GB2113113A

GB2113113A - Vapour-solid contacting device

Info

Publication number: GB2113113A
Application number: GB08301138A
Authority: GB
Inventors: Vaux George R De
Original assignee: Hydrocarbon Research Inc
Current assignee: Hydrocarbon Research Inc
Priority date: 1982-01-15
Filing date: 1983-01-17
Publication date: 1983-08-03
Also published as: DE3301341A1; JPS58196840A; NL8300166A; BE895617A; FR2519876A1; CA1201875A; ZA83282B; GB8301138D0

Abstract

A fluidized bed reactor has upper and lower fluidized beds which are separated by an ordered array packing zone consisting of stationary, parallel members to provide controlled hindered mixing of particulate solids and a gas flowing therethrough. The ordered array may comprise multiple rows of stationary, parallel members, which can be varied in their size, shape, and spacing to provide a void volume of from 20 to 80% and may contain catalytic material. in one embodiment, the stationary members are oriented substantially horizontally and particulate solids descend through the array in countercurrent flow against an upflowing hot gas. The horizontal rows of the members (11,12, 13) of the ordered array may be arranged to have an angle of rotation between them ranging from 0 to 90 DEG . <IMAGE>

Description

SPECIFICATION Vapour-solid contacting device This invention relates to vapour-solids contacting in a fluidized bed, and more particularly, it relates to gas-liquid-solids contacting in a fluidized bed in an ordered array device arranged to provide uniform hindered mixing and avoid agglomeration of particulate solids in a reaction zone.

Fluidized beds are often used for contacting vapour and particulate solid materials. Such devices have well-known properties but the most important and significant is that the fluid bed is normally a well-mixed bed of solid particles and acts as a stirred tank reactor for chemical reaction purposes.

In the fluidized bed cracking of heavy oils as described in U.S. Patent No. 2,861,943 to Finneran, there is disclosed a multi-zone reactor having an intermediate zone for restricted fluidiziation of a particulate carrier and stripping of adsorbed hydrocarbons. This arrangement, which is current practice, is illustrated in the accompanying FIG. 1, having two zones 1 and 2 of fluidized beds, which are each substantially isothermal but operate at different temperatures.

In this reactor, vapour passes upwardly from zone 1 through a hindered back-mixing zone 3 comprising a packed bed, and particulate solids pass downwardly from zone 2 through the hindered back-mixing zone into zone 1 countercurrent to upflowing gas. This hindered, i.e., restricted, zone 3 consists of a bed of random packings using materials, such as Raschig rings or spheres, supported on a grid plate 4 having openings smaller than the random packing material. A typical dense phase fluidized bed exists in both zone 1 and zone 2.

In some instances, the fluidized bed may be described as a fast fluidized bed having high superficial gas velocity, such as disclosed by Squires in U.S. Patent No. 3,840,353. In this arrangement, the general direction of the solids movement is upward and solids are recirculated within the reactor to maintain the bed at an appropriate density. In this type bed, there are some aspects of plug-flow behaviour without any stationary packing to provide hindered mixing of gas and solids.

The use of such stationary packed beds places undesirable process restraints on those gas-solids containing processes in which it is desired to provide a substantial temperature difference across the packed bed, particularly processes for upgrading heavy hydrocarbon feedstocks. Also, use of such stationary packing material, for which the individual pieces touch adjacent pieces, can cause localized agglomeration of the particulate solids within or passing through and consequently undesired plugging of the bed.

This invention provides a process for contacting particulate solids with a gas within an ordered array packing zone. The process comprises: (a) passing particulate solids through the ordered array packing zone having multiple rows of stationary, parallel members providing a void volume ranging from 20 to 80%; (b) passing a gas through the ordered array packing zone countercurrent to particulate solids to fluidize the particulate solids and to provide intimate contact between the gas and the solids; and (c) maintaining a hindered mixing of the solids and gas within the ordered array packing zone to provide a temperature of at least 11.100 (200F) across the packing zone.

The particulate solids may be passed either downward or upward through the ordered array packing zone while the gas is passed countercurrent to or co-current with the flow of the particulate solids. The particulate solids have a diameter of at least 0.051 mm (0.002 inches) and the superficial velocity of the gas ranges from 3.05 to 1 52 cm/sec (0.1 to 5.0 ft/sec). In the process, the particulate solids pass through the ordered array packing zone at a temperature of 454 to 7600C (850 to 1 4000F) and the gas passes through at a temperature ranging from 538 to 103800 (1000 to 19000F).

