US1882579A - Oil heating still - Google Patents

Description

A. E. HARNSBERGER OIL HEATING STILL Filed Dec. 27, 1929 Il lll N Hadley Eflrnseger Patented Oct. 11, 1932 UNITED STATES VParri-:NT OFFICE AUDLEY E. I'IARNSBERGER, OF CHICAGO, ILLINOIS, ASSIGNOR TO` GYRO PROCESS COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF :MICHIGAN` OIL HEATING STILL Application led December 27, 1929. Serial No. 416,793.

This invention relates to improvements in tube stills of the type employed in the heat treating of hydrocarbon oils for purposes of distillation, cracking, polymerizing or other wise treating oil passing therethrough to control its physical or chemical properties.

rllhe invention has specific reference to an improved form of tube still particularly adapted for high temperature oil cracking and wherein provision is made for continuously passing vaporized flow streams of oil through a plurality of substantially horizontally arranged parallel tubes located in the high temperature zone ofthe still and for regulating the flow of the vaporizedl oil selectively through each of said tubes or groups thereof for the purpose of securing substantially uniform cracking temperatures of the vaporized oils discharged from said tubes.

In previous types of converters considerable diiiiculty has been encountered in the matter of maintaining uniform cracking temperatures in the parallel streams of oil vapor passing through the high temperature zone of a tubular converter. In certain of the tubes the oil vapor is heated to an undesirably high temperature, whereas in other tubes sub-normal temperatures are present and these variations in temperature interfere seriously with the successful operation of high temperature converters especially.v EXces sive temperatures in the cracking of oil in the vapor phase result in increased gas production and a corresponding loss in the recovery of a desired low boiling distillate. Subnormal cracking temperatures in such systems result in diminished distillate recovery and in greater recirculation of the oil stock undergoing heat treatment.

It is therefore the purpose of the present invention to provide an improved type of Aoil heater wherein the cracking tubes in the high temperature zone of the heater lare provided with valves or other regulating equivalent by which the quantity of oil vapor owing through each tube or each group of tubes may be properly regulated by simple operations to the end of securing approximately uniform temperatures of the oil vapor flowing through all of said tubes.

Itis another object of the invention to provide an oil heater of simple and improved design and wherein provision is made for utilizing efficiently the heat developed by the burner so that outlet or stack temperatures will be maintained at a minimum or desirable low temperature and wherein the heater or converter is of simple mechanical designl so that its building and maintenance costs will be comparatively low as regards previously used types of converters.

For a further understanding of the invention reference is to be had to the following description and the accompanying drawing wherein:

Figure lis a vertical longitudinal sectional view taken through an oil converter kconstructed in accordance withv the present invention, and

Figure 2 is a horizontal sectional View on the line 2,-2 of Figure 1.

Referring more particularly to the drawing, the numeral l designates the setting of my improved converter. The setting is formed from the usual refractory wall material and is provided internally with a transversely arranged vertically extending bridge wall 2, which divides the interior of the converter into combustion and tube chambers 3 and 4 respectively. The combustion vchamber is. provided with one or more main burners 5 by which the internal temperature of the setting is maintained, the burners 5 utilizing oil or gas as fuels, or other equivalent heating means may be employed. The chambers 3 and 4 communicate over the topv of the bridge wall 2 so that the heated gases of combustion pass generally upwardly through the chamber 3, horizontally over the top of the bridge wall 2 and then vertically downwardly through the tube chamber 4. The front wall of the setting l is laterally off-set as at G to produce the so-called Dutch oven effect, while the horizontal top or vroof 7 of the sett-ing is formed with a downwardly and arcuately curved rear portion 8 which joins with the upper portion of the vertical rear wall 9 of the setting and reflects heat downwardly into the tube chamber 4. The

i 60. openings formed in the front wall of the setbridge wall 2 may be provided with a center air circulating space 10.

