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。