Talk:Combustion/Archive 2

Archive 1

Archive 2

nitrogen hydrocarbon combustion?

Is the stöchiometric combustion for hydrocarbons containing nitrogen known? For example for Pyridin. Is NO2 or NO or N2 the stöchiometric product? — Preceding unsigned comment added by 129.70.70.122 (talk) 11:33, 6 October 2011 (UTC)

Respiration

I don't think respiration should be included in this page. I thought the definition of "combustion" was rapid oxidation, so by definition there can't be "slow combustion". --Keenanpepper 01:28, 14 Oct 2004 (UTC)

Speed has nothing to do with whether combustion occurs or not, it has to do with what the reactants are. As long as you have a hydrocarbon reacting with oxygen which is creating carbon dioxide, and sometimes carbon monoxide and/or water as well, you have combustion. Respiration is O₂ reacting with the various forms of carbon in an organism, and it creates CO₂ as a result. Therefore, by definition, it is combustion. --BMS 03:47, 16 Dec 2004 (UTC)

The definition of combustion does not include a reference to speed. Within the frame work of combustion - there is no such thing as 'slow' combustion -or 'rapid' combustion. There are rates of combustion which are relative. —Preceding unsigned comment added by 64.30.82.123 (talk) 02:26, 4 October 2009 (UTC)

But the definition states combustion is accompanied by the production of heat or both heat and light in the form of either a glow or flames.I do not believe this happens in respiration (except fot the inevitable increase in entropy). Is the definition not accurate then? Manuel N —Preceding unsigned comment added by 84.120.147.37 (talk • contribs) 7 December 2006 (UTC)

Spontaneous Combustion

The spontaneous combustion page disambiguates to this page and this page has a link to spontaneous combustion but neither actually describes what it is or how it works. Which should contain information or should a third page be created?

I think that someone should add to this page, under "types" of combustion. Bernard S. Jansen 04:14, 15 January 2007 (UTC)

I think that any section of Spontaneous Combustion should be separated from the established Combustion pages, and every section in there should be well sourced. IOW I think Spontaneous Combustion is right up there with Vampires and Werewolves, and deserves no place here. —Preceding unsigned comment added by Halligan00 (talk • contribs) 14:24, 6 February 2009 (UTC)

Example

in the example in the intro carbon is made a link in the reaction. Why? It is no more relevant than the other elements. Ozone 00:34, 1 January 2006 (UTC)

Formation of formaldehyde

Formaldehyde says that it can be formed by incomplete combustion. What kind of reaction would result in formaldehyde? Just taking a wild stab in the dark with methane:

$CH_{4}+O_{2}\to H_{2}CO+H_{2}O+heat$

I have no idea if that's a valid reaction but the elements at least are equal on both sides... Cburnett 05:02, 11 April 2006 (UTC)

The primary source of Formaldehyde in a steady flame is the reaction between the methyl and oxygen radical shown below.

$CH_{3}+O\to CH_{2}O+H$

There are other reactions that'll make Formaldehyde but their rate of reaction are orders of magnitude lower. The most important of these are two reactions that are dominant during the ignition process because the concentration of the oxygen radical hasn't built up yet.

$CH_{3}O+M\to CH_{2}O+H+M$

$CH_{3}O+O_{2}\to CH_{2}O+HO_{2}$

boy that is complicated--Kkidd (talk) 14:55, 18 May 2008 (UTC)

For the sake of completeness there is one more worth mentioning but it is the slowest of the four.

$CH+H_{2}O\to CH_{2}O+H$

BlatantHeroics 00:05, 24 June 2007 (UTC)

Combustion Analysis ?

In the short section called "Combustion Analysis", it is defined as the determination of the compounds created by combustion. Though, I added a link to a page called "Combustion Analysis" regarding -mainly- the application of exhaust fume analysis to the determination of combustion efficiency. We have here two different fields related to the same term: theory of chemistry and empirical thermal engineering. Does anyone can help to get an agreement on the definitions ? Kekel 20:04, 20 April 2006 (UTC)

Kekel, I really don't see any major difference. Combustion analysis (what you call "theory of chemistry") involves combusting an organic compound, analyzing the products of combustion and then using that information to determine the formula of the organic compond. The combustion link you added also analyzes the products of combustion and then uses that information to determine the quality of the combustion.

