Toyo Smelter ＆ Refinery

The Toyo Smelter ＆ Refinery is located in both Saijo City and Niihama City, Ehime Prefecture. The Toyo plant is a large-scale seaside smelter that mainly produces copper, gold, silver, and platinum group metals. It has established the world's top-class technologies for smelting, production control, and environmental preservation.

Raw Materials

There are two types of copper ore: copper sulphide and copper oxide, and we use the former for raw materials. As financers of overseas copper mines in Peru, U.S., Chile, Australia, etc., we secured a 40% raw materials in these in-house mines. Although the average grade of copper ores extracted from the major mines is 1 to 2％ currently, we import purity-increased copper concentrate whose grade is about 30％ from overseas. Copper concentrate contains about 30％ iron and the same percentage of sulphur content, but it also contains a small amount of precious metals, such as gold and silver, all of which are collected in our precious metal refining plant. In addition, in the Toyo plant, we use gold ore yielded from our Hishikari Mine （Kagoshima Prefecture） as solvent （silica） for refining copper.

Copper Concentrate
（Candelaria Mine, Chile）

（Composition）
Copper: approx. 30％
Iron: approx. 30％
Sulphur: approx. 30％

Gold Ore
（Hishikari Mine, Kagoshima Pref.）

（Composition）
Gold: 40 to 45 g/t

Copper Smelting Process

Unloading Copper Concentrate

Copper concentrate to be smelted is carried in by a special carrier and then unloaded from its special berth. Up to 30,000-ton class carriers can dock in the berth.

Concentrate Dryer

Since copper concentrate contains about 8％ water, it is dehydrated using a dryer. For dehydrating concentrete, not only dryers that use heavy oil but also steam dryers that use the heat of steam collected in the plant are used, which helps save energy.

Flash Furnace

In order to make crude copper of 98％ purity from copper concentrates, copper is concentrated in a flash furnace first. Copper concentrate and gold ore are put in the flash furnace, and hot wind is blown in for them to be oxidized and melted. Because sulphur content in the copper concentrate works as fuel to maintain high temperature, the furnace is called flash furnace. Copper that has been concentrated so that its grade is 60 to 65％ is called matte. Dependant on the difference in specific gravity, slag （its main components are iron oxide and silicic acid） is separated from matte.

Converter and Refining Furnace

Matte with a copper grade of 60 to 65％ is sent from the self-blast furnace to the converter in order to increase its purity. With oxygen blown into the converter, the sulphur content is removed as a gas and iron is removed into silicon （main component of gold ore）. As a result, a portion of the matte becomes slag. Thus, crude copper with purity of 98％ is taken out from the converter to a refining furnace, where oxygen concentration is adjusted and refining anodes are cast.

Sulphuric Acid Facility

The gas generated while copper is refined （SO2） is collected and changed into sulphuric acid in the sulphuric acid facility.

Casting Machine

Refining Anode

One anode weighs about 400＆nsp;kilograms.

Copper Electrolysis Tank

There are two electrolytic methods for producing electrolytic copper with a purity of 99.99％: one is to alternately place refining anodes and negative plates in an electrolytic tank and the other is the permanent cathode method that uses stainless plates. Precious metals or rare metals contained in the anodes remains as anode slime （deposit） at the bottom of the electrolytic tank and is then sent to the precious metal refining plant.

Products

Electrolytic Copper

The refining anodes taken out from the refining furnace is changed into electrolytic copper with purity of 99.99％ through an electrolysis process.

Slag Sand

Slag Sand （water-granulated slag） is produced by placing the solution part of slag into running water. Since extraction of sea sand has been progressively banned due to consideration of the environment, Slag Sand is drawing attention as a substitute for concrete fine aggregate material.

Slag Powder

The remaining copper content is removed from the slag generated in the converter by a concentration process, and is then shipped as slag powder.

Copper Sulphate

Slag powers are made by refining the electrolytic solution in the copper electrolysis tank. Slag powder is mainly used for the copper plating of printed circuit boards.

Precious Metal Refining Process

Precious Metal Refining Plant

The anode slime （copper electrolysis slime） remaining in the copper electrolysis tank is changed into precious metals such as gold and platinum group metals in the precious metal refining plant of the Toyo Smelter ＆ Refinery. In the precious metal refining plant of the Toyo Smelter ＆ Refinery, hydrometallurgical refining （with no furnace used） has been adopted in all the refining processes. Therefore, each process can be seamless and automatically controlled, considerably reducing the gold recovery period, as compared with the conventional refining method. Also, in precious metal refinement, hydrometallurgical refining technologies we have accumulated through nickel smelting are utilized.