Research On Air Knife Sorting Technology For Stainless Steel Shredded Materials Of Scrap Car Body

Scrap stainless steel(SS)in shredded materials of scrap cars is worthy of recycling,the research of sorting technology of SS contained in shredded materials can bring high economic value,favorable social and environmental benefits.Air knife sorting is a pneumatic separation technology,air knife is formed of jet stream,and the trail of SS is changed by the impact force that is generated by air knife,then SS is separated from nonmetal.The air knife separator is developed successfully;the research is conducted by numerical simulations and experiments to probe sorting regulations.Basing on the detecting characteristic of SS,the air knife sorting technological process is determined.The materials are transported on a belt,proximity sensors are used to detect objective particles,PLC is used in actions control,in separation mechanism,the sorting action is executed by air knife that is formed with nozzles controlled by solenoid valves.The algorithms,program and electric circuit of the control system is designed.The motion trail of SS particles is calculated basing on theoretical analysis,the theoretical separating point and jet delay is determined.In order to assure the accuracy of time delay,the distance should be set to be adjustable.The time delay setting experiments is conducted,which comes to a conclusion that when the given distance is 30 mm smaller than the theoretical value,the error caused by system response can be reduced effectively and a higher accuracy of time delay and sorting can be reached.Basic jet flow theory is researched,the jet flow field of different nozzles and air conditions is analyzed.The regulation that jet flow velocity,width and jet flow distance vary with these parameters is revealed.The results show that the bigger the export diameter of a nozzle is,the longer core area length is,and the lower exit speed is.When the export diameter is 6mm,the core area length of conical nozzle is 5mm longer then that of cylindrical,and the divergence angle reduces a little.The calculating results of jet width of multiple jets injection field is probably far larger than the size of materials,in order to improve injection accuracy,radial detection range of proximity sensors is adjusted,thus the jet width is reduced.To determine the best location of jet and time delay under different velocities,pre-sorting experiment is conducted.After choosing proper test parameters according to the ones that influent the location of nozzles and designing scheme,the orthogonal experiment is conducted and the testing result is analyzed.The laws that sorting efficiency varies with location of separating mechanism are researched.It draws a conclution that the closer separating mechanism and trails are,the higher sorting efficiency is.The highest accuracy can reach 95% and the lowest one is 71%,the sorting purity is over 80% under every operating condition;The sorting accuracy will decrease when the size of sheet materials increases,for the trail of which is influenced by uncertainty.When the belt velocity is between 1-2.5m/s,the separator can work with a sorting accuracy and purity of 90% through setting a proper location of separating mechanism.