Study On The Physical Properties Of Molasses Alcohol Wastewater And Numerical Simulation Of Falling Film Evaporation In Horizontal Tube

Molasses alcohol wastewater(MAW)is a high concentration organic wastewater produced in the process of alcohol production,which is a key factor restricting the development of molasses alcohol production process because of its difficulty in processing.The concentration method is one of the most effective treatment methods for the waste liquid,but it has the problems of large equipment and high energy consumption.The physical data of MAW is very lack,which restricts the scientific research,equipment design and process optimization of concentration method seriously.In this paper,some momentum and heat transfer parameters of the waste liquid are measured in the range of operating parameters of the multi-effect evaporation process,and the numerical regression and analysis are carried out.On this basis,it is proposed that the first evaporator with the biggest energy consumption can adopt the horizontal tube falling film evaporator with high heat transfer efficiency and small heat transfer resistance,instead of the central circulating tubular evaporator widely used in the production.The behavior of the wastewater in the horizontal tube falling film evaporator was numerically simulated by using the measured physical data,which provided the basis for the application of the evaporator in the concentration process.The main contents and results of this paper are as follows:The basic data of Brix15~60 MAW and the parameters of viscosity,specific heat capacity and thermal conductivity were determined.The data show that the viscosity of the wastewater decreases with the increase of temperature,and the larger the Brix,the more obvious the viscosity decrease;the specific heat capacity and thermal conductivity of MAW increase slowly with the increase of temperature,and the Brix is larger,the smaller the heat capacity and thermal conductivity.Using the MATLAB software,the Brix(B),temperature(T)as the independent variable,and viscosity,specific heat capacity,thermal conductivity as the function of the numerical simulation,the applicable scope of the full coverage of the multiple-effect evaporation concentration process of the correlation.The error analysis proves that the relative error between the calculated value and the experimental value is less than 3.5%,which is within the acceptable range of the project.The 2D physical model of falling film evaporation of transverse tube is established by using the Mixture model of Fluent software and the numerical simulation the paper studied the liquid film flow in the process of falling film evaporation of molasses alcohol waste liquor,analyzed the effect of different spraying density,spraying height,pipe diameter and tube bundle arrangement on the liquid film distribution,and discussed the comparison of heat transfer efficiency.Results show that the thickness of liquid film in horizontal tube falling film evaporation process decreases with the increase of circumferential angle firstly,and the minimum value of the circumferential angle is near 110°,and the spray density of waste liquid is better than that in 0.429~1.288 kg/(m·s)and spraying height in the range of 5~8 mm.The results showed that the heat transfer efficiency of the horizontal tube falling film evaporator was higher than that of the central circulating tubular evaporator in the concentration process of molasses alcohol waste liquor.