GB2060426A - Reactor having dual upflow catalyst beds - Google Patents

Abstract

A vertical catalytic reactor (10) contains two catalyst beds (12, 20) located one above the other and connected in parallel flow arrangement. The effluent from the lower catalyst bed (12) bypasses the adjacent upper bed (20), and the effluents from both beds are combined and pass out of the reactor at its upper end (26). Generally, a conical grid plate (16) directing uniform fluid flow to the lower catalyst bed (12) is supported principally on rigid thermal insulation (17) in the lower head (18), and is restrained from upward movement by tension members. The lower grid assembly (16) also supports the upper catalyst bed (20) and its grid plate (22). Such a reactor is suitable for use in petroleum residuum conversion, hydrocarbon upgrading and coal liquefaction and hydrogenation. <IMAGE>

Description

SPECIFICATION Reactor having dual upflow catalyst beds This invention relates to pressurized reactors containing upflow catalytic beds, and particularly to such a reactor having dual catalyst beds arranged for parallel upflow of the feedstream inside a single pressurizable shell, and a process for using this reactor.

As design flow rates for high pressure catalytic reaction processes, such as petroleum residuum conversion, hydrocarbon upgrading and coal liquefaction and hydrogenation, increase to the point of requiring multiple reactors, such as 4 to 10 units connected in parallel or parallel/series arrangements, the investment costs for such multiple reactors increase substantially. Such cost increases are due in large part to the increased number of high pressure vessel heads required for the construction of the reactors.

In order to minimize the number of individual pressurized reactor vessels needed for large flow capacities, it has been proposed to provide two parallel flow reaction zones or catalyst beds within a single elongated pressurized vessel. Although this arrangement increases the length of each reactor substantially, it halves the number of expensive dished heads required, and results in significant overall savings in cost and space needed for the reactor vessels for a particular total feed rate requirement.

Multiple reaction zones in catalytic reactors have been used previously. For example, U.S.

Patent No. 2,987,468 to Chervenak and U.S.

Patent No. 3,183,178 to Wolk show the use of ebullated catalyst bed reaction zones connected in series within a single pressure shell for petroleum processing. However, reactors having ebullated catalytic beds connected in parallel with a common pressure shell have apparently not been previously used.

The present invention provides a process for catalytically reacting a feedstock, comprising the steps of: (a) introducing a portion of the feedstock into a catalyst bed located in the lower portion of a vertically oriented reactor vessel; (b) introducing the remaining portion of the feedstock into a catalyst bed located in the upper portion of the reactor vessel; (c) passing the effluent from the lower catalyst bed upwardly to bypass the upper catalyst bed; and (d) combining the effluent from both catalyst beds and withdrawing it from the reactor vessel at its upper end as a common effluent stream.

The invention also provides a catalytic reactor assembly comprising: (a) a vessel having upper and lower heads; (b) a catalyst bed located in the lower portion of the vessel and above a grid plate; (c) a catalyst bed located in the upper portion of the vessel and supported from the lower bed flow distributor grid by an elongated inlet pipe, this upper bed being adapted so that effluent from the lower bed can bypass the upper bed; (d) conduit means for introducing a feedstream into the lower catalyst bed; (e) conduit means for separately introducing a feedstream into the upper catalyst bed; and (f) outlet means for withdrawing the combined effluent stream from both catalyst beds from the reactor at its upper end.

According, to the present invention, a reactor has dual ebullated catalyst beds in parallel flow arrangement, and also both reaction zones are preferably supported from a special grid plate assembly located in the bottom portion of the reactor. The lower grid is supported principally by thermal insulation in the lower head and provides for uniform stress distribution within the grid and lower head during pressure and temperature cycling during process operations.

According to the invention, a vertical catalytic reactor has dual catalyst beds located one above the other within a single pressurizable vessel. The reactor beds are operated in parallel flow arrangement of the feedstream for reaction processes using catalytic upflow fluidized or ebullated catalyst beds. The liquid and gaseous effluent from the lower bed flows around the upper bed and/or through one or more vertical conduits within the upper bed to the reactor outlet opening.

