国产精品永久免费视频- 无码精品A∨在线观看中文 -热re99久久精品国产99热-国产成人久久777777

A clean energy research institute in the city of Datong, Shanxi province, completed research on a new type of environmentally safe coal recently, according to the city's science and technology bureau, and it has gone into production for use in the city residential area, Datong Evening News reported on Nov 4.

After entering the market, the coal got a good reputation for being dust- and smoke-free, with a large heat output and low cost. It took two years of research to go into large-scale production, with the city's environmental monitoring station reporting that smoke and dust emissions were 63.8 mg per cubic meter and sulfur dioxide, 183 mg per cubic meter, well below the national standards of 200 and 900 mg.