The Ashio smelter was built as the "Naori Bridge Sub Factory"in 1884. To keep up with the increasing smelting operations, a Bessemer rotary kiln was introduced in 1893; however, the amount of sulfuric acid gas inceased.
At the Ashio smelter, many systems were improved in order to remove the gas. In1956, with the flash-smelting system technology imported from Finland's Outokumpu Company, a method to remove smoke and other by-products of sulfuric acid gas was completed. It was the first time in Japan for the emission of sulfuric acid gas to be stopped. these smelting techniques developed in Japan and around the world continue to help eliminate pollutions from copper factories even today.
In 1973, the Ashio copper mine was closed. After that, the smelter began to refine imported minerals. The Ashio line was abolished in 1989, forcing the Ashio Smelter to stop operation since it was no longer able to transport copper by freight cars.
The storage tanks of sulfuric acid
