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Foreword
In order to realize the comprehensive and efficient utilization of coal resources, promote energy saving and emission reduction, and solve the problem of utilization of low calorific value coal resources, Shanxi Provincial Development and Reform Commission issued the "Twelfth Five-Year Plan" for generating low-calorific value coal in Shanxi Province in 2015. The implementation of "Planning" is of positive significance for promoting the comprehensive utilization of coal resources in Shanxi Province, reducing the adverse environmental impact of coal gangue and slime storage and delivering clean energy to the eastern regions such as Beijing, Tianjin, Hebei, Jiangsu and Shandong [1]. Promoting the construction of low-calorific value coal power generation projects is a strategic move of our province to readjust the structure, turn the way, and promote the transformation. It is also a practical need to promote enterprises to improve pollution control and improve the regional environmental quality [2].
According to the distribution characteristics of coal resources in Shanxi Province, during the 12th Five-Year Plan period, low-calorific value coal power plants are built around large-scale coal-electricity bases, forming the three major coal-power bases in North Shanxi, Jinzhong and Jindong. The project mainly relies on the planning of large-scale coal preparation plants Construction of large coal-fired integrated low-calorific value coal power plant. The three major coal bases plan to build 29 new low-calorie coal power generation projects, with an installed capacity of 24.2 million kilowatts.
1 Low-heat-value coal-fired power plant implementation of the ultra-low emission standards and the current coal-fired power plant pollutant emissions national environmental standards comparison
In the opinion of the general office of Shanxi Provincial People's Government in August 2014 on promoting ultra-low emission of coal-fired generating units in the province, it was proposed that ultra-low emission standards should be implemented for the concentration of soot discharged from new coal-fired thermal units [3]. Table 1 gives a comparison of the current national standards for emission of soot and ultra-low emission of coal-fired power plants in China.
As can be seen from Table 1, the ultra-low emission standards for soot and the thermal power plant in 2011 promulgated the control standards for pollutants, the more stringent. In December 2015, the NDRC issued the "Work Plan on Printing and Distributing the Ultra-Low Emissions and Energy Saving Reform of Coal-fired Power Plants" and explicitly requested that all qualified new coal-fired generating units nationwide achieve ultra-low emission levels and speed up the use of coal in service Generators ultra-low-emission transformation pace. It can be seen that the ultra-clean emission will be the general direction of the green thermal power station of coal-fired power station in China, and coal will enter the ultra-low emission stage.
2 coal-fired power plant flue gas pollutants smoke conventional process control program
At present, the existing routine flue gas treatment island tail of the domestic coal-fired power plant boiler is generally composed of denitration, precipitator and wet desulfurization. The flue gas directly enters the chimney from the wet desulfurization, as shown in FIG. 1.
At present, dust removal facilities adopted by the power plants mainly include electrostatic precipitators, bag filters and electric bag filters. After taking the above dust removal measures, the smoke and dust in the flue gas can meet the current requirements of the power plant dust emission standards (GB13223-2011). However, to meet the ultra-low emission standards there is a certain degree of difficulty.
3 Low calorific value coal plant to achieve ultra-low emissions of soot general idea
For the low-calorific value coal power plant in Shanxi Province, the high sulfur content, high ash content and low calorific value of coal are the main characteristics of coal with low calorific value in Shanxi Province. In the case of such coal quality, the emission of soot To achieve the ultra-low emission standards proposed by the Shanxi provincial government, the use of conventional coal-fired thermal power pollutant control technology program, more difficult.
During the process of environmental impact assessment of low-calorific value coal power generation, after repeated communication and investigation with construction units and design institutes, and drawing on the advanced dust removal technology in developed countries, the pollution prevention and control measures have been technically and economically demonstrated. After that, In order to achieve "ultra-low emission" of soot, the coal-fired power station finally proposed the technological process scheme of "end-of-pipe" and "coordinated control".
4 for low-calorific coal plant pollutants ultra-low emissions of technology proposed route
(1) In order to meet the ultra-low emissions, front-end with dry dust, while the end of wet flue gas desulfurization desulfurization wet electrostatic precipitator treatment program:
Combination program 1. Electrostatic precipitator + wet desulfurization + wet electrostatic precipitator
Combination of programs 2. Low temperature electrostatic precipitator + wet desulfurization + wet electrostatic precipitator
Combination of programs 3. Electric bag filter + wet desulfurization + wet electrostatic precipitator
(2) the use of low-temperature electrostatic precipitator or ultra-clean electric bag + efficient mist eliminator flue gas synergistic treatment technology program:
Combination of programs 1. Low temperature electrostatic precipitator + wet desulfurization (with efficient demister)
Combination of programs 2. Ultra-clean bag filter + wet desulfurization (with efficient demister)
4.1 tail flue gas to increase the end of the wet electrostatic precipitator treatment program
The wet electrostatic precipitator technology can effectively avoid the secondary fouling caused by wet desulphurization, such as gypsum rain, acid rain and other fields, to complete the re-treatment of flue gas after desulfurization, and effectively absorb the flue gas entrained droplets desulfurization Products, to avoid the droplets dissolved in the desulfurization products in the air crystallization of secondary particles caused by pollution.
4.1.1 tail to increase the characteristics of wet electrostatic precipitator
The efficiency of dust removal is not affected by the specific resistance of dust, which can effectively trap fine particles (PM2.5 dust, SO3 mist, aerosol), heavy metals (Hg, As, Se, Pb, Cr), organic pollutants Dioxins), etc .; can capture wet desulfurization system produces pollutants, eliminate gypsum rain, ease the downstream flue, chimney corrosion, save the cost of preservatives; other dust removal equipment can reach very low soot emission limits (<5mg / m3), to achieve ultra-low emissions.
4.1.2 tail to increase the wet electrostatic precipitator process
In a wet electrostatic precipitator, water mist condenses the dust and charges it together with the dust in the electric field and is collected together to collect the water mist on the plate to form a water film that is dewatered and held The board is clean. At the same time due to lower flue gas temperature and moisture content, the dust ratio dropped significantly, so the wet electrostatic precipitator working condition is very stable.
4.1.3 Three programs of technical and economic comparison
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