Kosaka smelter was put into operation in 1900 to treat ores mined nearby. Since then main raw material for the copper smelter has been coarse ores mined in the old time or concentrates originating from a finely mixed sulfide mineral, so-called “Black Ore”. Even now the copper concentrates contain a high level of impurities e.g. galena, sphalerite, barite and other unfavorable elements from a metallurgical point of view.
In 1967 copper smelting process was changed from the conventional blast furnace to the Outokumpu type flash smelting furnace. During thirteen years operation of the flash furnace, we have continuously endeavored to solve problems in many aspects, including refining, for the purpose of (1) getting higher quality products from complex and/or dirty copper resources, (2) yielding more elements at a higher recovery rate, (3) saving operation costs especially energy cost to overcome successive oil crises, and (4) meeting strict environmental regulations.
It is a distinctive feature of Kosaka Smelter that the copper smelter has a really close relationship to an adjacent lead smelter in handing intermediates to each other. This combination enables us to recover twelve kinds of products in total, namely, copper, gold, silver, lead, bismuth, antimony, selenium, tellurium, gallium, indium, blue vitriol, and sulfuric acid. Current production is 4, 000 metric tons of copper per month. In this paper improvements and modifications during the last decade are explained in detail.

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Miyako smelter is located at Miyako-shi, Iwate-Prefecture, and in the center of National Park of Rikuchu Kaigan.
This smelter was started in 1938, but ceased its operation from 1945 to 1958 because of the World War II.
Our copper ores are smelted in a blast furnace and converter furnaces. To smelt more copper ores improvements were made in many points, in which briquetting of concentrates, blast furnace dusts and converter furnace dusts was adopted.
We are excavating good aspects of the blast furnace day and night, and making efforts to continue its operation in the future.

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Onahama Smelting & Refining Co., Ltd., the first joint venture of Japanese copper producing firms, started its plant in April 1965, which was originally designed for a capacity of 5, 000 mtpm of cathode copper.
In December 1968, the addition of NO.2 tankhouse raised the capacity of cathode copper up to 12, 000 mtpm.
In 1973, it was further expanded up to 20, 000 mtpm with the addition of NO.2 reverberatory furnace, a Hazelett casting machine, NO.3 tankhouse, a MgO plant and a gypsum plant. Since the start-up of the plant we have made much effort to control the sulfur oxide emission, recovery rate of sulfur from the smelter being kept over 99.7% at present.
We have achieved constant compliance with sulfur oxide emission standard and ambient air standard.

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The Nikko Copper Works of the Furukawa Electric Co., Ltd. is the oldest copper refinery in Japan, built at its present location of Nikko, Tochigi Prefecture in 1906.
The works is characterized by the refining of crude copper supplied from other smelters, unlike general smelters where copper is made from ores in an integrated production.
When the copper refining plant facilities became so old as to require rebuilding, a plan was worked out to discontinue the use of small cathodes and to thoroughly rationalize operations including anode casting. A new copper refining plant was completed based on the plan in 1978. In addition to the conventional techniques, varied new technologies on operation scheduling, equipment layout, starting sheet stripping, etc. are incorporated in the new plant, making it one of the most up-to-date copper refineries rationalized to the point that, though small in scale, 4, 000 tons/month, it is comparable in many ways to a 10, 000 tons copper plant. The Nikko Copper Works has recently increased its copper production by 4, 600 tons a month and is now one of the world's leading copper refineries.

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Ashio copper mine was discovered about four hundred years ago. Since Furukawa began the management in 1877, the whole amount of copper product reached 0.8 million tons until its closing in 1973.It served as the foundation of industrial development in Japan.
Copper smelting method has also been developed in Ashio according to the technology progress of the world. Mafuki Method and the blast or reverberatory furnace method were used from 1877 to 1956. Ashio Smelter was the pioneer of copper smelting in Japan. The newest method of the age could always be seen here.
The first flash furnace in Japan was adopted to Ashio Smelter in 1956. It has been given a lot of improvements continuously for 24 years to complete the original equipments suited to the flash smelting in Japan, and to establish a stable operation. Furukawa type flash furnace became famous throughout the world for its advancement in anti-pollution and energy saving properties, and high product ability in the large scale furnace. Flash furnaces are now adopted not only in Japan but all over the world. Furukawa has participated in planning and technical guidance of those furnaces.
In 1978, against the increase in energy cost, Ashio Smelter developed a new method for flash smelting in which oxygen enriched air is used. This saves a great deal of thermal energy.
The history of anti-pollution in Ashio is old. Neutralization ponds were equipped in 1892, and a plant for the wet type desulfurization of waste gas was built in 1897. The system of waste water treatment was especially improved to have a larger scale. Treated water here is quite clean and has been used as drinking water for more than twenty years.
The first electro-static precipitator, so called Cottrell, in Japan was built here in 1918, where arsenic oxide was started to produce. Today, arsenic oxide is also produced from waste acid water in the sulfuric acid plant by the special neutralization method. The flash roaster used here is the only one in Japan. Other by-products here are bismuth since 1923, Ashio Metal which is the alloy of Pb and Sn, Sb₂O₃, and etc.
The scale of Ashio Smelter is rather small but it is a unique inland smelter which has the oldest history and the best technology to use its own electric power plant.

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Hitachi Smelter & Refinery of Nippon Milling Co., Ltd. has greatly devel oped its technology and has increased its copper production capacity.Oxygen Smelting Process was applied in 1958, and concentrates were charged into converters and blister copper was directly obtained by using oxygen enriched air. In 1972, the Oxygen Smeiting Process was taken over by Flash Smelting Process, With a monthly productlon capacity of 7, 000 tons of copper from concentrates.Oxygen ennchment was also applied to the flash furllace operation in which the high temperature air was supplied by hot stoves.
In addition, the monthly refining capacity rcached 16, 000 tons of copper by constructing a new tank house with a monthly capaclty of 10, 000 tons of electroiytlc copper. The new tank house is equipped with only one over-head crarle, as a result of instaliing highly developed handling machilles and a special double-hook system, That can simultaneously crop both anodes and cathodes.
New slime treatment plant was also constructed, The technology of The Ferric Leaching Process was developed and a high efficiency of copper removal from anode slime was realized.
Owing to the econornlcal suppression, the smelting division has been shut down since September in 1976. The anodes have been transported to Hitachi tallk house from Saganoseki Smeiter.

