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• The multi-scale CFD model is developed for simulating slug flow crystallization. • The associated mathematical equations of the CFD model are explained. • An experimental study is conducted to validate the developed CFD model. • The CFD model predicts suspended flows among the gas–liquid-solid multiphase. • Effects of particulate flow pattern on crystallization are investigated. This article discusses the development of a new computational fluid dynamics (CFD) model, the MVP (MP-PIC coupled with VOF and PBE) method, which predicts the slug flow crystallization phenomenon. The model is capable of predicting the flow of gas–liquid-solid phases and the associated chemical and particle changes. The MVP model is validated through a comparison with an experimental study on LAM (L-asparagine monohydrate) crystallization, and the results demonstrate its ability to accurately predict the three-phase fluid flow with particle size variation. In particular, we have been able to predict the effect of slug length change on particle mixing and predict hydrodynamic factors such as the particle streamlines and the circulation number of the particle phase via case studies. Overall, the MVP model is expected to offer a new way to accurately predict slug flow crystallization and provide valuable information for the process intensification of crystallization. [ABSTRACT FROM AUTHOR]

Gas masks are critical for protection against chemical, biological, radiological, and nuclear materials. Efforts are underway to develop advanced cartridges for next-generation gas respirators in civil-military combined use to improve wearability and protection for users (firefighters, military personnel, and environmental and safety-related workers). Herein, the performance of three newly designed cartridges for a next-generation gas respirator was evaluated using flow analysis, along with adsorption characteristics. The adsorption kinetics of cyclohexane gas on ASC (a copper-silver-hexavalent chromium impregnated activated carbon in the study) was measured by breakthrough experiments in a packed bed, and the obtained parameters were used in the computational fluid dynamics (CFD) model for the designed plate-type cartridges. To apply the physical properties of the adsorbent to the CFD simulation, porous materials were expressed using the granular technique and packed bed technique. The CFD model was verified through a gas adsorption experiment using a prototype cartridge. The respiration resistance and breakthrough time for the filled-adsorbent efficiency and lifespan were compared among the three designed cartridges according to the gas inflow conditions. Additionally, virtual engineering was performed by grafting the CFD results to a virtual reality (VR) system with which 3-dimensional performance visuals of the cartridges could be observed. The developed VR system provides detailed information for cartridge design and optimization. Overall, the developed procedure of virtual engineering can be used to improve CFD simulation results. [Display omitted] • Advanced cartridges for a next-generation gas respirators were developed. • Adsorption and performance were evaluated using breakthrough and prototype tests. • Cartridge performance with filters and adsorbents was evaluated by CFD with UDFs. • Pressure drop, gas adsorption and flow, blind spots could be observed in cartridges. • Virtual engineering for 3D observation was achieved by grafting a VR system to CFD. [ABSTRACT FROM AUTHOR]

Demilitarization of waste explosives on a commercial scale has become an important issue in many countries, and this has created a need for research in this area. TNT, RDX and Composition B have been used as military explosives, and they are very sensitive to thermal shock. For the safe waste treatment of these high-energy and highly sensitive explosives, the most plausible candidate suggested has been thermal decomposition in a rotary kiln. This research examines the safe treatment of waste TNT, RDX and Composition B in a rotary kiln type incinerator with regard to suitable operating conditions. Thermal decomposition in this study includes melting, 3 condensed phase reactions in the liquid phase and 263 gas phase reactions. Rigorous mathematical modeling and dynamic simulation for thermal decomposition were carried out for analysis of dynamic behavior in the reactor. The results showed time transient changes of the temperature, components and mass of the explosives and comparisons were made for the 3 explosives. It was concluded that waste explosives subject to heat supplied by hot air at 523.15 K were incinerated safely without any thermal detonation. [ABSTRACT FROM AUTHOR]

