US3000364A - Reactor with superheater coil encircling heat carrier lift pipe - Google Patents

Description

Sept. 19, 1961 A. B. STEEVER 3,000,364 REACTOR WITH SUPERHEATER con. ENCIRCLING HEAT CARRIER LIFT PIPE Filed Jan. 30, 1957 3 Sheets-Sheet 1 27 J I- i 32 T /0 E 93 JNVENTOR. ANDREW a. STEEVER ATTORNEY Sept. 19, 1961 A. BQSTEEVER REACTOR WITH SUPERE-IEATER COIL ENCIRC LING HEAT CARRIER LIFT PIPE 3 Sheets-Sheet 2 Filed Jan. 30, 1957 INVENTOR.

ANDREW B. STEEVER ATTORNEY Sept. 19, 1961 A. B.'STEEVER 3,000,354

REACTOR WITH SUPERHEATER COIL ENCIRCLING HEAT CARRIER LIFT PIPE Filed Jan. 30, 1957 3 Sheets-Sheet 3 INVENTOR.

ANDREW B. STEEVER BY ATTOR NEY United States Patent 3,000,364 REACTOR WITH SUPERIIEATER COIL EN CIR- CLING HEAT CARRIER LIFT PIPE Andrew B. Steever, Old Greenwich, Conn., assignor to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Jan. 30, 1957, Ser. No. 637,113 2 Claims. (Cl. 122-4) This invention relates to vapor superheaters and, more particularly, to a novel superheater acting as a thermal protector for a heat carrier lift pipe in high temperature heat exchange apparatus.

In certain types of processing apparatus involving heat exchange and the use of steam as a process reactant, a steam lift pipe is used to transport a solid, particulate heat carrier from a lower relatively highly heated reaction zone to an upper relatively cooler reaction zone wherein the heat carrier gives up heat for a stage of the process. As the lift pipe may be subjected to high heating from the temperatures developed in the processing apparatus, it is desirable to protect the lift pipe from any deleterious effects of elevated temperatures and pressures.

In accordance with the present invention, such heat protection for the lift pipe is provided by jacketing the lift pipe with a vapor or steam superheater supplied with saturated vapor at a pressure of the order of that within the lift pipe so that there is, at the most, only a low pressure difierential between the lift pipe and the superheater. This inhibits any damage to the lift pipe due to pressure difierentials. At the same time, the vapor flowing through the superheater absorbs the process heat which otherwise would be absorbed by the lift pipe. The superheater supplies superheated vapor or steam for the process reactions.

Preferably, the superheater is in the form of a spiral or helical coil surrounding the lift pipe for at least that portion of its length which is in the zone of highest temperature, the superheater coil preferably being supported by the lift pipe.

While the invention is applicable to any type of high temperature processing apparatus, it will, by way of example only, be described as incorporated in the hydrocracking and carbon-gasifying apparatus forming the subject matter of the copending application of T. S. Sprague, Serial No. 637,133, filed January 30, 1957, and now Patent No. 2,959,158. In such processing apparatus, a pressure vessel is divided into three separate reaction zones. In the lowest zone, carbon deposited on a solid heat carrier, which latter is in a fluidized state, is partially reacted with steam and oxygen to form CO and H This exothermic reaction also supplies the heat required for the cracking operation, raising the temperature of the heat carrier. The fluidized heat carrier, at the elevated temperature of, for example, 1800" F., is transported from the lower to the upper zone through a steam lift pipe. The upper zone has present therein gases from the lower zone, which have filtered upwardly through a Raschig ring packing in the intermediate or middle zone, and superheated vapor sprayed thereinto. The hydrocarbon feedstock, together with recycled oil, is sprayed into the upper zone, wherein it is cracked into distillates which are drawn out of the top of the vessel together with the other product gases.

In the cracking process, the heat carrier gives up the sensible heat above the substantially 1000 F. temperature of the upper zone, and is left with a deposit of carbon residue. The cooled heat carrier then gradually drains downwardly through the Raschig ring packing countercurrent to the rising synthesis gas produced in the lower zone. In passing from the relatively cooler upper end of the intermediate zone downwardly to the relatively hotter bottom end thereof, the heat carrier has essentially all of its adsorbed hydrocarbons stripped therefrom; This results in the production of very high gasoline yields from a given quantity of feedstock, as well as production of high B.t.u. fuel gas.

