US2055212A - Expander for cracking hydrocarbon oils - Google Patents

Description

Sept. 22, 1936. E. w. ZUBLIN EXPANDER FOR CRACKING HYDROCARBON OILS Filed Sept 19, 1933 m www was. mg N 2 INVENTOR.

Patented Sept. 22, 1936 UNITED, STATES EXPANDER FOR CRACKING HYDROCAR- BON OILS Ernest W. Zublin, Fort Worth, Tex., assignor to Texas Pacific Coal & Oil 00., Fort Worth, Tex.,

a corporation of Texas Application September 19, 1933, Serial No. 690,036

2 Claims.

This invention relates to an apparatus for cracking hydrocarbon oils in vapor phase and more specifically to a multiplicity of expander units having a novel arrangement of connecting conduits for the passage of vapors being converted, and also of fiues for the combustion or other gases employed in heating the units.

In a co-pending application Serial No. 656,206, filed February 11, 1933, by the present applicant and others, a process of converting higher boiling hydrocarbons into lower boiling hydrocarbons is described which includes introducing cracking stock into contact with hot cracked vapors produced in the process whereby said vapors are quenched and substantially vaporized, fractionating the resulting mixed vapors to produce a gasoline fraction as overhead and cracking distillate, condensing the gasoline fraction, vaporizing said cracking distillate, superheating said vapors to a point betweenthe flash evaporation and cracking temperature, and passing said vapors through a. vertical expansion zone heated uniformly to a conversion temperature by means of a plurality of heat zones extending vertically therethrough, whereby the hot cracked vapors to be treated in the beforementioned manner are produced. The apparatus of the present invention is designed particularly for use in processes of this type, although its utility is not limited thereto.

An object of the present invention is to increase the flexibility and raise the efiiciency of processes of the above type.

A further object is to provide a cracking apparatus capable of adjustment to control cracking temperatures thereby to control the rate of cracking, at several stages of the cracking operation independently of other stages.

A more specific object is'to provide a series of interchangeable expander units, any one of which may be cut out of the process without interrupting the'cracking operation thereby increasing the operating cycle of the apparatus. A further object is to provide an apparatus capable of being regulated by simple and quick adjustment to alter the time period of cracking without changing the rate of passage, of the vapors through the cracking apparatus, thereby permitting the apparatus to continuously operate at full capacity.

The construction of the expander units per se forms no part of the present invention, although by far the best results are obtained by use of units of the design hereinafter described, the

" details of the construction being described more fully in a co-pending application Serial No. 662,676, filed March 25, 1933.

In its broadest aspects the instant invention contemplates the arrangement of a multiplicity of three or more expander units connected by valved conduits in such manner that hydrocarbon vapors to be cracked and during cracking may be passed in series through any number or any combination of expander units and by-passed around any remaining units, each expander unit 10 being adapted for heating independently of the other units, thereby permitting optimum temperatures to be obtained in each unit, certain of the units to be heated while others remain unheated. With this arrangement any unit in 15 use can be cut out of operation for cleaning or other purpose and any idle unit put into operation by closing or opening valves in the by-pass and connecting conduits.

The apparatus of the present invention can be better understood from the accompanying drawing in which;

Figure 1 diagrammatically represents a front elevation with parts in section,

Figure 2 represents an end view of an expander unit, and

Figure 3 is a graphic view illustrating the adaptability or flexibility of the present apparatus in obtaining optimum temperature and time conditions in the cracking process, as will be hereinafter explained.

The value of the apparatus of the invention can be understood better from a. consideration of the nature of the processes which are to be carried out in the apparatus and the theory upon, which the operating conditions are based, saidv conditions being controlledby manipulation of the valves and dampers provided in the apparatus.

When the present apparatus is in use, hydrocarbon vapors of a crackingstock, superheated or not as desired, are passed through the expander units in series at a predetermined rate, the temperature to which the vapors are heated in each expander being also predetermined to obtain the largest yield of desired cracked products. As is well recognized in the. petroleum industry, the largest yield from any certain cracking stock is obtained by. regulating the operating conditions to obtain an optimum time and temperature product. (Each different cracking stock requires 50 difierent. time and temperature conditions.) Manyapparatuses have been designed to take advantage of this knowledge in a general way, butv as far asthe applicant is aware none has been capable of regulation of the temperature of the hydrocarbon vapors independently at several points such that optimum cracking conditions can be had during the whole period during which the vapors are being cracked, as is accomplished with the present apparatus.

The provision for independently regulating the temperature of the vapors at a plurality of points not only permits optimum temperature for a particular cracking stock but also permits the conditions to be adjusted to obtain maximum yields from any one of a variety of cracking stocks, including topped crude, gas oil and kerosene, The provision for putting into operation any number of expander units permits the time factor to be adjusted in correlation with the temperatures employed.

To illustrate the extreme flexibility of the present apparatus to obtain optimum time and tem-. perature conditions, the operating dataof the present apparatus as applied to three difierent runs has been shown in the'graph, constituting Figure 3, of the drawing. With reference to this figure, the temperatures during the period of the cracking operations, as ordinates, have been plotted against the time factors, as abscissae, the time being represented by the number of expanders instead of in seconds which evaluation is permissible because of the operation of the process at a constant throughput and of the fact that the size of the expanders for an existin ap ar s i a n an I Thecurves I, Z, and 3 represent three different rates of heating, the initial and final temperature being the same in each case. The rate of cracking during the processes as represented by these curves differs to a very great extent as is evident from the generally accepted axiom that the. rate of cracking approximately doubles for every twenty to twenty-flvedegrees F. increase in temperature between 750 and 1000 F. For example, the rate, of cracking of the vapors in the heating curves I and 3, after passage through two expanders' is about 16 or more times as fast in the latter than. in theformer curve, for there is a difference of.100: temperature.

