Reverse Flow Issues for Pulverised Coal Injection
 

I am analysing a pulverised coal injection process and every time I run my model I am having severe reverse flow issues on numerous faces of the pressure outlet along with a solution that does not converge properly.
I have tried refining the mesh and also ensuring the inlet conditions are correct and have a significantly higher pressure than the outlet but still no luck.
Any suggestions would be much appreciated.
Thanks.