Control and dynamic analysis of a packed distillation column based on modeling approaches

In this work, dynamic analysis and control of a packed distillation column have been utilized theoretically and experimentally. In theoretical studies, two types of mathematical models stagewise (Frank model) and partial differential approaches (back-mixing model), were used. Packed distillation uses 1400 mm packing height, and packing type is rashing ring with 20-15 mm diameter. The reboiler was made from a 13 L glass container. Reflux ratio was adjusted by an on-line computer. The system temperature was measured with six thermocouples. For control studies, the reflux ratio and the reboiler heat dutywere chosen as manipulated variables. Perturbation in feed composition was utilized as the disturbance. Decoupling multivariable dynamic matrix control (DDMC) and Nondecoupling multivariable dynamic matrix control (NDMC) of overhead and bottom compositions were applied for control studies. Performance of the control system was tested by using an integral absolute error (IAE) criterion and it was also compared with decoupling multivariable PID control (DPID) and Nondecoupling multivariable PID control (NDPID).     

Determination of the Optimum NiS Fire Assay Parameters for Pt,Pd, and Rh in Automotive Exhaust Catalytic Converters

This work investigates the performance of the nickel sulfide fire assay (NiS-FA) for the pyrometallurgical analysis of platinum group elements (PGEs) from mixtures of automotive exhaust catalytic converters (e.g., gasoline, diesel, and diesel particular filter) by assessing the effects of various flux materials and reaction parameters on platinum, palladium, and rhodium recovery. Inductively coupled plasma mass spectrometry and atomic absorption spectroscopy (AAS) are used for the analysis of the NiS-FA beads. We found that the optimum recovery (at least 99.0%) was achieved with reaction of 11.5 g of flux (0.53 w/w ratio, sodium tetraborate:sodium carbonate), 1 g nickel, and 0.84 g sulfur (1.2 w/w ratio, Ni:S) per gram of sample for 90 min at 975°C. Reference standards (NIST SRM 2557) were used to compare efficiencies and identify the optimum conditions. The results are consistent with certified values and PGEs could be recovered within the 95% confidence level. The precision (<4.0% RSD) of all measurements, expressed as percentage relative standard deviation (SD), ranged up to 3.0%.     

Thermodynamic analysis of an existing coal-fired power plant for district heating/cooling application

In a conventional coal-fired power plant, which is only designed for electricity generation, 2/3 of fuel energy is wasted through stack gases and cooling water of condensers. This waste energy could be recovered by trigeneration; modifying the plants in order to meet district heating/cooling demand of their locations. In this paper, thermodynamical analysis of trigeneration conversion of a public coal-fired power plant, which is designed only for electricity generation, has been carried out. Waste heat potentials and other heat extraction capabilities have been evaluated. Best effective steam extraction point for district heating/cooling system; have been identified by conducting energetic and exergetic performance analyses. Analyses results revealed that the low-pressure turbine inlet stage is the most convenient point for steam extraction for the plant analyzed.     

Numerical Determination of Thermal-Diffusivity Coefficients of Some Nematic Liquid Crystals <Emphasis Type="Italic">in Situ</Emphasis>

In this study, a new experimental study has been implemented to determine the thermal-diffusivity parameters of industrial nematic liquid crystals, 4-pentyl-4′-cyanobiphenyl (5CB) and 4′-octyl-4-cyanobiphenyl (8CB), both numerically by using the finite difference method (FDM) for forward solutions and experimentally by measuring the temperature variation with time and position. The most important parts of this experimental study are the heating system and the liquid crystal cell, which were constructed in-house to determine the temperatures of the materials in situ. Four different positions for local measurements have been studied, and the optimum graph of this variation has been determined. The experimental and theoretical results of this study are consistent with previous measurements performed by means of a conventional thermal technique.     