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Tamano Smelter was constructed as the first copper smglter of Hibi Kyodo Smelting Co., Ltd. whichwasajoint venture of three Japanese pnmary copper producers; MITSUI Mining & Smelting Co., Ltd., NITTETSU Mining Co., Ltd. and FURUKAWA Co., Ltd.
The Smelter started operations in January, 1972, and has the capacity now to produce 8500 tonnes of cathode copper per month. Though matte smelting was based on the flash smelting process of Outokumpu Oy., electrodes were inserted in the settler, which made it unnecessary to provide an external slag cleaning furnace. Copper loss in slag is less than 0.6wt% Cu while copper in matte is 54%. Moreover, the adoption of water jacketed steel plate uptake could avoid the dust trouble through a waste heat boiler.
Matte is treated in one of two hot converters. Converter off-gases are led to a gas cleaning section of an acid plant where flash furnace gas is combined with them. Nearly all sulfur dioxide in these gases are recovered as 98% sulfuric acid.
To aim at a non pollution smelter, off-gas and fugitive gas collecting systems were installed. Converter fugitive gases which are sent to a tall stack only during out of stack times in converter operations, are sucked to the uniquely developed collection systems. A desulfurization plant using the lime process was completed in 1976 to comply with strict regulations. By this more than 99.6% of sulfur is fixed at present.
Blister from converters is treated in two refining furnaces. Old refining furnaces were replaced by larger ones with unit capacity of 330 tonnes in 1975, in order to increase the production capacity, to achive higher efficiency in the operation, and to reduce the cost. For the purpose of simplifying the operation and improving the anode quality, the casting process was throughly made automated and, as the result, high quality anodes suitable for high current density electrolysis have been produced.
An oxygen plant is now under construction to achieve higher efficiency in the operation and to increase the production capacity. Coal milling plant is also to be completed to cut fuel cost.
The refinery started operation with a monthly production capacity of 7, 000 tonnes of cathode copper. Feature of this refinery is the use of periodic current reversal with current density of 348A/m². Developments of special cell bus bars and an automatic short circuit pair detector were useful for power saving. Present production capacity is 8500 tonnes per month.
Purification of electrolyte is done by electrowinning, evaporation using a submerged combustion burner, and crystallization of nickel sulfate.
Crude nickel sulfate and decopperized slimes are sent to Takehara refinery of Mitsui Mining & Smelting Co., Ltd. for further treatment.

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The Hibi Smelter is a copper smelter consisting of two blast furnaces, three Pierce-Smith converters, and two refining furnaces. Presently its production capacity of copper anode is 60, 000 metric tonnes per year.The operation started in 1936.Hibi anodes are transported to internal Takehara Refinery, and refined to electrolytic copper
The features of this smelter are as follows;
1. It uses various kinds of copper bearing materials; concentrates, scraps, residues from brass and copper manufacturingf actories, and by-products from the lead and zinc smelters (Miike, Hikoshima, Takehara) of Mitsui Mining and Smelting Co., Ltd.
2. Heavy oil is injected as fuel into the blast furnaces with preheated air through the tuyeres. Due to soaring price of oil, the temperature of the preheated air is lowered to 250°C from previous 350°C in order to economize oil consumption.
3. The blast furnace off-gas contains 4-5 percent sulfur dioxide, which, together with the converter off-gas, has been also reco vered in a sulfuric acid plant as 98 percent sulfuric acid since 1970
4. Special efforts are exerted to prevent public pollution. The fugitive gases collected from the blast furnaces, the converters, and tne refining furnaces, and the tail gases of the sulfuric acid plants, are led to a desulfurization plant, and most of sulfur remained in these gases is fixed into gypsum. The sulfur diokide of off-gas emitted into the air from the stack is monitored at all times by the municipality at stations around the smelter. The waste acid from the sulfuric acid plant and the waste water from the smeter are sent to the waste acid treatment plant and treated completely before flowing out.

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Takehara Refinery produces 6, 800 tons of electrolytic copper per month by electrorefining the anodes sent from Hibi Smelter of Mitsui Mining & Smelting Co., Ltd. and the blisters sent from Miyako Smelter of Rasa Co., Ltd. and overseas smelters.
Prior to the electrolysis, the blisters are charged into the reverberatory furnace for pyrometallurgical refining.
Anode slimes, which are produced during electrolysis, are treated in the process which consists of decoppering, roasting, smelting and electrorefining, to give highly pure gold and silver. Other rare metals contained in anode slimes such as selenium, tellurium, bismuth, palladium and platinum are also recovered during the treatment. The anode slimes produced at Tamano Refinery of Hibikyodo Smelting Co., Ltd. as well as overseas slimes are also treated in Takehara.
Etectrolyte is withdrawn from electrolysis system and then concentrated in the evaporator. The evaporated solution is led into the crystallizer where copper and nickel sulfate are produced.
Gold potassium cyanide and electrolytic copper powder are also produced at Takehara.
The new plant employing the amine leach-solvent extraction process for copper dross treatment was constructed in December, 1978. The copper sulfate solution obtained in the new plant is fed to the existing electrolytic cells to produce electrowon copper.

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The Naoshima Smelter is located on the Naoshima Island. which lies in the Seto Inland Sea, Japan, about 200 kilometers west of Osaka.
The Naoshima Smelter was built in 1917 to treat domestic copper concentrates with a reverberatory furnace. Since then, the smelter has gradually expanded its production capacity. The major expansion project was completed in 1969 adding a new smelter and a tankhouse with a capacity of 7, 500 tons copper cathode per month. The old smelter was then scrapped at the end of 1973 after 56 years of operation and the entirely new Mitsubishi Continuous Copper Smelting Process has taken its place with a monthly capacity of 4, 000 tons anode from concentrates, while the tankhouse was expanded at the same time.
In total, there are two smelter lines and tankhouse buildings with following production capacities.
Copper conc. treated45, 000 M. t/month
continuous smelter line 17, 500
conventional smelter line 27, 500
Electrolytic copper13, 500
Sulfuric acid41, 000
The conventional smelter is composed of a fluo-sol d roaster, calcine charged reverberatory furnace, three P.S converters, and two anode furnaces. The continuous process is carried out with a smelting furnace, a slag cleaning furnace and a converting furnace which are mutually linked with launders to allow continuous transfer of intermediate metallurgical products. The Naoshima Smelter is expected to develop further in the future with making the most use of this Mitsubishi Process.