The invention also provides a reaction vessel which includes an upper zone for containing a fluidized bed of particulate solids, a lower zone for containing a fluidized bed of particulate solids and an intermediate packing zone which consists of an ordered array packing zone of stationary members that separate the upper and lower zones. The members which are stationary are fixed in horizontal rows which are arranged at an angle of rotation between them of 0 to 900.

Reference is now made to the accompanying drawings, in which: FIG. 1 is a schematic drawing of a prior art configuration of a packed bed containing a fluidized bed for gas-solids contacting; FIG. 2 is several views illustrating typical construction features for an ordered array packing zone according to the present invention; and FIG. 3 is a schematic drawing illustrating a multiple-zone reactor containing an ordered array packing zone.

The vapour-solids contacting process of the present invention is generally carried out in a reactor having two reactor zones separated by an ordered array packing zone of stationary parallel members for providing intimate vapour/solids contacting and hindered, i.e., restricted, backmixing of the particulate solids and gas passing through the array. The arrangement of the ordered array packing zone permits a temperature gradient to be established between the reaction zone and across the ordered array.

In the ordered array packing zone the individual stationary members are horizontally spaced apart from each other, preferably by use of individual spacer elements. The members are usually arranged in a plurality of horizontal rows, which can each have variable cross-sectional shapes and spacing, the rows being spaced vertically.

The reactor vessel in which the process is carried out has an upper and a lower zone which are separated by the packing zone which consists of the ordered array of members. The solids transfer in the reactor vessel can be upwardly from the lower zone through the upper zone, or downwardly from the upper zone through the lower zone, or there may be a net zero flux of solids between the upper and lower zones.

The particulate solids contained in or transferred through the ordered array packing zone can be catalytic or non-catalytic. Also, the members of the ordered array packing zone may contain catalytic materials. Such catalytic materials can be selected to provide a typical chemical reaction desired. As an example of such a chemical reaction, a gas from the lower zone might consist of a synthesis gas containing CO. H2, H2O, and a catalyst could be incorporated in or coated on the members of the packing zone to cause the reaction equilibrium to shift towards producing more hydrogen. Thus, the hydrogen might then be more useful in the upper zone.

As illustrated in FIG. 3, the entire reactor might consist substantially of stationary packing so that zone 1 and zone 2 are reduced to near zero volume. The entire reactor would then consist essentially of a fluidized bed in an ordered array in which gradients could be obtained. Therefore, a fluid bed reactor would be provided having a gradient through it so as to obtain, for example, better yields of reacted products.

The present invention provides a novel reactor design configuration whereby a fixed bed of packed material is used in an ordered array configuration and vapour and solid particles are placed in intimate contact therein. The solid particles, as well as being catalytic or noncatalytic, may be absorptive or non-absorptive.

This type of reactor system using an ordered array permits a fluid bed of solids to be used and to obtain intimate contact between the vapour and the solid particles. At the same time, it permits gradients to exist within the bed which include temperature, concentration, solids age, and the solids dimensions, either specific gravity or diameters. Because the solids particles are in constant random motion, they may be added to or withdrawn from the ordered array at any point, or withdrawn from above of below the packing zone.

According to the present invention, various characteristics of the ordered array packing zone can be advantageously altered to suit specific applications. These characteristics include the shape of the packing zone members which may be a circle, a square, a diamond, a rectangle or a triangle, or any other suitable geometric shape, the horizontal spacing between the packing members, and the vertical spacing between the rows of the members. The sizes of the members are additional factors of variability, as is the angle of rotation between rows a further design variable.

The members may be solid, hollow, have a roughened-surfaced or be finned.

Referring to FIG. 2, there are shown several construction features for an ordered array packing zone according to the present invention. In FIG.

2A, there is illustrated three rows of rods 11, 12, 13 arranged at an angle of rotation between them of 900. The rows of members, e.g.. rods, are arranged at an angle of rotation between them of O to 90 . Supports 14, 15, 16 for the packing zone members are braced on shelves 17 from the vessel wall 18 or can be supported directly from horizontal beams provided in the reactor. Rows of members are supported on saddles which maintain the internal dimensions of the packed array. FIG. 2B is a top view and FIG. 2C is a front view of the support. The appropriate choice of variables in the ordered array permits a wide range of packing void fractions to be achieved, such as a void volume ranging from about 5 to 95%, and preferably from about 20 to about 80%.

