US1818674A - Process and apparatus for converting hydrocarbons - Google Patents

Description

Aug. 11, 1931. cno 1,818,674

PROCESS AND APPARATUS FOR CONVERTING HYDROCARBONS Filed March 11 1925 lira/1 Page I coils flea/1719' INVENTOR; V

- v jwfylfd ATTORNEY.

Patented Aug. 11, 1931 PATENT orrrce WALTER CROSS, 'DF KANSAS .MISSOURI, ASSIGND R, BY MESNE ASSIGNMENTS,

'HO GASOLINE PEEMMINUCIS 'GQMZPANX, INC OF WILMINGTON, DELAWARE, vA CORPO- QRATION OF DELAWARE PROCESS AND APPARATUS FOR CQNVER'DI'NG lHYDROCARIBONS Application filed March 11, 1925. Serial no; 14,642.

invention relates to improvements in a process. and apparatus for converting hydrocarbons, and refers more particularly to a process in which cracking stock "sub d j'edted' to conversion temperatures and high pressures during treatment, said. conditions being regiila'ted to effect the conversionof the oil in substantially the "liquid phase. The process "is preferably operated continuously 3:9 for the production of relatively light gasoline like .products from heavier-stocks such as gas oilfkerosene distillate, fuel oil, refinery s'lops or 'other'suitable cracking stocks.

Among the objects of "the invention are, to

15 provide a process in which the oil is'hea ted in afcoi-l .toa cracking temperature and is transferred while in a highly heated condition to a stage of conversion wherein it is collected in'a body and polymerization and cracking permitted to continue to'the desired extent,-

this heat and conversion taking place under high pressures, that is, su'flicient pressures that will prevent any substantial vaporize: tion during {the heating or cracking period; to provide a processin which the cracked 7 products are subsequently cooled on being withdrawn from the reaction stage and while in "a cool 'condition'the inert gases are sepa- I rated from the liquids and the cool cracked materi'alor what we choose to'term as'fcrude equivalent.or synthetic crude is returned and utilized as a cooling medium for the highly heated oil as it is discharged from the reaction stage, this acquired heat being sri'fii'cient to distill ofi' the lighter fractions 'from'the synthetic cru'de'whereby a liquid end point distillate may be obtained by "proper dephl'egmation and condensation; 'to provide a process, the novelty of which lies to a great extent in the cooling'of the synthetic or "cracked products and separating the gas from the hydrocarbon subsequent to cooling,v

thereafter returning the liquid synthetic crude to he reheated by the cracked products as they are discharged from the reaction stage in a highlyheated condition; to provide afn 'a'pjparatus "for carrying out this proccess and, in general to provide a process and apparatus hereinafter explained in more to detail.

The singlefigure is a diagrammatic side e'leyat-ional vie-wot the apparatus, with parts broken away and pa-rtsin section, in which the process maybe practiced, although it is recognized that similar "processes within the scope of the invention may 'be carried out in apparatuses 'of a different character withput departing from the spirit :ofthis invena Referring to the drawing, at 1 is shown a furnace preferably heated by means of gas burners diagrammatically shown at ilzn the furnace is mounted a continuous coil, the upper portion of which is designated as a preheating coil 3 and the lower bank, the heating coil 4. At 5 is shown a reaction chamber connected to the discharge ended the heating "coil by *a transfer line 6. The

which preferably of the bubble type 'as' shown diagrammatically in the broken away portion. A condenser '14 serves to liquery the overhead material iirom the top of the tower I3 conducted th ereto through the vapor line 15 and condenser coil 16 and at the same time "to cool the anvaporized material Withdrawn from the evaporator '11 through the line 17 and circulated. through the condenser box through the cooling coil 18; At 1 9 is a reflux condensate rebdi ler, whose function is to redist ill the lighter fractions by means of'hea t extracted from the reheat ed synthetic crude which; is circulated there through in a closed 'co i l shown at 2 0;'t he evolved vapors being returned to "the tower through the line '21;

Describing briefly. the mode of operation,

the charging stock is supplied to the system' through a line 122 and 'piump23. Thi'sstoc'k,

may be introduced being circulated through "a closed knock-back coil 24' posittionedin thc top of the tower, or may be bypassed automati'ca liy through the l ine '25 due to manipulationof a valve 26 by means o 'f anautomatictem'peraiture regula'torpos'i tioned in the top of the tower at the point of vapor exit designated as 27. This auto matic pressure regulator may be a thermostick which, through electrical connections shown diagrammatically, operates the valve 26 to bypass the charging stock when the temperature of the overhead vapors is reduced to the predetermined point. This charging stock, whether circulated through theknock-back coil or bvpassed through the line 25, is conducted through the line 28 to the suction side of the pump 29 from which it is discharged through the pipe 30 into the preheating coil 3, thence to the heating coil 4, and discharged in a cracking state into the reaction chamber 5. The conditions of heating in the cracking coil, that is, the velocity of the oil through the coil which constitutes the time factor of the heating and the degree of firing are properly controlled to prevent the accumulation of carbon deposition in the coils. These conditions are arrived at by proper temperature regulation, it being necessary to have sufficient heat in the oil to give an adequate yield after con version in the reaction, chamber 5, but such heating should not be excessive to produce objectionable carbon deposition in the coil. The reaction chamber is preferably fabricated of a single billet of steel forged to the desired shape on a mandrel, assuring the uniform texture throughout and a chamber which will withstand excessive temperatures and pressures. The usual size is approximately forty feet (40) long and four feet (4) in diameter. The end plates to the chamber are removable for cleaning purposes.