It is obvious from these curves that the-amount of cracking effected maybe great, medium or small, dependent upon the temperatures 'em.-. ployed during the whole of the cracking period. It is further obvious that the ability to regulate the temperatures of the series of expander units permits the apparatus to, be used for cracking a widevariety of cracking stocks each under its own particular optimum temperature conditions, the optimum time being obtained by merely'varying the number of expanders connected in the series.

A second set of curves can be derived from the present curves which represent the rate of cracking during the passage through the expander system. By integrating this new set ofcurves, .the amount of cracking which has taken place at any point in the system can be easily estimated. From such calculations, it appears obvious that the amount of cracking can be greatly-varied by altering the rate of heating or temperatures. of the vapors at various points during the. cracking period. The extreme flexibility of the cracking process obtained by the use of the instant apparatus is readily apparent.

With reference to Figures 1 and 2. of the drawing, there is illustrated a seriesof vertically elonated expander units l to. 6 inclusive, pierced by a plurality of heating tubes I equi-distantly spaced from each other. Each expander unit is sur-, rounded and supported in a removable mannerby a casing ll of a sufficiently larger diameter than the expander unit to permit a portion of the heating gases to pass around the exterior of the expander, the provision for heating both interiorly and exteriorly, accomplishing uniform heating and cracking of the whole stream of vapors passing therethrough. The temperatures throughout the expander at any horizontal plane are substantially the same.

A furnace I2 is provided for supplying combustion gases for heating the expander units, the same being connected through a duct or flue 13 having valved openings I 4 leading to each expander unit. The provision of valves permits the heating and the temperatures in each expander to be controlled independently. Though separate'furnaces could be employed for each expanderwith some degree of satisfaction, better results are obtained by the use of a single furnace, for with'this arrangement exchangeability between the expanders can be had without; delay for temperature regulation of independent furnaces which in such case would be necessary.

Each expander unit is provided with a top I 5 bolted or otherwise removably attached to the casing walls I I. At the back of each casing there is a heating gas outlet conduit l6 leading to a manifold conduit I1, the conduits l6 being provided with valves 18. The conduit ll leads to a heat exchange chamber l9 and finally to the stack 20. Whereas. the illustrated furnace and flue arrangement is adapted for heating by upward passage of vapors through and around the expander units it should be understood that an arrangement adapted for downward passage is also suitable and within the scope of the present invention.

Each expander unit'has an inlet conduit 22 extending almost to its bottom, and an outlet conduit 23 terminating at its top. All of these conduits connect into a manifold conduit 24. Valves 25,26- and?! are provided in said conduits as illustrated thereby enabling the cutting out of operation of any one or more expanders. The portions of the manifold conduit between the junctions of the inlet and outlet conduits thereto serve as lay-passes upon manipulation of the valves in obvious manner.

A heat exchange coil 30 is mounted in the chamber l9 and is preferably employed for superheating the vapors before, their introduction into the cracking units. Alternatively the coil may be used for vaporizing the oil. As illustrated, the coil 30 is connected through valved lines 3| and 32 to themanifoldconduit 24v leading to the expander units. Additional heating units (not shown) may beprovidedbetween the lines 3| and 24, if necessary torbring the vapors to the proper temperature before introduction into the expander units.

A valved steam inlet conduit 35 is connected to each inlet conduit 22,. and valved outlet conduits or vents 36 to each outlet conduit 23. Steam is passed through any expander unit after it has been cut out of operation for cleaning, repairing or for any other purpose. Y

The advantagesobtained by the arrangement of the apparatus constituting the. present invention may be summarized as follows:

1. The rate of flow of heating gases'to each expander unit is controlled individually thereby permitting accurate and independent control Within wide limits of the cracking temperature in each expander. '2. The number of units connected in series may: be altered at any time thereby permitting limitation or extension of the time period of cracking, the alteration being accomplished without changing the throughput of the cracking unit. 3. Any unit may be cut out of the process for cleaning or other purpose, and any idle unit substituted therefor without inter.- rupting the process. 4. A series of small expander units can be built more cheaply than one or two large ones of the same total volume.

Whereas the present invention has been described with reference to expander units and a heating means of a particular nature, it should be understood that some of the advantages of the invention can be obtained while using units of other and different construction. The field of the present invention is to be limited only by the scope of the claims appended hereto.

I claim:

1. An oil cracking apparatus comprising a multiplicity of expander units, casings enclosing said units, a manifold conduit for conducting vapors, inlet and outlet conduits connecting said manifold conduit and each of said expander units, valves in said manifold conduit and in said inlet and outlet conduits adapted to cut out selectively any of said units, a source of heating gases, 2. manifold flue connected to said source of heating gases and communicating with the interior of said casings for conducting heating gases thereto in indirect heat transfer relationship with respect to said vapors, valve means controlling the admission of heating gases to said casings, and a discharge fiue for said heating gases.

2. An oil cracking apparatus comprising a multiplicity of expander units, a manifold conduit for conducting vapors, inlet and outlet conduits.

connecting said manifold conduit and each of said expander units, valves in said manifold conduit and in said inlet and outlet conduits adapted to cut out selectively any one of said units, a source of heating gases, a casing enclosing each of said expander units, a manifold flue connected to said source of heating gases and leading to one end of each of said casings, a manifold discharge flue connected to the opposite end of each of said casings and leading to a stack, and a heat exchange coil communicating with said manifold conduit and disposed in said discharge flue.

ERNEST W. ZUBLIN.

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