US1838211A - Process of and apparatus for heating oil for cracking distillation - Google Patents

Description

Dec. 29, 1931. c. B. BUERGER 1 PROCESS OF AND APPARATUS FOR HEATING OIL FOR CRACKING DISTILLATION Filed June 28. 192'? 2 Sheets-Sheet 1 6 much 2 @AMVAMOAMO nnOQHuONUnmU COHuHUaunmu M h w Fwm H H A/ i 8. w Eon 3 Hm nmOHUnmuONu L Q /v comoonuouoomo ouoouuonofio omonmuomo WQAMUQMOQMO cnmunmvo owv 7 V 8.25 Q 5 W 3 0 Dec. 29, 1931. BUERGER 1,838,211

PROCESS OF AND APPARATUS FOR HEATING OIL FOR CRACKING DISTILLATION Filed June 28, 1927 2 Sheets-Sheet 2 I N "I fi N Baezye Patented Dec. 29, 1931 UNITED STATES PATENT OFFICE CHARLES B. B'UERGER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 GULF RE- FINING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF TEXAS I PROCESS OF AND APPARATUS FOR HEATING OIL FOR CRACKING DISTILLATION Application filed June 28,

This invention relates to process of and apparatus for heating oil for cracking distillation, and it comprises delivering the oil, preferably under heavy pressure, through tubes located in a relatively cool portion of a tube bank chamber of a furnace (the hot gases around the heating tubes being advantageously of a temperature in the neighborhood of 900 F. to 1200 F.), then through tubes located in respect to the furnace in such position that they will be subjected to the radiant heat thereof (and wherein the oil temperature will be raised by about 100 to 150 then through two subsequent tube banks,

the second of which is subjected to gases direct from the furnace (at a temperature in the neighborhood of 1500 F. to 1700 F.), and the first of which is subjected to gases which have given up part of their heat to the last mentloned tube bank and which have been reheated by the regulated addition of further gases direct from the furnace (the temperature of these combined streams of gas being in the neighborhood of 1400 F. to

1100 F.); whereby a large portion of the oil in the heating tubes is maintained within a desired elevated temperature range while protected from extreme temperatures, and whereby there results a uniform rate of heat so transmission to the oil; and it further comprises means for the generation of the necessary heat, a'pipe coil or series of pipe coils through which the petroleum oil is continuously passed; and means for distributing the heat to different portions of the coil in such manner as to maintain a large portionof the heating coil at a relatively uniform temperature and to supplyvheat to the oil passing therethrough at a substantially uniform rate, while delivering the combustion gases to the stack at a relatively low temperature not substantially above that at which the oil is discharged from the final coil, all as more fully hereinafter set forth and as claimed.

In the cracking distillation of petroleum it is desirable to bring the oil to, and then to maintain it within, a certain elevated \temperature range While supplying additional heat, and which protecting the petroleum undergoing treatl nent from excessive tempera- 1927. Serial- No. 202,048.

such high temperature gases without subjecting the oil undergoing treatment to excessive temperatures, accompanied by the production of large quantities of fixed gas and a reduction in the yield of desired liquid products.

Among the objects of the present invention are; to lower the temperature of the furnace gases to a safe temperature by passing relatively cool oil through one bank of tubes in the furnace proper, so positioned that they will absorb the radiant heat while not being interposed in the direct path of the hot combustion gases; to then divide these gases into two or more parts, so using these different portions (either singly or in combination) as to maintain a relatively even and effective though safe temperature over a considerable portion of the tube banks; and to do this in such manner as to maintain a relatively even rate of heat transmission to the material undergoing treatment.

In the accompanying drawings, Figs. 1 and 2, I have shown two forms of apparatus useful in the performance of my process and within the purview of my invention. Fig. 1 is a transverse section with parts in elevation through a furnace and tube bank chamber. Fig. 2 is a similar section and the apparatus illustrated therein differs from that in Fig. 1 only in that there is an additional tube bank in the tube bank chamber, and an additional flue and damper, as subsequently described.

In Fig. 1 reference numeral L. is the furnace proper or heat generating chamber; 2 is the tube bank chamber or heat absorbing arating the furnace from the tube bank chamber, broken by thepassages 5 and 6, which permit the directed passage of the hot furnace gases to the tube bank chamber. In passa es 5 and 6 are positioned dampers.7 and 8 or regulating the flow of gases through these openings. The stack is indicated as 9, while 10 is a firing opening in the front of the furnace, through which opening the oil, gas or other suitable burner 11 is introduced. The oil to be treated is drawn from a source of supply through suction line 12 to the pump '13,-

which discharges it under high pressure through the line 14 to the upper bank of tubes 15. The incoming oil in passing through the tube-bank 15, absorbs heat from the furnace gases immediately before they leave the tube bank chamber and the oil then passes through the connecting line 19 to the tubes 16 positioned in the top of the furnace chamber 1,

where it absorbs radiant heat from the furnace. Leaving the tubes 16 through the connection 20 the oil enters tube bank 17 and then passes through connection 21 to tube bank 18, after which it leaves the apparatus through line 22 and may be delivered to a separating chamber or drum, from which vapors and oil may be separately collected in any known manner. Positioned on thelines 1d and 22 are the valves 23 and 24 respectively.

