US1955264A - Process of and apparatus for the development of volatiles from hydrocarbon substances - Google Patents

Description

April 17, 1934. L. J. WALSH PROCESS OF AND AP F FARATUS OR THE DEVELOPMENT OM HYDROGARBON SUBSTKNCES OF VOLA'IILESl FR Patented Apr. 17, 1,934

PROCESS or .AND

DEVELOPMENTv F APPARATUS FOR THE VOLATILES FROM i maocAaBoN sUBs'rANcEs Louis J. Walsh, Belmont, Mass. Application May 5, 1926, serial-N0. 106,873

4 claims. (c1. 19e- 4.9)

This invention relatesto treating mineral hyi drccarbons to produce-` gasoline, and to produce other hydrocarbons susceptible of use as cycle stock for re-treatment` inthe process, and

5 other uses.` Y 1 `Objects of the invention are to improve the efficiency of heat treatment in liquid phase as measured by the rate. of cracking o r conversion of material treated during a unit ofthe time the material is kept under cracking `or conversion conditions; to increase the proportion of gasoline volatiles obtained at 'each 'passage through cracking apparatus of the material treated; .toobtain the saidresults with a .minimum production of 1:5` undesirable end products such as fixed gases and free carbon; to reduce the amount of fuel re# quired to produce a unit quantity of gasoline volatiles; and to reach these results byy steps capable of performance in simple and safe apparaby preliminary tus having no large vessels containing oil under high pressures at high temperatures;` and to provide apparatus of the said characteristics.

Une of the objects of this invention is to avoid treatment by heat of ready containingl more than a critical proportion of cracked volatiles, for thel purpose andn with the result of facilitating the rapiddevelopment of cracked volatiles at moderate degrees of heat,

with the end results of a maximum development of cracked volatiles in relation to the degreeof heating, avoidance of any undue production of fixed gases, tar or coke, and maximum development of volatiles in relation to the volume of oil retained in the treatment apparatus. Practices according to the invention include treatment of liquid hydrocarbon materials by subjecting the materials to successive increments of increase of temperature and/or decrease of pressure, of temperature and/orpressure, or both, and concomitantly withdrawing, upon each recessional stage of treatment, a fractional portion of the charge corresponding substantially to the volatile fraction produced under the conditions of a preceding stage of treatment. Practice of the invention further includes causing the n on-volatilized fraction or residue of the treated oil to be recovered at each stage of treatment in a condition susceptible of further continued thermal treatment and conversion and in a state free from undue gmnmy inclusions and carbon. vAncillary features of the procedure recommended include conservation of attained heat and maintenance of volume under treatment, for example by the concurrent addition of fresh hydrocarbon mahydrocarbon material alof volatiles as vapor;

with intermediate alternate recessions terial or cycle stock to the hydrocarbon material during or `after each stage of withdrawal of volatiles and of temperature and/or pressure reces-l sion, to make up volume substantially to compensate for a fraction removed in a vaporized 60 condition. The process thus provides for continuity of treatment, conserves heat, and reaches a high thermal efficiency.v

A typical instance of practice of the invention will now be described as carried out upon vcrude petroleum as the initial charging stock, as an example only of a'process according to the in' vention. In'the accompanying drawing:

Fig. 1 is a diagrammatic flow sheet and elevation partly in section of suitable` apparatus; and

Fig. 2 is a curve vplotted in relation to Fig. 1` illustrating a typical sequence of temperature changes.

The steps of the treatment may be practiced heating of the raw material entering the apparatus through a pipe 1; separation or topping of the material, a preliminary cracking treatment, a temperature-pressure reduction and withdrawal of volatiles as vapo a second cracking treatment, asecondtemperature-pressure reduction, and withdrawal of vola v Vtiles as vapor; a third cracking treatment, a third temperaturefpressure reduction and withdrawal further.` stages of cracking, if desired, with temperature-pressure reduc- `tion and withdrawal of volatiles; return of the,

unvolatilized hydrocarbon from the last `crack-- ing treatment to the topping or separation vstep in the process; selective reflux fractionation, and condensation of the withdrawn vapors; and-withdrawal of fractions of thevolatiles to storage; and fractionation and condensation of part of the material for further cracking treatment or passage to storage.

