co/co2

jaybee

What is the difference btween the two and what role do they play in combustion.

Jim Davis

CO-CO2

CO2 = Carbon Dioxide, complete combustion
CO = Carbon Monoxide, incomplete combustion

When carbon in the fuel is burned in the combustion process with oxygen it forms carbon dioxide if all goes well. But if the fuel and air do not mix well or are not brought up to proper temperature carbon monoxide will be all that is created. Actually CO is the first stage of the combustion process. CO2 is a gas that is 40% heavier than air. If it is not removed from the heat exhanger or the room it can displace Oxygen which becomes a problem with unvented heaters and cracking a window doesn't help.

jim sokolovic

The illustration that helps me...

understand or explain the relationship between CO and CO2 is the graph that plots the two on each axis, with a parabola-shaped curve. This curve generally illustrates that in most cases, there is a range of CO2 that provides a low CO level, and going richer or (in many cases) leaner, the CO can rapidly rise. I would have liked to include this graph here, but do not have it. Do you know what I am referring to, Jim Davis or anyone else? Do you agree or use this in your training? If so, is there anyone who has this to show here? Thanks.

Alan R. Mercurio_3

Jim, Is the chart you're thinking of?

Your friend in the industry,
Alan R. Mercurio

Oil Tech Talk

Jim Davis

Combustion chart

This chart shows a correct relationship of CO2 & O2 on the Excess Air side of the graph, but not on the Fuel Rich side. As an appliance get richer the Oxygen actually increases on the Fuel Rich side also. The CO portion of the chart is totally misleading because CO can exist in excess levels anywhere on the excess air side and is not predictable.

Alan R. Mercurio_3

So, another words, I need to keep digging through my charts

Your friend in the industry,
Alan R. Mercurio

Oil Tech Talk

jim sokolovic

Thanks for the reply on this, Jim...

I'm assuming you do know the chart I had in mind. I agree that nothing is exactly predictable, given the variations in burner types and conditions that exist, but I thought the general concept was good for demonstration. I'd still like to see someone attach this to a post and we could discuss it, even if falicies are uncovered.

Jim Davis

Just color it yellow?

jim sokolovic

O.K., now I see Alan has already posted...

something very similar to what I was thinking about. I'm not following Jim Davis with the "oxygen increasing on the fuel rich side" statement, but definitely agree with the "CO can exist in the excess air side" statement. That is why I alluded to a parabola shape to the CO curve, to generally suggest that there are conditions where excess air can produce CO also. Can we attribute this to impingement of the flame on a surface, when it begins to lift or stretch, or are there other circumstances?

Jamie Hall

Another difference...

is that while CO2 can suffocate you, it takes a lot of it and a long time... CO, as we should all be very aware, can kill you at relatively low (unnoticeable) concentrations, does it quite subtly (particularly if the victims are asleep) and, if you should be so lucky as to recover, can take a long time (like months if ever) to fully recover from. Not Good Stuff.

Alan R. Mercurio_3

Jim, though impingement of the flame on a surface
can and will contribute to the production of CO it's also possible to start producing high levels of CO when your excess air is to high and you still will may not have any smoke. This is because at a certain point you begin to cool the flame.

I try to maintain between 25% to 35% excess air in a residential oilheating appliances.



Your friend in the industry,
Alan R. Mercurio

Oil Tech Talk

Jim Davis

CO on Excess Air Side

Impingement is definitely one of the reasons, but by designs of different types of equipment, there is good or clean impingement and there is improper and dirty impingement. The other major cause is operating a cooler flame temperature by having too much excess air. Many times in class during testing of equipment we get high O2 readings above 10% caused mostly by underfiring. As fuel is added every students watches the CO reading fall as the Oxygen reading goes down.
On the fuel rich combustiion curve, I am talking past the 0% Oxygen, not 1% or .5%, but way to the left. CO at this point is going to be in the tens of thousands ppm. Only been there 3 times and the CO levels were 70,000ppm to over 100,000 ppm. I do have testers that go to 80,000 and 100,000. They were actually designed to test propane lift trucks. Anyway the Oxygen reading was 8%. When the gas input was reduced, the Oxygen fell to 4%, CO still high. Turned back the gas some more and the Oxygen dropped to 0%. Next time the gas was reduced the Oxygen went up to 3% and the CO came down to 100ppm. Scary stuff and yes, the first time I saw this I didn't have a clue!!

jim sokolovic

Shazam! That's wild stuff...

