EP0903184A2 - Injector and its application for spraying catalyst beds - Google Patents

Abstract

A jet injector finely distributes solid or liquid particles over a large area e.g. the use of silver with promoter as a catalytic material in the manufacture of formaldehyde. The injector has two or more single injectors secured to a base (5, 7) and a double mantled pipe (1, 2). The base (5, 7) is joined to and sealed with the double mantled pipe (1, 2) and has link apertures (70) between the inner space within the pipe (1) and the injector (8, 9, 10, 11) inner guide (11). It also has link passages (52) linking the zone between the double mantle pipe inner pipe (1) and the outer pipe (2), and an outer guide (8, 9) surrounding the inner guide (11). The base (5, 7) and individual injectors (8, 9, 10, 11) produce a mixture of carrier gas and aerosol charge of droplets or solids passing between the inner (1) and outer (2) pipes (1), and a uniform radial expansion of the mixture.

Description

The invention relates to injectors and in particular to two-substance injectors. In addition, the invention relates to the use such injectors for spraying catalyst beds.

There are numerous publications in the prior art that deal with atomizing liquids. In particular, there are two-component nozzles described with an inner mixture and two-component nozzles with an outer mixture and examined theoretically and experimentally. In the article "Calculated Spray - Methods of atomizing liquids in process engineering " by Thomas Richter and Stefan Wilhelm (Maschinenmarkt 1991, p. 26ff.) Such atomizing nozzles are described.

DE-OS 195 26 404 describes a device for dividing a first one Medium described using a second medium. It will a very low ratio of the exit areas of the respective openings for the second medium to those of the openings for the exit of the first medium described.

• der Injektor erfordert wenig Platz am Einbauort,
• der Injektor kann hohen Temperaturen standhalten,
• der Injektor bewirkt eine gleichmäßige, flächendeckende Aufteilung von Kleinen Mengen von Feststoffen auf große Flächen,
• der Injektor ist einfach aufgebaut,
• der Injektor ist störungssicher im Betrieb auch mit Feststoffaerosolen.

In addition, although numerous spray heads for atomizing a wide variety of materials are offered by commercial suppliers in the prior art, a spray head or injector which meets the following requirements in combination has been missing so far.

• the injector takes up little space at the installation site,
• the injector can withstand high temperatures,
• the injector distributes small amounts of solids evenly across large areas,
• the injector is simple,
• the injector is safe to operate even with solid aerosols.

Especially when promoting silver catalysts, such as those used in the Production of formaldehyde to be used resulted in a need for uniform, pulsed doping of the catalyst with the promoter during reactor operation and under the existing flow turbulence in the reactor. There should be local overdose with promoter that can lead to deactivation of the catalyst can be avoided. Conventional nozzles for feeding the promoters do not allow this.

The object of the invention is therefore to provide an injector, which avoids the disadvantages of the prior art and those mentioned above Requirements fulfilled. In particular, this injector is intended for use with the promotion of a silver catalyst with a large catalyst surface is available. In addition, the injector is said to existing lock systems can be integrated into formaldehyde reactors.

The task is achieved by an even distribution of solids or liquids on large areas suitable injector, the least has two individual injectors. According to the invention, the injector contains a Double jacket tube and a base body for single injectors. The double jacket tube has an inner tube, suitable for guiding a mixture of Carrier gas and solid particles or liquid droplets, and an exterior Pipe suitable for carrying a propellant gas. The basic body is with the tightly connected to both pipes of the double jacket pipe. The basic body has connection openings that connect between the interior of the inner tube and one connection point for an inner guide element of a single injector, as well as connecting channels, the one Connection between the area between the inner tube and the outer tube of the double jacket tube and one connection point for each the inner guide element surrounding the outer guide element of a single injector form. The basic body and individual injectors are designed in this way and arranged that a mixture supplied through the inner tube Carrier gas and solid particles or liquid droplets and one through the Area fed between the inner tube and the outer tube Propellant gas to swirl propellant gas, carrier gas and solid particles or liquid droplets and to a radial even spread of the mixture formed.

