US2089292A - Dual two-stage cracking apparatus for petroleum oils - Google Patents

Description

E. A. OCON Aug. 10, 1937.

DUAL TWO-STAGE CRACKING APPARATUS FOR PETROLEUM OILS Filed April 10, 1956 39 wiwmfi w IIIIII W R.

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Patented Aug. 10, 1937 DUAL 'TWO-STAGE CRACKING APPARATUS FOR PETROLEUM OILS Ernest A. Occn, New York, N. Y.

Application April 10, 1936, Serial No. 73,616

Claims.

This application is a continuation in part of my application filed December 2'7, 1933, Serial No. 704,174,.nowU. S..Patent 2,052,148 as to the apparatus disclosed in saidapplication, certain 5 improvements having been added thereto.

In the present apparatus, a furnace is divided into two sections by an intermediate wall so as to provide two separate heat-receiving areas. Each section is divided into a combustion area -and a convection area.

Within each convection areais disposed an initial charging stock vaporizing coil and a secondstage cracking coil adapted for intercommunication, and in the combustion section is disposed one or a plurality of first-stage cracking coils, certain of the tubes thereof being catalytic tubes. Within each heating area is also disposed a steam superheater adapted for, discharge into the initial first-stage cracking .coil and also into the vaporizing coil.

Aycharacteristic of the apparatus is that a wallseparating the two heating areas contains tubes through which liquid, such as burner. fuel is passed, absorbing heatby conduction from 5 said wall and notonly increasing the life of the latterbut serving asan element in the control of the temperature of either or both convection sections under operation.v

Bymeans of a communication between the second-stage cracking coil and the vaporizing coil of either section, control ofv the temperature of the vapors in;their-.second-stage cracking may be effected vby discharging, into the second-stage cracking-coil a suitable. proportion of the relatiVB1y COQ1 oilsteam vaporsfrom the vaporizing coil. r

The apparatus enables the operation of the two 'independent units under difierent thermal and/or pressure conditions and a simultaneous 40 ,dischargingof thecracked products for blend- -ingand simultaneoustreatment. For example, one section of-thefurnace may. be operated to produce-highlysaturated light products and the, second section operated for theproduction of light products-of less saturation, and the cracked vapors from thetwo sections may be blended and fractionated to. .produce high anti-knock motor fuel.

The invention will-be. described with reference to. the accompanying drawing in which:--

Figure 1 is a diagrammatic view of an apparatusconstructed in accordance withthe invention.

Figure 2 is adetailed.viewin sectionshowing a Venturi connection, between, the. vaporizing 0011 and the second-stagecracking, coil, whereby a the coils may be operated under relatively different pressures, and at the same time, a pre determined proportion of the vapors from the vaporizing coil will be mixed with the vapors entering second-stage cracking.

Referring to the drawing, A designates a dual furnace (of fire brick or other refractory material capable of withstanding the required internal temperature), divided into two independent areas by wall B, each area having a combustion section C or Cat and a convection section D or Dr.

The charging stock passes into convection section D through pipe i, preferably after first receiving heat froma suitable source, as, for example, a heat exchanger (not shown). The preheated charging stock enters the vaporizing coil 2 and the charging stock vapors thus pro duced pass into pipe 3. The lower end of pipe 3 is connected with the first-stage cracking coils 4, 4m, in the combustion section C, which coils receive superheated steam through pipe 5, from superheater coil 6 located within the combustion section C at the top of the furnace. The steam superheater coil also discharges through a branch pipe "I communicating with the charging stockof pipe i so that additional heat is imparted to the charging stock and the viscosity of l the latter is lowered prior to the vaporizing action of coil 2.

After leaving the first-stage cracking coils 4, 4.1:, in the combustion zone, the vapors under cracking reactions pass to pipe 8 which transfers the vapors to the second-stage cracking coil 9.

Control of the temperature of the vapors entering the second-stage cracking is effected by manipulating a valve iii in pipe 3 which valve controls the passage of the uncracked vapors through a venturi i 1, Figure 2, the nozzle of which projects into the pipe 9a: which effects communication between coil 2 and the second-stage cracking coil 9.

In the second heating area of the furnace, the charging stock preferably mixed with superheated steam from pipe l2, enters vaporizing coil 250 from pipe ix. The vapors thus produced are led to pipe 31: communicating with the first-stage cracking coils M, Mr, in the combustion section Cw, the first-stage cracking coils discharging into a pipe. l5 connected with the second-stage cracking coil i6.

