Thread: Biodiesel and Particulate Filters (DPF)

I must admit to some confusion between the terms Catalytic Converter and Diesel Particulate Filter. We've heard about petrol engined Cat Converters and how they use rare metals and the high Exhaust gas Temperature to convert "Bad Gases" to Good Gas" emissions. Is a DPF basically the same thing as a Cat Converter? By reading this report, it describes using a "Catalysed DPF". Isn't this a Cat Converter? I had suspected that Cat Converters might have not worked so well with BD due to a) reduced amounts of particulates to act as "Fuel" and b)reduced EGTs to fire up the reaction.

Originally Posted by Gunner

I must admit to some confusion between the terms Catalytic Converter and Diesel Particulate Filter. We've heard about petrol engined Cat Converters and how they use rare metals and the high Exhaust gas Temperature to convert "Bad Gases" to Good Gas" emissions. Is a DPF basically the same thing as a Cat Converter? By reading this report, it describes using a "Catalysed DPF". Isn't this a Cat Converter? I had suspected that Cat Converters might have not worked so well with BD due to a) reduced amounts of particulates to act as "Fuel" and b)reduced EGTs to fire up the reaction.

Hi there
Point well made from both the above writers Really the report that Goss pointed out states quite clearly that the use of a DPF with a 20 or 100% biodiesel is a very good PLUS Lower emmissions as well as a shorter regeneration time of the catalytic material used They do make the point and mention that there is a 5% penalty on fuel consumption in this test with 100% biodiesel 2% with the B20
It is interesting to note that the Oekotek monforts site on biodiesel in Germany lists a whole host of manufacturers that approve the use of biodiesel in their engines
I am not so sure that we are not taken for a bit of a ride in this country in so far as what the car manufacturers are telling us
The amount of testing done on biodiesel has been enormous with all the results very positive apart from the higher Nox emmissions which are countered by the other positive benefits
I am sure that if about 1% of the budget allowed to make catalytic converters as well as Dpf's was allocated to Nox's from biodiesel that issue will be licked in no time
I for one have no doubt that within a year or two that this will be the case any way, in the meantime we just have to do exactly what we are doing Keep each other informed as well as every one else that has an interest in renewable energy
Cheers
Chris

One thing has to be pointed out - the majority of passenger car applications of DPF will, or are using, post-injection techniques to clear the DPF when it's fully loaded.

This inevitably leads to fuel entering the engine's lubricant - and biodiesel breaks down the lubricant which in turn leads to rapid engine wear (this has been proven and is accepted by the scientific community). Which is why manufacturers are reluctant to give the all clear to biodiesel in DPF applications. A low percentage of biodiesel may be acceptable but definitely not B30 or higher.

It's fair to say that biodiesel may be compatible with some applications of DPF but not those in passenger cars at present or in the near future.

Originally Posted by F-B

One thing has to be pointed out - the majority of passenger car applications of DPF will, or are using, post-injection techniques to clear the DPF when it's fully loaded.

This inevitably leads to fuel entering the engine's lubricant - and biodiesel breaks down the lubricant which in turn leads to rapid engine wear (this has been proven and is accepted by the scientific community). Which is why manufacturers are reluctant to give the all clear to biodiesel in DPF applications. A low percentage of biodiesel may be acceptable but definitely not B30 or higher.

It's fair to say that biodiesel may be compatible with some applications of DPF but not those in passenger cars at present or in the near future.

Hi there
I am not so sure that this right I would have thought the break down of lubricity is the end result of low sulphur fuel that is used It has been a problem for larger capacity engines for a while now
I don't know that passenger car manufacturers have done any more than change the seal material in their injection systems
The link below will give anyone that is interested fairly well documented low sulphur diesel injection systems issues
If I am reading the latest reasearch right it seems that the scientific world out there suggest a 1-3% addition of Biodiesel so as to improve lubricity
In so far as DPF's are concerned it apperas that biodiesel improves them rather I have yet to see evidence to the contrary from a scientist's research
The point to keep in mind is that to get a catalyst designed tested and approved so as to be fitted to a vehicle in an assembly line at a fair price is a long and arduous process
Why would any one in the design criteria would want to include biodiesel in the specification when no more than at best 2-3 % of these cars will ever be used with biodiesel
Here is the link for any one that has an interest in finding out about low sulphur diesel This man done his homework and he is a proponent of biodiesel http://www.bebioenergy.com/agronomy_conference.htm
This is a long article so go down the page to the heading Low sulphur diesel, in particular the Stanadyne recomendation a fairly large us based manufacturer of diesel injection systems
Cheers
Chris

