US2520482A - Insulated conduit - Google Patents

Description

Filed May 16, 1946 5 Sheets-Sheet 3 INVENTOR ERA/E57' U TTERBQC/f Patented Aug. 29, `195() INSULATED CGNDUIT Ernest Utterback, New York, N. Y., assigner to Socony-Vacuum Oil Company, Incorporated, a

corporation of New York Application May 16, 1946, Serial No. 670,277

(Cl. 22B-2W) 5 Claims. 1

This invention relates to a conduit for the transfer of high temperature gases and is particularly adapted to the construction of conduits for transferring high temperature gases from a zone of high temperature treatment to a Zone of low temperature treatment.

it is often desirable to transfer gaseous material from a high temperature region to a low temperature region, thus requiring a construction which is reasonably gas tight and equipped with connections which will inhibit loss of gases from the predetermined path. The thermal stresses induced in metals between two regions of widely varying temperature and the thermal expansions involved in heating the apparatus up to working temperature introduce serious construction problems. IThe present invention provides means for confining a transferredgas within a predetermined path and is adapted for use with connections which permit adjustment for thermally induced stresses and yet inhibit serious losses of the gases being handled.

The nature of the problems involved and the manner in which they are met by the present invention is well `illustrated by apparatus for conversion of higher boiling hydrocarbons to ethylene by reaction for a very short time, say 0.2 second at high temperatures on the order of 1560" F. and above. To obtain the necessary short reaction time the high temperature reaction mixture must be promptly quenched to a low temperature. One advantageous system for accomplishing this high temperature short time reaction is to pass the charge hydrocarbons in direct contact with a bed of highlyheated granular solid and then pass the hot reaction mixture through a bed of relatively cold granular solid. This requires two contacting chambers `connected by a transfer line which will confine the hot gaseous mixture within the predetermined path. Because of the high temperature diierential between the two contacting zones and the wide range over which the apparatus must be heated on starting up, a rigid connection of the transfer lines to both contacting vessels is impractical. .A sliding connection may be made between the transfer line and one of the contacting chambers, preferably the heating chamber. Since the sliding connection is not completely gas-proof, a pressuring medium must be supplied about the sliding connection to prevent loss of the vapor under treatment. That pressuring medium is coniined within an outer shell surrounding the contacting chamber and precautions must be taken against leakage of the pressure medium from the outer shell at the point where it is penetrated by the transfer line which must be mounted for relative movement with respect to the outer shell.

According to the present invention, this result is achieved by providing an inner pipe which serves as the actual transfer line and an outer pipe thereabout which serves to seal the sliding fit between the outer shell and the relatively movable inner pipe. Spacing members are provided in the form of circular webs to maintain the relative coaxial positions of the inner and outer pipes.

These webs are securely fastened at one end of one of the concentric pipes but are free at the other end to permit relative movement of the pipes. The free end must, however, be closely fitted to the adjacent pipe to provide an opening of high pressure drop along the annular space between pipes. This plurality of gaps of high pressure drop serve to keep the leakage of pressuring medium to a minimum and also maintain proper spacing of the pipes. Preferably, the linear distance along each web between the two pipes is made considerably greater than the actual distance between the pipes in order to reduce thermal losses along the webs themselves. Thus, the webs are generally frusto-conical in form and are preferably mounted with the smaller end directed between the zone of highest pressure open to the annular space between the pipes.

Either edge of the webs may be secured to the adjacent pipe wall and, theoretically, the greatest pressure drop along the annular space is provided by having alternate webs secured at their inner and outer edges respectively to produce a labyrinth effect. However, this involves serious difficulties in assembly and, as a practical matter, the webs are generally secured to the same pipe. The nature of the `invention is best understood in connection with specic apparatus for practising the specific process noted above and such a process is described below in connection with the annexed drawings, wherein Figure l is a diagrammatic showing of the relationship of the several elements making up a plant for this purpose;

Figure 2 is a vertical section through a contactor and quencher and the communicating conduit therebetween;

Figure 3 is a section on line 3 3 of Figure 2; and

Figure 4 is a detail view in section of the reactor outlet port.

