US2595384A - Grid seal for fluidized solids contacting systems - Google Patents

Description

y 6, 1952 J. H. JOHNSEN ET AL 2,595,384

A GRID SEAL FOR FLUIDIZED SOLIDS CONTACTING SYSTEMS I Filed Dec. 7, 1950 FIG. 2

` FIG. 3

INVENTOR: JOHN H. JOHNSEN ENT CATALYST ATTORNEY:

ATE HSER JR.

Patented May 6, 1952 cim) SEAL ,FoR F ID Z SOL DS CONTACTING SYSTEMS John H. Johnsen, Hammond, Ind., and Nate H. Snyder, Jr., San Antonio, Tex., assignors to Standard Oil Company,` Chicago, III., a corporation ;of Indiana Application December 7, 1950, Serial .Ne. 19.9676

1 This *invention relates to an improved grid seal for fluidized solids contacting systems and it pertains more particularly to structure for preventing the by-passing of gases in fluidizedsolids contacting systems which operate at high temperatures.

The invention -is particularly applicable to `regenerators of fluid catalytic cracking systems of the type illustrated, for example, in U. S. 2,457,255 (although steam instead of oxygen may be employed 'for effecting the stripping). It is important that the grid at the base of the regenerator distribute the incoming regeneraion gas-catalyst suspension uniformly across substantially the entire regenerator cross sectional area and since supplemental air is usually introduced below the grid it is important that this supplemental 'air be likewise uniformly distributed. Heretofore much difiiculty has been encountered in effect'ng a seal between the distributor grid and thereactor walls. The distributor grid may expand or contract several inches during start-up and shut-down periods while there is little or no change in the dimensions of the outer vessel wall. Also, there are tendencies toward deformation due to differential expansion, and the erosive effect of the fluidized solids tends to aggravate the problem ot ;preventing Icy-passing of air and regeneration gas around the edges of the grid. such lay-passing of air-in turn -results in channeling along the reactor wall and afterburning in the :upper part of the regenerator which-'is' plate which may be caused by differential expension. Other objects will be apparent as the detailed description of the invention proceeds.

The grid seal of this invention is provided by metal plates of substantially the same curvature as the periphery of grid sections, said plates having a rounded lower surface for contacting the upper surface of a ledge which extends inwardly from the reactor wall underneath the Peripheral edges of the grid sections. The plates are held close to the peripheral edges of the grid sections by holders cooperatng with brackets on the grid section so that the rounded lower edges of the plates may bear against and slide upon the inwardly extending ledge while the outer surfaces of the grid plate may move upwardly and down- 3 Claims. (CI. 23-28@ -,2 wardly along the vertical surfaces o f-the eurved plates while said plates `remain in contact with the vertical ledge. The seal -is thu effected between 'the rounded lower 'edges of the -a-rcuate plates and the in-wardly extendirg ledge and also between the vertical inner sides of the arcuate plates and the periphery of the grid sections. such a seal construction has been -found to be'- remarkably effective in commercial fluid catalytic cracking regenerators as will be -polnted out in the following detailed description. i

The invention -will be more readily un'derstood from the following description of -a specific example read in conjunctlon with the accompany--- ing drawingswhich forma part of thls specification and in which-z Figura l is a diagrammatic sectional view of a conventional catalytic crackin regenerator l-l-.-'

lustrating the position of the improved grid seal;

Figure 2 is an isometrie detailed sketeh showing the structure of the grid seal in greater detail; and

Figura 3 is a detailed section showingthe slideable mounting of the seal plate against the periphery of a grid section.

The regenerator o of afiuid catalytic cracking system may be about 40 feet in diameter and about 50 feet in height. The lower section l l of the regenerator -vessel -is usually conieal or' hemispherlcal irrshape. Spent Catalyst suspended ;in a part ofzthe regeneration air stream is introduced intothe lower section through line 12 and supplemental `air may :be lntroduced into the bottom section through 'line !3. 'Regenerated catalyst is ;withdrawn from the regenerator through-standpipe !4, the upper end of which extends above distributor grid !5. This distributor grid may be supported -on rings IE and ll which in turn are mounted on structural supports 18 and [9. The grid !5 maybe in the ;form of a steel plate about 1 or 2 inches in thickess provided with apertures 20 -for uniformly -distributlng the introduced Catalyst suspension across substantially the entire cross sectiona l area of the regeneratorj The outer edges of the grid protrude over a ledge -2| *which extends inwardl'y from the reactor wall. Heretofore, it 'has been the practice to allow about inch clearance between the Iedge and the grid 'but much difficulty has been encountered in preventing short crcuiting of regeneration gas ,such as air around t edg s o t e such short ci cuitin not only detracts from regenerating eiiiciency but it causes channeling and afterburning in the upper part of the regenerator, which etterburning often ruins the cyclone separators 22, which are conventionally employed in the upper part of the regeneration chambers for separating solids from gases introduced thereto from inlet 23, the separated solids being returned to the dense phase by dip leg 24 and the gases then being vented from the top of the regenerator through line 25. While a single cyclone is shown in the drawing, it will be understood that a plurality of cyclones are usually employed and often 2 or 3 stages of cyclone separation are used instead of the single stage illustrated.

