Air Pollution Control in Urban Road Tunnels
Fumitake CHISAKA
Air Pollution Control of Automobile Exhaust Gas in Urban Road Tunnels
(FY 1991～1995)
Mr. Fumitake Chisaka(Director m3...@mel.go.jp)
Dr. Nobuhiro Aya (Senior Resercher)
Environmental Engineering Division
Energy Engineering Department
Mechanical Engineering Laboratory
Agency of Industrial Science and Technology
Ministry of International Trade and Industry
In the metropolitan regions, the environmental concentrations
of the nitrogen oxides (NOx) and particulate materials (PM) increase
considerably, and exceed the environmental standards of nitrogen
dioxide (NO2, 0.06 ppm) at almost of the measurement stations near
the street with large traffic volume. Specially, NOx concentrations
increase at near the outlets of road tunnels and the ventilation
towers. Diesel engine vehicles emit more amounts of NOx and PM than
gasoline engine vehicles, and these substances at high concentration
levels are an irritant and a health concern. Therefore, the air
quality control in road tunnels is very important. The removals of
NOx and PM are required to keep air quality within acceptable levels
in road tunnels. However, the NOx removal is very difficult at low
concentration levels in road tunnels.
Purposes of this research are to obtain a useful data for
designing of the device that eliminates simultaneously NOx and PM
pollutants, and to evaluate the effect of the removal device to
air pollution control from vehicle exhausts in road tunnels.
1. The adsorption filter for NOx removal from road tunnel gases.
The properties of zeolite honeycomb filters with respect
to NOx adsorption were examined through addition of ozone
and running of electric collector. For initial NOx
concentrations of 1.13 ppm to 2.49 ppm from diesel engine
exhausts, a removal efficiency of NOx is the range of 71 to
76 %. However, almost of nitrogen dioxide (NO2/NOx=0.98)
have passed through the filters. The NO2 is more harmful in
comparison with nitric oxide (NO). Therefore, we hope that
NO2 isn't discharged from NOx removal device. Ozone (O3) of 87%
is decomposed in zeolite honeycomb filters. Future studies
should examine the impact of adding up O3 of 20 ppm in front
of the honeycomb filters and increasing of filter surface areas.
2. Effect of air pollution protection using the NOx removal device
To investigate the NOx removal, we have produced the
plume dispersion model cooperated with the sources of a spot
and a line. When the traffic volume is maximum, the NO2
concentrations have passed the limit of 0.06 ppm inside of
the plume. However, for 0.25 times the amount of maximum NOx
exhausts, we can accomplish the environment standard of NO2
in the case of stable atmospheric condition. For D class
stability, the plume supplying of NOx from the tunnel rises
up 0.02 ppm highly from background of NO2.
The momentary concentrations of pollutants have been
measured at the point far away from about 150 m from the
street with common traffic volume. When a reversal vertical
temperature layer associated at a winter, the day average of
NO2 reaches 0.04 ppm, and 5 hours average exceed 0.055 ppm
in the night.
--- Mr. Fumitake Chisaka ----- Environmental Engineering Division ----
Mechanical Enginerring Laborarory,Namiki 1-2,tsukuba-city,ibaraki,Japan
--- Phone 81-298-58-7082 Fax 81-298-58-7275 -- m3...@mel.go.jp ----