查看更多>>摘要：Accurate prediction of the concentration polarisation (CP) effect is very important in the design of an efficient membrane-based gas separation process. This study analyses the reliability of analytical film theory (FT) for evaluating the performance of gas separation membranes in terms of CP and flux. The analytical model is compared against a more rigorous numerical model developed by using Computational Fluid Dynamics (CFD) for various operating variables. The results show that the FT prediction is less accurate at high CP conditions when gas permeation through the membrane increases, due to higher permeance selectivity and pressure ratio. Hence, the results suggest that FT is not recommended for membranes with high permeance or high-pressure conditions. Given that the typical range of feed composition and temperature has little impact on fluid properties (i.e., gas diffusion coefficient, densities, and viscosities), the resulting CP does not vary much and hence both FT and CFD models predict a similar CP. The analysis also suggests that the FT model is more accurate in predicting CP in the region closer to the membrane entrance. Overall, the analytical film theory serves as a reliable approximation in membrane gas applications under low CP at high crossflow and low flux conditions.
查看更多>>摘要：Low-cost chicken waste fat, with a high content of palmitic acid (saturated fatty acid) and oleic acid (unsaturated fatty acid) was used for biolubricant production. The effects of different reaction parameters on the fat transesterification reaction using potassium hydroxide to form fatty acid methyl esters were investigated. In this study, the methyl esters from chicken waste fat were chemically modified to produce hydroxyl ethers (biolu-bricants) through epoxidation, followed by the ring-opening reaction of the epoxides with isoamyl alcohol in the molar ratio of 3:1 (alcohol:methyl esters) using the acid catalyst p-toluene sulfonic acid. The biolubricant obtained after the ring-opening of the methyl epoxides exhibited higher oxidative stability (OS) (18 h) than that of the biodiesel (3.85 h). The viscosity index of the biolubricant was found to be 295.32. The tribological performance of the biolubricant was enhanced by the addition of TiO2 (0.05% w/v). The biolubricant with 0.05% TiO2 led to a 25% reduction in friction coefficient and also enhanced the viscosity by 1.1-fold. Thus, TiO2 is suggested as a good antifriction property enhancer and viscosity modifier for the chicken waste lubricant. In summary, the chicken waste fat can be considered a feasible alternative to formulate biolubricants that match the physico-chemical and low-temperature properties of commercial hydraulic oils.
查看更多>>摘要：The effects of the interaction between the hydrodynamic and colloidal forces on the suspension and performance characteristics of a slurry photocatalytic reactor equipped with oscillatory membrane and lateral turbulence promoters are investigated. Aggregation of catalyst particles is influenced by the magnitude of colloidal forces between the particles in relation to the hydrodynamic stresses acting on the aggregate. The interaction of the axial oscillatory shear with the transverse motion of the turbulence promoters (TP) results in generation of vortices and eddies that extended further away from the membrane surface leading to reducing particle aggregation. For the range of oscillatory conditions investigated, the aggregate size remained in the viscous subrange and decreased with increasing the oscillation intensity where an almost three folds decrease in aggregate size was achieved at high oscillation intensities. This resulted in reducing particles settling and deposition on the membrane surface which increased the catalyst specific area and volume fraction in suspension and enhanced both membrane flux and reaction rates. Improvement of the latter is also achieved by the microscale eddies attenuation of the concentration boundary layer surrounding the catalyst particles which results in better mass transfer. Using methylene blue dye (MB) degradation with ZnO photocatalyst under UV illumination as a model photocatalytic reaction, the investigation showed that increasing the oscillation intensity resulted in higher membrane flux and reaction rates that asymptotically approached maximum corresponding to near maximum catalyst suspension. This was estimated based on the magnitude of the eddy forces in the suspension in relation to the sedimentation and permeate drag forces acting on the catalyst particles. Comparison between the results of the present investigation and data from the literature showed satisfactory agreement.
