Dysprosium, one of the various rare earth elements, is mainly used in permanent magnets to increase the strength of magnet at high temperatures. Therefore, the use of dysprosium-doped permanent magnets is preferred in hybrid and electric vehicles and direct-drive wind turbines. Instabilities in supply and demand of dysprosium by Chinese resource policy sometimes induce social crises, because the reserves and production of dysprosium is extremely uneven distributed in China. However, as a result of recent exploration efforts, some dysprosium ore deposits in alkaline igneous rocks have been discovered outside China. The total quantity of the deposits is adequate to fulfill the dysprosium demand in the future. But, unfortunately these deposits contain a small amount of radioactive element thorium, that is hampering the development of the deposits. A new idea to develop the dysprosium ore bodies using paste backfill mining is discussed. Outline of this mining project is shown. Rare earth elements including dysprosium are recovered by conventional methods first. Thorium-rich precipitate produced in the process of smelting is then mixed with the waste coming out mining and mineral processing and a small amount of cement. The mixtures are backfilled to the original mine site. It is deduced that the solidified mixtures containing lower thorium than the ore provide a stable reducing environment of thorium and have a sufficient strength.
The paper sludge which is generated during paper manufacturing processes is incinerated to reduce its volume, and then the paper sludge ash is produced. The greater part of the paper sludge ash has been disposed to landfills and an effective utilization of the paper sludge ash has not been promoted. From view point of the effective utilization of industrial wastes, the authors have proposed that the granulated materials made of the paper sludge ash are used for concrete aggregate and evaluated the applicability of paper sludge ash to concrete. The concrete using the granulated paper sludge ash is lighter, and its water absorption is much higher than those of ordinary concretes. The drying shrinkage strain is larger than that of ordinary concretes. The lightweight precast materials used for such as forms have a merit of the cost reduction of transportation and construction. In this study, the applicability of the mortar using granulated paper sludge ash for aggregate (PS mortar) to precast lining form is examined. Firstly, the flowability and the strength of the PS mortar are examined and the curing performance of the PS mortar form is indirectly evaluated by measuring strength and air tightness of back filling concrete. Secondly, the drying shrinkage of the PS mortar is measured and its prediction equation is proposed. Finally, Practicality of the PS mortar to precast materials is evaluated by observing deformation and crack occurring of the precast PS mortar walls constructed tentatively in this study. From results of the above examinations, it is found that the PS mortar form has a high curing performance. However, the PS mortar may not be unconditionally utilized because its drying shrinkage strain is relatively large.
In the present study, a drilling test using a 66-mm-diamter high-speed (HS) percussion bit was first carried out to investigate the rock drillability of Sori granite, which has a uniaxial compressive strength of about 220 MPa. Durability tests were then performed with Sori granite using two HS bits in order to investigate the effect of the bit weight on the amount of bit wear. Based on the results of the drillability tests, bit weights of about 6 kN and 13 kN were selected. The main results obtained from the durability tests are as follows: a. The penetration rate of both bits decreased linearly with increasing drilled length. On the other hand, the specific energy increased almost linearly with drilled length. b. Both bits almost reached the bit-life at the drilled length of about 30 m. A detailed analysis revealed that, for both bits, the torque increased linearly with drilled length, with the final torque at 30 m being about 0.11 and 0.13 kN-m higher than the initial. c. For both bits, the height-loss of gauge tips was almost identical and increased linearly with drilled length. e. For both bits, a one-to-one correspondence was found between the increase in torque and the height-loss of gauge tips. This revealed that the torque is a quantitative indicator of bit wear, regardless of the bit weight. Finally, to investigate the effect of changing the rock strength, a drilling test was conducted using a new HS bit with Shinkomatsu andesite, which has a uniaxial compressive strength of 192 MPa. The one-to-one correspondence mentioned above was observed as well.
This paper describes the possibility of concentrating minor rare metals contained in cellular phones by applying a novel comminution and the combination of physical separation technologies, which were followed by metallurgical processes to extract them. We compared two kinds of comminution processes, conventional and novel, from the viewpoint of compositional separation and combined two kinds of physical separation categories, “Device Separation” and “Powder Separation” to achieve an effective concentration of rare metals. It was demonstrated that the novel comminution process could separate printed circuit board (PCB) from the body in the first stage and detach the installed electronic devices from the board in the second stage and that several kinds of rare metals could be concentrated by combining the novel comminution and “Device/Powder Separation”. The “Device” and “Powder” products concentrated are expected to be further treated by hydrometallurgical processes to extract rare metals and/or stocked as “Artificial Deposits” in accordance with the concept of “RtoS (Reserve to Stock)”.
Catalysts are widely used in petroleum refining and chemical industries. Hydrodesulphurization (HDS) catalysts account for about one third of the total worldwide catalyst consumption. Spent HDS catalysts contain rare metals such as molybdenum, vanadium, nickel and cobalt on an alumina carrier. Among secondary resources, spent HDS catalysts are regarded the most important catalysts for recycling these metals due to not only their large amounts and economic values, but also the environmental concerns if disposed of. In most cases, spent catalysts are treated with hydrometallurgical leaching processes such as caustic leaching and acid leaching with roasting as a pre-treatment step. In the alkaline leaching processes, most of the molybdenum and vanadium are selectively leached over aluminum, nickel and cobalt. In the present study, tri-n-octylamine (TOA) was used to investigate the separation of molybdenum and vanadium from a synthetic alkaline leach solution of spent HDS catalysts with a two stage process based on solvent extraction and precipitation stripping. Molybdenum and vanadium are simultaneously extracted at around pH 4 followed by stripping of molybdenum and vanadium with ammonium salt solutions. In the stripping process, vanadium is precipitated as ammonium salts containing tetraammonium disodium decavanadate decahydrate at pH>8. The precipitation stripping efficiency was in the order of ammonium chloride > ammonium nitrate > ammonium acetate > ammonium sulfate. Meanwhile, molybdenum exists in the form of ionic species in the stripping solution at pH>8. Therefore, the separation of molybdenum and vanadium from alkaline leach solutions based on a two stage process of solvent extraction with TOA and precipitation stripping with ammonium salt can be achieved.
A boomheader, also called roadheader, was patented in the late 1940s in Hungary and the machines were developed and manufactured in various countries such as Soviet Union, England and Austria. In 1961, PK3 made in Soviet Union was introduced to a Japanese coal mine. Thereafter, the machines were developed and manufactured mainly by two Japanese companies. Currently, the machines are widely used in tunneling both for mining and civil engineering projects. In this document, the development history of the machine up to now in Japan is shortly reviewed with a chronological table.