MULTITUBE REACTOR

Abstract: Multitube reactor suitable for carrying out for catalytic processes, comprising a normally substantially vertically extending vessel, a plurality of open-ended reactor tubes (2) arranged in the vessel parallel to its central longitudinal axis of which the upper ends are fixed to an upper tube plate (5) and in fluid communication with a fluid inlet chamber (8) above the upper tube plate (5) and of which the lower ends are fixed to a lower tube plate and in fluid communication with an effluent collecting chamber below the lower tube plate, liquid supply means (13) for supplying liquid to the fluid inlet chamber (8), gas supply means for supplying gas to the fluid inlet chamber (8), and an effluent outlet arranged in the effluent collecting chamber, wherein the upper end part of each reactor tube is provided with a gas and liquid supply device (25), which device comprises an inlet chamber (26) having a gas inlet opening (27), a liquid inlet (28) and an outlet (30) which is in fluid communication with the upper end part of the reactor tube (2), and a liquid riser (33) extending between a level in the layer (40) of liquid which is during normal operation present in the fluid inlet chamber (8) and the liquid inlet (28) of the inlet chamber (26).

Description: The present invention relates to a multitube reactor suitable for carrying out catalytic processes. An example of such a process is the conversion of synthesis gas into hydrocarbons, especially heavy hydrocarbons. Such a multitube reactor comprises a normally substantially vertically extending vessel, a plurality of open-ended reactor tubes arranged in the vessel parallel to its central longitudinal axis of which the upper ends are fixed to an upper tube plate and in fluid communication with a fluid inlet chamber above the upper tube plate and of which the lower ends are fixed to a lower tube plate and in fluid communication with an effluent collecting chamber below the lower tube plate, liquid supply means for supplying liquid to the fluid inlet chamber, gas supply means for supplying gas to the fluid inlet chamber, and an effluent outlet arranged in the effluent collecting chamber. The upper ends of the reactor tubes are provided with tubes extending through the upper tube plate and/or through the bottom of a horizontal tray arranged above the upper tube plate. During normal operation the reactor tubes are filled with catalyst particles. To convert for example synthesis gas into hydrocarbons, synthesis gas is supplied through the fluid inlet chamber into the upper ends of the reactor tubes and passed through the reactor tubes. Effluents leaving the lower ends of the reactor tubes are collected in the effluent collecting chamber and removed from the effluent collecting chamber through the effluent outlet. To distribute the heat of reaction generated during the conversion uniformly over the reactor tubes, and to improve heat transfer from the interiors of said tubes to the inner walls of the reactor tubes, liquid is introduced into the fluid collecting chamber. The liquid which is collected on the bottom of the horizontal tray flows into the upper ends of the reactor tubes. Liquid leaving the lower ends of the reactor tubes is collected in the effluent collecting chamber and removed from the effluent collecting chamber through the effluent outlet. The heat of reaction is removed by a heat transfer fluid which is passed along the outer surfaces of the reactor tubes. Such a multitube reactor can also be used for the catalytic conversion of a liquid in the presence of a gas. A commercial multitube reactor for such processes suitably will have a diameter of about 5 m and between about 5000 reactor tubes with a diameter of about 45 mm to 15000 reactor tubes with a diameter of about 25 mm. The length of a reactor tube will be about 10 to 15 m. Such a reactor will never be exactly vertical, nor will the upper tube plate be exactly flat. Consequently the distances between a horizontal plane and the upper ends of the reactor tubes will vary. As a result there are reactor tubes which during normal operation do not receive liquid. The heat develloped in these reactor tubes during the reaction will not be adequately distributed and this will causelocal overheating of the catalysts in the reactor tubes. It is an object of the present invention to provide a multitube reactor wherein during normal operation liquid can be substantially uniformly distributed to all reactor tubes, even when the