EP1399678B1 - Pump for transporting a heat exchange medium for a multi-tube reactor - Google Patents

Abstract

The invention relates to a pump ( 1 ) having a pump guide tube ( 13 ) for the transport of a heat-exchange medium ( 6 ) for a reactor having a bundle of catalyst tubes ( 2 ), where the pump ( 1 ) has a casing ( 14 ) which surrounds the pump guide tube ( 13 ), having an aperture ( 15 ) in the lower part of the casing ( 14 ) via which the heat-exchange medium ( 6 ) discharged from the lower region of the reactor by means of the pump ( 1 ) flows into the casing ( 14 ), flows upward in the region between the inner wall of the casing ( 14 ) and the outer wall of the pump guide tube ( 13 ), if desired via a heat exchanger ( 18 ), flows into the interior of the pump guide tube ( 13 ) via an aperture ( 16 ) in the upper region of the pump guide tube ( 13 ), flows through the pump guide tube ( 13 ) from top to bottom and flows via an aperture ( 17 ) in the lower region of the pump guide tube ( 13 ) into the reactor, into the upper region of the interspace between the catalyst tubes ( 2 ).

Description

The invention relates to a pump for conveying a heat exchange medium for a contact tube bundle reactor, and to a use of the pump.

The usual type of contact tube bundle reactors consists of a generally cylindrical container in which a bundle, i. a plurality of contact tubes in usually vertical arrangement is housed. These catalyst tubes, which may optionally contain supported catalysts, are sealingly secured with their ends in tube sheets and open into a respectively connected at the top and at the bottom of the container hood. About these hoods the reaction tubes flowing through the reaction mixture is added or removed. A heat exchange fluid circuit is passed through the space surrounding the catalyst tubes to balance the heat balance, especially in reactions of high heat of reaction.

With regard to the heat exchange medium cycle, it is known to realize a substantially homogeneous temperature distribution of the heat exchange medium in each horizontal section of the reactor in order to involve all the catalyst tubes equally in the reaction process (eg DE-B-16 01 162 ). The smoothing of the temperature distribution is the heat supply or heat dissipation via each attached to the reactor ends outer ring lines with a plurality of shell openings, as for example in DE-B-34 09 159 are described.

A further improvement of the heat transfer is achieved by the installation of deflection plates, which leave a passage cross section alternately in the reactor center and at the reactor edge. Such an arrangement is particularly suitable for annularly arranged tube bundles with a free central space and, for example GB-B-31 01 75 known. The deflection pulleys lead to a transverse flow of the catalyst tubes, with the result of an increase in the flow rates and the heat transfer.

In large reactors with a number of contact tubes in the range of about 10,000 to 50,000, in particular from about 15,000 to 33,000, which are additionally equipped with deflection plates, the pressure loss of the heat exchange medium is comparatively very large.

Conveniently, in such reactors, the pumping system is disposed between the upper and lower ring conduits, the heat exchange medium being supplied to the lower portion of the reactor, for example via a loop.

If the molten salt pumped directly into the upper part of the reactor or the upper loop, the required head of 4 to 5 m would require a technically unfavorable and failure-prone pumping system, including because of complex pump shaft seals, longer pump shafts, and greater heat input through the pump shaft in the under engine storage. Furthermore, the above head would require a raised brine equalization tank, which is undesirable for safety reasons. The complete pump pressure would be applied to the shaft seal.

The supply of the heat exchange medium at the upper end of the reactor, ie, in cocurrent with the reaction mixture also fed into the catalyst tubes at the upper end of the reactor, is known to be advantageous for the reaction (cf. DE-A-44 31 449 ).

The DC flow has advantages over the countercurrent flow, such as higher flow rates, lower catalyst hot spot temperatures, desirable increase in the heat exchange medium temperature toward the final reaction in the catalyst tubes, good temperature uniformity of the heat exchange medium across the reactor cross-section, d. H. good horizontal temperature stratification, clear operating conditions over the height of the contact tube space due to lack of feedback through the heat exchange medium.

A DC flow of reaction mixture and heat exchange medium, as in DE-A-44 31 449 described, but encountered with respect to the pumping system to the above difficulties, provided that the heat exchange medium to the upper reactor area, for example, directly via an upper ring line, supplied and discharged from the lower reactor area, for example, directly via a loop.

