Spatial reaction engineering approach as an alternative for nonequilibrium multiphase mass‐transfer model for drying of food and biological materials

Drying is a complex process which involves simultaneous heat and mass transfer. Complicated structure and heterogeneity of food and biological materials add to the complexity of drying. Drying models are important for improving dryer design and for evaluating dryer performance. The lumped reaction engineering approach (L‐REA) has been shown to be an accurate and robust alternative for cost‐effective simulations of challenging drying systems. However, more insightful physics has to be shown spatially. In this study, the REA is coupled with the standard mechanistic drying models to yield the spatial‐REA (S‐REA) as nonequilibrium multiphase mass‐transfer model. The S‐REA consists of a system of equations of conservation with the REA representing the local evaporation and wetting rate. Results of the modeling using the S‐REA match well with the experimental data reported previously. This is the first comprehensive REA approach to model the profiles of water vapor concentration during drying of food and biological materials. This study indicates that the S‐REA can be an accurate nonequilibrium multiphase mass‐transfer model with appropriate account of the local evaporation rate. The overall REA concept is expected to contribute substantially for better and cost‐effective representation of transport phenomena of drying process. © 2012 American Institute of Chemical Engineers AIChE J, 59: 55–67, 2013     

Effect of agitation on the fluidization behavior of a gas–solid fluidized bed with a frame impeller

The effect of agitation on the fluidization performance of a gas–solid fluidized bed with a frame impeller is experimentally and numerically investigated. A 3‐D unsteady computational fluid dynamics method is used, combining a two‐fluid model and the kinetic theory of granular flow. The rotation of the impeller is implemented with a multiple reference frame method. The numerical model is validated using experimental data of the bed pressure drop and pressure fluctuation. Although the minimum fluidizing velocity and bed pressure drop are independent of the impeller agitation, a sufficiently high agitation speed yields higher fluidization performance with reduced bubble diameters and internal circulations of particles. The fluidized bed can be divided into three zones: inlet zone where the gas distribution plays a major role, agitated fluidization zone where the impeller agitation has a positive effect on fluidization, and free fluidization zone where the impeller agitation has no effect on fluidization. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1066–1074, 2013     

CO2 capture in a multistage CFB: Part II: Riser with multiple cooling stages

A 1 m in diameter and 3.55 m tall fluidized bed riser internally with water tubes, which required six equilibrium stage of riser‐sorber for capturing about 95% of CO₂ emitted from a coal power plant, were designed to replace the multisingle risers. At the optimum operating condition, the temperature of the cooling tubes in the bottom, the middle and the top of the riser were kept constant values at 50, 40, and 30°C, respectively. The hot water (57°C) from lowest exchanger section can be used to preheat the spent sorbent for the regeneration in a downer. The rest of the heat for the regenertion is obtained from the stack gas (100–130°C). This new concept promises to reduce the energy consumption for CO₂ removal from flue gas. The only energy requirement is for pumping fluid and fluidizing particles in the bed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5280–5289, 2017     

喷雾干燥法制备PS-PVD用8YSZ纳米团聚粉末

目的 通过喷雾干燥法制备用于等离子喷涂-物理气相沉积法（Plasma Spray-Physical Vapor Deposition,PS-PVD）多相沉积柱状/致密涂层的ZrO2-8%Y2O3 (8YSZ)纳米团聚粉末。方法 采用平均粒度为20 nm的8YSZ纳米粉为原料并配制成浆料,球磨后通过喷雾干燥法制备出8YSZ的纳米团聚粉末,并研究不同含量粘结剂（NJ-3）对粉末的影响。利用TEM、SEM表征粉末及涂层的微观结构。通过XRD、激光粒度及拉伸试验对粉末及涂层性能进行表征。结果 纳米8YSZ粉末在添加适当种类及含量的分散剂、粘结剂并通过喷雾干燥加工后,成功制备出球形度高、粒度小且适用于气/液/固多相沉积的PS-PVD用喷涂粉末。当粘结剂含量低于8%时,粉末球形度低,表面存在明显坑孔。而当粘结剂含量高于12%时,PS-PVD气相沉积效率低,涂层质量差。当粘结剂含量为10%时,粉末球形度高,D90=12.24 μm,可气/液/固多相沉积制备形貌良好的柱状涂层及致密涂层。其中气相沉积所制备柱状涂层结合强度可达33 MPa,且原始粉末中的m-ZrO2完全转变为t-ZrO2。结论 当粘结剂含量为10%时,所制备粉末能够流畅送粉,并进行气/液/固多相沉积,且涂层质量最优。粘结剂在粉末内部分布均匀,并主要起粘结和支撑作用,同时可改善粉末表面形貌。喷雾干燥后粉末粒度随着粘结剂含量增加而增大,但非线性变化。     

多相流量计的现状以及发展趋势

阐述了井下多相流量测量技术发展现状,介绍了流量计的发展方向,以此来优化产量,实现更好的制定油田的采油工艺,确定最有价值信息,以及对油藏管理做出更迅速的反应,对重油开发和智能完井具有指导意义。     

3D打印用聚氯乙烯多相复合体系的开发

采用高分子类增塑剂乙烯-乙酸乙烯酯共聚物(EVM)替代聚氯乙烯(PVC)传统增塑剂,制备出具有双连续相结构的PVC/EVM/聚乳酸(PLA)共混物.通过热分析、流变学测试及微观形貌观察等研究了共混物结构与性能间的关系.结果表明,随着填料蒙脱土(OMMT)或碳纳米管的加入,PVC/EVM/PLA共混物的热分解温度和体系燃...     