reactor is slightly tilted or the upper tube plate is slightly sagged, and wherein the gas velocities in the reactor tubes are substantially insensitive to the void fractions in the reactor tubes. To this end the multitube reactor suitable for carrying out catalytic processes according to the invention comprises a normally substantially vertically extending vessel, a plurality of open-ended reactor tubes arranged in the vessel parallel to its central longitudinal axis of which the upper ends are fixed to an upper tube plate and in fluid communication with a fluid inlet chamber above the upper tube plate and of which the lower ends are fixed to a lower tube plate and in fluid communication with an effluent collecting chamber below the lower tube plate, liquid supply means for supplying liquid to the fluid inlet chamber, gas supply means for supplying gas to the fluid inlet chamber, and an effluent outlet arranged in the effluent collecting chamber, wherein the upper end part of each reactor tube is provided with a gas and liquid supply device, which device comprises an inlet chamber having a gas inlet opening, a liquid inlet and an outlet which is in fluid communication with the upper end part of the reactor tube, and a liquid riser extending between a level in the layer of liquid which is during normal operation present in the fluid inlet chamber and the liquid inlet of the inlet chamber. It is an advantage of the multitube reactor according to the present invention that the gas and liquid supply device is insensitive to fouling. In addition, liquid can be substantially uniformly distributed to all reactor tubes even when liquid is supplied to the fluid inlet chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes is extremely low. The invention will now be described by way of example in more detail with reference to the drawings, wherein: Figure 1 shows a longitudinal section of a multitube reactor according to the invention; Figure 2 shows detail II of Figure 1 drawn to a scale larger than the scale of Figure 1; Figure 3 shows an alternative of the gas and liquid supply device; Figure 4 shows a further alternative of the gas and liquid supply device; and Figure 5 shows cross-section V-V of Figure 4. Reference is made to Figures 1 and 2. The multitube reactor comprises a normally substantially vertically extending vessel 1 and a plurality of open-ended reactor tubes 2 arranged in the vessel 1 parallel to its central longitudinal axis 3. The upper ends 4 of the reactor tubes 2 are fixed to an upper tube plate 5 which is supported by the inner wall of the vessel 1. In the upper end part of the vessel 1, above the upper tube plate 5, there is a fluid inlet chamber 8 which is in fluid communication with the upper end parts 4 of the reactor tubes. The lower end parts 9 of the reactor tubes 2 are fixed to a lower tube plate 10 supported by the inner wall of the vessel 1. In the lower end part of the vessel 1, below the lower tube plate 10, there is an effluent collecting chamber 11 which is in fluid communication with the lower ends 9 of the reactor tubes 2. The vessel 1 is provided with liquid supply means 13 for supplying liquid to the fluid inlet chamber 8, which liquid supply means 13 comprises a main conduit 14 extending through the wall of the vessel 1 and a plurality of secondary conduits 15 extending perpendicular to the main conduit 14 and being in fluid communication with the main conduit 14. The main conduit 14 and the secondary conduits 15 are provided with outlet openings 16. The vessel 1 is further provided with gas supply means 18 for supplying gas to the fluid inlet chamber 8, in the form of a conduit 19 extending through the wall of the vessel 1 and being provided with slots 20. In the lower part of the vessel 1 there is arranged an effluent outlet 20 communicating with the effluent collecting chamber 11. The upper end part of each reactor tube 2 is provided with a gas and liquid supply device 25 arranged in the fluid inlet chamber 8. The gas and liquid supply device 25 comprises an inlet chamber 26 (see Figure 2) having a gas inlet opening 27, a liquid inlet 28 and an outlet 30 which is in fluid communication with the upper end of the reactor tube 2. The upper ends of reactor tubes 2 do not have fluid communication means other than outlet means 30 of the liquid supply devices 25. The gas and liquid supply device 25 further comprises a liquid riser 33 extending between a level in the layer 40 of liquid which is during normal operation present