What fuel did ancient people use to refine iron

Ancient iron smelting the most important fuel is charcoal

The disadvantage of charcoal is that it does not have a high combustion value, and the temperature it can reach is not high enough; the advantage of charcoal is that it has fewer impurities, and the iron smelted by it is of a better quality

China began to use coal as a fuel for iron smelting after the Song Dynasty, especially when the forest resources in the north were tight. After the Song Dynasty, China began to use coal as a fuel for iron smelting, especially in the northern part of the country where forest resources were tight. Because coal contains sulfur, phosphorus and other impurities, resulting in smelting iron is more brittle, the quality is not good

So, the Ming Dynasty, southern Guangdong with charcoal smelting iron is more popular, was used to casting artillery; while the north of the iron smelted with coal is not popular.