Both procedures involve combustion and analyzing the products of combustion. Both use that information to find additional useful information. I really don't see that as a conflict between "theory of chemistry" and "empirical thermal engineering". Nor do I understand why you labeled the boiler usage as "empirical". It is no more or no less empirical than the other usage. -mbeychok 18:23, 21 April 2006 (UTC)

Still, one approach is qualitative (the "chemistry" one) and the other is more quantitative (the "engineering one"). It makes a difference in my mind. But no big deal probably. The real thing is it would be nice if this section, "combustion analysis", could be developed in one way or another. Actually, I don't have the basics for this. I only entered the field cause I was looking for some info for my work that I finally found through this link.

Kekel 21:46, 23 April 2006 (UTC)

not really interested in the debate between chemistry related analysis vs. engineering related analysis- but I included a small section about combustion analysis at the end of the incomplete combustion section- where it applies practically?johntindale (talk) 15:55, 14 May 2008 (UTC)

Reverting of Pvsheridan's comment about fossil fuels

Pvsheridan had entered a paragraph in the Combustion Analysis stating that the term "fossil fuel" was a misnomer and that Wikipedia should completely remove that misnomer from all its articles. His reasoning was that "recent finds" made it obvious that the more correct term was "hydrocarbon fuels" ... presumably because hydrocarbon fuels did not originate from fossilized animals. He failed to furnish any source references or proof of his contention.

Since the term "fossil fuel" exists in a very great many Wikipedia articles and probably hundreds of thousands of books, magazines, journals, encyclopedias and web sites, that is a pretty drastic step that Pvsheridan is asking for. It really doesn't belong in any section of this article. I suggest that he/she make his proposal at the Wikipedia Village Pump. For that reason, I removed his paragraph from this article by reverting to the previous version. - mbeychok 22:16, 23 April 2006 (UTC)

No mention of radicals?

Why are free radicals not mentioned anywhere in this article? Aren't they necessary for the survival of a flame?--Joel 19:46, 6 June 2006 (UTC)

Yes, it should definitely be mentioned that the mechanism of a combustion reaction (at least when oxygen is a reactant) is via radicals. There is an good section on combustion in the radical article that should be integrated into this page. --Tospik 23:37, 24 July 2007 (UTC)

Hydrocarbons

Should this be expanded to cover combustion of eg alcohols, alkenes, etc. Joseph Sanderson 17:16, 8 October 2006 (UTC)

addition

would it be possible for somebody to add information about elemental impurities during combustion affecting what the products are? Although a few elements, such as sulfur and iron, were mentioned, I think that should be expanded to include a more general discussion of the combustion of other elements, like maybe silicon, or phosphorus, or boron. 65.78.17.194 20:22, 13 October 2006 (UTC)

Could we add information about DUST COMBUSTION to this entry??? —Preceding unsigned comment added by 68.58.152.238 (talk) 21:15, 28 November 2008 (UTC)

double replacement vs. single replacement.... and plasma

Could someone please explain the difference between 'double replacement' and 'single replacement' in the following sentence? They aren't linked to another document to explain them: Combustion is double replacement, on the other hand a chemical reaction is single replacement.

Also, it would be great if someone would go into more detail about how and when fire/combustion is like a plasma (either on the combustion page, or the fire page).

Thanks!

Isabelle Hakala 04:11, 19 April 2007 (UTC)

Heat of Combustion of Sulfur

What is the heat of combustion of sulfur? Here it is listed at 9261 kJ/kg which is equal to 3982btu/#, but on the "Heat of Combustion" entry it is listed at 4.639MJ/kg, which is 1995 btu/#.... —Preceding unsigned comment added by 74.0.223.151 (talk) 13:33, 11 September 2007 (UTC)

The value given in this article is for solid sulfur and is correct. The value in the Heat of combustion article is incorrect and I have corrected it. - mbeychok 20:17, 11 September 2007 (UTC)

Combustion

Combustion is made when a complex sequence of axothermic chemical reactions betwwen a fuel and an oxidant ccompanied by the production of heat or both heat and ligh in the form of either a glow or flame. In other words its a specific reaction that happends wen there a chemical bond. When these 2 chimicals bond and form a combustion it usually oxidises. —Preceding unsigned comment added by 72.187.134.27 (talk) 03:28, 31 October 2007 (UTC)

Not all exothermic reactions should be considered combustion. For example, when carbon and hydrogen react to form methane, heat is evolved, but I don't think anybody regards this as "combustion". And when oxygen is added to methane to form methanol, calling this combustion pushes the term to a point where it's meaning becomes too diffuse to be useful.Thermbal 05:34, 9 November 2007 (UTC)

Indeed, and rusting is another one. Can we tighten up the definition to exclude these cases? 88.96.214.6 (talk) —Preceding undated comment added 17:49, 21 December 2009 (UTC).

