Based on your query it seems to me that your the firm is a trader of goods (If it is a manufacturer than apply for excise registration and export goods by following rule 19 of CER, avail credit of ST paid on removal of goods and than claim refund if you are unable to utilise credit). Trading is in negative list of service tax. Hence question of registration under ST is not at applicable i.e you can’t apply for registration. If you apply for registration under Bussiness auxiliary services still you can't apply for refund as these services are provided for provisioning of a service which is outside the ambit of service tax and hence CCR-2004 or the export rules made there under are in-applicable. So applying for registration with ST deptt. is of no use to you.
Based on my knowledge about ST, Customs and Excise laws, in my opinion trader of goods is not eligible for any refund of ST paid. However you can save yourself from Excise Duty by applying for registration as merchant exporter under CEA 1944 and procuring goods under rule 19 of CER.
I would really like to see someone who differs from me.