Study On Non-Equilibrium Sorption Performance And Kinetic Models For Chlorides-ammonia Working Pairs

A new type of consolidated composite sorbent for metal chlorides is developed by the matrix of ENG-TSA?Expanded natural graphite treated by the sulfuric acid?.The non-equilibrium sorption performance and kinetic models for composite sorbent of metal chlorides-ammonia working pairs are studied,the process of isobaric sorption and sorption for composite sorbent was tested,and the results showed that non-equilibrium reaction curve for metal chlorides-ammonia working pairs was different from theoretical Clapeyron curve.Furthermore serious hysteresis occurs in the process of desorption.The study on sorption kinetics models for sorption and desorption process showed that sorption model can be fited with D-A equation in the process of sorption,while in the process of desorption the D-A equation and Spinner model both need to be considered.The Arrhenius equation for the relationship between sorption heat and hysteresis temperature difference was derived.Finally multi-salt composite sorbents were tested and analyzed,main conclusions are obtained as follows:?1?Through study on metal chloride sorption performance under the condition of non-equilibrium,results showed that under the same condensation/evaporation condition,the sorption quantity of composite sorbent changes with both pressure and temperature,that is to say non-equilibrium sorption/desorption processes are related with dual variables rather than a single variable,so it has bigger difference with theoretical Clapeyron curve.?2?Test from the isobaric sorption of composite sorbent showed that in the process of sorption non-equilibrium reaction curve was in accordance with equilibrium reaction curve,but in the process of desorption since the difference between activation energy of desorption and activation energy of sorption the serious hysteresis phenomenon occurred.the serious desorption hysteresis happened for 4mol NH₃ mol^-1 MnCl₂,for 7mol NH₃mol^-1 CaCl₂,for 7mol NH₃ mol^-1 SiCl₂,and for 1.5mol NH₃ mol^-1 NH₄Cl.?3?The sorption rate kinetics models were analyzed,desorption hysteresis phenomenon was weakened gradually with the increase of desorption temperature.Arrhenius equation for the relationship between sorption heat and hysteresis Temperature difference was derived,A₀ in this equation is a fixed value,but varies from Metal chloride to Metal chloride,for MnCl₂ A₀ is 18.02,for CaCl₂ A₀ is 18.89.?4?In order to deeply explore the relationship between adsorption heat and desorption hysteresis the sorption rate kinetics models were established,the results showed that sorption model can be fitting with D-A equation in the process of sorption,the constant x₀?k?n for MnCl₂,CaCl₂,NH₄Cl composite sorbent is 0.809,8.66,1.181,1.237,14.09,1.171,1.271,20.15,0.863,respectively,while in the process of desorption it will divided into two parts.The part before the hysteresis point the Spinner model can be used,and the part after hysteresis point the D-A equation is available,but the constants of x₀?k?n are has different values with that for sorption.?5?The isobaric sorption lines of multi-salt composite sorbents are studied,and the results showed that the sorption performance of double-salt composite sorbent is similar with that calculated by the performance of single salt.As condensing temperature increase the hysteresis loop will be smaller than that of single salt sorbents.The triple-salt composite sorbent has a totally difference characteristics,especially for the hysteresis loop,which is much smaller than the single salt sorbent.When the condensation temperature is 0?,desorption process is same with the sorption process,i.e.no hysteresis happens.