Design And Research On The High-speed Vertical Screw Mixer For Modifying Bitumen

Modified bitumen membrane is mainly used for building waterproofing,which has a large market.Modified bitumen mixer is the key equipment in modified bitumen membrane production plant.However,the domestic existing mixers have the defects of unsatisfied mixing,inefficient modification,and low production efficiency,which is difficult to meet the production requirements.In this paper,the modification process of bitumen is studied and the design method of mixer is researched in order to find a way of increasing the production efficiency of the mixer,and improving the bitumen modifying quality.The main contents of this paper are as follows:By researching the bitumen modification principle and production technology,conclusions are made that the properties of modified bitumen,such as high and low temperature properties,elongation property etc.,depend on the ratio of asphalt and modifiers,and the asphalt modification effect depends on the sufficient blending of the asphalt and modifier under certain temperature.Thus,the design of the heating,weighing and controlling system of the mixer are determined.The agitating method of a mixer mainly affects its mixing effect,working efficiency and energy costing.This paper presents an idea of replacing the commonly used low speed paddle type mixer with high speed screw type mixer.Comparisons are made by simulating the mixing flow and velocity field of the two types of mixers,with the following results: In the high speed screw type mixer,the compound movement is intense,the flow field is uniform,the axial circulation effect is available,and there's no obvious compound sedimentation at the bottom.The conclusion could be made that the mixing effect of the new high speed screw type mixer is better than the low speed paddle type mixer.For the high speed screw mixer proposed foresaid,this paper researches and determines the screw formality,works out the diameter of agitating shaft,and calculates the required electric power.Based on the design upside,the movement and stress of the materials in the mixer,the force of the screw,the strength and stability of the mixing shaft are analyzed.SolidWorks is used to construct the three-dimensional model of the agitator.The stress,strain and the fatigue strength of the mixing shaft are analyzed with SolidWorks Simulation,and the reliability of the mixing shaft is verified.At last,practical project cases of high speed screw type mixer are presented.The new designed modified bitumen mixer has been put into production,and has gained favorable comment by customers as well as good economic benefit.