Fluid sprinkling – spraying – and diffusing – Combining of separately supplied fluids – At or beyond outlet
Reexamination Certificate
1998-09-21
2001-08-21
Scherbel, David A. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Combining of separately supplied fluids
At or beyond outlet
C239S419000, C239S553000, C239S567000, C239S600000, C422S140000
Reexamination Certificate
active
06276615
ABSTRACT:
The invention relates to injectors and in particular to two-substance injectors. The invention furthermore relates to the use of such injectors for spraying catalyst beds.
In the prior art, there are numerous publications which relate to the atomization of liquids. In particular, two-substance nozzles with internal mixing and two-substance nozzles with external mixing have been described and examined theoretically and by experimentation. The article “Kalkulierter Sprüh—Methoden des Zerstäubens von Flüssigkeiten in der Verfahrenstechnik” [Calculated spray—methods of liquid atomization in process technology] by Thomas Richter and Stefan Wilhelm (Maschinenmarkt 1991, pp. 26 ff.) has described such atomization nozzles.
In DE-A-195 26 404 a device for distributing a first medium using a second medium has been described. The description mentions a very low ratio between the outlet surface areas of the respective orifices for the second medium and those of the orifices for the outlet of the first medium.
Although, furthermore, commercial suppliers in the prior art offer numerous spray heads for atomizing a very wide variety of materials, so far there is no spray head or injector available which fulfills the following combination of requirements:
the injector requires little space at the installation site,
the injector is able to withstand high temperatures,
the injector brings about a uniform, surface-covering distribution of small quantities of solids over large surface areas,
the injector is of simple construction,
the injector is secure against faults during operation even with solid aerosols.
Particularly when promoting silver catalysts, as are used in the production of formaldehyde, there has been a need for a uniform, pulsed doping of the catalyst with the promoter during operation of the reactor and under the turbulent flow conditions present in the reactor. The intention is to avoid local excess metering of promoter, which can lead to deactivation of the catalyst. Conventional nozzles for supplying promoters do not allow this to be achieved.
The object of the invention is therefore to provide an injector which avoids the drawbacks of the prior art and fulfills the abovementioned requirements. In particular, the intention is for this injector to be suitable for use in the promotion of a silver catalyst where there is a large catalyst surface area. Furthermore, it is intended for it to be possible to integrate the injector in existing lock systems in formaldehyde reactors.
The object is achieved by means of an injector which is suitable for uniformly distributing solids or liquids over large surfaces and has at least two individual injectors. According to the invention, the injector contains a double jacketed tube and a base body for individual injectors. The double jacketed tube has an inner tube, which is suitable for guiding a mixture of carrier gas and solid particles or liquid droplets, and an outer tube which is suitable for guiding a propellant gas. The base body is tightly connected to the two tubes of the double jacketed tube. The base body has connecting orifices, which form a connection between the interior of the inner tube and in each case one connection point for an internal guide element of an individual injector, and connecting passages, which form a connection between the region between the inner tube and the outer tube of the double jacketed tube and in each case one connection point for an external guide element, which surrounds the internal guide element, of an individual injector. Base body and individual injectors are designed and arranged in such a way that a mixture of carrier gas and solid particles or liquid droplets which is supplied through the inner tube and a propellant gas which is supplied through the region between the inner tube and the outer tube lead to a turbulent flow of propellant gas, carrier gas and solid particles or liquid droplets and to the mixture formed being distributed radially and uniformly.
Surprisingly, it has been found that injectors with nozzles which are fed simultaneously by a propellant gas and a distribution gas make it possible to distribute a solid promoter finely with virtually no possibility of local excess metering over the catalyst. Advantageously, the nozzles and the injector are furthermore of simple construction, are operationally reliable during use and are designed in such a way that the injector can be adapted to existing conditions of flow. The injector can be integrated in particular in an existing lock system of a formaldehyde reactor.
In one embodiment of the invention, a connection element is present between base body and double jacketed tube, the connection element having bores which are arranged in the form of a ring for conveying and uniformly distributing the propellant gas and which are dimensioned in such a way that the pressure drop when flowing through is lower by a multiple than when flowing into the pressure chamber of the individual injector.
Advantageously, an annular distributor chamber, which is connected to the region between the inner tube and the outer tube of the double jacketed tube, may be present in the base body. Connecting passages lead from this chamber to in each case one connection point for an external guide element of an individual injector.
Preferably, three to eight individual injectors are arranged in a regular polygon and connected to the base body.
Successful results are achieved with injectors according to the invention in which the individual injectors are designed as two-substance annular injectors.
It may be expedient to design and arrange the external guide element of the individual injectors in such a way that the propellant gas, on coming into contact with the mixture of carrier gas and solid particles or liquid droplets, has a flow component which is tangential with respect to the axis of the individual injector in question.
The fact that the individual injectors are connected in groups to a plurality of, in particular two, injector levels on the base body makes it possible to achieve particularly suitable distribution of the material.
The injector according to the invention may be designed in such a way that the central spraying direction of the individual injectors has only a radial and an axial component with respect to the axis of the double jacketed tube.
If a centrifugal distribution component is desired, the central spraying direction of the individual injectors may have a component which is tangential with respect to the axis of the double jacketed tube.
The invention furthermore relates to a method for supplying a suspension to a catalyst bed, in particular one which has a large surface area, wherein an injector according to the invention is used. By way of example, the catalyst bed may have minimum linear dimensions of 0.5-3 m, preferably in essentially circular form. The injector according to the invention is particularly suitable for supplying promoter material, in particular phosphorus promoter material, to a catalyst bed, in particular a silver catalyst bed, as is used in particular in a formaldehyde reactor.
The injector according to the invention can be used to distribute small quantities of solids, in particular 0.1-10 g/m
2
, preferably 0.1-5 g/m
2
, uniformly over large surface areas.
REFERENCES:
patent: 4518120 (1985-05-01), Johnson
patent: 4674682 (1987-06-01), Hansson
patent: 4890793 (1990-01-01), Fuglistaller et al.
patent: 5271562 (1993-12-01), Myers et al.
patent: 6027332 (2000-02-01), Glotin et al.
patent: 195 26 404 (1997-01-01), None
patent: 1460927 (1966-10-01), None
patent: 2 641 365 (1990-07-01), None
Thomas Richter, et al., “Kalkulierter Spruh—Methoden des Zerstaubens von Flussigkeiten in der Verfahrenstechnik,” Maschinenmarkt, Wurzburg 97 (1991) 11, pp. 26-28, 30-31. (with English Abstract).
BASF - Aktiengesellschaft
Ganey Steven J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Scherbel David A.
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