China builds ‘world’s biggest air purifire
Dr KK Aggarwal
An experimental tower over 100 metres (328 feet) high in northern China has brought a noticeable improvement in air quality. The tower has been built in Xian in Shaanxi province and is undergoing testing by researchers at the Institute of Earth Environment at the Chinese Academy of Sciences. The head of the research, Cao Junji, said improvements in air quality had been observed over an area of 10 square kilometres (3.86 square miles) in the city over the past few months and the tower has managed to produce more than 10 million cubic metres (353 million cubic feet) of clean air a day since its launch. Cao added that on severely polluted days the tower was able to reduce smog close to moderate levels.
The system works through greenhouses covering about half the size of a soccer field around the base of the tower. Polluted air is sucked into the glasshouses and heated up by solar energy. The hot air then rises through the tower and passes through multiple layers of cleaning filters.
The average reduction in PM2.5 – the fine particles in smog deemed most harmful to health – fell 15 per cent during heavy pollution.
The Xian smog tower project was launched by the academy in 2015 and construction was completed last year at a development zone in the Chang’an district. The purpose of the project was to find an effective, low cost method to artificially remove pollutants from the atmosphere. The cost of the project was not disclosed.
A full-sized tower would reach 500 metres (1,640 feet) high with a diameter of 200 metres (656 feet), according to a patent application they filed in 2014. The size of the greenhouses could cover nearly 30 square kilometres (11.6 square miles) and the plant would be powerful enough to purify the air for a small sized city. (South China Morning Post Excerpts)