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Laterite ore at the Ramu mine contains 48% Fe, most of which is in goethite, and 1% Ni, 0.1% Co, 1.8% Al, 0.14% Mg, and 0.8% Mn. Laboratory studies have been carried out to evaluate the effects of slurry temperature, leaching time and sulphuric acid (H2SO4) concentration on nickel and cobalt extraction. Results showed that at normal atmospheric pressure, over 99% of Ni and over 50% Co were extracted into solution within 120 minutes at 95 degrees C in 2M H2SO4 solution. Similar results were obtained when the temperature was reduced to 90 degrees C, but the Co extraction increased to over 70% when leaching time was increased to 240 minutes. Further reduction in temperature to 80 and 60 degrees C resulted in a reduction of Ni and Co extraction. At the end of each leaching test, magnetite was seen to attach to the magnetic stirrer. The study showed that nickel can be completely leached into solution but cobalt only up to 70%., Laterite ore at the Ramu mine contains 48% Fe, most of which is in goethite, and 1% Ni, 0.1% Co, 1.8% Al, 0.14% Mg, and 0.8% Mn. Laboratory studies have been carried out to evaluate the effects of slurry temperature, leaching time and sulphuric acid (H2SO4) concentration on nickel and cobalt extraction. Results showed that at normal atmospheric pressure, over 99% of Ni and over 50% Co were extracted into solution within 120 minutes at 95 degrees C in 2M H2SO4 solution. Similar results were obtained when the temperature was reduced to 90 degrees C, but the Co extraction increased to over 70% when leaching time was increased to 240 minutes. Further reduction in temperature to 80 and 60 degrees C resulted in a reduction of Ni and Co extraction. At the end of each leaching test, magnetite was seen to attach to the magnetic stirrer. The study showed that nickel can be completely leached into solution but cobalt only up to 70%.

Mine ventilation measurements were carried out using SF6 as tracer gas at the Kushiro coal mine in Japan, to investigate the flows in the inclined airway and the network flows from the inlet portals to the main fan. A photo-acoustic SF6 gas monitor with a high sensitivity of 10 ppb gas concentration was used to determine gas concentration/time curves. The effective gas diffusion coefficient in the single mine airway was investigated using measurements and numerical simulation results and determined to be 20 m2/s, almost the same order as that obtained from Taylor's equation. However, the effective diffusion coefficient in the mine ventilation network was 200 m2/s, an order of magnitude larger than Taylor's value. A possible mechanism is presented for the large effective diffusion coefficient and delay in gas flow in the airways, involving weak re-circulated flows formed in dead spaces and roads connecting main airways without airflows. A revised equation and numerical method for finding gas concentration/time curves is also presented, based on an extension of Taylor's equation to evaluate the effective diffusion coefficient of a single-flow channel., Mine ventilation measurements were carried out using SF6 as tracer gas at the Kushiro coal mine in Japan, to investigate the flows in the inclined airway and the network flows from the inlet portals to the main fan. A photo-acoustic SF6 gas monitor with a high sensitivity of 10 ppb gas concentration was used to determine gas concentration/time curves. The effective gas diffusion coefficient in the single mine airway was investigated using measurements and numerical simulation results and determined to be 20 m2/s, almost the same order as that obtained from Taylor's equation. However, the effective diffusion coefficient in the mine ventilation network was 200 m2/s, an order of magnitude larger than Taylor's value. A possible mechanism is presented for the large effective diffusion coefficient and delay in gas flow in the airways, involving weak re-circulated flows formed in dead spaces and roads connecting main airways without airflows. A revised equation and numerical method for finding gas concentration/time curves is also presented, based on an extension of Taylor's equation to evaluate the effective diffusion coefficient of a single-flow channel.