DE2326884A1 - METHOD AND DEVICE FOR THE CATALYTIC OXYDATION OF AMMONIA - Google Patents

Description

PATENT ANWALTSBÜRO TlEDTKE - BüriLING - KlNNE 2326884

TEL. (0811) 539653-56 TELEX: 524845 ti pat CABLE ADDRESS: Germaniapatent Munich

8000 Munich 2 Bavariaring4

P.O. Box 202403 May 25, 1973 B 5420

Imperial Chemical Industries Limited London, UK

Method and device for the catalytic oxidation of ammonia

The invention relates to a method and a device for the catalytic oxidation of ammonia to produce nitrogen oxides, e.g. the production of nitric acid are to be used, the oxidation in particular using a other catalyst than such a metal catalyst from the platinum group is to be made in all-metal form.

It has long been the subject of studies to find an alternative to the platinum group metal catalysts, which are the only satisfactory catalysts for the oxidation of ammonia so far. Recently results have been obtained using particulate Oxydkatalysatoren, including spherical sintered cobalt oxide, wherein 3 ^e 4PjAj i ^^ ^ J-SASI lt ^Wurc ^ ^e "that this

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Material differs from metal catalysts in certain areas behaves in the platinum group, creating the immediate replacement of platinum metal lattice catalysts through a bed of particulate! Catalyst did not lead to "fully satisfactory results.

It has now been discovered _s that the method, .- as it is usually used to oxidation over a platinum metal catalyst to trigger, ie local heating leads with a flame for local deactivation of a Kobaltoxydkatalysators and does not lead to a satisfactory progress of the reaction throughout the catalyst A new method and apparatus has now been developed which alleviate this difficulty and which can be used whether or not a particulate oxide catalyst is used.

According to the invention a method for catalytic Oxidation of ammonia started by making the catalyst essentially uniform with flowing Hot gas is heated until the catalyst has reached the trigger temperature for ammonia oxidation.

The ammonia / air reaction mixture is very advantageously used as the flowing hot gas. The gas can with ' However, it is advantageous to use suitable equipment, e.g. to be heated by indirect heat exchange warmed up by a chemical reaction resulting in this

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Mixture takes place. The combustion of hydrogen is suitable for this, as this takes place quickly enough - to the to achieve the required rapid temperature increase, so that a considerable passage of non-oxidized ammonia / Air mixture is prevented and undesired by-products are not generated. . .

The hydrogen flame is preferably in one Space formed in the oxidation reaction vessel above the area occupied by the catalyst. very hydrogen is advantageous over a large number of Feeding points introduced into this area * to ensure uniformity To ensure warming up of the gas phase and thus the catalyst.

In carrying out the process, the stream of ammonia and air to be subjected to the reaction becomes advantageously fed to the catalytic converter before the hydrogen flame is ignited. d. This changes the process quickly and smoothly from the start-up phase to the production phase. In order to achieve more effective mixing, a separate air supply is expediently provided to the To increase the mass of hot gas compared to the mass of reaction gas. The air supply does not have to be for burning the Hydrogen, provided that there is already enough air in the reactor.

If the catalyst bed is level, the 309884/097 7

Hydrogen or the air or both, preferably tangential to circles in a plane transverse to the direction of flow of the Reaction gas fed in to increase the efficiency Increase mixing by placing the gas mixture in a " Rotational movement offset. If the catalyst bed is not flat, the hydrogen flame will preferably be parallel in one zone formed on the surface of the catalyst bed.

The catalyst is preferably placed in a multi-tray or tubular or conical bed, as is is described in British patent applications 26 131/72 and 26 132/72.

The preferred catalyst is a cobalt oxide catalyst, preferably such as that disclosed in the UK Patent application 46 775/70 (FR-PS 2 109 930) is described, whose subject matter is part of this description.

The invention also provides a reactor for carrying out the process and a hydrogen burner for heating the gas flowing over the catalyst.