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The Niihama Copper Refinery of Sumitomo Metal Mining Co., Ltd., one of the major copper refineries in Japan, issituated in Niihama, one of the leading industrial cities, Shikoku Island, having the Port of Niihama in the back where both coast and ocean going vessels come in and go out through the Seto Inland Sea just outside thereof. The Refinery started operations in 1919 and has been expanded year after year since then. The Refiner produces 10, 000 tons per month of electrolytic copper from refined anode, mainly supplied from the Toyo Smelter which is located in the vicinity. The Refinery also produces many by-products such as gold, silver, platinum, selenium, tellurium, bismuth, nickel and rhodium.

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In order to modernize and scale up our copper smelting facilities, Toyo Smelter was constructed in 1971 on a reclaimed area of about 200, 000m² which stretches from Niihama to Saijo and faces Seto Inland Sea.
In constructing the smelter, we gave special attention to the following points:
(1) Attainment of high recovery rate of sulfur by adopting Flash Smelting Process,
(2) Minimizing of the emission of sulfur by adopting a process for exhaust gas desulphurization with by-product of sodium sulfate,
(3) Accomplishment of high efficiency smelting with a small number of personnel by introducing an on-line computer control system.
Toyo Smelter has just attained 10th anniversary, not only with brilliant operational performance, but also with environmental record. That is typically shown by the following items:
(1) Keep of the smelter availability at more than 98%.
(2) Attainment of the sulfur recovery rate of almost 99%.
(3) Increase of the smelting capacity from 900 tons of concentrate per day to 1100 tons of concentrate per day.
As a result Toyo Smelter has enjoyed popularity for 10 years as one of the most outstanding pollution free and clear smelter in the world.
Toyo Copper Refinery, with production capacity of 4, 500 t/month of electrolytic copper, started its operation in 1971. Sumitomo built Toyo Copper Refinery based on its own technology accumulated over long years of copper refining experience, and paid a great deal of attention to its design so as to provide the following features:
Completely pollution-free process and operation -Spacious refinery layout to enable further expansion-Fully modernized, automated tankhouse equipment and material handling machine to assure high productivity-The most advanced electfolysis technology and management system to provide high quality electroiytic copper at low production cost.
In addition to the above mentioned potential advantages, the development of new technology by our R & D people, as well as operator's steady effort towards improvement of process and operation have resulted in entirely successful production of electrolytic copper since the commencement of refining operation.
With our own up-to-date technology and modernized equipment as a background, Toyo Copper Refinery is believed to be one of the most outstanding refineries in the world.

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In early 1970's, the copper smelting and relating facilities of the Saganoseki Smelter and Refinery underwent an all-out renovation in light of the growing demand for copper and to cope with the stringent environmental regulations of Japan.
The first expansion and modernization program of the facilities was completed in 1970 including the replacement of blast furnaces with a flash furnace. In 1973, the second flash furnace was built and started its operation. Thus fully modernized seaboard copper smelter was born with the annual copper concentrate smelting capacity of 240, 000mt in copper content.
The adverse economic circumstances developed since the oil crisis in 1973 necessitated the Saganoseki Smelter to improve the overall operation by curtailing energy consumption and by improving smelting and refining processes.
As a result, at present, the Saganoseki Smelter and Refinery has become one of the largest and the most efficient copper smelters in the world with the following special features:
1. Flash furnace using hot blast of 1, 000°C with or without oxygen enrichment
2. Labor saving P-S type converters 3. Unique combination of magnetic separation and flotation of converter slag
4. Double anode casting machine with an hourly casting capacity of 80mt
5. Effective emission control by using secondary hood, etc.

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Hachinohe Smelting Company was established on Feb. 1st, 1967 as a joint toll smelter to take advantage of the Imperial Smelting Process to treat mixed and complex ores, especially some concentrates from “black ore” in Tohoku district of Japan and concentrates from Huanzala Mine in Peru. The Hachinohe ISF plant was commissioned in Feb., 1967, and has beensu ccessfully operating with excellent performances.
The Smelter Complex consists of sinter plant, acid plant, furnace plant, and zinc refinery. The sinter plant employs the Lurgi type sintering machine, while acid is produced in Lurgi type double contact acid plant. Some parts of crude zinc producedb y the ISF is further refined by its own reflux ing refining plant. Bullion is shipped without refining.
Since the, operation commencement, various improvements and modifications have been constantly applied to make the plant competitive, emphasizing the theme of “conservation and recovery of energy”. A typical example of the efforts is incorporation of power generator which utilizes waste heat of the furnace off-gas. Now the plant is trying to further strengthen its ability to cope with low production.rate forced by current unfavorable situations surrounding zinc industry

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In December, 1980, new “Electric Furnace Smelting with Hydrometallurgical Pretreatment” started up its operation.
This new plant is producing electrolytic lead, bismuth, antimony, and precious metals as final products and copper sulfide, cement copper, zinc hydro-oxide as by-products, separating arsenic contents as pollution-free compound.
In this paper, there is described 10 years experience of practical operation and history of lead smelting, hydrometallurgical treatment of copper smelting dusts, a short rotary furnace, an electric furnace, electrolytic refining and recovery of by-products from which new plant technology has been developed.

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Iijima Zinc Refinery was constructed in 1971 by Akita Zinc Co., Ltd. established as a joint venture of Dowa Mining Co. and five other zinc producing companies in Japan.
This plant started zinc production in Jan. 1972 and doubled the production capacity of zinc slabs, in 1974, from 6500t/M to 13000t/M.
Now we are permitted to produce only 75% of zinc slabs compared with the nominal production capacity considering the international overproduction against demand.
Recent operating condition at Iijima is very steady and if we are permitted full operation, we will be able to produce more than 14000t/m zinc slabs without any additional facilities.
Adoption of unique residue treatment process which is called Hematite process has been successful in excellent recovery of valuable metals in zinc concentrate, less trouble-some operation and low maintenance cost of autoclaves and also small energy consumption which is comparable to other hydrometallurgical residue treatment processes.
A big effort was devoted against the latest rise of energy price and energy consumption in the whole plant has been remarkably decreased, especially in the tank house. Power consumption for 1 ton of cathode is about 3100 kWh level in spite of abnormal electrolysis operation, that is, current density of 510 A/m² at night or on holidays and 50-250 A/m². in the daytime.

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Akita Zinc Refinery of Mitsubishi Metal Corporation (MMC) started its operation with capacity of 560 tons per month of electrolytic zinc for the treatment of zinc concentrates from Ikuno and Akenobe mines. Akita is located in the northern part of Honshu; Japan, about 500 km from Tokyo. The plant had gradually expanded its capacity and reached 8100 tons per month in 1973.
Silver recovery by flotation and newly developed sulfate roasting were incorporated for residue treatment in 1963. These residue treatment processes are unique and pyrite is used to sulfurize the residue. Since 1973, electric power from MMC's own Onuma geothermal power station has been supplied in addition to hydroelectric power from Komata. The cathode stripping in the tank house has been done by newly developed machines since 1976 which are compact and efficient.
The present capacity is:
Electrolytic Zinc 8100 tons per month
Die-casting Zinc Alloy 3500
Electrolytic Cadmium 30
However, present production of zinc is about 6500 tons per month due to the depressed zinc market.

