Study Of The Mechanism And Characteristics Of Transport And Conversion In A Bionic Flexible Fluid-induced Peristaltic Reactor

As a clean and efficient renewable energy source,biomass energy has significant energy-saving and emission-reducing effects and is expected to become an important alternative to fossil fuels in the future.In the process of biomass conversion and utilization,it usually needs to be carried out under high concentration of biomass to ensure high product concentration,reduce the cost of product separation and purification later,and improve the overall economic feasibility of the process.However,as the concentration increases,the free water content of the system decreases dramatically,leading to an increase in the mass transfer resistance between the catalyst and the substrate,which not only reduces the accessibility between the substrate and the catalyst,but also leads to a local accumulation of products and a decrease in the conversion rate.Mixing can significantly lower the mass transfer resistance,increase the accessibility between substrate and catalyst,and further reduce the amount of catalyst.At the same time,it can make the products leave the reaction system in time,promote the positive reaction and increase the product concentration.In this paper,based on the bionics,we designed a bionic flexible flow-induced peristaltic reactor based on the characteristics of the digestive tract of insects and herbivores that can degrade biomass efficiently in nature,to achieve gentle and efficient mixing of high-concentration substrates,eliminate the mixing dead zone and improve the conversion rate.By establishing a three-dimensional peristaltic model with higher accuracy and solving the two-way fluid-solid interaction efficiently with the separation solution method,the mechanism of enhanced heat and mass transfer and reaction by flexible wall peristalsis was investigated,and the effects of different operating parameters and substrate properties on the reactor performance were explored to provide theoretical guidance for the optimal design of reactor.Then,the feasibility of bionic flexible flow-induced peristaltic reactor was verified by the experimental study of biodiesel production from converted soybean oil,and the results were compared with the simulation and previous literature.The main results are as follows.（1）The increase of peristaltic section length（3 cm-7 cm）and peristaltic period（0.5s-2 s）decreased the mixing performance of peristaltic reactor by 54.5%-66.7%and16.9%-25.1%,respectively,and the increase of peristaltic amplitude（7.5%-50%）increased the mixing performance by 92.5%-100.8%.The increase of fluid viscosity decreased the mixing performance of the reactor,and compared with the traditional rigid reactor,the flow peristaltic reactor has better-enhanced mixing performance for high-viscosity fluids.The temperature distribution of peristaltic reactor was more uniform than that of rigid tubular reactor.（2）The largest Lyapunov exponent（LLE）within the flow-induced peristaltic reactor was twice that of the conventional rigid reactor,which had stronger chaotic mixing and lower mass transfer resistance.The increase of peak pulsation pressure can effectively increase the LLE in the flow-induced peristaltic reactor,while the increase of peristaltic section length and peristaltic period significantly decreased the LLE.Compared with the conventional rigid reactor,the solid-liquid flow in the flow-induced peristaltic reactor was more uniform and the probability of particle agglomeration was smaller.Variations in solid particle size（in the micron range）and fluid viscosity had a weak effect on the particle distribution in the flow-induced peristaltic reactor.（3）The biodiesel conversion in the flow-induced peristaltic reactor increased with the increase of alcohol-oil molar ratio and then leveled off.The conversion increased with the increase of temperature,but the positive correlation between temperature and biodiesel conversion also depended on the interaction with other reaction variables.The biodiesel conversion in the flow-induced peristaltic reactor gradually decreased with the increasing peristaltic period and increased with increasing peristaltic amplitude.Compared with the conventional rigid tubular reactor,the biodiesel conversion in the peristaltic reactor was higher and the enhanced reaction performance of peristaltic reactor was better.（4）The experimental results of the conversion of soybean oil to biodiesel showed that the conversion rate of biodiesel was 62%for 3 h in the batch treatment,54.5%for12 s in the rigid tubular reactor,and 89.9%for 10 s in the bionic flow-induced peristaltic reactor.The experimental results were within 15%of the simulated junction,which was in good agreement and proved the reliability of the simulation results.The conversion rate within the peristaltic reactor was 528 min^-1,which was 17-60 times higher than that traditional rigid reactor reported in the literature,demonstrating the superior enhanced reaction performance of flexible peristaltic reactor.