GB234104A - Improvements in methods for the manufacture of nitrogen or a mixture of nitrogen and hydrogen - Google Patents

Abstract

234,104. Hydrazote, (Assignees of Soc. l'Oxhydrique Frangaise). May 19, 1924, [Convention date]. Hydrogen; nitrogen.-In processes for making nitrogen from air or other gases rich in nitrogen and also containing some oxygen such as residual gases obtained in the manufacture of oxygen by liquefying air, or combustion gases by circulating such gases over hot reduced iron, the gases used to reduce the iron oxide produced and/or the gases used to heat the apparatus are obtained from an existing plant such as a blast furnace, coke oven plant or gas works. When combustion gases are used as the source of nitrogen the oxidation of the iron is effected at a comparatively low temperature to avoid the formation of carbon monoxide and the sulphur dioxide and carbon dioxide are removed from the remaining nitrogen by scrubbing with water under pressure or by treatment with alkalies. In a modification of the process, a mixture of nitrogen and hydrogen is obtained by passing steam over the reduced iron after it has been partially oxidized by the passage of air. The process may be effected with or without pressure; but pressure is preferably employed when the nitrogen is to be used in the synthesis of ammonia. The reaction chamber may comprise a number of tubes made of cast-iron or refractory material set in a mass of masonry 1, Fig. 1, strengthened by a plate-iron shell 5 so as to withstand pressure. Gas enters by a pipe 6 to a chamber 7 above the tubes and passes from the lower end of the tubes to the outlet pipes 8 each provided with a valve 9. The tubes may also be arranged in seriesparallel. In one such arrangement, Fig. 3, the reaction chamber comprises four sets of five retorts 16. Partitioned chambers may also be used. In the arrangement of plant shown in Fig. 5, the heating of the apparatus as well as the reduction of the iron oxide is effected by gases from a coke-oven plant. The distillation gases pass from the ovens 41 through a collecting drum 45 to condenser 46. By-products separate in an apparatus 47 and the uncondensed gases are normally, in part withdrawn through pipe 50 and in part passed to the burners under the ovens 41. To reduce the iron oxide formed in the nitrogen-producing apparatus the coke-oven gas is led through a heat interchanger 53 and heat accumulator 51 to the reaction chamber 52, the hot residual gases being returned to the cokeoven plant after passing through the heat interchanger 53. When the reduction is complete hot air from the coke-oven heat recovery apparatus 43 is led through heater 51 to the reaction chamber 52, the hot nitrogen being passed through a heater 54, used for heating water, and scrubber 56 to holder 55. Specification 206,822 is referred to. According to the Specification as open to inspection under Sect. 91 (3) (a) the reducing and heating gases may be specially produced as in the plant shown in Fig. 6 (Cancelled), in which water gas from generators 21 is forced through a heat interchanger 23 by means of a blower 22 and then passes through a heated brick heataccumulator 25 to a reaction chamber 30. The gases leaving the latter after heating the heat interchanger 23 are supplied to the burners of the heat accumulator 25. The reaction being complete, the supply of water gas is stopped and air is passed through the plant; usually, however, it is unnecessary to pass the air through the heat accumulator 25. The hot nitrogen leaving the heat interchanger 23 passes through a scrubber to a gas-holder. Preferably a second set of apparatus is employed so that while reduction is being effected in one set, nitrogen is being produced in the other. Some of the reducing gas may be used for heating the reaction chamber. This subject-matter does not appear in the Specification as accepted.