Is this an occurrence that takes place on a particular type of equipment only? If the Oxygen is seen to be increasing as the fuel input was made richer, wouldn't the CO2 be seen to then decrease proportionally?

Jim Davis

That is exactly right! That is why the CO2 curve on the fuel rich side decreases the farther out you get even steeper-not burning the fuel and diluting with air. The three appliances that this occurred on 1. Process steam boiler in plant in Hamilton,Ohio 2. Steam boiler in school in Canton, Ohio 3. Bake oven in grocery store in Cincinnati,Ohio
If I were to make an assumption and they even make me look stupid, I would think only power burners or induced draft equipment could keep running at these kind of numbers. Believe it or not, there was minimal sooting on any of them.

Kal Row

this may shed some light - from something i already posted

CO happens when there is not enough O2 to go around, the causes of this "rich" mixture are many - some really vexing, at the fine level,

typically O2 left over correlates to CO2, the lower the O2, the higher the CO2, until you get down to zero left over O2, where you are forming CO, because the is not enough air to go around, so just a little over 1% left over, at the sensor, should guarantee, that there was enough O2 to go around all over the combustion chamber,

but, THE BIG BUT, things are not that simple – a problem I call micro-mixture, you’d think that if you have too much air, there would be 100 guarantee of no CO, not true, because when you get into the lean miss conditions (ie the HydroCarbon and O2’s and Heat, are so spread out that they don’t connect – indicated again by rapid rising HC or O2 – (co rise will be much slower)) – you will also get CO, since 1 HC’s (it’s really H2C+junk) might just happen to connect with just one O2, and not the 2 O2’s required to get 2-H2O’s and CO2 – so you get instead h20 and CO, OR, if you are lucky, 2 h2c’s connect with 1 o2, to give you 2-h2o’s and 2 carbons – lucky because, the soot, at least, you can see – so it wont kill ya!! I really should have said Up to 2%, because, probably after 1.5% left over O2, it’s already to lean – and I suspect that number varies with fuel/air temp/press flow speed and Heat-eX temp

Then there is the localized speed and mixture temps that affect the whole heat+fuel+air connecting thing – a clump of cold fuel molecules could suddenly pop apart and demand air that’s just not there, OR, separated fuel molecules hit a cold heat exchanger and clump together (or should I say condense , then on the outside of the clump burns rich, because there’s not enough O2, while the inside of the clump, stays unburned completely, – then, there is the actual air flow, the secret has always been to slow it down as much as possible – so with some excess air, most of the fuel/air/heat connects, that’s why those gas/ceramic/radiant heaters do so well – or the ‘sticker shock city’ vitodens from viessmann

Here, is were, the science gets weak.....

eleft_4

please resize the graphic in this topic

jim sokolovic

So the occurrence of CO2 getting lower...

on the fuel rich side is not the norm, but is possible? I have run many types of burners quite rich, and seen the CO fly up beyond what the analyzer range can display, but do not recall seeing the CO2 get driven lower as I richen the mixture (it usually approaches the "ultimate" value). Once again, I think your point is that nothing is totally predictable - which I agree, but the chart is useful for understanding the normal occurrences (without nit-picking on exact numbers or curve slopes)?

Jim Davis

As you approach 0% Oxygen your CO will go off scale and CO2 rises to ultimate. But when you pass this point CO2 drops quickly and CO go in the tens of thousands. This is the point most manufacturers of CO analyzers say you will fry your sensor unless you have a high range tester. Let's just say your lucky never to have encountered this condition.

Unknown

A fuel rich mixture

can make CO and the charts wqill not show it. In my GAS combustion classes we discuss this and also how to make sure you do not get tricked or as my old Combustion mentor Professor Tom C. Roche used to say get "mouse trapped".

