The process is so efficient that all the usual soot is burned before it goes up the chimney, while the burning temperature is low enough for all the sulphur to be left behind.

• 这个过程是利用率非常高的，能让一般的煤烟都在排到烟囱里之前燃烧，同时起燃温度足够低可以让硫被留下来了。