| Chemical industry is a basic industry covering the national economy and people’s livelihood,which is of great strategic significance to promote national economic development and social progress.China’s chemical industry has the characteristics of starting behind and rapid development.China’s chemical industry is now in a critical period of transformation from the model of large-scale and rough to the model of miniaturization,refinement and sustainable development.However,problems such as low mass transfer efficiency,huge reactor volume,poor controllability and high equipment investment and operation cost exist in the conventional reactors such as stirring tank,tower equipment and fluidized bed,which greatly limit the transformation of China’s chemical industry to achieve the goal of green and sustainable development.In order to solve the above problems,helping China’s chemical industry to achieve leapfrog development.Based on the idea of process intensification technology,according to the characteristics of different chemical fields,scholars have developed process intensification equipment such as micro-reactor,rotating packed bed,ultrasonic wave reactor and high-speed shear reactor.To some extent,these devices have been successfully applied in the related industries instead of the traditional reactors,which have significantly promoted the long-term development of China’s chemical industry.At the same time,for the process intensification equipment,there is still ample room for improvement in mass transfer efficiency,handling capacity and applicability in complex multiphase flow system,so it is extremely urgent to improve and develop the new process intensification equipment.In order that further improving the mass transfer performance and handling capacity of the reactor,and its applicability in complex multiphase flow.Based on the idea that the mixing efficiency,mass transfer efficiency and handling capacity could be significantly enhanced under high speed shear field and in a confined space,anew type of rotor-stator spinning disc reactor(RSSDR)is proposed.In order to understand the performance of RSSDR,visualization technology and electrical conductance technique are used to study the hydrodynamic characteristics of RSSDR.In view of the fluid characteristics such as velocity field distribution and liquid holdup rate in the reactor,which are difficult to be obtained by visualization technology,computational fluid dynamics(CFD)is used to simulate and calculate the velocity field distribution and liquid holdup rate in the reactor,which provides theoretical support for optimization and scale-up design of the reactor.In addition,to clarify the characteristics of the mixing efficiency and mass transfer in the RSSDR,the parallel competition reaction system of iodide and iodate is used to study the characteristics of micromixing and its estimated micro-mixing times.A liquid-liquid two-phase mass transfer model is established and the mass transfer characteristics of RSSDR are analyzed by using the phosphoric acid-TBP extraction system.Based on the in-depth understanding of the hydrodynamics characteristics,mixing and mass transfer of RSSDR,the application of RSSDR to the extraction of chromium(Ⅲ)from aqueous waste solution and the enhancement of pre-lipidation of free fatty acids are studied.The main conclusions of this work are as follows:1.The fluid flow characteristics in RSSDR are studied systematically.Two typical flow patterns are obtained in the rotor-stator cavity.The influence of variable parameters on the liquid-liquid flow and liquid holdup are investigated,and the dimensionless transition criterion equations of the flow pattern and liquid holdup are established.It is proved that the average droplet diameter decreases with the decrease of rotorstator distance and liquid velocity,increasing of the rotational speed and liquid viscosity in the cavity zone.The relation between the average droplet diameter and the variable parameters is presented as follows:d=123.89N-0.78Q0.17H0.15μ-0.24.In addition,the relation between the average diameter and the mean energy dissipation rate is shown as follows:d=0.60(εm)-1.55.It shows that the higher the mean energy dissipation rate is,the smaller the average droplet diameter is.What more,it is found that the R-R distribution fits well with the distribution of droplet cumulative volume,and the value of the distribution width m range is 7.0-16.62,which is much higher than conventional equipment,indicating that the liquid has a better uniformity and plays an important role in the control of droplet size and distribution in the RSSDR.The empirical correlation of the liquid residence time in the rotor-stator cavity is