Please see my comments under the header "Definition" I'll appreciate your comments. —Preceding unsigned comment added by 67.253.165.162 (talk) 19:01, 1 December 2010 (UTC)MK67.253.165.162 (talk) 16:45, 1 December 2010 (UTC)

What Chemicals was released?

During the burning of slate dumps there where chemicals relased from these burning slate dumps, Does anyone know what the chemicals was in English terms and was it toxic? —Preceding unsigned comment added by 75.108.161.89 (talk) 15:13, 15 February 2008 (UTC)

What causes heat to burn things?

Since this is an article that is primarily scientific in nature, I thought someone here might be able to answer it. What is it that causes fire and heat to burn other things. And I mean this on a molecular level. I really have no clue myself, yet it's the only question I've ever had about anything that I couldn't find on the internet. Does it have something to do with the speed that molecules of fire/heat are moving and when this hits say the molecules of something like wood or flesh it separates them or something? Another example would be lasers. Some lasers are fine to hit other objects, they have no visible effect. However a more intense/powerful laser will burn through very hard substances. What is the intense laser actually doing to the substance at a molecular level that the weaker laser isn't. Livingston 00:02, 18 September 2008 (UTC)

You'll probably get more answers if you post this question at Wikipedia:Reference desk/Science. That page is watched by more people, many of whom are eager to answer interesting questions such as this one. --Itub (talk) 18:05, 18 September 2008 (UTC)

I did try to answer the question in the reaction mechanism section. Obviously any unclear parts could be clarified, as it isn't always obvious to the writer what parts are too difficult to dereference (or too obscure or wordy). --Vuo (talk) 20:35, 18 September 2008 (UTC)

A reference in the at the end of title of the reaction mechanism section, linking to the "radicals" article could be helpful.67.253.165.162 (talk) 18:59, 1 December 2010 (UTC)MK

The lead

it is bad, rm all equations to start with? --Vuo (talk) 18:29, 13 January 2009 (UTC)

Vuo, with all due respect, I completely disagree with you. There is no good reason why all of the equations (or any of them) should be removed from the lead section. Nor do I believe that the the lead is "bad". regards, mbeychok (talk) 02:31, 14 January 2009 (UTC)

Possible typo

In the section titled "Reaction mechanism", hydroperoxl is mentioned and is given the formula "OH₂". Isn't hydroperoxyl actually HO₂ ? At least this is what the wiki article on hydroperoxyl says. (Also, wouldn't OH₂ be the same as H₂O?).

TinyTimZamboni (talk) 01:52, 11 June 2009 (UTC)

• I read "OH₂" as water! Agreed. Bridgettttttte (talk) 11:13, 22 May 2010 (UTC)

combustion

what are the advantages and disadvantages of combustion? —Preceding unsigned comment added by 121.7.77.25 (talk) 14:56, 19 July 2009 (UTC)

Definition

Several comments above have gotten at the issue, but without a clear answer. What definition of combustion is being used here? Is it "any oxidation-reduction reaction that is exothermic"? That seems rather broad. 68.239.116.212 (talk) 03:04, 7 December 2009 (UTC)

I agree with the original posting of the question (i.e. "what definition is being used here?") that any oxidation acompanied by release of heat is a rather broad definition. Expert books on combustion I browsed through do not define conbustion clearly, and quickly move on to topics of practical interest, which always involves organic fuels decomposing into other organic substances, many also fuels, which are gaseous under the conditions surrounding the reaction site. It seems to me that a practical definition should include the idea of the the presence of gas products that can transmit significant heat by convection. The intense light of a flash, for example, would be excluded as a "combustion" in that case. 67.253.165.162 (talk) 19:00, 1 December 2010 (UTC)MK67.253.165.162 (talk) 18:42, 1 December 2010 (UTC) —Preceding unsigned comment added by 67.253.165.162 (talk) 16:41, 1 December 2010 (UTC)

Elements supporting combustion

If my understanding that there are only a few substances that support combustion is correct, would it be worth naming them explicitly ?