In a still for the cracking distillation of petroleum, it is essential that there not be any concentration of heat upon any one part of the oil in its travel through the system, and that the heating of the oil once it approaches the temperature range wherein the desired cracking takes place. be at a relatively uniform rate. These desiderata have been attained to a high degree in the present invention by the provision of a furnace in which the furnace gases as generated in the furnace will surrender a substantial propor tion of their heat by radiation to the relatively cool oil being circulated through the tubes positioned in the top of the furnace (this lowering the temperature of the gases by from 300 F. to 600 F.) in which the stream of gases is then divided and passed to the tube heating chamber 2 through the damper controlled passages 5 and 6; in which that portion of the gases which enters the tube chamber through the passage 6 will give up a portion of its heat to the oil passing through the tube bank 18 just before the oil leaves the apparatus; in which the partially cooled gases are then joined by the hot gases entering through passage 5; and in which the sensible heat of these gases which enter through passage 5 is shared with the gases which have already given up a part of their heat in tube bank 18, thus producing a greater body of gas at a temperature sufficiently high to give good heat transmission to the oil passing through the tube bank 17, while not at a temperature sufficiently high to cause any deterioration of the material undergoing treatment.

It will now be seen that the incoming, relatively cool oil is first subjected in the tube bank '15 to the heat of the gases immediately before the escape to the stack, removing the last availa le heat therefrom that the oil not yet up to what might be called the critical range, in which its heating must be very delicately controlled, is next exposed to the radiant heat of the furnace, which is so proportioned as to permit the reatest heat absorption consistent with sa ety; that the oil then oesto tube bank 17 where it absorbs rom the gases (which have already given u most 0 their available heat to tube bank 18 after these gases have been reheated by mixture with the furnace gases entering through passage 5; and that the oil then receives its final heating in the tube bank 18 where it-is exposed only to the gases entering the tube chamber through the passage 6.

In operating in accordance with the particular embodiment of my invention illustrated by Fig. l the furnace gases entering passages 5 and 6 were at a temperature of 1550 F the gases entering the tube chamber through passage 6 were reduced to 1125 F. after passing through the tube bank 18; these same gases, together with the gases entering the tube chamber through passage 5, combined, had a temperature of 1300 F., at the bottom of bank 15 the temperature was 1125 F.; and the gases finally entered the stack at 900 F. Operating this apparatus in such manner, and maintaining a temperature of 900 F. in the oil leaving through pipe 22, it will be seen that there is always a temperature differential between the heating medium and the material being heated sufficient to give even, effective heating without exposing the heated oil at any time to temperatures which would prove destructive.

With the furnace gas temperatures as above given, in the embodiment described, the temperature of oil upon entering the coils through pipe 14 (already preheated) was 700 to 730 F the oil leaving the bank 15 and entering the tube 16 was about 760 F. and the oil leaving the tube bank 16 and entering the tube bank 17 was 875 F. By the time this oil had passed through the banks 17 and 18 it had reached a temperature of about 900 and was delivered from bank 18 at that temperature through line 22to the point of separation of oil and vapors.

This invention as described, permits maintaining a. large portion of the heating tubes within a desired elevated range, protecting them from extreme temperatures, this protection being evidenced by the fact that per cent of the heating surface is ordinarily exposed to temperatures not more than 400 F. nor less than 200 F. above that of the oil undergoing treatment. This invention also gives a very uniform rateof heat transmission to the oil, once it has been brought to what has previously been referred to as its critical range. This is true because where the hotter gases are applied to the tubes, as in bank 18, the quantity of these gases and their velocity is less than is the case in the upper banks and this lower velocity results in a lower heat transmission to the material in the tubes in this section.

Fig. 2 illustrates another advantageous en}- bodiment of my invention and this figure is identical with Fig. 1 except that an additional tube bank 17 has been inserted between banks 17 and 18, and an additional flue 5', controlled by damper 7 has been inserted in the bridge wall. tween bank 17 and the heat generating chamber 1 is indicated by 41', and a line which conveys hot oil from the discharge end of bank 17 to the entrance end of bank 18 is shown as 21'. Fig. 2 illustrates an embodiment of my invention wherein hot furnace gases from the chamber 1 can be conveyed into the tube bank chamber 2 at more than one point interjacent the two extremities of the tube banks in the tube bank chamber.