The superheater of the invention comprises a helical coil embracing the portion of the lift pipe disposed in-the lower zone, and supported on the lift pipe. Saturated steam is supplied to the lower end of the superheater coil by means of an inlet pipe having the greater part of its length embedded within a refractory lining of the lower zone. superheated steam from the upper end of the superheater flows through a superheated steam line, embedded in a refractory lining of the intermediate and upper zones, to an annular spray ring at the upper end of the upper zone, where the superheated steam is discharged into the upper zone as a process reactant.

For an understanding of the invention principles, ref erence is made to the following description of typical em bodiments thereof as illustrated in the accompanying drawings. In the drawings: i

FIG. 1 is an axial sectional view through an apparatus embodying the invention;

, FIG. 2 is an enlarged axial sectional view of the upper end of the upper zone of the reaction chamber;

FIG. 3 is an enlarged axial sectional view of one form of support for the Raschig rings; and

FIG. 4 is an enlarged axial sectional view of the lower part of the lower zone of the reaction chamber.

Referring to the drawing, the invention is illustrated as embodied in heat exchange apparatus 10 comprising means, including a circumferential row of generally upright or vertical liquid conducting tubes 20, forming a sealed wall of a refractory-lined combustion or reaction chamber 30. A pressure-tight casing 40 surrounds the wall of the combustion chamber and forms therewith'an interposed annulus space 50. In a manner, and by means, described more fully hereinafter, combustible reactants are introduced into chamber 30 for combustion and reaction therein to produce high temperature gaseous products of combustion or reaction.

Liquid, such as Water, is supplied to tubes 20 from an annular lower header 21 having a liquid make-up inlet 22 and connected by supply conduits 23 to downcomers' 24 connected to the liquid space of a liquid-vapor drum 25 near the upper end of apparatus 10. Means are pro vided for maintaining an incombustible fluid in the gaseous state in annulus space 50 at a pressure in excess of the pressure in chamber 30 to inhibit leakage of the reactants or reaction products from chamber 30 through wall 20 into annulus 50. The incombustible fluid in the gaseous state may be vapor or steam supplied from drum 25, or may be an inert gas such as nitrogen. The vapor'or steam may be delivered to drum 25 for separation therein from the liquid by means of risers 26 connected to an upper annular header 27 interconnecting the upper ends of tubes 20. A vapor supply conduit 28 connects the vapor space of drum 25 to the interior of casing 40.

In the exemplary embodiment of the invention illus-i trated in the drawings, chamber 30 and casing 40 are preferably circular, and the apparatus 10, which has a height which is a relatively large multiple of its diameter, is designed for use in a combined hydrooracking and synthesis gas producing process. For carrying out this process, chamber 30 is divided into three superposed reaction zones, including an upper zone 30-1 comprising substantially the upper half of the chamber, and intermediate and lower zones 30-2 and 30-3 sharing the lower half of the chamber. Intermediate zone 30-2 comprises a packing 31 of Raschig rings extending upwardly from screen means 35 in turn supported from wall tubes 20. Screen means 35, described more fully hereinafter, sepae rates the intermediate and lower zones of chamber 30.

Lower zone 30-3 is substantially filled with a solid heat carrier 32 in the fluidized state, such as, for example 20 mesh alumina. Carbon carried by the heat carrier 32 is partially reacted, in the lower zone, with steam and oxygen, introduced into this. zone, to form CO and H This exothermic reaction elevatesthetemperature of the heat carrier to a relatively high value, such as l800 F., required for the hydrocracking operation. The high temperature, heat carrier is then transported to the upper zone 30-1 through a steam lift pipe 55 extending axially of chamber 30 to just above Raschig ring packing 31, pipe 55 being supported from screen means 35. The heat carrier preferably fills the upper zone 30-1 to a level well over half the height. of this zone. .In the upper zone 30-1, heat carrier 32 is in intimate contact with the synthesis gas from the lower zone, which filters upwardly through the Raschig ring packing of, intermediate zone 30-2, and with hydrocarbon feed stock and recycle oil sprayed into the upper zone. The reactants sprayed into upper zone 30-1 are cracked. into distillates which pass through an, overhead outlet or gas ofitake; together Withthe synthesis gas. In the cracking process, the heat carrier gives up its sensible heat above the 1.000 F. temperature of upper zone 30-1, and is left with a carbon residue deposited thereon. The spent heat. carrier drains down through Raschig ring packing 31 countercurrent to the rising synthesis gas. In this passage to the lower zone 30-3, the heat carrier 32 is essentially completely stripped of all adsorbed hydrocarbons, resulting in very high gasoline yields from a given quantity of feed stock. The synthesis gas reaction is essentially completed in the presence of superheated steam sprayed into the upper zone.

