US1869838A - Process and apparatus for heating oil - Google Patents

Description

lAug. 2, 1932.

J.' c. BLACK PROCESS AND APPARATUS FOR HEATING oIL INVENTUR. (Z55/aofi BY. l

A 'w14 NEW Filed 0G12. 20, 1926 Patentedl Aug. 2v, 1932 STATES PATENT ortica JOHN C. BLACK, OF DESTN, LOUISIANA, ASSIGN'OR T0 GASOLINE PRODUCTS COM- i n INC., F WILMINGTON, DEILAMTABE.a A CORPORATION 0F DELAWARE non HEATING o'rn Application led Qctober 20, 1926. Serial No. 142,998.

This invention is directed to a process and apparatus for cracking oil.

1n a process in which oils are cracked by yheating the oil lduring its passage throng coils, care must be taken to impart the necessary heat to the oil without superheating the oil at any point. rlhis superheating causes excessive decomposition with a consequent formation of carbon and fixed gases.

1t is therefore an object of mv invention tol crack oil in tubes and to regulate the heating of the oil to prevent excessive decomposition and carbonization. v

The invention will he better understoodby referring to the accompanying drawing which shows a furnace construction in which the above objects are realized., together with a conventional illustration of the units for the purpose of completing` a process of separajt1on of the light products formed during the crackin containing the cracking stock, that is, the oil" to be cracked. 2 is a pump connecting tank 1 to line 3.,.which line is controlled by a. valve 3', Line 3 connects with analyzer 4 situated in bubble tower 25. 5 is a line connectin analyzer 4 with line. 5 is a valvein sai line. 6 is a valve in line 6. 7 is a pump con-- necting line 6 with line 8. 8 is a valve in line 8. 9 is a line connectingline 8 with the upper coils 10 and 11 situated respectively in furnaces 41 and 42. 12 is a line connectingv the uppermost pass of coil 11 with the lower passes of coils 13 and 14, situated respectively in furnaces'42y and 41. 15 is a coil connected to coil 14 and situated above coil 14 and below coil 10 in furnace 41. 16 is a cross-over connecting coil 15 with coil 17 which is situat ed in furnace 42 betweeny coils 13 and 11. l18 is an exit line connecting` coil 17 with the carbon catcher l19. 18 is a valve in line 18. 20 is a. line connecting chamber 19 with exchanger 22. 20 is a valve in said line. 21 is a by-pass in which are valves 21 and 21 for lay-passing the carbon catcher and reactionof the oil. 1n this ligure, 1 is a tank chamber 19. 23 is a line connecting the heat exchanger 22 with evaporator 24. 23 is a valve in line 23. 25 is a rectifying and fractioning tower situated above evaporator 24.

26 is a vapor line connecting tower 25 with50 condenser 27. 28 is a lockbox situated in condenser run-down line 30. 31 is a tank for collecting the condensate issuing from line 30. 29 is a gas vent connected to lookbox 28. 32 is a trap for separating the condensate formed in tower 25. 33 is a line connecting said trap to tank 35.. 34 is a cooler in said line; 36 is aline connecting tank 35 with the intake of pump 7. 38 is a valve in said line. 37 isa line connected to the bottom of evaporator 24 and to the tank 40..` 38 is a pump in said line. 39 is a cooler in said line. J52 is a line connecting the exit side of pump 7 to heat exchanger 22. 52 is a valve in said line. 53 is a line connecting heat exchanger 22 with line 9. 48 is a line leading from the exit side of pump 7. 48 is a valvein said line. 49 is a line connecting line 48 to one of the nal passes in coil 17 shown specifically in the drawing as the last pass. 49q is a valve in said line. 50 is a line connecting line 48 with the final tube in coil 17. 50 is a valve in said line. 51 is a line connecting line 48 with line 18 at the exit of the coil 17. 51' is a valve in said line. 43 is a pyrometer situat- 'I5 ed'at the exit of coil 14. 44 is a pyrometer situated at the exit of 15. 54 is a pyrometer lsituated at the point of union of line 49 and coil 17. 45 is a pyrometer situated at the point of union of line 50 and coil 17. 47 is Q0 a pyrometer situated at the exit of coil 17. and just beyond the union of line 51 with line 18. 52 is a water tank. 53 is a line connecting the water tank with the intake line of pump 7. 53 is a valve in said line.

The operation of this system is as follows:

A suitable cracking stock, which may be a gas oil, contained in tank 1 ispicked up by pump 7 and introduced by the proper regulation of valves through line 52 and heat ex" changer 22, line 53 and line 9 to the coil 10. It passes through a bank in coil 10'situated in furnace 14 across into a bank situated in furnace 42, upward to an upper4 bank in furnace 42, across to an upper bank in furnace 41, upward to an upper bank in furnace 41, across into an upper bank in furnace 42.- As will be observed, this progress is concurrent to the passage of the combustion gases 1n above furnaces. After exiting from coil 11 the oil passes downward to the lowermost pass in furnace 42, across to the lowermost pass in furnace 41, upward to an upper bank in furnace 41; across to an upper bank in furnace 42; upward to an upper bank in furnace 42; across to an upper bank in furnace 41. It then continues in concurrent passage to the combustion gases through coil 15 in'furnace 41, and then passes through cross over` line 16 into coil 17 which is situated above the passes of coil 13 and passes in through `coil 17 in furnace 42 concurrent with the combustion gases in furnace 42.

While the illustration and description shows three passes in coil 10 and 11; three passes in coils 13, 14, and five passes each in the furnace coils 15 and 17, it will be clearly understood by the man skilled in the art that this illustrates but the direction of passage and character of construction of the furnaces. The number of passes which will be employed will be dependent upon the temperature to which the oil is to be heated; to the character of the oil; vto the volume of oil and the temperature of the furnace gases and their amount, and to the time during which the oil is to be heated to obtain the desired reaction. All these are questions of design familiarI to all engineers skilled in this art. Also,`while the illustration given shows the oil passing through a single pass through coil 10 then to a single pass in coil 11 to a pass immediately above, and then from that pass to a fourth.

pass in coil 10 immediately above the first pass, it will be clearly understood that this construction may be yvaried so that the oil in coil 10 may pass through a number of passes upwardly in coil 10, thenI across to a number of passesxin coil 11 upwardly through these passes and across to a number of passes in coil 10, and upwardlythrough these passes and in the same manner it `may continue its progress first through a number of passes in one coil and then through a numberof passes in the analogous (coil situated in the otherfurnace, as will be clear to those skilled in the art. Y

The oil passing through coils 10 and 1l are used as economizer coils to extract as much heat as possible from the waste gases issuing upward through the furnace. The oil issuing from coil 11 then passes through coils 13 and 14. This oil is still relatively cool and acts to temper or cooldown the hot combustion gases formed in these furnaces. The oil in passing through coils 13 and 14 is heated up to the chosen cracking temperature of -the oil, as measured by pyrometer 43. The oil when passing upwardly through coil 15 is heated to supply to the oil the endothermic heat of the cracking reaction. The oil in passing through coil 15 is maintained at substantially constant temperature, or at an increased temperature, care being taken, however, that the temperature is not allowed to drop below the chosen cracking temperature., The oil at the eXit from coil 15 crosses over into coils 17, through pipe 16, where additional heat is supplied to the oil to continue the cracking of the oil and to maintain the chosen cracking temperature, or to cause an increase thereof, care being taken in this heating that the temperature does not drop below the desired cracking temperature. Instead of dividing the coil into two sets of coils 15 and 17 continuing upwardly through furnace 41 in coil 15 then upwardly through furnace 42 in coil/ 17 coils 15 and 17 may be cross-connected in the manner of coils 10 and 11, or 13 and 14.

It will be understood that 'as the oil progresses upwardly through 15, and upwardly through 17 the oil is more and more cracked, and a concentration of the lighter hydrocar-v bons that do not crack readily, or did not crack at all at the temperature maintained in the coils, occurs in the oil. The temperature, as stated before, is maintained substantially constant through the passes in the coils 15 and 17 consequently there will be a smaller absorption of heat by the cracked oil. Unless care is taken to limit the intensity of heating, the tubes through which the highly cracked oil passes will become overheated and the oil in immediate contact with these overheated tubes would become excessively cracked, de-

rently with the direction of the heating gases,

this overheat is limited, for as 'the oil becomes more and more cracked and its capacity of yabsorbing endothermic heat diminished, the oil passes from a region of hot combustion gases to a region of cooler combustion gases, the thermal differential between the oil and the combustion gases becomes less and the tendency for overheating the coils is diminished and practically avoided.

By placing the preheating coils below the reaction coils 15 and 17 the combustion gases are tempered, and the. coils 15 and 17 are shielded from the direct action of the flame. The oil entering coils 13 and 14 being relatively cool can absorb considerable ,heat from these high temperature gases. The heat vtransferred is sufficiently good so that no overheating of the coils 13 and 1 4 results. The combustion gases reachlng colls 15 and superheating of the tubes.

i the heating 'inject the oil into ber. l may, however,

17 are therefore tempered down so that they are at such temperature as will avoid the That is, the heat transferred from these` partially cool gases will not be greater than that which the oil can absorb in endothermic reaction.

By dividing the (coils into twofurnaces of the coils'is more easily controlled, and the heating of the oil during its passageis more uniform.

The oil in reaching the final passes of coil 17 has been highly cracked, and its capacity to absorb heat as endothermic heat is therefore diminished to a very small point. These final passes therefore have a tendency to overheat, even though they are in an upper region of the furnace. In order to avoid the superheating of the coils, I have found it advantageous at times to inject into one of the iinal passes relatively cold,uncracked oil. This injected oil cools down the main stream of oil passing through the final passes, and the mixed stream therefore absorbs heat both as sensible heat and as endotherrnic heat from the combustion gases. This injected oil is, therefore, cracked both by the sensible heat of the main stream, and by the absorption of heat from the combustion gases. rlhe mixed stream then passes through the rest ofcoil 17 where it is heated to the desired temperature. The addition of this injected oil has the additional advantage of diluting the oil and reducing the vapor` pressure of the oil. A

l have found it advisableat times instead of injecting the oil into the final passes, to

the final tube. l may inject it at the exit of the coil. The injected oil is cracked by the admixture an *also cools down the cracked oil. The oil issuing from the coil 17 passes to the'carbon catcher and reaction chamber 19. The oil passing through the reaction chamber may have its cracking completed because of the' prolonged' period of time during which it is in the cham- Operate Without this chamber by giving the oil suiiicient time in the coils 15 and 17 that is, by increasing the length ofthe coil or varying its rate of passage. 1f l do this, the oil may pass through by-pass L21, valves 18 and 20 being closed. The oilgthen issues through line 20 and passes through heat exchanger 22. ln this heat exchanger the oil is partially cooled down giving 0H heat to the incoming oil to be cracked. 1n order to prevent the oil passing through line 29 through heat exchanger 22 from becoming cooled down too much, the amount of oil passing from pump 7 to heat exchanger 22 is regulated by regulating the valves 52 and 8. lf too much oil is passing d through hea't exchanger 22, oil is by-passed through line 8 into line 9 directly. The oil on passing through line 28 past the pressure reducing valve 23 is expanded into evaporator 24. In this evaporat the lighter fractions of the oil are evaporated,l the vapors are reiuxed in bubble tower`25, the uncracked oil is condensed,trapped out in chamber 32 and taken away by line 33, and cooled in cooler 34; It is then sent into tank 35 from which tank it is picked up by pump 7 tobe recycled through the process. Vapors rising in bubble tower 25 are refluxed therein by the aid of analyzer 4, which is cooled by oil coming from tanlg'l and circulated by pump 2 through pipes 3 and 5. The amount of the oil circulated is regulated by the pump 2 and valves 3 and 5 in order to controlthe correct fractionation in tower 25. Vapors rising from tower 25 which consist of the crude gasoline distillate formed in the cracking' process, are condensed in condenser 27 and collected in tank 31. Uncondensed gas is vented through line 29.

I prefer to operate ing to process disclosed in my Patent 1,456; 419, that is, to maintain a superimposed pressure on the oil greater than the vapor pressure developed during the heating.

As a specic example of my operation the following -may be given as an illustration. ln operating with a gas oil, the pressure as indicated on pressure gauge 46 should be in the neighborhood of 1000;t;':. rlhis pressure v is released toabout atmospheric in the evaporator. Gas oil is heatedin coils 10 and 11, 13 and' 14 until its temperature shall be, as indicated on pyrometer 43, about `840" F. This temperature is maintained through coil 15 and 17. In using injection oil via line 49, the oil injected is controlled so that the temperature is dropped to about 800. The oil then is heated up during its passage through the rest of the coil without further temperature control. The oil'on issuing from the coil passes through the heat exchanger where it is cooled down to about 700- F., and then passes to the evaporator. The gasoline fraction removed constitutes in the neighborhood of25% of the charge. The reaction coils 15 and 16 are so designed that the oil is given about 20 minutes of' heating at the cracking temperature.

naces, plpe connections for passing .oil first 1 25 through a portion of the upper coils srtu4 ated in the path of relatively cool combustion gases in one of said furnaces, then through a portion of the upper coils situated in another furnace in timev path of cool com- 430 this invention accordv A blow-down connection iscl shown whereby Water may be forced through M5 my invention, izo

for heating oil to a crachy of pipe coils in said furnaces, and then passing said oil through a coil situated between sald first mentioned coil and said second mentioned coil, in the path of combustion gases at an intermediate temperature in the first mentioned furnace, and then, in like manner, passing the oil through a coil situated in the path of combustion gases at an intermediate temperature in the second mentioned furnace. v

'2. An apparatus for heating oil to a crackin temperature, which comprises a plura ity of furnaces, a plurality of sets of pipe -coils" in said furnaces, pipe connections4 for a passing oil through a horizontal portion of an upper setof pipe coils, conveying oil across the path of combustion gases in one furnace, then passing said oil through a portion of another upper set of pipe coils, situated in another furnace, conveying oil horizontally across the path of combustion gases, then, passing said oil through other horizontal portions of said upper sets of coils concurrent to the flow ,of combustion gases; a pipe connection for conveying said oil to the lowest sets of pipe coils, and passing said oil through a horizontal portion of the lowest set of pipe coils across the path of combustion gases in one furnace, then passing said oil through a portion of another set of pipe coils situated in another furnace conveying oil horizontally across the pathl of combustion gases, then passing said oil through other horizontal portions of said lowest sets of coils concurrently to the flow of combustion gases; pipe connections for passin oil through a horizontal intermediate set o pipe coils, conveying oil across the ath of combustion gases, and continuing t e flow of oil through other sets of pipe coils in the same furnace, conveying oil copcurrently to the flow of combustion gases; a pipe,` connection for conveying the oil to a lower portion of a similar set of pipe coils situated lin another furnace, which in like manner conveys the oil concurrently to the fiow of combustion gases to a suitable outlet; and. connectionsA forintroducing a cooloil into the last coil or last row of coils of this set of coils to lower the temperature to a point below the crackingy temperature.