The oil, in its passage through the reaction chamber, is given suflicient time to consummate the conversion which was, initiated in the coil. The cracked products are removed through the discharge line 8 and passed through the heat exchanger which is heavily insulated to prevent loss of heat by radiation.

In its passage through the heat exchanger, the oil is introduced to the header 7, passing thence through the tubes 7 b into the header 0 at the opposite end of the exchanger and being discharged in a relatively cool state through the line 31 controlled by a valve 32 into the separator 9. The valve 32 may be utilized to eiiect any predetermined reduction of pressure on the oil; preferably this is reduced to substantially atmospheric pressure. It will be understood that in the heat exchanger 7, suflicient heat is abstracted from the synthetic crude to reduce it to such a temperature as will preclude vaporization of the lighter or gasoline-like fractions upon the subsequent reduction of pressure. In the gas separator the incondensable products, including such gases as methane, ethane and the like, are returned through the gas line 33 controlled by avalve 34 to the burners 2. During the initial stage of operation when the gas is insuh'icient to supply fuel to the burners, gas or fuel oil is introduced through the auxiliary line 35 regulated by a valve 36. The liquid material collected in the gas separator is automatically withdrawn through the line 37 by means of the liquid level regulator shown diagrammatically at 88. This liquid is discharged into the storage tank 10 from which it is recycled through the pipe 39 and pump 40 to the casing surrounding the heat exchanger by means of a line 41. By circulation about the tubes 7*, this cooling medium acquires the heat contained in the oil in the cracked products discharged from the reaction chamber, and subsequent to the acquisition of this heat it is directed through the line 12 into the closed coil 20 positioned in the reflux reboiler 19. In this stage, it gives up a portion of its heat to the reflux condensate hereinafter explained in more detail. The discharge 48 from the coil 20 is connected into the bottom of the evaporator 11 where the oil is permitted to expand,the lighter fractions passing off in the form of vapors which proceed through the vapor line 12 to the dephlegmator or refluxing tower 13. The unvaporized liquids are automatically withdrawn through the line 17, and after passing through the cooler 18 are conducted to storage. In the bottom of the evaporator is positioned a heating element such as a resistant element or electrode 44 heated by an electric current passed therethrough. It may be necessary to add heat at this point in the process according to the effectiveness of the heat exchange produced in the heat transfer element designated as 7. With certain types of oil,

the exchange is sufficient to eliminate the ad ditional heating in the evaporating tower, but provision is made in order to have a more efficient control of the operating conditions.

The vapors, passing overhead from the evaporator, are subjected to a dephlegmating action in the tower 13. The tower is of the well known bubble type wherein a series of vertically arranged pools of liquid oil serve as a percolating medium for the vapors. The condensate separated out in the respective pools gravitates downwardly in an opposed direction to the rising vapors. As previously described, the temperature of the overhead vapors passing off from the top of the tower is controlled by the automatic temperature regulator 27 which permits or prevents the flow of cool charging stock through the knockback coil 24. The vapors passing out through the top of the tower are directed to the line 15 and are liquefied in the coil 16, after which they are conducted to gasoline storage.

The reflux condensate which gravitate to automatic liquid level regulator 46 controlling the valve 47 in the draw off line 48. This level regulator maintains a liquid level which keeps the closed heating coil 20 immersed in the condensate. Thus, sufiicient heat is transferred to the liquid body, driving ofl the vapors through the line 21 back to the tower 13 to be retreated with the vapors from the evaporator 11. The unvaporized material discharged through the line 48 returns to the suction side of the pump 29 and is combined with the charging stock to be recycled through the system for retreatment.

It is desirable to maintain the highly heated cracked products discharged from the reaction chamber at the pressure of the reaction chamber up to their discharge in a cooled condition from the heat exchanger. It is a well known fact that a better heat exchange can be effected by a liquid product than by a vapor. As an illustrative run on a process of this character, temperatures of from 600 used in the heating coil. Normally, the discharge temperature from the coil is in the neighborhood of from 750 F. to 900 F., depending upon the character of the oil treated. A loss of heat of from 50 F. to 100 F. will take place in the reaction chamber in spite of the fact that it is heavily insulated. Pressures in the heating and reaction zones will normally range from 500 to 1500 pounds per square inch,-normal operating conditions being from 600 to 800 pounds per square inch. In starting the plant the storage tank 10 should be partially filled in order that there will be a cool medium to be recycled to take up the heat of the cracked products as they are discharged from the reaction stage.