Referring specifically now to Figure 1, a hot r'eenllll. $01.1@ is heated to a suitable high tem- Acondenser by line 25.

perature in heater' iii and transferred by feed leg il through a steam sealing zone t2 to a reactor i3. A charge for the reaction is introduced by a plurality or inlet tubes Ill depending from ring manifolds i at the top of the reactor. rhe number and spacing of tubes l fl is such as to give unito-ri l spacing of the discharge openings at the bottom ends thereof, depending on the size and shape of the cross-section o1" reactor i3. A typical structure has an internal diameter of the reactor shell (lic in Figure 2) of six feet nine inches with a deecting insert having an outside diameter of two feet. Three concentric rings of tubes I4 contain ll, l@ and 23 tubes, respectively. The charge may advantageously be a liquid oil, mixed with liquid water, to generate the hydrocarbon and steam vapors desired for the reaction. Al ternatively, hydrocarbon and steam vapors may be generated outside the reactor and charged thereto as a vapor phase mixture. Preheating of liquid charge to any desired degree will deu pend upon the heat balance factors involved, such as the desired temperature for granular solids withdrawn from the bottom of reactor i3.

`Within the reactor I3 the charge is passed in direct contact with the highly heated granular solids and is thus rapidly converted to a vapor phase mixture having the temperature desired for the reaction. Upon leaving the contact bed, the reaction mixture is quenched by the injection of water supplied from inlet i6 and is passed by conduit Il to a quencher I8 wherein it is passed through a moving bed o?? relatively cool granular solids for further reduction of temperature. The quenched reaction mixture is transferred by line I9 to a spray condenser 2t from which product vapors are taken overhead byline 2I to a suitable gas plant for purification and recovery of the gaseous products of the reaction. Oil and water from the bottom of condenser 23 are passed to a settler 22 wherein they separate into an upper oil layer which is cooled in heat exchanger 23 before transfer to processing or storage and a lower water layer which is coole-:l in heat exchanger 24 to be recycled in part to the spray If the charge to the reactor is in liquid phase, mvater from the bottom of settler 23 may be used in the charge since contamination of the charge water has no detrimental effect in such operations, the contaminants being either vaporized with the water or deposited on the granular solid from which they may be removed by burning in Vthe heater.

Returning now to the reactor i3, a purge gas such as steam is admitted to the bottom of the reactor at inlet 2e and a pressuring medium, which may also be steam is admitted at inlet 2l to #be used in a manner to be hereinafter described for preventing deposition of carbonaceous substances in the reactor insulation. The granular solids are withdrawn from the bottom of reactor i3 by pipe 28 and are passed through a depressuring pot 29 to an elevator 3B, In general, Solids transferred to the elevator should be "maintained at a temperature which will not damage the elevator or adversely affect its operation. If the outlet temperature of reactor I3 is too high, water may be injected to the solids in depressuring pot 29 or water may be sprayed onto the solids entering the housing of elevator 30, in which case the elevator shaft acts as a stack for the withdrawal of steam so generated. Solids are discharged from the top of elevator 3Q into a feed pipe 3l, passed through a classifier 32 for removal of particles broken down 1.10 ai S126 smaller than that desired and are then fed to heater I!) to again pass through the cycle. In the heater, fuel from inlet 33 is burned in preheated air supplied at 34 to generate a flame in direct Contact with the solid granules and thus heat the latter to the desired degree. Flue gases are withdrawn at 35 and passed to an economizer or stack.

The quencher is an element of a similar cycle of granular solids and wherein the granules serve to cool vaporious reaction mixture from reactor I3 and are then purged by steam admitted at 3B and passed by pipe 31 and depressuring pot 38 to an elevator 39. From the top of elevator 39 the solids are discharged by pipe 49 through a classifier 4I to a hopper 42. Solids are supplied through feed leg 43 to an air preheater 44 wherein they are contacted with air from blower 45 to preheat the same. The preheated air is then transferred by line 4B to inlet 34 of heater Il). Any carbonaceous deposit in the nature of coke or tar laid down on the solids in Vthe quencher I3 will be burned off in heater 44 but a large excess of air is supplied to chamber 44 and the net effect is to cool the solids in chamber '44 whereupon the cold granules are transferred by feed leg 4'! through a steam purging zone 48 to the quencher I8.

As shown in Figure 2, the reactor I3 comprises a reaction shell 5E) within an insulated casing 5I. Granular solids from feed leg II fall into the steam sealing element I2 and form therein a small heap of granular solids. Steam is admitted above the heap of solids from pipe 52 under a pressure greater than that existing in either the heater or the reactor to thus prevent any mixing of vapors from the elements connected by feed leg il. From the steam sealing chamber I2 the solids move downwardly through the bottom portion of feed leg II into the reactor I3 wherein they fall onto a sloping divider insert 53 and are thereby diverted to the contacting region of the reactor, none of which lies directly below the outlet of feed leg Il. Within the shell 5i) the granular solids take the form of a moving bed of granular solids having an upper surface which lies at about the angle of repose about the solids. It may be noted that the flow of gases upwardly through the bed has an effect on the angle of repose of the solids depending upon the gas velocity. As the gas velocity approaches that at which the granular solids would be suspended in the stream of gases, the angle of repose approaches the horizontal, This is an important element in determining how the charge inlets shall. be disposed within the bed as will appear hereinafter.

