Buying aluminum ingots A7, 50000 tons monthly, to China

We are buying aluminum ingots A7.
Purchase quantity: 50,000 tons per month.  
Annual purchase quantity: 600,000 tons.
Country of origin: Africa, South America, Middle Asia, Europe or other countries.
Contract period : annual  contract
Destination Port In China: Shanghai, Guangzhou, Qinzhou.
Payment method: Irrevocable and non-transferrable DLC MT700 at Destination port after SGS Inspection report or CIQ Report.