Currently Oxygen & Flourine are mentioned.

According to <a href="http://sg.answers.yahoo.com/question/index?qid=20081228055613AA3jAcl">this forum post</a>, two more are mentioned. The author also makes the distinction that although Nitrous oxide (and a few other substances containing oxygen) are often said to support combustion, they are in fact oxidants. —Preceding unsigned comment added by ThermalCat (talk • contribs) 12:12, 8 January 2010 (UTC)

Combustion

It is the sequence of exothermic reactions between a fuel and an oxident accompanied by the production of heat and conversion of chemical species.The release of heat can result in the production of light in the form of either glowing or a flame.Most fuels of interest are organic compounds ( especially hydrocarbon) in the gas, liquid or solid phase. —Preceding unsigned comment added by 217.42.215.160 (talk) 16:23, 2 February 2010 (UTC)

I agree with the original posting of the question (i.e. "what definition is being used here?") that any oxidation acompanied by release of heat is a rather broad definition. Expert books on combustion I browsed through do not define conbustion clearly, and quickly move on to topics of practical interest, which always involves organic fuels decomposing into other organic substances, many also fuels, which are gaseous under the conditions surrounding the reaction site. It seems to me that a practical definition should include the idea of the the presence of gas products that can transmit significant heat by convection. The intense light of a flash, for example, would be excluded as a "combustion" in that case.67.253.165.162 (talk) 19:01, 1 December 2010 (UTC)MK

I would think the production of light or a flame would be a requirement for a reaction to be considered combustion. It seems to me that if light or a flame is not a requirement for a combustion reaction, the definition might as well be an exothermic oxidation reaction.24.14.162.203 (talk) 00:17, 5 June 2011 (UTC)

Reaction Mechanism Section starts off too advanced

Concepts involving singlet and triplet states are at the level of third-year college chemistry, typically a physical chemistry class or a class in molecular orbital theory for chemistry majors. A far simpler explanation is to describe diatomic oxygen as a molecule bonding two electronegative atoms, wheareas in combustion products the oxygen atoms are bonded to more electropositve elements such as hydrogen and carbon. Bridgettttttte (talk) 11:09, 22 May 2010 (UTC)

Thioformaldehyde Combustion

I think the beginning paragraph should make mention of the reactants (fuel) (i.e. For example: should be For example the combustion reactions of methane and of thioformaldehyde) —Preceding unsigned comment added by MarsInSVG (talk • contribs) 18:28, 24 August 2010 (UTC)

Solid Fuels

The text under the Solid Fuels heading sounds like an apt description of how cellulose (e.g., wood, paper, cardboard) burns, but it is not fully applicable to other solid substances (e.g., hexamine) burn. Hexamine, for example, does not burn in a "charcoal phase," and charcoal–a solid fuel in its own right–does not burn in a "distillation phase." 71.199.121.113 (talk) 19:16, 3 September 2010 (UTC)

Ignition

I am surprised that there is not a topic (or indeed separate article) on ignition, and ignition temperature. Such an addition would be appreciated. ColinBJ (talk) 14:26, 9 February 2011 (UTC)

There is an article on Ignition system but not a separate article on ignition or ignition temperature. Wikipedia is still a work in progress. There are many worthy articles waiting to be written. Are you able to write such an article? Even it is just the beginning of an article - they are called stubs. Here is a link to some good information that will assist you in beginning an article on these subjects:

• How to write a great article
  

Happy editing! Dolphin (t) 21:31, 9 February 2011 (UTC)

I have found there is an article on 'autoignition temperature' which has most of what I'm thinking of. What's needed is a cross-reference to it in the combustion section, and also to redirect searches for 'ignition' to it. ColinBJ (talk) 06:19, 20 February 2011 (UTC)

Done. Searching for Ignition temperature now re-directs to the article Autoignition temperature. Check it out by selecting the following: Ignition temperature. Dolphin (t) 06:29, 20 February 2011 (UTC)

Thioformaldehyde?

