Recover accumulated cenvat credit

There is no way.

CENVAT Credit is allowed for its utilisation towards removal of Finished goods or inputs as such. While removing exempted goods you are not required to pay any duty and therefore the same cannot be utilised.

If the assessse is unable to utilse CENVAT Credit, bacuse of export, than as per Rule 5 of CENVAT Credit Rule, 2005, refund can be claimed, only to the extent of inputs used for manufacture of goods, which has been exported.