Aside from its use in generating electricity at power plants, how is coal used?
There are two kinds of coal: steam coal, which is used to generate electricity, and metallurgical coal, which is used in the production process for certain metals – especially steel. Virtually all steel utilizes coal. Steel is an alloy of iron and carbon. Coking coal is a source of carbon in the smelting process.
煤炭分两种：动力煤（用来发电）和冶金用煤（在某些金属的生产过程中使用，尤其是钢）。事实上所有的钢在生产时都要用到煤炭。钢是铁与碳的合金，焦煤便是熔炼过程中碳的来源。