US2160239A - Art of converting hydrocarbons - Google Patents

Description

May 30. 1939- v@ vooRHEEs 2,160,239

4 ART OF CONVERTING HYDROCARBONS Filed .July llO, 1934 2 Sheets-Sheet l May 30, 1939. v. vooRHEl-:s

ART OF CONVERTING HYDROCARBONS 2 Sheets-Sheet 2 Filed July lO, 1934 m m m m VNERVEER VUM/455.1' BYm a. 71M

ATTORNEY Patented May 30, 1939 so STATES ATT ori-*ie p andere Amr or ooNvER'rnro t v noofrnnons Vanderveen' Voorhees, Haond, Ind., assignor to Standard Oil Company (Indiana), Chicago, lli., a. corporation of Indiana Application July 10, i934, Serial No. 734,445

3 Claims.

lo ature of the hydrocarbon under treatment to the desired elevated temperature in a relatively short period of time. The molten material may be heated to the desired elevated temperature, in any suitable manner, such as by passing it either in indirect or direct heat exchange relation with hot combustion gases or by passing it in both direct and indirect heat exchange relation therewith. The thus heated molten material may then be conducted to an enlarged chamber wherein it is maintained in heat .exchange relation with a plurality of tubes of relatively small internal diameter therein.

l 'I'he plurality of tubes having a relatively small internal diameter or cross-sectional area within the enlarged chamber and in heat exchange relation with the molten material therein may be connected together to form a plurality of parallel paths for the hydrocarbon-to be rapidly raised to the desired elevated temperature. If desired, each of the parallel paths may comprise a plurality of tubes connected in series, or all of the tubes may be connected in parallel to form the plurality of parallel paths.

A hydrocarbon iluid-to be rapidly raised to the desired'elevated temperature may be preheated, as for example, by combustion gases produced in the furnace setting vand the thus preheated fluid introduced into the tubes of relatively small internal diameter to flow therethrough in the parallel paths.

By providing a plurality of small internal diameter tubes in heat exchange relation with the molten material, a large ratio of heating surface l to hydrocarbon uid volume is made possible. Thus, it will be evident that by dividing the main stream or streams of preheated hydrocarbon iiuid into a number of smaller streams, more heating surface is provided for the small quantity of hydrocarbon fluid passing through each path with the advantageous result that the hydrocarbon uid is rapidly heated to the desired elevated temperature in a relatively short period of time. Moreover, by having the small diameter tubes in heat exchange relation with the molten material, such as being immersed therein, local (Ci. ISG-) overheating of any one part of the tube surface is prevented, which-arrangement also permits of 'imparting large quantities of heat to the fluid being treated without a detrimental temperature gradient between the tube wall and the 5 molten material.

Rapid heating of hydrocarbon iiuids is quite desirable in that secondary reactions, which occur upon prolonged conversion of the uid, are

obviated with the result that the formation of l0` tar and gas, and particularly tar, is decreased while more gasoline is produced. This is especially true when converting a higher boiling oil into a lower boiling one, such as gasoline.

My invention also provides for the elimination 15 of the heretofore detrimental low temperature cracking in that the hydrocarbon uid to be converted is preferably preheated to a temperature short of active cracking and the thus preheated stream divided into a plurality of smaller streams 20 passing in heat exchange relation with the'iiuid heating medium whereby it is possible to rapidly raise each of theplurality of streams of oil to a high cracking temperature without the disadvantages inherent to the heretofore practiced 25' prolonged low temperature cracking of hydrocarbon iluid. By eliminating prolonged lowtemperature cracking of the-hydrocarbon iiuid, a greater proportion of. gasoline is produced, as heretofore pointed out, and the thus produced 30 gasoline is much superior to that produced in prolonged low temperature cracking in that desirable anti-knock properties are imparted to the hydrocarbon fluid in heating it to a high temperature in a relatively short period of time. 35 The heated hydrocarbon fluid upon leaving the tubes in heat exchange relation with the molten material may be immediately quenched and passed to an evaporator or other suitable apparatus for further treatment in a conventional 40y manner or may be soaked at conversion temperature prior to quenching. The .molten material, after passing in heat exchange relation with the hydrocarbon fluid owing through the tubes and preferably in4 counter current relation to the 45 flow of the hydrocarbon fluid, may be conducted from the enlarged chamber and returned tothe heating zone where it is again heated to an elevatedV temperature.

Comparable results may also be accomplished 5' in accordance with my invention by passing the molten material in counter current direct heat -exchange relationwit-h vaporous hydrocarbons.

