there is enough oxygen available, CO will continue to burn off because it's an unbalanced molecule. There's a lot of reactions going on in the blue flames, some but not all attributed to burning methane. If the blue flames are just CO, it's not combusting all the way and energy is being wasted. Check out Yanche's formula for anthracite and you'll see allot of available carbon and some is fixed to Hydrogen to make up some Methane. It's why we see the blue flames in the beginning and they tapper off as the anthracite glows red as the carbon is combusted for most of the burn cycle. This is the part where Yanche changes us to defer to our High School Chemistry books - mine's not handy but here goes anyway
Nature likes to balance out or neutralize all electrical charges and given the chance, it will. Kind of like lightning during a thunderstorm. That's what we strive for when we burn fuels - to rearrange the charges in a way that releases the stored energy by recombining (combusting) them with Oxygen. Free elemental Carbon (C) has the negative charge of -4. An Oxygen molecule has a positive charge of +2 but in nature Oxygen hooks up with another Oxygen molecule and is naturally found as O2 (two Oxygen molecules=+4). It's more complex, but this example is simplified. If there's enough Oxygen in the firebox, the Carbon in the anthracite will convert completely to CO2 (carbon dioxide) to make a more balanced molecule and release all the heat available. If it happens half way**
there's still energy to be released , CO(carbon monoxide) is formed. The Carbon Monoxide molecule (CO) still has a charge to be neutralized by the charge of another single Oxygen (O) molecule to make CO2 (carbon dioxide):
C(carbon)+O2(two oxygens)=CO(carbon monoxide**)+O(one oxygen = CO2(carbon dioxide) When this happens, all the heat available is released. That's the combustion efficiency of Yanche's post.
We all know it doesn't happen completely at 100% all the time and CO is one of the combustion byproduct gasses to be concerned about.
Methane (CH4) is the first simple 'balanced' formula for carbon. The simplest hydrocarbon. It's the main component of coal gas - the gas of ' the Canarie in the coal mine' infamy. It balances with four Hydrogen (electrical charge or valance of +1) to make Methane gas. Combusting methane with oxygen releases the energy stored in the carbon/hydrogen bond: CH4+2(02)= (H2CO + H2O)+O2= CO2 + 2(H2O)