Since 20 July 2005, this article has had the equation for the oxidation of thioformaldehyde, CH₂S, by fluorine, F
₂: CH₂S + 6 F
₂ → CF
₄ + 2 HF + SF
₆. Is this reaction, which was in the article before the equation for the combustion of methane, relevant to an encyclopedia article of on combustion?

Thioformaldehyde, is apparently an unstable compound. It is stable as its heterocyclic trimer, 1,3,5-Trithiane. If CH₂S is unstable, does it last long enough for a meaningful "combustion" reaction to occur? Is there an application for this reaction with fluorine that could be deemed "combustion."

Interestingly, an internet search on "CH2S + 6 F2 → CF4 + 2 HF + SF6" gives many, many links.[1],[2],[3], [4],[5]

I don't know if the information started here, but it seems to spread quickly. Here is your chance to defend the equation in this article.KudzuVine (talk) 23:25, 14 September 2011 (UTC)

• No discussion in three months. I will take it out.KudzuVine (talk) 15:33, 23 December 2011 (UTC)

Just trying to help, think I found a type in fuel does not burn rapidly and just glows and later only

The text said: fuel does burn rapidly and just glows and later only

I tried to change it to fuel does not burn rapidly and just glows and later only--notice the inclusion of "not"

That was because I thought that is what the author meant.

I don't really understand how to contribute, or discuss, and am assuming somebody will delete this section I just created after deciding of the "not" should be included. — Preceding unsigned comment added by 173.57.19.120 (talk) 12:59, 19 November 2011 (UTC)

Combustion of Elements

The article has a sentence:
When elements are burned, the products are primarily the most common oxides. Carbon will yield carbon dioxide, nitrogen will yield nitrogen dioxide, sulfur will yield sulfur dioxide, and iron will yield iron(III) oxide.
The products are more diverse than those stated. For example, combustion of carbon often yields both CO and CO2, combustion of sulfur yields both SO2 and SO3, nitrogen doesn't combust in any meaningful way (but if it did, there are several possible nitrogen oxide products), and iron can form three different oxides, FeO, Fe3O4, and Fe2O3. The quantity of any product depends on the temperature and the molar ratio of element to oxygen. I don't think the as-written sentence contributes any useful information, and should be deleted or drastically revised. Thermbal (talk) 05:14, 20 June 2012 (UTC)

Reactions for incomplete combustion of hydrocarbons

The several equations under this heading are incorrect. Whenever a hydrocarbon is burned with a slight insufficiency of oxygen, both CO and H2 will be present as products owing to the existence of the Water gas shift reaction. As the fuel/oxygen ratio decreases further, some CH4 will appear.Thermbal (talk) 22:12, 23 June 2012 (UTC)

Nitrogen

In the last reaction with nitrogen? isnt the nitrogen already balanced? then why is it part of the equation? the equation starts with some other elements +N(2) and after the chemical reaction, some other elements + the same N(2)is produced. This doesnt make any sense.

It is there to show that during combustion in air, the oxygen reacts, but the nitrogen does not. It is present in the reaction mixture, and present unchanged in the product mixture. I agree that this intention may not be readily apparent, so if there is a way that anyone can help clarify the text for the average reader, that would be helpful. -- Ed (Edgar181) 14:46, 1 March 2012 (UTC)

It should also be notes that the "air" in the left-hand side of the equation is composed of oxygen and nitrogen. All of the oxygen is consumed in the reaction, but none of the nitrogen is consumed since it is non-combustible. mbeychok (talk) 16:00, 1 March 2012 (UTC)

"Ideal" hydrocarbon combustion would involve the reaction of the fuel with pure oxygen, with the only products being carbon dioxide and water vapor. In most practical applications, however, the source of oxygen is from atmospheric air, which consists mainly of nitrogen and oxygen. Furthermore, most practical combustion processes occur with excess oxygen (and therefore excess air) to ensure that all of the fuel is burned (including CO) and to minimize emissions. The excess oxygen and all of the nitrogen in the products absorbs some of the heat of reaction, which makes it more difficult to extract useful heat from these products.

