Abstract: In order to achieve the coordinated removal of multi pollutants and avoid the problems of wet absorption process,a semi dry flue gas multi pollutant integrated removal process was proposed based on the combination of low temperature oxidation denitrification and ash calcium cyclic desulfurization and dust removal.The NO removal experiment on pollutants integration removal process of oxidation coupled ash-calcium cycle was carried out.The calcium absorption characteristics of calcium based absorbers for NO_xat low temperature were investigated in fixed bed and liquid-phase experimental device.The de NO_xeffect was verified on gas-fast-bed industrial test device.The results show that the absorption rate of NO_2 calcium base is 20%-30% in fixed bed,under the conditions of 70-80 ℃,O25%,RH 40%-60%.The average denitrification rate of liquid absorption is more than 90%,at NO_2 concentration 200×10~(-6),Ca( OH)_2 suspension concentration 1%,70 ℃,O_2 content of 5%.Reaction temperature and relative humidity are the key factors affecting the absorption of NO2.Under the experimental conditions,the lower the reaction temperature is and the higher the relative humidity is,the higher the removal rate of NO_2 by calcium based absorbers is; the change of NO_2 initial concentration in the low concentration range has little effect on the denitrification effect.Under the condition of inlet NO concentration 231-423 mg/m3,absorption reaction temperature75 ℃,oxidation temperature 140 ℃,O_3/NO0.9-1.8,the NO_xcalcium absorption rate is 83%-89%,NO oxidation rate 74%-97%,and the total de NO_xrate 66%-87%in the industrial test device.The oxidation rate and denitration rate increase with the increase of O_3/NO,and the concentration of NO and NO_xat the outlet of the device decreases after oxidation.Therefore,in a certain range,the higher O3/NOis,the better the denitration effect is,but the ozone escape increases. In actual operation,the reasonable process parameters should be selected according to the site conditions.According to the denitration products IR results,NO_2 reacts with Ca( OH)_2 to form nitrate and nitrite.The de NO_xrate of the three methods is as follows: wet method( liquid absorption) > semi dry method( gas fast bed) > dry method( fixed bed),and the gas fast bed is close to liquid-phase.The results are mainly affected by the way of humidification,that is,the existence and relative amount of liquid water are the key factors affecting the absorption reaction. This is because the reaction form between NO_2 and Ca( OH)_2 will change from gas-solid heterogeneous reaction to rapid ionization reaction in the presence of water.Therefore,the more moisture and relative humidity in the reactor is,the higher the absorption rate and the denitrification rate is.The lowest NO_xemission concentration is 30 mg/m~3,reaching the ultra-low emission level.It realized the high-efficiency collaborative removal of multi-pollutants in the same device.The flue gas purification technology with oxidation coupled with ash calcium circulation is suitable for the treatment of small and medium-sized coalfired flue gas,and has a broad application prospect.