Hot Inert Gas Research Articles

The use of a thermal model of ignition to explain aspects of flameproof enclosure

In an earlier paper (Combustion and Flame19, 187 (1972)) Phillips described the ignition process that occurs when a transient of hot inert gas is ejected into a flammable atmosphere through the equatorial flange gap of an 8-litre sphere for the determination of the Maximum Experimental Safe Gap (MESG) for flameproof enclosure. The analysis of the mechanism of ignition is now extended to take into account changes in flange breadth, vessel volume, internal ignition position, oxygen concentration, humidity, pressure, and ambient temperature. The results of the calculations agree with experimental data.

Ignition in a transient turbulent jet of hot inert gas

The ignition mechanism described by Phillipsis applied to the ignition of a flammable fuel/air mixture by a transient jet of hot inert gas. Calculated minimum jet sizes for ignition for a number of fuels were compared with the maximum experlmental safe gap for a flameproof enclosure. To make the comparison, the rate of entrainment into a transient jet was estimated. The critical gap size depends on jet velocity, but good agreement with experiment was found by taking the minimum critical gap size.

Oxide dispersed copper alloys by surface oxidation

A series of Cu-Al and Cu-Ni-Al alloys, inert gas atomized, as -44 μ powders, were converted to submicron thick flakes covered by copper oxide and aluminum oxide in varying amounts, depending on the initial aluminum content. The flake powders were either hydrogen reduced to eliminate copper oxide, or were reacted in a hot inert gas to increase the Al2O3 content by internal oxidation. A range of alloy compositions were produced by subsequent hot extrusion, yielding excellent room temperature tension and 450°and 650°C stress rupture properties; the alloys are structurally stable from 900°to 1000° C and higher in certain cases. The process is attractive for its simplicity, reproducibility, and resultant excellent properties.

Production of Levoglucosan by Pyrolysis of Carbohydrates. Pyrolysis in Hot Inert Gas Stream

Starch pyrolysis was carried out in a hot gas stream to establish optimum conditions for the production of levoglucosan. Helium, nitrogen, and steam were used. Steam was most effective and convenient because of its high heat capacity and because it is easily condensed. Yields of levoglucosan increased as pressures decreased. The effect of temperature, feed weight, gas flow rate, reduced air pressure, and catalyst on the yield of levoglucosan is reported. Optimum operating conditions for the acid-catalyzed process were established. A maximum yield of 44.5% levoglucosan was obtained from cornstarch.

Studies on the Manufacture of Formed Coke for Blast Furnace

At the Government Industrial Development Laboratory, Hokkaido, the process consisting of low-temperature carbonisation and hot briquetting followed by high temperature carbonisation is being investigated to convert non-or slightly caking coals into metallurgical coke and also to develop a continuous coke-making process. It is based on the technique for making solid smokeless fuel reported previously.This paper relates to low-temperature carbonisation and hot briquetting carried out with a pilot plant of 250kg/hr.Coking coals blended with 30 to 50 per cent of slightly caking coals of 1 to 11/2 in free swelling index are crushed and carbonized at 410-450°C in a fluidized bed carbonizer provided with a stirrer. Hot fine coals are formed while still hot by a double roll press.At first air was used as a fluidizing gas and then it was replaced by hot inert gas. Bed temperature was controlled within ±5°C by means of automatic feed control. In this way, briquet coke high in strength became obtainable.Secondly, a pre-heater of fluidized bed was added in series before the carbonizer. Though the effects of shortening of residence time in the carbonizer on coke quality were little recognized, the capacity of the carbonizer was much increased. From these results, a compound fluidized carbonizer was proposed.As regards high temperature carbonisation, a fluidized medium carbonizer of horizontal type is still in the stage of laboratory scale, experimental results being briefly described.

Production of Levoglucosan by Pyrolysis of Carbohydrates Pyrolysis in Hot Inert Gas Stream

AbstractStarch pyrolysis was carried out in a hot gas stream to establish optimum conditions for the production of levoglucosan. Helium, nitrogen, and steam were used. Steam was most effective and convenient because of its high heat capacity and because it is easily condensed. Yields of levoglucosan increased as pressures decreased. The effect of temperature, feed weight, gas flow rate, reduced air pressure, and catalyst on the yield of levoglucosan is reported. Optimum operating conditions for the acid‐catalyzed process were established. A maximum yield of 44.5% levoglucosan was obtained from cornstarch.

Thermal stability of a hot inert gas bubble in a cool reactive liquid

The behaviour of a hot inert gas bubble in an infinite sea of cool reactive liquid has been investigated utilizing a temperature-profile method of Spalding. ‘Inner solutions’, valid for small values of the time, have been found by singular perturbation methods for (i) an initial stepped temperature distribution and (ii) a hot gas bubble surrounded by a thermal layer. These have been taken to represent two extreme physical situations, instantaneous contact of the bubble with the liquid and the initial heating of the bubble and surrounding liquid by adiabatic compression. It has been shown that the early stages of the process in (i) are characterized by a rapid fall in temperature, with the bubble volume remaining approximately constant and chemical reaction playing no part. For (ii) the bubble temperature and volume initially increase, and this represents a supercritical situation which finally leads to thermal explosion.

Determining bleaching loss coefficients

Detailed description has been given of a laboratory method for determining oil retention by bleaching earths and carbons. The method involves determination of the increase in weight resulting when a sample of the bleaching material is treated with oil and the excess oil removed by suction in a stream of hot inert gas under standardized conditions. The oil retention values obtained by this method fall within the range of those observed under practical conditions of plant operation.