Home made Diesel Catalyst Stupid Idea?

[vdubnut62]

Ok so to cut to the chase, I want to run a catalyst on the exhaust of my Changfoid and Listeroid diesel gennys. The idea is to raise exhaust heat and maybe clean up a little of the soot?
Will a junkyard run of the mill car catalyst work on a diesel?  Will I have to have some sort of regen cycle, yes I do know that regens are to burn out the DPF primarily.
My old Dodge had a catalyst with no DPF, so I am assuming that would work for me.
And I don't want to create a new problem with the implementation of the cat.
Just throwing this up against the wall to see what sticks.
Ron.

[Henry W]

I like the idea. The reason why is more heat for CHP. Years ago I was at Mike Monteth's shop to pick up my GM-90 and he was working on a project on one of his GM-90's. It had a catalyst. At the time he said it passed Tier 3 EPA emission standards according to his exhaust analyzer and he was trying to get these engines certified. It never worked out because of the deep pockets that's needed to have the EPA test an engine at their testing facilities. So it is possible.

What size and type of catalyst that will work, I don't know. Bob G and I were talking about this years ago. He might be able to shine some light on this.

Henry

[Henry W]

Here are some topics I found:

http://www.microcogen.info/index.php?topic=690.0


https://listerengine.com/smf/index.php?topic=4168.0


https://listerengine.com/smf/index.php?topic=3111.0

[vdubnut62]

Thanks Henry, more heat for CHP is what I am after. Primarily, this is not a CHP setup per say, but more of a backup generator setup
that just happens to be in proximity to my cobbled up woodboiler. Being sort of a try it and see what happens sort of guy, yeah this whole thing has gotten out of hand.
I will someday, if I live long enough, post pictures of the monstrosity.
Ron

[Tom Reed]

I'm doing CHP and the idea of more heat is a attractive to me. I wonder how a wood stove catalyst would perform in a diesel environment. Heat extraction after the catalyst might resolve the soot issues which is why I'm only extracting heat from the coolant right now.

[mike90045]

There are particulate filters that trap the soot and then it is burned off, which is something the D.E.F. is supposed to do in the regen cycle. And  that's about the end of my retained knowledge of that system

I would thing  a water bath muffler - bubbling the exhaust through water, would trap a lot of the soot, and give warm water

[vdubnut62]

Hello Mike!  DEF is an acronym for Diesel Exhaust Fluid, that is the crap that smells like  pee, and it is metered in  to reduce the levels of NOx.
There is an SCR  (selective catalytic reduction) in there that is sort of a Catalyst that uses DEF for something that I simply do not understand, perhaps one of the more learned members could chime in and correct my assumptions.

The DPF is an acronym for Diesel Particulate Filter, that is supposed to trap soot and at a certain point, extra fuel is injected to burn the soot off and clean the filter.

All in all, the whole thing sounds pretty Mickey Mouse to me but I am admittedly not the sharpest tool in the shed.

Here is what I don't get - How do you burn more fuel to produce less emissions?

Also does the catalyst get hot enough to reduce the soot levels? Some, none, maybe a little bit?

I found this on Google. (Is this plagiarism? )

-----The diesel oxidizing catalyst (DOC), similar to a catalytic converter in gasoline engines, requires at least 662 °F to function. An exhaust cooler reduces the temperature of the exhaust gas before it exits the tailpipe

I'm just not sure that a naturally aspirated diesel will get hot enough to light the thing!  Although I have never had an exhaust temperature gauge on my changfoid I do have 'em on the shelf ready to go when everything is ready.

Ok Google again on automotive catalysts
------Exhaust catalysts usually operate in the temperature range 150–600 °C,(300 to 1100 °F) but they can experience temperatures of up to 1000 °C (a little over 1800°F). The conditions that can produce such high temperatures include repeated misfire (resulting in the oxidation of large amounts of unburned fuel over the catalyst) and high driving speeds.

I guess I am comparing apples to oranges, Google (crap google is EVERYWHERE!) says there are supposedly little or none of the precious metals platinum, palladium, and rhodium in a diesel cat?
   Help! 
Ron.