While the specific oil and gas temperatures of the modification described are indicated on Fi 1, this is for the purpose of illustration on%y, and the invention is, of course, not to be regarded as limited to the modification described. So also as to the position which the radiantly heated section of the tube C011 may bear to the other sections of the tube coil, as

for instance the oil may pass through all of the tube coil above the upper furnace gas passage before it passes through the radiantly heated section.

What I claim is:

1. Apparatus for heating tubes which comprises a furnace chamber, means for firing the same, a tube bank chamber and a plurality of vertically spaced passages leading from the furnace chamber to the tube bank chamber, a tube arranged in the tube bank chamber with a plurality of the coils below the highest of said passages and above the lowest of said passages, and a plurality of other coils above the highest passage, whereby the lower said coils are heated by hot gases direct from said furnace chamber, whereby the higher coils are heated with the gases which have passed the lower coils sup-' plemented by hot gases direct from said furnace chamber, and whereby the flow of hot gases through the several vertically spaced assages is so proportioned as to effect an initial heating of the material.

2. Apparatus for heating tubes which comprises a furnace chamber, means for firing the same, a tube bank chamber and a plurality of vertically spaced passages leading from the furnace chamber to the tube bank chamber, a tube arranged in the tube bank That portion of the bridge wall be-' chamber with a plurality of the coils below the highest of said passages and above the lowest of said passages, and a plurality of other coils above the highest passage, dampers in said passages whereby the lower said coils are heated by controlled gases direct from said furnace chamber, and whereby the higher coils are heated with the gases which have passed the lower coils supplemented by hot controlled gases direct from I said furnace chamber.

3. Apparatus for heating tubes which comprises a furnace chamber, means for firing the same, a tube bank chamber and al plurality of vertically spaced passages lead-, ing from the furnace chamber to the tube bank chamber, a tube arranged in the tub bank chamber with a plurality of coils below the highest of said passages and above the lowest of said passages, and a pluralityl of other coils above the highest passage, and a branch coil leading from the coils of the tube bank into the furnace chamber to a position exposed to the radiant heat there-i of and returning to the coils in the tube bankl chamber, whereby the lower said coils are heated by hot gases direct from the said furnace chamber, and whereby the higher coils are heated with the gases which have, passed the lower coils, supplemented by hot gases direct from said furnace chamber, and whereby a part'of the coils is subjected to radiant heat of the furnace.

4. Apparatus for heating tubes which comprises a furnace chamber, means for firing the same, a tube bank chamber and a plurality of vertically spaced passages lead-, ing from the furnace chamber to the tube! bank chamber, a tube arranged in the tube bank chamber with a plurality of coils below the highest of said passages and above the lowest of said passages, and a plurality of branch coil leading from the higher coils 'of the tube bank into the furnace chamber to! a position exposed to the radiant heat thereof and returning to the higher coils in the tube bank chamber whereby the lower said coils are heated by hot gases direct from the{ said furnace chamber, and whereby the} higher coils are heated with the gases whichf have passed the lower coils supplemented by hot gases direct from said furnace chamber, and whereby a part of the higher coils is subjected to radiant heat of the furnace.

5. In a tube heating furnace having a furnace chamber and a tube bank chamber, banks of tubes in the tube bank chamber, vertically spaced passages for directing portions of the furnace gases from the furnace chamber to selected zones of the tube bank chamber and a branch coil leading from the tube in the tube bank chamber and extending in the furnace chamber to a point where it receives the radiant heat of the furnace, and returning to the tube in the bank chamber.

6. In a furnace for heating tubes, a furnace chamber and a tube bank chamber, a continuous coil in the tube bank chamber extending from a high point thereof to a low point thereof with an intermediate section of the coil extending into the furnace chamber at a relatively high point where it is subjected to radiant heat, and a passage from the furnace chamber to the tube bank chamber at a point lower than that occupied by any portion of the coil, whereby the coils in the tube bank chamber receive fire gases direct from the furnace chamber and the contents of the coils which have been subjected to radiant heat may be heated by the said direct fire gases.

7. A process of heating oil in a petroleum cracking process which comprises forcing the oil undergoingtreatment through a tube coil exposed to hot gases generated in a furnace; forcing the oil entering the tube coil at about 725 F. first through a relatively cool portion of the tube coil in which the temperature of the oil is'raised not substantially more than 50 F., then through a second portion of the tube coil which portion is exposed to the radiant heat of the furnace and in which the temperature of the oil is raised substantially 100 F. to 125 F., then through a final portion of the tube coil exposed to moderate heating in which the temperature of the oil will be increased by not-more than 50 F.; while reheating the gases intermediate of their passage over the final ,portion of the tube bank by the addition of further gases direct from the furnace.

