US2035275A - Vapor phase cracking apparatus - Google Patents

Description

- Mafch 24, 1936. G. M. PFAU ET AL 2,035,275

VAPOR PHASE CRACKING APPARATUS Filed March 25, 1933 m r Om 11/ 28 FM a6 INVENTOR. George M. Pfau, Henry .H. Pruiff. BY I I Patented Mar. 24, 1936 U NI TED S TAT E. S

VAPOR PHASE CRACKING APPARATUS George M. 'Pfau and Henry Harris Pruitt, Fort Worth, Tex., assignors to Texas Pacific Coal & Oil "GoJFort Worth, -Tex., a corporation of Texas .ApplicationMarch25, 1933, Serial No. 662,676

8 Claims.

This invention relates to apparatus for .the conversion of higher boiling hydrocarbons to produce hydrocarbons of a lower boiling range of the .order of gasoline, and more particularly relates to an improved expander foruse in the cracking of oils while substantially in the vapor phase.

Ina companion application of .-I. Morris Levine, filed April 25, 1933, Serial No. 667,766 a double shell type of expander is described, said expander having heating tubes extending therethroug-h for internal heating and a flue casing or shell around its exterior, servingas a flue for eifectin external heating. Such an expander hasmany l5 advantages over prior forms of expanders or heat exchanging devices for the proper heating of vapors and is used with greater safety. In accordance with the present invention we have found that certain improvements could be made 2 on such .prior construction as will be hereinafter described.

(It'is one of the principal objects of our invention to provide an expander or heat exchange apparatus 'for vapor phase cracking which will effectively and uniformly raise the temperature of the vapor .to and maintain them withinthat range .best suited for the particular cracking stock'being treated. I

Another object of our invention is to provide a heat exchange apparatus for uniformly increasing the temperature of hydrocarbons particularly in the vapor state, which apparatus may be easily and quickly dismantled for the removal of carbon and other materials deposited on the internal and external surfaces.

.Another object of the invention is to provide a heat exchange and expander chamber pierced by a ,plurality of heating tubes securedto .end plates .in which the entire bundle oftubes may lie-removed as a unit for cleaning and inspection.

Other objects andadvantages of ourinvention will .appearfrom the followingdescription thereof. taken -in connection with the attached drawing which illustrates -a preferred embodiment thereof and in which there is shown .a vertical sectionsubstantially through the center of the expander,

The rhigh temperature maintained in heat exchangers .particularly in exp anders for the .cracking of higher boiling point hydrocarbons to lower boiling point hydrocarbons is such that gaseous seals are maintained with difficulty. It is .essential .that the expander chamber receiving the vapors to be cracked be leak-proof in order to insure operating efficiency and safety from flashing. Such expanders, however must be periodically cleaned to remove the unavoidable carbon deposits, for such deposits materially reduce'the heat exchange efficiency of the expander, and interfere with the uniform conduction of the heat through the various parts of the expander.

We have therefore developed an expander device capable of effecting uniform heating ofthe vapors introduced into the vapor chamber and 10 which may be dismantled, cleaned and inspected as often as necessary. In particular it consists of an outer chamber enclosed by wall or shell l0 which may be of brick or other suitable heat resistant .or refractory material, said chamber be- 5 ing adapted to receive hot gases through the opening I I from any suitable source, such as'from a furnace (not shown) either combustion gases or hydrocarbon gases being suitable. For ef-, fective operation, the shell l9 preferably is ver- 20 tically disposed although other positions may be found suitable. Inasmuch as the cracked vapors and the heated gases naturally tendto rise, and a constant and uniformflow of both is de- I sired, the stack shape or vertical position is most 25 satisfactory. 7 V n Mounted within the flue wall In and spaced therefrom is .a vapor chamber or expander having a shell or wall. 12, which chamber receives the vapors to be converted through the inlet I3 hav- 30 ing an extension conduit l4 adapted to convey thevapors substantially to the bottom of the chamber. The space l5 between the expander wall 10 and the flue gas wall l2 serves as a conduit for a portion of heating gases passing u 3 wardly therethrough, which gases uniformly heat the outer wall of the vapor chamber. The remaining gases pass through a series of tubular conduits or heating tubes l6 which extend through the vapor chamber and which, are equidistantly spaced from each other and in a preferred construction also from the walls, said tubes being secured to the end plates of the shell l2 as hereinafter described.

