Study On Simultaneous Desulfurization And Denitrification Process Of Coal-fired Flue Gas In NaClO/Na₂CO₃ Absorption System

China’s energy structure uses coal as the main energy source,and the direct combustion of coal will emit a large amount of SO₂ and NO_X.Directly emitted flue gas will eventually form acid rain,smog and photochemical smog,etc.,which endanger human health and natural ecology.At present,the most widely used desulfurization and denitrification technology in coal-fired boilers is calcium desulfurization and selective catalytic reduction denitration technology used in series.This process must have two sets of equipment,which are huge in cost and occupy a large area.Therefore,a technology for simultaneous desulfurization and denitrification of coal-fired flue gas is urgently needed.In many simultaneous desulfurization and denitration processes,the liquid phase oxidation method has a high removal rate and good industrial application prospects.Among the commonly used oxidants,sodium hypochlorite has the characteristics of high oxidation capacity and low price.However,the simultaneous desulfurization and denitration efficiency of NaClO solution alone is not high,so there are few studies on this in China.The desulfurization and denitrification process studied in this paper is based on sodium hypochlorite as an oxidant and sodium carbonate as a buffer.A series of experimental studies have been carried out in a bubbling model reactor.The main research contents include the effects of sodium hypochlorite concentration,sodium carbonate concentration,reaction temperature,initial p H value,air intake/gas residence time,gas dispersion mode and other factors on the simultaneous desulfurization and denitrification efficiency.The optimal reaction conditions were determined to be 0.65 mol/L sodium hypochlorite,0.09mol/L sodium carbonate,25℃,initial p H 11.9,intake air volume 50 L/h（gas residence time 4s）.When the distribution method is to pile up the Laxi ring filler with a size of 3.5 mm and a height of 6 cm,it can meet the pollutant discharge standards issued by the government for key areas,and the highest desulfurization and denitrification rates reach 100%and 82.23%,respectively.The sieve tray tower was used as the absorption device to amplify the small-scale test.The research contents include the influence of the sieve tray aperture,circulating flow,throat width and air intake on the tray pressure drop.Effect of pore size and circulating liquid flow rate on desulfurization efficiency and denitration efficiency.Under the conditions of 4 trays,opening liquid rate of 27%,aperture 6 mm,intake volume of 2800 m³/h,circulating fluid flow of 13 m³/h,the export concentration meets the pollutant discharge standards issued by the government for key areas,and the desulfurization and denitrification rates have reached94.98%and 90.88%.At the same time,the problems exposed in the amplification test were recorded and studied,such as the poor effect of the dust collector,which caused the absorption liquid to be contaminated and the 5 mm pore size to be blocked.In addition,due to the lack of heat exchange devices in the process,the temperature of the absorption liquid increases,which affects the absorption efficiency is another problem.The process of simultaneous desulfurization and denitrification amplification using the packing tower as the device was designed and calculated.The process data such as the tower diameter,the height of the packing layer and the pressure drop of the packing were calculated.