it usually takes 4 working days from date of submission to the date of collection. You need apply for a category of visa in Chinese embassy in Iran. You can submit application by youself, you can also ask someone else to do it for you. the application by mailing is not accepted by the emnbassy. Please see http://ir.chineseembassy.org/eng/lsfw/t141455.htm for what type of visa you need to apply for