CATALYTIC CRACKING OF TARS FROM COAL DEVOLATILIZATION

A set of runs were performed on the catalytic and thermal cracking of the tars present fn the gasifier off-gas stream; the cracking referred to here Js essentially hydrocracking, in view of the considerable amount of hydrogen being present in the gas stream. The catalyst evaluated for tar cracking was a commercial cobalt-molybdenum catalyst, suppported on γ-Al₂O₃(Katalco-477). It was observed that there was a decrease in the amount of tar obtained with the cracking unit on-line with the gasifier; the tars were cracked to gaseous products in the presence of catalyst. Furthermore, it appeared that higher ring structures were transformed to less heavier components; thus cracking could become beneficial in downstream processing of the gas stream coming out of a gasifier.     

Photoluminescence,Judd–Ofelt analysis and photometric characterization of Eu<Superscript>3+</Superscript> activated Ca<Subscript>0.5</Subscript>Gd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> red phosphor

The red emitting Ca_0.5Gd(WO₄)₂:Eu³⁺ was synthesized by a solid-state reaction method. X-ray diffraction patterns were used to characterize crystal structure as well as phase purity. The results suggest that the as synthesized powder phosphor possess scheelite crystal structure with tetragonal symmetry along with the space group of I4₁/a. SEM studies reveal that the as synthesized sample show polyhedral morphology with particle size of 5.5 µm. Photoluminescence excitation spectrum depicts that a broad band (from 200 to 300 nm) centered at 242 nm is attributed to the ligand to metal charge transfer transition of WO₄ ^2? and three intense with sharp absorption bands (observed at 394, 464 and 535 nm) are designated as f–f electronic transitions of Eu³⁺. Photoluminescence emission studies indicate that, under 394 nm UV excitation, a hypersensitive red emission was observed at 617 nm due to the transition from upper ⁵D₀ level to the ⁷F₂ lower level of Eu³⁺ ion. The spectroscopic behaviour of the as synthesized phosphor Ca_0.5Gd(WO₄)₂:Eu³⁺ was determined using Judd–Ofelt theory. The CIE color coordinates, colour correlated temperature and luminous efficacies of radiation were estimated. The as obtained results indicating that the Ca_0.5Gd(WO₄)₂:Eu³⁺ red phosphor is most suitable for solid state lighting applications.     

Preparation and characterization of sputtered Cu films containing insoluble Nb

Copper films containing various amounts of insoluble Nb (up to 24.7 at.%) were prepared by r.f. magnetron sputtering. The crystallography and microstructure of the films were investigated for as-deposited and annealed Cu(Nb) thin films. Cu(Nb) thin films are found to consist of non-equilibrium supersaturated solid solution of Nb in Cu with a nanocrystalline microstructure. X-ray diffraction and scanning electron microscope analyses revealed a reduction in the grain sizes of the films with increasing Nb content in the films leading to a grain refinement. The electrical resistivity of as-deposited and annealed Cu(Nb) thin films is found to be low for an Nb content 2.7 at.%. Significant drops in the resistivity were observed for the high Nb contents after annealing at 530 °C which may be due to grain growth and formation of Nb-bearing phase in the film. Microhardness of the films was found to increase with the Nb concentration due to the combined effects of grain refinement and the solute strengthening of Nb.     

Making Nonwoven Fibrous Poly(ε‐caprolactone) Constructs for Antimicrobial and Tissue Engineering Applications by Pressurized Melt Gyration

A pressurized melt gyration process has been used for the first time to generate poly(ε‐caprolactone) (PCL) fibers. Gyration speed, working pressure, and melt temperature are varied and these parameters influence the fiber diameter and the temperature enabled changing the surface morphology of the fibers. Two types of nonwoven PCL fiber constructs are prepared. First, Ag‐doped PCL is studied for antibacterial activity using Gram‐negative Escherichia coli and Pseudomonas aeruginosa microorganisms. The melt temperature used to make these constructs significantly influences antibacterial activity. Neat PCL nonwoven scaffolds are also prepared and their potential for application in muscular tissue engineering is studied with myoblast cells. Results show significant cell attachment, growth, and proliferation of cells on the scaffolds.

     

DEVOLATILIZATION STUDIES ON A BITUMINOUS COAL UNDER VARIOUS GAS ENVIRONMENTS

ABSTRACT

Devolatilization of a bituminous coal was studied in the temperature range 3 50°C to 550°C and at two pressures: 30 psig and 375 psig. Three separate particle sizes were investigated: (?2, +l),(?4, +3) and (?9, +6) mm. The runs, lasting up to 30 minutes, were carried out under two different types of flowing gas environments: a synthetic gas mixture of composition similar to that entering the devolatilization zone from the gasification zone below in a fixed bed gasifier, and containing 3% steam by volume; and, a helium-steam mixture, also containing 3% steam by volume.

The gas evolution rates from devolatilization show a peak at 5–10 minutes from the start of a run and then gradually taper off to zero as the run progresses. The concentration of methane in the off-gas stream is observed to be higher in the helium runs. There, however, is no significant effect of gas environment on the molecular weights of the tar, which show a maximum in the range 300–500. The tar yields, however, are higher for the helium runs; in all cases, the tar yields peak at 4 °C. The gas yield, however, is higher for the reactive gas environment. The total volatiles yield appears independent of particle size; however, it seems to increase with pressure, over the temperature range studied.