CATALYTIC CONVERSION OF LIQUID AND/OR GAS

Abstract: The invention relates to catalytic conversion of fluid introduced into the upper end of a vessel (1), passed through a catalyst bed in the vessel (1), passed through passages (20) between guide elements (14) arranged in the vessel (1), and removed from the lower end of the vessel (1), wherein at or near the narrow parts of the passages (20) cooling fluid is introduced into the passages (20) to control the temperature in the catalyst bed.

Description: The invention relates to a process for the catalytic conversion of a liquid and/or a gas comprising the steps of introducing in the upper end of a vessel the liquid to be converted and a gas or the gas to be converted and a liquid, passing said liquid and gas through a bed of catalyst particles within the vessel, and removing the effluent obtained by the catalytic conversion from the lower end of the vessel. Examples of such a process are hydroprocessing, hydro-­ desulphurization or hydrocracking. A further example is the catalytic conversion of synthesis gas, comprising hydrogen and carbon monoxide, into hydrocarbons in the boiling range of middle distillates. These processes are exothermic. To control the temperatures in the catalyst bed it is known to allow the fluids participating in the conversion to flow out of the catalyst bed into a plurality of hollow bars with permeable walls, in which hollow bars the fluids are mixed with cooling fluid, and to allow the cooled fluids to enter the catalyst bed downstream the hollow bars. A disadvantage of the known process is that the permeable walls can easily be blocked by fragments of catalyst particles or by deposits of coke from the fluid, so that the fluids may have difficulties to reach the mixing zone inside the hollow bars. It is an object of the present invention to overcome the above disadvantage. To this end the process for the catalytic conversion of a liquid and/or a gas according to the invention comprises the steps of introducing in the upper end of a vessel the liquid to be converted and a gas or the gas to be converted and a liquid, passing said liquid and gas through a bed of catalyst particles within the vessel, allowing the liquid and gas to pass through a plurality of passages defined between the outer surfaces of guide elements arranged in the bed of catalyst particles, passages having in the direction of flow a narrowing part, a narrow part and a widening part, introducing an additional fluid into the passages at the narrowing parts or at or near the narrow parts of the passages, and removing the effluent obtained by the catalytic conversion from the lower end of the vessel. The specification further relates to an apparatus for carrying out the process of catalytic conversion of a liquid or a gas comprising a vessel, inlet means for introducing into the vessel fluids and catalyst particles arranged at the upper end of the vessel, support means for supporting the bed of catalyst particles in the vessel, and discharge means for discharging from the vessel effluent and catalyst particles at the lower end of the vessel. In the known apparatus, there is provided a grid of hollow bars having fluid permeable outer walls in which hollow bars there are arranged spray means for introducing, during normal operation, cooling fluid in the hollow bars, which cooling fluid will mix with the fluids that pass from this catalyst bed into the hollow bars. It is an object of the invention to provide an improved apparatus. To this end the apparatus for carrying out a process for the catalytic conversion of a liquid and/or a gas according to the invention comprises a vessel, inlet means for introducing into the vessel fluids and catalyst particles arranged at the upper end of the vessel, support means for supporting a bed of catalyst particles in the vessel, discharge means for discharging from the vessel effluent and catalyst particles arranged at the lower end of the vessel, and a grid of guide elements which is arranged in the vessel substantially perpendicular to the direction of fluid flow, wherein between the parts of the outer surfaces of adjacent guide elements facing each other a passage is defined having in the direction of fluid flow a narrowing part, a narrow part and a widening part, and wherein the guide elements are provided with means for introducing additional fluid into the passage, which means are arranged along the narrowing part or at or near the narrow part of the passage. The invention will now be described by way of example in more detail with reference to the drawings, wherein Figure 1 shows schematically a longitudinal section of the apparatus; Figure 2 shows a cross-section of the apparatus shown in Figure 1 along the line II-II; Figure 3 shows detail III of the apparatus shown in Figure 1 drawn to a