The apparatus illustrated comprises a Vfeed pump 2 delivering to a feed line 3 and through heat exchangers 4, 5 and 6 to a preheater 7, which may be any suitable pipe coil in a furnace 8, and. thence through valvedconnections 9, 10, alternatively or concurrently to a topping still 12 or a vaporizer tank 13. But any part of the effect of the heating devices 4, 5, 6 or 'l may be dispensed with on occasion, for example when the feed-stock is a material already deprived of natural volatiles, and for this purpose valved by-passes 15 from pump 2 to feed line 3 and 16, to provide a shunt around preheater 1, may be used to carry all or a portion of the flow from pump 2.

It the material contains volatiles of the gaso- 11g van .thi-ee, of cracking units, preferably made as long y line range, it is desirable to separate these before the remainder of the treatment, and for this purpose the topping still 12, suiiciently heated (by furnace 14, and/or furnace 8, and/or heat exchangers 4, 5 and 6) receives the ow from pipe 3 in the first instance. A-vapor pipe 11 from still 12 leads to a primary fractionation tower 20, from which the bottom condensate may return to still 12 through a valved pipe 27 or be returned to vaporizer 13 through a valved pipe 27B. The tower 20 may be the primary tower for fractionation of cracked volatiles also, as presently mentioned. Preferably the tower operates in relation to a secondary tower 21 from which the bottom condensate may also ow through a valved pipe 17 to still 12. Still 12 may therefore be operated, when not receiving material to be topped from pipe 3, as a heater for maintaining the rectifying operation of tower 20 or 21, or both. Still 12 may also be operated as a storage receiver for material which it is desired to pump through the cracking stage of the apparatus.

If the material to be cracked contains portions of the asphaltic range it may be desirable to separate these before the remainder of the treatment, and for this purpose the vaporizer tank 13, sufciently heated by furnace 14, or preceding heaters, receives the ow from pipe 3 in the rst instance. vA vapor pipe 56 from vaporizer 13 leads to primary fractionation tower 20, from which the bottom condensate may return to still 12 through pipe 27. The portions of the asphaltic range remain in the liquid state and are drawn off through valve 57 and cooler 58 to storage.

'I'he uncondensed vaporous efllux from tower 20 may pass over to tower 21 by pipe 19 through a reux condenser, which may comprise one side of each of the feed line heat-exchangers 5 and 6. Tower 21 may have a reflux condenser comprising one side of the heat-exchanger 4, operating at a lower temperature than the heat-exchangers and condensers 5 and 6. Vapors passing the exchanger 4 through pipe 22 are the more volatile fraction of the output of this process, preferably are condensed in the water condenser indicated at 24, and the liquid product ows to storage in the gasoline tank 25 through pipe 26.

The topped, untopped and/or separated hot material flowing through still 12, and recycled material from valved pipes 27 and 17 and,'when desired, liquid from vaporizer tank 13 flowing through a valved pipe 29, comprise together or severally treatment stock to be cracked for optimum development of gasoline-range volatiles according to this process. For this purpose the pipe 28 delivers to a hot oil pressure-feed pump 30 delivering to a pipe 31 leading its flow in series through'any desired number, shown as convoluted pipe coils33, 34, adapted to be heated in independently regulated furnaces 36, 37, 38 respectively.

Bearing in mind that the pump 30 delivers a, relatively hot feed stock in the pipe line 31, the cracking unit 33, 36 (and succeeding units in turn) may be relied upon to carry the temperature of the oil in liquid phase to selected maximum cracking temperature, optimum for the material be treated, its rate of flow, and

is to say, a proportion of developed volatiles from the heat treatment according to a preferred step in the process, which is to produce in and of the material treated not to exceed from 10 to 15% by volume of developed volatiles included in the heated stream of material at any place in the series of steps of the treatment.

The purposes of this limitation upon the development of volatiles include avoidance of premature development of vapor in the coil 33, having regard to the pressures and temperature. This, in turn, results in an exchange of heat of high efficiency between the furnace 36, through the walls of the coil 33 to the liquid oil, which is in agitated flow because of the convoluted coil 33. Moreover, it is observed and relied upon that the presence of more than 10 to 15% of developed gasoline volatiles is inhibitory to the further development from the fluid containing this percentage of any further proportion of gasoline volatiles. While Athe causes of this phenomenon are obscure, the fact is that the heat treatment of a petroleum fraction, containing no cracked volatiles, results in the first stage of treatment in a much faster development of the desirable range of volatile products than it does at a later stage, if nothing has been done to strip the reacting volume of oil of its volatiley inclusions.

