Existing Problems And Improvement Implementation Evaluation In The Ultra-Low Emission Technical Renovation For Coal-Fired Power Plant

As the air pollution has been payed more attention in China,the state proposed the ultra-clean emission concentrationstandards of air pollutants for coal-fired power plant.Theemission concentration of soot and sulfur dioxide?SO₂?,nitrogen oxides?NO_X?of new coal-fired power generating units must achieve the emission concentrationstandards of gas generator unit,which are 10,35 and50mg/m³respectively.The proposal of ultra-clean emission standards not only promotes the development of ultra-clean emission processes and equipments,but also brings new operation and maintenance problems to operators.At present,we has not enough experience in the operation and maintenance of ultra-clean emissionprocesses and equipments,and the selection of ultra-clean emission technology route is not well implemented based on the principle of"one factory,one policy"at the same time.Firstly,through the collection and study of the implementation status of ultra-clean emissions equipment for major coal-fired power plantsin China,the operation problems of ESP efficiency improvement,low temperature electric precipitator,wet electrostatic precipitator,fiber bag precipitator/electric-bag filter,desulfurizationinnovationcollaborativewithdedusting,denitration innovationcollaborative with dedusting have been summarized and analyzed.For the operated ultra-clean emission technologies,desulfurization system and dust removal unit is more diverse compared with denitration system.The main problems in the actual operation of ultra-clean emission process or facility mainly conclude:the design or selection of process or equipment is unreasonable and not meet with originalenvironmental protect ion equipment;the installation position is not reasonable for the CEMS online measuring pointsand sampling points,and th e accuracy of meter test is low;the quality of raw materials?desulfurization and denitration?is not up to the requirements of design;the chain effect caused by the a operation and improvement of equipmenton the downstream equipments.According to a selected coal-fired power plant,the performance experiments for the existing environmental protection equipment?electric precipitator,desulfurization and denitrification equipments?have been carried out to assess the operationstatus and analysis exsisting problems.This paper aims to carry out the studies of analyzing,improving and optimizing the exsisting problems,improve the operating and economy performance of environmental protection equipment for the selected coal-fired power plant,and reduce the emission concentration of air pollutants further.The denitration reactor existsthe problems of large concentration distribution deviation for NO_X and excessammonia sprayed.The introduction of model predictive control reduce the emission concentration of NO_Xin A and B sides from the original 58 and 41mg/Nm³?standard state,dry basis,6%oxygen content?to 30 and 36mg/Nm³ respectively,and the NO_X distribution deviation and ammonia escape rate in the outlet of denitrification reactor are all improved to a ce rtain extent.The quality ofdesulfurization agent?limestone?does not meet the design requirements for wet flue gas desulfurization,resulting in the problems in slurry preparation and the dehydration of gypsum.The excess emissions of sulfur trioxide,sulfuric acid mist and ammonium bisulfatecauses the phenomenon of blue smoke/yellow smoke.The overall operation of electric precipitator meets the design requirements.After adjusting the unit price of pollution emission charges,the monthly cost of the denitration systemwill be reduced by 140.9 and 157.9 thousand yuan respectively according to the different setting value of the NO_Xemission concentration,while the monthly cost of desulfurization system will increase by327.6 thousand yuan.