Research On The Movement Characteristics Of Waste Based On Pneumatic Conveying Theory

With the gradual improvement of people’s living standards,the amount of household waste has increased rapidly.However,the structure of the domestic labor force is gradually differentiated,and the trend of aging is emerging.The traditional manual mode for waste collection and transportation has suffered from the problems including high labor intensity,low efficiency,environment impact and secondary pollution,leading to an urgent need of upgrading.The waste pneumatic conveying technology will be an attractive solution for the mode upgrade because of its advantages including high degree of automation,enclosed transport,and flexible conveying of multiple materials,etc.At present,the waste pneumatic conveying technology has been mastered and commercialized by some developed countries,while the domestic basic research on this technology is still in its infancy.This project is titled "Key technology of waste pneumatic conveying-Research on waste movement characteristics based on pneumatic conveying theory".In this study,some basic research has been made on the domestic waste pneumatic conveying technology,using the method of combining theoretical calculation,simulation analysis and experimental verification.Accomplished research activities include(a)definition of the physical properties of urban domestic waste and the acquisition of the key parameters of movement characteristics,(b)research on the movement characteristics of a large volume material pneumatic conveying and the movement characteristics of materials with irregular shape under the condition of pneumatic conveying,(c)further verification and analysis of the obtained data through experiment.The main investigations and results of this project are as follows:(1)Survey of the waste compositions,classification and recycling policy,disposal method,and application status of waste pneumatic conveying at home and abroad;clarification of the domestic waste composition and their physical properties under pneumatic conveying conditions.It is concluded that the parameters such as waste composition,density,comprehensive resistance coefficient,rolling friction coefficient and shape factor are the definition parameters of waste physical properties that are crucial for pneumatic conveying technology.These parameters are also necessary for the calculation of waste movement characteristics.Domestically,organic waste accounts for 61.34%(the reference density is 1100kg/m3),which is higher than the average level of urban domestic waste in the world.Organic waste is regulated waste,of which recyclable waste accounts for 31.95%.Wastepaper,plastics,and fabrics are the main raw materials for pneumatic conveying of solid waste,and the reference material densities are 950kg/m3,1200kg/m3 and 800kg/m3,respectively.After classification,the density of different types of conveyed waste is in an interval between 259.82 and 1200kg/m3,and this interval is used as the density range in this study.(2)Starting from the study of the physical properties of waste,the research is carried out through three aspects: the theory of pneumatic conveying and movement characteristics of waste pipelines,the simulation of movement characteristics,and the test of movement characteristics.(a)The theoretical calculation of waste pneumatic conveying technology is studied.The gas flow fields,engineering pipelines and physical properties of conveyed materials are the main targets of the study.Through the research on the theoretical derivation of key parameters of waste pneumatic conveying and its movement characteristics,the theoretical basis for the rational calculation of the pneumatic conveying is provided.(b)The simulation technology of waste pneumatic conveying technology is studied.Through the supercomputing cluster system and the 6DOF+UDF overlapping grid module,the interactive calculation of the movement of the waste and the gas flow field is realized;A calculation method suitable for the simulation of waste pneumatic conveying is developed,and the parallel calculation of waste pneumatic conveying simulation under different working conditions is realized.The analysis and correction of the simulation data with respect to the test data and the experimental verification are completed.The verification data and the theoretical prediction have good regularity and consistency(c)The movement characteristics of waste pneumatic conveying technology is studied.Through no-load and load tests,the collection and extraction of test data are completed,the calculation and analysis of key parameters of waste movement characteristics are completed by using the combined technology,and the key parameters such as drag coefficient,number of velocity heads lost for the particular bend,elbow equivalent,comprehensive resistance coefficient,shape factor,rolling friction coefficient,material movement balance speed and initial speed under different working conditions are obtained.The subject focuses on the conveyed materials and their motion states and completed the single material experiment and the multi-body material investigation experiment,as well as the verification and analysis of the theoretical data.The data shows that: under similar dynamic environment,with the increase of volume of materials of the same density or the increase of density of materials of the same volume,the difficulty of conveying increases,and the possibility of blockage increases.Under the determined dynamic environment,there will be a relatively clear boundary for the volume and density of the conveyed material.The movement acceleration of the conveyed material is not only related to the volume and density of the material itself,but also has a certain relationship with its initial speed.The shape of the conveyed material will affect the conveying motion,so the shape coefficient of the bulk material is an integral part of the study of the movement characteristics.The experimental data obtained above are consistent with the theoretical basis.This research is based on the following three aspects: the physical properties of waste,the parameters of waste movement characteristics under the condition of pneumatic conveying,and the engineering influencing factors constitute the relevant factors of conveying engineering.This study revealed the motion law of waste in the pneumatic conveying environment,and further verified and analyzed the movement characteristics of waste through experiments.It is also studied on how to obtain the key parameters of waste pneumatic conveying and movement,which can also be used as a guiding basis for similar projects.