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The Hosokura Smelter and Refinery, which is located a djacent to the Hosokura Mine, started its operation in 1889 and is at present one of the oldest metallurgical works in Japan.
The plant was further divided into three plants; a lead plant, a zinc plant and an acid plant.
The lead plant having a capacity of 1, 800 t/m electrolytic lead adopts a process which consists of sintering. smelting with ablast furnace, refining with Betts electrolyzing and recovery of byproducts. Electrolytic lead siabs, crude silver, electro- lytic bismuth, antimony oxide and lead-tin alloy are produced by treating the lead concentrate provided from the Hosokura Mine and a variety of lead bearin materials.
The zinc plant adopting traditionai hydrometaiiurgical processes with a capacity of 1, 800t/m electrolytic zinc produces 1 ton ingots of zinc alloy for use in hot-dip galvanizing, electroiytic cadmium and cemented copper with silver.
The acid piant treats sulfur dioxide gas generated at the sintering step for lead Concentrate and the roasting step for zinc concentrate in Lurgi single contact and double contact processes having a combined capacity of 180t/d sulfuric acid.

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For the past decade we have succeeded in establishing a new technology to recover zinc, lead and some valuable metals from leach residues and zinc-containing materials. Our Waelz plant was enlarged in 1971, and as the result the production of Waelz oxide doubled to 20, 000 t/y. In 1975, an additional kiln plant was brought into operation by our associated company in order to process 60, 000 t/y of electric-furnace steelmaking dusts.
As to processing of the Waelz oxide, chloridizing roasting of oxide to separate zinc oxide from lead-cadmium oxide, in combination with improved subsequent treatment, has made it possible to produce electrolytic zinc without trouble. Thus 60% or more slab zinc of 30, 000 t/y has been produced by this procedure. Since April of 1980, when our zinc electrolysis plant was forced to close down for economic reasons, however, further treatment of oxide has been commissioned to other smelters.
The above is the summary of one of items mentioned in this paper. This paper also includes the following subjects:
1. Recovery of lead by soda process.
2. Recovery of cadmium.
3. Production of zinc based wear-resistant alloy, “Beric”.
4. Production of stabilized liquid SO₃, “Nisso Sulfan”.
5. Processing and recycling of the industrial wastes.

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Annaka Refinery of Toho Zinc Company Limited, located seventy miles to the northwest of Tokyo, has the annual production capacity of about 140, 000 tons of electrolytic zinc.
The plant, erected in 1937 for the production of 5, 300 tons of zinc annually, had been enlarged up to the current production capacity until 1967.
For the 1970's decade, confronted with tightening requirements for environmental control, rapidly escalating energy prices and increasing labor costs, extensive improvements were carried out.
This paper presents these significant improvements and achieved results.

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Mikkaichi Smelter, Nippon Mining Co., Ltd., operating since 1954, is at present the only zinc smelter in the world that employs the resistance electrothermic zinc distillation process, which was originally developed by St. Joe Minerals Corp., U. S. A.
Zinc concentrates are first roasted at Tsuruga Plant to produce zinc calcine and sulfuric acid. Zinc calcine is then transported to Mikkaichi Smelter to be sintered, distilled and refined. Products are Prime Western zinc metal, Special High Grade zinc metal, Tailored zinc metal, diecast alloys and cadmium metal
The resistance electrothermic zinc distillation is a distinctive process that has the following unique features:
1) The process uses both coke and electricity as the sources of energy. Although energy consumption per unit of produced zinc metal is higher than those in other smelting processes, eventual energy cost is similar to those of others because of the use of coke in combination with electricity, for the price of coke is cheaper than that of electricity. Also, furnace gas can be further utilized for refining processes.
2) High zinc recovery rate.
3) The process is applicable to any kind of raw zinc materials.
4) High recovery rate of gold, silver, copper and indium.
5) Slag is chemically stable and of comparatively small amount so that it is easy to discard.
In the past ten years we have achieved the followings:
1) Establishing an effective environmental protection system.
2) Improvements in the plant and of equipments for reducing energy and labor costs.
The author firmly believes that the resistance electrothermic zinc distillation process employed at Mikkaichi Smelter has been and will be playing an important role in zinc production in Japan.

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Mitsui's Kamioka Mine and Smelter has an electrolytic zinc plant and a lead smelting and electrolytic refining plant.
While the establishment of lead smelting at Kamioka dates back to the early nineteenth century, the present lead smelting operation utilizing modern equipment began in 1905. However, it was not until 1943 that the electrolytic zinc plant started its operation.
The annual capacity of the main products is: 61, 000 tons of electrolytic zinc; 26, 700 tons of electrolytic lead; 85, 200kgs of electrolytic silver; 276, 000 kgs of electrolytic bismuth; and 4, 700 tons of PW zinc.
Due to the coexistence of both a zinc plant and a lead plant, such advantages as being able to treat zinc leach residue in the lead plant, having a common acid plant for both lead and zinc roasting and being able to treat both zinc and lead processing materials at the appropriate plant, have been enjoyed.
The lead plant consists of a conventional sintering-blast furnace, an electrothermic slag-fuming process and an electrolytic lead refining process. The main features are the above-mentioned electrothermic slag-fuming process which includes direct recovery of zinc metal from slag, complete recovering of sulfur dioxide gas from the sintering plant, a zinc leach residue treatment and a fully mechanized electrolytic lead refining system utilizing large cells with eight workers.
The zinc plant consists of a fluidized roaster, an acid plant, continuous single leaching, continuous purification and a cell room equipped with Mitsui's Stripping System. Featured processes in the zinc plant are the producing of sulfuric acid anhydride, a simplified cadmium recovering process, and such engineering system as Mitsui's Stripping Machine and casting machines. It is significant that Mitsui's Stripping Machine was first made in 1963, based on the technology of the Kamioka's zinc plant. Moreover, this machine was manufactured at Mitsui's own machine shop.
At present, the stripping machines are exported to West Germany, Canada, Australia and Mexico for zinc and copper plants.
For these last ten years, thirty or forty percent of labour savings has been accomplished. Presently, ways of taking energy saving measures are seriously being pursued.

