A Diffusion Model for a Drum Dryer Subjected to Conduction, Convection, and Radiant Heat Input

Drum dryers are commonly used for production of a flaky dry powder from thick suspensions. This article presents results of a simple diffusion-based model to predict the drying performance of a pilot-scale twin-drum dryer. Numerical results are compared with experimental data obtained for a biological sludge whose initial moisture content varied from 1.0 to 2.3 kg/kg db. The agreement of model predictions with the pilot-scale experimental data is favorable. Effects of film thickness, drum rotational speed, external air flow velocity, and its humidity are examined parametrically. Sludge film thickness is identified as the most critical operating parameter to control the final moisture content and productivity of the dryer. The validated model is used to predict performance of a drum dryer subjected to heat input by convection and radiation along with conduction through the drum wall. It is shown that dryer output can be enhanced significantly by increasing the film thickness and applying radiant heating in the initial period of drying. A simple mathematical model of this type can be used for the purpose of design and analysis as well as scale-up of industrial drum dryers based on simple laboratory-scale experiments.     

Transient Coupled Radiation and Conduction Heat Transfer in a Scattering Layer of ARLEN

ARLEN is a heat-resistant, modified polyamide with a high melting point and a rigidity level comparable to super engineering plastics. It possesses strong dimensional stability and is widely used in engineering and high-temperature applications. At elevated temperatures, radiative transfer becomes important, and transient temperature responses, including radiation, can be significantly different from those by conduction alone. This work considers transient radiative and conductive heat transfer in a plane, absorbing, emitting and isotropically scattering layer of ARLEN. The solution includes the radiative two-flux equation, which is coupled with the transient energy equation, and both equations are solved simultaneously. The two-flux method is used as a simplification for obtaining the radiative heat source term in the energy equation. The external boundaries of the layer are exposed to a radiative environment and can be convectively heated or cooled.     

Modeling Intermittent Drying of Wood under Rapidly Varying Temperature and Humidity Conditions with the Lumped Reaction Engineering Approach (L-REA)

For improving product quality and minimizing energy consumption during drying, intermittent drying is often recommended. The mathematical models that are used to describe intermittent drying are usually transport phenomena based, complex models. In this study, the lumped reaction engineering approach (L-REA) is implemented to model wood drying under rapid periodically changed drying air temperature and humidity with high number of cycles of intermittency. The equilibrium activation energy (ΔE _v,b ), an important parameter for REA approach, is evaluated according to the corresponding drying air temperature and humidity in each drying section. The results of modeling suggest the L-REA works well with the experimental data. The simplicity of the L-REA is obvious and is hoped to be used in an industrial setting more readily. The L-REA can be used for sustainable processing in industries to assist in energy audit and management.     

Fluid Dynamics of Vibrofluidized Beds during the Transient Period of Water Evaporation and Drying of Solutions

The influence of vibration number Γ, amplitude A, and frequency of vibration f on the fluid dynamic behavior of a vibrofluidized bed operating with inert particles in the transient period of water evaporation and drying of different solutions was evaluated. The solutions investigated were sewage sludge, skimmed milk, and calcium carbonate of three different solids contents. The impact of feed rate and vibration parameters on the dynamic behavior of variables such as pressure drop and inlet air velocity was determined. Based on the results it was verified that the operation at A = 0.015 m improved the bed dynamics and the gas‐particle contact in the wetted beds. As different dynamic behaviors may be obtained under the same Γ value, the values of A or f must be informed together with Γ for a complete characterization of vibration effects.     

Transient solutions of potential steps at the rotating disc electrode with steady state initial concentration profiles for one electron transfer reactions

In this paper the transient solution of a potential step at a rotating disc electrode (RDE) for irreversible and quasireversible one electron transfer reactions is derived by Nernst diffusion layer approximation and separation of variables. This is then compared to finite element simulation results. For the initial conditions steady state concentrations are chosen, such that with this theory it is possible to fit and simulate quasi steady-state linear sweep RDE measurements or other quasi steady-state sequences of potential steps.It was found that it is possible to derive accurate closed form solutions for the initial parts of the transient response. However, the Nernst diffusion layer approximation leads to inaccuracies in the intermediate times with relative errors of up to 10%.By fitting the initial transient to the closed form solution it is possible to extract steady state background currents. Additionally, we use the potential step theory to derive an expression for kinetically controlled transition times and show that these can exceed the mass transport controlled transition time.     

Lumped heat and mass transfer coefficient for simulation of a pressure swing adsorption process

The practical implications of replacing various individual transport resistances such as gas-solid mass and heat transfer, and gas phase axial dispersions of mass and heat in a numerical model of a pressure swing adsorption (PSA) process by a single, empirical, lumped, effective mass transport coefficient were evaluated. A non-isothermal, adiabatic, four-step Skarstrom-like PSA process for production of pure helium from a binary helium-nitrogen mixture using 5A zeolite adsorbent was considered. It was found that the above-described model simplification was adequate to describe key process performances such as the bed size factor and the product recovery vis-a-vis a detailed model where the effects of all individual resistances were explicitly included.     

