Ozone Oxidation-carbon Material Adsorption Technology To Remove NO_x,SO₂ And Hg⁰ From Flue Gas Of Industrial Boilers

Industrial boilers bring a lot of convenience in energy utilization and conversion,but the combustion of boiler fuel will produce a large amount of pollutants such as SOx,NOx,and heavy metals Hg.The discharge of these pollutants require proper treatment.Although the traditional method of removing SO2,NOx and Hg0 from boiler flue gas can achieve a certain flue gas purification effect,it has disadvantages such as complicated management,large area and high cost.In this paper,O3 oxidation and dry adsorption are combined for flue gas synergistic flue gas treatment:O3 is used to oxidize NOx,SO2 and Hg0 in the flue gas.After oxidation,the flue gas is adsorbed by low-cost corn biochar made from waste corn stalks or commercial coconut shell activated carbon,thereby achieving simultaneous desulfurization,denitrification and mercury removal.This method can effectively reduce the complexity of the process and the difficulty of management while achieving high pollutant removal efficiency.In this paper,electron microscope analysis,low temperature nitrogen adsorption-desorption,and elemental analysis of carbon samples were carried out,and a series of experiments of simulated flue gas and on-site flue gas were carried out.In simulation experiments,the effects of flue gas temperature and SO2 concentration on O3 oxidation characteristics were explored,and the effects of corn charcoal/coconut shell charcoal in removing SO2,NOx and Hg0 under different conditions were explored.In the industrial boiler flue gas experiment,the oxidation characteristics of O3 on the boiler flue gas were investigated.The combined use of O3 and corn charcoal/coconut shell charcoal on the treatment effect of on-site flue gas was explored,and X-ray photoelectron spectroscopy and temperature programmed absorption desorption analysis were performed on the carbon samples before and after adsorption.Finally,the process cost accounting was carried out on this basis.The above research results show that:(1)Coconut shell charcoal has richer pore structure than corn charcoal,and theoretically has stronger physical adsorption capacity;corn charcoal has higher O/C and N/C ratios than coconut shell charcoal,and theoretically has stronger chemical adsorption capacity.O3 has the highest oxidation rate of NO in the flue gas,and is almost unaffected by SO2 concentration.The increase in temperature inhibits the NO oxidation reaction but promotes the oxidation of SO2 and Hg0.Corn charcoal and coconut shell charcoal have poor NO adsorption effect and higher removal rate of high-valence NOx after oxidation.Therefore,the higher the NO oxidation rate,the higher the NOx removal rate.In contrast,corn charcoal has a better removal effect on high-valence NOx than coconut shell charcoal,but has a poorer removal effect on SO2 and Hg0.The removal rate of SO2 is not affected by O3/NO,but the presence of O3 can promote the removal of SO2.The removal effect of corn charcoal and coconut shell charcoal on high-valence NOx increased with the decrease of SO2 and Hg0 concentration.(2)Under the same O3/NO conditions,the NO oxidation rate in the on-site flue gas is significantly lower than the simulated flue gas.Under suitable conditions,the combined treatment of O3 oxidation and corn charcoal/coconut shell charcoal adsorption process can meet the ultra-low emission of flue gas on site.The cost accounting results found that the cost of the combined process can be lower than that of the traditional process in series.X-ray photoelectron spectroscopy analysis results show that the relative content of C-OH and C=O groups on the surface of corn charcoal before adsorption is larger than that of coconut shell charcoal,while the relative content of COOH and O-C=O groups is smaller;After adsorption,the relative content of C-OH and C=O groups on the surface of coconut shell charcoal and corn charcoal decreased,while the relative content of COOH and O-C=O groups increased.The adsorption of NOx is mainly affected by the C-OH and C=O groups,while the adsorption of SO2 and Hg0 is affected by the COOH and O-C=O groups and the physical adsorption capacity.The results of temperature-programmed adsorption and desorption showed that the desorption temperature of NO on the carbon samples was lower than that of SO2,and the SO2 desorption peak overlapped with the COOH desorption peak of CO2 at 200-400℃.