Technologies in Environment-
Detoxification of Dioxins Using E-beams
Introduction
Detoxification of dioxins found in
the flue gases emanating from waste incinerators can
now be done with the use of electron beams. The Radiation
Chemistry Research Establishment of JAERI has developed
a system for this process. Japan is going to amend its
law for preventing air pollution later this year. The
amount of toxic equivalents (TEQ) permitted in flue
gases would be sharply reduced from the present emission
standard of 80 ng/m3. Typical amount of TEQ/m3 in the
flue gas emitted by the existing incinerators vary between
10 ng for small incinerator with a capacity of <
2 ton/hour and 1 ng for large incinerator with a capacity
of > 4 ton/hour. Incinerators using the new process
may reduce these amounts to 5 ng and 0.1 ng respectively.
Flue gases from waste incinerators are released into
the atmosphere after smokestack pollutants are eliminated
through electrostatic precipitation and/or filtration.
Currently, bag filters require subsequent detoxification.
The gaseous dioxins in the flue gases can be eliminated
or decomposed through charcoal absorption columns or
catalytic reduction process towers. However, both processes
also require subsequent treatment and their efficiency
varies with the temperature.
In the new process, electron beam is applied to flue
gases, generating highly reactive activated gases such
as activated oxygen from the ingredients of flue gases,
which decompose the chemical structure of dioxin. The
EB process system uses a shielded irradiation chamber
accelerator, which is superior to current bag filters
on two main counts. First, the process does not produce
any toxic residuals and can eliminate dioxins at a low
concentration. Second, it can be easily installed in
existing waste incinerators. Experience with radiation-chemical
technology using e-beams such as the decomposition of
voltaic organic chlorides at factories, and the de-sulphurization
of flue gases from thermal power plants has been used
to develop this process.
An e-beam system with 300 KV, 40mA accelerator and an
irradiation chamber has been giving demonstration tests
since Dec 2000 at Takahama Clean Centre in Haruna, Gunma.
Using real flue gas flowing at 1000 m3/h at 200 oC,
it reduces dioxin levels by 50, 80 and 90% with absorbed
doses of 3, 10 and 15kGy respectively. Its running cost
is about two-third of the system using bag filters.
The system may be commercialized by JAERI.
Contact for more information Science & Technology Wing Embassy of India
2-2-11, Kudan Minami, Chiyoda-ku
Tokyo 102-0074, Japan
Tel: +81-3-3262-2391 to 97,
Fax: +81-3-3234-4866
E-mail: tandonus@hotmail.com
