Method and the device for supporting of the catalytic meshes in the burners for oxygenation of ammonia

FIELD: methods and devices for supporting of the catalytic meshes in the burners for oxygenation of ammonia.

SUBSTANCE: the invention is pertaining to the support system for catalytic meshes in the burners for oxygenation of ammonia and to the method of reduction of movement of the particulates of the ceramic substance caused by the thermal expansion. The support system consists of the catalytic meshes (1) and possibly, of the support sieves (2) which are supported by the ceramic filling agents placed in the burner box with metallic walls and the perforated bottom. The support structure (9) is attached to the metallic wall (4) and-or the outer part of the periphery of the bottom (5). The technical result of the invention is development of the support structure, which does not cause damage of the packet from the catalyzer during operation of the burner, and the development of the system preventing movement of the of the particulates of the ceramic substance.

EFFECT: the invention ensures development of the support structure, which does not cause damage of the packet from the catalyzer during operation of the burner, and the development of the system preventing movement of the of the particulates of the ceramic substance.

12 cl, 2 dwg, 2 tbl

 

In the known burner for the oxidation of ammonia, the mixture of NH3O2and N2interacts at elevated temperature and pressure with the use of a platinum metal catalyst to the formation of nitrogen oxides. Vanished platinum is collected using a capture material. Usually as a catalyst, and catching material include woven or knitted mesh and, consequently, several of these nets in the form of a package that is attached to the burner structure with clamps. Package of catalyst/trap is located in the burner at the pole. The most commonly used types of support include ceramic ring and ring process, placed in a basket attached to the burner structure. As a rule, between the main support and service from the catalyst/trap is the reference mesh woven or knitted base metal, for example, "Megapyr". These known burners are described in Ullmanns Encyclopaedia, volume 20, str-317, 4ethe edition. The use of the catalyst for the splitting of N2O in the burner completely or partially replaces the use of the reference material.

Ceramic ring and applied ceramic catalytic material often during the work shift with the periphery due to thermal expansion. This movement creates a trough, which often causes rupture of the package from the net. The damage of the discussion can be strong, especially around the outer edge of the grid due to low level of support Raschig rings in this place. It was noted that the trough deepens with increasing number of starts and stops installation. This gap poses a problem as due to the lower combustion efficiency and cycle time, and by reason of its dangerous. Leak of ammonia can lead to the formation of nitrite and ammonium nitrate in equipment located further along the process, especially in the condenser for acid. Nitrate and nitrite ammonium can rapidly decompose.

The purpose of this invention to provide an anchor structure which will not cause damage to the package of the catalyst during operation of the burner. Another goal is to develop a system that will prevent or reduce the movement of the particulate ceramic material during operation.

The above and other objectives of the present invention can be achieved by applying the method described below, and a support system. The invention is additionally characterized by the attached patent claims.

The invention is further described with reference to the drawings, in which:

figure 1 shows the formation of a trench in a ceramic filling the basket burner;

figure 2 shows another configuration of the breakwater".

Thus, the present invention relates to a support system to reduce movement of the particulate ceramic Mat is Rial and prevent rupture of the catalytic grids to the burner for the oxidation of ammonia. Catalytic lattice and possibly supporting sieve supported ceramic fillers and used catalytic material contained in the basket burner with metal walls and a perforated bottom. "Breakwater" is preferably attached to the metal wall of the basket burner or, alternatively, to the peripheral portion of the bottom of the trash burner. In this case, the ceramic fillers during expansion will move along the metal walls. Preferably, the breakwater was perforated and filled with ceramic fillers or other similar material to obtain the same hydraulic resistance as the filler layer. "The breakwater" may take the form of a triangular ledge. He can be in the form of a rectangular triangle, thus the wall right angle attached to the metal wall, kind of an equilateral triangle, is attached to the periphery of the bottom. "The breakwater" can also be a smooth or perforated sheet attached to the wall at an angle of 10-60°. The preferred angle is 25-35°. The protrusion of the sheet may consist of segments, the segments may end wall. Can also be used "breakwater" in the form of a honeycomb structure preferably has a sloped top.

