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.