It is, therefore recommended that the respective cracking units be connected in series by pipes 40, 41, etc., in whichrespectively (depending upon the number of cracking units) are interposed intermediate vaporizing chambers 45, 46, etc., the flow in series through the cracking units passing through the chambers and 46 and from the final cracking unit 35, 38, passing by the educt pipe 42 and pressure-reducing valve 43 to the vaporizing tank or receiver 13 above mentioned.

The intermediate vaporizers 45, 46, are preferably of sufficient capacity to permit their contents to act as relatively still pools in the stream under rapid flow at other points in the system; regarded as a part of the flowing stream, their contents undergo av recession of temperature, which may be the consequence of reduced pressure or of admixture with cooling material; or, particularly, the effect of vaporization at a slight reduction of pressure of the vapors of the volatile substances and gases produced by heat in the preceding stage of heat treatment.

Referring to Fig. 2, which plots in coordinate relation with Fig. 1 the attained temperatures, temperature at exit from the flrst cracking unit material and the pressures, between 840c F., but during stay in the intermediate vaporizer 45 these temperatures drop materially, for example through about 10 F., so that if the attained temperature is 840 the temperature in the vaporizer 45 may be about 830; and if the temperature at exit from coil 33 is 900, the temperature in vaporizer 45 may be about 890. The vapor eflluent from the material in the vaporizer 45 flows vaway through the valve 48 and the manifold vapor pipe 50 to the bottom of the tower 20.

The loss to vapor in the vaporizer tank 45 will reduce the volume of the contents flowing in the system unless compensated for. This loss is therefore made up or exceeded by the injection of fresh feed stock from the pressure feed pipe 31 through a valve 52. A similar pipe 53 and valve 54 may also be provided for the intermediate vaporizer 46 and any further intermediate vaporizers in the system. Regulation of the valves 52, 54, may be depended upon not only to make up the volume but sensitively to affect the temperature in the respective vaporizers through regulation of the admission of comparatively cool oil under comparatively high pressure from the pipe 31.

Referring again to Fig. 2, the second cracking unit 34, 37, may be operated either slightly to increase or merely to maintain the educt temperature of the liquid oil flowing from the preceding separator 45. This material, having lost substantially all of its volatile contents in the vaporizer 45,` is, in respect to volatile contents, in the same fresh condition as the material running to the primary cracking unit 33, 36,and cracking to produce another ten to fteen per centum of volatiles may proceed at the attained temperature at exit fromvaporizer 45 with high efficiency.

The operation the cracked material from the secondary unit 34, 37, may be now carried out in the intermediate vaporizer 46, exactly as described in connection with vaporizer 45, except that a drop oi temperature, which may be substantially through 10 F. of attained temperature will now` bring the material to temperatures ranging about 20 F. below the temperature at exit from the primary cracking unit 33, 36. Assuming that educt from the vaporizer 46 is at a temperature within the range of from 820 to 880 F., the tertiary cracking unit 35, 38, may be operated to bring up the temperature again to the temperature at exit from the secondary unit 34, 37; that is to say, in the described instance to temperature respectively ranging from 830 to 890 F. Vapors from the vaporizer 46 ilow into the manifold 50 through a pipe connection having a valve 55.

There may be' as many cracking 34, 37; 35, 38: as development from of the desired percentage The three cracking units example' only.

Whatever the number of cracking units the educt pipe 42 delivers the hot material from the the material at a single run of gasoline volatiles. shown are by way ci which .it is preferred to permit a drop of temperature to about 650 F. as indicated in Fig. 2. The thoroughly .evolved vapor at this temperature from the tank 13 is carried away by the pipe connection 56 to the bottom of the tower 20.

From time to time the non-volatile bottoms of the vaporizer tank 13 may be led away through the valved connection 57 and the cooling coil 58 to storage. This residue is useful as a fuel oil. Sometimes a ilow of cycle stock from the tank 13 is maintained through the pipe 29 and the pump 30, as mentioned above.

As mentioned above, the delivery of the gasoline volatiles from the rectifying towers 20, 21, is through the condenser 24 and pipe 26 to the tank 25. The material in the bottom of the tower 21 may vary, in accordance with the degree of the treatment, the nature of the original feed stock and other factors, through the boiling point ranges of kerosene, gas oil or high boiling gasoline. So much of this material as it is not desired to return through the still 12 may be cooled at the cooler 59 and flow to a storage tank 60 for this heavy distillate.

