Divided-wall distillation column design using molecular tracking

Divided-wall column (DWC) is an intensified separation process and so far developing a simple procedure for designing these units has been challenging. In this work, the concept of molecular tracking has been integrated with conventional methods to build a simple and easy-to-use methodology for designing DWCs for multicomponent separations. Application of the proposed approach is highlighted through several three- and four-component mixtures. The configuration obtained using molecular tracking gives a design with lower energy demands for the column reboiler, compared to other design methodology, which directly impacts the OPEX of the system.     

Ion-crosslinked carboxymethyl cellulose/polyaniline bio-conducting interpenetrated polymer network: preparation,characterization and application for an efficient removal of Cr(VI) from aqueous solution

A simple, cheap, and environmentally friendly bio-conducting interpenetrated polymer blend network was prepared and introduced as a highly efficient system with suitable physical and mechanical properties for industrial removal of toxic Cr(VI) ions from aqueous solution. Carboxymethyl cellulose/polyaniline (CMC/PANI) interpenetrated network (IPN) blend was prepared by simple simultaneous ion-cross-linking of CMC and PANI chains using Al³⁺ cations. The CMC/PANI bio-conducting nanocomposite was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy equipped with an "energy dispersive X-ray spectroscopy" (SEM–EDX) technique. The CMC/PANI blend, ion-cross-linked by Al³⁺ cations, showed good stability and high surface area, proper for the removal of toxic Cr(VI) ions of the aqueous solution. Batch removal experiments were accomplished and the impression of effective variables including solution pH, initial concentration of Cr(VI) ions, contact time, and adsorbent dosage were checked and optimized. The outcome of our findings revealed that the removal of Cr(VI) ions by CMC/PANI nanocomposite IPN strongly depends on solution pH. The removal information was matched with the Langmuir adsorption isotherm model and the utmost monolayer adsorption capacity at pH 2 was 136.98 mg/g at 25 °C. The pseudo-second-order kinetics were operated and the thermodynamic parameters suggested spontaneous and exothermic nature of the adsorption process. Consequences indicated that CMC/PANI nanocomposite IPN could be an affective eco/environmentally friendly adsorbent for the removal of Cr(VI) ions from aqueous solutions.

     

Molecular tracking: A concept for side-draw distillation column design

A simple approach is introduced to locate a side-draw tray for ternary and multi-component mixtures with middle boiling component(s) present in the system at trace levels. The concept is based on a probability function defined by the thermodynamic properties of the system. The advantage of this method over existing methods is the ability to quickly and efficiently provide a feasible configuration of the distillation unit without relying on rigorous optimization or trial and error approaches. Moreover, it provides an intuitive understanding of the movements of the middle boiling components in the column.     

Integrated design and control of reactive distillation processes using the driving force approach

Superior controllability of reactive distillation (RD) systems, designed at the maximum driving force (design-control solution) is demonstrated in this article. Binary or multielement single or double feed RD systems are considered. Reactive phase equilibrium data, needed for driving force analysis and design of the RD system, is generated through an in-house property prediction tool. Rigorous steady-state simulation is carried out in ASPEN plus in order to verify that the predefined design targets and dynamics are met. A multiobjective performance function is employed to evaluate the performance of the RD system in terms of energy consumption, sustainability metrics (total CO₂ footprint), and control performance. Controllability of the designed system is evaluated using indices like the relative gain array (RGA) and Niederlinski index (N_I ), to evaluate the degree of loop interaction, as well as through dynamic simulations using proportional-integral (PI) controllers and model predictive controllers (MPC). The design-control of the RD systems corresponding to other alternative designs that do not take advantage of the maximum driving force is also investigated. The analysis shows that the RD designs at the maximum driving force exhibit enhanced controllability and lower carbon footprint than the alternative RD designs.     

A novel decentralized method based on the system engineering concept for reliability‐security constraint unit commitment in restructured power environment