Initial tests on a small scale showing the Lee, what an important factor for the formation of the trench is the difference in expansion between the rings process and the metal support due to temperature changes. After only a few cycles of expansion without any support systems in the layer occurs trench, and part of the outer edge is released from the rings. This is consistent with the phenomena observed in burners used. Probably the reason for the formation of the trench is the difference in thermal expansion of metal baskets, burners and ceramic Raschig rings. On large installations, with the diameter of the burner up to 5 m thermal expansion of the metal basket, caused by heating from ambient temperature to operating temperature, up to 30 mm in radius.

Figure 1 illustrates the effect of heat on various levels. Figure 1 shows schematically the equipment before you begin. Burner for the oxidation of ammonia includes a layer of catalyst is usually in the form of several braided or knitted meshes of Pt/Rh wire and, as a rule, catching the layer of getter material, for example an alloy of palladium, in the form of a woven or knitted mesh. All of these grids form the package 1, supported on a steel sieve 2, supported by a layer of rings 3 process, placed in a basket with metal wall 4 and a perforated bottom 5. Ring process can be partially or fully replacements who are ceramic catalyst. Package catalyst package trap and the supporting mesh is attached to the circumference of the burner on the ledge with cargo 6 or similar device. The basket is also attached to the wall of the burner approximately in the same place. Before working layer of Raschig rings line, and around the periphery establish and fix steel sieve and the package of catalytic nets.

When you first power metal wall and a perforated bottom expands more than the ring process. This means that the ring process will not expand to fill the gap after the metal wall will move outward. Such a case is illustrated in figv.

After turning off the installation of the metal wall is cooled and compressed, and ring process on the periphery move inward relative to their initial position. Figs shows a vertical view in section of a known package of catalyst and safety of the grid and its support at the end of the business cycle. Is formed a groove 7, which often causes rupture of the nets. This gap poses a problem as due to the reduced combustion efficiency and reduce the operating cycle, and because of the possible danger.

The movement exposed rings, located close to the periphery. To eliminate this drawback, it was proposed to establish in the reference layer when ructure, also called the "breakwater"to prevent the gutter. Based on the initial experiments was a device for testing, having the same dimensions as one part from the center to the periphery of the middle burner. To simulate thermal expansion install hydraulic device capable of moving one of the short walls. A pilot test may not reproduce extending across the radius of the burner, but he can play the net effect at one end of a branch. The number of extensions of the burner during operation depends on the number of cycles during one working cycle; a specified number varies from 1 to 10.

The first stage involves the re-emergence of the trench formed on the periphery of the layer of Raschig rings during operation. This point is important to conclude whether thermal expansion be considered one of the main reasons. It is carried out to simulate thermal expansion by just moving the movable wall for different values of the extension. Used various length extensions 70, 50 and 30 mm To simulate temperature changes during normal expansion initially operate out of 30 mm (the beginning), and then subsequent movement into and out of the 10 mm.posle only a few cycles of movements of the formed trench, and part of the outer edge is released from the rings. This corresponds to the phenomena observed in working burners. Even at 10 mm repeated expansion/compression pilot pilot unit was able to recreate the formation of the trench.

In the pilot unit has been subjected to various "breakwaters", illustrated in figure 2. The studied samples have a structure of short and long hundred, smooth or perforated sheet at different angles and triangular ledge.

First, as shown in fig.2D, short "cell" is placed loosely in the layer near the moving wall and fill the rings. The result of the expansion of 30 mm is that the support system begins to move in the layer on the inside and outside simultaneously with the emergence of the gutter. After 8 cycles, the entire support system rises above a layer of Raschig rings, with the outer edge is released from the rings. The mobile reference system weld perforated bottom and put it in the layer, as in the previous experiment. The control system moves the layer up a few, but stop before reaching the top of the layer. However, improvement in the education of the gutter is not observed.