[mobile_bob]

Ron

just got some time to read what you posted and have a few thoughts to share, remembering you get what you pay for??



maybe 12 years ago or more, when i was doing all the testing of the s195 based trigen, i also was interested in some sort of catalyst to increase the heat value of the exhaust, thinking maybe the carbon particulate and any unburned hydrocarbons might be burned and raise the exhaust heat value a bit.

i found a small cat that looked like it might be useful for the task, and a forum member at the time sent me a high temp blanket to wrap it up with, but i never got around to putting it on and testing it.

my thinking at the time was i probably would have to remove it periodically to mechanically or chemically clean it out, as in my experience gas engines that burn oil seem to clog the cat with carbon, of those i would remove them and using a dead blow hammer moderately beat the crap out of the casing to dislodge the carbon and then reinstall the thing and off it would go again.

then i thought about maybe making my own reactor (not really a cat, because i have no catalyst)

i asked the guys over on the practicalmachinist forum for some stainless steel swarf (metal curls off a lathe) and was sent a big box of nice long curly ques (a technical term)

what i was considering doing was loosely packing a short piece of tubing maybe 4" diameter, likely stainless too
and then making up some clay slip (the stuff ceramics folks use to coat their creations before firing) use this slip in a
runny form and coat the interior and the curls of stainless, let it sit upright, drip out and let it dry and take it to a ceramic shop to have the thing fired.  the goal would be all those curls now with a thin ceramic coating on them.

i thought i would then introduce the diesel exhaust off the s195, and maybe also put a smog pump to add more air to the exhaust along with a measure stream of propane of nat gas and maybe a spark plug to assure ignition.  running the mixture on the lean side so that the heat would increase and ceramic coated stainless curls could catch the carbon and unburned hyrdocarbons and with the added air and gaseous fuel a complete burn could be assured along with much higher exhaust temperatures.

i am sure there would be issues with elevated Nox probably, but i think it would burn so cleanly that at least there would be no visible smoke coming out the tailpipe. and the elevated temps along complete burn of the carbon and unburned hyrdocarbons would extend the efficiency of the exhaust heat efficiency.

at least that was my thought?

i still have all the stuff, and my 86 yo mother has the clay slip and the ceramic kiln to fire it with
so aside from ordering a chunk of stainless exhaust pipe, i have everything to try it out with,,, just don't seem to have the time and when i do have the time... physically i just can't do what i once was able to do!

if i could just find a local kid that wanted to hang out and have some fun that didn't include either a tv video game or a smart phone?

ya, good luck with that last one bob!

anyway long story short?

i think your idea has merit! and there ought to be a way (or three ) to get done what you are contemplating.

bob g

[vdubnut62]

Thanks Bob! I seem to be facing some of the same issues that you are. My Wife and I had COVID back in August, and things have not taken a turn for the better after.
It just gets harder to get anything done.
  Anyway thanks for the input!

Ron

[Westcliffe01]

Hello Ron

The precious metal on oxidation catalysts is usually formulated to start working at about 280-300C and the substrate has a lower cell density (bigger cells with more open area) than is typically the case with a gas engine.  Gasoline engines have catalysts that are formulated differently to produce the best emissions at a stoichiometric air fuel ratio (never the case with a diesel) but they still have platinum or paladium in them so will react at the kinds of "normal" temperatures (right around 300C).   There is just a greater risk of plugging the cells of a gas converter if the diesel runs too cool and wet.

So one of the key things would be to have a thermocouple or RTD after the substrate and after warming up the engine you need to apply a good load to get the temperature of the exhaust up.   As the catalyst comes on line, the exhaust temp should go up without a load chaange and from that point it should be self sustaining, unless the load gets too low and the temperature drops off.   But your instrumentation will tell you that.  One could use an analog gauge that one uses in the stack of a wood stove (the type that penetrates into the bore of the pipe and hangs onto the pipe with a magnet).  Then all you would need to do is re-calibrate the scale of the dial to indicate too cold, operating and too hot...

It may also be helpful to measure the backpressure on the engine side of the catalyst so that you get a warning if the catalyst plugs up, so that you dont burn a valve or worse.  One could use a pressure switch for this, but that really depends on how constant the load is since the pressure will vary with engine speed.

[cujet]

I've been wanting a diesel oxidation catalyst for my 2 listeroids, my Kubota diesel and my mini Changfa. Quite simply, I can't stand the smell of diesel engines. My old VW TDI had an exh leak and smelled horrible, so I know the engine was making stinky exhaust. But the single catalyst (it did not have the more modern system) did a wonderful job of cleaning up the smell.

I'd love to find similar catalytic converters for my engines. Looking on Amazon and Ebay, all the diesel specific cats are gone. Most are simply universal cats.

Even the name brand guys no longer carry diesel cats.