Lead in various wastes is thought to cause serious pollution when the wastes are discarded in the environment. Therefore, its elution behavior from various kinds of ashes has so far been investigated. Here, mixing various wastes at optimum ratio is expected to result in the inhibition of its elution. In the present study, first, elution behavior of lead, artificially added to the mixture of coal ash, municipal waste ash and flue gas desulfurization sludge was investigated by varying added amount of lead and mixing ratio. Remarkable inhibition effects by addition of flue gas desulfurization sludge to the mixture of the coal ash and municipal waste ash were found on the elution of lead. Second, the mechanism of the inhibition effects of lead was discussed by considering the effects of co-existing anions in the leachate. Chemical species of lead eluted were estimated by the stability of various lead complexes formed and their solubility products. It was suggested that lead carbonate formed by the reaction between lead ion produced from lead chloride added and carbonate ion eluted from the desulfurization sludge suppressed the elution of lead. Finally, the contribution of formation of ettringite or similar minerals during the curing process to the lead elution was discussed from the results on the effects of coal ash to municipal waste ash ratio on its elution.
The efficiency of energy usage of a district heating and cooling plant using sewage water as heat source and sink, was evaluated by investigating the data of the district heat demand and energy supply to the plant, which were collected at the Koraku -1 Chome plant in Tokyo central region. Through analyzing these data, it was clarified that the overall COPs of the plant were 3.17 for cooling and 2.65 for heating. COP was then compared with that of another plant using air as heat source and sink. The overall COPs of this plant which were calculated according to the atmospheric temperature, were 2.54 for cooling in summer and 2.28 for heating in winter. The differences in COPs were due to the temperature differences between sewage water and air. As a result for COP differences, the district heating and cooling plant using sewage water could be more energy saving, up to 20% for cooling in summer and 14% for heating in winter, compared with the counterpart plant that uses air as heat source and sink.
Carbonization of powderd larch wood and bark, with diameter of 0.18-0.50mm, followed by steam activation was made in a batchwise fluidized bed reactor for the production of activated carbon as their advanced use. It is found that carbonization at 773K was optimum in term of specific surface area for activated carbon. In the subsequent steam activation of chars conducted at 1023, 1073 and 1173K for 0.5-3.0h, higher temperature and longer time gave larger surface area at the cost of the yield. This indicated a close relation between surface area and yield for activated carbons obtained. An activated larch wood char had the surface area of 1, 500m2/g as the maximum, and this value was equal or superior to those of activated carbons from fir wood, quercus wood and coconut shell. Larch bark char after activation also was almost equal to coalderived commercial activated carbons in the surface area. These results showed a promising aspect of conversion of the whole larch into activated carbon as higher value added product compared to the conventional use as packing and palette materials.