EDC, PDF transport and turbulent combustion

HP

Hi. I have used the non-premixed combustion model to simulate coal combustion in PF burner. The assumption of the chemical equillibrium was acceptable for my case, but I had other problems due to the 2 mixture fractions restriction (I can give more information on this). Therefore I would like to upgrade the combustion model I use, to EDC or PDF transport, but I am not quite sure, which are their main differences and which model is more suitable for my case (coal combustion).

Could anybody with experience on these models give me some guidelines?

PS. The computational cost of the two mixture fraction approach (non-premixed model) is already the most cost I can afford. So please relate it, if possible, to the cost of the other models (for a certain number of species for coal combustion)