The charge is admitted by the pipes I4 which extend downwardly through the insulated casing the top of shell to points within the bed of granular solids. The pipes I4 are mounted for vertical movement through stuffing boxes 54 and sealing Han-ges 55 in the top of shell 5i). To obtain uniformity of contact path within the bed of granular solids the several pipes I4 are adjusted to their lower ends at a constant depth below the upper surface of the bed in shell 5d. In the embodiment here shown, the reactor i3 is circular in general outline wherefor the upper surface of dividing insert 53, the upper Surface of the movingl contact bed and the surface along which the outlets of pipe i4 are arranged are generally conical. It will be readily understood that other1 outlines may be adopted for reactor I3 in which case these surfaces `will be of a different nature.

The bed in reactor I3 is considerably deeper than that necessary to accommodate the contacting zone above the discharge of pipes I4. Some of the heavier hydrocarbons may remain on the granular solid for a substantial distance below the pipes I4 before they become fully vaporized. Any vapors, whether formed instantaneously or substantially below the pipes I4 are caused to pass upwardly through the bed and are brought to maximum temperature in `the region above the ends of pipes I4 where the solid has not yet been chilled by direct contact with charge hydrocarbons. A deep bed offers fairly high resistance to the passage of hydrocarbons downwardly, thus encouraging iiow of gases through the path of least resistance to the top of the bed. Additionally, Vprovision is made for an inert gas such as steam to sweep upwardly through the bed. This latter result is achieved by injecting steam or the like below a -plate 5t through orifices 51 in the wall of the divider insert 53. Steam under pressure somewhat in excess of that prevailing in the contacting Zone is admitted to the interior of divider insert 53 by means of pipe 56. The steam pressure inside insert 53 effectively prevents leakage of hydrocarbons to this space thus inhibiting deposition of coky matter from extensive cracking of hydrocarbons inside the insert. A number of feed pipes 59 depend from plate 5B for the withdrawal of granular solids in a uniform manner across the interior of shell 50. Each one of the pipes 59 withdraws solid from a space diverging upwardly therefrom and the greater the numb-er of these pipes, the less will be the volume of dead spaces wherein the granular solids are not flowing. A plate 6U has orifices 6I spaced so that each of the orifices 6I draws equally from two or more pipes 59 thus equalizing the flow among the pipes 59. The symmetrical arrangement of orifices 6I about the center of shell 50 results in uniform withdrawal from these orices by outlet pipe B2. As the granular solid flows from the ends of pipes 59 onto plate 6I) it assumes the form of a large number of heaps below the free space about the pipes 59. The steam discharged through orifices 51 fills this space and penetrates the heaps to flow upwardly through the pipes 59 thus purging the granular solid as it is withdrawn and producing upward flow of a current of inert gas through the moving bed between plate 5B and the top contacting zone thus insuring that all volatile hydrocarbons shall pass i through the high temperature zone at the top of the bed and undergo the desired cracking. This also minimizes the danger of combustible materials being carried from the reactor into the elevator to thus cause a fire hazard.

The space between the insulated casing 5I and the shell 5i! is also placed under an inert gas pressure slightly in excess of the pressure in the contacting zone by admitting steam or the like through inlet 21. The pressure of the steam will be such that steam will flow slowly into the casing 50 from the space thereabout through any opening which might permit leakage. The chance that hydrocarbons will seep out into the insulation or to the space about shell 5S is thus effectively overcome.

A manifold for withdrawal of reactant vapors is provided above the bed of contact material by the top wall of shell 5B and a plate S3 having orifices El! through which the pipes I4 are passed.