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The Harima Works, constructed approximately 15 years ago in the Harima Industrial zone of Harima Township (partly in Kakogawa City), Hyogo Pref., Japan, as Sumitomo's zinc and lead smelting division, started its operation with a production capacity of 3000 tpm (ton per month) of zinc and 1500 tpm of lead utilizing the Imperial Smelting Process introduced from Imperial Smelting Processes Ltd. England.
This Works, combining Sumitomo's abundant experiences accumulated in copper and nickel smelting with new and epoch-making technologies, has operated profitably for the 15 years of its existence. Today, it is a highly productive and well laid-out sea-side smelter, with a production capacity of 6600 tpm of zinc and 2200 tpm of lead, under the following policies;
1. To manufacture and supply high quality products at low cost.
2. To operate our business while maintaining harmonious relationships with local communities.
3. To endeavor to make this Works a place where daily work is safe, rewarding and enjoyable.

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Mitsubishi Cominco Smelting Co. is a joint venture of Mitsubishi Metal Corp. of Japan and Cominco Ltd. of Canada. The smelter, which is located alongside Mitsubishi's Naoshima Copper Smelter, started its production in October, 1966 and has a capacity of 36, 000 tons per year of refined lead with five-9⁺ purity.
The concentrate feed for the smelter from Pine Point Mine of Cominco is of high grade with low levels of impurities, being particularly low in silver, bismuth, antimony and arsenic, which facilitated a compact plant layout and operation. Concentrate, fl uxes, recycle granulated slag and return sinter are drawn from bins by automatic control over weigh belt feeders. Sintering is carried out on a 20m² Lurgi updraft sintering machine, furnacing in a 1.4m×3.0m water jacketed blast furnace equipped with an Asarco continuous tapper, refining in 150 ton kettles and casting on a 25t/h automatic casting machine. The SO₂ gas from sintering is cleaned in a high temperature baghouse utilizing glass bags and then delivered to the adjacent copper smelter acid plants. The furnace gas after being cleaned in a low temperature baghouse is neutralized with a mixture of slaked lime and calcium carbonate, with gypsum as the by-product. Refining is simply done by decopperizing with Al-Zn alloy and succeeding clean-up by caustic soda for the residual aluminum and zinc elimination.

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Takehara Lead Refinery is designed to produce high quality electrolytic lead and many other by-products both from secondary lead-bearing materials and from purchased bullion.
For treatment of various kinds of secondary lead materials, Takehara lead smelting operation consisting of a blast furnace and two short rotary furnaces is suitable and advantageous in respect to recovery of valuable metals and fixation of hazardous elements. The smelter feed is made up of lead-bearing materials, limestone, and iron scrap. Charge of iron scrap fixes sulphur in the matte without any environmental problems.
The refinery plates out pure lead on lead cathode starting sheets in a hydrofluosilicic acid electrolyte, and leaves antimony, bismuth, gold, and silver to be recovered from the anode slimes. Meanwhile copper and tin are removed as dross or caustic soda scum produced at bullion melting kettles.
Refined cathodes are melted, fluxed with caustic soda, and cast for market or pumped to the lead chemical operations. In the smelting or the refining operation, antimony oxide, gold, silver, tin, tellurium, bismuth, and indium are recovered as by-products.

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The Chigirishima Smelter of Toho Zinc Co., Ltd. is located on a small island of about 90, 000m² situated in the National Park of the Inland Sea. This smelter is an independent custom lead smelter and its operation was started in 1951. At present, this smelter produces 6, 000 tons/month of electrolytic lead. The main processes are as follows:
(1) Updraft sintering (2) Blast furnace smelting (3) Bullion drossing (4) Electrolytic refining (5) Slime treatment.

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Hikoshima Smelter is situated in Hikoshima Island at the southeast end of Honshu, and faces Northern Kyushu Heavy Industrial Area which is opposite side of Kam-mon Channel.
The Smelter produced zinc by the horizontal retort process since 1915, but the Company decided to replace the horizontal retort plant by an electrolytic plant. Construction of the new electrolytic plant began in July, 1969 and production of electrolytic zinc started in November, 1970.
The new plant adopted a highly-mechanized and fully-automated system, for example. process computer control system, a stnpprng machine and automated transporting system for zinc cathodes.
Capacity of the plant is 84, 000t/y. but in recent years, unfortunately we have been forced to reduce the production rate. and now we are making efforts to lower the operation cost and save the energy through improvements as follows:
(1) Heat recovery of fluid bed roaster.
(2) Lowering the electric power consumption at the roasting, the leaching, the purification, and the electrolytic stages.
(3) Decreasing zinc dust and other reagent reauirement.
(4) Recovery of cobalt from residue at the purification stage.
(5) Feeding of melting furnace dross to the roaster.

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During the last decade, lead production at Saganoseki Smelter and Refinery was subject to the mercy of the repeated wide fluctuations in lead market.
In early 1970's, 2, 500mt a month of lead was produced at the plant by a blast furnace and an electric furnace and refined at the electrolytic tank house. The oil crisis in 1973 and the resulting sharp decrease in demand for lead obliged the smelter to suspend the blast furnace operation in 1975, and the electric furnace has since been operated mainly to treat dust collected at the copper and zinc smelter, which has a high content of lead as well as other rare metals.
The following facilities are in operation to attain an efficient lead refining operation and by-products recovery:
1. A drum machine and the preparation line for producing starting sheets
2. An anode flattening machine
3. A lead slime rotary dryer
Presently, 500mt a month of lead is produced in addition to recovery of rare metals such as indium, antimony andbi smuth.

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Miike Smelter is located in the industrial district of Ohmuta of Fukuoka prefecture, and adjoins Miike Coal Mine, one of the largest coal mines in Japan. The smelter has been treating various domestic and foreign concentrates with Miike coal since 1912. Main sources of domestic concentrate are Kamioka and Nakatatsu Mines, both of them are owned by the Company.
This consists of the following six plants: a roasting and sintering, a sulfuric acid, a vertical retort and reflux refining, a residue treatment, a lead and cadmium recovery, and a zinc sheet plant.
Miike Smelter experienced three different zinc smelting processes; the horizontal retort process, the electrolytic zinc process, and the vertical retort process, but now the vertical retort zinc smelting process only is existing.
The operation of the first four vertical retort furnaces started in 1954 and at present there are thirty-two furnaces as a whole, and total zinc producting capacity is 108, 000 tons per year.
Reflux refining process was originated in 1963 to satisfy demands for special high grade zinc. Reflux refined zinc (RMC) is mostly used to produce tailored zinc for galvanizing (GMC) and zinc oxide. Zinc oxide is produced by seef developed, process. The recent production rate of zinc oxide is 3, 000 tons per year.
Three half-shaft furnaces are operating in order to treat vertical retort briquette residue, leach residue from the electrolytic zinc plant, and other zinc bearing materials. The zinc contained in the raw materials is recovered as crude zinc oxide containing lead. The produced zinc oxide is sent to the calcination plant to eliminate lead chlorine and cadmium. Copper is recovered as low grade copper matte. Discharged slag from the furnaces is granulated by water and sold for use of portland cement manufacturing.
An electric furnace with submerged electrodes started operation in 1979 to recover lead in the lead enriched flue dust from the calcination plant and the flue dust of the electric furnace is sent to the cadmium and indium recovery plant.
The equipments of a zinc rolling mill were renewed in 1967. The annual production of zinc sheets is about 2, 000 tons per year and these zinc sheets are used for photo printing negative plates, shells of battery, and roofing materials.