Also, because of the high flame temperatures, various pollutant species will be formed (e.g. NOx) and will exist in the exhaust products. Even though the concentration of these pollutants is only in the ppm level (compared to 70+% nitrogen), the amount can be very significant to air quality and emissions limits. Keeping the nitrogen on both sides of the combustion equation serves as a reminder of these "minor effects". simchuck 18:15, 3 October 2012 (UTC)

Common Question Not Answered

I have been looking all over for a simple explanation of where the heat comes from in combustion, from the molecule being oxidized or the oxidant? I assume that the original energy that creates the heat previously resides somewhere in the atomic bonding, but I have not found where this is spelled out. What causes the surrounding molecules to vibrate? Bdubay (talk) 04:15, 24 July 2012 (UTC)

The heat released during the combustion reaction comes from the breaking and reforming of chemical bonds. Each molecule has a certain amount of chemical energy stored in its bonds, with the reactants' bonds containing more energy than those of the products. There is a net release of energy from the combustion reaction, which manifests itself as heat and visible flame.

Both the fuel and oxygen molecules are relatively stable on their own, and even when mixed together in the correct proportions, an additional amount of "activation energy" is generally required to break the bonds of the reactants and get the combustion started. This activation energy is usually provided by a spark (as in a gas range) or flame (the match used to light a charcoal fire). After this initial activation, the heat released from combustion provides the activation energy for subsequent reactions, until all of the fuel and/or oxygen is consumed. — Preceding unsigned comment added by Simchuck (talk • contribs) 3 October 2012

You seem to be searching for how to sign your posts. As stated near the top of this page, you simply type 4 tildes (like this:~~~~) and your signature will be automatically displayed. mbeychok (talk) 20:42, 3 October 2012 (UTC)

Atmospheric Nitrogen

When air is used for the oxidant, it is commonly assumed that this air contains 79% nitrogen and 21% oxygen (by volume). In fact, atmospheric air contains a number of other species, including argon (0.9% at 39.95 kg/kmol), carbon dioxide (0.038% at 44.01 kg/kmol), and water vapour, along with about a dozen other trace species contributing less than 0.5% of the total.

In the combustion equations, oxygen is assigned its true molecular weight (31.999 kg/kmol), and the "atmospheric air" is assumed to have a molecular weight of 29 kg/kmol (which is slightly higher than what you would calculate from the assumed species concentrations). This implies an "effective" molecular weight of the "atmospheric nitrogen" of 28.203 kg/kmol, compared to the value for molecular nitrogen of 28.013 kg/kmol.

I know it is not a big difference, and the distinction is probably irrelevant if you use a detailed chemical kinetics analysis appropriate to the level of precision required. However I was introduced to this concept of "atmospheric nitrogen" in a university thermodynamics class, but I have not been able to find any references in my web queries. Does anyone know where this topic might be discussed more thoroughly? Perhaps I am mis-remembering the terminology? — Preceding unsigned comment added by Simchuck (talk • contribs) 3 October 2012

You seem to be searching for how to sign your posts. As stated near the top of this page, you simply type 4 tildes (like this:~~~~) and your signature will be automatically displayed. mbeychok (talk) 20:42, 3 October 2012 (UTC)

The brightly colored image of the fuel droplet in microgravity should be replaced

It looks pretty, but only a handful of people will be able to figure out what this picture is actually showing. (I have a PhD in science. If I can't make sense of it, there's little hope for the average reader). The problem is that the image is too doctored: it is a colorized version of a backlit gray scale image that is a composite of many other images of a rare phenomenon that people do not see every day. This is a science article, not an art article. Compositing and colorizing the effect renders it meaningless. Replace this image with a grey-scale single frame image of the same effect. 129.63.129.196 (talk) 16:10, 27 June 2013 (UTC)

Thank you for already posting this comment. I'd like to emphasise that this pictures doesn't fit in here. I can't figure what this picture might be showing me. It looks more like an angelic art drawing than something connected with combustion. I would support exchanging it. 86.56.88.118 (talk) 08:46, 25 August 2013 (UTC)

Recent update

Some earlier Talk discussion indicated a need for more references, clarification on the nature of incomplete combustion, and the extent of NOx presence in excess air combustion products. To accommodate these and other suggestions, two new sections were created, and various minor edits were performed to bring greater consistency in symbols and concepts throughout the article. Several new references to combustion and the calculation of combustion extent were found, and added. Thermbal (talk) 18:04, 4 July 2013 (UTC)