Thus hydrocarbons, preferably in vapor form, may be introduced i'nto the lower portion of an 55 `made possibw, with the Aresult that hy carbon 'vapors are to the desired eleva i temperature in a reiativeiyshort period of in order to make my invention more cle l y" understood,

have shown in the accompanying drawings, means for carrying the same into practical effect without limiting the improvements in their useful applications to the particular constructions which, for the purpose of explanation, have been made the subject of illustration.

`Figure i is `an elevational view, partly in section, of an apparatus capable of carrying out my invention.

Figure 2 is a sectional view taken along lines iii-Z of Figure l.

Figure 3 is a modified form of construction that may be used in lieu of the structure shown in Figure 2. y

Figure i is an elevational view, partly in section, of a modification that may be used for the right hand side of Figure i.

Referring to the drawings and more particularly to Figure l., there is shown a furnace setting l, having a combustion chamber 2 and a convection heating chamber 3 separated from each other by a bridge wall l. The combustion chamber il may be provided with a plurality of burners suitably positioned in the lower portion thereof and adapted to burn any suitable fuel to produce hot products of combustion for the furnace setting.

A supply tank 6, having molten material therein, may be positioned in the upper portion of the combustion chamber and may be provided with an overflow pipe 1 at one end thereof. The molten material from the supply tank overflows` through the pipe l' and may' be conducted due to gravity into a suitable wall trough 9 extending along one Wall, for instance the back wall, of the furnace. In accordance with my invention, the molten material may be caused to flow spirally around the four walls of the furnace due to gravity and thereafter collected in a suitable reservoir. The trough 9 may therefore be slightly inclined to accomplish the gravity fiow of the molten material therein and at the lower end thereof, another similar trough II, extending along the bridge Wall 4, is suitably connected thereto to form a continuous path for the molten material. The trough II is likewise inclined to accomplish the flow of molten material and connected to' a similarly inclined trough extending along the front Wall of the furnace, not shown, which in turn is connected to another similarly inclined trough I2 extending along the end wall of the furnace. The troughs extending along each Wall are suitably spaced from each other to ab'sorb radiant heat which strikes the Walls of the furnace and extend from an upper part of the combustion chamber 2 to a lower part thereof, thereby forming a spiral path for the molten material. The molten material is thus passed from trough to trough throughout substantially all of the combustion chamber and may be colv lected in a suitable reservoir I3 positioned in the lower portion of the combustion chamber,

A@duced into t i and pass upwardly therethrough co and-indirectly to the molten material desee ling the combustion chamber oy means of spirally arranged troughs. Thus, the molt iai collected in each of the troughs l l g from one to another is subjected to the absorbed by the troughs as well as the absorbed directly by the molten material. Plesired, the molten material may be passed through a coil the combustion chamber to be heated by indirect heat exchange with the hot gases,

or it may be heated entirely by direct contact upon contact and produce a slag. Where the molten material consists of a salt which is brought into direct contact with the oil undergoing cracking as hereinafter described, it may be advisable to employ a sufficient excess of air to free the salt from any organic material, coke, etc. which may be carried with it.

The thus highly heated molten material collected in the reservoir i3 may be conducted therefrom through a suitable passage it in the bridge wall d to a conduit it provided at one end thereof with an inlet pressure pipe il. As shown in Figure l, a venturi arrangement i5 may be provided for raising the molten material through the conduit iB. The molten material thus conducted through the passage I6 into the conduit it may be lifted or raised therein by a suitable inert uid under high pressure introduced through the pipe il. The inert iiuid under high pressure, which may be highly superheated steam, a suitable gas such as hot combustion gases or high pressure gas from a cracking operation, for example, after fractionating out gasoline, lifts or raises the molten material through the conduit I8 into an elevated tank I9 in an upper portion of the furnace setting. If desired, in lieu of an inert fluid for lifting or raising the molten material to the elevated tank I9, any other suitable means, such as a pump, may be employed. The tank i9 may be provided with a vent pipe 2I, controlled by a suitable valve 20, for conducting the inert fluid used' to lift or raise the molten material from the tank I5. While the conduit i8 has been shown to the right of the bridge Wall, it may be positioned to the left thereof and directly in the molten material collected in the reservoir I3.

The tank I9 is adapted to collect a body of highly heated molten material therein which overflows through a conduit 22 into one end of an enlarged chamber 23, as more clearly shown in Figure 2. The molten material, which preferably lls the enlarged chamber 23 is conducted therefrom into a similar chamber 24'positioned directly therebelow through a conduit 25 at the end opposite the end in which the molten material is introduced into the enlarged chamber 23. Both of the chambers 23 and 24 are preferably maintained full of highly heated molten material which is utilized as a heat transfer medium for imparting the desired heat to hydroamazes carbon fluids to be converted, as will now beV described.

