Experimental Study On Ligin Suspension Of Horizontal Tube Falling Film Evaporation

Falling film evaporator on horizontal tubes with the characteristics of higher heat transfer coefficient, lower temperature difference and operational stability, are widely used in seawater desalination, refrigeration systems,processing and sucrose of the black liquor evaporation and concentration process.Falling film evaporator on horizontal tubes has been used in the enrichment process of distillation waste dregs for cellulosic ethanol production, three kinds of tube diameter (φ38mm,φ45mm and φ>57mm) has been selected in this paper. Experiments on falling film lignin suspension outside horizontal tubes were done respectively to investigate the impact of the spray density, temperature difference, heat flux, tube diameter, solid content, and fouling resistance on the heat transfer performance of ligin suspension.Through the cold Membrane experiments, structure and size of the liquid distributor were determined. The results of hot-film experiments show that:within the experimental setting of the spray density (0.321Kg/m/s<г<0.721Kg/m/s), heat transfer film coefficient outside horizontal tubes with the increase of the spray density firstly increases and then decreases. When г=0.534Kg/m·s, the maximum value is obtained; When the spray density, solid content, and diameter are constant, with the temperature difference increasing, heat transfer film coefficient outside horizontal tubes decreases;heat transfer film coefficient outside horizontal tubes also increases with the decreasing of heat flux and solid content.The φ38mm tube has the smallest diameter in the experiment, but the heat transfer coefficient is the highest; The φ57mm having the biggest diameter, gets the minimum heat transfer coefficient, with the contrast of tube diameters, the tube of smaller diameter can obtain the higher heat transfer coefficient. In an evaporation cycle (72h), heat transfer film coefficient outside horizontal tubes decreases by8.6%,the overall heat transfer coefficient decreases by7.6%,showing that the fouling resistance greatly reduces the heat transfer coefficient and is extremely unfavorable. Finally, Set an example of the φ38mm tube with the solid content of19%to do experimental data regression, experimental correlations for horizontal tube falling film evaporator is obtained, the error is within20%.