As pyrometallurgical technologies to smelt nickel metal from the oxide ore, melting reduction process using an electric furnace (Elkem) and semi-melting reduction process using a rotary kiln (Krupp-Renn) with a saprolite ore as a raw material have been established and operated commercially. However, in the future, it is expected that it will be difficult to smelt nickel from the oxide ore because of the decline of nickel grade in the ore and it is necessary to develop a new process adaptable to lower grade ore and difficult processing ore.

The authors have conducted fundamental research on the pyrometallurgical reaction of low grade and difficult processing nickel oxide ore smelting by the rotary hearth furnace (RHF). Liquefied gas burner will be supposed from points of cost, reduction of global warming gas and so on in the operation of Ni smelting. On the other hand, it is getting clearer that Fe and Ni metallization degree in liquefied gas burning atmosphere are lower than those in N₂ atmosphere. The reason have been guessed effects of H₂O generating in liquefied gas combustion. The results about effects of H₂O to reduction reaction of low Nickel grade oxide ore is described in this report.

EICP (Enzyme Induced Calcite Precipitation), which artificially precipitates calcium carbonate using urease purified from enzymes found in leguminous plants, is attracting attention as a ground improvement method with low environmental impact. Many mechanical and permeability tests have been conducted on treated soil modified by the EICP technique, but there is a need for a technique that enables microscopic observation of the calcium carbonate precipitation process. In this study, we injected a grouting solution into a microfluidic chip using the EICP technique, and observed the precipitation process of calcium carbonate to examine the precipitation mechanisms in the pores. The area of precipitated crystals was quantitatively evaluated by using image analysis software. In addition, we developed a device that can measure the differential pressure before and after the chip and the flow rate of permeate water, and conducted permeability experiments to investigate the water sealing effect of grout injection on a micro scale. As a result, the precipitation of calcium carbonate crystals by grout injection was confirmed. The change in porosity was quantitatively evaluated by the image analysis, and the qualitative change of permeability was understood.