An excess of carbon, amounting to about 15-25% by weight of the heat carrier, ismaintained in chamber 30 at. all times. Thecarbon gasification rate in lower zone 3.0-1. is adjusted by adjusting the, oxygen flow rate, and the 1000 F. temperature of, upper zone 30-3 is maintained or regulated by adjusting the rate of heat carrier circulation.

Apparatus is supported in the upright position by a. suitable structural framework (not shown) including support brackets 11 welded or otherwise secured to the outer surface of casing'40. Other brackets 12 adjacent the upper end of casing 40 support a rigging steel framework 13 including brackets 14' andsupport drum 25.

It. will be noted from the above description that reactants are introduced into both the upper zone 30-1 and, the lower zone 30-3 of chamber 30, and the gaseous reaction products are withdrawn from the upper zone. For this reason, pressure casing 40, which may, for example, be a metal shell designed for 500 p.s.i. pressure in accordance with the ASME code for unfired pressure vessels, has openings in both its upper and lower ends.

The upper end of vessel 40 is closed by a hemispherical head 45 having a flange, removably secured to a flange on the upper end of casing 40, and a tubular axial extension 41 with a flange 42 on its outer end. A seal 43 iswelded around the inside of the joint between casing 40 and head 45. The hemispherical lower end of casing 40 has a relatively large diameter axial opening in which is Welded a tubular, nozzle-like extension 44 having a flange 46 on its outer end.

The means, including tubes 20, defining reaction chamber 30 are supported on the lower end of casing 40. The support means includes an annular, substantially boxshape shelf or bracket 47 formed of a pair of angles preferably welded at their outer ends to the inner surface of-casing 40. A tubular sealing diaphragm 48 extends between the joined ends of the angles and casing 40 just outwardly of extension 44. Bracket of shelf 47 supports lower header 21, the connections 22 and 23 to the header extending through bracket 47. A'tubular sleeve 51 extends in telescoped, slightly spaced relation through extension 44 terminating flush with the lower end of the 4 latter, and has a radial flange 52 on its upper end welded to header 21 and braced by gussets 53. Flange 52 supports the refractory lining of reaction chamber 30, which covers the inner surfaces of wall tubes 20.

The inter-tube spaces between tubes 20 are sealed by elongated metal bars welded along their edges to adjacent tubes, and also by welds between adjacent tubes.

In order to prevent collapse of the tube wall should the pressure differential between chamber 30 and annulus space 50 become excessive, tubes 20 are braced by stifiener rings 57 embracing the tube wall at spaced intervals, such as 30" for example, along the tube wall. Each tube 20. has a pad 58 welded thereto and tapped to receive bolts securing the tube to the H-shape stifiener rings 5.7. Insurance against a collapse due to excessive pressure differentials is provided also by a connection 61 connecting the interior of head 45to a charge pipe 15 for the heat carrier 32. Charge pipe 15 extends, in a manner not shown in detail, through head 45 and into reaction chamber 30, thepipe extending through a thermal, sleeve 16 including anexpansion joint 17. Connection 61 thus interconnects annulus space 50 and chamber 30, andthis connection contains a pressure relief valve 60 operable, upon attainment of a predetermined pressure differential (such as, for example, 50 p.s.i.) between chamber 30 and space 50, to open and equalize the pres.- sures in chamber 30 and space 50.

The refractory lining of chamber 30 is supported on flange 52 and on supports secured to tubes 20. In the intermediate zone 30-2 and lower zone 30-3, the lining comprises a 4" thick outer section 33 of insulating firebrick. shapes. against tubes 20 and a 4" thick inner section 34 of firebrick shapes having good resistance to abrasion and suitable for usein strongly reducing atmospheres. The lining of the upper zone 30-1 comprises a 4" thick outer section 36 of lightweight insulating concrete shapes, and a 1'' thick inner section 37 of high strength abrasion resistant cast refractory reinforced by a steel mesh (not shown) secured to studs 38 on tubes 20.

