Numerical Simulation And Analysis Of Complex Iron Desulfurization Loop Reactor

Chelated iron desulfuration process plays a crucial role in natural gas treatment in an environmental and efficient way,especially for the circumstances to purify acid gas with lower potential sulfur concentration in a small scale.Moreover,the Airlift Loop Reactor(ALR)has advantages in reducing power consumption and enhancing mass transfer efficiency in wide field,such as chemical industry,biological fermentation and waste water treatment.In this paper,computational fluid dynamic,as a research tool,made an analysis on the flow characteristics of gas-liquid and their influence factors.Then further researches of bubble behavior,region and efficiency of mass transfer were also taken into consideration.Later,major investigations have been made on gas-liquid-solid flow as well as the characteristics and the rate of mass transfer and reaction.According to the conditions of operating environment and simulation date in Aspen,a 3D physical model has been built and in consideration of the continuous process,residence time in airlift reactor is 0.1 h and the liquid cyclic velocity is 1.0440 m/s.By introducing the Eulerian multi-phase model,standard k-? model and in consideration of the virtual mass force and drag force to describe the turbulent behavior in gas-liquid,a high-quality mesh and optimized algorithm have been established.A self-circulating flow distribution driven by density difference in a two-distributor ALR is obtained.The influence of operation and structure parameter on gas holdup and liquid circulation velocity indicated that there is obvious dofference in diverse region and there exist "viscous" effect and "break" phenomenon.As a consequence of this,optimized parameters of operation:air superficial velocity(0.8668 m/s)and structure:draft tube diameter(1.1 m)and draft tube height(4.0 m)have been presented.Meanwhile,analyses on bubble size distribution and bubble interface concentration,using population balance model and bubble coalescence and breakage model,illustrate that size of bubble is increasing in riser compared with that stable in downcomer.At the same time,big bubble is dominated and the smaller bubble is,the higher interface concentration is.It performs high mass transfer efficiency in gas injection area and in where turbulent eddy appears.Additionally,middle size of bubble tends to coalescence to large bubble and to keep balance under air superficial velocity at 0.8668 m/s thus a higher air superficial velocity makes an adverse contribution to mass transfer.Based on the characteristics of gas-liquid and behavior of bubbles,models and mechanisms for species transport,mass transfer and reaction have been taken into account to reveal the distribution of reactant and production as well as the rate of mass transfer and reaction.A homogeneous flow distribution,increasing in gas holdup and receding in liquid cyclic velocity have obtained.Analyses indicate that the mass transfer and reaction process mainly take place in small bubble where there exist gas injection and liquid turbulent.The liquid volumetric mass transfer rate mainly effect by gas holdup and liquid equilibrium concentration and the liquid volumetric mass transfer rate of H2S is smaller than that of O2 by I order of magnitude.On the other hand,reaction rate is influenced by concentration of reactant and reaction rate constant and the oxidation reaction rate of H2S is controlled by its liquid volumetric mass transfer rate while the Fe2+ regeneration reaction is limited by the liquid cyclic velocity.ALR have established its illustriousness flow characteristic and efficient rate in mass transfer and reaction with Lo-cat solution.Descriptions and researches on gas-liquid interaction,gas bubble behavior,mass transfer and reaction process in ALR provide a theoretical basis and guidance for application and analysis in nature gas desulfuration.