The lower catalyst reaction bed and its grid plate providing for uniform flow distribution in the bed can be supported in any convenient manner, such as by ring support from the reactor shell; however the lower grid plate is preferably supported principally on cast refractory thermal insulation located in the bottom head of the reactor vessel. The upper catalyst reaction bed is supported by its inlet vertical conduit, which is in turn attached to and supported from the lower grid plate.

It is an advantage of this dual catalyst bed reactor configuration that the total number of reactor vessels needed for a particular total feed requirement is reduced by half, as the reactor dual catalyst beds are provided in tandem within a common pressure shell. Thus, although each reactor shell is extended in length, fewer dished heads and less external piping are required, thereby resulting in significant overall cost savings. The catalyst beds operate in all-liquid phase, and the effluent from both beds is withdrawn from the top of the common pressure vessel and passes to a further processing such as external phase separation.

In an alternative design for a dual ebullated bed reactor, a plurality of tubular riser conduits are provided which pass through the upper catalyst bed for handling the effluent from the lower catalyst bed, instead of having all the effluent pass around the upper reaction bed. Also, the lower catalyst bed is preferably supported principally on the cast refractory thermal insulation in the bottom head of the reactor, and is restrained from appreciable upward movement by a plurality of tension members extending between the grid assembly and the lower head of the reactor. The upper catalyst bed and its grid plate assembly are supported from the grid plate assembly for the lower catalyst bed.

Suitable operating pressures for this dual catalyst bed reactor can range from at least about 200 psig kg/cm2) to as high as 10,000 psig (703 kg/cm2), and reactor temperatures usually range from about 3000F to 1 5000F (1490 to 8160 C). For reactors operating at temperatures above about 4000F (2040 C), the reactor is usually lined internally with solid thermal insulation which is abrasion-resistant. This reactor configuration is particularly useful for the catalyst hydroprocessing of hydrocarbon feedstreams, such as for petroleum conversion and coal hydrogenation, in which the particulate catalyst material is introduced along with the feedstream. The particle size of catalysts useful for this invention is usually within the range of 20-400 mesh (U.S.Sieve Series) and the catalyst can be any shape such as spherical or extrudates. Used catalyst is withdrawn separately from each bed as required .to maintain the desired level of catalytic activity.

While this invention can be used for reactors having any upflow type particulate catalyst beds, it is most advantageously and preferably used for ebullated type catalyst beds as described in U.S.

Patent No. Re, 25,770 to Johanson.

Reference is now made to the accompanying drawings, in which: Figure 1 shows a reactor vessel containing dual catalyst beds connected in parallel flow arrangement; Figure 2 shows an alternative reactor configuration having dual catalyst beds in parallel flow arrangement, with the grid assembly for the lower bed principally supported on the refractory insulation; and Figure 3 shows an enlarged view of the lower grid assembly of Figure 2 having tension members between the grid and the lower head.

As illustrated by Figure 1, a reactor vessel generally shown at 10 contains a lower catalyst bed 12 and an upper catalyst bed 20. The feed liquid for the lower bed 12 is provided through an annular conduit or passage 1 4 and then through a lower grid plate assembly 1 6 containing multiple openings or nozzles 16a. The catalyst bed is expanded by the upflowing feed stream, which is usually a mixture of liquid and gas, to an upper level 12a.

The grid plate assembly 1 6 is supported principally by refractory insulation 1 7 situated within a lower head 1 8 of the vessel, so as to provide for uniform differential thermal expansion of the grid plate 16 relative to the vessel wall and the head 18. The grid plate assembly 1 6 is also restrained from substantial upward movement due to differential pressure across the nozzles by the inlet conduit 1 5. Fresh catalyst is provided mixed with the feed as needed, and used catalyst is withdrawn through a conduit 13 as needed to maintain the desired catalytic activity within the bed.