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An original precious metals recovery plant at Osaka Refinery was constructed in 1944. Since then the plant ha s treated the copper electrolysis slimes delivered from the copper refineries of Mitsubishi Metal Corporation. The increase of cathode copper production by the company, however, has made it inevitable to expand the plant capacity at Osaka. Then in December, 1969, a new precious metals recovery plant was completed which has many design features different from the old plant, such as the layout of furnaces and the selenium recovery system. The new plant is one of the most advanced plants which have complete measures for environmental pollution control and high productivity.

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There exists Japan's only cyanidation plant in the mine site, which was constructed in 1914 with technology imported from U. S. A.
The ore of mine is crushed and ground to be leached in cyanic solution.
Then bullion, Au/Ag alloy, is produced finally through the method of zinc precipitation.
The plant treats also various Au/Ag scraps, which bear more bullion than that of above. The bullion is sent to Mitsui's Takehara Refinery for refining.
On the other hand, a great effort has been made for researching new methods of waste residue disposal, that is a serious problem of the mine.
Several attempts are conducted to utilize waste materials with some profit.

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Itomuka Refinery is located 37km to the west of Rubeshibe station of Sekihoku line, Hokkaido. In 1936, Itomuka mine was discovered rather accidentally by typhoon, and it became the largest mercury producer in Japan which showed its peak in 1944, when 245 metric tons of mercury was produced. But, in the 1960s, the toxic and environmental ill-effect of mercury occurred at Minamata Bay, Kyushu, aroused considerable concern. Environmental damages and the government control caused the decrease in mercury consumption, demand and price.
Therefore, Itomuka mine was closed its mining in 1974, converted its material source to mercury waste resources and now it is turning wasts materials into profitable product. The plant has six-hearth Herreshoff Furnace, an electric screw Furnace, and a rotary retort with 4000 tons per year capacity. Now, Itomuka Refinery is the sole mercury producer and mercury waste resources treatment works in Japan.

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Chuo Denki Kogyo Co. Ltd. was established for producing low cation ferromanganese in February 1934. Now our company produces some ferromanganese, electrolytic manganese, and inorganic compounds of manganese. The electrolytic manganese is produced at Taguchi Plant of Myokokogen in Niigata.
Commercial production begun in 1940 was small, of the order of 15 kg per day, and the process was gradually improved and the pilot plant expanded so that it had a monthly capacity of 300 tons in 1971.
Initially native Rhordochrosite (MnCO₃) was used as manganese source. But it was changed to calcined ore of manganese dioxide (MnO₂) in 1976. The reduction process has been originally studied to develop new sources of the metal. Use of the calcined ore has an advantage to maintain the stability of the operation.

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For some years, trials on the separation of high purity nickel and cobalt from sulfate solution by hydro-metallurgical process had been developed by Nippon Mining and a new refining plant was constructed at Hitachi Smelter and Refinery. Through this N. M. C. process, the plant has since then been operating smoothly producing approximately 3, 300 mt/y and 1, 300 mt/y of high purity nickel and cobalt, respectively.
Typical analysis of electrolytic nickel and cobalt are shown as follows. ElementNi Co Fe Cu Zn Pb
Nickel product (wt %) 99.98 0.01 0.001 0.001 0.0001 0.0001
Cobalt product (wu %) 0.02 99.98 0.002 0.001 0.0001 0.0001
The N.M.C. process can be described briefly:
1) Simple process.
2) Coherent process by handling sulfate solution from leaching to electrowinning.
3) Safety (minimal fire risk) process using high flash point of diluent solvent.
4) Low operation cost.
5) Good environment for workers.
6) Operation rate is at high level and stable actually.
7) Corrosion free at many facilities.

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Sumitomo Metal Mining Co., Ltd. is the largest producer of nickel metal in Japan. Niihama nickel refinery in Besshi Division has been producing electrolytic nickel since 1939, except for a temporary suspension after World War II. Since 1970, major part of nickel products has been produced by matte anode electrolysis. Nickel matte is imported from Australia and Indonesia. The production rate of electrolytic nickel including electrowon nickel by chloride bath is about 24, 000 tons annually. In addition, the production capacity of other nickel products such as nickel sulfate, nickel oxide, nickel chloride, is about 3, 500 tons annually in terms of nickel amount.
In 1975, a cobalt refining plant was newly constructed on the north side of the nickel refinery. The new refining process is distinctive because of its high purity of products and its hydrometallurgical feature including the solvent extraction for separation of cobalt from nickel. The raw material for the cobalt plant is the mixed sulfide of nickel and cobalt imported from Philippines. The recent cobalt products are; electrolytic cobalt: 1, 500 tons per year, cobalt oxide: 100 t/year, cobal sulfate crystal: 480 t/year, cobalt nitrate solution: 300 m³/year (Co 200 g/l). The production of cobalt chloride, cobalt acetate, etc., will start in the near future.

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Ikuno tin smelter started its operation in 1913 with the reverberatory furnace smelting process and in 1916 another plant started to recover tungsten which was contained in tin concentrates in the form of scheelite.
In 1950, the company replaced the reverberatory furnace with an electric furnace to improve operation efficiency and recovery.
The smelting process is composed of three stages, namely, concentrate smelting, slag smelting, and hard-head smelting. At present, smelter treats both tin concentrates mainly from Akenobe Mine and other tin bearing scrap materials to recover tin metal.
Annual production of crude tin metal is approximately 1, 250 metric tons and 50% of the crude metal comes from tin bearing scrap materials.
Ikuno is the only primary tin smelter in Japan.

