Refund of sgst procedure

Hello, I have a New Manufacturing Unit in Andra Pradesh & procuring Inter & Intrastate purchases, and my sales 100% to Tamilnadu only. So that i have Utilized IGST Credit for Making IGST Payment which is sufficiently available.  

In My Credit Ledger Accumulated  SGST Balance was lying for more than 6 months. What is the procedure to get a refund of that SGST Amount?  Because i have no plan for Intrastate sales in next 1-2 years.