Particular advantages of this type of operation lie in the fact that the cooling of the synthetic crude in this manner permits a somewhat more complete polymerizing efiect in the crude equivalent, and further, the separation of the gas prior to its redistillation removes from the hydrocarbon products a considerable volume of volatile material which is relatively inert to the selective fract-ionations to which the vapors are subjected during the dephlegmating and refluxing treatment. The presence of these inert gases in the vapors necessitates a larger tower construction in order to properly treat the increasing volume,a considerable portion of which is unaffected by dephlegmation. By removing these gases prior to redistillation, the volume of the vapors formed on redistil- V lation is reduced to an extent that the size of the tower construction may be considerably decreased, thereby reducing the construction costs. In fact, both the evaporator and tower construction which comprises the re-v distilling units may be reduced in size, decreasing further the constructional expense.

F.to 1,000 F. are

This eliminationof the vapor contamination by relatively inert gases is of considerable importance in the, effectiveness of the treatment of the evolved vapors distilled from the synthetic crude.

I claim as my invention:

1. A process for converting hydrocarbons, comprising the steps of heating and digesting the oil at relatively hi h temperatures and pressures, withdrawing the cracked products while in a highly heatedcondition, cooling said cracked products in a heat exchanger stage and utilizing the heat given up in the heat exchanger stage to reheat the cooled products to a temperature sufficient to distill 'ofi the lighter constituents, passing said reheated products to stages of vaporization, 'dephlegmation and final condensation serially connected, utilizing a portion of the heat of the reheated oil to revaporize the oil constituents separated out during d'ephlegmation.

2. A process for converting hydrocarbons, comprising the steps of heating and digesting oil at high temperatures and pressures, passing the cracked oil in the highly heated condition through a cooling stage, separating the incondensable gas therefrom and recycling the cooled cracked oil to the cooling stage and there utilizing it as a medium-to extract the heatfrom the cracked products, whereby it is raised to a distilling temperature, passing the reheated oil to and through evaporating, refluxing and condensing stages, and redistilling the condensate separated out in therefluxing stage by heat applied from the reheated oil prior to its introduction to the evaporating stage.

3. A process of converting hydrocarbon oil comprising heating and digesting the oilat relatively high temperatures and pressures, withdrawing the products of conversion in a highly heated condition and pass ing them through a heat exchanging stage and then through a gas separating stage maintained at a lower pressure than the heat exchanger; passing the liquid products recovered from the separating stage through ti'onship to the hot products of conversion,

then evaporating the reheated products of conversion, refluxing the vapors, passing refluxcondensate in heat exchange relationship wlth the reheated llquid products from the separating stage, takingofl vapors, re-

the entire exchanger in'heat transfer 'rela 5 densate separated out in the idephlegmating ing stage,.reducing:the pressure onthe cooled products in a gas separating stage, Withdrawing the separated liquid products and passing them through the heat exchanger to abstract heat from the liquid products of conversion, then evaporating the reheated products of conversion, refluxing the vapors, redistilling reflux LCOIldBIlSfltB !by heat ex change with the reheated separated liquid products and recyclingirefiux bottoms to the heating and digesting means.

5. :In an apparatus [forconverting hydrocarbons, the combination with means for cracking oil "WithOUt substantial vaporization, comprising heating, digesting, evaporating,-dephlegmating and condensing means serially'connected, of a -heat exchanger and separator interposed between the digesting and evaporating means'and in fluid communication therewith, said heat exchanger be ing connected to the digesting means and adapted to cool the cracked oil and reheat the cooled separated oil and means connected to theexchanger'adapted to redistill the reflux condensate discharged from the-dephlegmating-means.

'6. ,Inan apparatus for converting hydrocarbons, a combination with means for cracking oil without substantial vaporization comprising heating, digesting, evapo rating, dephlegmating and condensing means seriallyconnected, of a heat exchanger interposed in the discharge line from the digestion means and adapted to vcool the cracked oil prior to gas separation and to reheatthe cooled oil directed therethrough, and separate means connected with the exchanger for utilizing a portion of the heat of the reheated oil for redistilling the con means.

7. A process'of converting hydrocarbon oil comprising, passing ,oil in heat exchange relationship with hot vapors to :preheat the oil, then further heating and digesting the oil at relativelyhigh temperaturesnnd pressures, Withdrawing the products of conversion in a highly heated condition and passingthem through a heat exchanging stage and then through a gas separating stage maintained at a lower pressure'than the heat exchanging stage; passing the liquid products recovered from the separating stage through a :heat exchanging stage in heat transfer @relationship to the hot products of conversion, then evaporating the reheated products-of conversion, refluxlng the vapors, passlng the reflux condensate in heat vexchange with the reheated liquid products from the separating stage, taking-oil vapors therefrom and recyclmg'a POItIOII'OfthG refiu-x bottoms to :the converslon sta e.

WALTER M. dnoss.

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