China has a pretty serious pollution problem, with so much smog in some parts of the country that it can discolor buildings and even block the sun. By some estimates, high levels of air pollution in China's cities cause between 350,000 and 400,000 premature deaths each year. But a new project in Xi’an, one of the nation's most severely polluted cities, aims to lessen it, thanks to a massive 200-foot chimney. However, unlike most fireplaces, this one will not increase air pollution levels, but will act as a purification system for the outside air, filtering out harmful particles and blowing clean air into the sky.
The chimney is designed to remove particles called PM2.5, referring to particles with an ultrafine mass of less than 2.5 microns. This is known to be very dangerous for individuals and can increase the risk of age-specific mortality, particularly from cardiovascular causes.
“The Solar-Assisted Large-Scale Cleaning System (SALSCS) consists of a green house with a circular or rectangular base with glass panels gradually rising towards the central tower,” Professor David Y.H. Pui, one of the researchers on the project, told Digital Trends. “Solar heating heats the polluted ambient air that is drawn in under the panels, and the hot air rises towards the central tower due to its buoyancy effect. A bank of filters is placed around the inlet of the tower to remove PM2.5 pollutants, so that only clean air exits the outlet at the top of the tower. By placing the SALSCS near a large city, you will draw polluted air into the SALSCS and return the clean air to the city to reduce the concentration of PM2.5. The SALSCS glass panels are coated with nanoparticles to remove nitrogen oxides, one of the main precursors of PM2.5 and ozone. "
While the results have yet to be released, the $ 2 million project has yielded positive results. Pui said the project's research group has found a 19 percent decrease in PM2.5 concentrations in a 10-square-kilometer area surrounding the Xi’an SALSCS, compared to other parts of the city.
“It took Los Angeles several decades to reach today's pollution levels in China by controlling pollutants at their source,” continued Pui. “China is likely to be able to achieve this in a much shorter time due to the new technologies available and the tightening of emission standards. "In a shorter period of 10 to 15 years, China can benefit from the implementation of SALSCS technology for large-scale cleaning of urban air pollution."
Next, Pui said the team hopes to build a much larger SALSCS in Xi’an, which will measure 1,000 feet. They also want to expand to other parts of China, as well as beyond
By Luke Dormehl
Original article (in English)