MEASUREMENT APPARATUS FOR MEASURING AXIAL TEMPERATURE PROFILES IN A REACTOR TUBE

Abstract

Described herein are a measurement apparatus for measuring axial temperature profiles in a reactor tube, a connecting piece for connecting the reactor tube to a feed pipe configured as a thermal stress compensator for a reaction input stream and for lateral introduction of a multipoint thermocouple into the reactor tube, the use of the connecting piece/measurement apparatus for measuring axial temperature profiles in a reformer tube for steam reforming of hydrocarbons and a process for installing the measurement apparatus.

Claims

1. A connecting piece for connecting a reactor tube to a feed pipe configured as a thermal stress compensator for a reactor input stream and for lateral introduction of a multipoint thermocouple into the reactor tube, comprising: (a) a first cylindrical or frustoconical section having a first end pointing towards a circular entry end of the reactor tube, wherein the first end of the connecting piece has the same internal diameter as the entry end of the reactor tube or as a tubular insulation piece introduced into the entry end of the reaction tube and wherein the first section of the connecting piece is gastightly connectable to the entry end of the reactor tube, (b) a second cylindrical or frustoconical section having a second end pointing towards a circular exit end of the feed pipe, wherein the second end of the connecting piece has the same internal diameter as the exit end of the feed pipe and is gastightly connectable thereto, (c) at least one transition piece gastightly connectable to the first and the second section of the connecting piece, (d) wherein the constituents (a), (b) and (c) have a circular cross section and a longitudinal axis through the respective circle center point, wherein the constituents are arranged one behind the other with their longitudinal axes in alignment and thus coincide on a common longitudinal axis, (e) a guide tube laterally attached to one of the constituents (a), (b) and (c), gastightly connected to the constituent and opening into the constituent and provided at the end pointing away from the constituent with a securing means which permits feedthrough and gastight securing of a multipoint thermocouple, (f) wherein the angle between the common longitudinal axis and the longitudinal axis of the guide tube is between 15° and 60 and the angle points in the direction of the feed pipe.

2. The connecting piece according to claim 1, characterized in that first section, the second section, the at least one transition piece and the guide tube or combinations of these elements are single-piece or multi-piece but gastightly connectable so that all elements in the connected state are in fluid connection with one another.

3. The connecting piece according to claim 1, wherein in the connected state the common longitudinal axis of the connecting piece coincides with the center point of the entry end of the reactor tube and with the center point of the exit end of the feed pipe.

4. The connecting piece according to claim 1, wherein the first and/or the second section of the connecting piece comprise a flange which is gastightly connectable with flange counterparts at the entry end of the reactor tube and/or at the exit end of the feed pipe.

5. The connecting piece according to claim 1, wherein the end of the guide tube pointing away from the connecting piece comprises an outer screw thread, and a pipe screw connection, crush fitting, compression fitting or cutting ring fitting serves as securing means.

6. A measurement apparatus for measuring axial temperature profiles in a reactor tube, comprising: (a) a connecting piece according to claim 1, (b) a multipoint thermocouple, (c) at least once centering body for centering the multipoint thermocouple in the reactor tube, wherein the centering body comprises: (c1) an inner ring which permits feedthrough of the multipoint thermocouple, (c2) a multiplicity of spacers which in respect of the inner ring are arranged radially and at equal distances along the outside of the inner ring, wherein the spacers have the same length and the length is chosen such that the circle center point of the inner ring coincides with the longitudinal axis of the reactor tube when the centering body is introduced into the reactor tube and the plane formed by the spacers is arranged perpendicularly to the longitudinal axis of the reactor tube.

7. The measurement apparatus according to claim 6 for measuring axial temperature profiles in a reactor tube filled with a dumped bed of a solid, particulate catalyst, wherein the average distance between two adjacent spacers is greater than the average length of the catalyst particles.

8. A process for installing the measurement apparatus according to claim 6 in a reactor tube for performing endothermic or exothermic heterogeneously catalyzed chemical reactions comprising: (a) providing the reactor tube, the measurement apparatus, the feed pipe for the reactor input stream and a solid, particulate catalyst as bulk solid, (b) passing the multipoint thermocouple through the feed pipe and through the inner rings of at least two centering bodies, (c) introducing the multipoint thermocouple with the centering bodies into the interior of the reactor tube through the entry end thereof, (d) charging the solid, particulate catalyst into the interior of the reactor tube through through the entry end thereof up to a specified fill height, (e) gastightly connecting the connecting piece to the entry end of the reactor tube, (f) gastightly connecting the connecting piece to the exit end of the feed pipe, (g) gastightly securing the multipoint thermocouple in the guide tube with the securing means.

