US3174924A - Quench method and apparatus - Google Patents

Description

March 23, 1965 w. c. CLARK ETAL 3,174,924

QUENCH METHOD AND APPARATUS Filed June 4, 1962 INVENTORS W. C. CLARK J.H. EN

A 7'TORNEYS Uit of Delaware Filed June 4, 1962, Ser. No. 199,747 6 Claims. (Cl. 208-48) This invention relates to quenching of hot hydrocarbon fluids. In one aspect it relates to a method and apparatus for quenching hot hydrocarbon fluids from a temperature above a carbon-forming temperature to a temperature below said carbon-forming temperature without deposition of carbon in the quench apparatus and in the transfer conduit downstream from the quench apparatus. In another aspect it relates to an apparatus for quenching hot hydrocarbon liquids as well as hot hydrocarbon vapors. In yet another aspect it relates to a quench apparatus which is suitable for injecting quench oil, quench water or a quench vapor such as steam, into a hot hydrocarbon stream.

In hydrocarbon conversion operations in which hydrocarbons are heated to carbon-producing temperatures, carbon is frequently deposited on the walls of transfer conduits through which the heated hydrocarbons are passed.

In many instances immediately following the conversion step the effluent therefrom is quenched to a temperature below which carbon deposition or conversion reactions take place. At the downstream end of a pipe bend, particularly a right angle bend, as a result of the centrifugal force of high velocity fluid passing around such a bend in addition to a secondary flow, there is produced a low pressure area at the locus at which the two oppositely revolving secondary flows meet.

The nature of the flow of fluids in bends has been thoroughly investigated and many interesting facts have been discovered. For example, when a fluid passes around a bend in either viscous or turbulent flow, there is established in the bend and immediately following the bend a condition known as secondary flow. This secondary flow is a rotating motion at right angles to the pipe axis. This secondary flow is in addition to the main motion or flow in the direction of the axis of the conduit. The friction-a1 resistance of the pipe walls and the action of centrifugal force combine to produce this secondary flow.

We have found that at the point of secondary flow there is a marked tendency for carbon to deposit from hydrocarbons at or above a carbon-producing temperature. Deposition of carbon, as will be realized, increases friction which in turn operates to resist fluid flow. Thus, as carbon deposition increases, pressure drop across the affected conduit increases.

In one instance in a 12-inch conduit, when passing heated hydrocarbon fluid from a conversion zone at a superatmospheric pressure and at a conversion zone efiiuent temperature, a pressure drop of about 4 pounds per square inch resulted when the quench L and transfer line were clean. The pressure drop increased to from 5 to 8 pounds per square inch when coke was deposited in the outer end of the quench L and in the transfer line following the quench L. Approximately 60 percent of this increase in pressure drop was caused by coke build-up immediately downstream from the quench oil injection L. This coke build-up was formed in the low pressure area created by the fluid flow through the 90 L.

An object of this invention is to provide a method and apparatus for quenching hot hydrocarbon fluid without the production of deposited carbon on the walls of the quench apparatus. Another object of this invention is to provide a quenching apparatus suitable for quenching States Patet hot hydrocarbon fluids from a temperature above a carbon-forming temperature to a temperature therebelow without the deposition of carbon in the outlet end of the quench apparatus and in the transfer conduits immediately following the quench apparatus. Still other objects and advantages of this invention will be realized upon reading the following description which, taken with the attached drawing, forms a part of this specification.

According to this invention we have devised a method and apparatus for accomplishing the above-mentioned objects and advantages by providing apparatus for addition of supplemental injection or quench fluid at the point of conventional carbon deposition in such quench Ls and subsequent transfer lines.

In the drawing FIGURE 1 is an elevational view, partly in section, of the apparatus of this invention. FIGURE 2 is an elevational view, in section, of a pipe L and subsequent conduit illustrating the area of normal carbon deposition. FIGURE 3 is a sectional view taken on the line 3-3 of FIGURE 2. FIGURE 4 illustrates on an enlarged scale, a portion of the apparatus of FIGURE 1. FIG- URE 5 is an elevational view of an alternate embodiment of the invention.

In the drawing, and particularly in FIGURE 1, reference numeral 11 refers to a transfer conduit downstream from a quench fluid injection L 12. A sleeve 13a is welded to the pipe L 12 in such a manner that upon installation of pipe 13, carrying a spray nozzle 14, spray is introduced into the L 12 in a direction along the axis and L 12 at its outlet end. Reference numeral 21 identifies directional arrows indicating the direction of fluid flow in the L 12. Reference numeral 15 identifies the spray of quench fluid from spray nozzle 14. We provide a further sleeve pipe 17 welded to the quench L at about the position illustrated. A flange 25 is attached to the outer end of pipe 17 while a flange 26 is welded to a conduit 16 as illustrated. A plate 20 is attached to the end of conduit 16 within the quench L 12. Adjacent this plate 20 and in the end portion of conduit 16 is a slot 19, provided for outlet of additional quench fluid from concluit 16 in a direction coinciding in general with fluid flow through the L. Reference numeral 25a refers to the fluid passed through the slot 19.