• This article needs a section on thermodynamics and kinetics of combustion (first chapter of any textbook on combustion) instead of mostly irrelevelant discussion of complete vs. incomplete combustion. Methane never burns completely to CO2 and H2O, but (depending on pressure and other parameters) products of combustion, including dozens of intermediate species, tend to get to the thermodynamic equilibrium. Completeness of combustion is the measure of the ability of the products to reach equilibrium concentrations and in general depends on kinetic factors and times of residence in the combustion chamber. --Fedor Babkin (talk) 06:16, 15 January 2014 (UTC)

Error?

This reaction releases −242 kJ/mol of enthalpy (heat):

242 or 572? — Preceding unsigned comment added by 190.134.13.35 (talk) 05:56, 6 October 2014 (UTC)

Quantum ellipsis

Uncatalyzed combustion in air requires fairly high temperatures, because quantum mechanics forbids the reaction between the rare triplet state of the familiar dioxygen and the common singlet state of fuels.

How can fuels be in a singlet state? I thought that was for electrons.

How can triplet and singlet states be rare and common? 89.217.28.204 (talk) 17:04, 11 January 2015 (UTC)

Clarify scope

It took me a while to figure out what the difference between the fire article and combustion article are supposed to be about because in normal usage they and burning are synonyms. The fire and combustion leads do not clearly define the difference in scope of the two articles (burning redirects to combustion). Would anyone object to my editing this lead to say something like "fire and combustion are frequently used as synonyms but this article's scope is about combustion as a chemical reaction, see fire for information for the phenomenon (observation or experience). I mentioned this topic on the fire talk page with the option of a hatnote but in my opinion there are too many hatnotes here already. Jim Derby (talk) 01:46, 12 March 2015 (UTC)

Explosion = detonation? Internal combustion engine: no explosion?

The section Rapid says that the explosion term is inaccurate for an internal combustion engine (but doesn't say what is accurate). It also equates explosion and detonation. The RedBurn (ϕ) 09:36, 26 July 2016 (UTC)

Of course it's wrong. A detonation, by definition, has a flame front velocity faster than the local speed of sound, thus a shock wave is formed. This does not happen in internal combustion engines: they may (in a fault condition) begin to combust simultaneously across the whole chamber, a condition known (variously) as knocking, but that is caused by the optical transfer of heat energy triggering a simultaneous ignition, not the detonation of the mixture. Wikipedia's coverage of knocking is, as usual for car articles, unsourced and execrable. Andy Dingley (talk) 22:49, 26 July 2016 (UTC)

Sulfur and H2SO4 by product

Could someone please add to the equations of fuel combustion the stoichiometric balance of Sulfur to produce sulfuric Acid. — Preceding unsigned comment added by 66.185.99.227 (talk) 01:18, 27 November 2017 (UTC)

Incomplete combustion hoax

Incomplete combustion is a big misunderstanding. When something is burned, for example wood, you either have nothing but ashes, or you have some wood left over and you can burn the rest later. The second case, where you have some wood left over, is incomplete combustion. This is a much simpler and more truthful definition of incomplete combustion than the long convoluted misleading hoax definition in this article. Brian Everlasting (talk) 03:52, 11 January 2018 (UTC)

The sections on incomplete combustion look fine to me. To persuade readers of this Talk page that some or all of the offending sections are a hoax, or inaccurate, it would be helpful if you quote one or two sentences or statements, and explain why you think they are incorrect. So far, your criticism is so vague that it is likely no-one will agree with you. Dolphin (t) 04:09, 11 January 2018 (UTC)

Not entirely accurate

"Combustion, or burning,[1] is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke." Over my 40 year career at Pratt & Whitney burning Jet fuel to develop low emissions combustors, the products of combustion are NOT know as smoke. Smoke is a product of combustion only so much as a product of incomplete combustion: it is carbonized particles from unburned fuel. From combustion of Jet fuel, the real products of combustion are CO2, water vapor, and much smaller amounts of oxides of nitrogen, CO and UHC (unburned hydrocarbons) which are gaseous. These emissions are determined via analysis of the gasses; smoke is determined by passing a sample through a filter paper and measuring the reflectivity of the spotted sample against a pure white filter. — Preceding unsigned comment added by Sbxstr (talk • contribs) 18:19, 5 October 2018 (UTC)

