Study On Denitrification Performance Of NaClO₂ Solution Strengthened By Hydrodynamic Cavitation

With the development of shipping,the emission of exhaust pollutants from ships is increasing.The International Maritime Organization has continuously improved relevant laws and regulations to limit NO,emissions because of the harmful of NOx.The research focus of ship's exhaust denitrification is using oxidant to oxidize NO to high-valent nitrogen oxides and then removed by water absorption,but the disadvantages are large concentration of oxidant and high cost.Therefore,it is of great significance to study an economical and high NOx removal method for ship exhaust.Cavitation is a hydrodynamic phenomenon.Cavitation effects such as high temperature and high pressure can enhance the chemical reaction and the gas-liquid mixing effect.NaClO2 is a strong oxidant,which is common in ship denitrification research.In this paper,the cavitation effect was used to strengthen the denitrification of using NaClO2.The main contents are as follows:(1)The experimental platform was built to investigate the effects of different venturi injector upstream pressure,inlet gas flow rate,NaClO2 solution temperature,initial pH value of NaClO2 solution and NaClO2 solution concentration on denitrification performance.The results show that NO and NOx removal rates increase with the increase of upstream pressure,the temperature of NaClO2 solution and the concentration of NaClO2 solution,and decrease with the increase of inlet gas flow and solution initial pH value.When the upstream pressure exceeds 0.40MPa,the solution temperature exceeds 35?,and the NaClO2 solution concentration exceeds 1.000 mmol/L,NO,removal rate increases slowly,so considering the denitrification rate and economy,the optimal parameters are that the upstream pressure is 0.40 MPa,solution temperature is 35 0C,NaClO2 solution concentration is 1.000 mmol/L and initial pH value of NaClO2 solution is 7.00;(2)Based on FLUENT numerical simulation software,the venturi injector used in ship exhaust gas treatment was simulated to explore the effects of operating parameters such as upstream pressure,inlet gas flow and downstream pressure on cavitation performance.The results show that the cavitation intensity increases with the increase of the upstream pressure,and decreases with the increase of the inlet gas flow and the downstream pressure.The maximum growth rate of the cavitation bubble increases with the increase of the upstream pressure and decreases with the increase of the inlet gas flow.Basically,it is not affected by the downstream pressure.The maximum collapse rate of cavitation bubbles increases first and then increases with the increase of upstream pressure,and increases with the increase of intake air flow and downstream pressure.Considering cavitation intensity and economy,the best operating parameters given in this paper are that the upstream pressure is 0.40 MPa and downstream pressure is 0 MPa.