Method and device for the recovery of nitrous oxide

 

(57) Abstract:

The invention relates to a method and apparatus for recovery of nitrous oxide, formed during the catalytic combustion of ammonia and oxygen to nitrogen oxides. The use of catalysts for catalytic combustion of ammonia and oxygen to nitrogen oxides, comprising at least one first mesh catalyst and at least one second mesh catalyst, at least one first mesh catalyst is a platinum-rhodium mesh, and at least one second and below the mesh catalyst is palladium-rhodium mesh with at least 92 wt.% palladium, 2-4 wt.% rhodium, the rest is platinum. In case of simultaneous use of nets catalyst effectively restored nitrous oxide and increases the conversion of ammonia to nitric oxide. 5 S. and 6 C.p. f-crystals.

The invention concerns a method and an apparatus for recovery of nitrous oxide, formed during the catalytic combustion of ammonia and oxygen to nitrogen oxides, and the use of catalysts for catalytic combustion of ammonia and oxygen to nitrogen oxides, comprising at least one first mesh catalyst is a platinum grid.

A well-known problem in the formation of nitric acid by burning ammonia with oxygen with the formation of suitable oxides of nitrogen is that it produces nitrous oxide (laughing gas), which is associated with the destruction of earth's ozone layer and takes part in its destruction. So, when nitric acid is clearly revealed that the formed N2Additionally, it should effectively destroy or substantially avoid the formation of laughing gas. In this case, the desired output of nitrogen oxides shall not be caused harm.

In the application DE 19819882 A1 describes a method for the catalytic decomposition of N2O in a mixture of gases obtained during the manufacture of nitric acid by catalytic oxidation of ammonia, the catalyst for the decomposition of N2O, characterized in that the hot gas mixture obtained by the catalytic oxidation of ammonia, before the subsequent cooling in contact with the catalyst for the decomposition of N2O.

Patent DE-OS 2239514 describes the location of the grids catalyst to accelerate the reaction between two or more gases rushing through the metal grid, characterized in that directed towards arenoso metal material and less volatile, and cleaned using gas metal material, the operation accelerates the reaction.

In the patent DE-OS 1959137 described catalyst for the oxidation of ammonia to nitrogen oxides with low content of platinum and rhodium from 12 to 20 wt.%.

In Hollemann-Wiberg "Lehrbuch der anorganischen Chemie", 71.-80. edition, publishing house Walter de Gruyter & Co., Berlin, 1971, S. 360, elements described combustion of ammonia to obtain the nitrogen oxides with a catalyst of the platinum mesh and larger multi one above the other arranged on the element burning wire mesh.

In the patent EP 0359286 B1 describes a method for recovery of nitrous oxide, which is formed by the catalytic combustion of ammonia and oxygen to oxides of nitrogen and then cooled in an element of the regeneration heat and is absorbed by the water and/or dilute nitric acid, characterized in that warm the reaction gases are given time retaining abilities from 0.1 to 3 before they are cooled. This allows the formed N2About to re-arrange up to 90%.

In the patent EP 0611041 B1 describes a method of reducing the emission of N2About during the start-up phase oxidation reaction of ammonia with the use of mesh can produce the moreover palladium alloy contains from 0.1 to 5 weight. % cobalt.

In the application DE 19805202 A1 describes a method of obtaining nitric acid, in which ammonia is burned, at least one grid of a catalyst, in particular a platinum grid and the supply of oxygen, and the reaction gases are cooled, and the reaction gases before cooling go down in the direction of the grid of the catalyst over temperature resistant catalyst for the conversion of N2Oh, contained in the reaction gases.

The above methods are characterized by, or a small fraction decomposition of N2Oh, or very high costs related to hardware, which from an economic point of view considered to be disadvantageous.

So was tasked with using method a new genus and apparatus for recovery of nitrous oxide new genus to resolve, at least partially, the above-mentioned disadvantages, in particular to provide an efficient and favorable costs related to equipment, methods and appropriate equipment.

This problem is solved according to the invention, by means of the method according to item 1 or 2, and by means of the device according to item 6 or 7, as well as through the application of item 11.

As for the method according to the Ute at a temperature of about 860oBy direction to the first grid of a catalyst which is a platinum-rhodium mesh with a typical content of rhodium from 5.0 to 10.0 weight. percent, and through the second grid of the catalyst, and this second grid is a palladium-rhodium mesh with at least 92 wt.% (or more) of palladium, 2-4 wt.% rhodium, the rest is platinum, or with alternative 82-83 wt.% palladium, of 2.5-3.5 wt.% rhodium, the rest is platinum, and is highly efficient recovery of the share of nitrous oxide. The grid is denoted by a gas-permeable structure, which is essentially a metal and is made, for example, by knitting, braiding, weaving or receiving layer of a fibrous mass.

Unexpectedly, it was possible to show that thanks to the simultaneous use of both grids of the catalyst according to the invention the resulting number2About from the beginning was able to significantly recover, and at the same time was highly effective education NO.

First and foremost is preferred that the palladium-rhodium mesh is characterized by the content of rhodium from 2.5 to 3 wt.% and the palladium content of 82.5 wt. % as it can be dorogawa mesh placed at a distance from the platinum-rhodium mesh by at least one third of the grid, to avoid the coupling of different types of nets, and as a material for the third grid was suitable heat resisting steel (FeCrAl-alloy, for example, Medarov or Kanthal).

Finally, it may be preferable that the palladium-rhodium mesh contains at least one other metal from the group of iridium, ruthenium, rhenium, cobalt, Nickel, copper, gold, in order to increase the mechanical stability, with the same catalytic action, mesh palladium-rhodium catalyst.

