Mixed Gas Stream Research Articles

Comments On the Effect of Gas Velocity On Oxygen Index Measurements

For certain materials, the velocity of the mixed gas stream used in an oxygen index determination has been reported to exert a strong influence on the ex perimental result. It is now possible to rationalise these reported dependences which are shown to result from the form of column used in the test. A proposed modification to the column outlet eliminates the dependence of oxygen index on gas velocity over the range of gas velocity permitted by the testing standards.

Oxidation of mixed copper-iron sulfide

A rectangular plate of mixed copper-iron sulfide composed of bornite (Cu5FeS4) and troilite (FeS) was oxidized in an O2-Ar mixed gas stream at 1023 to 1123 K. At the start of the oxidation, iron was preferentially oxidized with the rapid formation of a dense Fe3O4 layer of about 10 μm thickness on the sample surface, without the evolution of SO2 gas. Following this reaction, layers of both Fe3O4 and Fe2O3 grew on the sulfide surface in accordance with the parabolic rate law. The diffusion of iron through the oxide layers was assumed to control the oxidation rate during this stage. The effect of oxygen partial pressure on the parabolic rate constants was minor and an apparent activation energy of 126 kJ/mol was obtained. During the later stages of the reaction, when the sulfur activity in the inner sulfide core increased, the oxidation proceeded irregularly to the interior of the remaining sulfide with the formation of a porous oxide and the evolution of gaseous SO2. The remaining sulfide core was found to be a mixture of bornite (Cu5FeS4) and djurleite (Cu1.96S).

An automated submicrogram determination of selenium in vegetation by quartz-tube furnace atomic-absorption spectrophotometry

An automated method for the determination of submicrogram amounts of selenium in vegetation is described. A weighed sample of vegetation is digested with a 4:1 nitric-perchloric acid mixture, and made up to a known volume. The digested sample is placed in a Technicon sampler and reacted with sodium borohydride solution. The selenium converted into the gaseous hydride is swept by an argon stream into a gas-liquid separator. The mixed gas stream is passed through a heated quartz cell, positioned in the light-path of an atomic-absorption spectrophotometer. The absorption by the atomized selenium is recorded. The method is capable of analysing 50 samples a day by the use of a calibration curve or 25 a day by the standard addition technique. A relative standard deviation of better than 10% and a detection limit of 0.025 μg g were obtained.

Chlorination-Volatilization Processing of Irradiated Uranium Dioxide, (II)

A study was made on the decontamination of F.P. from irradiatcd UO2 fuel by means of a sorption-desorption process using BaC12 bed. A very high degree of decontamination was obtained. Irradiated UO2 pellets were pulverized through a repeated oxidation-reduction process, and then chlorinated with CCl4 vapor at 580°C. The gas containing the vapor of the chlorides formed thereupon was passed through the BaCl2 bed whose temperature varied along its length from 500° to 100°C. The vapor of the chlorides was sorbed on the bed. From this bed, zirconium and niobiutn chlorides were selectively desorbed by maintaining the bed at batween 460° and 480°C in a mixed gas stream of Ar and CCl4 vapor. The uranium chlorides, remaining on the bed, were then desorbed by maintaining the bed at 500°C in a mixed gas stream of Ar, Cl2 and CCl4 vapor. Cesium chloride accomparlied the uranium chlorides in this process. Cerium and ruthenium chlorides remained undesorbed on the bed after both desorption processes. The vapor of uranium chlorides desorbed was trapped to recover the U. The γ-decontamination factor of the U recovered after 1, 2 and 3 cycles of the sorption-dcsorption process was of the order of 102, 103 and 104, respectively.

Chlorination-Volatilization Processing of Irradiated Uranium Dioxide, (I)

A study was made on the decontamination of F.P. from irradiatcd UO2 fuel by means of a sorption-desorption process using BaC12 bed. A very high degree of decontamination was obtained. Irradiated UO2 pellets were pulverized through a repeated oxidation-reduction process, and then chlorinated with CCl4 vapor at 580°C. The gas containing the vapor of the chlorides formed thereupon was passed through the BaCl2 bed whose temperature varied along its length from 500° to 100°C. The vapor of the chlorides was sorbed on the bed. From this bed, zirconium and niobiutn chlorides were selectively desorbed by maintaining the bed at batween 460° and 480°C in a mixed gas stream of Ar and CCl4 vapor. The uranium chlorides, remaining on the bed, were then desorbed by maintaining the bed at 500°C in a mixed gas stream of Ar, Cl2 and CCl4 vapor. Cesium chloride accomparlied the uranium chlorides in this process. Cerium and ruthenium chlorides remained undesorbed on the bed after both desorption processes. The vapor of uraniu...

Chlorination-Volatilization Processing of Irradiated Uranium Dioxide, (I)

A study was made on the decontamination of F.P. from irradiatcd UO2 fuel by means of a sorption-desorption process using BaC12 bed. A very high degree of decontamination was obtained. Irradiated UO2 pellets were pulverized through a repeated oxidation-reduction process, and then chlorinated with CCl4 vapor at 580°C. The gas containing the vapor of the chlorides formed thereupon was passed through the BaCl2 bed whose temperature varied along its length from 500° to 100°C. The vapor of the chlorides was sorbed on the bed. From this bed, zirconium and niobiutn chlorides were selectively desorbed by maintaining the bed at batween 460° and 480°C in a mixed gas stream of Ar and CCl4 vapor. The uranium chlorides, remaining on the bed, were then desorbed by maintaining the bed at 500°C in a mixed gas stream of Ar, Cl2 and CCl4 vapor. Cesium chloride accomparlied the uranium chlorides in this process. Cerium and ruthenium chlorides remained undesorbed on the bed after both desorption processes. The vapor of uraniu...

Thermal and Electrolytic Palladium Alloy Diffusion Cells

In this article the performance of thermal diffusion cells extracting pure hydrogen from mixed gas streams is discussed and the relationships between gas quality, output and extraction efficiency are summarised for convenience in the form of a graph applicable to any silver-palladium unit. Small quantities of ultra-pure hydrogen can also be generated by electrolytic diffusion, and the characteristics of a small prototype electrolytic cell are described and possible applications suggested.

Gas absorption accompanied by chemical reaction: A study of the absorption of carbon dioxide in aqueous solutions of monoethanolamine

AbstractExperiments were conducted on the absorption of carbon dioxide in aqueous solutions of monoethanolamine in a very short wetted‐wall column.When the absorption was effected from pure carbon dioxide streams, the results conformed to a theoretical relation for absorption combined with very fast second‐order reaction. This is in accordance with expectations based on the probable mechanism and rate of the reaction. The data indicate that there is no appreciable effect of nonequilibrium at the interface for this particular reaction system over the range of exposure times studied.When mixed gas streams were used, it was necessary to resort to empiricism to correlate the data, although the correlating expression arose from theoretical considerations.