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The tin refining plant at Naoshima Smelter began operation in 1960 treating crude tin produced at Ikuno Smelter, while the tin refining plant at Osaka Refinery was shut down.
At the present time, the plant, the only primary tin refinery in Japan, produces electrolytic tin of more than 99.995% at a capacity of 130 t/m.

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Our company, MLI, started aluminium smelting business at Naoetsu in 1963 and enlarged it to 4 potlines in 1970. Main raw materials for producing aluminium are alumina, carbon materials and fluorides. Alumina is reduced by electric power to aluminium in the molten bath of cryolite and aluminium fluoride at about 970°C. Our technoloty is ac follows:
(1) We have our own power station operated by using heavy oil. The power station is consisted of direct current generators driven by diesel type engines. This method is superior with respect to energy efficiency and facility utilization to the laree unit steam driven Hower stations.
(2) We have 100kA Soderberg cells of vertical spike type. We have improved cathode lining technique, anode manufacturing process and have developed the computer control system of cell operation. Now our operational results have approached near those of Pre-baked type cells, with DC power consumption under 14, 000 kWh/t-Al and anode paste consumption under 500 kg/t-Al. And we have achieved DC power consumption of 13, 000 kWh/t-Al in several cells.
(3) We have improved our original fluoride recovery technology to produce aluminium fluorides directly by using alumite sludge.

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Sumitomo Aluminium Smelting Co., Ltd. started producing aluminium by Prebaked anode pots of 15 kA current load at Niihama in 1936. As per the worldwide trend of the industry, Sumitomo extended the pot design to 30 kA horizontal stud Soederberg pots, which were followed by 50 kA vertical stud Soederberg pots. In 1961, a smelter was constructed at Nagoya by using 100 kA vertical stud Soederberg pots, and two smelters with same pots were built in Niihama and in Toyama.
Supported by years of experience in operation of 100 kA vertical stud Soederberg pots, Sumitomo worked hard in development of better technology. The comparative study of the intensity factor of current and the scale factor, was directed to satisfy the requirements of industry, like engergy saving, labour saving, and environmental pollution control. Curtailment of energy consumption was studied by means of i) optimum current density, ii) suppression of effect of electromagnetic force by intervenient influence between flows of electrolysis current and bus bar current, and iii) cathode construction of good heat balance. Reduction of labour requirement was dependent on process control by computer, and improvement to environmental pollution was attributable to scrubbing of both the primary pot gas and the secondary gas from the potroom building.
Outcome of Sumitomo's development works was incorporated in a 100, 000 mtpa aluminium smelter equipped with 175 kA prebaked anode pots, which was built in 1973 at Toyo City.
After being put into operation in 1975, the modern smelter is now running at full production capacity.

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Production of nickel oxide sinter 75 at Matsuzaka Plant of Tokyo Nickel was started in March, 1967 by fluid bed roasting of nickel sulfide matte imported from INCO Limited in Canada. Roasting of Canadian matte was continued until April, 1978 when it was switched over to Indonesian matte.
The Indonesian matte is produced by PT International Nickel Indonesia (PT INCO) at its Soroako Plant in the Island of Sulawesi. The project is backed up by Larona hydroelectric power plant which provides PT INCO with cheap electric power. The cheap electric power, together with mass production, is a major contribution to PT INCO to produce its product at low cost. Good quality and lower transportation cost to Japan are other advantages of Indonesian matte produced at Soroako.
At Matsuzaka Plant, production of nickel oxide sinter 75 is done in a very rationalized process which requires least energy and manpower.
Nickel oxide sinter 75 produced at Matsuzaka Plant has many advantages for special steelmaking and is shipped to special steelmakers' plants all over Japan.

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Pacific Metals Hachinohe Works commenced to be constructed in September, 1956 for the purpose of the production of sand pig iron from iron sand produced in Aomori prefecture and Hokkaido area, and was completed and began to be operated in May, 1957. We have attempted to increase the capacity of the works for producing pig iron by about two times, established a steel manufacturing plant for carrying out a continuous operation of pig iron and steel making and enlarged the scale of the works. However, being readily responsive to the change in various conditions of industries concerning this works, we enjoyed our seaside works which could handle a great deal of materials from overseas, planned to convertth e sand pig iron into ferroalloy comprising ferro-nickel and ferro-manganese, completed to change and rationalize the existing manufacturing equipment and improved its nature as a steel manufacturing plant which produced mainly stainless steel by April, 1967.
In 1969, we finished installing a 25, 000kVA large closed type electric furnace for ferro-nickel and changing an electric furnace for ferro-alloy, which had been converted from a pig iron manufacturing furnace, into a large and closed one.
In September in 1970, we installed a 40, 000kVA electric furnace for ferro-nickel which is the biggest in the world and our works has become one of the largest ferro-nickel manufacturing works in the world which has an excellent smelting technique.
Therefore, this works is a seaside works which is expected to be a main installation of the Pacific Metals Co., Ltd. and to be more developed.

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Toyama Showa Denko Co., Ltd.(TSK) is situated in the industrial area near by the Toyama port. TSK is smelting ferro-alloys such as ferro-nickel, ferro-chromium and ferro-molybdenum, and these products are mainly used for stainless steel making.
TSK had been Toyama works of Showa Denko Co., Ltd., but became the subsidiary of Showa Denko Co., Ltd. on January 22, 1979.
Since we started ferro-nickel smelting in 1969, we have had much experience about it during more than ten years.
At present, we go on smelting ferro-nickel, based on the rotary kiln-electric furnace process. The annual capacity of this process is about 4500 tons of nickel.
TSK is dependent for its raw material ores on garnierite obtained from the nickel oxide deposits in areas such as New Caledonia and Indonesia. Garnierite is a rich siliceous ore of which the nickel content varies between 2.3-2.6%. Our process is to calcine these ores in the rotary kiln and to reduce the hot materials in the electric furnace. In this paper, the outline of our smelting process, and improvements of plants are described.