The following examples serve to explain the invention.

1. Tests in the test reactor.

Installation options:

the reactor, test reactor with an effective diameter of 100 mm;

reactor pressure: 5 bar;

load: 10 t/m2per day;

temperature: 865oC;

period of service: 20 days.

Example 1 (standard system): mesh PtRh8+mesh PdNi5.

The selectivity of the conversion of ammonia to nitric oxide: the 95.5-96%.

The emission of N2O: 1000-1200 ppm (parts per million).

Example 2 (comparative example): mesh PtRh8+mesh PdBhl,5.

The selectivity of the conversion of ammonia to nitric oxide: the 95.5-96.

The emission of N2O: 1000-1200 p is ka to nitric oxide: the 94.5-95%.

The emission of N2O: 900-1200 ppm.

Example 4 (invention):mesh PtRh8+mesh PdRh3.

The selectivity of the conversion of ammonia to nitric oxide: the 95.5-96%.

The emission of N2O: 300-500 ppm.

Note: Pd-mesh after using mechanically very weak: have cracks.

Example 5 (invention): mesh PtRh8+mesh PdRh3Pt5.

The selectivity of the conversion of ammonia to nitric oxide: the 95.5-96%.

The emission of N2O: 300-500 ppm.

Note: Pd-mesh after using mechanically weak, but cracks are not.

Example 6 (invention): mesh PtRh8+mesh PdRh3Ptl5.

The selectivity of the conversion of ammonia to nitric oxide: the 95.5-96%.

The emission of N2O: 300-500 ppm.

Note: Pd-mesh after using mechanically stable and have no cracks.

2.1. Testing in an industrial reactor.

Installation options:

reactor: industrial unit with two parallel reactors;

reactor pressure: 4,8;

load: 11,2 t/m2per day;

temperature: 880oC;

the life: 180 days.

Reactor 1 (standard system): mesh PtRh5+mesh PdNi5.

The conversion of ammonia to nitric oxide 95%.

The emission of N2O: 1000 ppm.

2.2. Testing in an industrial reactor.

Installation options:

reactor: industrial reactor;

reactor pressure: 3.5 bar;

load: 5,85 m/m2per day;

temperature: 860oC;

lifespan: 300 days.

Example 1 (standard system): mesh PtRh5+mesh PdNi5.

The conversion of ammonia to nitric oxide: 94-96%.

The emission of N2O: 1200-1600 ppm.

Reactor 2 (invention): mesh PtRh5+mesh PdPtl5Rh3.

The conversion of ammonia to nitric oxide: 94-96%.

The emission of N2O: 400-800 ppm.

1. Method of recovery of nitrous oxide, formed during the catalytic combustion of ammonia and oxygen to nitrogen oxides, and use of catalysts for catalytic combustion of ammonia and oxygen to nitrogen oxides, comprising at least one first mesh catalyst and at least one second mesh catalyst, and at least one first mesh catalyst is a platinum-rhodium mesh, characterized in that the at least one second and the downstream located mesh catalyst is palladium-rhodium mesh with at least 92 weight. % palladium, 2-4 weight. % Roghani ammonia and oxygen to nitrogen oxides, moreover, the use of catalysts for catalytic combustion of ammonia and oxygen to nitrogen oxides, comprising at least one first mesh catalyst and at least one second mesh catalyst, and at least one first mesh catalyst is a platinum-rhodium mesh, characterized in that the at least one second and the downstream located mesh catalyst is palladium-rhodium mesh with 82-83 weight. % palladium, 2.5 to 3.5 weight. % of rhodium, and the rest - platinum.

3. The method according to p. 2, characterized in that the palladium-rhodium mesh is characterized by the content of rhodium 2.5 to 3 weight. % and the palladium content of 82.5 weight. %

4. The method according to one of paragraphs. 1-3, characterized in that the palladium-rhodium mesh placed at a distance from the platinum-rhodium mesh by at least one third of the grid.

5. The method according to p. 4, characterized in that the third grid consists of heat-resistant steel.

6. Device for the recovery of nitrous oxide, formed during the catalytic combustion of ammonia and oxygen to nitrogen oxides, and use of catalysts for catalytic combustion of ammonia and oxygen to nitrogen oxides, consisting of menheere one first mesh catalyst is a platinum-rhodium mesh, characterized in that the second and the downstream located mesh catalyst is palladium-rhodium mesh with at least 92 weight. % palladium, 2-4 weight. % of rhodium, and the rest - platinum.

7. Device for the recovery of nitrous oxide, formed during the catalytic combustion of ammonia and oxygen to nitrogen oxides, and use of catalysts for catalytic combustion of ammonia and oxygen to nitrogen oxides, comprising at least one first mesh catalyst and at least one second mesh catalyst, and at least one first mesh catalyst is a platinum-rhodium mesh, characterized in that the second and the downstream located mesh catalyst is palladium-rhodium mesh with 82-83 weight. % palladium, 2.5 to 3.5 weight. % of rhodium, and the rest - platinum.

8. The device according to p. 7, characterized in that palliatieve grid is characterized by the content of rhodium 2.5 to 3 weight. % and the palladium content of 82.5 weight. %

9. Device according to one of paragraphs. 6-8, characterized in that palliatieve mesh placed at a distance from the platinum-rhodium mesh by at least one third of the grid.

10. Device according to one of paragraphs. 6-9, great for the in particular, when the catalytic combustion of ammonia and oxygen to nitrogen oxides, characterized in that it uses the device on one of the PP. 6-10.

 

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