In the deregulated power environment, including Central operator (CO) and Micro Grids (MGs), different parts of the network are dedicated to the private sector, and each of them seeks to increase their profits independently. The CO and MGs should cooperate and collaborate in terms of operating, security and reliability in the whole power system. This article proposes a new method based on a System of System (SoS) concept for the secure and economic hourly generation scheduling to find optimal operational point. The main methodology includes three steps. In the first step, the power system is divided into several subsystems by using a spectral clustering partitioning technique to reduce converge time by decentralizes methods. And also load forecasting based on a Gaussian probability distribution function to avoid conventional calculation and considering uncertainty of the loads has been presented. To find a similar scenario, and reduction scenario with low probability, the probabilistic method has been addressed. The main contribution of this method is removing scenarios with low value of probabilities and scenarios which are similar to each other. In fact, the reduced set must include scenarios which are scattered appropriately in the uncertain space while holding high probabilities. In order to estimate the similarity (distance) between two scenarios the Kantorovich distance is implemented. In the second step, the hierarchical Bi‐level optimization approach is used to execute the decentralized decision making to solve the Security Constraints Unit Commitment (SCUC) problem between CO and MGs. Regarding all physical relations and shared data among CO and MGs, the SoS concept and Bi‐level optimization are presented to find the optimal operating point of autonomous systems. In the third step, a random number of generators will be select. Hence, the initial iteration number is set. In this step, sampling from state space to classifying reliability object achieved (The expected energy not supplied and loss of load probability are the reliability criterion). The presented method is evaluated using a 6‐bus, the RTS 24‐bus, 118‐bus, and 4672‐bus as an IEEE test systems. The suggested structure has been implemented by GAMS, and the results illustrate the usefulness of the presented methodology. To comparing proposed approach with the centralized method, the results illustrate improving total operational costs and security (in RTS‐24($603,209), 118 bus ($2 562 154) and 4672‐bus ($9 185 168)) in scenario 3 near to 9%, 10% and 8% respectively. Similarly, by comparison (in three test systems) with genetic algorithm these improvements are near to 23%, 22% and 13% respectively.     

Biohydrogen synthesis from catalytic steam gasification of furniture waste using nickel catalysts supported on modified CeO2

Present study evaluated the catalytic steam gasification of furniture waste to enhance the biohydrogen production. To do this, 10 wt% nickel loaded catalysts on the variety of supports (Al₂O₃, CeO₂, CeO₂-La₂O₃, and CeO₂–ZrO₂) were prepared by the novel solvent deficient method. The hydrogen selectivity (vol%) order of the catalysts was achieved as Ni/CeO₂–ZrO₂>Ni/CeO₂>Ni/Al₂O₃?Ni/CeO₂-La₂O₃. The best catalytic activity of Ni/CeO₂–ZrO₂ catalyst (~82 vol % H₂ at 800 °C) was ascribed to the smaller size of nickel crystals, finely dispersed Ni on the catalyst surface, and Ce_1-xZr_xO_2-δ solid solution. The role of Ce_1-xZr_xO_2-δ solid solution in Ni/CeO₂–ZrO₂ catalyst was observed as bi-functional; acceleration of water-gas-shift and oxidation of carbon reaction. The high resistance of Ni/CeO₂–ZrO₂ towards the coke formation showed its potential to establish a cost-effective commercial-scale biomass steam gasification process. This study is expected to provide a promising solution for the disposal of furniture wastes for production of clean energy (biohydrogen).     

Local RBF-DQ method for two-dimensional transient heat conduction problems

The meshless local radial basis function-based differential quadrature (RBF-DQ) method is applied on two-dimensional heat conduction for different irregular geometries. This method is the combination of differential quadrature approximation of derivatives and function approximation of radial basis function. Four different geometries with regular and irregular boundaries are considered, and numerical results are compared with those gained by finite element (FE) solution achieved by COMSOL commercial code. Outcomes prove that current technique is in very good agreement with FEM and this fact that RBF-DQ method is an accurate and flexible method in solution of heat conduction problems.     

Computational modeling and design of actively-cooled microvascular materials

The computational modeling and design of an actively-cooled microvascular fin specimen is presented. The design study is based on three objective functions: (i) minimizing the maximum temperature in the thermally loaded fin, (ii) optimizing the flow efficiency of the embedded microchannel, and (iii) minimizing the void volume fraction of the microvascular material. A recently introduced Interface-enriched Generalized Finite Element Method (IGFEM) is employed to evaluate the temperature field in a 2D model of the specimen, allowing for the accurate and efficient capturing of the gradient discontinuity along the fluid/solid interface without the need of meshes that conform to the geometry of the problem. Finding the optimal shape of the embedded microchannel is thus accomplished with a single non-conforming mesh for all configurations. Prior to the optimization study, the IGFEM solver is validated through comparison with infrared measurements of the thermal response of an epoxy fin with a sinusoidal microchannel.     

Natural convection heat transfer in a nanofluid filled semi-annulus enclosure

To investigate natural convection heat transfer in a semi-annulus enclosure filled with nanofluid, the Control Volume based Finite Element Method (CVFEM) is used. The fluid in the enclosure is Cu–water nanofluid. The inner and outer semi circular walls are maintained at constant temperatures while the two other walls are thermally insulated. The Navier Stokes equations in their vorticity-stream function form are used to simulate the flow pattern and isotherms. The numerical investigation is carried out for different governing parameters namely; the Rayleigh number, nanoparticle volume fraction and the angle of turn for the enclosure. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell–Garnetts (MG) and Brinkman models, respectively. The results reveal that there is an optimum angle of turn in which the average Nusselt number is maximum for each Rayleigh number. Moreover, the angle of turn has an important effect on the streamlines, isotherms and maximum or minimum values of local Nusselt number.