9. The process for installing the measurement apparatus according to claim 8, wherein (a) the charging of the solid, particulate catalyst is carried out up to the lower edge of the lowest centering body, (b) the lowest centering body is raised by a specified length along the longitudinal axis of the reactor tube, (c) the steps (a) and (b) are repeated until the specified fill height has been achieved, (d) the at least one centering body is removed before the connecting of the connecting piece to the reactor tube.

10. The process for installing the measurement apparatus according to claim 8, wherein the gastight connecting of the connecting piece with the entry end of the reactor tube and/or the gastight connecting of the connecting piece with the exit end of the feed pipe is carried out using flange connections and/or weld connections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Developments, advantages and possible applications of the invention are also apparent from the following description of working and numerical examples and the drawings. All features described and/or depicted form, either in themselves or in any combination, the invention, regardless of the way they are combined in the claims or the back-references therein.

[0057] FIG. 1 shows an example of a reactor tube for catalytic steam reforming of hydrocarbons having a measurement apparatus for measuring axial temperature profiles according to the prior art (for example US 2016/0263542 A1),

[0058] FIG. 2 shows an example of a connecting piece according to the invention for connecting a reactor tube for the catalytic steam reforming of hydrocarbons to a feed pipe configured as a thermal stress compensator for a reactor input stream and for lateral introduction of a multipoint thermocouple into the reactor tube,

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0059] FIG. 1 is an exemplary and schematic diagram of a reactor tube 1 for catalytic steam reforming of hydrocarbons having a measurement apparatus for measuring axial temperature profiles in the reactor tube according to the prior art (for example US 2016/0263542 A1). The arrangement shown comprises a reactor tube 10 having an entry-side flange 12 which is sealed using a flange-connected cap 14. The reactor tube is filled with a dumped bed 16 of a particulate catalyst for steam reforming of hydrocarbons. The hydrocarbons to be reacted, for example methane, butane or naphtha, are mixed with steam to afford a gaseous input mixture and after heating in a heating apparatus (not shown) introduced into the reactor tube 10 using a feed pipe 18. The flow conditions in the gaseous input mixture are indicated by means of flow arrows. It is apparent therefrom that after entering into the entry end of the reactor tube a proportion of the gaseous input mixture initially moves counter to the main flow direction on account of eddy formation since in the region of the internal volume of the reactor tube between the entry side flange and the feed pipe a low-flow dead zone is formed in which the comparatively high residence time of the hot hydrocarbon-steam mixture results in undesired coke formation.

[0060] The axial temperature profile inside the catalyst dumped bed is measured using a multipoint thermocouple 20 which may be introduced into the interior of the reactor tube via a bore in the cap. Using a compression fitting 22 the multipoint thermocouple may be secured to the cap 14 gastightly with respect to the environment so that undesired escape of input gas or product gas from the reactor tube under elevated pressure is avoided. To this end the bore in the cap 14 may be provided for example with an inner screw thread (not shown) which may be connected to a corresponding outer screw thread on the compression fitting.

[0061] A plurality of centering bodies 24 which are permeable to the gaseous input mixture and—during charging the reactor tube with catalyst—to individual catalyst particles are used to secure the multipoint thermocouple in the tube center of the reactor tube.

[0062] In the case of operating the reactor tube 10 for steam reforming of hydrocarbons the described arrangement of the multipoint thermocouple has disadvantages. In the course of operation the high reactor temperatures occurring during steam reforming result in a considerable lengthening of the reformer tube relative to ambient conditions. In order to reduce the associated thermal stresses the feed pipe is for example connected with thermal stress compensators (not shown); alternatively the feed pipe may also be configured as a thermal stress compensator. The lateral arrangement of the inlet pipe means there are nevertheless thermal stresses acting on the already highly thermally stressed reactor tube which act perpendicularly to its longitudinal axis and can therefore result in deformation thereof. Furthermore, the deflection of the gas flow direction of the input gas by angles up to 90° from the inlet pipe into the reactor tube is unfavorable since this can result in the formation of zones of relatively high temperature in which increased cracking of the introduced hydrocarbons and thus local coke deposition occurs. For example the region of the reactor tube above the connection point of the inlet pipe forms a low-flow zone (dead zone) which is at particular risk of local overheating and thus undesired local coke formation.