Michelle Mei Xue LumAbdul Rahman MohamedSin Yuan Lai
17页
查看更多>>摘要：Flue gas with high SO2 content presents a series of human health and environmental problems, which prompted Flue Gas Desulfurization (FGD) technologies widely utilised in industries. However, the conventional FGD using absorbents or adsorbents could generate secondary sulfur-containing pollutants. Thus, a regenerative FGD reaction system that eliminates secondary pollutants while recovering valuable S has been researched. Ba-based materials, viz. Ba(OH)2, BaCO3 and BaO as the precursors, are involved in a regenerative BaS/BaSO4 reaction system of this research. Current thermodynamic study via minimization of Gibbs free energy explored the feasibility of BaS production from these Ba-based materials and reviewed its potential in SO2 reduction to S. Formation of BaS from Ba-based materials was feasible but the yield depends strongly on the temperature and sulfidizing agent used. Compared to BaCO3-systems, Ba(OH)2- and BaO-systems showed better performance in BaS synthesis due to their high equilibrium conversion, even at temperatures < 773 K. Besides, H2S is a better sulfidizing agent for BaS synthesis due to higher BaS yield (maximum 99%). Synthesis routes of different Ba-systems were confirmed by their respective K_(eq) profiles. The feasibility of BaS catalyst in SO2 reduction to S was proven by the excellent SO2 reducing activity and high S yield (100%) at 273 - 1173 K with S8 and S2 as major products. BaS regeneration via H2 was also validated by high BaS yield (100%) at 473 - 1273 K.
查看更多>>摘要：Fouling in heat exchangers is unavoidable and causes performance degradation;; hence, occasional cleaning is essential. An effective cleaning strategy requires knowledge of foulants that can be obtained by laboratory tests. However, these are unaffordable for small and medium-scale industries. Model-based methods have been proposed for fou-lant characterization. However, they fail when exchangers are under temperature control and varying inlet conditions. This paper proposes a simple methodology to directly estimate foulants' characteristics using excess thermal and hydraulic loads. Specifically, it first uses changes in the pressure drop and mass flowrate vis-a-vis the exchanger's clean state to estimate foulant thickness. Subsequently, the estimated thickness is used along with temperature measurements to estimate the thermal conductivity. The methodology is demonstrated on a heat exchanger in two cases- with fouling only on tube side, and on both shell and tube sides. Our results show that the estimates have an error of less than 3% in all cases. A key advantage of the proposed methodology is that it can accommodate setpoint changes and disturbances that are common in industrial practise.
查看更多>>摘要：A low-cost microfiltration membrane was prepared by utilizing silicate cement and pore-forming material at room temperature. The effects of pore-forming material content (2-10%, wt.) on membrane properties such as morphology, porosity, flexural strength, pore size distribution, permeability, chemical stability and antifouling properties were investigated. The optimized silicate-based microfiltration membrane (SFM) with 6% of pore-forming material content has a porosity of 20.3%, an average pore diameter of 0.74 μm, a flexural strength of 13.2 MPa and a water permeability of 2.33 m~3·m~(-2)·h~(-1)·bar~(-1). The SFM had poor stability in the pH range of 1-3, while had good stability in the pH range of 5-10. The fouling mechanism was mainly the formation of cake layer according to the different plugging models through the SFM pollution test. The analysis of flux recovery ratio (FRR), total flux decline ratio (TFR), reversible flux decline ratio (RFR) and irreversible flux decline ratio (IFR) demonstrated that the SFM could be regenerated by cleaning with deionized water and 2 mg/L ozone solution. Compared with deionized water cleaning process, ozone solution cleaning could more effectively remove contaminants on the surface of SFM, and displayed favorable FRR of more than 90%. Finally, because of its promising properties and affordable cost, the developed membrane may be proposed as an alternative to conventional ceramic membranes for water purification.