Pipe 30: is also in communication with a Venturi tube of the same construction as that shown in Figure 2 at i I, having its nozzle discharging into the second-stage cracking coil l6 so that by manipulating valve like a predetermined proportion of therelatively cool vapors may be injected into the second-stage cracking coil for regulating the temperature of the vapors undergoing final cracking reactions.

In each combustion section I have shown a burner I! receiving fuel from pipe l8 communicating with pipe I83: receiving fuel from heat absorbing coils l9 disposed in the upper part of wall B which divides the furnace into two heating sections. Coil 23 is adapted to receive any fluid used in the process such as hydrogenous vapors or gas, as, for example, cracked hydrocarbon gas, preferably cool. It has a double function of cooling wall B, and secondly, absorbing heat from the upper portion of either or both convection sections D, Dr, in accordance with the quantity of cool fluid passed therethrough, to secure, as one function, jointly with the action of the Venturi tubes l l and valves H] a satisfactory control of the thermal reactions. The Venturi tubes enable the use of a higher pressure in either one of the coils 2 and 9, or either one of the coils 2m and IS, without disturbance in the normal action of the connected coil.

I prefer that the tubes of the second-stage cracking coil 9 or it be larger in diameter than the tubes of the first cracking stage 3, 4x or I4, Mx, so that there will be a drop of pressure in the vapors when they are passed to the secondstage cracking coil in either case.

Instead of leading burner fuel through coils 23 in the division wall I3, I may lead any fluid for subsequent passage to the coils or one of them. For example, by closing the valves 25 and opening the valves 22, a supplementary or primary flow of charging stock or any flow-material desirable for addition to the primary charging stock,

, may be passed through pipes Him connected with pipes l I at, and thence to the inlet of coil 2 or the inlet of coil 23:, or to both coils simultaneously.

A distinct advantage of the apparatus is that if the coils of one of the heating sections need cleaning or the activity of the catalytic tubes if used has been substantially lowered, by shutting off the feed of the hydrocarbon material from the affected circuit and allowing steam to flow therethrough until the affected coils are cleaned and the clogging material removed, and/or activity of the catalysts recovered, then by turning on the heat and supply of hydrocarbon material,

the complete'unit starts operation at once and without stopping the flow through the second unaffected heating section. Also, by shutting off the heat and feed of the hydrocarbon material from an afiected circuit of the unit, the coils may be cleaned, repaired or replaced without aifecting the operation of the second heating section.

The catalytic tube may be made of, or lined with, a suitable catalytic material, say, chromenickel-steel.

In the operation of the apparatus, the charging stock from any suitable source passing through either one or both of pipes l, meets a blast of superheated steam. The steam-oil vapors pass through the appropriate vaporizing coil and the oil-steam vapors may reach a temperature of incipient cracking in its vaporizing coil. The oilsteam vapors thence pass through the two sections of the first-stage cracking coils in the appropriate combustion area, and thence pass into the appropriate second-stage cracking coil, which, by reason of the Venturi tube l I may be operated under any desired pressure relatively to the vaporizing coils.

By opening valve H0 or low a desired degree, a

' suitable proportion of the uncracked but vaporized oil-steam mixture will be passed directly from the appropriate vaporizing coils into the second-stage cracking coils to control the temperature of the vapors therein and to effect a rapid cracking action upon the uncracked vapors. It has been pointed out above that the second-stage cracking coils are preferably of larger diameter than the coils of the first stage. I also prefer that the second-stage cracking coils be greater in length than the coils of the first stage.

I have placed in the outflow pipes for the cracked products, l9 and I92; pressure control valves 20, 20:0, the operation of which is well understood in the art. By means of these valves the pressure under which the cracking operations are effected in one of the heating sections may be different from that of the second section. It will further be understood that pumps, temperature intakes, controls and pressure regulators and other commonly used elements may be placed at appropriate points, as is well understood in the art.

By reason of the increased diameter and length of the second-stage coils, I prefer that the reactions therein be under lower pressure than in the first-stage cracking coils and vaporizing coils.

While I have described the preferred embodiment of my invention, it is understood that modifications will vary within comparatively Wide limits provided they do not depart from the scope and benefits of the invention and claims. In fact, many variations may be made within the general scope and extent of the invention as I have not I described my apparatus in a limiting sense.

The Venturi construction illustrated in Figure 2, in addition to its application intermediate the vaporizing and second-stage cracking coils, may

be applied for controlling the flow of charging stock and steam to the vaporizing coil in either or both heating sections of the furnace. Thus the injector tube may be carried by steam pipe 7 or steam pipe l2 and projected within the appropriate charging stock pipe. By this arrangement, pressure of the steam may be greater'than that of the charging stock and hence may act as a conveyor for the charging stock, or vice versa.