in the fluid inlet chamber 8 and the liquid inlet 28 of the inlet chamber 26. In the embodiments of the invention as shown in Figures 1 and 2 the liquid riser 33 is the annular space between a cap 41 arranged around the upper part of an extension tube 42 which is in fluid communication with the reactor tube 2, wherein the extension tube 42 is formed by the upper end part of the reactor tube 2. During normal operation, the reactor tubes 2 are filled with catalyst particles (not shown), supported in the reactor tubes 2 by catalyst support means (not shown) arranged in the lower end parts of the reactor tubes 2. To carry out a process for the catalytic conversion of gas in the presence of a liquid, or the catalytic conversion of a liquid in the presence of gas, gas and liquid are supplied to the gas supply means 18 and the liquid supply means 14, respectively. Liquid is collected on the upper tube plate 5 so that a layer 40 of liquid is formed. Gas flows through the gas inlet openings 27 of the inlet chambers 26, and consequently the pressure in the inlet chambers 26 is below the pressure in the fluid inlet chamber 8. As a result liquid is sucked from the layer 40 through the riser 33 to the liquid inlet 28. Gas and liquid pass downwardly through the reactor tubes 2 filled with catalyst particles and the conversion takes place in the reactor tubes 2. The effluents are collected in the effluent collecting chamber 11, and removed therefrom through effluent outlet 20. If the conversion is an exothermic reaction the heat of reaction is removed by a cold fluid supplied to the heat-exchange chamber 50 through inlet 51 and removed therefrom through outlet 52. If the conversion is an endothermic reaction additional heat is supplied by a hot fluid supplied to the heat-exchange chamber 50 through inlet 51 and removed therefrom through outlet 52. In addition, the heat-exchange chamber 50 is provided with baffles 53 to guide the fluid passing theretrough. EXPERIMENTS The following experiments have been carried out using a test rig comprising a fluid distribution chamber closed at its lower end by a tube plate, and between three and five reactor tubes fixed in the tube plate and extending theretrough. The inner diameter of the reactor tubes is 24 mm, their length is 4 m, and the reactor tubes extend 0.2 m above the tube plate. The upper end part of each reactor tube is provided with a gas and liquid supply device in the form of a cap arranged around the upper end part of the reactor tube closed at its upper end by a plate provided with a gas inlet opening, wherein the width of the annulus between the cap and the upper end part of the reactor tube is 5 mm, the distance between the gas inlet opening and the upper end of the reactor tube is 40 mm, and wherein the diameter of the inlet opening is 2.9 mm. The lower ends of the reactor tubes debouche into a separation vessel so as to allow independent determination of the gas and liquid velocities through the reactor tubes. Nitrogen was used to simulate the gas, and decane was used to simulate the liquid. The expression spread of a velocity is used to refer to the ratio of the standard deviation of the velocity over the average velocity times 100%, wherein the standard deviation is the root of the average of the squares of the differences of the velocities from their average. The first experiment was carried out to show that liquid can be substantially uniformly distributed to the reactor tubes when the reactor is tilted or the upper tube plate is sagged. To this end the test rig was provided with three reactor tubes, the upper ends of tubes 1 and 2 extended 200 mm above the tube plate and the upper end of tube 3 extended 212 mm above the tube plate. The reactor tubes were filled with spheres having a diameter of 1.5 mm, and the void fraction in the reactor tubes was 0.36 m³ voids/m³ bed. Decane was supplied to the fluid inlet chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes was 0.51 mm/s. Nitrogen was supplied at such a rate that the pressure in the fluid inlet chamber was maintained at 0.53 bar (gauge). It was found that in tube 1, the liquid velocity was 0.59 mm/s and the gas velocity 30.6 cm/s; that in tube 2, the liquid velocity was 0.62 mm/s and the gas velocity 29.6 cm/s; and that in tube 3, the extended tube, the liquid velocity was 0.32 mm/s and the gas velocity 34.2 cm/s. The second experiment was carried out to show that liquid can be substantially uniformly distributed to the reactor tubes even when liquid is