Numerical Simulation And Optimization Of Tank Cleaning For Chemical Tanker

Bulk liquid chemicals are complex and harmful.Therefore,for the sake of safety and economy,the tanker in chemical tankers need to be cleaned when changing different kinds of chemicals.Due to the large difference in the physical properties of chemicals,the specific influence parameters on the cleaning effect are not clear,and the quantitative research and analysis are not comprehensive enough.Therefore,it is of positive significance to explore the influence of various parameters on the cleaning effect of the washing process on the safety assessment of the washing operation.In this thesis,according to the actual situation and research status and different types of chemicals,the residual goods phase is added to simulate the washing process of volatile and non-volatile chemicals.The results are combined with intuitive cloud images and numerical analysis.The concentration of volatile residual gas in the cabin and the residual removal rate of non-volatile gas bulkheads are used as the evaluation criteria for their respective washing effects,and the actual washing optimization reference opinions are obtained.For volatile chemicals,benzene is taken as an example.In the first stage,15 sets of examples are used to verify the relevant rationality.The actual tanker size is reduced in a ratio of 1:100 to explore the fan ventilation effect under different outlet diameters and air supply rates.In the second stage,the comparative simulation of 12 sets of examples shows that the air supply rate of the fan is the main influencing factor.If the rate is 0.15 m/s,even if the diameter of the air outlet is increased from 3 mm to 14 mm,the gas in the tanker cannot be fully mixed and stirred,and it is difficult to effectively exchange air.After that,the air supply rate of the fan with the outlet diameter of 14 mm was increased to 2.50 m/s,and the benzene at the outlet could meet the safety requirement of 0.09 mg/m~3,which could be used as a reference for practical operation.For non-volatile chemicals,taking glycerol as an example,considering that it has a large viscosity and is easily soluble in water,according to the main forces in the cleaning process are jet impact force,wall shear force and dissolution of soluble goods,the nozzle outlet diameter,outlet pressure and jet distance are selected as the main variable parameters.In the first stage,10 sets of examples were used to verify the relevant rationality.In the second stage,12 sets of examples were used to compare and simulate.Combined with the removal rate and residual ratio of residual glycerol in the bilge under the same cleaning time,the better parameters of outlet diameter and outlet pressure were 10 mm and 1.0 MPa respectively under the fixed injection distance of 85 mm.According to the size distribution of the wall shear stress of the bilge water jet,the cleaning process is divided into three stages,and the specific area proportion is divided.At the same time,in order to explore the difference between soluble and insoluble substances,the specific dissolution ratio was 35.6%.Finally,according to the actual tanker size,the influence of jet distance and the location of residual goods is considered.In the first stage,7 sets of examples are used to verify the relevant rationality.In the second stage,50 sets of examples are used to compare and simulate.It is concluded that the cleaning efficiency of jet horizontal injection is lower than that of jet vertical injection.This is mainly due to the decrease of the rate of reaching the wall when the jet is injected horizontally,especially at a long injection distance,resulting in a decrease in the cleaning efficiency.Compared with G32 and G58,the cleaning efficiency of water jet vertical injection is 19%higher than that of water jet horizontal injection.In terms of specific better cleaning parameters,the outlet pressure and outlet diameter can follow the previous conclusions,and the injection distance should not exceed 92 d.This thesis shows that the simulation can effectively explore the quantitative analysis of the chemical ship washing effect and provide reference optimization for the actual washing operation.