Catalytic cracking is a main oil refining technique of making heavy oil lighter, and the mark and pillar of oil refining industry.

催化裂化是重质油轻质化的一个主要炼油工艺，是石油加工工业的标志和支柱。

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Next up is the primary sedimentation tank, where sludge settles to the bottom and lighter liquids like grease, oil and soap rise to the top.

下一步就是一级沉淀池，污泥沉淀到底部，轻质液体例如油脂、油和皂类浮到上面。

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Daily maps of oil distribution produced by NOAA show predicted heavier and lighter oil movement near the Gulf coastline.

由NOAA(注1)绘制的每日油污分布地图预测了海湾沿岸附近的轻重油污的流动情况。

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The oil is not thought to be crude oil but some sort of lighter oil but it is not yet known exactly what the substance is.

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For now, China has to blend Venezuela's oil with lighter crudes or sell it unrefined.

FORBES: Energy Outlook 2009

So transporting gloopy oil is far more profitable than shifting lighter-than-air gas.

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