The advantages, of this general construction are set forth more in detail in the companion application of I. Morris Levine heretofore mentioned.

The tubular conduits 16 are sealed in the 'top end plate l'l and to the bottom end plate l8,by any desired method as welding, rolling or otherwise. The bottom plate 18, is in the form of a round inverted box-like structure having an opening boundedby flanges l9 which cooperate with inwardly projecting flanges 20 extending'inward- 1y from the wall l2 of the expander chamber to secure the structure in position. Suitable bolts, clamps or other securing devices 2! are employed to join the flanges l9 and 20 to form an efiective seal against vapor leaks. The upper plate I! is also bolted, sealed or otherwise attached by securing means 22 to an outwardly turned flange 23 formed on the upper end of the wall l2 of the vapor chamber. Other methods of attachment may be employed if desired. For example, it has been found that a tongue and groove arrangement together with a high temperature resistant gasket is especially effective in securing the end plates I! and IE to the flanges 22 and 20 respectively.

The hydrocarbon vapors to be cracked are heated to relatively high cracking temperature in the expander by the heated gases which pass both through the bank of tubes l6 spaced substantially equi-distantly from each other and through the annular space'or channel I 5 between thetwo walls or shells.

The expander is supported in the shell 10 by means of a perforated supporting ring 24, formed on, welded or otherwise attached to the wall l2 which in turn is supported by a perforated annular ring 25, resting upon a series of brackets 26 attached to the flue wall 10. The size and number of holes or slots in these rings are such that the division of the heating gases as between the tubes I 5 and the space l5 effects uniform heating of the vapors within the expander chamber. By supporting the expander only at one horizontal plane near the top, thermal expansion and relief of stresses and strains is provided for.

The flue gas wall l0 extends some distance above the expander chamber forming a chamber 26 covered by a removable plate 21 attached by any suitable means 28 to said wall. The vapor inlet pipe I3 as well as the vapor discharge pipe 29, connected to the top end plate I! in couplings 30, pass through this plate, suitable stuffing boxes 3| being used to completely seal the connections. The heating gases pass from this chamber through the outlet 32.

In order to remove the tube bank for cleaning or repairing, the stuffing boxes are loosened, the inlet or outlet tubes are withdrawn and the cap plate 21 is removed. The vapor chamber then may be easily lifted out of the flue chamber wall. By removing the bolts 2| and 22 holding the tube bank to the vapor chamber walls l2, the tube bank may be removed from said walls so that the outside of each tube can be cleaned, inspected or repaired, without separating any of the tubes from the end walls I! and I 8.

The present device can be constructed at a very low-cost and is extremely easy to dismantle. Furthermore, it is safer to operate, for even should a leak of vapors from the inner chamber occur under circumstances where the flue gases contain sufficient oxygen to cause combustion of the vapors, the fire will be confined to the space between the chambers and likely be brought to the attention of the operator before any damage is sustained. The expander is also an eflicient heat.exchanger, for the vapors are heated both internally and externally. It is of course to be understood that either liquid phase or vapor phase hydrocarbons may be uniformly heated to cracking temperature in the chamber.

While we have shown a preferred form of apparatus in detail, it is to be understood that many modifications may be made thereto without departing from the novel features of the present invention, and we therefore desire a broad interpretation within the scope and-spirit of the description herein and of the claims appended hereinafter.

We claim:

1. An expander tank for the conversion of higher boiling point hydrocarbons to lower boiling point hydrocarbons which consists of an inner shell forming a vapor chamber, a tube bundle mounted within said chamber, said tube bundle being removably secured at each end to said shell, an outer. shell forming a flue gas chamber surrounding said vapor chamber, a bafile ring within said flue gas chamber supporting said vapor chamber, said vapor chamber and flue gas chamber having passageways for the passage of heating gases therethrough, one of said passageways comprising the tubes of said tube bundle, said tube bundle and inner shell being removable from said outer shell.