"Torching" listed at Redirects for discussion

A discussion is taking place to address the redirect Torching. The discussion will occur at Wikipedia:Redirects for discussion/Log/2020 October 25#Torching until a consensus is reached, and readers of this page are welcome to contribute to the discussion. Beeblebrox (talk) 20:18, 25 October 2020 (UTC)

Fringe theories

I removed the following paragraph, and it has been re-added:

Combustion of an organic fuel in air is always exothermic because the double bond in O₂ is much weaker than other double bonds or pairs of single bonds, and therefore the formation of the stronger bonds in the combustion products CO₂ and H₂O results in the release of energy. The bond energies in the fuel play only a minor role, since they are similar to those in the combustion products; e.g., the sum of the bond energies of CH₄ is nearly the same as that of CO₂. The heat of combustion is approximately −418 kJ per mole of O₂ used up in the combustion reaction, and can be estimated from the elemental composition of the fuel.

The sole reference is a self-cited paper (the author of the paper is the editor who added the paragraph).

That the claims are also incorrect isn't really relevant to this, but I'd just like to point out that no great chemical insight is required to determine that they are. Combustion, for example, is exothermic by definition (so there's no need to explain why it is in a special case), and there are organic molecules which, depending on your definition, do not combust or require no O₂ to do so.

IpseCustos (talk) 09:00, 10 June 2022 (UTC)

This short paragraph makes correct and relevant scientific statements about bond energies and the heat of combustion. It states documented, verifiable facts based on universally accepted values of bond energies. That heats of reaction, including combustion, can be estimated from bond energies is also universally accepted in chemistry. A peer-reviewed reference providing all the details is provided for verification. In short, nothing is scientifically incorrect about this paragraph.

The claim that "combustion ... is exothermic by definition" is highly questionable and needs to be referenced. Combustion of an organic fuel is an example of a chemical reaction, and the heat of reaction depends on the bond energies or on the enthalpies of formation of reactants and products. How does any heat of reaction become negative (exothermic) by definition?

Furthermore, an "analysis" just "by definition" is unable to provide good quantitative estimates of the heats of combustion, unlike the last sentence in the quoted paragraph. Why, for instance, is the heat of combustion, per gram, of carbohydrates more than twice smaller than that of fat? Because carbohydrates, containing oxygen atoms, react with less O₂ than the corresponding mass of fat. A mere definition does not provide this useful result.

The last sentence by IpseCustos also does not hold up to careful scrutiny. The quoted paragraph, being about "Combustion of an organic fuel in air", makes no statement about "organic molecules which ... do not combust". Next, if organic molecules "require no O2 to do so." then they violate the definition of combustion given in the first sentence of the Wikipedia article and possibly the premise of "Combustion of an organic fuel in air".

Editors are of course free to replace this paragraph with a better, even more widely applicable and more accurate explanation (properly sourced) of the heat of combustion and its quite strict proportionality with the amount of oxygen consumed. But just deleting this correct short paragraph with its explanation of a central quantitative aspect of the heat of combustion is not in the interest of Wikipedia readers.

Klaus Schmidt-Rohr (talk) 14:58, 10 June 2022 (UTC)

I don't think I've ever seen educational material present combustion as anything but exothermic by definition — if a reaction qualifies as combustion, it is exothermic, simply because of the meanings of the words, though whether it is vigorously exothermic is then an empirical matter. To the concerns in my edit summary, I'd add that the details of energetics may be unsuitable for that point in the article. The typical reader of an article on a broad topic like combustion, particularly its opening paragraphs, may have only limited knowledge of which chemical bonds typically occur in fuel molecules. Consequently, citing a table of bond energies is basically assigning a homework problem, and one for which the student only has some of the necessary information. For encyclopedia content that is obligated to be verifiable, that's rather poor form. Moreover, the cited table of bond energies is by itself insufficient to say that one sum of energies is nearly the same as another. What counts as "nearly"? Citing the Chang (2010) textbook at that point merely disguises the fact that the nearly claim comes from a paper about which conflict-of-interest concerns have been raised. XOR'easter (talk) 17:31, 15 June 2022 (UTC)

References