Simultaneous Removing SO₂ And NO From Flue Gas By （NH₄）₂S

In recent years,with the rapid development of our economy,level of industrialization significantly increasing and structural adjustment and industrial development,finishing industry gradually be taken attention.mineral mining,smelting and processing is still an important part of our industry.in the traditional smelting industry,the acidity of SO2 and NOx is great harm to human body and the environment,which has an increasing social concern and attention.Although the air pollution is more and more serious,Sulfur dioxide emissions accounts for the second,NOx emissions is also rising in constant in China now.But the emissions from mineral smelting account for a high proportion in all industries.Its waste gas mainly includes:SO2,SO3,NOx,water vapor And some heavy metals and etc.Among these major poIlutants,SO2 emissions from largest emission concentration of about 0.05%to 25%;In zinc smelting process,NOx emission concentration is about 150 to 200ppm,more than 90%of them are NO,therefore,removing the NOx in flue gas is mainly the NO.At present how to effectively and economically control emissions of sulphur dioxide and nitrogen oxides is problems of extreme value and solving in the field of environmental protection all over the world.Thus to explore suitable combined control and Resource Technology for nonferrous metals industry furnace flue gas SO2 and nitric oxide(NO)has important theoretical and practical significance to solve the urgent problem of the removal of pollutants in smelting industry.This research is mainly tried to flow about 5%of SO2 and 352mg/m3 of NO mixing cylinders(Ar balance,Dalian Special Gases co,LTD production)into the bubble absorber at the flow rate of 200mL·min-1 in water bath temperature is 20℃ to 80℃,the concentration of O2 in the mixture is about 6%in the process of absorption,The concentration ratio of SO2,NO and O2 is in line with the requirements of simulated flue gas,and then experimental platform has been establisied;This experiment chooses ammonium sulfide solution as absorption liquid to test absorb and purge NO in smelting flue gas containing SO2,focus on exploration and ammonium sulfide removal of nonferrous smelting process of SO2 and NO optimum process conditions,we will test the influence of reaction conditions such as ammonium sulfide solution concentration,pH value,gas flow rate,temperature on the absorption process.And we will use X-ray diffraction(XRD)and X-ray fluorescence spectrum(XRF)characterization methods to analyze the reaction products in the reaction system,determine the reaction mechanism of the experiment.Experimental results show that under the condition of temperature is 20℃,NO flow rate of 200 ml/min,the concentration of a solution of(NH4)2S is 0.5 mol/L,(NH4)2 S solution absorbs NO Separately than NO absorption rate with the presence of SO2 absorption is lower,when the presence of SO2 and O2,gas residence time is 2.4s,pH is 6.1 to 8.2,additives are ammonia and urea,NO removal rate is 59%to 69%and does produce H2S,SO2 removal rate is more than 99,99%,and reached the Air Pullutant Emission standards(GB25466-2010).The solution at the end of four reaction system of(NH4)2S-NO,(NH4)2S-NO-O2,(NH4)2S-NO-SO2 and(NH4)2S-NO-SO2-O2 by H2O2 and NH4HCO3 treated with evaporation and crystallization at 80℃ obtained product were characterized by XRD and XRF analysis.The results showed that nitrogen content of the nitrogen compounds in the product only in the presence of SO2 and the O2 responses is higher,with 24.21%.the percentage of nitrogen in ammonium nitrate refer standard GB2945-89 in the industry that is no clear limit,ammonium nitrogen content in flue gas has reached to 23.6%in the smelting,refering by-product ammonium sulfate DL/T 808-2002 and reached the requirements of qualified products,Both can be used as compound fertilizer.Experimental results also concluded that when involved in the reaction of sulfur dioxide concentration is high,it inhibits the removal of NO,when involved in the reaction of sulfur dioxide concentration is low,it proves that sulphur dioxide and ammonium sulfide solution generated(NH4)2S2O3 absorps NO through the analysis of the reaction product,the experiments show that low concentration of SO2 has a promoting effect on the removal rate of NO.After analysis of product simultaneous removal of NO and SO2 with ammonium nitrate by X-ray diffraction(XRD)and X-ray fluorescence spectrum(XRF)methods analysis,then treated with H2O2 and NH4HCO3,finally the solution treated at 80℃ by evaporation and crystallization obtains the main product,which is(NH4)2SO4,(NH4)(NO3)2SO4,(NH4)3H(SO4)2 and S,the possible reaction mechanism is Established.The research proves that the problems to avoid the post-processing of large energy consumption,high equipment requirements and serious secondary pollution and so on,the ammonium nitrate and ammonium sulfate compounds can be directly as a product to sell,and this highly referenced technology is applied to industrial purification.