Surprisingly, it was found that by means of injectors with nozzles that are fed by a propellant gas and a distribution gas at the same time, a fine distribution of a solid promoter can be achieved, the one local overdosing on the catalyst practically excludes. In advantageous In addition, the nozzles and the injector are simple constructed, reliable in use and constructed so that the Injector can be adapted to existing flow conditions. Of the Injector can in particular in an existing lock system of a formaldehyde reactor to get integrated.

In one embodiment of the invention is between the base body and Double-walled pipe, a connection element is present, the connection element ring-shaped holes for transport and even distribution of the propellant gas, which are dimensioned so that the Pressure loss when flowing through is many times lower than with Inflow into the pressure chamber of the single injector.

An annular distributor space can advantageously be present in the base body be the one with the area between the inner tube and the outer tube of the double jacket tube is connected. From this lead Connection channels to a connection point for an outer guide element of a single injector.

Preferably three to eight individual injectors are in a regular Polygon arranged connected to the base body.

Good results are achieved with injectors according to the invention in which the individual injectors are designed as two-component ring nozzle injectors.

It may be appropriate for the outer guide element of the individual injectors is designed and arranged so that the propellant gas in contact with the mixture of carrier gas and solid particles or liquid droplets a tangential flow component related to the axis of the concerned Has single injector.

The fact that the individual injectors in groups on several, in particular two, injector levels can be connected to the base body particularly suitable distributions of the material can be effected.

The injector according to the invention can be designed so that the central one Spray direction of the individual injectors only one radial and one axial component referred to the axis of the double jacket tube.

If a centrifugal distribution component is desired, the central spray direction of the individual injectors a tangential component related to the axis of the double jacket tube.

The invention further relates to the use of an inventive Injector for supplying a suspension to a catalyst bed, in particular one with a large surface. For example, this catalyst bed linear minimum dimensions of 0.5-3 m, preferably essentially have a circular shape. The one according to the invention is particularly suitable Injector for feeding promoter material, in particular Phosphor promoter material, on a catalyst bed, in particular a silver catalyst bed, as it is used in particular in a formaldehyde reactor finds.

With the injector according to the invention, small amounts of solids, in particular 0.1-10 g / m ² , preferably 0.1-5 g / m ² , can be uniformly distributed over large areas.

Fig. 1 einen Querschnitt durch einen erfindungsgemäßen Injektor und

Fig. 2 eine Draufsicht auf einen erfindungsgemäßen Injektor

zeigt.Further details, features and advantages of the invention will become apparent from the following description and the drawing, in which

Fig. 1 shows a cross section through an injector according to the invention and

Fig. 2 is a plan view of an injector according to the invention

shows.

1 shows a preferred injector according to the invention. This has a modular structure. The modules product feed, basic body and ring nozzle injector their design and effectiveness can easily be changed. The individual elements are by plug and / or screw connections easily exchangeable. The injector according to the invention has a double jacket tube 1, 2 consisting of an inner tube 1 and an outer tube 2 consists. The double jacket tube is via an intermediate piece 3, which is preferably three to twelve, in the illustrated case eight connecting holes 4, which run in the axial direction with respect to the double jacket tube, connected to a base body 5. In this basic body is a annular distribution space 51 is provided, from which connecting channels, in the form of bores 52, to propellant gas annular spaces 10 of individual injectors 8,9,10,11 lead.

Connection openings lead through an inner section of the base body, in the form of bores 70, radially outwards and axially downwards. The Bores 70 connect the inside of the inner tube with spray nozzles 11 of the individual injectors 8,9,10,11. The spray nozzles (inner guide elements) 11 are surrounded by outer guide cylinders 8.9. These cylinders (outer guide elements) can for example be screwed into the base body 5 be.

The individual injectors, six of which are shown in FIG. 2, can be designed so that with respect to the central spray direction or the axis of the Single injectors generated a tangential component of the propellant gas flow becomes. This can preferably be done by the design of the outer guide cylinder 8.9, e.g. of their walls. The individual injectors themselves can moreover be arranged so that they are a tangential exit component related to the axis of the double jacket tube.