An upper catalyst bed 20 is arranged in parallel fluid flow arrangement with the lower bed 12, with the feed liquid being provided flowing upwardly through a central inlet conduit 21. The catalyst bed 20 is similarly expanded by the upflowing fluid to a level 20a. The central conduit 21 also provides the support for the upper catalyst bed 20 and the grid plate assembly 22 from the lower grid assembly 1 6. The effluent flow from the lower bed 12 passes around the upper bed 20 through an annular passageway 24, and is combined with the effluent from the upper bed 20 before it leaves the reactor vessel at an outlet opening 26. Fresh catalyst is provided mixed with the feedstream as needed, and used catalyst is withdrawn through a conduit 23 similarly as for the lower bed, with the conduit 23 being preferably located within the inlet flow conduit 21.

The length/diameter ratio of each catalyst bed in its settled condition should be between about 1 and 10, with lower ratios usually being used for larger diameter beds, and the percent bed expansion during operations should be between about 30 and 150% of its settled height. For reactors having normal operating temperatures above about 4000F (2040 C), an internal thermal insulation lining 1 9 is usually provided of erosionresistant solid refractory type insulation, such as Fractocrete No. 3400 available from Combustion Engineering Company.

Figure 2 shows an alternative flow configuration for the upper catalyst bed 20 in the reactor 10. In addition to providing an annular passageway 24 around the bed for flow of the effluent from the lower catalyst bed 12, a plurality of generally vertical conduits 28 are provided through the bed. The conduits 28 pass through the upper grid 22 and extend to a level above the expanded catalyst bed level 20a. Thus, if for any reason the annular flow passageway 24 becomes obstructed during operations, the additional flow passageways 28 are available to convey the effluent from the lower bed 12 to the outlet 26.

Also, the upper bed 20 and the grid plate 22 are supported by the flow conduit 21, which is in turn supported by the lower grid 16, principally by the refractory insulation 1 7 situated within the lower head 18. The grid support arrangement provides for uniform differential thermal expansion of the grid plate 16 relative to the reactor wall 19. A layer 1 7a of refractory fibres, such as Kaowool, provided by Babcock-Wilcox Co., is preferably placed between the lower plate of the grid 1 6 and the refractory insulation 1 7 to provide for more uniform contact between these elements. Also as mentioned, the lower grid plate assembly 1 6 is restrained from upward movement due to differential pressure across the grid nozzles 22a by a plurality of tension members 30 extending from the grid assembly 1 6 through the refractory insulation 1 7 to the reactor lower head 1 8. As shown in Figure 3, compression spring means 32, preferably a bellville type spring, are provided at the upper end of the member 30 to accommodate thermal expansion of structural parts and provide a net downward force on the grid against the insulation 1 7. A pressure-tight cap 34 is provided to retain reactor pressure within the grid assembly 16. The spring 32 also restrains upward movement of the grid.

Although the lower grid plate assembly 1 6 is supported principally by rigid insulation 1 7 shown being used with dual catalyst beds, this grid assembly can also be used advantageously in a reactor having a single catalyst bed.

Although we have disclosed certain preferred embodiments of our invention, it is recognized that modification can be made thereto and that some features can be employed without other all within the spirit and scope of the invention, which is defined solely by the following claims.

Claims (17)

1. A process for catalytically reacting a feedstock, comprising the steps of: (a) introducing a portion of the feedstock into a catalyst bed located in the lower portion of a vertically oriented reactor vessel; (b) introducing the remaining portion of the feedstock into a catalyst bed located in the upper portion of the reactor vessel; (c) passing the effluent from the lower catalyst bed upwardly to bypass the upper catalyst bed; and (d) combining the effluent from both catalyst beds and withdrawing it from the reactor vessel at its upper end as a common effluent stream.

2. A process as claimed in claim 1, wherein all the effluent from the lower catalyst bed flows upwardly around the periphery of the upper catalyst bed.

3. A process as claimed in claim 1, wherein effluent from the lower catalyst bed bypasses the upper catalyst bed by passing upwardly through a plurality of conduits extending through the upper catalyst bed.

4. A process as claimed in any of claims 1 to 3, wherein the feedstock is a heavy hydrocarbon liquid which produces a lower boiling gas and liquid effluent products by catalytic reaction within the pressure range of from 200 to 10,000 psig (14 to 703 kg/cm2) and temperature range of from 300 to 15000F(149to8160C).

