The fourth best use of refinery gas is purification and sale as natural gas, if the market value of the gas (on an energy basis) is near that of low sulfur fuel oil.

炼厂气的第四种最好应用是，如果天然气市场价格(从能源角度计算)接近低硫燃料油的价格，可将炼厂气通过净化作为天然气销售。

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Under the new rule, by 2015, existing boilers must switch from No. 6 oil to a low-sulfur version of the No. 4 heating oil or to an equivalent cleaner fuel.

按照这项新法规，截止2015年，现存锅炉必须由6号燃料油换成4号低硫型燃料油或与之相当的较为清洁的燃料。

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The reactor, according to Petrobras, was built with technology to produce oil with low sulfur content, respecting the new environmental standards on fuel quality.

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