scale larger than the scale of Figure 1; and Figure 4 shows a cross-section of an alternative design of a guide element. Reference is now made to Figures 1, 2 and 3. The apparatus according to the invention comprises a vessel 1, a fluid inlet 2 and a catalyst inlet 3 arranged at the upper end of the vessel 1, and a fluid outlet 4 and a catalyst outlet 5 arranged at the lower end of the vessel 1. Furthermore, the vessel 1 comprises a support cone 8 for supporting a bed of catalyst particles (not shown) in the vessel 1, which support cone 8 has a central opening 9 which is connected by means of tube 10 to the catalyst outlet 5. Furthermore, the catalyst outlet 5 is provided with valve means (not shown) for allowing or stopping discharging of catalyst particles from the vessel 1. In addition, the vessel 1 is provided with a first grid 12 and a second grid 13, which grids are arranged at different levels in the vessel 1 substantially perpendicular to the direction of fluid flow through the vessel 1. Each grid comprises guide elements 14, which are connected to a ring-shaped support member 18 joined to the inner surface of the side-wall of the vessel 1. The guide elements pertaining to the first grid 12 are preferably staggered with respect to the guide elements pertaining to the second grid 13. Between the facing parts of outer surfaces of adjacent guide elements 14, and between the facing parts of the outer surfaces of the ring-shaped support member 18 and the adjacent guide elements there are defined passages indicated with reference numeral 20. Each of the passages 20 comprises in the direction of fluid flow a narrowing part 21, a narrow part 22 and a widening part 23. For the sake of clarity, the reference numerals referring to the parts of the passages 20 have only been included in Figure 3. Each guide element 14 comprises a triangular fluid feed cap 25 (see Figure 3) having side walls 26 and a bottom wall 28, in which fluid feed cap 25 a fluid conduit 29 is arranged. Each ring-shaped support member 18 comprises a fluid feed cap 30 having side wall 26 and bottom wall 28, in which fluid feed cap 30 there is arranged a fluid supply conduit 31 which is in fluid communication with the fluid conduits 29 in the triangular fluid feed caps 25 and with an additional fluid inlet 32 (see Figure 2). Each of the fluid feed caps 25 and 30 is supported by a support beam 33. The fluid feed cap is so wide that the bottom wall 28 extends beyond the support beam 33, along the length of the support beam 33. In the part of the bottom wall 28 extending beyond the support beam 33 there are arranged means for intro-­ ducing additional fluid into a passage in the form of a row of outlet openings 35 (see Figure 3), which are in fluid commu-­ nication with the fluid conduit 29, or, for the outlet openings 35 pertaining to the ring-shaped support member 18, with the fluid supply conduit 31. It will be appreciated that the above described details of the guide elements and ring-shaped support member pertaining to the second grid 13 are included as well in the guide element and the ring-shaped support member pertaining to the first grid 12. The process of catalytic conversion of sulphur containing hydrocarbon oil into a substantially sulphur-free hydrocarbon oil with the use of hydrogen will now be described. Catalyst particles are supplied via the catalyst inlet 3 until the space above the support cone 8 and in the tube 10 is filled with a bed of catalyst particles (not shown). Subsequently a mixture of sulphur containing hydrocarbon oil and hydrogen, at a temperature in the range of from 300 °C to 500 °C and at a pressure in the range of from 3 MPa to 25 MPa, is introduced into the vessel 1 via the fluid inlet 2. In the reactor an exothermic reaction will occur, wherein hydrogen and the sulphur in the sulphur containing hydrocarbon oil react to give hydrogen sulphide and a substantially desulphurized hydrocarbon oil. The mixture of hydrocarbon oil and hydrogen sulphide is allowed to flow in downward direction and to pass through upward tilting separator slits 40 arranged in the wall of the tube 10 into an effluent collecting space 41 below the support cone 8, from which the mixture is discharged via fluid outlet 4. Upon cooling, the formed hydrogen sulphide is subsequently separated from the desulphurized hydrocarbon oil in a suitable separator (not shown). When the catalyst is deactivated, for example after 6 to 12 months the process is interrupted, all catalyst particles are discharged from the vessel 1, and the vessel 1 is subsequently filled with fresh catalyst particles. In order to control the temperature in the vessel addi- tional fluid in the form of cooling fluid, comprising, for example, cooled desulphurized hydrocarbon oil or quench gas, is supplied to the additional fluid inlet 32 pertaining