[0063] FIG. 2 therefore shows a connecting piece 30 according to the invention which overcomes the recited problems and makes it possible to connect a reactor tube 10 to a feed pipe 34 configured as a thermal stress compensator for a reactor input stream and for lateral introduction of a multipoint thermocouple into the reactor tube. The connecting piece 30 comprises the following constituents:

[0064] (a) a first section 32 having a, for example cylindrical, first end which points towards the entry end of the reactor tube 10 and which has the same internal diameter as the entry end of the reactor tube and is gastightly connectable thereto. In the example shown the gastight connection is effected using a flange 33 which is connectable to the reactor tube 10 with a flange counterpart 12. This is indicated by dashed lines in FIG. 2.

[0065] (b) a second section 34 having a, for example cylindrical, second end which points towards the exit end of the reactor tube 35 (shown with dashed lines) and which has the same internal diameter as the exit end of the feed pipe 35 and is gastightly connectable thereto. The connection may be produced using a flange provided therefor as indicated in FIG. 2. An alternative connection possibility is that of producing a weld connection.

[0066] (c) a transition piece 36 whose first end has the internal diameter of the entry end of the reactor tube 10/the first section 32 and whose second, opposite end has the internal diameter of the exit end of the feed pipe 35/the second section 34.

[0067] (d) The constituents (a), (b) and (c) preferably have a circular cross section and a longitudinal axis through the respective circle center point, wherein the constituents are arranged one behind the other with their longitudinal axes in alignment and thus coincide on a common longitudinal axis 40.

[0068] (e) The first section 32 has a guide tube 38 attached to it which is gastightly connected to the first section of the connecting piece and opens into the first section 32. The gastight connection between the guide tube and the first section is preferably realized using a weld connection and in an alternative example using a flange connection. The guide tube 38 is provided at its end pointing away from the first section with a securing means 22, for example a pipe screw connection, crush fitting, compression fitting or cutting ring fitting, wherein the securing means permits feedthrough and gastight securing of a multipoint thermocouple (not shown in FIG. 2).

[0069] (f) The angle α between the common longitudinal axis 40 and the longitudinal axis of the guide tube 42 is between 15° and 60°, preferably between 20° and 45°, wherein the angle points in the direction of the feed pipe. In other words the angle points away from the reactor tube. In the example shown in FIG. 2 the angle α is 45°. Investigations have shown that the recited angles make it possible using the guide tube to introduce a multipoint thermocouple via the entry end of the reactor tube into the interior thereof without the force required therefor becoming excessive and without excessive deformation being exerted on the multipoint thermocouple. The bend radius of multipoint thermocouples is more limited compared to individual thermocouples since for each temperature measurement point a corresponding thermocouple must be provided and in one example all thermocouples are embedded together with their supply leads in a common shell tube, which, while flexible, has limited flexibility due to the greater thickness of the arrangement compared to individual thermocouples.

[0070] In one example of a reactor tube 1 for catalytic steam reforming of hydrocarbons with a measurement apparatus 20 for measuring axial temperature profiles, wherein the installation of the measurement apparatus 20 between the reactor tube 10 and the feed pipe 18 for the input gas containing hydrocarbons and steam is effected using the connecting piece 30 according to the invention. The lateral introduction of the measurement apparatus 20 (multipoint thermocouple) via the guide tube 38 and the centering of the measurement apparatus using the centering body 24 is indicated. It should be noted that this configuration allows introduction of the input gas without dead zones. This reduces the extent of undesired coke deposition in the inlet region of the reactor tube.

[0071] In another example of a reactor tube 10 which is configured similarly to the example described above, wherein in a departure therefrom the entry end of the reactor tube is provided with a tubular insulating piece. Accordingly the first section of the connecting piece is configured at its first end pointing towards the entry end of the reactor tube with a narrowing, for example with a frustoconical narrowing, so that the first end of the connecting piece has the same internal diameter as the tubular insulating piece. The configuration of the end of the first section of the connecting piece pointing towards the entry end of the reactor tube with a frustoconical narrowing has the further advantage that it facilitates introduction of the multipoint thermocouple during installation; the frustoconical narrowing acts as a kind of guide element for the thermocouple.

LIST OF REFERENCE SYMBOLS

[0072] [1] Reformer tube [0073] [10] Reactor tube [0074] [12] Flange [0075] [14] Cap [0076] [16] Catalyst dumped bed [0077] [18] Feed pipe [0078] [20] Measurement apparatus (multipoint thermocouple) [0079] [22] Securing means (for example compression fitting) [0080] [30] Connecting piece [0081] [32] First section [0082] [33] Flange [0083] [34] Second section [0084] [35] Feed pipe [0085] [36] Transition piece [0086] [38] Guide tube [0087] [40] Common longitudinal axis of 32, 34, 36 [0088] [42] Longitudinal axis of guide tube

[0089] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.