Firstly, air quality of inside and outside of tunnel is decreased because high concentration of exhaust gas cannot eliminate in time. Thus, safety and health for driver & passengers and living quality of residents live around outlet of tunnel are influenced because of poor air quality.
China is a country with numerous mountains. With the rapid development of economy and growing importance of environmental protection, mileage of highway tunnel has significantly increased. Due to highway tunnel is a relatively isolated space, air pollutants exhausted from automobiles, such as particulate matter, carbon monoxide, hydro-carbons, oxidesof nitrogen, are not convenient to spread around. Therefore, the concentration of air pollutant is increased continually. Moreover, with the number of automobiles raises sharply, current traffic volume of many highway tunnels far exceeds the original design standards. Thus, air quality has decreased because of poor visibility. Then safety and health for driver & passengers and living quality of residents who live around outlet of tunnel are influenced.
Secondly, the exhaust gas from construction vehicles spread around during the tunnel construction. Construction workers and maintenance workers are much easy to inhale dust and poisonous gas. Thus, poor air quality in highway tunnel endangers the occupational health of workers.
Most running highway tunnels do not meet the standards of ventilation and dust removal. Air pollution of automobiles is severe. Currently, workers stay long time in the tunnel, the morbidity of pneumoconiosis must be increased. If measures are not taken to control air pollution in tunnels, the morbidity of pneumoconiosis must be increased rapidly.
Thirdly, Underground Fast Track and City Tunnel are the important methods to solve the traffic jam problem due to the number of automobiles increases rapidly.
By the end of 2014, the number of automobile in domestic reached 154,000,000. However, there is still no progress in the product R&D used for tunnel maintenance and dust removal. Currently, there are totally 3 ventilation methods in domestic, include transverse ventilation, semi-transverse ventilation and longitudinal ventilation. These 3 ventilation methods only dilute air pollutants physically instead of purify. And the pollutants still spread outside of tunnel and then pollute the atmosphericenvironment.
In view of three reasons mentioned above, it is much necessary to install electrostatic precipitator(abbr. ESP) to achieve the ventilation and dust removal in tunnel.
ESP is a facility which removes particles from airflow by static electricity. It is consist of several modular components which include electrostatic dust removal unit, high voltage DC power supply pack, PLC intelligent control system, cleaning system, water treatment system and pre-filtration system, etc.
Operational Principle of ESP is as follow:
Firstly, dust gas flow close to the helical spike which powered by 12-15KV high voltage current in the case. Then the particles in the dust gas are charged negative under the effect of High-pressure ionization. Induced voltage and current are generated to dust collecting section (Honeycomb tube). Dust sticks to dust collecting section because of characteristic of positive and negative charge. The cleaning system starts to work once particles are collected up to certain amount. Finally,the particles removed out.
A mass of experiments demonstrated that dust removal efficiency of ESP which install in tunnel is more than 90% no matter how fast the wind velocity is. In the field of hygienic security, ESP not only can remove particles from pollutants in the tunnel, but also can protect the safety of drivers, passengers,construction workers and maintenance workers. In the field of environmental protection, ESP can remove particles to prevent pollutants spread to the atmosphere environment. In the field of fire safety, ESP can remove smoke more than 80% in a moment. Thus, drivers and passengers can gain more 5 to 10 minutes to escape from the fire. In the field of energy saving, after installation of ESP, jet fan only need to eliminate CO and volatile hydrocarbon. Then power consumption of jet fan is reduced.
Road Tunnel 公路隧道
Installation site of multi-cross ESP (MEP-1000)
Before:Amendment Bill of Atmospheric Pollution Prevention Act published