As shown in FIG. 3, the members, e.g., rods, are extended completely across the reactor vessel, which eliminates the need for a grid beneath the ordered array of members. Each member, e.g., rod, being self-supporting permits a broader span to be handled with a given material and operating temperature.

Moreover, the dimensions and spacing of the members, e.g., rods, should be such that the fluidized solid particles will readily pass through them. The ordered array of members may be arranged to gradually increase the vertical spacing between adjacent rows of the members, e.g., rods, from the top to the bottom, thereby assuring that any particulate solids which enter the ordered array packing zone will pass on through.

Different sections of the ordered array might have different purposes. As illustrated in FIG. 3, Part A, which is immediately above the gasification or lower zone 1, could be designed to withstand high temperatures. In this zone a packing material having high mechanical strength in relation to its weight would be used. Such a section of specially designed material would permit the hot gases from zone 1 to be cooled prior to entering the ordered array packing zone. In Part B, the rods might, for example, have a vertical spacing such that each rod is self-supporting and no rod could sag enough to touch another.

In Part C of the ordered array, the vertical spacing between members, e.g., rods, might be reduced to near zero. By doing this, all of the members could act together to support the weight of a slumped bed from zone 2.

The advantages of the invention described herein will be further illustrated by the following example which should not be construed as limiting in scope.

EXAMPLE An ordered array according to the present invention is constructed which consists of three rows of horizontal rods, 5.08 cm (2.0 inches) in diameter, and arranged in a staggered triangular pitch pattern of about 6.6 cm (2.6 inch) center to center spacing. The rods are separated by angularshaped spacers or washers circumferentially mounted on the rods to provide a void volume of about 50%. The rods are supported by structural beams attached to the reactor inner wall, to provide an array of about 2.44 m (8 feet) diameter by 1.22 m (4 feet) deep. The packed array contains a bed of inert particulate solids such as a clay or an alumina having a particle size of 0.127-1.27 mm (0.005--0.050 inches) which are fluidized by a hot reducing gas passing upwardly through the bed.Particulate carrier solids containing coke deposits with some hydrocarbon liquid on and within the particles pass downwardly through the array counter-current to the upflowing gas. The particulate solids enter the ordered array at the top of about 5380C (10000 F) and exit the ordered array at the bottom at a temperature slightly less than the gas entering the array. The gas enters the ordered array at the bottdm at about 9820C (18000 F) and exits the ordered array at the top at a temperature slightly higher than the particulate solids entering the array. The pressure is about 27.6 bar gauge (400 psig). In the ordered array, the particulate solids are fluidized by the upflowing reducing gas and the hydrocarbon liquid is stripped off the particulate solids. The particulate solids then pass downwardly into the lower zone for combustion and gasification of the carbon deposits.

Claims

1. A process for contacting particulate solids with a gas within an ordered array packing zone comprising: (a) passing particulate solids through the ordered array packing zone having multiple rows of stationary, parallel members providing a void volume ranging from 20 to 80%; (b) passing a gas through said ordered array packing zone to fluidize said particulate solids and to provide intimate contact between the gas and the solids; and (c) maintaining a hindered mixing of the solids and gas within the ordered array packing zone to provide a temperature difference of at least 11.1 OC (200 F) across the packing zone.

2. A process as claimed in claim 1, wherein the particulate solids are passed downward through the ordered array packing zone and the gas is passed upward, counter-current to said solids, through the ordered array packing zone.

3. A process as claimed in claim 1, wherein the particulate solids are passed upward through the ordered array packing zone and the gas is passed upward, co-current with said solids, through the ordered array packing zone.

4. A process as claimed in any of claims 1 to 3, wherein the particulate solids have a diameter of at least 0.051 mm (0.002 inches) and the superficial velocity of the gas ranges from 3.05 to 152 cm/sec (0.1 to 5.0 ft/sec.).

5. A process as claimed in any of claims 1 to 4, wherein the particulate solids enter the ordered array packing zone at a temperature of 454 to 7600C (850 to 14000 F) and the gas enters through the packing zone at a temperature of 538 to 10280C (1000 to 19000F).

6. A process as claimed in claim 5, wherein the particulate solids have thereon a hydrocarbon liquid and the flowing gas heats the solids and strips the liquid therefrom.

7. A process according to any of the claims 1 to 6, wherein the rows of the members of the ordered array packing zone are arranged at an angle of rotation between them of 0 to 900.