to at least one of the grids 12 and 13, which cooling fluid will enter the passages 20 through the outlet openings 35 near the narrow parts 22 of the passages 20 (see Figure 3). In this manner the reaction products are cooled in the region where the passage is reduced, and consequently where the fluid velocity and turbulence are increased. Thus an improved heat exchange between the hot reaction products and the additional fluid is obtained. To obtain a sufficient heat exchange and a moderate pressure drop over a grid, the total cross-sectional area of the passages 20 should be in the range of from 30% to 60% of the cross-sectional area of the vessel 1, and preferably in the range of from 45% to 55%. The bottom walls 28 of the fluid feed caps 25 and 30 extend beyond the support beams 33. When the vessel is filled with catalyst particles (not shown), these particles will be so distributed in the vessel 1 that under the sides of the bottom walls 28 extending beyond the support beams 33 there exist catalyst-free distribution spaces 42 (see Figure 3) extending in longitudinal direction of the support beams 33. Since the fluid outlet openings 35 are arranged in the side of the bottom walls 28 extending beyond the support beam 33, cooling fluid is introduced in the distribution spaces 42 so that, before it enters the bed of catalyst particles, the cooling fluid is uniformly distributed in the distribution spaces 42. This reduces the change of a non-uniform temperature distribution in the catalyst bed in the passages 20. In order to obtain a uniform distribution of liquid flowing through the widening part 23 of each passage 20, the acute angle 43 between the vertical and the part of the outer surface of a guide element 14 or of the ring-shaped support member 18 defin-­ ing the widening part 23 should be matched with the liquid spreading angle. For liquids flowing through a bed of convention-­ al catalyst particles the acute angle 43 is in the range of from 3° to 10°. The uniform distribution of liquid in the widening part 23 of each passage 20 has a beneficial effect on the efficiency of reaction because non-uniform contacting of the liquid with catalyst and consequently non-uniform temperature distribution in the catalyst bed and consequently non-uniform fouling of catalyst particles is avoided. In the above described process, deactivated catalyst is refreshed only after substantially long periods. In an alternative embodiment of the invention, a volume of catalyst particles is discharged from the vessel and is replaced by a volume of fresh catalyst particles introduced into the vessel via the catalyst inlet 3. Moving the catalyst bed in bunker flow over a small distance so as to allow replacing a volume of deactivated catalyst particles by a volume of fresh catalyst particles may be carried out at short intervals, for example once a day. To ensure that, when the catalyst particles in the narrowing part 21 of a passage 20 move downwardly in a uniform manner, so that the catalyst particles near the surfaces defining the narrowing part 21 will move at about the same velocity as the catalyst particles in the central part of the narrowing part 21, the acute angle 44 between the vertical and the part of the outer surface of a guide element 14 or of the ring-shaped support member 18 defining the narrowing part 21 should be so selected that mass flow will occur. For conventional catalyst particles the acute angle 44 is in the range of from 10° to 40°. In an alternative process a gas is converted to a liquid, and, to this end a mixture of gas and liquid is introduced into the vessel through the fluid inlet 2. An example of such a process is the conversion of synthesis gas, comprising hydrogen and carbon monoxide, into a liquid hydrocarbon in the boiling range of a middle distillate. In this process a mixture of synthesis gas and recycled liquid hydrocarbon at a temperature in the range of from 200 °C to 250 °C and at a pressure in the range of from 2 MPa to 4 MPa is introduced in the catalyst bed in the reactor. In such a process the purpose of the liquid is to transfer heat so as to obtain a uniform temperature distribution in the catalyst bed in the vessel. During normal operation cooled recycled liquid hydrocarbon product is supplied to the additional fluid inlets 32 and enters the vessel 1 through the outlet openings 35 in order to cool the products. The apparatus described with reference to Figure 1 is provided with two grids of guide elements; a very small apparatus can be provided with only one grid of guide elements, and, on the other hand, a larger apparatus can be provided with more than one grid, for example 3 to 10 arranged at different levels in the vessel. In the guide elements described with reference to Figure 3, the means for introducing additional fluid into a passage are