Then the cell reference system with a plate welded to the movable wall. The result of this expansion has been the formation of a trench outside "cells", but rings in the chambers of Stalis is fixed. The chute was less than in the previous experiments, however, after 6 cycles the outer edge of the support system in the layer was exposed.

There were also experiments with the structure of the long hundred (figs). It was found that the best results can be obtained in the case when the support structure is welded to the movable wall, and part of the structure is cut, as shown in figa.

In most cases, a support system of short and long hundred out over a layer of Raschig rings. This can lead to rupture of the lattice sharp edges even without the formation of the trench. After cutting the upper part of the cell support in the form of an inclined top 8 performance increases, and the bearing does not come out on top of the layer of Raschig rings. Perhaps such a system with many small branches is more difficult to control, because all offices shall be filled rings. However, if the Department is equipped with perforated bottoms, they can be lifted up completely.

As shown in figa were also conducted experiments with a smooth sheet 9, which is located in a layer under two different angles α 60 and 75°. Sheet are welded to the movable wall, and the sheet are welded wedges 10. Smooth sheet set at an angle of 60°provides the best results, with ongoing education W is LOBA does not occur. Alternatively, it may be a triangle with a right angle, thus the wall right angle attached to the metal wall. The use of an inclined sheet depends on the roughness of the sheet and angle. A decrease in the angle covered is a large area in the burner. In the absence of perforations in the sheet, the cross-sectional area of flow in the burner is reduced, causing a stronger pressure drop and fluid flow through the catalytic grid.

Perforated sheet (hole size 5 mm) is placed in a layer different angles: 60, 45 and 30°. Sheet are welded to the movable wall, and anchor wedges are welded to the sheet. The results are shown in table 1.

td align="center"> 60 0,5
Table 1
αThe magnitude of the expansion, mmThe number of cyclesThe depth of the trench, mmLength*mm
6030115
6030235250
6030550350
60302,5303501
6030330250
30540400
60302,5403502
6030550350
45300,510200
45302,5203003
4530525300
45305,530350
45301030350
453014,535400
45301535400
453024,540400
453034,540400
45303535350
30300
303010
30301,5203004
303020
30302,530300
303050
30305,530300
303010203005
303010,535300
30301525300
303015,535300
30302020300
*the distance from the movable wall to the gutter (if a gutter is formed at a distance from the movable wall).

1) for 250 hours;

2) for 300 hours;

3) the groove formed near a moving wall;

4) trough moved into the layer, about 300 mm;

5) the groove is constant.

Angle constituting 60° a gutter is formed next to the mobile wall (50 mm) for 5 cycles). At the angle of 45° the groove is also formed near the wall, but its size is reduced compared to an angle of 60° (35 mm 35 cycles). When using a sheet with 30° the inclination of the chute is moved approximately 300 mm in the layer, and its depth is also reduced (20 mm 20 cycles).

There were also experiments with triangular ledge 11 (support in the form of a pyramid) of perforated sheets (5° mm). First, it is put in a layer without welding to the movable wall. In this case, there was no significant improvement in the education of the gutter. If such support is not fixed, there is a possibility that the top of the pyramid will pass through the layer and expose sharp edges that can break the bars. If the support is welded to the wall, it follows the movements of the walls, and the groove is not formed on top of a support. This trough has a substantially smaller depth than the groove formed without the use of "breakwater". Installation of the protrusion is triangular in shape, moving together with the outer wall or outer part of the perforated bottom, moves the ring process together with metal. When gutters closer to the center of the basket burner difference in altitude decreases.

Below are the results of experiments with the "breakwater" in the form of pyramids is. Along the outer wall install triangular ledge (in the form of a pyramid). The height of the protrusion is 100 mm, and the angle between the base and the side is 45°. The closest distance of the edge of the ledge on the outer wall is approximately 50 mm, the Protrusion is attached to the outer wall. Height Raschig rings is 130-300 mm

Table 2

The results of the movement of the wall with the "breakwater" in the form of a pyramid
no trialThe height of the rings (mm)The movement of the wall (mm)The depth of trench (mm)Gutter width (mm)
11303035300
21303025300
31303035300
413030/1020300
513030/1030300
613030/1025300
72003520250
820030/1025300
930030/1025350

The resulting trench is a rather flat recess without sharp edges or steep descents.