Highly efficient nonlinear regression for big data with lexicographical splitting

This paper considers the problem of online piecewise linear regression for big data applications. We introduce an algorithm, which sequentially achieves the performance of the best piecewise linear (affine) model with optimal partition of the space of the regressor vectors in an individual sequence manner. To this end, our algorithm constructs a class of \(2^D\) sequential piecewise linear models over a set of partitions of the regressor space and efficiently combines them in the mixture-of-experts setting. We show that the algorithm is highly efficient with computational complexity of only \(O(mD^2)\), where m is the dimension of the regressor vectors. This efficient computational complexity is achieved by efficiently representing all of the \(2^D\) models using a “lexicographical splitting graph.” We analyze the performance of our algorithm without any statistical assumptions, i.e., our results are guaranteed to hold. Furthermore, we demonstrate the effectiveness of our algorithm over the well-known data sets in the machine learning literature with computational complexity fraction of the state of the art.     

Morphology,order, light transmittance,and water vapor permeability of aluminum‐coated polypropylene zeolite composite films

In this study, the polypropylene–zeolite composite films having 2–6 wt % natural zeolite were coated with a thin film of aluminum (Al) by magnetron sputtering, and the contribution of the Al coating on film properties was investigated. The samples were characterized by EDX, X‐ray diffraction, SEM, AFM, UV–visible spectroscopy, and water vapor permeation analyses. The surface of the films coated with a smooth Al film having 98–131 nm thickness. EDX revealed that Al percentage on the surface appeared to be as 8–10 wt % indicating contribution of polymer surface under Al film to analysis. XRD analysis showed that the grain size of Al at the surface was 22–29 nm. The surface roughness increased after Al‐coating process. The transmission of coated films was very low for both UV and visible regions of the light spectrum. Permeation analysis indicated that water vapor permeation was lower for Al‐coated material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effects of Ni-addition on the crystal structure,thermal properties and morphology of Mg-based hydroxyapatites synthesized by a wet chemical method

Four Mg-based hydroxyapatites (HAps) doped with Ni at various amounts of 0, 0.6, 1.2 and 1.8?at% were prepared at the temperature of 870?°C by a wet chemical synthesis. The crystallite size, lattice parameters and crystallinity percent dramatically decreased with adding of Ni. The amount of HAp phase for all the Ni-containing samples is smaller than that of the Ni-free MgHAp. Furthermore, the lattice strain, stress and anisotropic energy density values were affected by the amount of Ni. The differential thermal analysis (DTA) measurements taken in the temperature range from 25 to 1000?°C showed that all the samples are thermally stable. No significant change in the morphology was observed. It was observed that the gradual introduction of Ni caused the Ca-deficiency.     

Comparative energetic and exergetic performance analyses for coal-fired thermal power plants in Turkey

The purpose of this study is to analyze comparatively the performance of nine thermal power plants under control governmental bodies in Turkey, from energetic and exergetic viewpoint. The considered power plants are mostly conventional reheat steam power plant fed by low quality coal. Firstly, thermodynamic models of the plants are developed based on first and second law of thermodynamics. Secondly, some energetic simulation results of the developed models are compared with the design values of the power plants in order to demonstrate the reliability. Thirdly, design point performance analyses based on energetic and exergetic performance criteria such as thermal efficiency, exergy efficiency, exergy loss, exergetic performance coefficient are performed for all considered plants in order to make comprehensive evaluations. Finally, by means of these analyses, the main sources of thermodynamic inefficiencies as well as reasonable comparison of each plant to others are identified and discussed. As a result, the outcomes of this study can provide a basis used for plant performance improvement for the considered coal-fired thermal power plants.     

Visible light photocatalytic water splitting for hydrogen production from N-TiO2 rice grain shaped electrospun nanostructures

We report on the visible light-driven hydrogen production from splitting of water molecules by nitrogen-doped TiO₂ (N-TiO₂) with a rice grain-like nanostructure morphology. The N-TiO₂ nanostructures are prepared using sol-gel and electrospinning methods followed by post-annealing of the composite nanofibers. The nanostructures are characterized by microscopy and spectroscopy. First order rate constants for the visible light-assisted photocatalysis in the degradation of methylene blue (MB) dye are found to be 0.2 × 10⁻³ and 1.8 × 10⁻³ min⁻¹ for TiO₂ and N-TiO₂ (5 wt% of nitrogen), respectively. The N-TiO₂ utilized in water splitting experiments and evaluated hydrogen (H₂) of 28 and 2 μmol/h for N-TiO₂ and TiO₂, respectively. The improvement may be attributed due to the N-doping and higher surface area as ∼70 m²/g.