supplied to the fluid inlet chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes is extremely low. In this experiment the test rig was provided with five reactor tubes. The reactor tubes were filled with spheres having a diameter of 1.5 mm, and the void fraction in the reactor tubes was 0.36 m³ voids/m³ bed. At first decane was supplied to the fluid distribution chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes was 3.3 mm/s, and nitrogen was supplied at such a rate that the pressure in the fluid inlet chamber was maintained at 0.53 bar (gauge) resulting in an average gas velocity of 17 cm/s. It was found that the spread of the liquid velocities in the tubes was 8% and that the spread of the gas velocities in the tubes was 2%. Then decane was supplied to the fluid distribution chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes was 0.36 mm/s, and nitrogen was supplied at such a rate that the pressure in the fluid inlet chamber was maintained at 0.53 bar (gauge) resulting in an average gas velocity of 35 cm/s. It was found that the spread of the liquid velocities in the tubes was 15% and that the spread of the gas velocities in the tubes was 2%. The third experiment was carried out to show that liquid can be substantially uniformly distributed to the reactor tubes even when liquid is supplied to the fluid inlet chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes is extremely low, and that the gas velocities in the reactor tubes are substantially insensitive to the void fractions in the reactor tubes. In this experiment the test rig was provided with five reactor tubes. The reactor tubes were filled with spheres having a diameter of 1.5 mm, and the void fractions in the reactor tubes were in the range of from 0.36 to 0.39 m³ voids/m³ bed. At first decane was supplied to the fluid distribution chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes was 3.8 mm/s, and nitrogen was supplied at such a rate that the pressure in the fluid inlet chamber was maintained at 0.53 bar (gauge) resulting in an average gas velocity of 15 cm/s. It was found that the spread of the liquid velocities in the tubes was 25% and that the spread of the gas velocities in the tubes was 4%. Then decane was supplied to the fluid distribution chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes was 0.7 mm/s, and nitrogen was supplied at such a rate that the pressure in the fluid inlet chamber was maintained at 0.53 bar (gauge) resulting in an average gas velocity 34 cm/s. It was found that the spread of the liquid velocities in the tubes was 44% and that the spread of the gas velocities in the tubes was 3%. The presence of the gas and liquid supply means reduces the variations of the liquid velocity in the reactor tubes due to tilt of the vessel and sagging of the upper tube plate. The fourth experiment was carried out to show the effect of the presence of the gas and liquid distributor. In this experiment the test rig was provided with four reactor tubes. The reactor tubes were filled with spheres having a diameter of 1.5 mm, and the void fractions in the reactor tubes were in the range of from 0.41 to 0.45 m³ voids/m³ bed. At first decane was supplied to the fluid distribution chamber at such a volumetric flow rate that the average liquid velocity in the reactor tubes was 1.9 mm/s, and nitrogen was supplied at such a rate that the pressure in the fluid inlet chamber was maintained at 0.53 bar (gauge) resulting in an average gas velocity of 45 cm/s. It was found that the spread of the liquid velocities in the tubes was 21% and that the spread of the gas velocities in the tubes was 4%. Then the gas and liquid distributors were removed and in four tests each reactor tube tested individually. Decane was supplied at such a rate that the liquid velocity in the reactor tubes was 2.0 mm/s, and nitrogen was supplied at such a rate that the pressure in the fluid inlet chamber was maintained at 0.53 bar (gauge) resulting in an average gas velocity of 44 cm/s. It was found that spread of the gas velocities in the tubes was 7%. In an alternative embodiment the extension tube of the gas and liquid supply means is formed by a downcomer tube extending into the upper end part of the reactor tube. Reference is made to Figure 3 showing an alternative of the apparatus as shown in Figure 2. Parts of the device which correspond to parts shown in Figures 1 and 2 have the same reference numerals. The multitube reactor is provided with a horizontal tray 60, which tray rests on