developed as follows:T=1560N0.86Q-0.79H0.32μ0.23.The experimental data agree well with the theoretical values of the liquid residence time calculated by the empirical correlation.2.The two typical flow patterns is proved by the CFD method in the RSSDR.The simulation data show a good agreement with our previous visual experimental results.It proves the reliability of the model and method selected by our simulation work.In addition,aiming at the characteristics of liquid velocity field distribution and liquid holdup rate in RSSDR which are difficult to be measured by visualization and other experimental methods,the relation between different parameters and the liquid velocity field distribution and liquid holdup rate in RSSDR are simulated using CFD method.The liquid velocity and radial velocity increase with the increase of rotational speed and initial liquid velocity,decreasing with the rotor-stator distance.While due to the influence of gas disturbance,both the liquid velocity and radial velocity will decrease slightly near the outer edge of the rotor-stator cavity.However,due to the inlet effect,the radial velocity of liquid would decrease rapidly near the inlet.In addition,the liquid holdup rate of organic phase in RSSDR is slightly higher than that of water.And both of them are kept constant at first and then sharply decrease with the increase of rotational speed and rotor-stator distance,while they first increase and then remain stable with the increase of liquid flow rate.3.In the investigation of the micro-mixing of the RSSDR,it is found that the micro-mixing effect will be enhanced by decreasing the rotor-stator distance,reactant viscosity,and acid concentration,increasing the rotational speed.While,the micro-mixing effect will be enhanced and then weakened with the increase of reactant velocity.The relation between the segregation index and estimated micro-mixing times is simulated by the Runge-Kutta function in the RSSDR as follows:tm=(XS/60.01)1.12.The estimated micro-mixing times of RSSDR are in the range of 10-5-10-3s,which is less than that of other conventional reactors(10-310-1s).The results show that RSSDR is a promising equipment for process intensification with excellent mixing performance.4.In the study of the mass transfer of the RSSDR,the calculation model of volumetric mass transfer coefficient is established based on the law of mass conservation.It is found that the extraction efficiency and volumetric mass transfer coefficient are improved by increasing rotational speed and the decrease of rotorstator distance,leading to the enhanced mass transfer.The maximum value of volume mass transfer coefficient and extraction efficiency in RSSDR are 1.49×10-2s-1(one order of magnitude higher than the rotating disk tower)and 98.8%,respectively.And the mass transfer effect of spiral-grooved rotor disc is better than that of the smooth rotor disc,which confirms that the etching pattern on the disc surface helps to strengthen the mass transfer.In addition,the extraction efficiency and volumetric mass transfer coefficient of the spiral-grooved rotor disc and smooth rotor disc in RSSDR are obtained by fitting,respectively.The correlation equations with the relevant parameters are as follows:Spiral-grooved rotor disc:η=1.78ω0.51Q-0.16V-0.32 KLa=0.15ω9.77 Q0.18V-2.75 Smooth rotor disc:η=5.34ω0.49Q-0.18V-0.83 KLa=1.02ω1.79Q0.45V-2.935.In the extraction of chromium(Ⅲ)from aqueous waste solution experimental system,it is found that the maximum values of extraction efficiency and volumetric mass transfer coefficient are 97.2%and 0.40s-1 in RSSDR,respectively.It proves that RSSDR is a promising process intensification equipment for extraction of chromium(Ⅲ)from aqueous waste solution.In addition,an analysis on the relationships between volumetric mass transfer coefficient and various parameters is launched by the grey correlation method.It is obtained that the order of influence on volumetric mass transfer coefficient is rotor-stator distance,concentration of chromium(Ⅲ),liquid flow rate,and rotational speed,respectively.6.In the investigation of enhancing the pre-esterification of free fatty acids by RSSDR.The effect of different parameters on the esterification efficiency are studied,and the process parameters are optimized.Under optimal parameter conditions,it shows that the maximum value of esterification efficiency is 99.37%.And the RSSDR has the super productivity and esterification conversion ability(31.6)than that of the conventional esterification reactors(4.48).Therefore,the RSSDR is proved as an effective esterification reactor used to enhance the pre-esterification of free fatty acids. |
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