铈锆复合氧化物催化HCl氧化中相互作用机制

采用浸渍法制备了不同负载量的ZrO₂/CeO₂·（xZr/Ce）和CeO₂/ZrO₂·（yCe/Zr）两组催化剂。并采用XRD、Raman、N₂-Sorption、TEM和H₂-TPR等手段对xZr/Ce和yCe/Zr的结构和性质进行表征,并结合HCl催化氧化活性研究CeO₂与ZrO₂在反应体系中的相互作用。结果显示,CeO₂表面掺杂适量的Zr⁴⁺可以增加xZr/Ce表面氧空位浓度,提高其HCl氧化反应活性;但当CeO₂表面掺杂过量的Zr⁴⁺,Zr元素会以ZrO₂的形式存在于xZr/Ce表面,覆盖氧空位,降低了xZr/Ce的反应活性。对于yCe/Zr催化剂,ZrO₂表面高分散的CeO₂有利于催化活性的提高,但ZrO₂表层负载的CeO₂对催化活性的贡献具有阈值,当CeO₂负载量超过10%后,额外增加的铈物种对催化活性已无显著促进作用;对比发现xZr/Ce的氧空位主要来自于铈锆固溶体,yCe/Zr的氧空位主要来自于高分散的CeO₂,由铈锆固溶体产生的氧空位对活性提升更有利;与纯组分CeO₂相比,xZr/Ce与yCe/Zr两组催化剂在苛刻条件下的长期稳定性测试中均表现出高反应稳定性。     

用双锥-内锥型水力旋流器提纯海洋天然气水合物浆体

针对水合物混合浆体中存在少量天然气的问题,设计了一种适合水合物混合浆体除气除砂的新型水力旋流器?双锥?内锥型水力旋流器,采用有限体积数值模拟方法研究了颗粒粒径、锥角组合、进口压力对固体颗粒和天然气分离效率的影响. 结果表明,固体颗粒粒径为50?90 ?m、天然气气泡直径为400?800 ?m、进口压力为4.3?7.3 MPa时分离效率最佳,最优的锥角组合为10o–5o.     

Microfluidic synthesis of elastomeric microparticles: A case study in catalysis of palladium‐mediated cross‐coupling

Palladium (Pd)‐loaded poly‐hydromethylsiloxane (PHMS) microparticles of tunable size and elasticity are prepared in a capillary‐based coaxial flow‐focusing microfluidic device constructed using off‐the‐shelf components. Simultaneous droplet formation and chemical cross‐linking processes are performed by tuning the dilution of the cross‐linking catalyst in the annular flow of the microreactor, resulting in PHMS microparticles synthesized in a single step. The size of the elastomeric microparticles can be tuned by adjusting the flow rate ratio of the polymer and cross‐linker mixture to water, while the elasticity can be tuned by the polymer to cross‐linker ratio as well as the flow rate ratio of the polymer mixture to cross‐linking catalyst mixture. Microparticle elasticity is characterized by the degree of solvent uptake. Application of the synthesized PHMS microparticles in organic synthesis is demonstrated by producing monodispersed Pd‐loaded microparticles and utilizing them as microreaction vessels for continuous Suzuki‐Miyaura cross‐coupling in a Pd‐loaded microparticle‐packed bed reactor. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3188–3197, 2018     

压载水旋流器结构因素对分离性能影响分析

随着全球贸易和船舶运输的发展,压载水对环境的影响越来越大。水力旋流分离设备是压载水净化的重要固液分离设备。本文使用计算流体力学,建立数学模型模拟压载水旋流分离过程,模型包括多相湍流雷诺应力模型RSM、处理气液界面的自由表面多相流动模型VOF、处理固体颗粒运动规律的离散相模型DPM。通过数值模拟计算柱段长度、底流口直径和溢流口直径这几个关键因素对旋流器内部流场和分离效率的影响,获得了各个因素对分离效率的影响规律：柱段长度变化对旋流器分离效率的影响不大;底流口直径对旋流器压力降的影响不明显,但对分流比的作用比较大;溢流管直径的增大有助于降低能耗和增大溢流口流量,但随着溢流管直径的增大,分级粒度变大。这些规律为高效旋流分离净化压载水奠定了基础。