In Chile, which is a mining country, based on our company’s original technology, we have opened the Atacama Mine, a copper mine, in which our company owns a 60% majority share, and are conducting operations based on our own initiative. The Atacama Mine is located about 16 kilometers SSE of Copiapo, the capital city of the Third Region in the Republic of Chile, at an elevation above sea level of approx. 500 meters. We began investigations in 1990, starting basically from scratch with almost no existing data, and found and confirmed ore deposits that could be economically mined. In 1999 we founded a joint venture company and began mine construction in 2001. At the time, the price of copper was low, so our main propositions were to reduce development costs, and shorten the development period, which we successfully completed by the end of 2002, achieving a short development period of a year and a half. Our development of the Atacama Mine had the following technological features: i) Because the ore body was deep underground (approx. 400 meters from the surface), we placed the primary ore reduction equipment underground, and used three long belt conveyors (3,500 m total) to transport the ore to the surface. This allowed us to reduce operation costs, and realize a safe and comfortable underground environment. ii) Slime is transported to a mine residue dam 16 km from the dressing plant via a fluid transport system using a pipeline, which has allowed us to reduce transport costs. iii) By using a new type of flotation machine we have been able to maximize the extraction rate of shipping ore (recovery rate of 93% or more). Four years after beginning operations the Atacama Mine continues to operate stably.
Mitsubishi Materials Corporation established the brand-new recycling system at Naoshima Smelter and Refinery (NSR) by constructing two recycling plants; the incinerating and melting plant for the waste and the washing treatment plant for fly ash. In these plants, input materials, which used to be buried at landfills, are pre-treated to be processed in the copper smelting & refining plant. The project proceeded against the background of Teshima incident, the worst illegal dumping of the industrial waste in Japan. In settling the arbitration between residents in Teshima island and Kagawa prefecture, the prefecture proposed construction of the intermediate treatment plant for the Teshima waste in Naoshima, taking advantage of the facilities and technologies of NSR. In 2001, the town of Naoshima drew up an “Eco-Island Naoshima plan” in cooperation with Kagawa prefecture. It was approved as an eco-town plan by the Ministry of the Environment and the Ministry of Economy, Trade and Industry. Two recycling plants in NSR as well as the intermediate treatment plant for Teshima industrial waste by Kagawa prefecture were built in Naosihma based on the plan. Since the establishment in 1917, NSR has accumulated comprehensive and reliable technology in the field of extractive metallurgy. The employed “Mitsubishi Continuous Copper Smelting and Converting Process” is compact, labor-saving and energy-saving in comparison with other conventional processes. The technologies can be applied to recycling of the industrial waste such as shredder residue and fly ash. However, the industrial waste has various form and size, containing more chlorine. Higher combustion heat of the waste causes some troubles in a boiler. Therefore pre-treatment facilities are necessary. The combination of the new pre-treatment lines with the existing copper process line has created a highly efficient and environmentally friendly system for recycling of valuable metals that previously used to be sent to a landfill.
Methane hydrate (MH) is one of the potential resources of natural gas in the near future, because it exists in marine sediments or in permafrost regions worldwide. Some extraction methods of MH from the reservoir have been proposed, such as depressurization, thermal stimulation and inhibitor injection. These are all based on the in-situ dissociation process of MH that is transformed into methane gas and water. However, There are some technical and economical problems for operation of these methods. Therefore, we have proposed a new enhanced gas recovery method by nitrogen injection. Nitrogen has the effect as an inhibitor as well as methanol and salts to shift an equilibrium condition of hydrate to high-temperature and low-pressure. In addition, we supposed some advantages for this process compared with conventional ones, such as 1) utilization of inexpensive and high permeable nitrogen, 2) retention of pore pressure to avoid compaction of sediments due to increase of effective stress expected in depressurization process. In this study, to clarify the physical phenomena in the reservoir and gas production behavior during nitrogen injection process, we have carried out the experimental study. The core holder type apparatus to enable observation of temperature change during MH dissociation was developed. Using this apparatus, some experiments for MH dissociation by nitrogen injection were conducted changing nitrogen injection rate as an experimental parameter. From the experimental observations, it was found that dissociation zone extended to the downstream zone of the sand column with time depending on dissociation rate and injection rate. Furthermore, we obtained high dissociated gas production rate in the case of high injection rate due to the multiple effect such as enhancement of dissociation and displacement of methane by nitrogen migration in pore space.
The objective of this study is to promote the understanding of structural evolution of fractures, which affects the transport of contaminants, in geological media. In this study, we grew highly soluble potassium alum as an analogue material in an open fracture with a solvent transported by advection along the fracture in order to observe decreases in aperture of the fracture. In addition, we determined experimentally the growth rate law of K-alum based on relationship between relative supersaturation and linear flow velocity. We compared our sealing result with simulations based on a simplified numerical model with our growth rate law, and found that the time necessary for sealing time on simulation result was longer than that on the sealing result. This discrepancy was explained by additive growth rate of original seed crystal and secondary crystals nucleated near the fixed seed. Thus, we showed that primary and/or secondary nucleation is an additional factor to predict the structural evolution of fractures in geological media.
Selective extractions of gold chloro complex from the chlorine leach liquor of copper anode slime with dibutyl carbitol and selective reduction of gold in the organic phase with oxalic acid were investigated. The reduction process is the most important step for the impurities removal in gold. In the reaction, since the stability of chloro complex of silver and platinum group metals increases with chloride ion, reductions of these ions are controlled. Hydronium ion generated in the reaction is effectively neutralized by hydrolysis of urea without local increase in pH value and local decrease in ORP (Oxidation Reduction Potential). In the result, co-precipitations of most impurities (Ag, Se, Sn, Sb, Pt, Pd, Fe) in the gold powder were suppressed.
For recovery of gold from wastes of electronic products, it is necessary to concentrate Au(III) complex ions from solution and to reduce them to elemental Au (Au(0)). To develop the recovery system, the coprecipitation of Au(III) complex ions with iron(III) hydroxide as a concentration procedure and their spontaneous reduction to elemental gold (Au(0)) were investigated as a function of iron concentration, pH and electrolyte concentration at ambient temperature. Most of the Au(III) complex ions were coprecipitated with iron(III) hydroxide around neutral pH, at low Cl concentration and even at low iron concentration. Under the condition, the coprecipitated Au(III) complex ions were spontaneously reduced to Au(0) even in the absence of a specific reducing agent, and 1 - 5 μm gold particles in size were formed. Finally this method was applied to recover gold from electronic devices of cellular phone.
Milling of cellulosic woody biomass as preprocessing is one of the key technologies for an ethanol production by an enzymatic hydrolysis process. Generally a mechanical mill is used for grinding of woody biomass. However, because the efficiency of the normal vibratory ball mill is low, it is not suitable for grinding of woody biomass. Therefore, the most suitable condition of woody biomass for ethanol production is needed to develop the mill system. The purpose of this research is to get the optimum condition for the high enzymatic hydrolysis by the normal vibratory ball mill. As a result, it was clarified that average particle size of 20 ∼ 30 μm and cellulose crystallinity index of 8 ∼ 12 % is the optimum condition for the high enzymatic hydrolysis. In a commercial scale, the development of the mill system to achieve those conditions in a short time is necessary, and it became clear that the application of a special-rod mill or super-high-speed ball mill would be effective for commercial ethanol production.