The orifices64`actto throttle disengaged vapors rising from the contact bed and thus afford equal iiow into the manifold from the various 'areas above the bed. For example, the orifices E4 may be of such area as to provide a uniform linear velocity of ft. per second through the orifices and the manifold. The manifold is connected to the conduit I1 by a sliding joint comprising a flange 65 at the outlet of the manifold and a collar 66 on an insulated pipe 51 which defines the transfer line between reactor I3 and quencher I8. The water for preliminary quenching may be advantageously admittedatthis point, as by means of a spray 68 facing in the direction of vapor flow. A i

The transfer line between the reactor and the quencher is subject to high thermal stresses and is' therefore advantageously mounted and connected in the manner shown. The collar 66 is slidably mounted on the reactor end of pipe 61 and contacts the latter along a relatively small surface such as integral ring 69` A pair of guides 10 mounted on the flange 65 maintain the face of collar, 66 in contact with flange 65 along the relatively small area of the raised ring 1I. The guides 1U are preferably so formed that they permit some play of the collar 69 from side to side but maintain a fairly firm contact between ring 1I and flange E5. There is thus provided a connection between the manifold and the pipe 61 which permits relative movement of pipe 61 with respect to flange 65 over a considerable distance in any direction without substantial effect upon the nature of the connection. No attempt is made to provide `a vapor-tight connection at this point since `the steampressure imposed between shell 5!) and casing 5I willi-prevent the loss of reactant vapors at this point.

In the insulated space between the pipe 61 and a metal wall 12 are disposed a plurality of webs 13 disposed at an angle to the pipe 61 to maintain the spacing between the pipe and the metal wall. The inner ends of these webs are adapted to fit fairly closely tothe outer surface of pipe 61 but are not secured thereto, whereby the pipe 61 may slide through the webs under the influence of thermal expansion. The webs are placed at an acute angle to the pipe 61 in order to substantially reduce the temperature diiferential per unit of length and thus cut down the heat loss by conduction along the webs 13. It will be noted that a similar type of connection is made at 14 on the reactor discharge pipe and is suitable for other conduits and pipes in the system. The webs 13 serve another function in reducing the ow of inert pressuring gas from the space about shell 50 into the quencher I8. The pressure drop through the gap between the end of a web 13 and the pipe 69 issubstantial and very little pressuring gas will iiow between the pipe 61 and its insulation due to the several high pressure drop gaps thus imposed in its path.

At its end remote from reactor I3, pipe 61 is connected to a manifold 14 for distributing gas in the quencher I8. A plurality of headers 15 extend from each side of the manifold 14 and a plurality of drop pipes 16 depend from each of the headers 15 into a body of relatively cold granular solid in the quencher. Granular solid from the air preheater enters the quencher through feed leg 41 and falls onto a plate 11 from which depend a plurality of feed pipes 18, supplying cold granular solid to the contacting zone below manifold 14. As shown, the contacting zone is enclosed by a shell 19 and an inert pressuring gas such as steam may be admitted by pipe 80 to the space between shell 19 and an insulated casing 8l. Quenched reaction products are withdrawn from quencher I8 by an outlet 82 open to the disengaging space among the drop pipes 16 and feed pipes 18.

Uniform flow of solids across the contacting bed in quencher I3 is induced by a number of flow control pipes 83 depending from a plate 84. Purging steam is introduced to the space under plate 84 by pipes 85'communicating with a ring manifold 86 supplied from steam inlet 36. Flow control plates 81 and 88 function to induce equivalent iiow through each of the pipes 83 and thus cause the latter to draw equally from all parts of the contacting bed.

As shown, conventional bellows type expansion joints'89 are provided on the granular solid transfer pipes and other places where the same are found desirable.

The thermal strains involved in apparatus of this type are well illustrated by application of this apparatus to the cracking of gas oil to produce ethylene. Circulating granular fused alumina having an average particle diameter of 0.3 inch in both the reaction and quenching cycles, 28.1% by weight of ethylene is produced at a mean effective temperature of 1440 F. and a contact time of 0.29 second. The granular solid is heated to 1575o F. in the heater and enters the reactor at 1546 F. A mixture of 33% steam and 67% gas oil (by weight) is admitted to the reactor at 625 F. with a space velocity of 3.12 volumes of liquid oil at 60 F.,per volume of reaction space per hour. A granular solid to oil weight ratio of 11.95 is maintained, using a zone of contact 24 inches deep. The heated reaction mixture is disengaged from the solid bed at 1545 F. and quenched with water to 1200 F., at which temperature it is transferred to the quencher and further cooled therein to 57i2 F. The quenched reaction mixture is further cooled in the spray condenser to 100 F. and is then treated for recoveryof the products of the reaction. Among the liquid bi1-products are 5.5% of depentanized motor gasoline having Vani end point of 416 F. and an octane number of 94.6 with 3 cc. of tetraethyl lead per gallon.