What I claim is:

1. A dual two-stage cracking apparatus for hydrocarbon oils, which comprises a furnace divided by a wall into two heating sections, a wall in each section dividing the same into combustion and convection areas permitting the passage of gases from the combustion area to the convection area, a vaporizing coil at the lower portion of the convection area of each heating section, means for leading a hydrocarbon oil charging stock to said vaporizing coil, a second-stage cracking coil disposed above each vaporizing coil, a first-stage cracking coil in each combustion area and comappropriate vaporizing coil, means whereby steam may be led from said superheater to the firstbustion section, and heat control means for-the convection areas comprising'a plurality of intercommunicating tubes disposed in said division wall between the two heating sections, adapted to receive a relatively cool flow material and to lead the same to the vaporizing coils receiving hydrocarbon oil chargingstock. M

.. stage cracking coil, heating means in each com- 2. A cracking apparatus for hydrocarbon oils, which comprises a furnace, a wall in the furnace dividing the same into combustion and convection areas communicating at the top thereof, a vaporizing coil at the lower portion of the convection area, a second-stage cracking coil disposed above the vaporizing coil, a first-stage cracking coil in the combustion area and receiving vapors from the vaporizing coil and discharging vapors undergoing cracking reactions to the second-stage cracking coil, a steam superheater in the furnace and communicating with the vaporizing coil, means whereby steam may be led from said superheater to one of said cracking coils, heating means in the combustion section, and a heat control for the second-stage cracking coil comprising means for injecting therein vapors directly from the vaporizing coil.

3. A cracking apparatus for hydrocarbon oils, which comprises a furnace, a wall in the furnace dividing the same into combustion and convection areas communicating at the top thereof, a vaporizing coil at the lower portion of the convection area, a second-stage cracking coil disposed above the vaporizing coil, a first-stage cracking coil in the combustion area and receiving vapors from the vaporizing coil and discharging vapors undergoing cracking reactions to the second-stage cracking coil, a steam superheater in the furnace and communicating with the vaporizing coil, means whereby steam may be led from said superheater to one of said cracking coils, heating means in the combustion section, and heat control means for the second-stage cracking coil comprising a Venturi injector directly communicating with the vaporizing coil and projecting within said second-stage cracking coil.

4. A dual two-stage cracking apparatus for hydrocarbon oils, which comprises a furnace divided by a division wall into two heating sections, another wall in each section dividing the same into combustion and convection areas permitting the passage of gases from the combustion area to the convection area, a vaporizing coil at the lower portion of the convection area of each heating section, means for leading a hydrocarbon oil charging stock to said vaporizing coil, a secondstage cracking coil disposed above each vaporizing coil, a first-stage cracking coil in each combustion area and communicating with and receiving vapors from the appropriate vaporizing coil, said first-stage cracking coil communicating with and discharging vapors undergoing cracking reactions to the second-stage cracking coil, the diameter and length of the tubes comprising the first-stage cracking coil being less than that of the second-stage cracking coil whereby the vapors are expanded in the second-stage cracking coil, a steam superheater communicating with the appropriate vaporizing coil, means whereby steam may be led from said superheater to the first-stage cracking coils, heating means in each combustion section, and heat control means for the convection areas comprising a plurality of intercommunicating tubes disposed in said division wall between the two heating sections, adapted to receive a relatively cool fiow material and to lead the same to a vaporizing coil of the two above specified, jointly with the oil charging stock.

5. A dual two-stage cracking apparatus for hydrocarbon oils, which comprises a furnace divided by a division wall into two heating sections, another wall in each section dividing the same into combustion and convection areas permitting the passage of gases from the combustion area to the convection area, a vaporizing coil at the lower portion of the convection area of each heating section, means for leading a hydrocarbon oil charging stock to said vaporizing coil, a secondstage cracking coil disposed above each vaporizing coil, a first-stage cracking coil in each combustion area and communicating with and receiving vapors from the appropriate vaporizing coil, said first-stage cracking coil communicating with and discharging vapors undergoing cracking reactions to the second-stage cracking coil, the diameter and length of the tube comprising the first-stage cracking coil being less than that of the second-stage cracking coil whereby the vapors are expanded in the second-stage cracking coil, a steam superheater communicating with the appropriate vaporizing coil, means whereby steam may be led from said superheater to the first-stage cracking coil, heating means in each combustion section, and a plurality of intercommunicating tubes disposed in said division wall at the upper part thereof opposite the second-stage cracking coils, and means for passing hydrogenous gas through said intercommunicating tubes and to the vaporizing coils.

ERNEST A. OCON.

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