Out DE 198 367 92 it is known in a contact tube bundle reactor to use the space between the upper and lower ring line for the supply of the heat exchange medium for deflecting the same, wherein the advantage of a DC flow of heat exchange medium and reaction mixture can be connected to the proven pump assembly with supply of the heat exchange medium to the lower loop. For this purpose, it has been proposed to arrange in each case a cylinder jacket-shaped intermediate wall in the upper and in the lower ring line, which separates these in each case into an inner and an outer ring line. The heat transfer medium is supplied to the outer lower ring line, which is connected via a region between the upper and lower ring line to the inner upper ring line, passed from here in a known manner via shell openings in the space surrounding the catalyst tubes, wherein a meandering flow is formed via deflection disks. The heat transfer medium leaves via shell openings the space surrounding the catalyst tubes in the lower part of the reactor and enters the lower inner ring line. This in turn is connected via the area between the upper and lower ring line and with the upper outer ring line.

Out JP / A 59 138 794 is a circulation pump with a deflection of the liquid flow in the pump housing for the purpose of shortening the pump length, the pump weight described. The liquid flow is sucked in the lower area of the pump housing, via nozzles, deflected by baffles, passed down an impeller through an inner guide tube and discharged via a lower opening.

In contrast, it was an object of the invention, a further, in particular manufacturing technology simpler solution to the problem that the heat exchange medium, although with conventional pump assembly, that is with promotion down, is used, yet the entry of the heat exchange medium in the space between the contact tubes of a vertical upright contact tube bundle reactor in the upper region thereof should take place. The above problem should be solved in a simple manner, in particular without changes to the contact tube bundle reactor itself.

The solution is based on a pump with a Pumpenleitrohr for promoting a heat exchange means for a reactor with a bundle of contact tubes with vertically arranged longitudinal axis, with supply of the heat exchange medium in the upper region of the reactor and removal of the heat exchange medium from the lower region of the reactor, preferably above each a ring line.

The invention is characterized in that the pump has a housing which encloses the Pumpenleitrohr, with an opening in the lower part of the housing, via which withdrawn from the lower region of the reactor by means of the pump heat exchange medium flows into the housing, flows in the area between the inner wall of the housing and the outer wall of the Pumpenleitrohrs, optionally via a heat exchanger, upwards, flows through an opening in the upper portion of the Pumpenleitrohrs in the interior of the Pumpenleitrohrs, flows through from top to bottom and over an opening in the lower portion of the Pumpenleitrohrs flows into the reactor, in the upper region of the gap between the catalyst tubes.

The invention is not limited with regard to the configuration of the supply and removal of the heat exchange medium from the reactor. These can preferably take place via a respective ring line. However, other flow guides are also possible, for example via contact tube-free spaces lying opposite one another in the reactor space, as in connection with reactor modules with a rectangular cross section in FIG DE-A 198 57 842 described.

In a preferred embodiment, the heat exchange medium flows through the opening in the lower portion of the Pumpenleitrohrs in a further space between the inner wall of the housing and the outer wall of the Pumpenleitrohrs, flows through this gap from bottom to top and finally flows through an opening in the upper region in the Reactor, in the upper region of the gap between the catalyst tubes.

In a further preferred embodiment variant, the pump is arranged higher, such that it conveys the heat exchange medium directly, preferably via an upper ring line, into a reactor with a bundle of contact tubes into the intermediate space between the contact tubes.

In this embodiment, one or more vent lines from the upper region of the reactor are advantageously provided in the pump. If a plurality of vent lines are provided, they are in particular arranged symmetrically distributed over the circumference of the reactor and brought together before feeding to the pump in a manifold. The vent line (s) can (for example) as a nozzle on the reactor jacket, a short distance below the upper tube sheet or as holes in the tube sheet itself, which lead from the reactor interior to the outside of the reactor, be formed. The vent line (s) is (are) preferably along the outer wall of the pump housing, in particular in the immediate vicinity thereof, led upwards. This embodiment is thermally advantageous because it requires no additional external heating for the heat transfer medium.

The vent line (s) may be configured as needed to open in the pump below or above the liquid level in the same.

According to the invention, a pump is thus provided with a housing, which causes a deflection of the funded by the pump heat exchange medium flow.

