how much years sponge iron field going?

Answer 1

Sponge iron is the product created when iron ore is reduced to metallic iron, usually with some kind of carbon (charcoal, etc), at temperatures below the melting point of iron. This results in a spongy mass, sometimes called a bloom, consisting of a mix of incandescent wrought iron and slag.
Producing sponge iron and then working it was the earliest method used to obtain iron in the Middle East, Egypt, and Europe, where it remained in use until at least the 16th century. There is some evidence that the bloomery method was also used in China, but China had developed blast furnaces to obtain pig iron by 500BC.

The advantage of the bloomery technique is that iron can be obtained at a lower furnace temperature, only about 1100 C or so. The disadvantage, relative to using a blast furnace, is that only small quantities can be made at a time.