5. A catalytic reactor assembly comprising: (a) a vessel having upper and lower heads; (b) a catalyst bed located in the lower portion of the vessel and above a grid plate; (c) a catalyst bed located in the upper portion of the vessel and supported from the lower bed flow distributor grid by an elongated inlet pipe, the upper bed being adapted so that effluent from the lower bed can bypass the upper bed; (d) conduit means for introducing a feedstream into the lower catalyst bed; (e) conduit means for separately introducing a feedstream into the upper catalyst bed; and (f) outlet means for withdrawing the combined effluent stream from both catalyst beds from the reactor at its upper end.

6. A reactor assembly as claimed in claim 5, wherein the upper catalyst bed has an outside diameter smaller than the vessel inner wall, the bed being centrally located to provide an annular space between the catalyst bed and inner wall surface of the reactor for passage of effluent from the lower bed.

7. A reactor assembly as claimed in claim 5, wherein the upper catalyst bed contains a plurality of conduits extending vertically therethrough for passing effluent from the lower bed to the reactor outlet means.

8. A reactor assembly as claimed in any of claims 5 to 7, wherein the upper catalyst bed is supported from the flow distributor grid of the lower bed.

9. A reactor assembly as claimed in any of claims 5 to 8, wherein the lower grid plate is supported principally by solid thermal insulation in the lower head and is restrained from substantial upward movement by a plurality of tension members extending between the grid and the lower head of the reactor.

10. A reactor assembly as claimed in any of claims 5 to 9, wherein the reactor is internally lined with solid thermal insulation.

11. A catalytic bed type reactor assembly, comprising: (a) a pressurizable vessel having upper and lower heads and containing internal solid type thermal insulation adjacent to its inner wall; (b) a lower catalyst bed located in the lower portion of the vessel and above a flow distribution grid plate, which grid is supported principally by solid thermal insulation located in the lower head; (c) an upper catalyst bed located in the upper portion of the vessel and supported from the lower flow distribution grid plate by an elongated inlet pipe, the upper bed being adapted so that effluent from the lower bed bypasses the upper bed; (d) conduit means for introducing a pressurized feedstream upwardly into the lower grid plate; (e) conduit means for separately introducing a feedstream into the upper catalyst bed;; (f) structural means for restraining upward movement of the lower grid plate due to pressure differential existing therein; and (g) outlet means for withdrawing the combined effluent steam from both catalyst beds of the reactor at its upper end.

12. An assembly as claimed in claim 11, wherein the grid plate assembly contains a plurality of nozzle openings in its upper surface, and the upward movement restraining means comprises multiple rods connecting the grid to the lower head.

13. An assembly as claimed in claim 11, wherein the grid plate assembly is restrained from upward movement by a tubular connection between the inner diameter of the grid and the reactor inlet nozzle opening.

14. A catalytic bed type reactor assembly, comprising: (a) a pressurizable vessel having upper and lower heads; (b) a catalyst bed located in the lower portion of the vessel and above a flow distribution grid plate, which grid is supported principally by solid thermal insulation located in the lower head; (c) conduit means for introducing a pressurized feedstream upwardly into the lower grid plate; (d) structural means for restraining upward movement of the grid plate due to pressure differential existing therein; and (e) outlet means for withdrawing the effluent stream from the catalyst bed.

15. An assembly as claimed in claim 14, wherein the grid plate assembly contains a plurality of nozzle openings in its upper surface, and the upward movement restraining means comprises multiple rods connecting the grid to the lower head.

16. An assembly as claimed in claim 14, wherein the grid plate assembly is restrained from upward movement by a tubular connection between the inner diameter of the grid and the reactor inlet nozzle opening.

17. An assembly as claimed in any of claims 14 to 1 6, wherein the reactor is internally lined with solid thermal insulation.

1 8. A process as claimed in claim 1, substantially as hereinbefore described with reference to the accompanying drawings.

1 9. A catalytic reactor assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.