Hi again F-B
Would you be kind enough to send me a link or a reference to the item(s) you are refering to (that has been accepted by the scientifc ....)
It would be appreciated
Thanks
Cheers
Chris

F-B, a couple of points I'd like clarified that I am still confused about:

1. Post Injection. If a fuel (which I believe does not come from the main fuel tank, but is instead another fuel carried in an small reservoir specifically designed for this purpose) is injected into the DPF, I fail to see how this fuel, (be it biodiesel, petroleum distillate, or any other sort of fuel) would get back into the engine lubricant. The DPF is at the end of the exhaust system and treats the air that passes out of the engine. The engine and the DPF are clearly 2 very separate systems and there could be no way that the DPF fuel would enter back into the engine. This would be almost as silly as saying that the rear brake drum cylinder fluid might enter the engine and dilute the lubricant.

2. Does biodiesel actually pollute the engine lubricant? I have heard conflicting stories about this. I have heard of B100 users claiming far longer lubricant life as there is no sulphur and a much cleaner and more complete burn, thus resulting in no dilution of the lubricant (as petroleum distillate currently does). Of course this point is null and void as per the above point and gets a little off topic. However, I'd like to see this topic discussed with some more depth in a new thread. I'd not go so far as to say this was a "proven or accepted" belief held by any "scientific community". If I were to assert that, I'd be sure to back it up with some better arguments

Please be careful about making sweeping statements like mentioning a specific blend that would not be compatible without mentioning any facts or research to back this up. We already seem to get enough of this crap from vehicle manufacturers. Let's try to inform ourselves without just parroting myths. If I am guilty of doing this too, then could someone please correct me?

Biodiesel can improve lubricity of the fuel but I'm talking about the fuel getting into the engine oil/lubricant with DPF usage. When it does so it reacts with the oil and the products of the reaction/decomposition are very detrimental to the durability of the engine.

Fuel also passes into the engine oil to a certain extent during cold starts regardless of DPF being present or not.

The fact that biodiesel degrades engine lubricant is indisputable; a quick google search found this info that is in the public domain:


http://http://www.enviroharvest.ca/d..._biodiesel.htm
100% biodiesel and higher percentage biodiesel blends can cause a variety of engine performance problems, including filter plugging, injector choking, piston ring sticking and breaking, elastomer seal swelling and hardening/cracking, and severe engine lubricant degradation.

http://eriss.erin.gov.au/atmosphere/...pubs/mobil.pdf


Lubricant degradation. The use of B100 or high percentage biodiesel blends can
cause severe engine lubricant degradation. Diesel engine manufacturers
recommend more frequent oil change intervals if biodiesel is used.

http://www.eeci.net/archive/biobase/B10577.html
Test results: the effects of biodiesel on lubricant
The results of tests on the effects of the use of biodiesel on the lubricant can be summarized as follows (S. Bona et al, 1997):
- A definite reduction in viscosity was found in all samples, which means that biodiesel fuel dilutes lubricant oil;
- Sludge and lacquer-like coatings (index of thermal-oxidative degradation of the lubricant) did not increase excessively;
The alkaline number (TBN) was reduced. The TBN index expressed the ability of the lubricant to neutralise acid compounds generated by combustion and degradation of the oil. TBN in used oils (samples taken after 440 and 630 working hours) reached excessively low values;
- The acidity number increased (TAN), an index of formation of acid products due to oil degradation;
- Metals, particularly copper and lead, contained in the engine bearings, reached particularly high values in samples taken after 440 and 630 working hours.