The pump according to the invention is preferably a propeller pump, in particular with a propeller with three or more blades.

To promote liquid heat exchange means, often of molten salts, for the supply or removal of the heat of reaction from Kontaktrohrbündekeaktoren Axialförderpumpen, often propeller pumps are used. The propeller pump delivers the desired liquid, in this case a heat exchange medium, for example a salt melt or a heat transfer oil, by means of the propeller, which rotates in the pump guide tube. The propeller preferably has a gap spacing in the range of 2 to 10 mm to the pump guide tube. In this case, a promotion of the liquid in Pumpenleitrohr from top to bottom is required, otherwise otherwise sealing problems occur. The Pumpenleitrohr is usually a propeller enclosing hollow cylinder.

In the present case, a housing is provided around the pump guide tube, which encloses the pump guide tube and which, in conjunction with openings provided in suitable locations in the pump guide tube, is designed such that it effects a deflection of the heat exchange medium flow in the pump.

For this purpose, the housing has in its lower region an opening into which the withdrawn from the reactor heat exchange medium is passed in an area between Pumpenleitrohr and the inner wall of the housing upwards, flows through an opening in the upper region of the Pumpenleitrohrs in the interior of the Pumpenleitrohrs , which, as usual, flows through from top to bottom, leaving it through an opening in its lower part and finally fed back to the reactor in its upper region.

The openings in the Pumpenleitrohr and in the housing do not extend over the entire cross-sectional area of the Pumpenleitrohrs or the housing, but only about 20 to 50%, preferably about about 30% thereof. The reduced area, ie the opening, can be stabilized by suitable bracing. It is also possible to realize the openings in the pump guide tube or in the housing in such a way that the pump guide tube or housing is formed by a perforated plate in the corresponding areas is or has slots.

However, it is also possible, particularly for higher pressure loads, to design the housing with a circular cross-section.

Preferably, guide plates for the heat exchange medium are arranged in one or more deflection regions of the housing.

In a preferred embodiment variant, a guide vane equipped with vanes is arranged below the propeller in order to remove the swirl from the flow. The Nachleitapparat is preferably designed such that its flow cross-section corresponds to the flow-through cross-section in the region of the propeller.

In a preferred embodiment, a pin is provided at the lower end of the pump shaft, which rotates in a bearing. As a result, the propeller can be operated at a greater peripheral speed, the gap width between the propeller and the inner wall of the pump guide tube can be reduced, the pump runs more precisely and is maintenance-free, because the upper bearings are loaded less. The pump can thus handle a larger volume flow and a larger head. If the pump promotes molten salt as heat transfer medium, the heat transfer medium itself acts lubricating for the bearing. The bearing can additionally be reinforced with tungsten carbide steel.

The pump according to the invention is particularly suitable for promoting the heat exchange medium flow for contact tube bundle reactors for carrying out exothermic or endothermic reactions, in particular of oxidation reactions.

The invention will be explained in more detail below with reference to a drawing.

Figur 1

eine bevorzugte Pumpenvariante zur Umlenkung des Wärmetauschmittel- stromes in der Pumpe mit Querschnittsdarstellung in Fig. 1a,

Figur 2

eine weitere bevorzugte Ausführungsvariante zur Umlenkung des Wärme- tauschmittelstromes in der Pumpe, mit Querschnittsdarstellung in Fig. 2a,

Figur 3

eine weitere Ausführungsvariante mit einem Zapfen am unteren Ende der Pumpenwelle, und

Figur 4

eine weitere bevorzugte Alternative mit Anordnung der Pumpe oberhalb des Reaktors und unmittelbarer Förderung des Wärmetauschmittelstromes in die obere Ringleitung des Reaktors.

They show in detail:

FIG. 1

a preferred pump variant for deflecting the Wärmetauschmittel- stream in the pump with a cross-sectional view in Fig. 1a .

FIG. 2

a further preferred embodiment for deflecting the heat exchange medium flow in the pump, with a cross-sectional view in Fig. 2a .

FIG. 3

a further embodiment with a pin at the lower end of the pump shaft, and

FIG. 4

a further preferred alternative with arrangement of the pump above the reactor and direct promotion of the heat exchange medium flow in the upper loop of the reactor.