查看更多>>摘要：In this research, separation of paraxylene from mixed-xylene using industrial Eluxyl adsorbent was investigated through batch and dynamic analysis methods at real operating conditions (9 bar and 175 °C). The Ba-faujasite exchanged commercial adsorbent (SPX-3000 fine) was characterized through the BET, XRD, FE-SEM, EDS, XRF, and TGA methods. The single and multicomponent equilibrium and single component kinetics of the adsorption of the mixed-xylene and para diethylbenzene as the desorbent in Eluxyl process were studied. It was found that the Langmuir and non-modified Langmuir (NML) models describe very well experimental data for single and multicomponent isotherms, respectively. Also, Pseudo-second-order kinetic model was selected to predict experimental results. Selective and non-selective volume of adsorbent were calculated to be 0.153 and 0.561, respectively through multicomponent breakthrough analysis. Selectivity factor of PX to MX, OX and EB were determined as 3.7, 3.96 and 3.3, respectively. Finally, a hierarchical method composed of the both batch and dynamic analysis were presented for the evaluation of the adsorbents for any other adsorptive separation.
查看更多>>摘要：Traditionally, chemical processes have been evaluated on the basis of economic criteria under the designated nominal conditions. However, sole dependence on such criterion does not always guarantee that a given process is operable in actual implementation if some uncertain parameters deviate from their assumed levels. Flexibility analysis has long been successfully adopted to quantify the ability of a process to maintain its feasibility within a range of uncertain parameter deviations. This paper presents the use of the dynamic flexibility index (FId) for improving the operational flexibility of process systems. In order to calculate FId efficiently, the computation strategy proposed by Ali et al. (2021) has been adopted. Specifically, by treating the manipulated variables as piecewise constant functions of time, the search procedure of the conventional vertex method can be enhanced based on the genetic algorithm. It has been shown in the case studies presented in this paper that the flexibility index can effectively guide process design to ensure op-erability in practical applications.
Osiris Martinez-SanchezFernando Israel Gomez-CastroNelly Ramirez-Corona
14页
查看更多>>摘要：Biodiesel can be obtained from a variety of oils and fats rich in triglycerides. Due to this variability, production processes must be flexible enough to handle different raw materials. This work reports the simulation-based design of a biodiesel production process able to obtain the biofuel from different raw materials. This approach avoids dependence on a single kind of raw material by developing a flexible process. The process is designed to ensure that the product accomplishes the international standard EN 14214 for any of the tested raw materials. A plantwide control structure is then developed to handle the potential variations in feed composition. The controllers' parameters are tuned, and the control scheme is tested to determine its capability to reach a new steady state in an acceptable period. According to the results, the steady state design allows producing biodiesel from three different raw materials in a single process by only adjusting the operational conditions, obtaining the lowest total annual cost when processing micro-algae oil. Moreover, the proposed control strategy allows rejecting the perturbations occurring when the change of raw material occurs, stabilizing after a maximum period of 8 h while maintaining a product still accomplishing the international standard EN 14214.
查看更多>>摘要：MoS2 quantum dots (MoS2 QDs) have recently attracted extremely high consideration owing to their exclusive qualities related to both sheet-like structures and QDs. Doping MoS2 QDs with other semiconductors, such as ZnO nanoparticles (ZnO NPs), has provided superior synergistic effects on their performances. Herein, we constructed mixed matrix loose nanofiltration polyethersulfone (PES) membranes decorated with MoS2 QDs, ZnO NPs, and MoS2 QDs@ ZnO NPs (MNQs) separately, prepared by phase inversion method, for a comprehensive study of filtration, antifouling, and photocatalytic properties. Among all the prepared membranes, the MNQ0.5 membrane provides enhanced properties such as high permeation (15.46 ± 0.75 L/m.2 h. bar which is 11 times greater than control PES), significant rejection performance against Rhodamine B (Rh. B) (>95 %), excellent photocatalytic activity (2.5 times greater than control PES), and outstanding anti-fouling features (FRR=93.14 %, reversible fouling ratios (Rr)= 39.17 %, irreversible fouling ratio (R_(ir)) = 6.85 %, and total fouling ratio (Rt)= 46.02 %). Besides, the best anti-fouling performance was obtained by the MNQ0.5 membrane in comparison to that of the bare PES one, confirmed via BSA protein permeance.
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