The area adjacent the outlet end of the pipe L 12 and the area of the transfer pipe 11 downstream from the outlet end of conduit 16 is the low pressure area referred to hereinabove. It is in this area that carbon deposition ordinarily occurs.

This carbon deposition in the area just mentioned is illustrated clearly in FIGURE 2. Reference numeral 22 identifies a carbon deposit in this low pressure area at the outlet end of L 12 and in the transfer conduit 11. The directional arrow 21, shown in FIGURES 1 and 2, are drawn to illustrate the effect of centrifugal force of a high velocity fluid passing through the L. As will be realized, the fluid rounding L 12 tends to concentrate at the L surface having the greatest L radius thereby providing a low pressure area identified by the coke deposition 22 of FIGURE 2. In FIGURE 3 is illustrated the eiiect of the secondary flow hereinbefore mentioned. Reference numeral 24 identifies the higher pressure area caused by the centrifugal force. From this high pressure area fluid tends to flow adjacent the periphery of the conduit in both directions. Thus, a pair of oppositely rotating secondary flow areas is produced, these being identified by reference numerals 23. The area identified by reference numeral 22 in FIGURE 3 (as deposited coke) is also the low pressure area which is opposite high pressure area 24.

According to our invention We provide an additional quench fluid inlet so positioned and oriented to provide additional quench fluid for washing the surface exposed to the low fluid pressure and for increasing the pressure in this area. Since the entire L and transfer pipes are at a high temperature, any of the quench fluid which, in case it is a liquid, vaporizes will cause an increase in pressure in this low pressure area. Thus, such an increase in pressure tends to equalize pressure in the conduit at this point and to reduce the effect of the secondary flows.

A spray nozzle suitable for use, as spray nozzle 14, is one which provides a full cone spray and is manufactured by Spray Enginering Company, Somerville, Massachusetts. Such a full cone spray nozzle is identified as Nozzle No. 11A and fully described in an advertizing sheet copyrighted 1948 by said engineering company.

In FIGURE 1, on observing the particular direction of the fluid flow directional lines 21, it should be noted that the form of spray from nozzle 14 is distorted from that of a true cone. This distortion is caused by the high velocity of fluid flow into and around the L 12. Since the spray 15 is so distorted there is reason to believe that spray liquid does not contact the Walls of the L 12 at the outlet end thereof and the walls of transfer conduit 11 immediately downstream from the L 12 in the low pressure area. Accordingly, s-ince the spray is believed not to contact this area, and because this area is hot, carbon deposition tends to occur. Accordingly, upon installation of the additional quench fluid injection pipe 16 for providing additional quench fluid through slot 19, we find that carbon deposition at the above-mentioned low pressure area is markedly reduced or substantially eliminated.

On reference to FIGURE 5, which illustrates an alternate embodiment of the invention, the quench fluid inlet pipe 13 is inserted further into the L 12 at a point near its outlet end. However, spray 15, issuing from spray nozzle 14, is still distorted somewhat in shape because of the centrifugal force of the fluid rounding the L 12. The spray fluid inlet pipe 16 with slot 19 provides additional quench fluid at this point for serving exactly the same purpose as described relative to FIGURE 1.

FIGURE 4 illustrates in detail the construction of the injection pipe 16. In this case plate 20 is welded to the end of conduit 16. A portion of the end of conduit16 is ground 011 and this opening or slot portion is identified by reference numeral '19. Thus, with the actual end of conduit 16 closed by plate 20, and with the opening 19 positioned in the manner illustrated, the fluid injected through pipe 16 flows in the downstream direction thus wetting and washing the surface of the pipe in the vicinity of the low pressure fluid area.

Pipe flanges 27, 28, 29, 30, 31 and 32 are illustrated for attachment of the corresponding quench L to theinlet and outlet transfer conduits as illustrated.

In one instance, injection quench oil pipe 13 was a 2- inch diameter schedule 80 stainless steel pipe while sleeve 13a was a 4-inch diameter 300-pound, 4-inch pipe section, the spray nozzle 14 was a 2-inch spray nozzle, mentioned hereinabove. Pipe 16 was l-inch in diameter and 19 /2- inches long. This length included a A-inch thick plate 20 welded to the end thereof adjacent slot 19. The slot 19 was A-inch wide and was Ai-inch deep. This A-inch deep means that the distance from the outer periphery of pipe 16 toward the axial center of this pipe which was ground away was flt-inch. The quench fluid injection conduit 16 extended into L 12 about 1 inch. This distance of 1 inch was the distance between the point of contact of an upward projection of the inner surface of transfer conduit 11 and the surface of plate 20 remote from That which is claimed is:'

1. A quench fluid injection assembly comprising in combination:

(1) a curved pipe L of relatively large diameter having an inlet and an outlet at its opposite ends; 7

(2) a first conduit for fluid coolant extending into said L through the wall section forming the longer outside curve thereof;

(3) a nozzle on the inner end of said first conduit directed substantially toward the center of the outlet end of said L;

(4) a second conduit for fluid coolant extending into said L through the wall section forming the shorter inside curve thereof adjacent said outlet end; and

(5) means on the inner end of said second conduit for directing fluid along the adjacent inner wall of the L toward the outlet end thereof.