Fig. 1 shows a pump 1 with deflection of the heat exchange medium 6 in the pump with guide tube 13 with inflow 16 in the upper region or outflow 17 in the lower region thereof, with housing 14 to the guide tube 13 and a housing 14 arranged in the heat exchanger 18. The heat exchanger is only exemplified, it is also possible to form the pump without a heat exchanger. The cross section DD in Fig. 1a illustrates the rectangular cross-sectional configuration of the housing 14. Below the propeller 20, a Nachleitapparat 21 is arranged with blades 22. Guiding plates 19 are preferably arranged in one or more deflection regions for the heat transfer medium 6 in the housing 14.

Fig. 2 shows a further embodiment of a pump 1 for deflecting the heat exchange medium 6 with a cross section EE in Fig. 2a , which deviates from the illustration in Fig. 1 the housing 14, as in the cross-sectional view in Fig. 2a illustrated, is arranged in a circular cross-section around the Pumpenleitrohr 13 around.

Fig. 3 shows a preferred pump variant with a guide pin 23 at the lower end of the pump shaft, which rotates in a bearing 24.

Fig. 4 illustrates a particularly advantageous arrangement of a pump 1 with propeller 20 as well as after nozzle 21 with blades 22, which promotes the heat exchange means 6 directly into the upper ring line 25 of a reactor with a bundle of catalyst tubes 2. Reference numeral 26 denotes the lower ring line, through which the heat exchange medium is withdrawn by the pump 1. In the feed line from the lower ring line 26 to the pump 1, according to the illustrated preferred embodiment, a thermal expansion compensator 28 may be installed and from the upper region of the reactor a vent line 27 leads into the pump, above the liquid level in the same. Also in this arrangement can be arranged in the housing 14 baffles advantageously in the deflection areas for the heat transfer medium.

Claims (9)

1. A pump (1) having a pump guide tube (13) for the transport of a heat-exchange medium (6) for a reactor having a bundle of catalyst tubes (2) with a vertically arranged longitudinal axis, with supply of the heat-exchange medium (6) in the upper region of the reactor into the interspace between the contact tubes (2) and discharge of the heat-exchange medium (6) from the lower region of the reactor, preferably in each case via a ring line (25, 26), wherein the pump (1) has a casing (14) which surrounds the pump guide tube (13), having an aperture (15) in the lower part of the casing (14) via which the heat-exchange medium (6) discharged from the lower region of the reactor by means of the pump (1) flows into the casing (14), flows upward in the region between the inner wall of the casing (14) and the outer wall of the pump guide tube (13), if desired via a heat exchanger (18), flows into the interior of the pump guide tube (13) via an aperture (16) in the upper region of the pump guide tube (13), flows through the pump guide tube (13) from top to bottom, wherein the heat-exchange medium then flows via an aperture (17) in the lower region of the pump guide tube (13) into a further interspace between the inner wall of the casing (14) and the outer wall of the pump guide tube (13), flows through this interspace from bottom to top and flows via an aperture in the upper region of the interspace into the reactor, into the upper region of the interspace between the contact tubes (2).
2. The pump (1) according to claim 1, wherein the pump (1) transports the heat-exchange medium (6) directly into the upper region, into the upper ring line (25) of a reactor having a bundle of catalyst tubes (2).
3. The pump (1) according to claim 1 or 2, wherein the pump is an axial pump, preferably a propeller pump having a propeller (20) having three or more blades.
4. The pump (1) according to any one of claims 1 to 3, wherein the casing (14) is designed with a rectangular cross section.
5. The pump (1) according to any one of claims 1 to 3, wherein the casing (14) is designed with a circular cross section.
6. The pump (1) according to any one of claims 1 to 5, wherein baffle plates (19) for the heat-exchange medium (6) are arranged in one or more deflection regions of the casing (14).
7. The pump (1) according to any one of claims 1 to 6, wherein a diffuser (21) with blades (22) is arranged in the pump guide tube (13) beneath the propeller (20).
8. The pump (1) according to any one of claims 1 to 7, wherein a guide pivot (23) which rotates in a bearing (24) is arranged at the lower end of the pump shaft.
9. The use of a pump (1) according to any one of claims 1 to 8 for the transport of a heat-exchange medium (6) for a reactor having a bundle of catalyst tubes (2) for carrying out exothermic or endothermic reactions, in particular for carrying out oxidation reactions.

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