大体积混凝土基础裂缝分析及温控监测措施

随着社会的不断发展,大体积混凝土基础随处可见,如高层楼房基础、大型设备基础等。大体积混凝土基础裂缝的产生会严重影响上部结构的施工质量,以及整个建筑物或设备的使用寿命,因此分析大体积混凝土基础裂缝产生的原因,采取有效的温控监测措施,意义重大。文章对大型储罐混凝土基础的裂缝进行分析及采取有效的温控监测措施。     

Coupled Enzymatic Treatment and Mass Spectrometric Analysis for Identification of Glucuronidated Metabolites in Human Samples

Glucuronidation is the most common phase II modification and plays an important role in human clearance metabolism. Glucuronidated metabolites have also been linked to disease development and microbiota–host co-metabolism. Although many of these compounds have been identified, the total number of unknown glucuronides and their impact on the human host's physiology can only be estimated. Herein, we describe the combination of an untargeted metabolomics analysis and enzymatic metabolic conversion for the selective detection of glucuronide conjugates by using UPLC-MS/MS in human urine samples. Our study demonstrates that this powerful strategy can be used for the selective identification of glucuronidated molecules and to discover unknown natural metabolites. In total, we identified 191 metabolites in a single sample including microbiota-derived compounds as well as previously unidentified molecules.     

On the Effect of Surfactant on Mass Transfer to Water–Glycerol Solutions in a Pulsed Baffled Reactor

This paper describes the effect of surfactant (0·025%w/w octanol) on mass transfer of oxygen into water–glycerol solutions of viscosity up to 21 mPa s in a pulsed baffled reactor. We also report the effect of air entrainment on the volumetric mass transfer coefficient in the open reactor system. The results show that the presence of octanol in solutions increases the mass transfer rate for all the experimental conditions tested, in particular, a higher percentage increase in k_La was obtained for more viscous solutions. This behaviour can be attributed to the non-coalescing characteristics of the octanol that is added to the water–glycerol solutions. The results of air entrainment on k_La suggest that the effect of the surface air entrained into the system on k_La measurement is insignificant. © 1997 SCI.     

The Effect of Bed Temperature on Mass Transfer between the Bubble and Emulsion Phases in a Fluidized Bed

The rate of interphase mass transfer between the bubble and emulsion phases of a bubbling fluidized bed is of primary importance in all models for fluidized bed reactors. Many experimental studies have been reported, however, all these investigations have been carried out in fluidized beds operated at room temperature. In this work, the effect of the bed temperature on the interphase mass transfer is reported. Single bubbles containing argon – used as a tracer – were injected into an incipiently fluidized bed maintained at the required temperature. The change in argon concentration in the bubble was measured using a suction probe connected to a mass spectrometer. The effects of bed particle type and size, bubble size, and bed temperature on the mass transfer coefficient were examined experimentally. The interphase mass transfer coefficient was found to decrease with the increase in bed temperature and bubble size, and increase slightly with increase in particle size. Experimental data obtained in this study were compared with some frequently used correlations for estimation of the mass transfer coefficient.     

Developing an Application Analytical Solution of Adiabatic Heat and Mass Transfer Processes in a Liquid Desiccant Dehumidifier/Regenerator

An analytical solution of simultaneous heat and mass transfer processes in a packed bed liquid desiccant dehumidifier/regenerator is developed. Various dimensionless parameters and reliable assumptions are used in order to develop this solution. The outlet parameters predicted with the analytical solution show very good agreement with the experimental data available in the literature. The results show that using a Lewis number value of Le = 1.1 instead of Le = 1 gives a better prediction of the performance of the dehumidifier. In addition, the use of Le = 0.9 instead of Le = 1 can give a better prediction of the outlet parameters of the regenerator. The benefits of the present solution are its simplicity and easy application for the simulation of air dehumidification and liquid desiccant regeneration processes.     

Evaluation of the Calmodulin‐SOX9 Interaction by “Magnetic Fishing” Coupled to Mass Spectrometry

Disruption of calmodulin (CaM)‐based protein interactions has been touted as a potential means for modulating several disease pathways. Among these is SOX9, which is a DNA binding protein that is involved in chrondrocyte differentiation and regulation of the hormones that control sexual development. In this work, we employed a “magnetic fishing”/mass spectrometry assay in conjunction with intrinsic fluorescence to examine the interaction of CaM with the CaM‐binding domain of SOX9 (SOX‐CAL), and to assess the modulation of this interaction by known anti‐CaM compounds. Our data show that there is a high affinity interaction between CaM and SOX‐CAL (27±9 nM ), and that SOX‐CAL bound to the same location as the well‐known CaM antagonist melittin; unexpectedly, we also found that addition of CaM‐binding small molecules initially produced increased SOX‐CAL binding, indicative of binding to both the well‐known high‐affinity CaM binding site and a second, lower‐affinity binding site.     

