Leached test was used to evaluate the safety of the ferrite sludge formed by the heat treatment after conventional or two-step treatment with pH adjustment of wastewater. Simultaneously, the concentrations of Cd and Fe ions in the treated water were measured before the leached test. The effect of the heat treatment on the concentrations of Cd (CCd) and Fe (CFe) in the elute was discussed by comparing the ferrite sludge formed without heat treatment. The CCd of ferrite sludge formed by the heat treatment with the two-step treatment was remarkably lower than that by conventional or two-step treatments in relation to Cd(OH)2 on the surface of ferrite particles. XPS measurement of the sludge formed by conventional and two-step treatments indicated the existence of Cd(OH)2 on the surface of ferrite particles. XPS measurement of the sludge formed by the heat treatment indicated no existence of Cd(OH)2 on the surface of ferrite particles. The measurement after Xe+ sputtering showed that the Cd(OH)2 is absent not only on the surface but also in the bulk of the particles formed by heat treatment. The heat treatment after two-step treatment stabilizes the sludge and is favorable for steady operation of the ferrite process, industrial utilization of the sludge and good quality of the treated water.
Recently, the increase in production, consumption causes the shortage of the natural resources and the increase in waste disposal. In order to build up a sustainable society, the input and the output of the natural system should be reduced by the recirculation of materials and energy. We have tried to develop a recycling technology of inorganic wastes using the hydrothermal processing. The starting materials were the incinerated ash from sewage sludge and construction sludge. Ca(OH)2 was added to waste. The mixtures were formed and autoclaved at 180°C under saturated steam pressure. The flexural strength of the specimens varied from 3.2 to 16.2 MPa. These solidified inorganic waste have good performance of humidity control. Numerical simulation method based on heat and moisture transfer model was studied to estimate performance of hydrothermally solidified inorganic waste. Numerical model was calculated by the relative humidity changes in the physical space with temperature changes. Simulation result was compared with experimental measurement. Simulated values by calculating with non linear material property were in good agreement with experimental measurements.
Two-step liquid-liquid extraction methods using aqueous and organic phases for separation of red (Y2O3: Eu3+), blue (BaMgAl10O17: Eu2+) and green (CeMgAl10O17: Tb3+) fine fluorescent powders were proposed in this paper. At first, the blue powder was extracted selectively into heptane phase using a chelating agent, 2-thenoyltrifluoroacetone (HTTA, CF3COCH2COC4H3S) under alkaline pH condition. Then, chloroform was used for extracting the green powder into the chloroform phase. The red powder separating from the green powder remained in aqueous phase with a depressant, potassium sodium tartrate tetrahydrate (PST, KNaC4H4O6·4H2O). The powders could be well separated in terms of their grade and recovery. The results suggested directions for future research into the recycling of fluorescent powders from fluorescent lights.
In Japan, large quantities of pesticides are stockpiled in many locations. The Japanese government aspires that these pesticides should be regulated by treating them as per the regulations of the Stockholm Convention which came into effect from the year 2004, controlling twelve persistent organic pollutants (POPs). Therefore, it has become mandatory to develop technologies that can effectively destroy these stockpiled pesticides safely and effectively. Having this in mind, in this study, the removal and elimination efficiency of DDTs, aldrin and BHC (HCHs) was investigated heating mixed samples of these pesticides in a tubular furnace coupled with a secondary combustion chamber, in presence of air or nitrogen. We observed no difference in the volatilization temperatures of these pesticides when the samples were heat-treated either under nitrogen or air. When the sample was heated to 600°C under a nitrogen atmosphere, an increase in the ratio of DDE in total DDTs was observed. About 90% of the aldrin was destroyed. BHC was volatilized almost completely at this temperature but did not disintegrate at all. A high removal rate was observed for all the chemicals when the flue gas from the tubular furnace was heated to 1,100°C in the secondary combustion chamber. However, the volatilization rate of BHC (HCHs) decreased when the oxygen concentration in the secondary combustion chamber was lowered. This study proves the effectiveness of a system designed to vaporize pesticides through heating in a furnace at high temperature followed by combustion of the flue gas.
Development of the integrated gasification combined cycle power generation of various gasifying methods has been preceded in the world. The gasified fuels are chiefly characterized by the gasifying agents and the synthetic gas clean-up method, and divided roughly into four types. The calorific value of gasified fuel differs according to the type of gasification agents. On the other hand, to improve the thermal efficiency, it is necessary to use a hot/dry type synthetic gas clean-up, but ammonia originated from nitrogenous compounds in coal is not removed. And then it forms fuel-NOx. For these reasons, the combustion technology for each gasified fuel is important. In this paper, I review development of the gas turbine combustors for the gasified fuels of three types through numerical analyses, experiments using a small burner and the designed combustors.
In 2003, 2.16 million tons of polyvinyl chloride (PVC) have been produced in Japan, i.e. the third large proportion of plastic production. However, only 20% of PVC wastes have been recycled, while the rest was disposed or incinerated. In order to improve the PVC recycling rate, a two-stage separation process that combines the triboelectric separation and the air tabling has been designed. The developed process is able to sort PVC from other types of plastics. The efficiency of the process was investigated for two three-component plastic mixtures, i.e. (1) ABS (acrylonitrile-butadiene-styrene), PP (polypropylene) and PVC, which are used in production of home electric appliances or automobiles; and (2) PET (polyethylene terephthalate), PP and PVC, which are utilized in production of plastic containers or everyday products. In order to sort the ABS-PP-PVC mixture, the triboelectric separator was employed in the first stage of process to collect the ABS flakes as positively charged fraction. The negatively charged fraction of PP and PVC was then separated by means of the air table by taking advantages of differences in density. Hence, at the end of the process, the collected PVC fraction had a grade and a recovery of 90.2% and 78.0%, respectively. Regarding the separation of the PET-PP-PVC mixture, the air table was used in the first stage to collect the PP flakes as a low-density fraction. Then, the triboelectric separator was employed in the second stage to recover 89.0% of PVC with a grade of 93.7%.