Changeover conundrum

Opened in 1999, Huaneng Beijing Thermal Power Plant has four coal-fired generation units, which have a combined capacity of 845 megawatts. It provides 10 percent of the electricity consumed in Beijing annually and about 33 percent of the heat supplied to the city's central heating pipe network.

In 2006, when Beijing was applying to host the 2008 Olympic Games, the plant upgraded the desulfurization devices in four boilers, lowering sulfer dioxide emissions from between 400 to 500 milligrams per cubic meter to less than 50 mg. A year later, it modified denitration devices, technology that removes nitrogen oxide from exhaust gases, and reduced nitrogen oxide emissions from 400 mg per cu m to less than 100 mg.

In recent years, PM2.5 levels have become a matter of public concern. As a result, this year, Huaneng Beijing has finished upgrading one of its dust-collection facilities by using a technology currently employed in Japanese coal-fired power plants, which lowered emissions of dust to less than 10 mg per cu m.