Engineering Transportation

Controlled Atmospheres for Heat Treatment by R. Nemenyi

By R. Nemenyi

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1 COMPOSITION OF ATMOSPHERES PRODUCED FROM PROPANE, AND THE QUANTITY PRODUCED FROM 1 M 3 AT N T P Properties of Exogas Atmospheres 49 FIG. 2 COMPOSITION OF ATMOSPHERES PRODUCED FROM TOWN GAS, AND THE QUANTITY PRODUCED FROM 1 M 3 AT N T P FIG. 2 CONSTRUCTION AND OPERATION OF EXOTHERMIC GAS GENERATORS The main parts of the exothermic gas generator are: mixer, retort, gas cooler and dryer. The mixing equipment provides an appropriate ratio of air to base gas. The resulting hot gas mixture is quenched and most of the water vapour produced during the combustion reaction is condensed and removed.

For perfect combustion the air factor Λ = 1 while for partial combustion it is less than 1 (Λ < 1). Referring to the diagram of Fig. 8 to 1 The limit of 5% combustibles (CO + H 2 ) can easily be reached using a slight deficiency of air, as shown on the graph. The main phases of prepared nitrogen-base or monogas production are: burning of the combustible base gas with a slight deficiency of air to give a very lean exogas; conversion of the CO content of the resulting atmosphere to carbon dioxide; removal of carbon dioxide formed during Prepared Nitrogen-base or Monogas Generators 59 F I G .

Hydrogen is used as a protective atmosphere in the following applications: annealing of stainless and heat-resistant steels, other high-alloy steels, low-carbon steels and non-ferrous metals, reduction of metal powders and sintering of powder metallurgy products/ 11) Its decarburising power is utilised, for example, in the decarburising annealing of dynamo and transformer iron sheets. This decarburising power can be increased by the addition of small amounts of water vapour. (19) Hydrogen can be obtained by the electrolysis of water, catalytic cracking of hydrocarbons or the dissociation of ammonia.

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