In accordance with this invention, an arcuate steel plate 26 surrounds the outer edge of each grid section and rests on ledge 2 I, plate 26 being held by bolt 2'l to brackets 28 with either the plate or the bracket being slotted to provide for vertical movement of the periphery of the grid with respect to the plate which is held close to: the perpnery of the grid in aii positions tnereof.

The structure will be more readily apparent by reference to Fig. 2 which shows in greater detail the wall structure, grid section and the improved rid seal of this invention. The outer reactor wall 29 is fabricated from steel. Inside the outer steel casing is a layer of insulating cement or concrete 30. When this insulating concrete has set, a steel mesh lining 3l is placed on the inner surface of the walls, this steel mesh preierably being in the form of hexagonal steel grating which, when placed on the concave surfaces,

provides a secure anchor for refractory cement which is applied through the steel mesh to form a so-called gunited lining 32. Iron bars 33 are welded at 34 and 35 to the steel mesh 3! bent in the form of angular brackets at spaced points around the periphery of the lower part of the vessel andserve as reenforcement for the inwardly extending ledge 21 which is preferably a refractory concrete and which has a substantially flat horizontal upper surface 36.

A vertical arcuate plate 26, which in this case is inch by 9 inch steel plate rolled to grid plate curvature, surrounds the outer peripheral edge of grid section !5. Plate 26 is rounded at its lower end 42 which rests on the top surface 36 of ledge 2| so that plate 26 may slide inwardly and outwardly on the ledge as the grid plate expands and contracts. Angle iron brackets 28 are welded at sp aced intervals around the outer edge-of the grid. They are provided with vertical'slotsas for re ceiving -a bolt or other holder 21 which extends inwar dly through or from plate 26. Alternatively or in agdition, vertical Slots a may be provided in plates26. The bolt or holder .2'1`

holds the plate- 26 in sliding engagement with the outer periphery of the grid plate section !5 so that the outer edges of the grid plate may warp or move up or down and still be substantially sealed by the close proximity thereto of an arcuate plate 26 which in turn is sealed at its lower Since the grid plates are around the entire periphery of the-grid. The term grid section" as employed herein is intended 'to mean either separate or integral grid sections and the arcuate plates for the grid sections may likewise be separate or integral with adjacent plate sections.

In the example hereinabove described, the grid plate was separately supported by rings 16 and H so that ledge 2| did not carry the actual weight of the grid. In some cases, however, it may be feasible to support the grid on the inwardly extending peripheral ledges using an annular steel ring instead of refractory cement for the upper surface thereof. 'Even in this case, any warping of the grid would lead to by-passing of gases around the edges thereof and a structure of the type hereinabove described will provide a remarkably more effective seal.

Prior 'to the installation of the grid seal hereinabove described in a fluid catalytic cracking regenerator, great diificulty was encountered because of afterburning in said regenerator and ineifective operation thereof. Inspection after.. a shut-down showed that erosion of the refractory ledge under the grid had occurred to such a'n extent that the space between the grid and the remainder of the ledge wasapproximately one inch in many places. Thereafter the above described grid seal was installed in this regenerator" and it was found to be remarkably effective in eliminating the by-passing of gases around the grid. Afterburning was no longer encountered and the regenerator functioned with much greater efficiency.

After the installation of said grid seal, the conf version in this catalytic cracking unit was unusually high and the gasoline yields were higher; than were ever before obtained on the unit.

While a particular example of the invention has been described in considerable detail, many alternatives and modifications will be apparentto those skilled in the art from the above description. v

We claim: V v

1. A grid seal for a fluidized solids Contacting 4 system whereir grid plate sections are supported with their outer edges protruding above a periph eral ledge extending inwardly from the innerwa-ll; of a Contacting vessel, which grid seal omprises a vertical arcuate plate substantialy conforming.i with the outer edges of each grid section, A plate having a rounded lower surface for contacting the upper surface of the ledge, brackets at the periphery of each grid segment ;and a holder cooperating with said bra'cletsand-said' plate for holding said plate close to the outer edge of the grid section while permltting relative ver tical movement between the plate and the outer edge of the grid section. v I

2. The structure of claim 1 wherin theinner vessel walls and upper surface of the ledge, which 7 are adjacent the outer edges of the grid sections j are of refractory cement held in place by steel mesh. v V I 3. The structure of claim 1 which includes separate grid supports for supporting` th grid sections so that the weight of said grid sections; is not carl-led by said ledge. t

JOHN H. JOHNSEN. 1

NATE H. SNYDER, J

No references cited. i

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