secondary refining

例句：

1. 1. The company's primary focus ison primary refining and downstream processing.
   该公司的主要关注点是初级精炼和下游加工。
2. 2. The process of secondary refining involves removing impurities from thecrude oil.
   二次精炼过程涉及从原油中去除杂质。
3. 3. In secondary refining, the crude oil is further processed toproduce refined products.
   在二次精炼过程中，原油进一步加工以生产精制产品。