Research Of Denitration System Retrofit In Power Plant

With the rapid development of social economy in recent years, power supplyincrease rapidly, as a result, the quantity of coal increased significantly and NOxemissions of coal-fired power plant increase rapidly. Nitrogen oxides which causeserious damage to the atmospheric environment in China, control of NOx emissions hasbecome one of the focus of the current environmental protection work in China, effectivecontrol of nitrogen oxides generating in the process of coal fired is imperative. To reduceNOx emission of thermal power unit in order to meet increasingly stringent emissionstandards and improve air quality, flue gas denitration project of old and new thermalpower unit appears especially important.This paper studies NOx formation mechanism and influence factors in the thermalpower unit, NOx emissions control and processing method.and then compares thedifferent methods of nitrogen treatment. The thesis is focused on the principle ofselective catalytic reduction method, and side effects occurred in the process ofdenitration reaction, the layout of denitration systemt and composition of reactor, thechoosing principle of denitration technology, the preparation of denitration reaction agentand the comparison of different denitration agent. The thesis analyzes the influence ofinstallation of SCR device on boiler host device, flue bypass reactor and and other relatedproblems.Based on the practical situation of power plant units, the unit adopts the route ofreduce NOx emissions first and then denitration to implement low nitrogen combustionand the renovation of the denitration project on#156units. According to the unitoperation condition before and after the retrofit and test results of Electric PowerResearch Institute, retrofit of the low nitrogen combustion and grading air distributionreduce the temperature field of the main combustion zone and effectively reduce thermalNOx production of the W type boiler and NOx level were significantly reduced in the boiler flue gas. The average NOx emission concentration1210mg/m3(standard state dry,O2=6%) at330-335MW before the transformation of the burner dropped602mg/m3at330MW load after the transformation and achieve the desired purpose (below800mg/m3). The measured thermal efficiency of the boiler is92.63%, which is higher thanthe design value (91.82%) at350MW. Besides the boiler thermal efficiency is higherthan design value under other conditions. The results show that economic performance of#6boiler is well. The boiler thermal efficiency after retrofit is higher than that before thetransformation under various operating conditions. The technical route of reducing NOxemissions firstly and then implementing denitration is adopted in the denitration project.When the concentration of nitrogen oxide after the modification of the existing burners isreduced to a certain level and then gas denitration is implemented, which makes theconcentration of NOx emission reach the allowing the NOx emission concentration200mg/m3of new "power plant air pollutants emission standards"(GB13223-2011). Thesuccess transformation of denitration of the unit provides valuable experience for lownitrogen combustion system formulation and denitration project of the similar unit.