Since 1995, Padaeng Industry has imported zinc sulphide as a feedstock for the refinery. Because of its slightly different properties, zinc sulphide must first be roasted to form the oxide “calcine” before the zinc can be extracted.

The company has converted its operations to include a facility to produce zinc oxide (calcine). This facility is located on the grounds of the Padaeng Industrial Estate at Map Ta Phut in Rayong province on the eastern seaboard of Thailand, which began operations mid-1995. Zinc sulphide is converted into calcine during the roasting process, while the sulphur constituent is converted into saleable sulphur acid. The calcine is then delivered to the zinc smelting plant in Tak province.

The ore roasting plant in Rayong was established in 1995 to treat the imported zinc sulfide concentrate and transform it into calcine before sending it to the Tak plant for smelting into zinc metal.

Once PDI decided to close the conventional zinc business, the ore roasting plant discontinued its operation at the end of 2016. The machinery will be partly dismantled to transfer the useful equipment to the PDI-CRT project, which will recycle metals from industrial waste.