Research Onpulverized Power Mass Flow Online Measurement Technique And Its Application

Pneumatic transporting powder process is a typecal gas-solid two phase flow.Mass flow measurement of powder is an industrial problem urgent need to solve,because of the instability of flow pattern.Powder mass flow detection based on capacitance is most applicable and common.The invariance of the solid phase's permittivity is deemed to be the premise of capacitive phase concentration detection.Detection accuracy of mass flow was reduced due to change of dielectric constant by temperature,humidity and powder ratio.Powder mass flow detecting technology needed to be researched.This thesis was set in the characteristics of Liu Steel's 2#blast furnace,pulverized coal mass flow measurement system with dielectric constant of solid state medium compensation.Methodof pulverized coal mass flow detection with soft measurement was researched.Error of dielectric constant of powder changing was reduced.The main work of this thesis is showed as follows,(1)In Liu steel's 2#blast furnace,pulverized coal transmission distance is far,flow pattern of pulverized coal is unstable,coal powder dielectric constant is not fixed.Online detecting system was proposed based on capacitance sensor.Compensating sensor was added to get coal powder dielectric constant.Compensation effect on change of dielectric constant with dual sensors was analysed.(2)The model of mass flow measurement was established by multiple regression fitting.The output variable was determined by calculating instantaneous mass flow of electronic scale,the input variables were determined by regression analysis and process mechanism analysis.Effectivehistoricaldata was filtered to build detecting model though injecting tank pressure stability.The segment boundaries were determined by injecting tank pressure though technique nonlinear data.(3)System deviation threshold was determined by demand.Online correction time was determined by the time system detection value deviation exceeds the threshold value.Injecting tank pressure,valve opening and injection setting were judgment basis.Historical data was selected to rebuild detecting model by regression fitting.(4)A dual sensor detection scheme is proposed.Derived by formula,concentration was only related to two sensor detection capacitance and calibration parameters.The error caused by the change of dielectric constant can be eliminated by compensating sensor.Timing of dielectric constant compensation was judged by tank weight,tank pressure and valve under the state.(5)Low correlation between the upper and lower velocity signals was found by cross correlation analysis.Speed improved algorithmobtained.Similar peaks was searched by comparing the height and width of the signal peaks of the upper and lower reaches.Transit timewas found by calculating the average value of the difference between the wave crest velocity.Speed calculation was implemented.(6)Installation scheme was determined according to the site conditions in Liu Steel.The wear resistance and insulation of thecompensating sensor was ensured.The scheme of Liu Steel's database reading and IP address allocation was proposed.Reconnection and singlechiprestart was proposed to ensure stablity of long distance communication.