CAIRO - Orascom Construction Industries (OCI), Egypt's biggest listed firm, said on Wednesday it signed a deal to buy 100 per cent of MICRO Chemie B.V., which owns and operates ammonia storage tanks. MICRO Chemie has storage tanks with a total capacity of 30,000 tonnes and a lease for a terminal located at the port of Rotterdam in the Netherlands, Orascom said in a statement. It did not give a price for the deal.