arranged in the sides of the bottom wall extending beyond the support beam, so that during normal operation additional fluid is introduced near the narrow part of the passage. Reference is now made to Figure 4 showing a guide element 45 that can replace part of, or all guide elements 14 in the grids 12 and 13 as described with reference to Figures 1, 2 and 3. The guide element 45 comprises a triangular fluid feed cap 46 supported by a support beam 47. Each side wall of the triangular fluid feed cap 46 comprises a lower strip 48 and an upper strip 49 extending along the length of the guide element 45, and so arranged one above the other that the lower part of the upper strip 49 overlaps the upper part of the lower strip 48. Means for introducing additional fluid into a passage in the form of a row of outlet openings 50 are arranged along the narrowing part of a passage in the area where the upper strip 49 overlaps the lower strip 48, which area extends along the guide element 45. In addition, bottom wall 53 of the fluid feed cap 46 is so wide that it extends beyond the support beam 47, and means for introducing additional fluid in the form of a row of outlet openings 54 are arranged in the part of the bottom wall 53 extending beyond the support beam 47. The outlet openings 50 and 54 are in fluid communication with a fluid conduit 55 arranged within the triangular fluid feed cap 46, which fluid conduit 55 is in fluid communication with the fluid supply conduit 31 pertaining to the ring-shaped support member 18 (see Figure 3). During normal operation, the vessel is filled with a bed of catalyst particles (not shown) so distributed in the vessel that there exist catalyst-free distributor spaces 56 and 57 below the area where the strips 49 overlap the strips 48 and below the sides of the bottom wall 53 extending beyond the support beam 47. Additional fluid, supplied to the fluid conduits 55 pertaining to the guide element 45 of each grid, will be introduced via the openings 50 and 54 into the narrowing parts and near the narrow part of each passage. The fluid feed cap pertaining to a ring-shaped support member can as well be provided with a side wall comprising two strips extending along the support member and so arranged that the lower part of the upper strip overlaps the upper part of the lower strip, wherein means for introducing additional fluid into the passage are arranged in the area where the upper strip overlaps the lower strip. The acute angle between the outer surfaces of the strips and the vertical should be in the range of from 10° to 40°. The sides of the triangular fluid feed cap may comprise more than two strips, for example 3 to 5, extending along the guide element and so arranged one above the other that the lower part of the upper strip overlaps the upper part of the lower strip, wherein means for introducing additional fluid are arranged in the area where the upper strip overlaps the lower strip so as to allow introduction of additional fluid into the narrowing part or at the narrow part of a passage. Each row of outlet openings 35 (see Figure 3), 50 and 54 (see Figure 4) extend along the corresponding guide elements, such a row of outlet openings can at least partly be replaced by a slit extending along at least part of the guide element. During normal operation, additional fluid in the form of a fluid required for the catalytic conversion can be supplied. An example of such an additional fluid is hydrogen gas supplied to maintain a required ratio between the volumes of sulphur containing hydrocarbon oil and hydrogen in the above described process of catalytic conversion of a sulphur containing hydrocarbon oil. Where the process of catalytic conversion of a liquid and/or a gas is endothermic, the additional fluid comprises a heating fluid, for example steam, or heated fluid required for the catalytic conversion. In an alternative embodiment, fluids can be sucked into the upper part of the fluid feed cap 46 (see Figure 4) through openings 50, mixed with additional fluid and introduced into the passages through openings 54. In the apparatus described with reference to Figure 1 the support means for supporting a bed of catalyst particles in the vessel 1 comprises a support cone 8. In an alternative embodiment of the invention the catalyst bed may be supported by a perforated plate or a wire mesh which have the additional advantage of enhancing the catalyst/fluid separation. The catalyst bed may alsobe supported by the bottom wall of the vessel 1. In addition, gas and liquid can be supplied to the vessel via separated inlet means. It will be appreciated that the apparatus may comprise more than one bed of catalyst particles arranged axially spaced apart in the vessel, wherein at least one of the beds is provided with the guide elements as described hereinabove.