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This company was founded in 1942 as Oheyama Plant of Nippon Yakin Kogyo Co., Ltd. to produce ferro-nickel from low grade nickel oxide ores of Mt. Oheyama. The smelting method at that time was something like the one known as the Krupp-Renn process, and operation continued till the end of World War II.
The plant began to run again in 1952, switching to imported ores from New Caledonia for its raw materials. The Krupp-Renn process, which we employed for treatment of nickel ores, has been modified and developed remarkably since then. Our engineering experiences and techniques stored over many years enabled us to achieve technical innovation and reformation in whole process, such as grinding and homogenization of materials, filtration, pelletizing, preheating, kiln- operation and jigging. We have now established a unique process for Fe-Ni smelting, which might be named “Nippon Yakin-Oheyama Process”.
In 1975 Oheyama Nickel Co. separated from Nippon Yakin Kogyo Co. Now monthly nickel production amounts to some 900 tons, and almost all of the products is sold to Nippon Yakin Kogyo Co. for stainless steel production.
Nippon Yakin-Oheyama Process has drawn attention to its low production cost, which is due essentially to its low consumption of expensive electricity and motive power use. The oxide ores within the rotary kiln are roasted and reduced by both fuel oil and coal. In the partially fused slae, the reduced metal particles then coalesce and grow to size of 0.5 to 30mm, which is called “Luppe”. Chemical analysis in percent; C<0.1, Si<0.1, Ni-18-22, slag<2.
Owing to its properties “Luppe” is also usef ul as coolant source for AOD process which is most important in stainless steel making.

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In 1933, Nippon Mining Co., Ltd.(N. M. C.) started the first ferro-nickel production in Japan at Saganoseki Smelter & Refinery by using an electric furnace. At that time, they smelted 75 metric tons of ore into 12 metric tons of ferro-nickel per month and produced 70 metric tons of slag.
Today, 50, 000 metric tons of ore is smelted into 5, 000 metric tons of ferro-nickel and 4, 000 metric tons of slag per month by the blast furnace process and the electric furnace process.
For 1933-1980, N. M. C. have developed many techniques and processes in ferro-nickel field such as practical use of ferro-nickel to special steel making, blast furnace process, fertilizer production from slag, and so forth, and experienced almost all of ferro-nickel smelting processes, namely, electric furnace process, blast furnace process, Krupp-Renn process and Elkem process.
Among above mentioned processes, the most effective energy saving process is the blast furnace process and Elkem process is the most pdpular one. At Saganoseki Smelter & Refinery, these two processes are making good combination and producing many kinds of ferro-nickel with about 15, 000 metric tons of contained nickel per year.

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Hyuga Smelting Co., Ltd. established by Sumitomo Metal Mining Co., Ltd. started the production of ferro-nickel at Hososhima, Miyazaki prefecture, in September 1956, which is now owned by Sumitomo Metal Mining Co., Ltd.(60%); Nippon Steel Corporation (25%); and Mitsui & Co., Ltd.(15%).
In accordance with the rapid increase of the market demands, the company made a steady growth, expanding the production capacity several times. Because the further expansion required greater productivity and broader acres, the new plant was built at the present site in the second section of Hyuga coastal industrial quarter adopting the Rotary Kiln-Electric Furnace process, in 1968.
Since the improvement of the process, the development of low grade ore treatment technology, the development of new products and the energy curtailment of the whole plant have been achieved, Hyuga Smelter has become one of the most advanced coastal ferro-nickel smelters, boasting of most modern facilities and incompetitive technical knowledge.

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The Tomakomai Plant of Tomakomai Chemical Company, Limited, produces sulfuric acid and iron pellets by treating pyrites mined from metal mines in Hokkaido and Tohoku regions and at the same time recovers such valuable metals as gold, silver, copper, lead and zinc contained in pyrites-an integrated plant of processing pyrites.
Construction of the Tomakomai Plant was started in June 1971 and the operation was commenced in August 1972. The plant consists of four main sections, i.e., pyrite roasting, acid production, pellet production and by-products recovering.
The pyrite roasting section is composed of two steps of roasting preroasting and postoxidizing-by which sufficient elimination of impurities is attained.
The acid production section recovers sulfur at high recovery rate by a dpuble contact type converter.
At pellet production section, the chlorinating volatilization process is adopted for producing iron pellets of low impurities and excellent physical properties fully meeting the requirements of ironworks in Japan.
The valuable metals volatilized by the chlorination are collected by a gas treating system and recovered by liquid treating units.
For the past eight years since the commencement of operation, the Company has been paying tenacious efforts to develop and establish the technology of effective and efficient treatment of pyrites, and the plant operation has been successful in achieving the original technical targets.

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Onahama plant of Ryoho Recycle Company employs the electrothermic process for producing marketable zinc oxide from steelmaking dusts.
Ryoho Recycle Company has operated a zinc oxide plant in Onahama since 1974, the location being at about 200 kms north-northeast of Tokyo. The plant treats 50, 000 tons of steelmaking dusts to produce 15, 000 tons of zinc oxide per year.
The process includes 1) rotary kiln, 2) crashing, 3) washing, 4) pre-mixing, 5) sintering, and 6) furnacing to produce zinc oxide. All of facilities are operated automatically by a central control room.

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Sotetsu Metal Co., Ltd., which was established by the investment of Nisso Smelting Co., Ltd. and electric-furnace steel making companies, started operation of Waelz plant in 1975, to recover zinc and lead values from electric furnace steel makine dusts. Our plant data together with results of five vear's operation are described in this paper.
Our kiln size is 3.2-3.5 meters in shell diameter with 52 meters length. Typically, 18, 000 tons of Waelz oxide are produced from about 50, 000 tons of pelletized dusts fed into the kiln annually. The resulting crude zinc oxide is transported to Nisso Smelting Co.(Aizu Smelter) for further treatment.

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In 1969 at Amagasaki Plant of Dowa Seiko, we completed the construction of the chloride volatilization plant which could produce iron oxide pellets of 28, 000t/m with recovery of non-ferrous metals such as Cu, Pb, Zn, Au and Ag from contaminated pyrite cinder used as the raw material. And we have continued the operation for about ten years since then.
Meanwhile, in the field of the sulphuric acid production, there has been a remarkable change in the situation of raw materials. Therefore pyrite cinder entering Amagasaki Plant decreased year by year, and at present the plant is forced to run at one fourth of the full capacity.
In order to keep the production level of Cu and Zn, however, various kinds of industrial waste containing Cu and Zn (sludge and solution) have been treated for the purpose of recovering them. So that at present more than 80% of Cu and Zn products come from that industrial waste. And at the same time dirty pickled liquor of steel (FeC1₂ solution containing Pb and Zn), which is collected from the small mills making wires and nails, etc., in the surrounding area, is decomposed with hot air by the conversion of discarded plastic, and recovered dilute HC1 solution (about 10%) is served to leach metals in sludge in stead of acid produced from the chloride volatilization plant.
As mentioned above, the chloride volatilization plant, in which the pellets production is cut back by the decrease of raw material, can produce even more metal products than at the full operation.
Thus we contribute to, the recycle of the pregnant resources and to solve the environmental problems in this district.

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