CFD Simulation Of Dehydration Of Fructose To HMF In Microchannel Reactor

5-Hydroxymethylfurfural(HMF)in furans has six carbon atoms and contains one furan ring,one aldehyde group and one hydroxymethyl group,which makes its chemical properties more active and can be oxidized,hydrogenated and Condensation to prepare a variety of derivatives,is an important fine chemical raw materials.The biomass resource based on lignocellulose is considered to be an ideal candidate for future energy sources.At the same time,lignocellulose can be dehydrated to produce HMF after fructose formation.At present,the focus of HMF research is on catalysts and solvents.There are few studies on the enhancement of the reaction process.The microchannel reactor has a relatively high specific surface area due to its small size,and the enhancement effect in heat transfer and transfer is more obvious.Therefore,the microchannel reactor and fructose dehydration reaction are combined in this paper.This paper mainly studies the process of strengthening the dehydration reaction of fructose in the microchannel reactor from three aspects.First,the effect of solvent,residence time,geometric effect,and thermal effect on the performance of the reactor is considered in the homogeneous reaction process.In the straight channel,when the residence time reaches 4 s,the yield of the intermediate 5-HMF is the highest.The effects of three different reactor geometries on the reaction performance of rough tubes,straight channels and curved channels were compared.The properties of rough tubes>straight channels>curved channels indicate that the decrease in the degree of backmixing is beneficial to increase the yield of HMF..Secondly,the effect of wall temperature and heat flux on the reaction is considered in terms of thermal effect.When the wall temperature reaches 487 K and the heat flux is 150 W/m2,the optimal conditions are achieved at this time.Thirdly,in the process of single-channel to multi-channel amplification,the uniform distribution problem faced by the microchannel reactor during amplification is solved by the Z-shaped structure and the apertured baffle structure.In the Z-type structure,the influence of the inclination angle and the number of channels on the uniform distribution is considered.When the inlet velocity is less than 0.0125 m/s,the Z-type structure can meet the uniform distribution;when the inlet velocity is more than 0.125 m/s,the backflow occurs at the entrance of the passage and the degree of uneven distribution increases.The perforated baffle uses the size of the hole to adjust the distribution of the flow.The adjustment of the size of the perforated baffle is done through iterations.Through the adjustment of the hole,the uniformity can be achieved,but the backmixing degree is larger than the Z-shaped structure.In the investigation of the two-phase flow in the microchannel,the formation and development of the slug flow were studied.The effects of the two-phase velocity,the contact angle and the two-phase velocity ratio on the flow pattern distribution were investigated.When the inlet velocity of the two phases is greater than 0.08 m/s,there is no slug flow in the microchannel and only parallel flows.When the inlet velocity is less than 0.07 m/s,a slug flow is formed in the microchannel,and the position where the first slug flow forms is away from the intersection as the inlet velocity increases.When the wall contact is less than 45°,parallel flow appears in the microchannel.When the contact angle is greater than 60°,the formation of slug flow in the microchannels indicates that the reduction of the contact angle is beneficial to dissipation of the wall energy.The length of the slug flow decreases with the increase of the ratio of the two-phase inlet velocity,and the distance between adjacent two slug flows increases with the increase of the ratio of the two-phase inlet velocity,and it is linearly correlated.In the two-phase mass transfer process,the increase of the inlet velocity,the increase of the ratio of the water phase and the oil phase flow are all conducive to the increase of the mass transfer coefficient.