Nitrogen is not the problem!

General Discussion
#1

It’s common knowledge that woodgas is less powerful than gasoline. There are several reasons for this; mainly, the gases have far less BTUs than gasoline does. One of the often stated reasons is that, since we’re using air, the woodgas contains nitrogen, a dead gas. Obviously gasoline has no nitrogen in it, so the woodgas must be less powerful because of all the extra inert gases.

Let’s look at some percentages. You might be surprised.

Atmospheric air:
78% Nitrogen, 21% Oxygen. [Ignoring trace gases.]

Woodgas as measured from Wayne’s gasifier:
20% Hydrogen, 20% CO, 10% CO2, 2% Methane. The remainder is 48% Nitrogen.

A gasoline engine runs on gas and air, mixed about 12:1 (it varies). 92% Air and 8% gasoline.

So the Air/Fuel mix on gasoline looks like this.

71% Nitrogen, 19% Oxygen, 8% gasoline.

Woodgas is pretty much 50/50. So the Air/Fuel mix on woodgas looks like this:

63% Nitrogen, 10% Oxygen, 10% Hydrogen, 10% CO, 5% CO2, 1% Methane.

So we have LESS nitrogen on woodgas. If we count the CO2 and Nitrogen together as inert gases, there’s basically the same as on gasoline.

Do you see something different though? How about oxygen? Only half as much! Should we experiment with adding some? [Please remember, oxygen is dangerous and expensive.] Supplementing 10% O2 at 2,000 RPM, a 318 would run through about 16 cubic feet per minute (largest bottle is 330cuft). Yow! Far from practical.

Now let’s think about Nitrogen for a minute. You might assume that removing nitrogen is always a good thing - after all, it takes up space and doesn’t contribute to combustion.

But you might be forgetting a basic fact about engines - they are air pumps. Heated nitrogen has a good expansion rate - without any in the cylinder, where would all the heat go? Much less work could be accomplished, because there wouldn’t be enough inert gases to absorb the heat and expand outwards. Without it, your engine would generate lots of excess heat, and accomplish less work overall.

I don’t have any proposed solutions for increasing the potency of woodgas. But it’s good to be aware of what’s happening, and not to blame everything on nitrogen.

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#2

Great post ChrisKY
I agree 96% with your numbers and conclusions. (the 1 to 4 % of in gasifer produced CH4 in Waynes woodgas is missing at 4%+ this maths out as contributing as much shaft power as the higher %age of CO fuel).
The passed through nitrogen in addition to being a great expansion gas is along with the CO2 a combustion burning rate modifier allowing the woodgas to fuel reasonable well a gasoline/propane/methane set up Internal Combustion piston engine.
Pure CO, or H2 dedicated fueled engines MUST be IC piston engine set up radically different from these or each other.

You are setting yourself up for the question then of why doesn’t woodgas then produce the same engine power as gasoline?
Well neither do substitue propane and methane fueled in a gasoline set up IC engine.

Regards
Steve Unruh

#3

Yes Steve, thanks for reminding me of the methane, edited to include. It is small but important.

It should be fairly clear to everyone why woodgas has less power. The fuel gases are not energy dense. Gasoline is very dense. So it’s no surprise to get more BTUs (more power) into a small space with a denser fuel.

I’ve added this as one of the Learning section articles. I will be expanding this section over time… as I get time.

#4

I agree with both off you, 99% :wink:

But still there is some importance in the right mixture,
The less Co2 generated by the gasifier, the more efficient he’s working
The higher Hydrogen content will increase the flame velocity, ergo better performance in the combustion engine
The methane will also have its benefits in increasing some power

It comes down dough to the mixture needed by the given engine to perform at its best.

Producer gas mixtures are rather less power full then gasoline mixtures, but then it comes to engine tuning to compensate that.

Maybe an idea to retrofit a lambda sensor , just to indicate if the engine runs lean or rich and the regulating capability from the mixture to adjust to the optimum would help a lot.

My question, towards both of you, what would you consider the most effective mixture/proportions ? about Carbon monoxide, Hydrogen and Methane talked only.

#5

My opinion on what i consider to be the most effective mixture = 44%Co + 44%H2 +2%CH4

Since there is no need to ad extra oxygen in an mixture without adding more fuel… the calculation is roughly as follows:

Mixture requires an amount of oxygen to be completely combusted.
Since i doubled the amount of combustable gasses, i also need to double the amount of oxygen…

leeds to following calculation:
42 Parts Combustible gas + 58 Parts inert against 21 Parts Oxygen + 79 parts inert = 200, where is 63 parts forming the energy and 137 Parts the inert

90 Parts Combustible + 10 Parts inert mixed with 45 parts Oxygen + 169 parts inert = 314, where 135 parts forming the energy and 179 Parts the inert.

in perspective: each part of mixture contains in case 1 = 0,315 Energy and in case 2 = 0,429 Energy, an increase of 36,19% !!!

