... Catalytic activity, especially with ozone in the game, should do something for oxidation of any junk in the system. If there is at least some filtering, I would expect no real accumulation inside.
If you think about it, somewhat similar catalytic converters last for 10+ years in cars as well - feeding on engine exhaust....
 
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HAWK21M
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Re: Catalytic Converter - AC Packs

Thu Aug 27, 2020 6:14 pm

strfyr51 wrote:
kalvado wrote:
HAWK21M wrote:

that was a bird strike that entered the pack inlet and fouled the entire pack system so it had to be removed to be sent to the shop for cleaning.
I've never seen one removed for any other reason though..


Ram Air Inlet & FCSOV Inlet are different areas, how would a bird strike in the former affect the latter.
I may not win often, but I damn well never lose!!! ;)

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