What is visa requirement to attend a conference in Beijing and how many days does the process will take?

I have been invited to attend the Student Conference on Conservation Science (SCCS) in Beijing. I have a formal invitation letter from the conference organizers as well as the scanned copy of the Invitation Letter from the Duly Authorized Unit (ILDAU) in hand. Will the scan copy of ILDAU work? I will provide the above mentioned doc.s along with a filled Vise Application form and my passport. What else is needed? And very importantly, how many days the visa process will take once the passport is submitted to CHinese Embassy for visa?

Best regards,