A hydrocarbon uid to be converted, such as a cleangas oil for example, may be introduced through a. line 26 and forced by means of a pump 2l through a preheating coil 28 positioned in the lower portion of the convection heating chamber 3 receiving combustion gases from the combustion chamber 2. The hydrocarbon fluid in passing through the preheating coil 28 may be raised to a temperature short of active cracking and may be conducted by means of a line 29 into a manifold 3l. The enlarged chambers 24 and 23 are provided respectively, with a plurality of tubes 3d and 36 of relatively small internal diameter. The tubes in each chamber may be connected together so as to form a plurality of parallel paths, the separate paths being identified by the numerals 38 and 36 with appropriate exponents as shown in Figure l. Theindividual tubes of each layer within the enlarged chambers may be connected in series, the tubes 34 of each layer being connected to the manifold Si by a number of tubes 32, the number of tubes 32 depending on the number of parallel paths formed within the enlarged chamber 24. The plurality of parallel streams of hydrocarbon iluid after passing in heat exchange with molten material within the enlarged chamber 24, preferably accomplished by completely immersing all of the tubes 3E in the molten material, are conducted by tubes 35, the number thereof depending upon the number of parallel paths, into similar parallel paths formed by the tubes 36 in the' enlarged chamber 23. The hydrocarbon fluid after passing through the parallel paths formed by the tubes 36 in heat exchange relation with molten material in the enlarged chamber 23 is conducted by means of a plurality of pipes 31, each controlled by a suitable valve 38, into a manifold 39 from which the heated hydrocarbon fluid is conducted by means of a pipe 4l, controlled by a valve 42, to any suitable` apparatus for further treatment.

The molten material from the enlarged chamber 24 ilows through a conduit 43 into the molten material supply tank 6. As shown in Figure l, the head of molten material maintained in the tank I9 is at a higher elevation than the level of molten material maintained in the supply tank 6 with the result that the molten material,

which occupies substantially the entire free area between the tank I9 and the supply tank 6, is forced into the supply tank v6 without the aid of pumps or the like. If desired any suitable means, such as a pump, may be provided for returning the molten material to the supply tank 6 from which it is passed through the combustion chamber 2 to be reheated.

In accordance with my invention there is provided an arrangement whereby it is possible to increase the ratio of heating surface to hydrocarbon fluid volume to a great extent to aecomplish rapid heating of the hydrocarbon fluid to the desired elevated temperature. As shown in Figure l, the hydrocarbon fluid entering the manifold 3l is divided into a plurality of parallel paths, each of which' is of considerably smaller internal diameter than thus dividing the oil into a plurality of paths and passing it through the tubes 34 and 36 immersed in the molten material in the chambers 24 and 23, intimate contact between the molten material and the tubes is thus obtained to accomplish the advantageous results heretofore pointed out.

-are heated indirectly,

, the two chambers shown in with this modification,

the preheating coll. By y In quick cracking it is essential to obtain the maximum area of contact between the hydrocarbon oil and the heating surfaces in proportion to the volume of the oil being treated. In order to use small tubes in practical cracking plant operation it is necessary to operate them in parallel flow in order to obtain any reasonable capacity and reduce the pressures required to force the oil through the furnace. In attempting to carry out this operation in conventional heating equipment by decreasing the diameter of the heating tubes, great difficulty has been encountered with coke formation in the tubes, stopping the ow of oil and resulting in failure of the4 tubes. According to my invention, by which the small tubes it is possible to control the temperature within very much narrower limits than is the case in conventional direct red tube heaters. The temperature gradient between the molten heattransfermaterial and the oil tubes is relatively very small, due largely to the heat conductivity of the molten material used. This gradient may amount to only 50 to 200 F., whereas in direct iired heaters the temperature gradient may be as much as 1000 F. With such a low temperature gradient between the heating fluid and the tubes there is substantially no dimculty from local overheating and coking and should coking occur there is no danger of tube failure since the temperature of the heating fluid is not sufficiently high to bring about this undesirable condition. v

In Figure 3, there is shown a modified form of enlarged chamber that may be used in lieu of Figures 1 and 2. It is to be understood, of course, that only one enlarged chamber may be used in accordance with my invention as illustrated in Figure l and `where the expression enlarged chamber appears inthe appended claims, it isintended that such expression covers either one or more enlarged chambers, more especially either of the type of chambers 4shown in Figure 2 or Figure 3. Referring to Figure 3,-there is shown an enlarged chamberl 45 provided with a plurality of internal baffles 46 arranged in such a manner as to cause molten material introduced through an inlet line '41 to follow a tortuous path through the enlarged chamber 45 to a suitable outlet 48. In accordance a stream of hydrocarbon iluid, preheated if desired, may be introduced through a line 49 into a manifold 5|. The manifold I may be connected to a plurality of tubes 52 of relatively small internal diameter and the oil introduced into the manifold 5I thus divided into a p`urality of streams of relatively small cross-sectional area to be passed through the parallel tubes 52 immersed in Imolten material within the enlarged chamber 45 to a header 53,. the heated OiLentering the header 53 being conducted through an outlet line 54 to suitable apparatus for further treatment in any well known manner.