8. A process of heating oil in a petroleum cracking process which comprises forcing the oil undergoing treatment through a tube coil exposed to hot gases generated in a furnace; forcing the oil entering the tube coil at about 725 F. first through a relatively cool portion of the tube coil in which the temperature of the oil is raised not substantially more than 50 F., then through a second portion of the tube coil which portion is exposed to the radiant heat of the furnace and in which the temperature of the oil is raised approximately 100 F. to 125 F., then through a final lportion of the tube coil exposed to moderate eating in which the temperature of the oil will be increased by not more than 50 F. and then discharged from the tube coil at a temperature not above 930 F. and reheating the gases intermediate of their passage over the final portion of the tube bank by the addition of further gases direct from the furnace.

9. A process of heating oil in a petroleum cracking process from a temperature of approximately 7 00 F. to a temperature not above 930 F. which comprises forcing the oil undergoing treatment through a tube coil exposed to hot gases generated in a furnace;

forcing the oil first through a relatively cool portion of the tube coil in which the temperature of the oil is raised not substantially more than 50 F., then through a second portion of the tube coil which portion is exposed to the radiant heat of the furnace and in which the temperature of the oil is raised approximately 100 F. to 125 F., then through subsequent portions of the tube coil exposed to moderate heating in which the temperature of the oil will be increased by not more than 50 F.; while reheating the gases intermediate of their passage over the subsequent portions of the tube coil by the, addition of further gases direct from the furnace.

10. A process of heating oil in a petroleum cracking process which comprises forcing the oil undergoing treatment through a tube coil exposed to hot gases generated in a furnace; forcing the oil entering the tube coil at about 725 F. first through a relatively cool portion of the tube coil in which the temperature of the oil is raised not substantially more than 50 F., then through a second portion of the tube coil which portion is exposed to the radiant heat of the furnace and in which the temperature of the oil is raised approximately 100 F. to 125 F., then through a final portion of the tube coil exposed to moderate heating in which the temperature of the oil will be increased by not more than 50 F. while reheating the gases intermediate of their passage over the final portion of the tube bank by the addition of further gases direct from the furnace; and in which per cent of the surface of the heating coil shall be exposed to gases not substantially less than 200 F. or substantially more than 400 F. higher than the temperature of the oil passing therethrough.

11. Heating apparatus for use in the cracking distillation of petroleum, comprising a furnace, means for firing the same, a tube bank so positioned in the furnace as to receive the radiant heat thereof, an enclosed tube bank chamber containing a plurality of subsequent tube banks shielded from the radiant heat of the furnace and through which the oil to be treated may be seriately forced, a stack connection at one extremity of the tube bank chamber, a plurality of ports affording communication from} the furnace to the tube bank chamber, one of said plurality of ports being positioned to convey and direct hot furnace gases from the furnace to the tubes in the tube bank chamber at their most remote point from the stack connection, and the remainder of said plurality of ports being positioned to convey and direct hot furnace gases from the furnace to the tubes in the tube bank chamber interj acent the two extremities of the tube banks in the tube bank chamber, and an adjustable damper positioned in each port, and adapted to control the passage of furnace gases therethrough lot independent of other ports or controlling dampers.

12. Heating apparatus for use in the cracking distillation of petroleum, comprising a furnace, means for firing the same, a tube bank so positioned in the furnace as to receive the radiant heat thereof, an enclosed tube bank chamber containing a plurality of subsequent tube banks shielded from the radiant heat of the furnace and through which the oil to be treated may be seriately forced, a stack connection at one extremity of the tube bank chamber, a plurality of ports affording communication from the furnace to the tube bank chamber, one of said plurality of ports being positioned to convey and direct hot furnace gases from the furnace to the tubes in the tube bank chamber at their most remote point from the stack connection, and the remainder of said plurality of ports being positioned to convey and direct hot furnace gases from the furnace to the tubes in the tube bank chamber at points interjacent the two extremities of the tube banks in the tube bank chamber, and an adjustable damper positioned in each port and adapted to control the passage of furnace gases therethrough independent of other ports or controlling dampers.

13. In a petroleum cracking process a method of heating the oil to be cracked which comprises continuously heating a flowing stream of oil in a tube bank so positioned with respect to a furnace that it will receive the.

radiant heat of that furnace, then subjecting the stream of oil to continued heating in a plurality of subsequent tube banks located away from the furnace and shielded from the radiant heat thereof, directing a controllable portion of the hot furnace gases to one portion of said subsequent tube banks to effect heating of the oil passing therethrough, and directing another independently controllable portion of said gases to another portion of said subsequent tube banks to there combine with and reheat the first mentioned controllable portion of hot flue gases. In testimony whereof, I have hereunto affixed my signature.

CHARLES B. BUERGER.

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