In carrying out the process to which the apparatus 10 is particularly adaptable, there is a high gas pressure drop longitudinally of the reaction chamber, combined with a dust laden atmosphere. For this reason, metal vapor stops 62 are disposed at regularly spaced intervals along the full height of the reaction chamber. These stops are continuously welded to wall tubes 20 to. form gas tight barriers in the refractory lining of chamber 30. In the intermediate and lower zones, stops 62 act also as supports for the refractory lining, being braced by gussets 63. In the upper zone 30-"1, elements 62 act only as vapor stops. Horizontal expansion joints beneath each vapor stop are packed with a mineral wool 64 retaining its resilience at temperatures well above the temperature of the lower zone 30-3. To simplify the illustration, vapor stops62 are not illustrated in FIGS. 1 and 4.

The upper end of reaction. chamber 30 is closed by a metal rupture diaphragm 65 having a refractory lining, on its inner surface, of the same type as the lining 3637 of upper zone 30-1. Diaphragm 65 is sealed at its outer edge to an. annular ring 66 welded to the upper inner quadrant of header 27. The inner margin of diaphragm 65 is sealingly'connected to the lower end of an expansion joint 67 whose upper end is connected to a thermal sleeve; 68 surrounding a gas ofitake pipe 70.

An insulating liner 71 is disposed between sleeve 68 and pipe 70, and the-sleeve and pipe have radial flanges on their outer ends superposed on each other and on flange 42; of. extension 41. Thereby, the sleeve and pipe are, clamped. in position on flange 42 by a connection member 72 having a flangesecured to flange 42. Member 72' has'an insulating liner 73 on its inner surfaces as does also a second flanged connection member 74 secured. to member 72.

A housing-76 for a soot blower 75 is mounted on member 74, and the lower end of pipe 70 has braces '77 mounted thereon and positioning a guide sleeve 78 for the soot blowerr Thermal. protection for head 45, from the hot gases flowing through oiftake pipe 70, is further provided by a bathe 80 which. directs the incombustible fluid under pressure and in the gaseous state supplied to annulus space 50 to sweep over the inner surface of head 45, around sleeve 68 and joint 67, and over rupture diaphragm 65. Baflle 80 comprises an annular frustoconical base 81 secured to casing 40 joint below steam inlet 28, and a cylindrical and axial upper part or sleeve 82 surrounding the gas ofltake parts and extending to near the top of head 45. Thus, the saturated steam, or other incombustible fluid in the gaseous state, supplied through inlet 28 first sweeps upwardly over the inner surface of head 45, then down through bafie section 82 around sleeve 68 and joint 67, then outwardly between baflie base 81 and diaphragm 65, and thence into annulus space 50.

Head 45 is provided with a normally closed access opening 83. However, for access to combustion or reaction chamber 30, the entire head 45 and its supported parts are removable with the assistance of suitable rigging on framework 13. Base 81 of baffle 80 has a normally closed manhole 84, aligned with a normally closed manhole 86 in diaphragm 65, the cover 87 of this latter manhole having its inner surface refractory-lined in the same manner as the diaphragm 65.

The feedstock and re-cycled oil are introduced into upper zone 30-1 of reaction chamber 30 by feed lines 85 extending through thermal sleeves 88 in head 45 and diaphragm 65. In chamber 30, these feed lines extend through protective sleeves 89. In the illustrated embodiment of the invention, three feed lines 85 are provided each terminating at a difierent level of zone 30-1 for uniform distribution of the hydrocarobn reactants.

superheated steam is supplied to the upper reaction zone 301 by the invention superheater 90. This superheater comprises a helical coil embracing lift pipe 55 in lower zone 30-3, and thus acting as a thermal protector for the lift pipe. Superheater 90 is supported by lift pipe 55 by means of a shelf 91 secured to pipe 55. The superheater is designed to deliver approximately 1000 lbs./hr. of superheated steam at 1200 F. Saturated steam at a pressure of, for example, 450 p.s.i., is supplied to the lower end of superheater 90 by a supply line 92 entering through the lower end of casing 40 and extending between bracket 47 and sleeve 51. Line 92 is encased in inner refractory lining section 34 through which it extends for some distance upwardly until it is bent radially inwardly to connect with the lower end of superheater 90.

