Tube isothermal catalytic reactor

Abstract

Vertical reactor (1) for chemical reactions, comprising a tube heat exchanger (6) immersed in a catalytic bed (5), wherein said tube exchanger (6) comprises a plurality of straight tube bundles (6.1, 6.2) with respective tube plates for feeding (9.1, 9.2) and collecting (10.1, 10.2) the heat exchange fluid, and wherein the tube bundles and the respective tube plates are vertically staggered so as to allow access to the shell side.

Claims

1. A vertical chemical reactor comprising at least a catalytic bed and a tube heat exchanger immersed in said catalytic bed and fed with a heat exchange fluid, wherein: said tube exchanger comprises a plurality of straight tube bundles, each tube bundle having a respective feed tube plate and a respective collection tube plate for the fluid, wherein said plurality of tube bundles comprises at least a first set of tube bundles arranged at a first height inside the reactor and a second set of tube bundles arranged at a second height inside the reactor, the bundles of the first set and the second set being alternated so that each tube bundle is staggered vertically with respect to the adjacent bundles, wherein said tube plates are shaped as circular sectors or ring sectors and each one of said sectors extend substantially along the full radial extension of said catalytic bed.

2. The reactor according to claim 1, wherein said tube plates have a surface of interface with the tubes, which is flat.

3. The reactor according to claim 1, wherein the free spaces between adjacent tube plates, due to the vertically staggered arrangement, define access points to the reactor zone containing the catalytic bed, which can be used for loading and unloading catalyst.

4. The reactor according to claim 1, wherein the tube plates, viewed in cross-section, cover the entire cross-section of the catalytic bed.

5. The reactor according to claim 1, wherein the tube bundles comprise straight tubes having the same length.

6. The reactor according to claim 1, wherein the catalytic bed has an essentially annular geometry being situated between two vertical and coaxial cylindrical walls, and the bed is crossed by a radial or axial-radial flow, and the tube plates are formed as ring sectors.

7. The reactor according to claim 1, for one of the following uses: methanol synthesis reactor, ammonia synthesis reactor, synthesis gas shift reactor.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows in schematic form a tube reactor according to an embodiment of the invention.

(2) FIG. 2 is a schematic cross-section of the reactor according to FIG. 1.

(3) FIG. 3 shows a planar expansion of the longitudinal section of the heat exchanger of the reactor according to FIG. 1.

DETAILED DESCRIPTION

(4) FIG. 1 shows the main parts of a vertical reactor 1 according to an embodiment of the invention. The reactor 1 comprises: a shell 2; coaxial and perforated cylindrical walls which form an inner collector 3 and an outer collector 4. The space between the two collectors 3 and 4 contains a catalytic bed 5 and a tube heat exchanger denoted overall by the reference number 6. Said heat exchanger 6 is immersed in the bed 5.

(5) The example relates to a centripetal axial-radial or radial flow reactor, in which the reagents, fed via the inlet 30, enter the catalytic bed 5 through the space 8 around the outer collector 4, and the reaction products are collected inside the central tube 7 and exit through the outlet flange 31.

(6) The reactor according to FIG. 1 is therefore of the radial or axial-radial flow type (depending on the direction the bed 5 is passed through) which constitutes a particularly advantageous application; it is however possible to apply the configuration of the invention also to an axial reactor and in this case the reactor does not comprise the collectors 3 and 4.

(7) The heat exchanger 6 is fed with a heat exchange fluid, entering at 20 and exiting at 21, which controls the temperature of the catalytic bed 5. For example, reference is made to an exothermal reactor wherein the heat exchanger 6 exports heat from the bed, and the fluid is water which is fed to the bottom and which evaporates along the tubes, emerging in the form of steam from the top of the bundle. Due to this operating mode, such a reactor is also called steam raising reactor.

(8) The heat exchanger 6 comprises a plurality of tube bundles, with respective tube plates, which are vertically staggered as can be noted from the figures. The figures show a first bundle 6.1 with tube plates 9.1 and 10.1 and a second bundle 6.2 with tube plates 9.2 and 10.2. The bundle 6.1 is located at a first height inside the reactor 1, while the bundle 6.2 is located at a second height; consequently, the bundles and the tube plates are staggered by a distance s (FIG. 3) defining spaces 11 and 11 between adjacent plates.

(9) As can be noted in particular in FIG. 3, there are alternated bundles which are situated at a first height (such as the bundle 6.1) and at a second height (such as the bundle 6.2). It should also be noted that the surface 12 of the plates is advantageously flat. In this way, the ends of the straight tubes may be easily welded to the plates.

(10) The tube bundles communicate with a common feed distributor 13 (water inlet) and with a common steam collector 14 (steam outlet). Each plate communicates with the distributor 13 or the collector 14, preferably via a duct 15 and a cover 16.

(11) A preferred embodiment of the tube plates 9.1 and 9.2 is illustrated in FIG. 2, wherein said tube plates are shaped as ring sectors. A single tube plate, for example the plate 9.1, occupies a sector of the ring defined between the walls 3 and 4, substantially corresponding with the cross-section of the catalytic bed 5.

(12) From FIG. 2 it can be noted that the tube plates cover the entire cross-section of the catalytic bed 5 and consequently, even though ordinary straight tubes are used, it is possible to distribute the tubes within the catalytic bed in a substantially uniform manner. Also, each sector of plate has substantially the same radial extension as the catalytic bed going from the inner collector 3 to the outer collector 4.

(13) This results in better use of the reactor volume and improved and more uniform control of the process, in particular of the reactor temperature. Nevertheless, the shell side (i.e. the space containing the catalyst) is accessible via the passages 11 and 11, which are not visible in FIG. 2, but which allow the catalyst to be easily loaded and unloaded. The passages 11 in the top part of the reactor allow the loading of the catalyst, while the passages 11 in the bottom part are intended for unloading.

(14) The fluid collection plates 10.1 and 10.2 are shaped and arranged in a similar manner and as shown by way of example in FIG. 2.

(15) The invention therefore achieves the objects described above.