Simulation Study Of Ship Ballast Water Treatment System Based On Inert Flue Gas

With the continuous development of the world shipping industry,the harm caused by ship's ballast water is getting worse.At present,in the research on various ship ballast water treatment technologies,the electrolysis method and the ultraviolet method have become the two mainstream technologies.Electrolytic treatment of ship ballast water,excessive concentration of residual chlorine will corrode the hull structure,and the treated ballast water will also cause secondary pollution when discharged;When the ship's ballast water is treated by ultraviolet method,the microorganisms after irradiation may have photoreactivation phenomenon,and the energy consumption is higher than other treatment methods.Therefore,it is more and more important to study new ship ballast water treatment technology.The inert flue gas deoxidation method can be used as an effective solution because of its low operating cost,no chemical generation,no secondary pollution,and delaying corrosion of the ballast tank.In this context,this paper proposes to treat ship ballast water by inert flue gas deoxidation method.The inert flue gas deoxidation method introduces the inert flue gas generated by the ship into the ballast water pipe through the ejector,mixes it with the ballast water and sends it to the ballast tank to inactivate the microorganisms.This paper clarifies the working principle of the ejector and the mechanism of inactivation of microorganisms by inert smoke.Based on the principle of inert gas treatment of ballast water,an experimental system was designed.Based on the Fluent software,the ejector structure is simulated and optimized.It is concluded that the optimized ejector structure increases the inspiratory capacity of the ballast water to the inert flue gas under the same working conditions.The lethal rate of inert smoke to chlorella and Escherichia coli was analyzed by experiments,and the optimal conditions for inactivating bacteria to inactivate microorganisms were established.Corrosion kinetics and thermodynamics were used to investigate the corrosion mechanism of ballast water treated by inert flue gas to ballast tanks.The corrosion effects of ballast water treated by inert flue gas on ballast tanks were analyzed by experiments.The test results show that:1)The volume ratio of inert flue gas N₂ and CO₂ mixture is7:1,the dissolved oxygen concentration in ballast water is 0.5mg/L,and the pH value is 6,the mortality rate of chlorella is 100%,and the lethal rate of E.coli is 99.98%,which meets the D-2 standard;2)The water quality of the ballast water after the inert flue gas treatment was detected,and no other chemical substances were found;3)Inert flue gas deoxidation treatment of ship ballast water,most of the corrosion factors in the seawater medium before and after treatment have not changed,the change factor is only the treatment factor;From the weight loss test results,the average corrosion rate of the ballast tank in the corrosive medium with dissolved oxygen concentration of 0.5 mg/L and pH 6 decreased by 69.02%compared with that in the simulated seawater;According to the results of electrochemical corrosion test,in the corrosive medium with dissolved oxygen concentration of 0.5 mg/L and pH 6,the corrosion tendency of the ballast tank is reduced.Therefore,the treatment of ship ballast water with a mixture of inert flue gas N₂ and CO₂ can reduce the corrosion rate and corrosion tendency of the ballast tank.