用于制备本体ABS树脂的引发剂—评价与应用

采用三釜连续聚合装置,开展连续本体ABS树脂研究。根据产品动力学参数,选定了3种过氧化物类引发剂,分析了产品在反应釜内的半衰期、分解曲线、残留物含量以及对本体ABS树脂性能的影响规律。从反应平稳控制、SAN的接枝效率、引发剂对基体树脂的强度、ABS冲击强度、耐热性的影响等方面对不同引发剂作出评价筛选。     

影响催化裂化装置长周期运行的因素及解决方案

总结了影响催化装置长周期运行的部分关键因素,从工艺和设备管理2个方面,提出了一些具体解决措施和办法。     

聚丙烯粉料的分子质量及其分布测定方法

采用凝胶渗透色谱(GPC)测定聚丙烯粉料加入不同类型、不同浓度抗氧剂后相对分子质量及其分布,结果表明,未加入抗氧剂的聚丙烯粉料相对分子质量随着时间的增加不断降低,而加入抗氧剂的聚丙烯粉料能保持稳定,浓度为50mg/Kg的抗氧剂1010可以达到很好的防降解效果。建立GPC测定聚丙烯粉料的分子质量及其分布的方法,该方法适用于生产过程中的中控检测。     

提高材料学科大学生工程素质的必要性和措施

高层次工程技术人才是现代化企业发展的关键因素之一,是国家走新型工业化道路、建设创新型国家战略目标的重要支撑。文章论述了提高材料学科大学生工程素质的必要性,提出利用学科实验平台为支撑的校内工程创新实验室、校企联合研究平台来提高材料本科生的工程素质。     

Microporous hollow fibres for carbon dioxide absorption: Mass transfer model fitting and the supplying of carbon dioxide to microalgal cultures

A method of supplying CO₂ to photosynthetic algal cultures was developed based on mass transfer measurements of CO₂ through microporous hydrophobic hollow fibres for various gas and liquid flow rates. A mathematical model was derived to describe the mass transfer. The designed hollow fibre module led to overall mass transfer coefficient values ranging from 1·26 × 10⁻³ to 2·64 × 10⁻³ cm s⁻¹. Higher efficiencies of the CO₂ transmission were obtained at high liquid flow rates and low gas flow rates. The use of microporous hydrophobic hollow fibres enabled an enhancement of the carbon dioxide transfer per area of membrane surface by a factor of 10, in comparison to operation with silicone tubing. The hollow fibre module was operated in an external bypass to a 1 dm³ microalgae culture vessel. In this system the algal growth pattern was similar to that obtained with a control culture where CO₂ was bubbled. However, the dissolved oxygen concentration was always lower in the vessel in which CO₂ was supplied by the module. © 1998 SCI.     

Access of Hydrogen-Radicals to the Peptide-Backbone as a Measure for Estimating the Flexibility of Proteins Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

A factor for estimating the flexibility of proteins is described that uses a cleavage method of “in-source decay (ISD)” coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). The MALDI-ISD spectra of bovine serum albumin (BSA), myoglobin and thioredoxin show discontinuous intense ion peaks originating from one-side preferential cleavage at the N-Cα bond of Xxx-Asp, Xxx-Asn, Xxx-Cys and Gly-Xxx residues. Consistent with these observations, Asp, Asn and Gly residues are also identified by other flexibility measures such as B-factor, turn preference, protection and fluorescence decay factors, while Asp, Asn, Cys and Gly residues are identified by turn preference factor based on X-ray crystallography. The results suggest that protein molecules embedded in/on MALDI matrix crystals partly maintain α-helix and that the reason some of the residues are more susceptible to ISD (Asp, Asn, Cys and Gly) and others less so (Ile and Val) is because of accessibility of the peptide backbone to hydrogen-radicals from matrix molecules. The hydrogen-radical accessibility in MALDI-ISD could therefore be adopted as a factor for measuring protein flexibility.     

Revision of the Cyclisation Mechanism for the Diterpene Spiroviolene and Investigations of Its Mass Spectrometric Fragmentation

The diterpene spiroviolene, its diterpene synthase from Streptomyces violens and the experimentally determined terpene cyclisation mechanism were reported in 2017. Recently, the structure of spiroviolene was revised based on a total synthesis, with consequences for the cyclisation mechanism. Herein, a reinvestigation of the terpene cyclisation to spiroviolene and the mass spectrometric fragmentation mechanism investigated by ¹³C-labelling experiments are presented.