2. In apparatus for the conversion of hydrocarbon oils into lower boiling hydrocarbon oils such as gasoline, an expander tank which comprises an inner shell and end plates attached thereto forming a' pressure tight chamber adapted for the passage of hydrocarbons, a plurality of tubes projecting through said chamber, and attached to said end plates,.an outer shell surrounding said inner shell and spaced therefrom, a conduit for introducing hot gases into said outer shell on the exterior of said inner shell chamber, a plurality. of flue gas tubes within said chamber connecting said end plates, an outer shell of refractory material completely surrounding said inner shell, means for passing heating gases through said outer shell and through said flue gas tubes and means for introducing and removing hydrocarbon vapors into said conversion chamber adjacent the bottom thereof at a point near the outer periphery of the same, and means for removing said hydrocarbon vapors from said conversion chamber at a point adjacent the top thereof and diametrically opposed to the point of introduction of said Vapors. 4. A heat exchange apparatus for hydrocarbons comprising an outer vertical shell,.an inlet for introducing heating fluid at the bottom, an outlet for removing the same near the top, an outer end plate removably attached to the top of said shell, an inner vertical shell supported within said outer shell and spaced therefrom having end plates removably. attached thereto and a bank of tubes connecting the same, the shell, end plates and tubes constituting a heating chamber, inlet and outlet conduits extending through the top end plates of said outer shell and of said inner shell, said heating chamber being removable as a unit from said outer shell through the top thereof upon detachment of the outer top plate attached thereto.

5. An expander tank for the conversion of higher boiling point hydrocarbons to lower boiling point hydrocarbons comprising an outer ver-' tlcal shell, means for introducing heating gases at the bottom and for removing them near the top of said shell, an outer end plate removably attached to the top of said shell, an inner vertical shell supported within said outer shell and having end plates connected by a plurality of uniformly spaced heating flues forming with said shell a vapor conversion chamber therebetween, inlet and outlet conduits extending through said outer top plate and inner top plate for introducing vapors into and for removing the same from said chamber, said inlet conduit extending to a point adjacent the bottom of said chamber, said heating gases being adapted to pass between said shells, and means for throttling the flow of said heating gases passing between said shells.

6. An expander tank for the conversion of higher boiling point hydrocarbons to lower boiling point hydrocarbons comprising an inner shell provided with end plates which, together with said shell, form a vapor chamber therebetween, means for introducing hydrocarbons to be converted into said vapor chamber, a plurality of flue gas conduits extending through said chamber in gas tight relation thereto, said conduits being removable as a unit from said shell, an outer shell completely surrounding said inner shell and spaced therefrom, and means for passing hot flue gases through said outer shell for passage through said conduits and around said inner shell whereby they give up a portion of their heat to said hydrocarbons for conversion of the latter, said inner shell together with its end plates and conduits being bodily removable from said outer shell as a unit to facilitate repair thereof.

7. In an expander tank for the conversion of higher boiling point hydrocarbons to lower boiling point hydrocarbons, a shell having an outwardly turned flange at one end thereof and an inwardly turned flange at the other end thereof, an end plate removably secured to said outwardly turned flange, and an open ended box shaped end plate having an inwardly turned flange secured to the inwardly turned flange of said shell on the inner side thereof and being contained within said shell, a bank of flue gas conduits extending through said shell and having their ends secured in said end plates, said box-like end plate being slidable through said shell for removal of the same together with said bank of conduits from said shell, an outer shell surrounding said inner shell and in which said latter shell is suspended, means for introducing vapors to be converted into the interior of said inner shell at a point adjacent the lower end thereof, means for conducting converted vapors from the top of said inner shell, and means for passing hot flue gases through said outer shell for passage through. said conduits and around the outside of said inner shell.

8. An apparatus for converting hydrocarbon vapors, comprising an outer vertical shell, means for introducing heating gases at the bottom and for removing them near the top, an outer end plate removably attached to the top of said shell, an inner vertical shell supported within said outer shell having end plates connected by a plurality of heating flues which are uniformly spaced from each other throughout the entire cross sectional area of said shell and forming with said shell a vapor conversion chamber therebetween, inlet and outlet conduits extending through said outer top plate and inner top plate for introducing vapors into and removing the same from said chamber, said inlet conduit extending to a point adjacent the bottom of said chamber.

' GEORGE M. PFAU.

HENRY HARRIS PRUITT.

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