Research On Pneumatic Conveying System Of PTFE Powder

The Polytetrafluoroethylene(PTFE)material has excellent temperature resistance,corrosion resistance,aging resistance,insulation,flame retardant,self-lubricating and some other characteristics.Therefore,PTFE has been widely applied in many areas,such as aerospace,machinery,electronics and petrochemical industry.At present,PTFE pipe production industry mainly uses artificial feeding methods.This is not only time-consuming,but also prone to dust pollution.Therefore,companies need automated and closed feeding device.However,due to the small particle size and poor flowability of the powder,the powder can be extruded into a group or clog the filter element easily during transport.There has been no efficient and stable automatic feeding equipment for PTFE powder yet.Thus,it is urgent and meaningful to propose a new practical method and develop an automatic conveying equipment for PTFE powder.In order to solve this problem,a structural design scheme of pneumatic conveying system for PTFE powder is proposed.A series of research work has been carried out for the system,including overall technical scheme research,key technical research,control system integration and basic feature test,etc.Firstly,according to the characteristics of PTFE powder and the technical requirement of automatic feeding equipment,the overall technical scheme of automatic conveying system for PTFE powder is studied.On the basis of the basic vacuum conveying system,the structure of the gravity feeding storage-supply subsystem is proposed.Also,the aggregate-discharge subsystem which has the function of cyclone powder separation and cup type HEPA(High-Efficiency Particulate Air)filter separation is developed.The system work flow is analyzed,and main performance parameters of the system as well as the operating parameters of the main components is determined.These lay the foundation for future research and are beneficial to system implementation.Some technical problems in the system have been solved.The method of reverse gas flow for cleaning the filter is put forward,which solves the problem of plugging and short working life of the filter.The experiment shows that the method can greatly improve the service life of the filter to satisfy the system 's demand.Aiming at the problem of material storage and feeding,a technical scheme of valve-controlled intermittent limited supply is proposed and the corresponding skate valve is developed to realize reliable feeding.In order to meet the special technical requirements of the aggregate-discharge valve,a new compact cover valve which is driven by cylinder pendulum multi-bar mechanism has been developed to solve the problem of sealing and preventing friction and wear.According to the functional requirements of the system,the pneumatic control circuit and the electrical control circuit of the system are designed,the required pneumatic and electrical components are selected,and the PLC is programmed.Based on the prototype of the system,the basic characteristics of the system are tested and the mathematical model of powder conveying speed in the system is established.The actual powder conveying speed captured by camera is turned out to be 3.99 m/s.Using the weighing method,the conveying capacity of the system is 206.4 kg/h.Through the long continuous non-standby conveying test,the relationship between the conveying capacity and delivery time is obtained.The recommended service life of the filter is 3 months which has met the technical needs of the system.The pneumatic conveying system developed for PTFE powder can meet the technical requirements of the automatic feeding system.Up to now,the system has been completed and delivered to the enterprise.Users are very satisfied with the machine.