an impermeable layer 61, which is supported by the upper tube plate 5. Reactor tubes 2 are provided with extension tubes 63 which pass through the impermeable layer 61 and the bottom of the horizontal tray 60. The operation of the multitube reactor as discussed with reference to in Figure 3 is similar to the operation of the multitube reactor as discussed with reference to in Figures 1 and 2. In an alternative embodiment the impermeable layer 61 may be replaced by sealing rings (not shown) arranged in the annular zones between the inner walls of the reactor tubes 2 and the outer walls of the extension tubes 63. Reference is now made to Figures 4 and 5 showing a further alternative of the gas and liquid supply device. Parts of the device which correspond to parts shown in Figures 1, 2 and 3 have the same reference numerals. The liquid supply device 25 is provided with three longitudinal dents 70 so as to allow securing the liquid supply device on the extension tube 63. To make the liquid supply device less sensitive to fouling, the liquid supply device 25 is provided with an opening 71 which is arranged in the layer of liquid present on the tube plate 5 during normal operation. To facilitate positioning of the liquid supply device 25, it is provided with legs 72. Suitably, the distance between the gas inlet opening 27 (see Figure 2) and the outlet 30 of the inlet chamber 26 is in the range of from 0.1 to 3 times the inner diameter of the reactor tube 2. The diameter of the gas inlet opening 27 is suitably in the range of from 2 to 30% of the inner diameter of the reactor tube 2. A further example of a process in which the multitube reactor according to the invention can be used is the reaction between hydrogen and acetone to form methyl isobutane ketone and water.

Claims: 1. Multitube reactor suitable for carrying out catalytic processes, comprising a normally substantially vertically extending vessel, a plurality of open-ended reactor tubes arranged in the vessel parallel to its central longitudinal axis of which the upper ends are fixed to an upper tube plate and in fluid communication with a fluid inlet chamber above the upper tube plate and of which the lower ends are fixed to a lower tube plate and in fluid communication with an effluent collecting chamber below the lower tube plate, liquid supply means for supplying liquid to the fluid inlet chamber, gas supply means for supplying gas to the fluid inlet chamber, and an effluent outlet arranged in the effluent collecting chamber, wherein the upper end part of each reactor tube is provided with a gas and liquid supply device, which device comprises an inlet chamber having a gas inlet opening, a liquid inlet and an outlet which is in fluid communication with the upper end part of the reactor tube, and a liquid riser extending between a level in the layer of liquid which is during normal operation present in the fluid inlet chamber and the liquid inlet of the inlet chamber. 2. Multitube reactor as claimed in claim 1, wherein the liquid riser is the annular space between a conduit arranged around the upper part of an extension tube which is in fluid communication with the reactor tube. 3. Multitube reactor as claimed in claim 2, wherein the extension tube is formed by the upper end part of the reactor tube. 4. Multitube reactor as claimed in claim 2, wherein the extension tube is formed by a downcomer tube extending into the upper end part of the reactor tube. 5. Multitube reactor as claimed in any one of the claims 1-4, wherein the multitube reactor is provided with a horizontal tray arranged above the upper tube plate, and wherein the extension tubes pass through the bottom of the horizontal tray. 6. Multitube reactor as claimed in any one of the claims 2-5, wherein the gas and liquid supply device is provided with longitudinal dents to allow securing the liquid supply device to the extension tube. 7. Multitube reactor as claimed in any one of the claims 1-6, wherein the distance between the gas inlet opening and the outlet of the inlet chamber is in the range of from 0.1 to 3 times the inner diameter of the reactor tube. 8. Multitube reactor as claimed in any one of the claims 1-7, wherein the diameter of the gas inlet opening is in the range of from 2 to 30% of the inner diameter of the reactor tube.

Inventors: SCHRAUWEN, FRANCISCUS JOHANNES MARIA, WESTERMAN, DAVID
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1988
Main classification: B01J8
IPC codes: C07C45, C07C1, B01J8, C10G5, C07C67, C07C49