Shanghai Electric Power (SEP), Subsidiary of China Power Investment Corporation, Trial Implement in PM 2.5 Dedusting

Source: China Business News

Reporter: xxx

Date: November 13, 2013

   On October 11 this year, the PM 2.5 concentration reached to its peak 174.9 micrograms / cubic meter for a time. 

   Currently, for Shanghai, the top priority is to effectively control the source of PM 2.5. A ‘mini’ thermal power plant built in dense residential area on Changxing Island at the estuary of Yangtze River is to pilot PM 2.5 whole process emission reduction.

   Collaborative integrated treatment of multi-pollutants

   In China, the first energy structure is dominated by coal. Thus, coal-fired power plants become the target in the government’s controlling sulfur dioxide, nitrogen oxides and soot emission.

   In general, the coal-fired power plants adopt conventional electrostatic precipitator, which can remove 99% dust with PM 10, while failing to effectively removing PM2.5 dust particles.

  Since soot deep processing equipments used by large-scale power plant needs a huge amount of capitals, the two ‘mini’ units in Shanghai Changxing Island No.2 Power Plant surely become the ideal pilot for collaborative integrated treatment of multi-pollutants for their ‘small size and less capital input’.

  The technology used in collaborative integrated multi-pollutants is to change the separate treatments in the past and integrate them into a collaborative method which coordinates and gives full play to each technique. This technology minimizes capital investment while maximizing environment benefit.

  First, the 85% nitrogen oxides contained in soot discharged from the boiler can be removed through denigration equipments.

  Then, the high temperature soot goes through poikilothermic treatment: the low-level economizer reduces the temperature from 160 to 100 degrees Celsius. Seemingly, this process is simple, but it ‘kills two birds with one stone’.

 Since higher temperature increases the soot volume and flow velocity, so temperature reduction may reduce the soot flow velocity, allowing the soot to slowly go through the dedusting polar plate, thus improving the dedusting effectiveness. During this process, the energy emitted from the soot is not wasted, but absorbed by the colder water in the water cycle cryogenic tank and change to recyclable energy, improving the energy efficiency of the power plant.

  Next, the most of the soot contained in the smoke is removed through dry electrostatic precipitator. The technology of the so-called dry electrostatic precipitator goes like this: let the soot goes through densely arranged polar plates and attach different charges; the small particles aggregate into large ones according to principle of ‘like charges repel and opposite one attract’; the soot freely settles and starts ash bucket dedusting. Electrostatic precipitation achieves remarkable effect, for the soot concentration per cubic meter reduces to 1/600.

  In the following step, 98% of sulfur dioxide is successfully removed from the smoke through wet flue gas desulfurization.

  Finally, the remaining smoke ends its journey after entering into wet electrostatic dust collector. Different from electrostatic dust collection, in the wet electrostatic dust collection, the charged dust particles are gathered on the dust collection board, and are washed by water to the dust bucket and then discharged out. In a wet environment, the resistivity of soot is lower, making the soot easy to agglomerate and settle. At the same time, the sulfur trioxide can be dissolved and absorbed by water.

  Shanghai Electric Power (SEP) estimates that, by collaborative integrated treatment technology, the concentration of nitrogen oxides, sulfur dioxide and PMx reduce 30 mg, 28.6 mg and 4.1 mg per cubic meter. According to the most strict state emission standard GB23113-2011, which is to be implemented in 2014, the goals of emission for the coal-fired power plants in main areas are 100mg, 50mg and 20mg per cubic meter respectively. Therefore, this technology is more effective than the state standards in terms of emission effectiveness.

  The Challenge Lies in Balance of Environmental Protection and Capital Investment

  However, for enterprises, huge investment in environmental friendly technology is the biggest bottleneck for further adopting environmental protection equipment.

 Collaborative integrated multi-pollutant control technology needs enormous capital investment. Mr. Hu Weibin, secretary of the party committee of Shanghai Shangdian-Caojing Power Generation Co., Ltd, said, the low-temperature economizer technology in the phase I can save 8,000 tons coals every year, while the transformation of low-temperature economizer technology needs the capital investment worthy of the value of 40 thousand tons of coal. However, Mr. Hu admitted that among the energy saving techniques, few can bring actual economic benefits like low-temperature economizer.

  Judging from the state power-related policies, the environmental protection subsidies on electricity price cannot make up the capital investment on environment friendly equipments. Thus, some power enterprises assume presentable looks---only talk and not to act.

  According to existing national policies, the current subsidies on electricity price for power enterprises that adopt denigration technology are one cent per kilowatt. For those power enterprises that adopt new technology transformation and meet the national standard, the subsidized electricity price is 0.2 cent per kilowatt. The subsidized electricity price for power plant adopting desulphurization is 1.2 cents per kilowatt.

  Wang Yundan, Chairman of Shanghai Electric Power (SEP) estimates that the total cost of denigration and desulphurization is equivalent to four cents per kilowatt.

(This new is from China Business News dated November 13)


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