Claims: 1. Process for the catalytic conversion of a liquid and/or a gas comprising the steps of introducing in the upper end of a vessel the liquid to be converted and a gas or the gas to be converted and a liquid, passing said liquid and gas through a bed of catalyst particles within the vessel, allowing the liquid and gas to pass through a plurality of passages defined between the outer surfaces of guide elements arranged in the bed of catalyst particles, passages having in the direction of flow a narrowing part, a narrow part and a widening part, introducing an additional fluid into the passages at the narrowing parts or at or near the narrow parts of the passages, and removing the effluent obtained by the catalytic conversion from the lower end of the vessel. 2. Process as claimed in claim 1, wherein the additional fluid comprises a cooling fluid. 3. Process as claimed in claims 1 or 2, wherein the additional fluid comprises a fluid required for the catalytic conversion. 4. Process as claimed in any one of the claims 1-3, further comprising discharging at the lower end of the vessel a volume of catalyst particles and introducing in the upper end of the vessel a volume of catalyst particles to replace the discharged volume of catalyst particles. 5. Apparatus for carrying out the process for catalytic conversion of a liquid and/or a gas comprising a vessel, inlet means for introducing into the vessel fluids and catalyst particles arranged at the upper end of the vessel, support means for supporting a bed of catalyst particles in the vessel, discharge means for discharging from the vessel effluent and catalyst particles arranged at the lower end of the vessel, and a grid of guide elements which is arranged in the vessel substantially perpendicular to the direction of fluid flow, wherein between the parts of the outer surfaces of adjacent guide elements facing each other a passage is defined having in the direction of fluid flow a narrowing part, a narrow part and a widening part, and wherein the guide elements are provided with means for introducing additional fluid into the passage, which means are arranged along the narrowing part or at or near the narrow part of the passage. 6. Apparatus as claimed in claim 5, wherein a guide element comprises a triangular fluid feed cap having two side walls and a bottom wall, which fluid feed cap is supported by a support beam of which the outer surface has an inverse triangular cross-section. 7. Apparatus as claimed in claim 6, wherein a side wall of the fluid feed cap is formed by at least two strips extending along the guide element and so arranged one above the other that the lower part of the upper strip overlaps the upper part of the lower strip, and wherein fluid passages are arranged in the area where the upper strip overlaps the lower strip. 8. Apparatus as claimed in claim 6 or 7, wherein the bottom wall of the fluid feed cap is so wide that the bottom wall extends beyond the support beam, and wherein the means for introducing additional fluid comprise openings arranged in the part of the bottom wall extending beyond the support beam. 9. Apparatus as claimed in any one of the claims 5-8, wherein the total cross-sectional area of the passages is in the range of from 30% to 60% of the cross-sectional area of the vessel. 10. Apparatus as claimed in any one of the claims 5-9, wherein the acute angle between the part of the outer surface of a guide element defining the narrowing part of the passage and the vertical is in the range of from 10° to 40°. 11. Apparatus as claimed in any one of the claims 5-10, wherein the acute angle between the part of the outer surface of a guide element defining the widening part of the passage and the vertical is in the range of from 3° to 10°. 12. Apparatus as claimed in any one of the claims 5-11, wherein the catalytic conventor comprises two or more grids of guide elements arranged at different levels in the vessel. 13. Apparatus as claimed in claim 12, wherein the guide elements of a grid are staggered with respect to the guide elements of an adjacent grid. 14. Apparatus for carrying out the process of catalytic treat- ment of a hydrocarbon oil substantially as described in the specification with reference to the accompanying drawings.

Inventors: SCOTT, ANDREW MICHAEL, WESTERMAN, DAVID WILLIAM BELL
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1986
Main classification: C10G45
IPC codes: B01J8, C10G49