US1011014A - Process of manufacturing oxids of nitrogen. - Google Patents

Description

0. BEN D BR. PROCESS OF MANUFACTURING OXIDS-0P NITROGEN,

APPLICATION IILE D APILG, 1909. 1,1 1,1 Fig 6/ Patented Dec.5,1911

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PROCESS OF MANUFACTURING OXIIDS 0F NITROGEN.

Specification of Letters Patent.

Fatented 5, full lpplicationfiled April 6, 1909. Serial No. 488,203.

This invention relates to an improved process for manufacturing oxids of nitrogen.

by oxidizing atmospheric nitrogen at high temperatures produced by burning hydrogen or substantially gaseous or gasified liquid combustible material or fuel such as water gas, illuminating gas, natural gas, methane or petroleum vapors in an atmosphere rich in oxygen.

By means of the present invention in creased yields of oxids of nitrogen are obtained.

Comparative systematic experiments have shown that the oxidation of atmospheric nitrogen in a flame produced by burning. combustible materials -containing hydrogen depends not only on the temperature used but also upon a number of other facts which considerably affect the result and which were hitherto unknown or the importance of which was not understood. First I have found that the yield in oxids of nitrogen greatly depends upon the perfect mixing of the combustibles with the gaseous mixtures supplied for combustion, at the moment when the flame is formed. The theoretical reason for this is to be found in the fact that the completion of the reaction between nitrogen and oxygen requires a measurable interval of time which is scarcely shorter than that which is at thedisposal of the gases from the commencement of the flame reaction to the end thereof. i When a part of this time is taken up by the diffusion of the gases infer se, the remainder will be insufficient for establishing the theoretically possible equilibrium between the oxid of nitrogen and the remaining constituent parts of the burning gases The yield of oxid of nitrogen will therefore approach more and more the theoretical yield. the more perfectly the time occupied by the gases in flowing through the flame is utilized for forming the equilibrium' at the given.

temperature between nitrogen, oxygen, car bon or the remaining materials taking part in the combustion, This fact had not been taken into account in the previously known processes of manufacturing oxids of IlllIOr gen according to which the flame formed by burmng combustible materials is sup plied with the other components (air or mixtures of nitrogen and oxygen richer in oxygen than air) by partially forcing them in from the side and partially by blowing them into the same, so that consequently the yields remained relatively moderate According to the present inventionthe perfect mixing of the combustible materials (which has been recognized as an important factor).

with the air or with air and oxygen miX- tures during the combustion is obtained in a specially effective manner by dividing the flame into numerous small pointed flames, the mixing being elfected at the commencement or first stage in the formation of the flame by supplying the required quantity of nitrogen and oxygen to each separate pointed flame to such an extent that the perfect mixing is already completed during the commencement or first stage in the formation of the flame. Further it was found that in order toobtain the'absolutely necessary complete combustion of all the carbon in the combustible or fuel to form carbonic acid a considerable surplus of oxygen is necessary. It is undesirable to obtain this surplus of oxygen by increasing the supply of atmospheric air owing to thelarge amount of nitrogen supplied at the same time which nitrogen is useless and unnecessarily absorbs heat. It is found however that the cou-ibustion of the finely divided fuel is facilitated in air enriched with such a quantity of oxygen that the mixture contains 50 to per cent. of oxygen and 50 to 10 per cent. of nitrogen. The quantity of this mixture is preferably such that the products of combusion contain 10 to '50 per cent. of free oxygen per volume by the use of which temperatures of from 1600 to 2500 are obtained in the hottest portion or Zone of the combustion-chamber. Under those conditions a surprisingly large proportion of nitrogen will be oxidized in the flame.

In order to protectthe oxids from decom-' position which could easily happen as is well known. the mixture produced by the reaction'and containing in addition to oxid of nitrogen carbonic acid, .free oxygen,

nitrogen, and-the water formed by burning removed at once without being allowed to return into the combustion chamber. This is done by means of cooling devices which are arranged immediately adjacent to the reaction zone and which consist preferably of cooled tubes, pipes or the like which are so arranged that the water condensed on them is either run off to the outside or collects in a condensation vessel. As the combination of nitrogen oxid with oxygen can only take place after the separation of the Water of condensation, the latter is entirely free, or almost so, of nitric acid.

The whole process is carried out in a furnace shown diagrammatically in the accompanying drawings.

Figure 1 is a vertical section thereof and Fig. 2 a horizontal section.

This furnace comprises a casing a lined with fire resisting material. A grate or burner b, composed of communicating tubular grate-bars, is disposed horizontally across the lower part ofthe casing. Some one of said bars communicates with an inlet. pipe through which fuel gas is introduced into all of the bars, and all of the bars are provided with numerous very-small orifices through which the fuel passes. As illustrated, small tubes 0 are'mounted over the various orifices of the hollow grate-bars. By this means the combustion of the fuel is forced to take place at the top of said tubes, thus preventing overheating and consequent rapid wear of the grate-bars. Moreover,

the fuel in passing up the tubes 0 receive an advantageous preliminary heating preparatory to combustion. The mixture of air and oxygen flowing up through the pipe .9 and between the grate-bars meets the numerous finely divided jets of fuel gas from the orifices of thegrate-bars or from the tubes 0, and thus immediatelyforms a very intimate mixture. In the group of flames thus formed above the grate, or burner, the formation of oxid of nitrogen takes place.

The cooling system (1 is arranged beyond the' hottest range or zone past which system the reaction gases flow when leaving the furnace, being thus cooled and the condensed water formed by the combustion is drained off from the condensation vessel or trap, e. The cooled and dry re-action gases are then passed on by the pipe f, in order to be further treated so as to form nitric acid or the salts thereof.

It is of course understood that the burner is not restricted to the form described,for instance thenumerous little tubes supplying the combustible or fuel need not be arranged on a. hollow grate in the furnace, but may terminate directly in the furnace and supply the air and oxygen mixture through .merous small or pointed flames to which the quantities of nitrogen and oxygen required for obtaining favorable equilibrium conditions are added and thoroughly mixed with the flame at the commencement or first stage in the formation of the same and further by employing an air and oxygen mixture containing 50 to 90 per cent.- of oxygen in such quantities that the re-action gases contain from 10 to 50 per cent. of free oxygen and that by means of an immediate cooling of the re-actiongases by cooled pipes or the like, the water of condensation formed is drained off. The yield of oxids of nitrogen is increased tenfold or more as compared with that obtained when employing known processes.

I claim- 1. The process herein described of producing oxids of nitrogen, which consists in burning combustibles containing hydrogen in a furnace in the form of numerous small pointed flames, supporting the combustion of said flames with a mixture consisting of nitrogen and 50 to of free oxygen, and condensing the aqueous vapor thus formed.

2. The process herein described of producing oxids of nitrogen, which consists in burning a fuel-gas containing hydrogen in the form of numerous small pointed flames by passing said fuel-gas through very small orifices, supporting the combustion by a mixture of air and oxygen containing 50 to 90% of oxygen in such proportion that the resulting reaction-gases contain 10 to 50% of free oxygen, and cooling the reaction gases to a temperature below 100 (1., thus condensing the water formed by the combustion.

In testimony, that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

OSCAR BENDER.

Witnesses:

WOLDEMAR HAUPT, HENRY Hasrnn.

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