That is food for thoughts

#6

interesting ideas, i would say forced induction is cheaper and more reliable/adjustable than oxygen or NOS tanks, even though we run into the turn down ratio… one other thing to think about even though alot of people give it a bad rap is water injection. and theres a limit, its rust and hydrolock haha anything that is cheap or easy to increase cylinder pressures on the down stroke (ignition advance for slow burning wg) would surely help.

#7

Hi, I am a brand new fellow on here, just bought the book last night. But I went for the full lifetime forum membership.

I’ve studied the general concepts of the gasifier and I believe that some oxygen enrichment could be beneficial. The trick is, to do so economically. We don’t need, or even want, the 99.95% pure oxygen which comes out of the tanks, or the medical oxygen generators. 90% oxygen would be fine, perhaps even too much, but air can be mixed in to bring it to the desired level. As far as heat removal, I am not sure that this is so much of an issue. But it’s worth keeping in mind. In any case, I have some ideas on how to build a cheap oxygen generator but need to refine them, and then actually build. It is important to me to keep the design simple to build, reliable, and inexpensive. For instance, the design could also remove argon, but as it is a fairly minor component of air, as opposed to nitrogen, that it might not be worth the effort. Argon is a noble gas, and therefore unreactive for all practical purposes. Nitrogen, however, is not, and can react creating useless compounds which can also be nasty pollutants (nitrogen oxides and ammonia, for instance). So perhaps, a better term for the machine I propose is a nitrogen separator.

#8

Hi Robert, and welcome to the forum. An oxygen-enriched air supply would be useful. What would be the flow rate, do you think it can keep up with an engine?

#9

years, but never tried it, to build a hydrogen battery, separate the oxy. and hydrogen, feed oxy. in air, hydro. in with the out going wood gas. Al

#10

Vacuum Pressure Swing Adsorption which would probably fill up the rest of one’s truck. It’s the method used for portable oxygen machines.

#11

Yes, PSA (vacuum or not). In the past, there has been the worry about CO2 and other minor air fractions poisoning the zeolite over time. Evidently some newer, specialized zeolites do not have this problem. As far as the size - well, they can be pretty small, as you mentioned Bill, they are used in portable oxygen machines. The question is, how much can oxygen can they provide? If it is hard or expensive to provide 100% nitrogen rejection, that should be at least some help, as every reduction in nitrogen should help increase power.

#12

Well, as I calculated in the original post, a 318 would run through about 16 CFM at merely 10% oxygen supplement (to bring us on par with gasoline.) Most medical units make 1/100th of that at the most.

Here’s a unit that would suffice. http://www.ozonesolutions.com/products/Oxygen-Concentrators/OG-1000_1000_SCFH_Oxygen_Concentrator

Unfortunately there’s no price (if you have to ask… ) and it weighs as much as my truck (4250 lbs). Also requires external air compressor to supply 175 CFM @ 90psi.

#13

Robert,
The deal is how much O2 that is required to make wood gas. Too much O2 and the quality of wood gas goes down. So the Nitrogen may be a good filler to match with the required engine CFM. If you remove the Nitrogen after the gasifier, Is it only going to remove the nitrogen? Is the wood gas going to have an adverse effect on the Zeolite or the PSA unit with it’s corrosive properties? Maybe a PSA would best suit for the incoming air at the engine to mix with the woodgas?
I have optimistically looked into this but have decided to make a working system first. Now I want my truck to run on wood. After that I want to build a charcoal gasifier. So while the potential for this to work is there, I have the woodgas bug.
Chris S, what baffles me in your initial post here is, where did the Nitrogen go after it passes through the gasifier?

#14

Hey BillS
Read back closely. What ChrisKY was putting up was finals out of IC engine exhaust flow by porportions. The duel streams of nitrogen’s in the gasifier primary air and engine secondary air hopefully just get passed through. ANY having been heat and pressure converted to NOx just ties up oxygen that could have been used to make more combustion heat/expansions gasses piston pushing mechanical energy.
Once you become HARD Goals orientated to total system energy inputs IN; versus usable systems energies OUT then molecular modeling take a far back seat to the realities of “systems” effects on systems metals in heats spalling, corrosion’s and crystallization. And Then cumulative systems by-product “contaminates” problems.
Bluntly. Until molecular idealists start getting hammered by real condensates and ashes: Until they learn to deal with these, and MORE; they can never achieve real world workable results.
Steve Unruh

#15

i have wondered about this for awhile…what about a reverse osmosis oxygen filter?..they work by blocking nitrogen,…if i remember right a double pass 6" filter would lift the oxy % to about 32 to 35% at 6m3 per minute.

If it was on the gasifier intake it would enrich the fuel gas mix…probably have to reduce the size of the gasifier air jets/nozzles a bit to compensate for higher oxy content.

richer gas would need a better fuel/air ratio = more power

first ran across reverse osmosis oxy filters on a gold plant i worked maintenance on…it never gave any trouble so i didn’t have much to do with it apart from change the intake (dust) filters once every 2 weeks and change the oil in the detroit diesel half engine half compressor every 500hrs