In a series of studies on regeneration and cleaning of gypsum produced from flue gas desulfurization, change in chemical form of calcium and release behavior of mercury during reduction of gypsum with solid carbon were investigated. Calcium sulfate dihydrate as a model compound for gypsum was mixed with solid carbon and heated to a terminal temperature of 1100 °C under a nitrogen stream. CaS was produced by the reduction of CaSO4 with carbon. CaO formed drastically above 900 °C via a reaction of CaSO4 and CaS. An optimum amount of solid carbon to CaSO4 was determined for the production of CaO. To remove mercury from FGD gypsum during the carbon reduction, release behavior of mercury from gypsum was investigated. Model compounds were prepared by addition of reagents of HgCl2, HgO and HgSO4 to calcium sulfate dihydrates. HgCl2 in gypsum was released as Hg via HgO during heating in a nitrogen stream. HgO and HgSO4 changed to elemental Hg and volatilized. Carbon addition accelerated the release of every mercury compounds to gas phase as elemental Hg from the matrix of gypsum.
Increasing attention has been paid to geothermal power generation in particularly after The Great East Japan Earthquake. However, up till now, socio-economic impacts of geothermal power generation have not been thoroughly analyzed in Japan. The objective of the present study is to analyze employment created over the entire life cycle of geothermal power generation (i.e. resource survey, equipment production, plant construction, operation and maintenance), and clarify the characteristics compared to wind and solar photovoltaic power generation. An extended input-output table, which was constructed by disaggregating the existing sectors of the 2005 Input-Output Table for Japan, was developed and used for the analysis. Employment created over the life cycle of geothermal power generation was estimated to be 0.81 person-year per GWh. Employment at the operation and maintenance stage accounted for 65% of the total employment. That is, geothermal power generation can constantly produce employment over the life cycle, which is a different characteristic from wind and solar photovoltaic power generation. Other interesting characteristic is that more employment is produced in service industry sectors such as Repair of machine, Wholesale trade, Other business services than in manufacturing and construction industry sectors.