Sulfur compounds such as sulfur oxides (SOx) are generated and emitted from operations in the petroleum industry which have negative effects on the environment. This study gives a critical and detailed introduction to the control and treatment of sulfur co...

Control and treatment of sulfur compounds specially sulfur oxides (SOx) emissions from the petroleum industry: A review

In sandwich structures, lightweight cellular materials as the core hold the face sheets far away from the neutral axis to maximize the bending performance of the structure. Honeycomb materials as a major type of lightweight cellular materials have been widely applied in various fields, including aerospace, vehicle, marine, architecture and mechanical engineering, due to reliable mechanical properties and excellent designability. Using fiber-reinforced composites is an efficient method to develop ultralight honeycomb materials with superior mechanical behaviors. In recent years, fiber-reinforced composite honeycomb materials possessing lightweight and excellent mechanical performances have attracted noticeable attention to replacing traditional aluminum honeycombs and Nomex honeycombs. Compared to metal, polymer and Nomex paper, fiber-reinforced composites possess various merits, such as high specific stiffness and specific strength, excellent fatigue property, corrosion resistance and high-temperature resistance. Thus, the applications of fiber-reinforced honeycomb material for sandwich core have unlimited potential in hypersonic vehicles, long-range rockets, cargo vessels and protective systems. Although the fact that attention has been rapidly increasing, there is a lack of comprehensive reviews of new advances in the field of fiber-reinforced composite honeycomb materials. In this review, new advances reported by different scientists in the field of fiber-reinforced honeycomb materials have been reviewed and analyzed to provide an in-depth overview and knowledge for beginners in the field of ultra-lightweight and high-performance composite sandwich architectures. The challenges and prospects for the development of fiber-reinforced honeycomb materials have also been presented.

New advances in fiber-reinforced composite honeycomb materials

In this study, we propose a plasma-chemical hybrid NOx removal process using nonthermal plasma for the treatment of flue gases emitted from glass melting furnaces; the process is demonstrated through a laboratory-scale model experiment conducted using a semi-dry desulfurization apparatus. The performance of the system for simultaneous removal of SO2 and NOx is investigated. As a result, NO is effectively oxidized to NO2 by injecting ozone into the spray region and the removal efficiencies of 90% and 50% were obtained for NO and NOx, respectively. In addition, the SO2 removal efficiency of 84% was achieved.

Simultaneous Removal of NOx and SOx from Flue Gas of a Glass Melting Furnace using a Combined Ozone Injection and Semi-dry Chemical Process

Sideritis scardica and Sideritis syriaca are considered highly valuable plant materials and their total polyphenols (TP) and total flavonoids (TF) extracts can be employed in nutraceutics and cosmetics. A two-step process was proposed consisting in the ultrasound-assisted extraction (UAE) and concentration of the biologically active compounds via nanofiltration (NF). An extensive comparison between UAE and conventional high-temperature stirring was performed, taking into account the effect of process parameters such as solvent, temperature and ultrasonication. In terms of radical scavenging activity and time optimization, UAE was found more effective, providing – after only 1 h – extraction yields comparable to 20 h of the conventional thermo-mechanical method. The extract was then concentrated by nanofiltration in tangential mode at 20 bar using 300 and 500 Da cut-off Duramem membranes. Permeate and rejection flux was monitored during the filtration process. The lower molecular weight membrane showed higher permeability towards TP and TF and contributed to a more stable flux and lower fouling processes. To predict operational drawbacks, computational fluid dynamic simulations were performed to model the complex rotational flow occurring during membrane filtration.

Ultrasound-assisted extraction of biologically active compounds and their successive concentration by using membrane processes

Liquid Maldistribution in Random‐Packed Columns: Experimental Investigation of Influencing Factors

The liquid radial spreading coefficient of packings for absorption and rectification columns is necessary to determine the packing height which ensures uniform liquid distribution over the column cross section. The existing calculation methods can be used theoretically only when this coefficient is independent of the liquid superficial velocity, which is often not the case. A tracer method free from this limitation is developed and tested. The spreading coefficients for different sizes of modern, highly effective packings (Raschig Super-Ring, Ralu-Flow, and impulse metal tower packing) are determined. Practically, in the range of the experimental error, the spreading coefficients of these packings are independent of the liquid superficial velocity. For such packings the tracer method is expected to give the same results as the existing single jet method. Some differences between the results of these two methods are discussed and an explanation is proposed.