Burners of the type as they are in the start-up process can be used according to the invention and a device for blowing through combustible gas have a surface area and a device for blowing through the ^ combustion supporting gas, one or both gases being blown in tangentially,

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appear new and of particular value in any situation where it is desired to quickly become a volume element of a to heat the flowing gas, for example to obtain a mass of hot gas or to warm up catalysts, which differ from those used for ammonia oxidation, as well as those with which the invention is mainly concerned.

A preferred reactor for use in the process of the invention is shown in the attached schematic Drawings clarified in which

Fig. 1 is a cross-sectional view and

FIG. 2 shows a sectional view along the line 2-2 in FIG. 1.

Numeral 10 denotes the upper portion an ammonia oxidation reactor; this upper section ends at its lower end in a flange 12 which connects to the lower portion of the reactor. The lower section is made of cooling tubes or surrounded by a water jacket, but these parts are not shown. The catalyst bed 24 is on one Metal grid layer 26 supported, in turn by layers 30 made of a honeycomb framework and a metal frame construction 31 is supported. Above the catalytic converter there is a frame structure 76 on a ring 77 that forms the bed

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surrounds and is supported towards its center by anchors attached to the sloping wall of the kettle hang down, the frame structure 76 hanging rails or hangers 80 for atomizers or showers 8 2 and 84 wearing. The showers or distributors 82 are used for hydrogen; they carry nozzles 86 that point down and are over a central hub 87 fed by the tube 90. The showers or manifolds 84 are used for Air. They are provided with holes 8 8 which each point horizontally in alignment with a hydrogen nozzle, see above that the hydrogen mixes with the air and the mixture flows tangentially in the plane of the reactor. The distributors 84 are fed via a central hub 89 which is supplied via the pipe 72. Numeral 94 is a Spark plug for igniting the hydrogen / air mixture for the purpose of heating the catalytic converter.

The nozzles and distributors or showers are in The boiler is stationary, but the hydrogen / air flames are directed tangentially, thereby releasing the process gas is rotated so that a well mixed stream of hot gas is uniform with the catalyst comes into contact.

In an alternative burner design, the hydrogen is promoted through the lower manifold or shower head and increases with regard to the very low Density in the air currents, which are now conveyed horizontally

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be changed. In this embodiment, slots are preferably provided as hydrogen outlets, possibly a single slot for each spoke of the burner or a slot in the form of a channel ₉ which is formed on the spokes and is supplied through the nozzles. In this embodiment, a single flowing hydrogen curtain or veil is generated, which can be ignited quickly from a single ignition point.

In any arrangement, the distance between the nozzles or openings or the width of the conveyor slots should be such that that hydrogen and air are supplied at a uniform rate per unit area of the reactor plane. So should they openings are closer to one another in the direction of the circumference than in the direction of the center.

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Claims (7)

Patent claims 1. A method for the catalytic oxidation of ammonia, characterized in that it is thereby initiates that the catalyst is heated substantially uniformly with flowing hot gas until the catalyst Has reached the trigger temperature for the ammonia oxidation. · ' 2. The method according to claim 1, characterized in that the flowing gas is the ammonia / air reaction mixture. 3. The method according to claim 1 or 2, characterized in that the flowing hot gas by the combustion is heated by the hydrogen contained therein. M-. Method according to claim 3, characterized in that the combustion of hydrogen takes place in a room in the oxidation reaction vessel above the range ", which is ingested by the catalyst. 5. The method according to claim 4, characterized in that the catalyst bed is flat and hydrogen and / or air is supplied tangentially to circles in a plane which is transverse to the direction of flow of the flowing hot gas lies. 6. The method according to one or more of the preceding Claims, characterized in that the catalyst 3098m / 'OB-7 7: made of cobalt oxide. 7. Device, in particular according to one or more of the preceding claims, characterized by a burner for heating a volume element of a flowing gas with means (82) for the spraying of combustible gas over an area / and by means (84) for spraying the combustion-supporting gas, one or both gases being sprayed in tangentially. 309884/0977 JlO Blank page