With regard to the education of the gutter and the burners work, the use of inclined perforated sheets turned out to be the best solution. At the angle of 30° to the horizontal plane of the chute is formed at some distance from the wall, and its depth is significantly reduced compared to the original. In the formation of the trench at a distance from the wall tearing forces acting on the lattice, are reduced. Concentration of forces is avoided due to the weight lattice and too close to her education gutters.

The use of almost all of the tested breakwaters has led to better results than no support. For example, there may be used a metal tape sinusoidal attached to the metal wall. It can be positioned directly beneath a steel sieve.

In working burners expansion occurs along the entire radius. In the pilot tests of the expansion is concentrated on a relatively short distance in the vicinity of the movable wall, however, the test installation recreates the groove similar to the groove that occur during operation. "Breakwaters" asin lip triangular, and inclined sheet was subjected to full-scale production test, confirming the results of the pilot test. When using a flat sheet angle doesn't matter, because the ring process easily slide over such material. However, when using perforated sheets right angle is of great importance.

1. Reference system for catalytic gratings in the burner for the oxidation of ammonia, in which the catalytic lattice (1) and may support sieves supported ceramic fillers (3) and/or catalyst in the basket burner with metal walls (4) and a perforated plate (5), characterized in that the supporting structure (9, 11) attached to the metal wall and/or outer part of the periphery of the bottom under the bars (1).

2. Reference system according to claim 1, characterized in that the structure has a protrusion is triangular in shape (11).

3. Reference system according to claim 1, characterized in that the supporting structure is a smooth or perforated sheet (9), mounted at an angle of 10 to 60° to the wall.

4. Reference system according to claim 3, wherein the specified angle is from 25 to 35°.

5. Reference system according to claim 2, 3 or 4, characterized in that the supporting structure is composed of segments.

6. Reference system according to claim 5, characterized in that the segments have end walls

7. Reference system according to claim 1, characterized in that the supporting structure has the appearance of a honeycomb.

8. Reference system according to claim 7, characterized in that the supporting cell structure has an inclined top (8).

9. Reference system according to any one of claim 2 to 4, 6-8, characterized in that the supporting structure is filled with ceramic fillers/catalyst or similar material to obtain the same hydraulic resistance as the filler layer.

10. Reference system according to claim 5, characterized in that the supporting structure is filled with ceramic fillers/catalyst or similar material to obtain the same hydraulic resistance as the filler layer.

11. The way out of ceramic material and avoid rupture catalytic gratings in the burner for the oxidation of ammonia, in which the catalytic lattice and possibly supporting sieve support ceramic fillers and possibly a catalyst on a perforated plate or sign in the trash burner with metal walls and a perforated bottom, characterized in that the support structure is attached to the metal wall and/or outer part of the periphery of the bottom of the basket burner under the bars so that it moves ceramic material together with a metal wall during expansion.

12. The method according to claim 11, characterized in that the applied therein the supporting structure has the form of a triangular protrusion, smooth or perforated sheet or honeycomb structure.



 

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4 cl, 2 ex, 2 tbl, 2 dwg

FIELD: chemical industry; methods of manufacture of the building structures.