Determination of Liquid Radial Spreading Coefficients of Some Highly Effective Packings

Ceramic block packing of Honeycomb type for absorption processes and direct heat transfer

The present study aims at investigation of the liquid phase distribution in order to fill in the missing data on liquid spreading in industrial scale packing layer of metal Raschig Super-Ring (RSR) packings for development of a reliable prediction model. Our attempt to apply the well-proven dispersion model to RSR packings has faced difficulties connected with the packing open, web-like structure resulting in poor radial distribution properties and with the industrial scale of the packed column. An experimental set-up is designed so as to provide the necessary data for model parameters’ identification. Special attention is paid to the uniform liquid distributor, in order to ensure the validity of the model assumption of regular initial irrigation. The approach avoids the need of data from well-established wall flow, which can be measured at a very high (over 3 m in that scale) packing layer. Instead, it uses additional data from irrigation on the column wall, provided by a peripheral liquid distributor. The present work has obtained original data for the liquid distribution in RSR packings of different sizes addressing improvement and validation of a prediction model.

Experimental Investigation of Liquid Distribution in Open-structure Random Packings as a Basis for Model Refinement

The scientific interest in the efficiency of packed bed columns is a part of the world-wide pursuit of sustainability of the processes. The maldistribution of the phases in the apparatus reduces the efficiency and makes difficult the prediction of process performance and scaling up. The present work aims at modeling of liquid distribution in a packed column with high performance open-structure random packings - metal Raschig Super-Rings 0.7”, 1.5” and 3” and metal Pall rings 1”. Some new approaches for estimation and calculation of model parameters are proposed and tested, using own experimental data for Raschig Super-Rings and published data for Pall rings. A new procedure for identifying one of the model parameters, called by us “overlapping confidential intervals” solution, is developed and illustrated for Raschig Super-Ring packing in the case of partial radial insensitivity (“plateau”) of the residual variance between the model and experimental data. The obtained results show that using appropriate statistical methods of estimation, the dispersion model parameters can be successfully identified achieving a very good prediction of the experimental data. Several numerical examples and case studies are considered and discussed. For the case of Pall rings, the dispersion model predictions are in very good agreement with both published experimental data and predictions made by Computational Fluid Dynamics(CFD) modeling.

Modeling of Liquid Distribution in a Packed Column with Open-structure Random Packings

The aim of the present work is to study the transfer processes in a cross-flow filtration cell, in order to determine the conditions for stable and efficient operation of a side-stream filtration module, integrated with a bioreactor. The current interest in membrane integrated bioreactors is connected with the pursuit of energy and cost efficiency in a wide area of industrial applications, including wastewater treatment, food industry, pharmaceutical industry, and fuel production. A numerical CFD model is employed, based on previous experience with experimental concentration of antioxidants, such as polyphenols and flavonoids from extracts of natural products by nanofiltration. The geometry under investigation is a 3D model of the experimental flat-sheet cell with tangential orientation of the feed inlet. The swirling turbulent flow in the feed channel is favourable for reducing the concentration polarization layer on the membrane surface and preventing fouling. The main factors, affecting the filtration process, are the shear stress distribution and the concentration profiles in the vicinity of the membrane surface. The CFD models of mass transfer in cross-flow nanofiltration are scarce and there are none for the reference experimental filtration cell. The present CFD simulation reveals the concentration distribution in the feed channel. It complements previous data for the flow pattern with new knowledge on the mass transfer there, directed to understanding and control of the concentration polarization phenomenon. The numerical study uses the tools of ANSYS Fluent R13, based on the finite volume method for solving the Reynolds-Averaged Navier-Stokes (RANS) equations. The obtained results are analysed in rapport with available experimental data.

D. Dzhonova-Atanasova

Papers

Determination of Liquid Radial Spreading Coefficients of Some Highly Effective Packings

Ceramic block packing of Honeycomb type for absorption processes and direct heat transfer

Experimental Investigation of Liquid Distribution in Open-structure Random Packings as a Basis for Model Refinement

Modeling of Liquid Distribution in a Packed Column with Open-structure Random Packings

CFD Simulation of Cross-Flow Filtration