I claim:

1. In combination, a iirst vessel, a shell about i said vessel, means to introduce a pressuring gas between said first vessel and said shell, a second vessel and an insulated transfer line between said vessels comprising an inner pipe communieating at its ends with the respective interiors of said vessels, an outer pipe about and spaced from said inner pipe dening an annular space communicating at one endV with the space between said rst vessel and said shell and communicating at the other end with said second vessel, and a plurality of fins about said inner pipe spaced along a portion of the length of said annular space, each Vbeing of the form of a frustum of a cone having its apex directed toward first vessel and each being secured to one of said pipes and free of but closely fitting the other of said pipes.

` 2. In combination, a first vessel, a shell about said Vessel, means to introduce a pressuring gas between said first vessel and said shell, a second vessel and an insulated transfer line between said vessels comprising an inner pipe communicating at its ends with the respective interiors of said vessels, an outer pipe about and spaced :from said inner pipe defining an annular space communicating at one end with the space between said rst vessel and said shell and communicating at the other end with said second vessel, and a plurality of fins about said inner pipe spaced along a portion of the length of said annular space, each being of the form of a frustum of a cone having its apex directed toward said first vessel and each being secured at its outer edge to said outer pipe and having its inner edge free of but closely fitting said inner pipe.

3. In combination, a first vessel, a shell about said vessel, means to introduce a pressuring gas between said first vessel and said shell, a second vessel and an insulated transfer line between said Vessels comprising a free iioating inner pipe communicating at its ends with the respective interiors of said vessels, an outer pipe about Aand spaced from said inner pipe defining an annnular space communicating at one end with the space between said iirst vessel and said shell and communicating at the other end with said second vessel, and a plurality of annular fins extending around said inner pipe spaced along a portion of the length of said annular space, each being secured to one of said pipes and free of but closely tting the other of said pipes, said iins adapted to both provide support for said inner pipe and substantially prevent the transfer of pressuring gas from said space between said first vessel and said shell to the interior of said second vessel.

4. In combination, a first vessel, a shell about said vessel, means to introduce a pressuring gas between said first vessel and said shell, a Second vessel and an insulated transfer line between said vessels comprising a free floating inner pipe communicating at its ends with the respective interiors of said vessels, an outer pipe about and spaced from said inner pipe defining an annular space communicating at one end with the space between said rst vessel and said shell and communicating at the other end with said second vessel, and a plurality of individually circumferentially continuous fins extending about said inner pipe spaced along a portion of the length of said annular space, each being secured at its outer edge to said outer pipe and having its inner edge free of but closely fitting said inner pipe, said fins adapted to both provide support for said inner pipe and substantially prevent the transfer of pressuring gas from said space between said iirst vessel and said shell to the interior of said second vessel.

5. A transfer line comprising an inner pipe., an outer pipe about and spaced from said inner pipe defining an annular space, and a plurality of fins about said inner pipe spaced along a portion of the length of said annular space, each being of the form of a frustum of a cone having its apex directed toward said first vessel and each being secured to one of said pipes and free of but closely fitting the other of said pipes.

ERNEST UTTERBACK.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,871,508 Gardner Aug. 16, 1932 2,063,229 Corriston Dec. 8, 1936 2,240,618 Harris May 6, 1941 2,243,427 Kleifel May 27, 1941 2,324,195 Carlson July 13, 1943

Claims (1)

1. IN COMBINATION, A FIRST VESSEL, A SHELL ABOUT SAID VESSEL, MEANS TO INTRODUCE A PRESSURING GAS BETWEEN SAID FIRST VESSEL AND SAID SHELL, A SECOND VESSEL AND AN INSULATED TRANSFER LINE BETWEEN SAID VESSELS COMPRISING AN INNER PIPE COMMUNICATING AT ITS ENDS WITH THE RESPECTIVE INTERIORS OF SAID VESSELS, AN OUTER PIPE ABOUT AND SPACED FROM SAID INNER PIPE DEFINING AN ANNULAR SPACE COMMUNICATING AT ONE END WITH THE SPACE BETWEEN SAID FIRST VESSEL AND SAID SHELL AND COMMUNICATING AT THE OTHER END WITH SAID SECOND VESSEL, AND A PLURALITY OF FINS ABOUT SAID INNER PIPE SPACED ALONG A PORTION OF THE LENGTH OF SAID ANNULAR SPACE, EACH BEING OF THE FORM OF A

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