8. A process according to any of claims 1 to 7, wherein the members extend completely across the packing zone.

9. A process according to any of claims 1 to 8, wherein the shape of the members is a circle, a square, a diamond, a rectangle, or a triangle.

10. A process according to any of claims 1 to 9, wherein the members are solid, hollow, have a roughened-surface or are finned.

11. A process for contacting particulate solids with a gas within an ordered array packing zone, comprising: (a) passing particulate solids having a diameter of at least 0.051 mm (0.002 inches) downward through the ordered array packing zone having multiple rows of stationary, parallel members providing a void volume ranging from 20 to 80%; (b) passing a gas upwardly, countercurrent to the particulate solids, through the ordered array packing zone at a superficial velocity ranging from 3.05 to 152 cm/sec (0.1 to 5.0 ft/sec) to fluidize the solids and provide intimate contact with said solids; and (c) maintaining hindered mixing of the solids and gas within the ordered array packing zone to provide a temperature difference of at least 11.1 0C (200 F) across the packing zone.

12. A process according to claim 11, wherein the particulate solids enter said ordered array packing zone at a temperature of 454 to 7600C (850 to 14000 F) and the gas enters the packing zone at a temperature of 538 to 1 0380C (1000 to 1 9000F).

13. A process as claimed in claim 11 or 12, wherein the rows of the members of the ordered array packing zone are arranged at an angle of rotation between them of 0 to 900.

14. A process according to any of claims 11 to 13, wherein the shape of the members is a circle, a square, a diamond, a rectangle, or a triangle.

1 5. A process according to any of claims 11 to 14, wherein the members are solid, hollow, have a roughened-surfaced or are finned.

16. A process according to any of claims 1 to 1 5, wherein the solids are catalytic and absorptive.

17. A process according to any of claims 1 to 15, wherein the solids are non-catalytic and nonabsorptive.

18. A process according to any of claims 1 to 15, wherein the solids are catalytic and nonabsorptive.

19. A process according to any of claims 1 to 15, wherein the solids are non-catalytic and absorptive.

20. A reactor vessel for contacting fluids with particulate solids, comprising: (a) an upper zone for containing a fluidized bed of particulate solids; (b) a lower zone for containing a fluidized bed of particulate solids; and (c) an intermediate packing zone comprising an ordered array of stationary, parallel members separating said upper and lower zones.

21. A reactor as claimed in claim 20, wherein said ordered array comprises at least two rows of spaced, self-supporting horizontal members.

22. A reactor as claimed in claim 20 or 21, wherein the members in each row have different horizontal spacing between the adjacent members.

23. A reactor as claimed in any of claims 20 to 22, wherein the rows of the members of the ordered array are arranged at an angle of rotation between them of 0 to 90".

24. A reactor as claimed in any of claims 20 to 23, wherein the members in each adjacent row have different diameters.

25. A reactor as claimed in any of claims 20 to 24, wherein the ordered array comprises at least three rows of rods and the vertical spacing is varied between adjacent rows of rods.

26. A reactor as claimed in any of claims 20 to 25, wherein the adjacent rows of members are separated by vertical spacers.

27. A reactor as claimed in any of claims 20 to 26, wherein the void volume of the ordered array ranges from 20 to 80%.

28. A reactor as claimed in any of claims 20 to 27, wherein the ordered array contains a catalytic material.

29. A reactor as claimed in claim 28, wherein the catalytic material comprises a coating of at least a portion of the horizontal members of the ordered array.

30. A reactor as claimed in any of claims 20 to 29, wherein particulate solids from the upper zone descend downwardly through the ordered array while the gas passes from the lower zone upward, countercurrent to said solids through the ordered array to fluidize the solids and provide intimate contact between the gas and solids therein.

31. A reactor as claimed in any of claims 20 to 29, wherein particulate solids pass from the lower zone upwardly through the ordered array, and a gas passes upward to the upper zone, co-current with the flow of solids, through the ordered array to fluidize the solids therein and to provide intimate contact therewith.

32. A reactor as claimed in any of claims 20 to 31, wherein the reactor internal pressure is from 0 to 69 bar gauge (0 to 1000 psig) and the ordered array temperature is from 454 to 1 0380C (from 850 to 19000F).

33. A process as claimed in claim 1, substantially as hereinbefore described with reference to the Example.

34. A reactor as claimed in claim 20, substantially as hereinbefore described with reference to the Example and/or the accompanying drawings.