In operation, an aerosol stream, preferably finely divided solid material, in a carrier gas through the inner tube 1 and the holes 70 fed to the spray nozzles 11 of the individual injectors. At the same time the Propellant gas flow over the ring area between the inner tube 1 and the outer tube 2 through the holes 4, the manifold 51, the holes 52 and the feed chambers 10 of the individual injectors are fed so that there is a strong swirling and mixing inside the individual injectors of the aerosol flow and the propellant gas flow.

Typical operating conditions for the propellant gas flow, which preferably consists of Air there are pressures of 0.5 to 5 bar, while the aerosol, i.e. the Particles or droplets in an inert gas or compressed air, preferably with a pressure of 0.2 to 3.0 bar to the nozzle head or injector head becomes. This operation of the injector is very smooth Distribution of solid material, in particular phosphorus doping material, reached via, for example, a catalyst bed. Merging the Aerosols and the propellant lead to optimal atomization and Distribution.

In the following the invention and preferred individual features thereof explained using examples.

Example 1 (comparative example ):

A three-layer silver catalyst bed was placed in a production reactor applied with a total layer thickness of 2 cm. The bottom layer consisted of silver crystals with a grain size of 1 to 2.5 mm, the middle one Silver crystals with a grain size of 0.75 to 1 mm, the upper layer made of silver crystals grain size 0.2 to 0.75 mm.

A gas mixture consisting of methane, water and air was passed through an initial fixed bed of silver catalyst which had been heated to 340 ° C. The amount was increased during the 2-hour activation period to 4.5 tons of methanol, 3.1 tons of water and 7.8 tons of air per hour (final load). At the end of the activation period, the temperature in the fixed bed was 680 ° C. This flow rate was kept constant over the entire duration of the experiment. 180 mg of phosphorus per m ^{2 of} the cross-sectional area of the activated silver catalyst fixed bed in the form of powdered Na ₄ P ₂ O _{7 were then} sprayed on using a conventional injector, the supply of the gas mixture being continued. The reactor was operated continuously and after several hours of waiting more amounts of phosphorus were applied to the phosphorus-doped silver catalyst fixed bed.

After the fifth post-injection of phosphorus, the catalyst bed was deactivated partial, which inter alia in the increasing methanol content in the end product and low process yield.

The result of this example is summarized below:

Result 1 :

Before the last jetting: Sales: 97.3% Selectivity: 92.6% Yield: 90.1% Residual methanol in the product: 3.2% (based on 100% formaldehyde)

After the last spraying: Sales: 93.0% Selectivity: 90.6% Yield: 84.2% Residual methanol in the product: 8.9% (based on 100% formaldehyde)

The deactivation of the catalyst was visual via camera monitoring visible through a dark spot on the catalyst surface.

Example 2 :

Example 1 was repeated, but the phosphorus feed was stopped with a Injector performed according to the present invention. The reactor was continued to operate, and after several hours of waiting additional amounts of phosphorus on the phosphorus-doped silver catalyst fixed bed upset. In total, phosphorus became 112 times within 49 days post-sprayed without the catalyst bed being deactivated.

Result :

On the 31st day after starting the spraying, after the 44th spraying process: Sales: 97.3% Selectivity: 92.7% Yield: 90.2% Residual methanol in the product: 3.2% (based on 100% formaldehyde)

On the 36th day after starting the spraying, after the 56th spraying process: Sales: 97.2% Selectivity: 92.9% Yield: 90.3% Residual methanol in the product: 3.3% (based on 100% formaldehyde)

Example 3 :

Example 1 was repeated, but 180 mg of phosphorus per m ^{2 of} the activated silver catalyst fixed bed in the form of a 2.0% strength by weight aqueous solution of Na ₄ P ₂ O _{7 were} sprayed onto the surface thereof using the injector according to the invention, with the supply the gas mixture was continued.

In total, phosphorus was injected 67 times within 35 days, without that the catalyst was deactivated.