(note these are all referencing usage without DPF; post-injections needed by the DPF will make things a lot worse)

DPF usage and post-injection:
Passenger car applications of DPF in general use active regeneration (as compared to passive as per the earlier report)

http://www.landre-ruhaak.nl/Whatarethey.html
Combustion of HC over a catalyst
The CRT® and CCRT® systems can form part of actively regenerated DPF systems in which the HC content of the exhaust stream is periodically enriched, either by in-cylinder post injection or by direct injection of fuel into the exhaust stream. The HC is burnt over the catalyst, raising the temperature of the DPF to combust the collected PM.

...most systems of this sort use the in-cylinder post injection as mentioned above to a greater or lesser degree. Basically the injectors are adding another injection of fuel after the main "power" injection. This results in unburnt fuel entering the cylinder, most of which passes through the exhaust and regenerates the DPF. Some of it however hits the cylinder bore and gets scraped down into the sump.

Once it mixes with the oil degredation starts....

Post injections can result in upwards of 5% of the sump oil being made up of diesel which is not an ideal situation. With biodiesel it's far from ideal!

(note I'm not disputing that biodiesel may be cleaner at the exhaust c.f. dead dinosaur fuel)

I can't post the entire report due to copyright restrictions, but I think this gives some indication of the fact that biodiesel behaves differently to diesel with current lubricant technology for a B100. I would expect the affects to diminish as the mix of bio/dino decreases. At what point this becomes acceptable is open to debate. I should say that I'm approaching this with the mindset of the manufacturers' in that the vehicle must have no decrease in its useful life by using biodiesel compared with mineral diesel.

Effect of various lubricating oils on piston deposits in biodiesel-fueled engines
SAE 2004 World Congress and Exhibition; Detroit, Michigan, USA; 03/08/2004-03/11/2004
Abstract:
Some customers of Transport Refrigeration Units (TRU’s) powered by 2.1-liter diesel engines in Europe are requesting to run 100% biodiesel fuel in their TRU’s. The purpose of this paper was to find a way for users of 100% biodiesel fuel to maintain reliable diesel engine operation through selection of a better engine lubricant. Diesel engines that have been run with 100% biodiesel fuel have been found to have deposits inside the engine that are not found when running on fossil petroleum diesel fuel. This paper examines the effect of various engine-lubricating oils on engines running with 100% biodiesel fuel. The comparison of various engine oils was accomplished by evaluating the piston skirt and ring groove deposits when running 4 different engine oils for 1000 hours each on identical engines that are fueled by Soybean Biodiesel fuel.



WHAT KIND OF ENGINE PROBLEMS HAVE THERE
BEEN WITH B100 BIODIESEL? - The literature has
explored various problems on B100 biodiesel fueled
engines, most of which are related to various residues
and deposits caused by B100 that can result in engine
damage.




HOW DOES B100 BIODIESEL FUEL GET PAST THE
RINGS INTO THE OIL PAN? - Under normal engine
operation, a small amount of any diesel fuel, including
petroleum diesel and biodiesel, will get into the oil pan
due to incompletely combusted fuel. There are several
reasons why the B100 biodiesel has a greater tendency
than petroleum diesel to get into the oil pan.
B100 has about 50% higher viscosity than petroleum
diesel [2], which means that when the injectors try to
atomize the thicker fuel, larger droplets will form in the
fuel spray [14]. The droplet size is affected by several
fuel properties including surface tension, specific gravity,
and viscosity.




CONCLUSIONS

All four of the B100 Biodiesel fueled engines had at least
one stuck top ring at the completion of the 1000 hour
test. As discussed in the introduction, the light loading of
the TRU application and the direct-injection combustion


could have contributed to excessive unburned fuel
getting past the rings and decomposing to form a
deposit in the ring grooves. The type of lube oil would
have a very limited effect in reducing deposits in the top
ring groove. The synthetic Oil D, and the semi-synthetic
Oil C, had better top ring groove condition for the
Biodiesel fueled engines than the mineral Oils A and B,
however even the synthetics were not able to protect the
engines from the formation of a stuck ring condition.

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One thing seems apparent with respect to wear and general information on the web - there is a misconception that because biodiesel exhibits less wear for the fuel injection equipment it must therefore give less wear for the engine as a whole which is a flawed argument.