Suitably supported in conjunction with the walls of the tube chamber 4 is a horizontally arranged row of serially connected drying tubes 11 which are arranged in the relatively coolest portion of the chamber 4. Oil to be cracked enters the tubes 11 in substantially vaporous form by way of the inlet pipe 12 and while passing through the tubes 11 this vaporized oil is subjected to a sufficient degree of heat to reduce the vapors to a dry gaseous form, depriving the latter of any liquidentraininent. No substantial cracking of the oil vapors takes place within the drying tubes 117 and these tubes are of sufficient diameter or cross-sectional area that if any coke or free vcarbon is formed in the drying operation it may accumulate within the tubes 11 without interfering with oil vapor flow through said tubes. From time to time the tubes 11 may be cleaned to remove carbon deposits therefrom, although such cleaning is an infrequent operation.

Also supported in the tubechamber 4 below the tubes 11 is a coil 13 composed of a plural- A ity of serially connected tubes through which steam may be passedfor superheating purposes, such a coil 'being an advantage in connection with cracking systems wherein steam is utilized. In the lower part of the chamber 4 auxiliary burners 14 are provided which may or may not be used depending upon the l through the length thereof are upright pipes 17 provided with control valves 18. The pipes 17 terminate in fittings 19 from which project laterally and horizontally extending branch pipes 20. These branch pipes in turn are connected with flaring distributor heads or secondary manifolds 21, which are arranged horizontally in advance of the front wall of the converter setting. Arising from each of the distributor heads are vertically disposed pipes 22 each of which being provided with a regulating valve 23.

The upper ends of the pipes 22 are connected with horizontally disposed fittings 24 to which are secured the forward ends of a plurality of horizontally arranged parallel cracking tubes 25. These tubes pass through ings formed in the upper portion of the bridge wall 2 and extend horizontally across the top of the tube chamber 4 and thence through openings provided in the rear wall 9 and have their ends, beyond the setting walls, connected with fittings 26 in which are arranged thermocouples 27 or other temperature recording instruments. The thermocouples are united by lines 28 with potentiometers 29 arranged at the front of the setting where they may be'readily viewed by the operator who, by noting the oil vapor temperatures at the ends of the tubes 25 may regulate the control valves 18 and 23 to secure desired temperature adjustments. The span of the tubes 25 over the chamber 4 is supported by means of braces 30 which arise from and are secured to the anchor plates 31 in which the tubes 11 and 13 are carried. These braces prevent sagging of the tubes Linder the iniiuences of high furnace temperatures. The span of the tubes 25 in the combustion chamber 3 is relatively short and since these tubes are formed from-metals which resist high temperatures noextra support for the tubes in the chamber 3 has been considered necessary. Preferably, the tubes 25 contain chromium or are protected by an aluminum oxide coating.

The anchor plates 31 support within the tube chamber 4 a plurality of converting:

tubes 32 which are of greater cross-sectional area than the tubes 25. These tubes are arranged in horizontal rows and the tubes are united by return bends (not shown) so that the oil vapor undergoing conversion reactions will flow serially therethrough. The vapors discharged from the tubes 32 possess a temperature usually in excess of 1000o F. although this temperature, of course, may be varied depending upon the particular cracking system which is employed. The smaller cracking tubes 25 provide for high velocity or flow of the oil vapor therethrough in order that the oil vapor may be brought up to a desired cracking temperature in a short period of time. Thus oil vapor may enter the tubes 25 at a temperature of approximately 700o F. and when discharged from the ends of the tubes 25 the vapor possesses a temperature usually in excess of 1100o F., although this temperature may be as low as 1000o F. After a desired cracking temperature has been attained such high velocities are no longer required since the element of time is then involved. For this reason the larger cracking tubes 32 are employed through which the oil vapor iiows serially at a lower velocity but is maintained in a furnace area possessing a temperature sufficiently high to keep the oil vapor above gases following their discharge from the 'p are avoided. The converted vaporsleave the tubes 32 by Way of the line 33 yand are led to separating, fractionating and condensing i equipment (not shown) of any suitable type current flow with the cracked oil vapors so that the heat of such gases is effectively absorbed by the walls of the tubes 32 and transmitted to the oil vapor passing therethrough. This constantly reduces the temperature of the furnace gases so that the latter will possess a desired temperature when engaging with the Walls of the drying tubes 11, permitting of the drying of the oil vapors passing through the tubes 11 Without any appreciable amount of cracking of the oil vapor. The heat of the cooling furnace gases may also be used for the superheating of steam passing through the coil 13.

