Absorption of carbon dioxide in alkanolamines in the presence of fine activated carbon particles

The rates of absorption of CO₂ into water and 0.1 kmol/m³ aqueous solutions of MEA, DEA and AMP were measured in a stirred cell with a flat gas-liquid interface in the presence of fine activated carbon particles. Experiments showed that the rates of absorption increased significantly with increases in the loading of activated carbon up to about 6 kg/m³ and thereafter remained constant.     

Absorption of carbon dioxide into aqueous blends of 2-amino-2-methyl-1-propanol and monoethanolamine

This work presents an investigation of CO₂ absorption into aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA). The acid gas mass transfer has been modeled using equilibrium-mass transfer-kinetics-based combined model to describe CO₂ absorption into the amine blends according to Higbie's penetration theory. The effect of contact time and relative amine concentration on the rate of absorption and enhancement factor were studied by absorption experiment in a wetted wall column at atmospheric pressure. The model was used to estimate the rate coefficient of the reaction between CO₂ and monoethanolamine at 313 K from experimentally measured absorption rates. A rigorous parametric sensitivity test has been done to identify the key systems’ parameters and quantify their effects on the mass transfer using the mathematical model developed in this work. The model predictions have been found to be in good agreement with the experimental rates of absorption of CO₂ into (AMP+MEA+H₂O).     

The architecture of a knowledge-based process planning system for small scale industriee

The objective of this paper is to describe a knowledge-based system to assist engineers to generate optimum process plans. The knowledge base is defined using a PASCAL-like language and is maintained in the form of PROLOG sentences. The knowledge base may be readily modified by process planners to meet their specific requirements. An inferece engine systematically tries to apply the rules to generate basic process plans. These plans are then optimised by repeated applications of user difined rules. The system is being written in PROLOG.     

Component description for knowledge based process planning

The International Journal of Advanced Manufacturing Technology - This paper discusses a number of possible strategies for specifying the geometric characteristics of a part to be manufactured using...     

Microstructural Characterization and Mechanical Properties of Si3N4 Formed by Fused Deposition of Ceramics

We present processing (green and sintered), part shrinkage and warping, microstructural characterization, and mechanical properties of Si₃N₄ made by fused deposition of ceramics (FDC), using optical microscopy, scanning electron microscopy, and X-ray diffraction. The mechanical properties (fracture strength, fracture toughness, and Weibull modulus) are also reported. Proper FDC build parameters resulted in dense, homogeneous, near-net-shape Si₃N₄, with microstructures and mechanical properties similar to conventionally processed material. Mechanical properties are shown to be isotropic, while there is some degree of microstructural texturing (preferred β-Si₃N₄ grain orientation) in sintered components.     

Surface Modification of Synthesized Nanozeolite NaX with TEAOH for Removal of Bisphenol A

In the present study, the surface modification of a freshly synthesized nanozeolite NaX was done with tetraethylammonium hydroxide (TEAOH) and applied as an adsorbent for the removal of bisphenol A (BPA) from its aqueous solutions. The adsorbent was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the synthesized adsorbent can remove BPA rapidly and effectively because of its high surface area (572 m²/g) and small particle size (35 nm). Uptake of BPA was greatly influenced by pH, stirring rate, temperature, contact time, and adsorbent dose. The optimum values of these parameters were 10.5 pH, 250 rpm, 25°C, 2 h, and 0.6 g/L. The adsorption was found to be spontaneous and exothermic. The Freundlich isotherm model and pseudo-first-order kinetic model fitted the experimental results well. The monolayer and multilayer adsorption capacities were found to be 42.8 and 122.6 mg/g, respectively.     

Alkali metal modified nano-silicalite-1: an efficient catalyst for transesterification of triacetin

Nanocrystalline Silicalite-1 was synthesized by conventional hydrothermal method and transformed into efficient solid base catalyst by modification with alkali metals like lithium, potassium and cesium. The synthesized and modified catalyst was characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption/desorption, Infra-red spectroscopy, thermogravimetry and basicity determination. The catalysts were tested for transesterification reaction of short triglyceride triacetin with methanol. 1–3 wt% alkali metal ions have been loaded on nano Silicalite-1 and used for transesterification reaction. Among the tested catalyst, 3 % potassium loaded Silicalite-1 (KS-3) showed highest reactivity giving 94 % triacetin conversion, and 98 mol% selectivity for methyl acetate. Reaction parameters such as triglyceride/alcohol molar ratio, catalyst amount, time and temperature were optimized with KS-3 catalyst. Kinetic studies were also done and found that transesterification of triacetin follows first order dependence.     

Dielectric behavior of polystyrene foam at microwave frequency

Polystyrene foams have been generated and fabricated into differently shaped structures', by change of steaming period under constant impregnation time and solvent-nonsolvent composition. Optical photomicrographs of samples both plain and wax-copper-coated reveal uniform appearance, distinct grain-boundaries, and random cell size distribution. Dielectric measurements have been made on test specimens cut according to wave-guide size at 9.375 GHz X-band microwave frequency by short-circuited wave-guide method of Smith and Hippel modified by Dakin and Works. Dielectric constants are linear, on direct and semi-log scales in bulk-density and volume-fraction, obeying Weiner's inequalities. Formulae of Landau-Lifshitz, Beer, Maxwell-Wagner, Odelevsky, etc. have been tried. Data fit best with the logarithmic law of Lichtenecker and Rother. Specific polarization is also a true function of density. Dielectric constant vs bulk-density plots of foams resemble dielectric-constant vs fractional-density plots based on the theoretical derivation by Smith for polystyrene compacts, signifying that compacts containing closely-spaced oblong-spherical particles arc physically similar to foams having spherical gas inclusions in plastic structures. Tan δ lying in the range 0.002–0.0038 results from conformational polarization (β-relaxation at room-temperature for wide-angle torsional oscillations of side-groups with co-operative motion from wriggling chains). It is therefore possible for low-loss foam dielectrics suitable for micro-wave applications to be made by this method.     

Alpha-Quartz 2. Crystal chemistry,and nature and distribution of impurities

Crystal chemistry of alpha-quartz is discussed in relation to the nature, concentration and distribution of the common impurities. Two schemes for incorporation of impurities in the host structure,viz., the charge compensation model for untwinned natural quartz, and the broken-bond model for synthetic quartz to accomodate excess impurity residue after charge compensation, are critically reviewed. Another model for the presence of Al-H defects independent of alkali association in natural quartz is suggested. It is pointed out that the growth pressure influences the nature and distribution of impurities as well as generation of planar and line defects in synthetic quartz. It is also established that mechanicalQ (which is a measure of the acoustic loss) of synthetic crystals grown at low pressure deteriorates with increase in impurity content in excess of what is required for satisfying the charge compensation rule.