Can a manufacturer trade raw materials?

If premises are separate then you can traded the same excisable and non-excisable goods. 

A manufacturer can trade (Sale) raw materials. For Central Excise purpose, you are removing inputs from registered premises for which you have to pay excise based on valuation of the raw materials at the time of removal. You need not keep separate account of material sold.

If you are keeping Goods to be traded separately from similar inputs use for manufacturing, then you need to obtain Traders registration from Central Excise. You can then pass on the cenvat credit on the goods traded. You will have to keep separate account of the goods traded.

Hope this is of some use to you.

If the case is that :- Raw material purchased @ excise duty , say 8 % in year 2009, and removal of this raw material is in 2014 when Excise is 12 %, what credit to be passed on ???

Dear Mayank - If Input (Raw Material here) removed as such than the credit taken at the time of receivng of such input should be reversal, irrespective time of holding.  

Dear Subrata - Provision of Cenvat Credit applicable for both Manufacturer and as Trader. There is no confiliction if he removed RM from factory gate. Depends upon circumstances he has to follow the process and maintain seperate exice numbers. Thanks,