By the arrangement shown in Figure 3 the hydrocarbon fluid to be rapidly heated is passed in a plurality of streams in ccuntercurrent heat exchange-relation with the flow of molten material through the enlarged chamber 45 around the baiiles 46. Thus rapid heating of the hydrocarbon fluid is accomplished, as before described, and in Aactuel operation it is preferred to accomplish the rapid heating of the fluid in an varrangement comparable with that shown in' Figure 3, although countercurrent flow of hydrocarbon uid and moiten material may be accomplished heating of the hydrocarbon el ect conact between it and highly heat n mateal. FEhe arrangement to the left e bridge vall l shown in Figure l has been omitted from Figure l as being unnecessary for a proper understanding oi this modification, any suitable heating arrangement for the molten material, as above described, being applicable.

Referring more specifically to Il, there is provided an enlarged chamber having a plurality of downwardly extending battles therein for causing `fluids passing therethrough to follow a tortuous path around 'the baffles. in accordance with this modication, a stream of hydrocarbon uid, such as a clean gas oil, to be converted may be introduced through a pipe 5l and oi-ced through a preheating coil receiving combustion gases from the combustion chamber The stream of hydrocarbon fluid passing through the preheating coil 50 is raised to a temperature su'ciently high to preferably effect vaporization thereoi and the thus. vaporized huid may be introduced through a pipe into the lower portion of the enlarged chamber Molten material is simultaneously introduced into the upper portion of the chamber 55 by means of the pipe which in this modification may be provided with a trap leg as illustrated, and caused to flow downwardly through the enlarged chamber 55 over and around the baffles 5t therein. The vaporous hydrocarbon introduced into the lower portion of the enlarged chamber 55 through the line 59 rises in the enlarged chamber 55 in countercurrent heat exchange relation with the downwardly owing molten material and due to the direct heat exchange between the two fluids in the enlarged chamber 55, the vaporous hydrocarbon fluid is rapidly raised to the desired conversion temperature and conducted from the enlarged chamber 55, by means of a suitable outlet pipe 5l. Both the downwardly flowing molten material and the upwardly rising vaporous hydrocarbon tend to spread out throughout the entire space within the enlarged chamber 55 with the result that a large ratio of heating surface, in this instance direct contact with molten material, to hydrocarbon iluid volume is accomplished which permits of rapid heating of the hydrocarbon fluid.

The molten material after passing in heat exchange relation with the upwardly rising vaporous hydrocarbon may be withdrawn through a conduit 62 and forced by means of a pump 63 to the molten material supply tank 6.

The various elements within the furnace setting l have been shown rather diagrammatically and it is to be clearly understood that their arrangement and the relative position of each may be varied without departing from the scope of my invention. It is preferred to position certain of the elements, such as the tanks E and I9 as well as the conduits connected to these tanks against one wall of the furnace'to thereby prevent any unnecessary obstruction to the ilow of hot products of combustion .from the combustion chamber into the convection heating 'chamber 3. The tubes connecting the tubes 36 and 34 in the eneconomic operation in that these elaineL r a: ened against one e will be evident t all of the elements a the furnace setting which cf-Jr' lf intensive -at, inclu-ding convection arid/ or radiant heat, vhich aids in preventing l" at from the various parts the syster understood, however, that my inventa...- be carried out without arranging ail of the various elements within the same furnace setting and obviously some of the elements do not have to be swept or .heated by the hot combustion gases and may be suitably lagged to prevent loss oi' heat.

