The demand for oxygen for industrial proeesscs whi ch has been steadily growing since the liquefaction method of alr separation was introduced fifty years ago has, until recently, been met by extension of t h e .. clas sical proccss " nod csp ceially by the production of liquid oxygen on a large scale. The usc of liquid oxygen is particularly con venient when the demand is highly irregular and intermittent, as, for instance, in steel-works practice, but tllere is an increasing demand for o""ygen in chemical and metallurgical processes which operate continuously and steadily, and which require oxygen of only moderate purity. 'Vhen the demand for such purposes is large oxygen is best produced in gaseous form in plants opemting at low pressure, and the term" Tonnage Oxygen " has been applied to plants of this type, which supply ox.. ygcn in quantities sometimes of several hundred tons a day. The principles of low temperature air separation are discussed from the point of view of thermodynamic efficiency and the developments which have made possible the low-pressure processes of "Tonnnge Oxygen" production are outlined.
A brief survey is made of the uses of oxygen in metallurgical, gasification, and chemical processes. Oxygen is used in many different ways in the conversion of raw iron to finished steel, and a number of new steel-making processes have been developed which depend on a "Tonnnge Oxygen" supply. Many processes based on solid liquid or gaseous fuels make use of oxygen in the prcparation of synthesis gas for the manufacture of ammonia, petrol, and organic chemical products. Oxygen is also used in the complete gasificntion of coal to produce a fuel gas of high calorific value. In a number of applications the use of oxygen confers the advantage that it enables low-grade raw materials to be processed economically, and an increasing demand for these purposes is predicted.
Resume-La dernande d'oxygene pour les proeedes lndustriels, qui a augmentd eontinuellement