The adiabatic flame temperature (theoretical maximum temperature) of black coal in air is over 2000oc. if the ambient temperature is 20oc then the theoretical maximum efficiency of a coal fired power station is approximately 87%.
why then is the efficiency of even the best coal fired power stations less than 50%.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.

it is the most commonly accepted one