Annual Report on the Environment and the Sound Material-Cycle Society in Japan 2007 Page: 71
132 p. : col. ill.View a full description of this text.
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Fig. 2-17 Trend in the amount of dioxins emitted from waste incineration plants
(g/year)
7,500
New guideline laid d505 own Industrial waste incineration plants
New guideline laid down
S_ --- General waste incineration plants
6,000 1,505
4,500
3,000 2,63 New regulation value applied
5,000 1,105 2,045 from December, 2002
695 1,577 4 16 33
1,550 636 with 1997)
1,5 1,350 1,019 812 75 71 69 64 50 51
0 1997 1998 1999 2000 2001 2002 2003 2004 Target value of
reduction (2010) (Year)
Note: 2004 value and target value of reduction are percentages with respect to 2003.
Source: Ministry of the Environment
measures against dioxins, and regulations on exhaust gas and waste water and measures for contaminated soil were stipulated. For
example, for dioxins generated in a waste incinerating facility, the emission standard was determined to be 0.1 ng-TEQ/m3N (for
incinerators with a 4 t/h or larger capacity). To meet these regulations, various activities have been conducted and the amount of
dioxins emitted in 2003 from waste incinerating facilities has been reduced by approximately 98%, compared to 1997 figures (Fig.
2-17).
The development and introduction of excellent technology in harmony with institutional reinforcement has greatly reduced the
generation of dioxins. Dioxins are thought to be generated when carbon compounds that remain as unburned material react with
chlorine in the course of combustion. For their reduction, it is necessary to keep combustion temperatures at 800C or higher and
make combustion as complete as possible.
The aforesaid new guidelines require new furnaces to maintain a combustion temperature of 850C or higher for two seconds or
longer. According to this requirement, the introduction of full continuous type incineration plants, which can maintain high-
temperature combustion for a long period of time, have been promoted, in order to reduce the dioxins generated. Because dioxins
are generated at a temperature of about 300C , under the catalytic action of copper, etc. contained in fly ash, a method is applied
that quickly cools exhaust gases from 800C or higher to 200C or lower and collects dust in a bag filter. In addition, the technology
of spraying activated carbon powder in the inlet of bag filters to adsorb dioxins on the surface of the activated carbon and the
technology of letting the exhaust gas flow through a tower filled with activated carbon powder after dust collection to adsorb
Column: Coexistence of the Reduction of Dioxins and Power Generation
While it is necessary to reduce the amount of dioxins emitted from waste incinerating facilities, it is also necessary to
introduce and expand power generation from waste as a way to cut CO2 emissions. Various measures are being taken,
including power utilities' purchasing surplus power of waste power generation and the introduction of the RPS system (the
Special Measures Law for the Utilization of New Energy, etc. by Electric Power Suppliers).
To prevent dioxins at waste incinerating facilities, rapid cooling to 300.C is needed, in addition to increasing the
combustion temperature and securing the retention time. There was concern that the slow cooling of exhaust gas by the
boiler, which is necessary for power generation, may cause the re-synthesis of dioxins, but this problem has been solved by
spraying activated carbon in the after-flow, installing a catalytic reaction tower, etc. Today, high-efficiency power generation
is possible while reducing dioxins.
Thanks to these measures, the amount of dioxins emitted in 2004 from waste incinerating facilities in Japan was reduced
by 98% or more, compared with 1997, while the electricity generated from waste increased 2.2 times. These new
technologies are the core 3R technologies for waste management in Japan, where municipal waste is mostly incinerated, andare attracting attention worldwide.
71
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Japan. Kankyōsho. Annual Report on the Environment and the Sound Material-Cycle Society in Japan 2007, text, 2007; Tokyo, Japan. (https://digital.library.unt.edu/ark:/67531/metadc11843/m1/73/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .