US1944318A - Oil heater - Google Patents

Description

Jan. 23, 1934. A. E. HARNsBr-:RGER ET AL 1,944,318

om HEATER Fil'ed Nov. 25. v 1951 2 Sheets-Sheet l w gx @L 157m z ZL' Jan. 23, 1934.

A. E. HARNSBERGER. Er AL. 1,944,318

OIL HEATER Filed Nov. 25. 1931 2 Sheets-Sheet 2 j'nuewtoud l Q 'mit Efrwbefger Patented Jan. 23; 1934 Fris OIL HEATER Audley E. Hamsberger and Clyde L. Smith, Chi cago, Ill., assignors to The Pure Oil Company, Chicago, Ill., a corporation oi Ohio Application November 25, i931 Serial No. 577,309

' claims. (ci. iss- 116) This invention relates to improvements tubular heaters of the type employed in the heat treatment of hydrocarbon oils for purposes of eiecting distillation, cracking, polymerizing or otherwise treating' hydrocarbon oil passed through the heater, whereby to eiect changes in the physical or chemical properties of the oil so heated. i The invention has specic reference to a tubular heater which vhas been particularly adapted for use in connection with high temperature oil cracking systems and embodies the provision of means for continuously passing vaporized streams of oil through a plurality of substantially horizontally arranged tube banks provided in the heating section of the still, and wherein provision is made for securing eicent heat transfer between the oils passing through the tubes of the still and the furnace gases to the end of providing an oil heater economical and eiilcient in its construction and operation, one wherein repairs and adjustments can be made with facility and one wherein provision is made in the arrangement and form of the tubes of the heater and the flow of oil through said tubes to secure sustained operation without permitting of undue coke or carbon accumulations in the oil passages of the tubes.

In vapor phaseoil cracking stills of the tubular type, considerable difficulty has been encountered in securing emcient and economical designs by which carbon accumulation in the tubes can be reduced to a minimum degree to avoid interference with the continued operation ofthe still for extended runs or periods of operation ,and to reduce repair and maintenance costs. A vapor phase converter is required to operate at high temperatures since to effect the desired cracking reactions, it is necessary that the oil passed through the heater be heated to a temperature varying between 1000 F. and 1150 F. This means high furnace gas Atemperatures which latter temperatures are suniciently high so that if there is any interference in the matter of heat transfer between the furnace gases and the oils undergoing heating in the tubes, such as by obstructing carbon deposit in the tubes, the metal of the obstructed tubes is rapidly deteriorated by the lack of heat transfer and the excessive heating of the metal to temperatures where the tube or tubes so affected breaks down or ruptures.

In accordance with the present invention, we

have provided an oil heater of the character specified wherein the oil undergoing heating is positively advanced in serial flow through a. plurality of connected tubes arranged in the heating section of the still and wherein an equalized ow of oil vapor passes through each of said tubes so that proper heat exchange exists between all portions of the still tubes and the furnace gases developed in the still.

With these and other objects in View, which will appear as the description proceeds, the invention consists in the novel features of construe et tion, combination of elements and arrangements of parts hereinafter fully described and pointed out in the appended claims.

In the accompanying drawings: K

Fig. l is a vertical longitudinal sectional View m taken through an oil heater constructed in accordance with the features of the present invention;

Fig. 2 is a view in rear elevation of the heater and disclosing the distributing pipes for delivg5 ering oil to the converting tubes of the heater;

Fig. 3 is a horizontal sectional view taken through the upper portion of the heater online 3 3 of Fig. 1 and disclosing in plan the arrangement of the rst pass of converting tubes g@ provided in the heaten.A

Referring more particularly to the drawings, the numeral l designates the wall struc-ture of my improved oil heater or converter. The wall structure may be formed from the usualrefrac- 35 tory materials to provide a heat retaining enclosure. The converter is provided with a trans= versely arrangedbridge wall 2, ldisposed to divide the interior thereof into combustion andtube chambers 3 and d respectively. The combustion Q@ chamber is provided with a Dutch oven formation 5 in which is arranged one or more main burners 5 by which the internal temperatures of the converter are obtained through the development of. combustion gases.rIihe compartments 3 and i 95 communicate with each other over the top of thevbridge wall 2 and the top oi the bridge wall is spaced and disposed below the roof 6 of the converter. By this arrangement, the furnace gases developed by the combustion of fuels discharged my@ nace gases are then passed through the'horizontal 05 outlet duct '7 and escape to the atmosphere by way of a vertical stack 8 of suitable height. Arranged in the duct 7 is a'bank of serialiy connected tubes 9 and the oil to be heated enters this bank of tubes by way of a pipe line l0 under im through the tubes 9, the temperature of the oil is raised suiciently to vaporize its lower boiling compounds but usually insufliciently to effect any material cracking of the oil` passing through this bank of tubes. Ordinarily, the tubes 9 are referred to as economizer tubessince said tubes are largely heated by the waste furnace gases issuing from the principal heating sections of the converter, although, if desired, additional .burners 11 may be provided to supplement the heat of the furnace gases generated by the operation of the burners 5' so that such waste furnace gases will possess a sufcient high temperature to secure the desired vaporization of the oils in the tubes 9. After the passage of the furnace gases over the tubes 9, said gases are led to the atmosphere through the stack 8.

From the outlet side of the bank of tubes 9, apipe 12 leads to an evaporator (not shown) where high boiling liquid oils, unvaporized in the tubes 9, are removed and the desired vaporized oils are then transmitted to a bank of serially connected' drying tubes indicated at 13 in the chamber 4 of the converter. It has been found in the operation of vapor phase converters that the vaporized oil should be in a substantially dry state and free from small liquid particles or mist before such vaporized oils enter the high temperature cracking sections of the converter tubes. The presence of liquid in the vapors results in carbon formation on the inner walls of the tubes. Apparently due to the high temperatures, this mist is rapidly evaporated to a point of dryness, leaving an objectionable carbon deposit which, if permitted to accumulate, obstructs or blocks proper vapor flow through the tubes. We therefore pass the vaporized oil, prior to its delivery to the high temperature cracking tubes, through what we term the drying tubes, which have been indicated at 13. The temperature of the furnace gases around thetubes 13 is such that it does not effect any appreciable cracking of the oil vapor iiowing`- through said tubes, although the temperature is sufficiently high to vaporize any liquid or mist of high boiling hydrocarbons present in the vapor. Thetubes 13 are of such diameter that if there is any carbon accumulation, vapor ow throughv the tubes is not seriously obstructed. For instance, these tubes may possess an internal diameter of approximately 12 inches and, moreover, are capable of being readily cleaned from positions exterior of the side walls of the converter in connection with which the tubes are supported.

From thetubes 13 the heated oil, now in a gaseous or vaporous condition and free from fine liquid particles, is transferred by way of apipe line 14 to amanifold 15 extending horizontally with respect to the converter and'disposed. contiguous to the top or roof of the converter adjacent toits rear wall. It will be understood that thepipe 14 and themanifold 15 are suitably covered with a heat 4insulating material to minimize loss in temperature of the heated oil vapors passed therethrough. The manifold 15- is provided with spaced dependingpipe members 16, each of which is provided with a control valve 17 which may be adjusted, in accordance with the indications of heat measuringinstruments (not shown) to obtain equalized delivery of oil) vapors to each of the pipe members. These pipe members extend vertically downwardly from themanifold 15, are lagged with heat insulating coverings and have their lower ends connected with a plurality of horizontally disposedtubes 18 which,

suitable pressure. During the serial flow ofthe oil collectively, constitute what may be termed the first pass of converter tubes. Thetubes 18 are connected with corresponding tubes comprising a plurality of groups as indicated at A, B, C and D, thetubes 18 of each group being united for the serial flow of oil vapor therethrough. The pressure on the oil vapor passing through thetubes 18 and related pipe members is preferably suiciently high to overcome pipe friction and provide for the necessary vapor velocities and in this connection use may be made of pressures of the order of 50 pounds per square inch, although it will be understood that this pressure is subject to considerable variation depending on the character of the cracking reactions desired.

Heretofore in converters of this character, thetubes 18 have had their inlet and outlet ends connected with adjoining inlet and outlet manifolds so that vapor flow through said tubes was effected in parallel or multiple streams with the vapor flowing in but a single direction. We have 0bserved however that when said tubes are arranged in multiple to provide the independently flowing parallel vapor streams, it is practically impossible to secure uniform distribution of the oil vapor to each of such tubes. Certain tubes invariably receive more oil vapor than the remaining tubes, with the result that the tubes through which an insufficient amount of oil vapor travels overheat, since there is not sufficient oil vapor present in those tubes to.conduct away from the walls of the tubes the heat imparted to the latter by the furnaces gases.` Again, obstructing deposits might accumulate in such tubes which is also the cause of or contributes to the overheating of tubes. In such high temperature furnaces, it is imperative that the proper rate of heat exchange take place between the furnace gases and the oils or oil vapors passing through the tubes.

If this rate or balance of heat exchange is impaired, overheating of the tubes as a direct consequence takes place, causing the tubes so affected 4 to break down structurally under the high temperatures of the furnace gases, and causing their short life. Tube failure results in necessitating the immediate discontinuance of the converting operations until repairs can be made, so, therefore, it is not only thecost of the defective tube or' tubes but the loss of theentire operation of the converter while the repairs are being made that makes such shut-downs so highly expensive and undesired. By providing for the serial flow of oil vapor through the various tubes of each of the groups A, B, C and D, we have provided a construction which insures a proper delivery of oil vapor and passage thereof through each of the tubes and in this way overcome one of the major objections to the parallel type of heater. 'Ihe tubes 18 are located in the high temperature region of the converter and are therefore subject to the greatest influences of destruction set up by the furnace gases. It is therefore of very considerable importance that these tubes should be protected as far as possible against destruction by the defective heat exchange. In certain instances, we have found it advisable to supplement the burners 5 by the use of roof burners 19 which we have found to be highly effective in quickly raising the temperature of the oilvapors entering thetubes 18 from a non-cracking temperature to a cracking temperature in excess of 1000 F. Thetubes 18 are approximately 6 inches in outside diameter to increase somewhat the velocity of the vapor travel therethrough in order that the oil vapor will rapidly attain a cracking lac temperature. tubes may or may not contain catalysts or cores but in the preferred embodiment of our invention, these tubes are plain and are not provided with internal cores vor other obstructions.

After the oil vapors attain the desired temperatures, which are usually in excess of l000 F., the cracked vapors leave the discharge tubes of the groups A, B, C and D and pass through heat insulated downwardly extendingbranches 20 to a correspondingly protected header or manifold 21 arranged below and extending parallel with a header or manifold ,15, in which the oil vapors discharged from the groups oftubes 18 are mingled and attain an equalized temperature. Since cracking is a function of i time and temperature and since comparatively high velocities obtain in thetubes 18, it is desirable to continue the conversion reactions in order to secure a desired yield of low boiling oils. This is obtained by passing the oil vapors from theheader 21 into the lower pass of a bank of seriallyconnected time tubes 22 which are arranged in the chamber 4 of the converter between the drying andconversion tubes 13 and 18. Thetubes 22 may possess an outside diameter of 12% inches to eiect a somewhat retarded rate of flow of the vapors as compared with their rate of flow in thesmaller tubes 18. In travelling through thetubes 22, the vapors ow generally in counter-current relationship to the descending furnace gases passing through the chamber 4 so that when the cracked vapors are discharged from theoutlet tube 22, they will possess a desired cracking temperature, which offsets loss of heat due to the endothermic character of an eil cracking reaction and also to compensate for the drop in temperature of the furnace gases following contact with heat absorbing surfaces. vapors discharged from thetubes 22 may then be shock chilled to arrest conversion reactions and subjected to the usual fractionation operations common in crack-ing of oils.

The various tubes employed in our converter are supported in conjunction with the walls of the converter setting and since adjacent tubes are connected for serial oil flow, the return bends'used in uniting adjacent tubes are located exteriorly of the converter walls. These return bends are provided with the usual threadedplugs 23 which may be removed to provide for the cleaning of any tubeor its independent removal from the converter and. substitutions therefor. Thetubes 18 extend longitudinally of the converter and are located over thechambers 3 and fl to receive Athe benefit of the furnace heat through radiation and convection, whereas thetubes 13 and 22 extend transversely of the converter at right angles to thetubes 18 and are located solely in the tube chamber 4.

In View of the foregoing, it will be seen that the present invention provides a converter peculiarly suitable for the vapor phase cracking of hydrocarbon oils and one wherein a novel arrangement of tubes is provided to insure sustained operation of the converter for prolonged periods under high furnace temperatures, to minimize premature destruction of the tubes through overheating and contributory causes, to minimize the deposition of carbon in the tubes and obstruction of vapor flow therethrough and the disadvantages of irnproper heat transfer and provides generally a converter in which repairs and adjustments can be made quickly and with facilitf The cracked gases communicating with the lower part of` the tube chamber, a plurality of independently regulable horizontally disposed tube coils supported at their ends by said wall structure and intermediately of their lengths by the bridge wall, said coils being arranged openly in said converter above the burner and tube chambers and below the roof of the converter, each of said coils being composed of a plurality of spaced parallel tubes through which oil vapor to be heated flows serially, a vapor manifold located exteriorly of said wall structure and operable to supply each of the independent tube coils with oil vapor whereby to cause the vapor to travel in serial flow through each of the tube coils and with multiple delivery of vapor simultaneously to each of the coils from said manifold, av second manifold disposed exteriorly of the wall structure of the converter into which oil streams heated in said tube coils and discharged therefrom are merged in a single stream, and a bank of serially united parallel 'tubes arranged openly in said tube chamber below the first-named tube coils and extending at right angles thereto and through which oil vapor heated in the multiple tube coils is passed following discharge in a merged stream from said second manifold.

2. In a converter for cracking oil in the vapor phase, a heat-confining wall structure arranged to provide burner and tube chambers spaced by an intervening bridge wail over the top of which said chambers communicate, combustion developing means arranged adjacent to the lower part of the burner chamber, an outlet duct for furnace gases communicating with the lower part of the tube chamber, a plurality of independently regulable horizontally disposed tube coils supported at their ends by said wall structure and intermediatelyof their lengths by the bridge wall, said coils being arranged openly in said converter above the burner and tube chambers arid; below the roof of the converter, each of said coils being composed of a plurality of spaced parallel tubes through which oil vapor to be heated flowsv serially, a vapor manifold located exteriorly ci' said wall structure and operable toy supply each of the independent tube coils with oil vapor whereby to cause the vapor to travel in serial flow through each of the tube coils and with multiple delivery of vapor simultaneously to each of the coils from said manifold, a second manifold disposed exteriorly of the wall structure of the converter into which oil streams heated in said tube coils and discharged therefrom are merged in a single stream, and a bank of serially united parallel tubes arranged openly in said tube chamber below the rst-named tube coils and extending at right angles thereto and through which ,oil vapor heated in the multiple tube coils is passed following discharge in a mergedstream from said second manifold, said last-named tubes being eachl lof greater cross sectional area than the corresponding area of each of the individual tubes found yin the tube coils.

3. In a converter for cracking oil in the vapor phase, a heat-confining wall structure arranged lll@ to provide burner and tube chambers spaced by rd.;

an intervening bridge wall over the top of which said chambers communicate, combustion developing means arranged adjacent to the lower part of the burner chamber, an outlet duct for fur-v nace gases communicating with the lower part of the tube chamber, a plurality of independently regulable horizontally disposed tube coils supported at their ends by said Wall structure and intermediately of their lengths by the bridge wall. said coils being arranged openly in said converter above the burner and tube chambers and below the roof of the converter, each of said coils being composed of a plurality of spaced parallel tubes through which oil vapor to be heated flows serially, a vapor manifold located exteriorly of said Wall structure and operable to supply each of the independent tube coils with oil vapor whereby ,to cause the vapor to travel in serial flow through each of the tube coils and with multiple delivery of vapor simultaneously to each of the coils from said manifold, a second manifold disposed exteriorly of the. wall structure of the. converter into which oil streams heated in said tube coils and discharged therefrom are merged in a single stream, a bank of serially united parallel tubes arranged openly in said tube chamber below the first-named tube coils and extending at right angles thereto and through which oil vapor heated in the multiple tube coils is passed following discharge in a merged stream from said second manifold, and a third bank of tubes arranged in the lower part of the tubechamber for preheating oil vapor prior to its delivery to said first-named manifold.

4. In-a converter for cracking oil in the vapor phase, a heat-confining wall structure arranged to provideburner and tube chambers spaced by an intervening bridge wall over the top of which said chambers communicate, combustion develop- -ing means arranged adjacent to the lower part of the burner chamber, an outlet duct for furnace gases communicating with the lower part of the tube chamber, 'a plurality of independently regulable horizontally disposed tube coils supported at their ends by said wall structure and intermediately of their lengths by the bridge wall, said coils being arranged openly in said converter above the burner and tube chambers and below the roof of the converter, each of said coils being composed of a plurality of spaced parallel tubes through which oil vapor to be heated fiows serially, a vapor manifold located exteriorly of said wall structure and operable to supply each of the independent tube coils with oil vapor whereby to cause the vapor to travel in serial flow through each of the tube coils and with multiple delivery of vapor simultaneously to each of the coils from said manifold, a second manifold disposed exteriorly of the wall structure of the converter into which oil streams heated in said tube coils and discharged therefrom are merged in a single stream, a bank of serially united parallel tubes arranged openly in said tube chamber below the first-named tube coils and extending at 'right angles thereto and through which oil vapor heated in the multiple tube coils is passed following discharge in a merged stream from said second manifold, and valve means arranged between said flrst-named manifold and each of said tube coils to vary the rate of delivery of oil vapor to each of said tube coils.

l 5. In a converter for cracking oil in the vapor phase, a heat-confining wall structure arranged to provide burner and tube chambers spaced by an intervening bridge wall over the top of which said chambers communicate, combustion developing means arranged adjacent to the lower part of the burner chamber, an outlet duct for furnace gases communicating with the lower part of the tube chamber, a plurality of independently regulable disposed tube coils supported at their ends by said wall structure and intermediately of their lengths by the bridge wall, said coils being arranged openly in said converter above the burner and tube chambers and below the roof of the converter, each of said coils being composed of a plurality of spaced parallel tubes through which oil vapor to be heated flows serially, a vapor manifold located exteriorly of said wall structure and operable to supply each of the independent tube coils with oil vapor whereby to cause the vapor to travel in serial flow through each of the tube coils and with multiple delivery ofvapor simultaneously to each of the coils from said manifold, a second manifold disposed exteriorly of the wall structure of the converter into which oil streams heated in said tube coils and discharged therefrom are merged in a single stream, a4 bank of seriallyunited parallel tubes arranged openly in said tube chamber below the first-named tube coils and extending at right angles thereto and through whichoil-vapor heated in the multiple tube coils is passed following discharge in a merged stream from said second Y manifold, and auxiliary combustion developing means arranged between the roof of said converter and the tube coils.

6. In a converter for cracking oil in the vapor phase, a heat-confining wall structure arranged to provide burner and tube chambers spaced by an intervening bridge wall over the top of which said chambers communicate, combustion developing means arranged adjacent to the lower part of the burner chamber, an outlet duct for furnace gases communicating with the lower part of the tube chamber, a plurality of independently regulable horizontally disposed tube coils supported at their ends by said wall structure and intermediately of their lengths by the bridge wall, said coils being arranged openly in said converter above the burner and tube chambers and below the roof of the converter, each of said coils being composed of a plurality of spaced parallel 'tubes through which oil vapor to b e heated flows serially, a vapor manifold located exteriorly of said wall structure and operable to supply each of the independent tube coils with oil vapor whereby to cause the vapor to travel in serial ow through each of the tube coils and with multiple delivery of vapor simultaneously to each of the coils from said manifold, a second manifold disposed exteriorly of the wall structure of the converter intowhich oil streams heated in said tube coils and discharged therefrom are merged ina single stream, a bank of serially united parallel V tubes arranged openly in said tube chamber below the first-named tube coils and extending at right angles thereto and through which oil vapor heated in the multiple tube coils is passed following discharge in a merged stream from said secondmanifold, and a bank of vaporizing tubes disposed in the outlet duct leading from the tube chamber for preheating oil .prior to the delivery of at least a fraction thereof to said first-named manifold.

'1. In a converter for cracking oil in the vapor phase, a heat-conning wall structure arranged to provide burner and tube chambers spaced by an intervening bridge wall over theitop of which said chambers communicate, combustion develop- 150 ing means arranged adjacent to the lower part of the burner chamber, an outlet duct for furnace gases communicating with the lower part of the tube chamber, a plurality of independently regulable horizontally disposed tube coils supported at their ends by said wall structure and intermediately of their lengths by thebridge wall, said coils being arranged openly -in said converter above the burner and tube chambers and below the roof of the converter, each of said coils being composed of a plurality of spaced parallel tubes through which oil vapor to be heated flows serially, a vapor manifold located exteriorly of said wall structure and operable to supply each of the independent tube coils with oil vapor whereby to cause the vapor to travel in serial flow through each of the tube coils and with multiple delivery of vapor simultaneously to each of the coils from said manifold, a second manifold disposed, ex-

teriorly of the .wall structure of the converter into which oil streams heated in said tube coils and discharged therefrom are merged in a single stream, and a bank of serially united parallel tubes arranged openly in said tube chamber be i los

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