Leading from the bottom ofthe chamber 4 is a laterally extending outlet4 duct 34 which leads to a vertical stack 35. Vithin the duct 35 there is` arranged a bank of vaporizing tubes 36 which are heated by the remaining heat contained in the furnace chamber 4. In some instances this heat is suilicient to vaporize the oil passing through the tubes 36. If for any reason it is not, one or more of the auxiliary burners 14 may be employed to secure the desired added temperature. Heretofore it has been customary to place the vaporizing tubes 36 in a separate setting corresponding generally in construction to the setting 1 and utilizing, in some instances, the waste heat from the high temperature converting unit. By the present invention the vaporizing of the oil is secured with the same degree of effectiveness by loeating the tubes 36 in the duct 34 and at the same time avoiding the expense of building and maintenance costs of a separate setting. The charging stocks are introduced in liquid form into the inlet side of the tubes 36, and after circulation through the tubes 36 the stocks are reduced substantially to a vaporous form. From the tubes 36 the vaporized oil is transferred by the pipe 12 to the dry tubes 11. Liquid traps (not shown) may be employed in the line 12 if desired.

From the foregoing it will be seen that the present invention provides an oilk converter wherein dry vapors enter the highly heated Zone and wherein the vapors are split into a numberV of parallel streams, each stream being under manual or automatic control by means of a valve 18. Each stream is further split or divided into a number of smaller streams by the employment of the flaring distributors 21 and I employ this construction for the reason that I find, in ordinary constructions, that there is an unequal distribution of heat from the side walls of the converter toward its center, the tendency being for the center tubes, i. e., corresponding to the tubes 25, to receive more heat than the, tubes near the outer walls. l For instance, in the case of an ordinary 60 tube converter, the present invention provides for the control of the flow of vapor through the 12 valves designated at 18. Each of these valves serves 5 tubes, the vapor distribution being taken care of by the heads 21. By means of the thermocouple disposed at the endof the first pass of tubes 25 and a potentiometer located at a point convenient to the valves 18, the latter may be adjusted so as to give as nearly as possible uniform vapor temperatures at the far ends of the tubes 25.' Y

The importance of this control is disclosed by thefollowing table setting forth temperature readings obtained from the operation of an ordinary 60 tube converter wherein all the tubes are fed with oil vapor from a common manifold:

plq Tubes 31 to 35-ave1age temperature end of first pass 1174 Tubes 41 to l5-average temperature end of rst Tulpes 5G to (S0-average temperature end of first 11290 From the above table it will be observed that there is a gradual rise in temperature towards the middle of the converter, with the lowest temperatures adjacent to each side wall. Such a condition can be rectified by the present invention, since by throttling on the control valves 18 and 23 of those tubes nearest to the side walls, the quantity of vapor passing through them can be reduced and, therefore, the temperature of the vapor raised. This, in turn, will force more Va,- pors through the tubes closest to the center of the furnace and this will result in a corresponding decrease in vapor temperatures existing in the center tubes. I, therefore, obtain a more uniform temperature at the end of the first pass of tubes, which greatly increases the efficiency of cracking, since under previous conditions the vapors going through the center tubes were overcracked, vand the vapors passing through the tubes closest to the sidewalls were undercracked, `the former affecting the percent yield of gasoline from gasoil, and the latter reducing the quantity of gasoline produced per day.

Another feature of importance is the placing of the vaporizing tubes, ordinarily known as economizers, in the gas duct leading to the stack. lVhile this change does not produce any appreciable increase in eiiiciency over the employment of an extra setting, yet it somewhat improves the ease of handling the unit, reduces heat losses by radiation and further reduces the cost of construction lidi and maintenance. When the converter is being placed on stream, that is, when initially brought into operat-ion, I circulate sufficient steam through the steam superheater 13 and the drying tubes 11 to permit the auxiliary burners 14 in the rear of the converter to operate at fairly high temperatures without injuring the tubes above. There will always be a strong down draft through the rear port-ion of the converter, which tends to keep the tubes above cool while the converter is being heated up or while going on stream. This, therefore, serves to prevent flame impingement on the tubes 11 and 13 which would be of a. destructive character.