` 3. An apparatus for heating oil to a cracking temperature, which comprises a plu'- rality of furnaces, a plurality of sets of coils in said furnaces, disposed on different levels, pipe connections to deliver oil from'the uppermost coils in`a first furnace to the uppermost coils in a second furnace, pipe connectionsl for delivering oil from the uppermost coils of the second furnace to the lowermost coils therein, pipe connections for delivering oil from the said lowermost coils to the lowermost coils Ain the first furnace, pipe connections for delivering oil from the lowermost coils of the said first furnace to the intermediately disposed coils in said furnace, and pipe connections from the top of said intermediate coils to the bottom of the intermediate coils in said second furnace. 4. A continuous process for cracking hydrocarbon oils, comprising, passing oil to and through a continuousheatingcoil in concurrent heat exchange relationship with relatively cool furnace gases in a furnace, whereby saidoil is-heated to a point below the cracking temperature, then passing the oil in heat exchange relationship concurrently with highly heated furnace gases, where said oil is heated to a cracking temperature without any substantial overheating of any part of the oil and then passing the oil in concurrent flow with furnace gases intermediate in temperature between the first and second furnace gases, wherein said oil is maintained at a substantially uniform cracking temperature and finally injecting quantities of cooler cracking stock into the oil stream as it leaves the cracking coil,'in quantities sufficient to cool the said streamibelow the temperature of excessive decomposition and carbonization ofthe main stream of oil.

5. A continuous process for cracking hydrocarbon oils, comprising, passing oil to and through a continuous heating coil in concurrent heat exchange relationship with relatively cool furnace gases in a furnace, whereby said oil is heated to a point below the cracking temperature, then Icontinuing passing the oil in a heat exchange Vrelationship concurrently with highly heated furnace gases, Where said oil is heated to the cracking temperature and then passing the oil in concurrent flow with furnace gases intermediate in temperature between the first and second mentioned furnace gases, at a temperature `sufiicient to maintain the oil at a substantially uniform cracking temperature, in-

jecting a cool hydrocarbon oil of the samt` character, into the oil stream as it leaves the cracking coil; whereby ythe temperature of the admixed stream is lowered below the temperature of excessive decomposition and carbonization of the main stream of oil, said temperature of the admixed stream .of oil being sufiicient. to partially crack the injected oil.

6. An apparatus for heating oils to a cracking temperature, comprising a plurality of furnaces having passageways for the comnseaeas hustion gases and exit hues, multiple sets of horizontal heating coils arranged in succession in said passageways and pipe connections connecting the sets of coils, whereby the oil to be heated is` conducted to and through the set of coils closest to the exit ues in concurrent iiow with combustion gases, thence to and through the set ofcoils closest to the combustion chamber of the furnaces in concurrent flow with combustion gases and finally to and through the intermediate 'set of coils disposed between the aforementioned sets of coils in concurrent flow with the com bustion gases.

7. An apparatus for heating oil to a cracking temperature which comprises a plurality of furnaces having vertical passagewa s for the combustion gases, sets of pipe coi disposed in dierent levels above each other in said passageways, and means comprising ipes connectingjthe sets of pipe coils, wherey oil to be heated is conducted to the uppermost set of coils in series relationship with each other, thence to the lowermost set of coils in series relationship to each other and then through an intermediately disposed coil in one furnace then to a second intermediately disposed coil in the second furnace, said pipe connections to said coils providing' means whereby the oil to be heated is conducted through said coils concurrently with' the iiow of combustion gases.

8. A continuous process for cracking hydrocarbon oils comprising, passing oil to and through a continuous coil in concurrent heat exchange relationship with relatively cool furnace gases in a furnace, whereby said oil is'heated to a point below the cacking temperature, then passing the voil in heat exchange relationship concurrently with highly heated furnace gases, whereby said oil is of oil.

JGHN C. BLACK.

heated to a cracking temperature Without l any substantial overheating of any part of the oil and then passlng the oil in concurrent flow with furnace gases intermediate in teinj perature between the rst and second furnace gases, whereby said oil is maintained at a substantially uniform cracking temperature and finally injecting quantities of cooler cracking stock into the oil stream as it passes through the final passes of the cracking coil, in quantities sufficient to cool the said stream below the temperature of excessive decomppsitlion and carbonization of the main stream o o1 i 9. A continuous process for cracking hydrocarbon oil comprising, passing oil to and through a continuous coil in concurrent heat relationshi with relatively cool furnace gases in a urnace, whereby said oil is heated to a point below the cracking temperature, then passing the oil in heat exchange relationship concurrently with highly heated furnace gases, whereby said oil is heated to a cracking temperature without lany substan-

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