It will be obvious that the material supplied to the pipe 1 may be either crude petroleum or a of stripping the volatiles from( distillate substance; as above described the degree of preheating at 4, 5, 6 and 7 may be controlled, or preheating may be avoided by the use of the by-passes 15 and/or 16, all of the preheating then occurring in the still 12, which may serve as a primary heater for a distillate or topped crude, a'nd as a source of re-vaporizing heat' for the proper operation of the column 20.

VIf desired, any proportion of the incoming relatively cool charging stock may be delivered through the valve 9 into the vaporizer tank 13 to aid in a suitable reduction of temperature at this point. l I n It will be obvious that theprimary pressure in the cracking unit 33, 36 and in the pipe 31 is a function of the rate of the pump 30, and that the desirable value of this pressure has relation to the temperature at which the furnaces 36, 37, 38 are operated and the hydraulic resistance of the pipe system of the cracking units to flow; these factors of relationship of pressure and temperature are in turn determined by the nature of the material being treated and the desired degree of development of the gasoline volatiles. When the initial cracking temperature reaches the range of from 340 to 900 and the material is a crude oil, the typical initial pressure in the line 31 is about 700 lbs. per square inch; but this value is highly variable in practice, and should be so, to enable the result obtained of holding to liquid phase the flow in the successive cracking units. Naturally, the pressure in the second cracking unit is a lesser pressure, preferably by about 50 to 75 lbs. to the square inch; this pressure is measured by the pressure at which the vaporizer 45 at oil operates to permit vaporization of all or sub'- stantially all of the developed volatiles and gases. The further stages of the process operate under the same system of relationships, loss of hydraulic head of about 50 to 75 lbs. to the square inch at each cracking .unit reducing the pressure toward the end of the system, and being controlled by adjustment at valve 43, which is preferably so adjusted as to cause pressure in vaporizing tank 13 of about 50 lbs. to the square inch only above atmospheric pressure, having regard to the pressure in tank 13 imposed by the resistance to ilow through columns 20 and 21 and resistance beyond, including adjustment of flow at valve 61 and valve reducing valves 63, 64 may, if desired, be provided between each stage of cracking further to control the loss of hydraulic head stage of the treatment. A typical operating pressure at valve 43 is 550 lbs. above atmosphere.

The pressures in the rectifying columns 20, 21, may be suitably controlled at valves 61 and 62. It will be observed that at sundry places in this process, for example in the separators or vaporizers 45, 46 and 13, the vapors of the more volatile substances in the ow are permitted to separate according to their vapor pressures, the pressure against now from the container of the volatile substances and the temperature at that point. The imposed pressure and the temperature are factors of a condition permitting volatilization, the same results following when the temperature and pressure are higher, or when the temperature and pressure are lower. An expression for the integrated value of temperature and pressure when there is iiow off of vapor is,

4within limits, a measure of potential in relation to any resistance against which a volatile 62. Intermediate pressurefrom stage t0 2O ling heavier vapors by indirect cooling, an accumuwhen I refer in the claims to temperature-pressure potential I allude to this condition, whichever of its component factors is relatively high or low.

I claim:

said intermediate vaporizers.

2. In apparatus for the cracking of oil, the improvement which comprises a separator connected to receive the hot cracked product, pipes for separately withdrawingv vapors and tar fromthe separator, heat exch ange means for condensoils to produce gasoline, comprising cracking a liquid lwdrocarbon oil under high initial pressure in an elongated cracking zone so as to form not substantially more than 10%15% of gasoline volatiles therein, passing the cracked oil into a vaporizing zone, dropping the pressure through said zone by not more than 50-75 lbs. per sq. in., removing from the vaporizing zone substantially all the gasoline and more volatile hydrocarbons, passing the remaining oil as a liquid into a second rst cracking zone by not more than about 50-75 lbs. per sq. in. to form not substantially more than 10%-15% ofgasoline volatilesv in the oil, passing the oil cracked in said second cracking zone into a second vaporizingfzone maintained under conditions to permit evolution of the gasoline volatiles therefrom, and segregating such gasoline volatiles and the residual oil.

4. Method according to claim more than A10%-l5% of gasoline volatiles, and is then discharged at lower pressure and temperature into a vaporizing zone from which the gasoline volatiles are recovered and the residual oil removed. t

LOUIS J. WALSH.

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