• 4-tube catalytic membrane reactor (CMR) and baffled membrane reactor (BMR) are compared with CFD simulations. • The baffles enhance the performance of the CMR measured in terms of CH 4 conversion and permeate H 2 yield. • Performance of the BMR is less sensitive to an increase in the gas hourly space velocity than the CMR. • The BMR with a varying number of tubes is analyzed through concentration and temperature distribution. [Display omitted] Catalytic membrane reactor (CMR) represents an intensified process that combines the reaction and separation steps. For a high level of productivity, multiple membrane tubes are placed in a CMR, which can lead to the problem of concentration and temperature gradients. This study explores the idea of placing baffles inside the CMR, which is called baffled membrane reactor (BMR). Representative CMR and BMR are compared using computational fluid dynamics (CFD) simulations. First, the CFD model of a single-tube CMR is validated with the published experimental data. The results for a 4-tube CMR and BMR (with 14-baffles) reveal that the baffles lead to complex flow patterns, regions with elevated pressure, reduced concentration gradients and reduced temperature drops. The BMR's performance is less sensitive to an increase in gas hourly space velocity than that of the CMR. Simulations of a larger-scale BMR shows that the performance improvement over the CMR is retained. [ABSTRACT FROM AUTHOR]

Purpose: Epidemiological studies have shown that obesity is associated with an increased risk of thyroid cancer. However, the exact nature of the relationship, especially with respect to the behavior of the cancer, remains uncertain. The objective of this study was to evaluate the correlation between the body mass index (BMI) and clinicopathological features of thyroid cancer patients. Methods: From January 2009 to April 2010, 716 consecutive patients (602 females and 114 males; mean age 47.02 ± 11.73 years) with papillary thyroid cancer (PTC) were analyzed retrospectively. Patients were divided into two subgroups according to age (<45 years, ≥45 years). The BMI groupings were based on standardized categories set by the World Health Organization. The relationships between the BMI and these parameters were assessed. Results: A non-overweight BMI was associated with a younger age and female gender. Tumor multiplicity was related to a higher BMI. In an age-related subgroup analysis, a higher BMI was correlated with more lymph node involvement ( p = 0.004), lymphatic invasion ( p = 0.003) and tumor multiplicity ( p = 0.008) in patients ≥45 years of age. The absence of an association between the BMI and T stage, nodal status, vascular invasion, lymphatic invasion, and extrathyroidal extension was noted in a statistical analysis. In the subgroup of patients <45 years of age, no positive associations were observed between the BMI and any parameters other than age and sex. Conclusions: In PTC patients ≥45 years of age, a higher BMI was associated with more aggressive tumor features, such as lymph node metastasis, lymphatic invasion, and tumor multiplicity. [ABSTRACT FROM AUTHOR]

• The multi-scale CFD model is developed for simulating MMA suspension polymerization in a CSTR. • The associated mathematical equations of the CFD model are explained. • The CFD model clearly shows suspended flow patterns between particles and solvent • Effects of blade angles of impeller on particle size distribution and particle mixing are investigated. This research presents an advanced multi-scale computational fluid dynamics (CFD) model based on the 'multi-phase particle-in-cell coupled with the population balance equation (MP-PIC-PBE)' method to predict the stationary continuous stirred tank reactor for methyl methacrylate suspension polymerization. The developed CFD model can realistically simulate the flow patterns of the free-flowing particles and the continuous carrier phase based on the Euler-Lagrangian frame and can track the change in particle size based on PBE. In particular, the model can predict the polymer properties by free-radical polymerization in a parcel through the method of moment equations. To validate the suggested CFD model, the simulation results are compared with the reported experimental data in the literature. Various case-studies are then conducted to investigate the effect of different blade angles (pitched blade angles of 30˚, 45˚, and 60˚) of the impeller on the mixing, the particle size change, particulate flow pattern, and polymer properties. The simulation results demonstrate the phenomena that the low-density particles rise in the larger density solvent by buoyancy and that the higher the blade angle, the smaller the resulting particles due to a higher rate of breakage. It is also found that the particulate flow is well mixed with a 45˚ blade angle. [ABSTRACT FROM AUTHOR]

• The MP-PIC-PBE method is proposed for simulating multi-scale particulate flows coupled with particle formation and growth. • The associated mathematical equations and numerical solution methods are explained. • The proposed method is shown to be more efficient than the existing particulate CFD methods. • The proposed method generates more information on particles than the existing particulate CFD methods. The 'multiphase particle-in-cell coupled with population balance equation' (MP-PIC-PBE) method is introduced for simulating multi-scale multiphase particulate flows. This method couples the meso‑scale fluid dynamics simulated by the MP-PIC method with the simulation of the micro-scale particle size distribution. The homogeneous population balance equation is calculated for each discrete particle tracked in a Lagrangian frame, after the MP-PIC numerical procedure is followed at each time instance. This approach allows the particulate phase to accommodate the particulate stresses using spatial gradients and allows the Lagrangian description to predict particle properties by the PBE. For the antisolvent crystallization of Lovastatin in a biradial mixer, the proposed method is compared to an existing method that simulates the spatiotemporal evolution of the particle distribution by combining a multi-environment probability density function with the spatially varying PBE. The MP-PIC-PBE method has lower computational cost and provides more detailed information, such as particle age and location. [ABSTRACT FROM AUTHOR]