SUBSTANCE: the invention is pertaining to the field of the chemical industry, in particular, to production of the nitric acid, nitric fertilizers, the cyanhydric acid, the nitrites and nitrates and to other productions of chemical products, where the flow sheet of production provides for the catalytic conversion of ammonia up to the nitrogen oxides with usage of the platinoid mesh catalytic agents. The platinoid mesh catalytic agent formed in the form of the catalytic package produced out of the layer-by-layer stacked wire catalytic meshes and weaved out of the wires with the diameter of 0.06-0.1 mm consisting of the alloys of platinum with rhodium, palladium, ruthenium and other metals of the platinum group differs that the catalytic package consists of two different in the geometry of the braiding types of the meshes sequentially alternating in the height of the package. At that the geometry of the braiding of the first type of the catalytic meshes is characterized by the number of the wires interlacing per 1 cm2 in the interval of 1024-450, and the geometry of the braiding of the second type of the catalytic meshes is characterized by the number of the wires interlacing per 1 cm2 in the interval of 400-200. The technical result of the invention is the increased conversion of ammonia and the decreased share of the platinoids included in the mesh catalytic agent production processes providing for the catalytic conversion of ammonia in the flow sheet of the chemical goods production.

EFFECT: the invention ensures the increased conversion of ammonia and the decreased share of the platinoids included in the mesh catalytic agent production processes providing for the catalytic conversion of ammonia in the flow sheet of the chemical goods production.

3 ex

FIELD: inorganic synthesis catalysts.

SUBSTANCE: decomposition if N2O under Ostwald process conditions at 750-1000°C and pressure 0.9-15 bar is conducted on catalyst, which comprises (A) support composed of α-Al2O3, ZrO2, SeO2, or mixture thereof and (B) supported coating composed of rhodium or rhodium oxide, or mixed Pd-Rh catalyst. Apparatus wherein N2O is decomposed under Ostwald process conditions on the above-defined catalyst is also described. Catalyst is disposed successively downstream of catalyst grids in direction of stream of NH3 to be oxidized.

EFFECT: increased catalyst activity.

8 cl, 2 tbl, 3 ex

FIELD: inorganic synthesis catalysts.

SUBSTANCE: invention relates to catalytic elements including ceramic contact of regular honeycomb structure for heterogeneous high-temperature reactions, e.g. ammonia conversion, and can be used in production of nitric acid, hydrocyanic acid, and hydroxylamine sulfate. Described is catalytic element for heterogeneous high-temperature reactions comprising two-step catalytic system consisting of ceramic contact of regular honeycomb structure made in the form of at least one bed constituted by (i) separate prisms with honeycomb canals connected by side faces with gap and (ii) platinoid grids, ratio of diameter of unit honeycomb canal to diameter of wire, from which platinoid grids are made, being below 20.

EFFECT: increased degree of conversion and degree of trapping of platinum, and prolonged lifetime of grids.

5 cl, 6 ex

FIELD: chemistry.

SUBSTANCE: invention pertains to the method of obtaining porous substances on a substrate for catalytic applications, to the method of obtaining porous catalysts for decomposition of N2O and their use in decomposing N2O, oxidising ammonia and reforming methane with water vapour. Description is given of the method of obtaining porous substances on a substrate for catalytic applications, in which one or more soluble precursor(s) metal of the active phase is added to a suspension, consisting of an insoluble phase of a substrate in water or an organic solvent. The suspension undergoes wet grinding so as to reduce the size of the particles of the substrate phase to less than 50 mcm. The additive is added, which promotes treatment before or after grinding. A pore-forming substance is added and the suspension, viscosity of which is maintained at 100-5000 cP, undergoes spray drying, is pressed and undergoes thermal treatment so as to remove the pore-forming substance, and is then baked. Description is also given of the method of obtaining porous catalysts on a substrate for decomposing N2O, in which a soluble cobalt precursor is added to a suspension of cerium oxide and an additive, promoting treatment, in water. The suspension is ground to particle size of less than 10 mcm. A pore-forming substance, viscosity of which is regulated to approximately 1000 cP, is added before the suspension undergoes spray drying with subsequent pressing. The pore-forming substance is removed and the product is baked. Description is given of the use of the substances obtained above as catalysts for decomposition of N2O, oxidation of ammonia and reforming of methane with water vapour.

EFFECT: obtaining catalysts with homogenous distribution of active phases and uniform and regulated porosity for optimisation of characteristics in catalytic applications.

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