I have experienced this on several occasions when gas power burners where overfired and the boiler design was not capable of handling the mix. It is interesting that when this happens the flame remained blue.

We used to talk about the unseen line on the combustion curve chart which was hidden CO (only detected if you test for it). It encopasses making sure the entire set up and adjustment of equipment is done and tested.

Kal Row

i still dont get why you guys dont messure

HydroCarbons in the flue - that forth gas will tell you a lot, if heat-fuel-and-air are connecting or not - and many analyzers have an hc socket

I am telling ya, it’s just a matter of time before the epa gets involved, then you’ll have baro sensors, o2 sensors, temp sensors all going to a computer that will modulate the fuel and the air – and a single stage catalytic converter is not out of the question – at least we will be able to extract the heat from the catalytic converter’s jacket

Without the emission controls, a modulating boiler is even worse, floyed and Lead-Pipe are each going at their WM Ultras with their analyzers, and the readings are all over the place, and I don’t care for any of them, o2 as high as 9% - so for now, running a bunch of small cast iron fixed combustion boilers at 140-160 staged with a tekmar and injection mixed to the load is still easier on the atmosphere than these new fangled modulators with just not enough sensors to do it right – the combustion efficiency of a staged/mixed cast setup, may even offset, the condensing efficiency, of the full modulators

No manufacture wants to bite the active combustion control bullet, – the gov is going to have to push them – lucky that the basic sensor set, is avail real cheap from the auto aftermarket – a heated o2=$35, barro=$20, temp=$10, the computer should be $150 in quantity, and the modulating gas valve twice as much as a regular one, and the combustion fan will have to be a var-speed and oversized with a bypass valve to keep the flue temps nice for pvc pipes – it’s going to happen, why not pre-empt it – and we better not let the Germans do it first – the viessmann vitodens is embarrassing enough, thank god it costs a mint

Weezbo

nicely done.

may i ask what affect cold coagulation and seperation of fuel oil molecules ,prior to atomization play in the apparent drastic increases in co?

scrook_2

co2 vs co

CO2 suffocates/asphyxiates you by displacing/replacing the O2 in the air you breate -- N2 or other gasses can do the same thing, but in either case it takes quite a lot. As long as your lungs can remove enough CO2 from your blood though you don't notice, it is increasing CO2 in the blood that tells the brain you need to breate harder/faster/deeper, not decreased O2.

CO on the other hand is *absorbed* by the red blood cells hundreds of times more easily than O2, so they do not absorb nearly the normal amount of O2, but absorb the CO instead, even though it remains present in near normal quantities in the air, meanwhile CO2 is exhausted normally from the blood by your lungs so your brain doesn't have a clue that anything's wrong.

So you get less and less oxygen to your body, headache starts you feel weak/lousy, w/ lack of oxygen the brain does not think clearly or rationally. Eventually you may pass out and ultimatly you can die if the CO concentration is high enough, and high enough isn't very high. If you are asleep, there is nothing to warn you/wake you...

Kal Row

cause it like putting a drop of cold water

on a hot griddle - the fuel flashes instantly - but at physical point there just isn't enough air to go around for proper combustion - so you get CO – you always get H2O because hydrogen and oxygen connect a lot better that oxygen and carbon, in fact, the only thing that connects better with oxygen, is chlorine - that's why those old halon fire extinguishers worked so well, the chlorine in the halon (tri-cloro,di-floro ethane) grabs all the air away from the fire instantly – and that’s that. Of course the “tri-cloro” makes it a triple ozone killer so they charge you $30 a pound to dissuade you from using it – I foresaw the epa approaching like a freight train and stocked up – I have halon extinguishers all over my house – best of all it doesn’t make a mess – you can put out a burning frying pan with it and still eat what’s inside

jerry scharf

CO2 is a bit trickier than N2

Carbon Dioxide suffocation is a bit more complex than other gases. The way the lungs decide when to breath is based on the CO2 levels. If there starts to be CO2 in the inhaled air, the breathing system is knocked off and you can have problems at lower precentages than with other gases.