When applying my invention to the cracking oi oi a relatively clean gas oil, for instance, the oil may be preheated in passing through the heating coil to a temperature as high as about 800 F. or to a temperature just below the active cracking temperature of the particular oil being heated. The thus preheatedoil may be conducted to the manifold Si, Figure l, or the manifold 5i, Figure 3, and passed in a plurality of parallel paths through the tubes of relatively small internal diameter connected to the manifold. The molten material collected in the reservoir i3 may be at a temperature of about from 1150 to l300 F. and conducte-d through the conduit l and tank i9 to the enlarged chambers 23 and 26, or the enlarged chamber @l of Figure 3, at a temperature substantially the same as that attained during the heating thereof or at a slightly lower temperature. The tubes forming the plurality of parallel paths for the oil are immersed in the molten material and arein direct heat exchange relation therewith. in accordance with my invention. these tubes are of relatively small internal'diameter such as from about 1/8 to SA," and preferably about or l" internal diameter. The oil is passed through the plurality of tubes immersed in the molten material in` a relatively short period of time, preierably less than seconds, and most advantageously in about two to twenty seconds. The oil in passing through the small internal diameter tubes is rapidly raised to the desired temperature and passed through the tubes while in the active cracking range in a relatively short period of time as above mentioned. It is preferable to keep the temperature of the oil going up and this is efiiciently accomplished by the countercurrent flow of the molten material with respect to the oil being converted. The oil is thus rapidly heated to a high temperature of about 1100u to 1300 F. and conducted through either the line 4I of Figure l, or the line 5B of Figure 3, to suitable equipment, such as an evaporator,v for further treatment. It is preferable in operating in this manner to quench the oil in passing through either the line 4I or 54 before reaching the after equipment or if desired, the products may be soaked at cracking temperature before quenching them.

Any suitable pressures may be maintained on the oil being heated. For instance, pressures ranging from approximately atmospheric to as much as 1000 pounds per square inch, or higher, may be maintained on the oil passing through the heating conduits, the selected pressure being reduced after leaving the heating coil by a suitable pressure reduction valve.

While my invention has been specically deis to bel Der, means scribed in connection with the cr:` f of a relatively clean gas oil, it is to be clear-ly understood that other hydrocarbon uids may also be thermally converted in accordance therewith. For instance, my invention is also applicable to the thermal conversion of normally gaseous saturated hydrocarbons, for the production of gaseous olens or normally liquid products, and when practicing it in such a manner, temperatures above 1300 and as high as l600 F. and higher and lower pressures may be employed.

Any suitable molten material may be uscd in accordance with my invention. For instance, molten lead, or other suitable metal, or any suitable alloy of various metals, or fused salts 'such as sodium hydroxide or a mixture ci fused salts such as sodium and aluminum chloride may be employed. The expression molten material" used throughout the speciiication and claims is intended to include any suitable metal, alloylof various metals, salts or mixtures of variou's salts.

While I have shown and described the preferred embodiment f my invention, I wish it to be understood that I do not confine myself to the precise details or construction herein set forth, by way of illustration, as it is apparent that many changes and variations may be made therein, by those skilled in the art, without departing from the spirit of theinvention or exceedng the scope of the appended claims.

What I claim is: 1. An apparatus for the heat treatment of hydrocarbons which comprises a combustion chamfor producing hot products of combuston therefor, means 'within said combustion chamber to enable the heating of molten'material partly by direct'contact with products of combustion and partly 'by indirect contact therewith, an enlarged chamber, means for conducting heated molten vmaterial to said enlarged chamber, a plurality of conduit elements within said enlarged chamber in heat exchange relation with molten material therein, said conduit elements being connected to form a plurality of parallel paths, means for introducing hydrocarbon into said conduits whe i it is Apassed in the plurality of parallel paths in heat exchange relation with the molten material and rapidly raised to an elevated temperature and me for passing the thus heated hy-i from said conduits.

2. An apparatus for the heat treatment-of hy- 'drocarbons which comprises a combustion chamber, means for producing hot products of combastion therefor, means within said combustion chamber to enable the heating of molten material ly by direct contact `with products of combustion and partly by indirect contact therewith, an enlarged chamber having baies therein, means for conducting heated molten material to said enlarged chamber, means for introducing hydrocarbons into lsaid chamber to thereby cause said hydrocarbons to dow aroundsaid balles in the' enlarged chamber and in countercurrent heat exchange relation with molten material introduced into said chamber, and means for withdrawing the heated hydrocarbons and molten material after passing in heat exchange with each other.

3. The method of heating hydrocarbon uids in an apparatus comprising, a combustion chamber and a reaction chamber separate therefrom which comprises flowing molten material in a stream in the combustion chamber in both direct and indirect contact with heated combustion gases therein to thereby raise the molten material to an elevated temperature, delivering the thus heated molten material to said reaction chamber, introducing .hydrocarbon fluid into said reaction chamber and passing said hydrocarbon fluid in a plurality of parallel paths in indirect heat exchange relation with the molten material to rapidly raise said hydrocarbon uid to an eleo vated temperature.

VANDERVm VOORI-IEES.

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