Conceptual Design Of The Bionic Reactor With Distributed Input And Output Flow Channels

The Bionic Reactor is novel unconventional fixed bed reactor proposed by the research group,and its configuration design is inspired by the mammal circulation system.It has hierarchical distributed input(artery)and ouput(vein)flow channel network and its catalyst bed size is as small as centimeters or even millimeters so as to reduce pressure drop.Its channel structure and framework can be used to enhance bed heat transfer.The application purpose of the Bionic Reactor is to use fine catalysts to eliminate intra-and inter-particle diffusion resistance,uniformize reaction load,improve efficiency,and in the meantime,to realize the miniaturization,modularization and integration of fixed bed reactor.So far,this kind of reactor concept and configuration have not been reported.Several Bionic Reactor implementations for different production scales were proposed in this thesis,and the structure of elementary unit and higher levels were designed.The distribution uniformity of infiltration velocity and temperature were taken as criteria of the optimal design of the elementary unit.Based on the Constructal Theory,the Bionic Reactor was optimized in order of particle scale,channel and bed scale,and higher level scale.The Bionic Reactor is suitable for fast and highly exothermic gas-solid catalytic reaction with different production scale.Several typical petrochemical and coalchemical industry application cases were analyzed to further demonstrate the concept and design methodology of the Bionic Reactor,and lay the foundation of the industrialization of this kind of reactors.The contents of this thesis include following aspects:1.Concept and implementation of the Bionic Reactor.The novel Bionic Reactor with distributed input and output flow channels was proposed,and so were 4 typical Bionic Reactor implementations,including the Honeycomb micro packed bed,the Metal plate micro packed bed,the Multi-layer radial bed,and the Multi-layer inclined bed.The Honeycomb Micro packed bed is a small scale modular Bionic Reactor manufactured by processing,packing and sealing of the honeycomb ceramics with permeable walls.Its advantages are low pressure drop,good heat transfer performance,simple manufacture and scale-up process.The Metal plate micro packed bed is a small scale modular Bionic Reactor with built-in heat exchanger.It is manufactured by lamination and brazing of metallic sheets.Its advantages are extraordinary heat transfer performance,small reactor volume,and high integreation level,and is suitable for small scale production in mobile devices.The Multi-layer radial bed and the Multi-layer inclined bed are constituted by coaxial annular and inclined channels and beds,respectively.Their advantages are low pressure drop,uniform distribution of infiltration velocity,and simple structure,and is suitable for large scale industrial production.2.Flow distribution uniformity criterion of the Bionic Reactor.The coupled mathematical model between free channel flow and porous media infiltration was established for the Bionic Reactor elementary unit.The model equations were expanded and solved by the use of radial distribution function,and 2 charactersitic dimensionless parameters,Rew and Pr,that determine the axial distribution uniformity of infiltration velocity were obtained.Rew is the bed infiltration Reynolds number,and the physical significance of Pr is the pressure drop ratio between the channel flow and the bed infiltration.The model equations were simplified by radial integral average,and the analytical solution was obtained for axial distribution of the pressure difference between the input and output channels in the elementary unit.The flow patterns in the elementary unit include z and ? patterns.The analytical solution gave that for z pattern,when Rew<1.3,the distribution type of infiltration velocity is concave with internal minimum,when Rew?1.3,it is monototic ascending,while for ? pattern,it remains monototic descending.The distribution uniformity criterion of the infiltration velocity was quantitatively estimated by the relative maximal difference ?max,which is propotional to Pr for different range of Rew,indicating that Pr is the key parameter that determines the distribution uniformity.When Rew is large enough,there are?max=1.5Pr and ?max=0.5Pr,respectively for z and ? patterns.3.Heat transfer characteristics of the Bionic Reactor.Taking Honeycomb micro packed bed as object,3 dimenional mathematical model was established for momentum,mass and energy transfer.The numerical simulation results showed that the non-uniformity of bed temperature was mainly caused by axial channel temperature difference.Heat convection is dominant in flow channels,and the axial channel temperature difference increases with the channel length,and decreases with the channel width.Heat conduction is dominant in catalyst bed,the bed temperature difference can be significantly reduced by increasing the framework heat conduction area.For narrow flow channels,the axial bed temperature difference is significantly affected by the value of Pr,that is,the axial non-uniformity of infiltration velocity.The maximal bed temperature difference can be nearly halved by add back-turning input channel.The catalytic combustion of lean methane was selected as application case.Cold feed was used to neutralized the reaction heat,and the sizes of catalysts,channels and beds were optimized to maintain the maximal bed temperature under 50?.Since the auto-thermal function was realized,the thermal storage media were saved,the catalyst loading capacity was more than doubled,and the catalyst dosage and reactor volume were significantly reduced.4.Application cases study of the Bionic Reactor.Based on the detailed structure of Honeycomb and Metal plate micro packed bed,the modified expression of the flow distribution characteristic parameters were given.By numerical simulations of Multi-layer radial bed,the central channel diameter condition for annular channels and beds to be equivalent to rectangular ones were obtained.By numerical simulations of Multi-layer inclined bed,the best channel inclination to achieve uniform infiltration velocity distribution were obtained.The structure and size were designed and optimized for several application cases based on flow and temperature distribution uniformity critertion.Flue gas denitrification reactor adopted Honeycomb micro packed bed.The oxidation and SCR catalysts were packed in order in catalyst channels to realize compact process of NO pre-oxidation and SCR.0.21mm and 0.16mm fine catalysts were packed with 1119.4Pa total pressure drop.In secondary level structure with 40cm channel length,the catalyst packing fraction is 53.44%,much higher than monolith reactors.The auto-thermal reforming of methane adopted SiC Honeycomb micro packed bed with back-turning input channel.0.2mm fine catalysts were packed with 3000Pa total pressure drop.Under higher methane feed concentration and lower steam dilution ratio,the bed temperature was controlled under 80?,the methane conversion was 95.3%.The catalyst packing fraction of the elementary unit was 49.4%.The CO preferential oxidation adopted Metal plate micro packed bed,and the heat transfer was enhanced by metal framework and internal heat exchanger,so the bed temperature was maintained properly between 180?200?.O.1mm fine catalysts were packed with 4950Pa total pressure drop.The catalyst packing fraction of the elementary unit was 59.5%,and comparing to microchannel reactor,the reactor volume was saved by 40.2%.The methanol to propylene process adopted Multi-stage multi-layer radial bed.(?)1.2×0.4×4.8mm hollow cylinder catalysts were packed with 0.03MPa total pressure drop.The steady state maximal propylene selectivity was 13.56%higher than that in Lurgi fixed bed,and the catalyst dosage was saved by 56%.The gas phase Beckmann rearrangement adopted Multi-layer inclined bed as deep conversion reactor.(?)1×2mm cylinder catalysts were packed,and under the high gas flowrate condition of prepositive fluidized bed outlet,the total pressure drop was 0.22atm.The conversion of cyclohexanone oxime reached over 99.95%.