Result :

On the 11th day after starting the spraying, after the 18th spraying process: Sales: 96.7% Selectivity: 93.2% Yield: 90.1% Residual methanol in the product: 3.9%

Example 4 (comparative example ):

Example 1 was repeated, but 270 mg of phosphorus per m ^{2 of} the cross-sectional area of the activated silver catalyst fixed bed in the form of a 0.3% strength by weight aqueous solution of Na ₄ P ₂ O _{7 were} sprayed onto the surface thereof using a conventional injector, wherein the supply of the gas mixture was continued.

In total, phosphorus was injected 16 times within 30 days, only limited sales were achieved after the 10th post-nozzle. The sales impact could be reduced by lowering the reactor throughput to be corrected again, but occurred with every subsequent post-jet until the correction was no longer possible after the 16th time. This negative result with the conventional injector is summarized below:

Result 4 :

Before the last jetting: Sales: 97.0% Selectivity: 92.4% Yield: 89.5% Residual methanol in the product: 3.6% (based on 100% formaldehyde)

After the last spraying: Sales: 71.2% Selectivity: 93.3% Yield: 66.5% Residual methanol in the product: 46.2% (based on 100% formaldehyde)

Claims (10)

Injector suitable for uniform distribution of solids or liquids over large areas, comprising at least two individual injectors,
marked by a) a double-jacket tube (1,2) with an inner tube (1), suitable for guiding a mixture of carrier gas and solid particles or liquid droplets, and an outer tube (2), suitable for guiding a propellant gas, and b) having a base body (5, 7) tightly connected to the two tubes (1, 2) of the double jacket tube, having aa) connection openings (70) which form a connection between the interior of the inner tube (1) and in each case a connection point for an inner guide element (11) of a single injector (8, 9, 10, 11), and bb) connecting channels (52) which provide a connection between the area between the inner tube (1) and the outer tube (2) of the double-jacket tube and in each case a connection point for an outer guide element (8,9) surrounding the inner guide element (11) of a single injector ( 8,9,10,11), wherein the base body (5, 7) and individual injectors (8, 9, 10, 11) are designed and arranged such that a mixture of carrier gas and solid particles or liquid droplets fed through the inner tube (1) and one through the region between the inner tube (1) and the outer tube (2) supplied propellant lead to a swirling of propellant gas, carrier gas and solid particles or liquid droplets and to a radial, uniform spreading of the mixture formed. Injector according to claim 1, characterized in that between Base body (5,7) and double jacket tube (1,2) a connection element (3) is present, the connecting element arranged in a ring Bores (4) for the transport and uniform distribution of the propellant gas has, which are dimensioned so that the pressure loss when Flow is many times less than when flowing in the pressure space of the single injector (8,9,10,11). Injector according to claim 1 or 2, characterized in that in the Base body (5, 7) there is an annular distributor space (51), with the area between the inner tube (1) and the outer Tube (2) of the double-walled tube is connected and from which the connecting channels (52) to a connection point for an outer guide element (8,9) of a single injector (8,9,10,11). Injector according to one of claims 1 to 3, characterized in that that three to eight individual injectors (8,9,10,11) in a regular Polygon arranged with the base body (5,7) are connected. Injector according to one of claims 1 to 4, characterized in that the single injectors (8,9,10,11) as two-component ring nozzle injectors are trained. Injector according to one of claims 1 to 5, characterized in that the outer guide element (8,9) of the individual injectors is designed in this way and is arranged that the propellant gas in contact with the mixture a carrier gas and solid particles or liquid droplets tangential flow component related to the axis of the concerned Single injector (8, 9, 10, 11). Injector according to one of claims 1 to 6, characterized in that that the individual injectors (8,9,10,11) in groups on several, in particular two injector levels connected to the base body (5,7) are. Injector according to one of claims 1 to 7, characterized in that that the central spray direction of the individual injectors (8, 9, 10, 11) one tangential component related to the axis of the double jacket tube (1, 2). Use of the injector according to one of claims 1 to 8 for Feeding a suspension onto a catalyst bed. Use according to claim 9, characterized in that the injector for feeding promoter material, in particular phosphor promoter material, on a catalyst bed, in particular a silver catalyst bed, in a formaldehyde reactor is used.

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