`While I have described in considerable detail the several features of my present in,- vention and a specific construction for securing the objects and advantages above pointed out, yet it will be understood that my invention is not limited in scope to the structural details above described and illustrated in the accompanying drawing, but is susceptible to such variations and modifications as may be said to fall fairly within the scope of the following claims.

What is claimed is:

1. A converter for cracking oil vapor comprising a setting divided internally by a bridge wall into combustion and tube charnbers, a plurality of small parallel tubes` arranged in the upper portion of said converter and extending openly across the upper portions of the combustion and tube chambers, a manifold to which oil vapor is supplied, pipe connections between said manifold and the inlet ends of said tubes, valve means provided in conjunction with said connections for regulating selectively the quantity of oil vapor admitted into said tubes for passage therethrough, a manifold connected with the outlet ends of said tubes, a bank of tubes disposed in said tube chamber communicating with said last mentioned manifold, the tubes of said last named bank being of greater cross-sectional area than said rst named tubes, and heat generating means arranged within said setting for heating oil vapors passing through said tubes to converting temperatures.

2. A converter for cracking oil in the vapor phase comprising a setting, a bridge wall arranged in said setting and dividing the latter into combustion and tube chambers, a plurality of tubes of small cross-sectional area positioned horizontally in the upper part of said converter and extending across said bridge wall and said combustion and tube chambers, an inlet manifold for supplying oil vapor to all of said tubes, adjustable means between said manifold and the inlet ends of said tubes for controlling selectively .the quantity of oil vapor passing through said tubes from said manifold, and a bank of converting tubes of greater cross-sectional area than said first named tubes arranged in said tube chamber below said rst named tubes and in direct communication with the latter.

3. In a converter for cracking oil in the vapor phase comprising a. setting, there being a bridge wall arranged in said setting to divide the latter into combustion and tube chambers, lheat generating means arranged in said combustion chamber to admit 0f the flow of furnace gases upwardly through said combustion chamber, over the top of said bridge wall and downwardly through said tube chamber to an outlet, a row of horizontally arranged tubes mounted in said setting inA relatively parallel relationship and arranged in the upper portion of said setting, said tubes possessing relatively small crosssectional area, an oil vapor manifold arranged exteriorly of said setting, a plurality of oil vapor distributing heads connected with said manifold, a plurality of pipe connections leading from said distributing heads to the inlet ends of said tubes, valve means arranged between said manifold and the inlet ends of said tubes for controlling selectively the quantity of oil vapor passing through said tubes, and a bank of communicating tubes arranged in said tube chamber below said first named tubes and through which the oil vapor is passed following its travel through said first named tubes.

4. In a converter for cracking oil in the vapor phase, a setting formed to include a heating chamber, heat generating means disposed within said chamber, a plurality of oil converting tubes arranged within said chamber, an oil vapor manifold arranged exteriorly of said setting, oil vapor distributors connected at longitudinal intervals with said manifold, regulable valve means for controlling oil vapor flow from said manifold to said distributors, and a plurality of pipe connections between each of said distributors and the inlet ends of said tubes, said valve means serving to regulate and relatively vary the quantity of oil vapor passing through localized groups of said tubes.

5. In a converter for cracking oil in the vapor phase, a setting formed to include a heating chamber and a tube chamber, a plurality of cracking tubes of relatively small cross-sectional area arranged horizontally in the upper portion of said heating and tube chambers, an oil vapor manifold, a plurality of valve connections between said manifold and the vapor inlet ends of said tubes providing for parallel multiple stream flow of oil vapor through said tubes, and secondary converting tubes of greater cross-sectional area arranged in said tube chamber through which the oil vapor is passed serially when discharged from said first named tubes.

In testimony whereof I affix my signature.

AUDLEY E. HARNSBERGrER.l

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