2. The assembly of claim 1 wherein said second conduit extends through said wall transverse to the direction of flow in said L, the inner end of said second conduit is closed, and an opening is provided on the downstream side of same adjacent said outlet end.

3. In the quenching of a stream of hot hydrocarbon vapor from a temperature above the carbon formation temperature to a temperature below the carbon formation temperature thereof wherein said stream is passed at high velocity through an enclosed curved L-shaped quench tube into a coaxial downstream conduit and liquid quench is sprayed into said stream in the direction of flow thereof and along the axis of said tube at the outlet end thereof, and'wherein said stream and quench fluid are at a greater concentration and pressure adjacent the wall of said tube on the outside curve of said L near the downstream end thereof and adjacent the adjoining downstream wall of said conduit than their concentration and pressure adjacent the diametrically opposite walls of said tube and conduit whereby carbon is deposited on said opposite walls, the method of substantially reducing the deposition of carbon on said opposite walls comprising injecting additional quench fluid into said stream at a point just upstream of the juncture of said'tube and said conduit so that said additional quench-fluid flows principally along said opposite walls.

4. In the quenching of a stream of hot hydrocarbon vapor from a temperature above the carbon formation temperature to a temperature below the carbon formation temperature thereof wherein said stream ispassed at high velocity through an enclosed curved L-shapedquench tube into a coaxial downstream conduit and liquid quench is sprayed into said stream in the direction of flow thereof from a locus along the outer curve of said L adjacent the midpoint thereof and wherein fluid flow along the wall of said tube and the adjoining wall of said conduit directly downstream of said locus is greater than along the diametrically opposite walls of said tube and said conduit thereby causing carbon to deposit on said opposite walls, the method of alleviating carbon depositionon said opposite walls comprising passing a separate stream of quench fluid along said opposite walls from a locus adjacent the inside curve of said L just upstream of the juncture of said tube and said conduit.

5. The method of quenching a stream of hot hydrocarbon vapor from a temperature above carbon forming temperature to a temperature below carbon forming temperature wherein said stream flows through an arcuate L conduit into a coaxial downstream conduit and wherein carbon deposition normally occurs on the wallof said tube along the inside curve of said L and along the adjacent downstream wall of said conduit comprising the steps of:

(a) injecting a primary quench fluid in a downstream direction along an intermediate section of the outside curve of said L; and

(b) injecting a secondary quench fluid in a downstream direction along the inside curve of said L near its juncture with said conduit so as to flow said secondary quench fluid over the wall areas on which carbon normally deposits.

6. A quench fluid injection assembly comprising in combination:

(1) a curved pipe L attachable at one end to an inlet line and at the other to an effluent line;

(2) means for injecting a dispersion of a primary fluid quench from a locus adjacent the longer outside curve of said L toward the center area of the downstream end thereof; and

(3) means for injecting a dispersion of a secondary quench fluid from a locus adjacent the shorter inside curve of said L downstream along the wall thereof.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. 3. IN THE QUENCHING OF A STREAM OF HOT HYDROCARBON VAPOR FROM A TEMPERATURE ABOVE THE CARBON FORMATION TEMPERATURE TO A TEMPERATURE BELOW THE CARBON FORMATION TEMPERATURE THEREOF WHEREIN SAID STREAM IS PASSED AT HIGH VELOCITY THROUGH AN ENCLOSED CURVED L-SHAPED QUENCH TUBE INTO A COAXIAL DOWNSTREAM CONDUIT AND LIQUID QUENCH IS SPRAYED INTO SAID STREAM IN THE DIRECTION OF FLOW THEREOF AND ALONG THE AXIS OF SAID TUBE AT THE OUTLET END THEREOF, AND WHEREIN SAID STREAM AND QUENCH FLUID ARE AT A GREATER CONCENTRATION AND PRESSURE ADJACENT THE WALL OF SAID TUBE ON THE OUTSIDE CURVE OF SAID L NEAR THE DOWNSTREAM END THEREOF AND ADJACENT THE ADJOINING DOWNSTREAM WALL OF SAID CONDUIT THAN THEIR CONCENTRATION AND PRESSURE ADJACENT THE DIAMETRICALLY OPPOSITE WALLS OF SAID TUBE AND CONDUIT SHEREBY CARBON IS DEPOSITED ON SAID OPPOSITE WALLS, THE METHOD OF SUBSTANTIALLY REDUCING THE DEPOSITION OF CARBON ON SAID OPPOSITE WALLS COMPRISING INJECTING ADDITIONAL QUENCH FLUID INTO SAID STREAM AT A POINT JUST UPSTREAM OF THE JUNCTURE OF SAID TUBE AND SAID CONDUIT SO THAT SAID ADDITIONAL QUENCH FLUID FLOWS PRINCIPALLY ALONG SAID OPPOSITE WALLS.

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