Spinning Cone Column (SCC) is considered as an alternative to the existing stripping equipment in a residual monomer removal process. Rotation-induced dynamics of the fluid are key to the process's enhanced efficiency, but the complex features of the SCC make its operation and design challenging. In this study, fluid dynamics inside a lab-scale SCC are investigated from a new angle. Full three-dimensional CFD transient simulations are conducted under various operation and design conditions. In particular, an Eulerian-Lagrangian approach is implemented to describe the motions of the liquid droplets as well as of the liquid film. Based on the results from the CFD simulations, key phenomena for the enhanced performance in monomer removal by the SCC are discussed. The study is intended to provide fundamental understandings of the flow patterns inside SCC, which can be translated into valuable insights for stable operation and scale-up. [ABSTRACT FROM AUTHOR]

Understanding separation behavior in an adsorption bed is crucial for well-designed adsorption processes. Since adsorption phenomena depend on temperature, thermal parameters, such as the internal heat transfer ( h i ), isosteric heat of adsorption (Q st ) and axial thermal conductivity of the bed (K w ), can affect the adsorption dynamics and performance of the bed. In this study, the effects of these thermal parameters on the adsorption dynamics and breakthrough curves were analyzed with the experimental results using integrated gasification combined cycle gas from the carbon capture process (IGCC gas; H 2 :CO:N 2 :CO 2 :Ar = 88:3:6:2:1 mol%) as a purification gas and blast furnace gas (BFG; H 2 :CO:N 2 :CO 2 = 20:0.1:44.5:35.4 mol%) as a bulk separation gas. The results were then compared with the isothermal and adiabatic results. Considering the variation of the internal heat transfer coefficient and isosteric heat of adsorption along with the propagation of gas in the bed, the temperature profiles inside the bed could be predicted better than in the case using constant values. The axial thermal conductivity of the bed significantly affected the temperature profiles as the temperature excursion was sharp. In the prediction of breakthrough curves, these variable thermal parameters could be replaced by suitable constant values estimated from experimental and theoretical approaches when well-fitted isotherm parameters were applied considering the partial pressure of each component in the feed. [ABSTRACT FROM AUTHOR]

Integrated gasification combined cycle (IGCC) plants that are also capable of CO 2 capture have received significant attention as the next generation of coal-based power plants for the co-production of H 2 and electrical power. Accordingly, for a cost-effective and environmentally friendly poly-generation IGCC process, efficient techniques need to be developed to recover H 2 from the syngas of an IGCC plant with carbon capture. In this study, an eight-layered bed pressure swing adsorption (PSA) process using activated carbon and zeolite simultaneously was developed to produce high purity H 2 from the H 2 -rich syngas of an IGCC plant. As a first step, the separation performance was compared between four-and eight-layered bed PSA processes. The eight-layered bed PSA process led to higher recovery of H 2 at the condition of a similar H 2 purity owing to a greater number of pressure equalization steps in the operational step configuration. It is noteworthy that the productivity could be greatly improved as the purge gas was replaced from the product gas to residual gas in a bed. When the adsorption bed was purged by using the residual gas after the first pressure equalization step, recovery improved by about 3 ∼ 6 % at the condition of 99.99+ mol% H 2 purity in comparison with the product-purge PSA configuration. On the other hand, the highest H 2 recovery that could be obtained for the requirement of 99.99 mol% H 2 purity, was ∼ 89.7 % from the eight-layered bed H 2 PSA process when the purge gas was provided from the residual gas of the adsorption bed after the last depressurization pressure equalization step. However, as the concentration of CO in the desired H 2 product was higher in the PSA configuration when using residual gas compared to the product gas, the operational configuration of PSA needed to be decided by the desired H 2 purity and impurity constraints for application. Furthermore, the tail gas from the PSA contained 45–66 mol% of H 2 and CO, depending on the applied PSA configurations, and could be used to drive a gas turbine without any loss of the syngas, even though the recompression energy loss required evaluation. [ABSTRACT FROM AUTHOR]