Breakthroughs turning trash into treasure

By Li You | China Daily | Updated: 2017-04-13 06:54

Forty-two percent of Beijing's daily household waste is transferred to 26 waste incineration plants built throughout the city's suburbs, more than is handled by any other garbage processing methods, such as sanitary landfill or biodisposal.

Among the 26 plants, there is one plant that has a daily processing capacity of 3,000 metric tons of household waste, accounting for 12.5 percent of Beijing's total.

The plant's name is Beijing Shougang Bioenergy Science & Technology Co Ltd.

Located at the former Capital Steel Corp in Lujiatan village, in the Tanzhe temple town of Beijing's Mentougou district, the plant occupies a total land area of 31.32 hectares.

In 2016, the project disposed of a total of 1.2 million tons of household waste, mainly from Dongcheng, Xicheng, Mentougou, Shijingshan and Fengtai districts.

"The plant was designed with the largest initial operation capacity in the world, and now, its scale still tops most incineration plants worldwide," said Zhao Shuming, head of the corporation's technology and quality department.

Though operated as an incineration plant, the project prioritizes environmental protection and people's livelihood by completing waste treatment in the best way possible.

Incineration along with the other disposal procedure of the household waste can generate flue gas and reduce leachate and solid residues.

HCl, SO2, nitrogen oxides and dioxin are major sources of air pollution from burning. To purify flue gas from incinerated waste, the plant combines in-furnace selective non-catalytic reduction de-nitrification, rotary-atomizing de-acidification, bag filters and selective catalytic reduction desulfurization.

The plant further supplements the procedures with de-acidification by dry power spray, and removal of heavy metals and dioxin through activated carbon.

"After the process, the denitration rate can reach 85 to 90 percent, which means the level of nitrogen oxides can be kept at a very low level," Zhao said.

According to the company, after the whole process, the HCl level is designed to be lower than 50 milligrams per cubic meter, lower than the 60 mg/Nm3 standard stipulated both by China and the European Union.

The level of nitrogen oxides, the main cause of acid rain, will be about 250 mg/Nm3, much lower than the 400 mg/Nm3 stipulated by the EU.

The solid residue generated by incineration can be regarded as general solid waste, and can be used as roadbed construction material or pavement bricks, said Zhao.

Lin Jinwen, director of the Division for Environmental and Sanitary Facilities at the Beijing Municipal Commission of City Management, said: "Incineration can help to reduce the amount of garbage going through the process by 80 percent and increase resource utilization by generating electricity and supplying heat for residents. It can also ease land pressure caused by landfill sites."

Nowadays, the annual power production of the plant reaches 380 million kilowatt-hours. It also has an annual heat supply of 349,000 gigajoules, covering more than 1 million square meters.

Since its trial operation, the plant has disposed of 3.05 million tons of garbage, equivalent to the capacity of two medium-sized garbage landfills.

The plant was set up under the support of Beijing Municipal Government as a major livelihood project in 2010, with 30 years of operation expected and 400 million yuan ($58.2 million) in registered capital.