CO is in a class by itself. Jim, you say you saw 8-10% CO in combustion samples. That's mind boggling.

thanks,
jerry

Ken D.

CO/CO2

On a practical note, on an otherwise healthy burner, CO is usually caused by recirculation of combustion gasses. This most times is the result of flue or vent fouling or blockages or possibly the flue pipe disconnected or leaking. The gasses do not vent up the chimney and therefore get dumped into the room where the furnace is. The spent gasses are sucked up into the combustion air intake where they are reburned. The more they are recirculated (reburned), the more CO is produced and the more concentrated it becomes. Until the furnace carbonizes (soots) you would not know it - unless a CO detector is installed - until sickness or death. This recirculation can be charted on the Stoichiometric chart that was provided by Al. As mentioned, you can have good CO2 numbers otherwise, but still be producing CO.This is why I take both CO and O2 readings in addition to CO2 when I check combustion. To check if you are on the right side of the Stoichiometric curve, simply close down the air for combustion. The CO2 should go up or conversely if the air is opened, the CO2 should go down. If not you are on the wrong side of the curve. This is a problem that is more likely seen with gas or wood, but it can happen with oil. It does not necessarily result in sooting right away. I have seen where this was a problem in a clean operating burner. It was years ago in a Blueray furnace. The flues were clean and draft and CO2 were ok. There was a problem with the internal refractory ring causing more internal recirculation than the furnace was designed. This was a mind blower when I first encountered it. Back then we checked oil combustion with a Bacharach combustion test kit with a CO2 tester and all readings were good, but the furnace would dance while running. It wasn't until we checked it with a O2 tester did we see the problem. That is why each job I have is checked with a Bacharach electronic combustion tester. I get all readings- CO,CO2,O2,excess air, NOX,Etc. Plus I can print out the readings for a record on paper you can file. I also tell all my customers that burn any kind of fossil fuel to get a CO detector and use it. CO is actually a form of oxygen, that is why the body absorbs it so readily. It also is absorbed faster than it is expelled,so it has a cumulative effect. Pretty interesting and dangerous subject. I am amazed by the intellegence and detail by the previous posts. There are a lot of sharp people in this industry, and that's a very good thing. Ken D.

Kal Row

even cooler

i just bought a new GE Profile slide in range with lots of cool features and the whole manual was littered with instructions of what not to do so you don’t generate CO, for example, they say it in words and pictures, that if you use a WOK with the ring that comes with it, then you will generate deadly carbon monoxide – this only one example of many, in the manual, they finally get it!!!

Unknown

Kal, could you possibly

make me a copy of that instruction and mail it to me?

Tim McElwain

Gas Appliance Service Training and Consulting

22 Griffith Drive

Riverside, RI 02915

Kal Row

i attached the pdf from the ge site on model JGS968BHBB

if you do a control/f in acrobat and search for "carbon" you will get 5 hits, 2 on pg 3, 1 on pg 6, 2 on pg 9

this range is way cool, and well thought out - for example - the largest burner, made for huge pots, is in the front - since you wouldn’t want lean over to the back with a huge pot - but - the 4 slots in that burner cap, 2 in each front corner, where the grates are open, are made smaller to cut the flame size in the front corners of the burner so you don’t burn yourself - since the grates are cut out over there, and you could easily get your hand or sleeve in there, - it has to have the large cut outs, since you don’t want to sink the btu’s to the grates instead of the pot

read that manual or go to http://products.geappliances.com/ProdContent/Dispatcher?REQUEST=GEAPRODUCTRESULTS&CATEGORY=Slide-In Gas Range&PRODLINE=Gas Cooking&MASK=Approved Models_SalesNet_CustomerNet_Consumer Ready_Full GE Collection_GEAppliances.com


ps I live in the nyc metro area and paid 25% less than list

Kal Row

another anti CO freature with this range

the burner caps support the lager grates in the center, which allowed them to raise the height of the grates a full inch above, this distance guarantees airflow even with a huge pot - some GE engineer must have take a co tester to a regular stove, and got shocked by the readings, like i said, they finally got it