Read this book (how to use curvilinear grid), it can be helpful. Good luck.

You can check FireFOAM. It's open source and since it is based on the FOAM suite it could provide arbitrary curvilinear meshes.

You can simulate your topic easily by using AVL Fire , CFD code. Kindly see the following paper and link below:

“CFD modelling of air-fired and oxy-fuel combustion of lignite in a 100 kW furnace”, Fuel, vol. 90, no. 5, pp. 1778-1795

http://www.sciencedirect.com/science/article/pii/S0016236111000160

Good luck

Regards