Subjectivist wrote:Pardon the interruption but you are mixing up methane combustion designed to produce heat and methane conversion to produce cyclic hydricarbons for chemical use.
Nope.
It is acetylene what is industrially produced this way and benzene is only a nuisance by-product of this process.
Aromatic hydrocarbons (including benzene) are petroleum product.
Acetylene is far too valuable to convert it into benzene this way by design.
Sure, you may get a tiny tiny TINY production of benzene, but the goal of a power plant is to burn the methane as completely as possible to spin a gas turbine.
Engineering is an art of compromise.
They want to achieve as high burning temperature as possible, just to maximize yield of conversion of heat into motion and then electricity.
The greater difference between the heater and cooler, the better the efficiency, as per Carnot cycle where
Max efficiency = [T(heater)-T(cooler)]/T(heater).
Complete combustion requires significant excess of air but such excess of air would lower combustion temperature and T(heater) from Carnot cycle by the same.
That would be detrimental to efficiency.
So they have to strike a compromise, use afterburners (which are by no means perfect because they must handle fast flows and already large volumes) etc.
Allowing methane to be wasted producing anything but heat defeats the whole purpose of a power plant and they work fairly hard at getting combustion efficiency as high as they can achieve.
It is better to waste a bit rather than produce more entropy and less electricity as I have explained above.