Research On Key Technology Of Supercritical CO₂ Dyeing Process Control

During the supercritical CO₂ dyeing process,the slight change of process parameters——temperature and pressure will make the solubility of dyes in supercritical CO₂ change significantly,thus affecting the dyeing quality of fabric.Therefore,it is necessary to control temperature and pressure of the supercritical CO₂ dyeing process precisely.Supercritical CO₂ dyeing process has the characteristics of rapid,multivariable,nonlinear and strong coupling.Accurately controlling temperature and pressure of dyeing is the key technical challenge faced by supercritical CO₂ dyeing production to improve product quality and expand application range.The main work completed in this paper is as follows:1.At present,the supercritical CO₂ dyeing process adopts a single-loop control system for temperature and pressure without considering the coupling relationship between them.During the dyeing process,any parameter change will cause significant fluctuations of other parameters.First of all,in this paper a multivariable model was established in which supercritical CO₂ was used as ideal gas with the inflow and outflow as control variables,and temperature and pressure as controlled variables.Combined with the nonlinear characteristics of the supercritical dyeing process,a corresponding nonlinear decoupling control algorithm was designed.2.The pVT relationship of fluids was analyzed in order to more quantify CO₂fluids accurately.A multivariable model was established in which supercritical CO₂was used as the compressed gas and the inflow and outflow as control variables,and temperature and pressure as controlled variables.In view of the lack of data on the physical properties of dyes,the critical parameters,eccentricity factor,and molar volume of disperse dyes were calculated based on the group contribution rules.On this basis,the corresponding nonlinear decoupling algorithm was designed,and the effectiveness of the model and the decoupling algorithm were verified through simulation experiments.3.Considering the fact that the actual dyeing process contains multiple components——CO₂ fluid and dyes and phase transitions,therefore the interphase equilibrium dyeing model of fluid mixtures containing supercritical components was established,and the related decoupling algorithm was further designed and verified.4.The reason for the isothermal solubility curve showing S-type and the extreme conditions for the occurrence were discussed;Calculating the density of supercritical CO₂ and correlating the solubility data of four different disperse dyes based on the models of Chrastil,M-T,and modified Chrastil to obtain different types of solubility equations and analyzing them.The research results of this paper can provide a practical and feasible control technology solution for accurately controlling the temperature and pressure process parameters of the supercritical CO₂ dyeing process.It is of great significance to advance the control technology of supercritical CO₂ dyeing process and improve the dyeing quality of fabrics.