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( Michiyo Kobori ),( Yasumasa Tojo ),( Takayuki Matsuo ),( Toshihiko Matsuto ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1
In past studies, it was reported that most of cesium (Cs) remained in the bottom ash and it became less soluble form when sewage sludge containing Cs was incinerated. Besides, from the thermodynamic equilibrium calculation, it was pointed out that Cs-aluminosilicate formed from Si, Al, etc. contained in sewage sludge under high temperature condition and this was the reason why Cs became less soluble. However, there is no study actually confirming the existence form of cesium in bottom ash of sewage sludge. If mechanism by which Cs becomes less soluble during the incineration process of sewage sludge is clarified, it can be applied for the treatment of decontamination waste that is still generating now. Therefore, in this research, the following two objectives were set; 1) to elucidate mechanism that Cs in sewage sludge becomes less soluble during incineration process; 2) to examine the possibility of Cs becoming less soluble by co-combustion of both Cs-containing waste and sewage sludge. In order to confirm the mechanism by which cesium becomes less soluble in the incineration process, Cs2CO3 and sewage sludge were heated together at 900℃ for 2 hours, and the ash for observation was obtained. By the elemental composition analysis using XRF, it was found that Fe, Si, Al, P, Sr were major elements contained in the ash. Based on the mass balance on Cs, about 75% of Cs remained in the ash and it became less soluble form. Subsequently, several thin section samples of the ash particle were created and they were analyzed by Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and Electron Probe Micro Analyzer (EPMA). Mapping of Cs using EPMA or SEM-EDS revealed that Cs presented inside the ash particles. However, there was no tendency that the specific element was particularly high at the region where Cs existed. At last, to confirm the applicability of this capturing mechanism to MSW fly ash containing Cs, CsCl and sewage sludge were heated together. This is because Cs contained in fly ash was mainly chloride and it is well known that CsCl is highly volatile and easily soluble. Even when Cs2CO3 was changed to CsCl, the amount of Cs remained in the ash after heating and the proportion of less soluble form were almost the same. In other words, it can be said that the sewage sludge can suppress volatilization of Cs during incineration and capture it inside the ash particle as less soluble form.
( Akihito Nakamine ),( Toshihiko Matsuto ),( Takayuki Matsuo ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 심포지움 Vol.2018 No.1
In Japan, there are many ash melting process and gasification melting system are working. Because of high transfer rate of precious metal such as Au, molten metals can be considered as metal resources. In this study, potential as metal resources of molten metals from various types of gasification melting and ash melting facilities was investigated. The questionnaire survey was conducted to all ash melting system and so-called shaft-type gasification system, which produce metals, and sampling was requested. Because precious and rare metal are used in home appliances, collection activity of small electric appliances were investigated. As a result, metal and slag samples were provided from 28 facilities (27.7%). Sample for analysis were taken by c one -quartering method, and it was crushed with a hammer. After digested in HF and aqua regia. Au, Pt, Pd were analyzed by ICP mass spectrometry. Cu was analyzed by ICP emission spectrometry. Si, Ca, Fe were analyzed by XRF. Metal resource potential was evaluated by Total material requirement (TMR), which is the total weight of mass which are moved when the material is mined. The rarer the metal is, the higher TMR per unit weight. Concentration in metal of Au, Pt, Pd is shown in Fig 1, in which Group 1 is electric ash melting furnaces, Group2 is fuel type ash melting furnaces and a DC electric resistance type ash melting furnace, Group3 is coke bed type gasification melting furnaces, and Group4 is oxygen type gasification melting furnaces. Figl shows that concentrations of metals in Group 3 are smaller than in other groups. The different level of concentration could be explained by dilution effect of major constituents shown in Fig.2, which is estimated by multiplying Si, Ca, Fe concentration in metal with weight percentage of metal among all outputs. The transfer rate Si and Ca in Group3 is the highest, and Group 2 show high Fe transfer rate to metal. Ca is derived from slaked lime supplied in the furnace in Group 3, but source of Si is not known yet. Fig.3 shows the estimated TMR which is almost the same tendency as in Fig. 1. Group2 shows the highest TMR, which followed by Group 1 and Group3. There are large variations in Group4. Total amount of metals in all outputs was not correlated with recycling activity of small home appliance. In conclusion, type of furnace influences potential as metal resources of molten metals. The reason is that the amount of transferring Si, Ca and Fe is different by type of furnace.
( Junya Machida ),( Toshihiko Matsuto ),( Takayuki Matsuo ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-
Even after landfill is closed, biological degradation process and, production of leachate and landfill gas, continues for several decades or longer. In Japan, semi-aerobic structure is recommended for supply air into waste layer by natural convection. The heat generated by aerobic microorganism raise the temperature of waste, then the difference of temperature between waste and the atmosphere drives air to flow into waste layer from the end of leachate collection pipe. In the previous research by authors, there was found the positive correlation between gas velocity and the temperature at exit of gas vent, so the relation can be used to evaluate the soundness of natural aeration function of semi-aerobic landfill. In this study, data of gas velocity and temperature was collected from 26 landfills from which gas flow is detected. Additional measurement was also asked to increase data on the relation between gas velocity and temperature only. As a result, only 7 landfills were considered sound semi-aerobic landfill.