Refineries in China are all state owned. You'll need "guanxi" to do business with any of them. It's illegal to mine, or refine gold (unless you're part of the state) in the People's Republic, I'd recommend you go to HK. If you're not Chinese, and you've never done business in China before, I would strongly recommend you tread carefully. There are some big LMBA accredited refineries;
Shandong Zhaojin Gold & Silver Refinery Co Ltd
The Great Wall Gold & Silver Refinery of China
Inner Mongolia Qiankun Gold and Silver Refinery Share Company Limited
Jianxi Copper Company Ltd
Shandong Zhaojin Gold & Silver Refinery Co Ltd
Zhongyuan Gold Smelter of Zhongjin Gold Corporation
Zijin Mining Group Co Ltd