Superheater 90 terminates just below screen 35, and the superheated steam flows through a line 93 from the upper end of the superheater coil. Line 93 extends radially outwardly and upwardly (FIG. 3) into lining section 34 and thence upwardly through this lining section and between lining sections 36 and 37 to an annular spray ring 95 at the upper end of zone 30-1.

Lift pipe 55 is supported solely from the screen support for Raschig rings 31. This allows all the reactant introduction means for lower zone 30-3 to be mounted through a removable plug 100 closing the lower end of reaction chamber 30 and casing 40. In the screen arrangement shown in FIGS. 1 and 3, the support screen 35 comprises a perforated annular frusto-conical support plate 35 carried by radial arms or brackets 94 secured, at their outer ends, to wall tubes 20 and, at their inner ends, to a ring 96 embracing pipe 55. The pipe is supported on ring 96 by means of brackets 97.

The removable plug" 100 includes an annular plate 105 removably secured to flange 46 of lower tubular extension 44 and sealing abutting the lower end of sleeve 51 to separate chamber 30 from annulus space 50. A flanged tubular sleeve 106 is mounted axially of plate andhas'an annular closure plate 107 secured to its lower outer end. Plate 105 supports a cylinder or annular plug 108 of built up lightweight refractory shapes, this cylinder fitting closely within sleeve 51 and having a layer 111 of plastic refractorymaterial on its upper end substantially flush with the upper end of sleeve 51. Cylinder 108 has an axial opening 112 forming a continuation of sleeve 106 and having a flared upper opening through refractory layer 111. The lower end of lift pipe 55 has a loose fit in passage 112.

An oxygen and steam mixture is introduced into lower zone 30-3 by inlet pipes 113 connected to a spray ring located just below superheater 90. Pipes 113 extend through jacket sleeves 114 in plug 100, and sleeves 114 are supplied with steam from annulus space 50. For this purpose, space '50 is provided with an outlet pipe 116 connected through a suitable pressure reducing valve and a header to jacket sleeves 114. The reducing valve and header have not been shown, in order to simplify the drawing, and the connecting means is schematically indicated by broken line 117. Additional steam, from a separate source of supply, is delivered to zone 30-3 by pipes 118, connected to an intermediate spray ring 115, and pipes 119, connected to lower spray ring 120.

Lift steam for pipe 55 is supplied by a conduit 121 connected through a sealing nipple 122 in plate 107. Conduit 121 also supplies steam for operating a piston type gate valve controlling the opening 123 in pipe 55 for entry of the heat carrier 32 thereinto.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In high temperature processing apparatus utilizing a superheated fluid as a reactant, a relatively elongated reaction chamber having superposed upper and lower zones with a gas outlet from said upper zone, said lower zone having a high temperature therein, a vertically arranged transfer pipe in said chamber for transferring a solid particulate heat carrier from said lower to said upper zone and having at least a lower portion thereof subjected to said high temperature, means for protecting at least said lower portion of said transfer pipe from the effects of such relatively high temperature comprising a tubular coil in contact with and jacketing the exterior surface of said transfer pipe lower portion; means for introducing a fluid into said tubular coil for superheating thereof by heat absorption from the surrounding high temperature zone, and means for withdrawing the superheated fluid from said tubular coil and discharging the superheated fluid into said upper zone as a reactant.

2. In high temperature processing apparatus utilizing a superheated fluid as a reactant, a relatively elongated reaction chamber having superposed upper and lower zones with a gas outlet from said upper zone, said lower zone having a high temperature therein, a vertically arranged transfer pipe in said chamber for transferring a solid particulate heat carrier from said lower to said upper zone and having at least a lower portion thereof subjected to said high temperature, jacketing means for protecting at least said lower portion of said transfer pipe from the effects of such relatively high temperature comprising a tubular coil having the convolutions thereof in tube to tube contact and in contact with the exterior surface of said transfer pipe lower portion, means for introducing a fluid into said tubular coil for superheating thereof by heat absorption from the surrounding high temperature zone, and means for withdrawing the superheated fluid from said tubular coil and discharging the superheated fluid into the upper portion of said upper zone as a reactant.

(References on following page) References Cited. in the file of this patent UNITED STATES PATENTS McCollum Apr. 17,v 1945 Gunness Oct. 14,1947 5 Arveson Nov. '25, 1947 Watson Aug.'31, 1948 Sensel et. a1. Mar. 28, 1950

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