Performance Study Of Column Tray And Application Of Ionic Liquids In Absorption Process

Column is one of the most important separation equipment,widely used in separation processes such as oil refining,chemical engineering and pharmaceutical.As the most important column internal,the structure and performance of the column tray directly affects the capacity,energy cost,operating flexibility and product quality of the column equipment.In addition,due to the wide usage of column equipment and high energy consumption,even a small increase in the performance of the column internals can bring huge energy saving.Therefore,the research and improvement of the tray has always been one of the key points for energy saving and consumption reduction in the chemical engineering.In this paper,the cold mold experiment of the flow-guiding tray was carried out,and its hydrodynamics and mass transfer performance were measured.The two-phase flow field on the tray is simulated by Computational Fluid Dynamics(CFD).Based on the simulated results,a quantitative design model of the flow-guiding hole was proposed for the first time,and the design model was applied in the experimental equipment and industrial equipment redesign.This paper also applied the CFD technology to the structural optimization and improvement of the sieve-fixed valve.What's more,we also design a new kind of vertical tray.The ionic liquid is called "green solvent".In this work,ionic liquid[BMIM][Tf2N]was applied for the absorption process of esters in flue gas(CO2),and its thermodynamic properties were also studied in depth.The main work and results are summarized as follows:1.Hydrodynamics experiment:The plexiglass column with an inner diameter of 476 mm was used to test the hydrodynamics performance of the flow-guiding sieve tray,the sieve-fixed valve tray and the novel vertical tray,including pressure drop,weeping,entrainment and clear liquid height.In addition,the mass transfer efficiency of the experimental trays was measured using the oxygen-enriched water-air(O2-Air-Water)system.2.Establishment of CFD model:Based on mass conservation and momentum conservation,a basic CFD model was established.The experimental data of the clear liquid height on the tray were fitted and regressioned.Furthermore a new average gas phase volume fraction expression was obtained,which is combined with the Bennett relationship.Finally an interphase momentum transfer term was obtained.In the CFD simulation,UDF was used to modify the two-phase momentum transfer of the CFD model,so that the model has better adaptability to different trays.3.Propose the quantitative design model for the flow-guiding hole.In the CFD simulation of the flow-guiding sieve tray,a closed domain above the tray was constructed,then a math-physical equation was established based on the momentum conservation,which including the effect of these flow-guiding holes and the tray's resistance.With the aid and data of the CFD results,the math-physical equation was solved obtaining two hydrodynamics parameters.These paramters was used to build the quantitative design model.Finally,the applicability of the model was verified in experimental and industrial scale.4.Improvement of the sieve-fixed valve tray.In order to reduce or avoid the liquid back mixing and retention phenomenon above the valve,optimize the two-phase distribution,an improved plan was proposed.And the hydrodynamic experiment and CFD simulation of the this tray before and after the structural change were carried out.5.According to the design idea of the composite tray,the vertical sieve tray and the structured packing were combined to develop a novel vertical tray.As a partial structure of the vertical cap,the structured packing was arranged above the cap to promote and optimize the two-phase contact.The hydrodynamics experiment of the new tray was carried out,and a dry-plate pressure drop model of the tray was proposed according to its structural characteristics.The CFD simulation was also used to simulate the two-phase flow on the tray,providing basic data and information for the design and further optimization.6.The COSMO-RS model was used to screen out the ionic liquid[BMIM][Tf2N]suitable for the absorption process of ester gases.Combined with quantum chemical calculations,the separation mechanism was revealed from the microscopic molecular level.The vapor-liquid equilibrium(VLE)data of the three esters(ethyl acetate,ethyl propionate and butyl acetate)and[BMIM][Tf2N]binary mixture were determined and compared with the calculation results of the UNIFAC-Lei model.In addition,absorption experiments of three esters with[BMIM][Tf2N]as the absorbent was performed.And the parameters of UNIFAC-Lei model and physical properties of ionic liquid were inputted into the software Aspen Plus to simulate the process.In addition,the absorption of methanol and DMM by IL[EMIM][BF4]was investigated systematically.