US1971252A - Method for treating hydrocarbons - Google Patents

Description

g- 1934. w. M. cRos 1,971,252

METHOD FOR TREATING HYDROCARBONS Original Filed Oct. 2 1923 Patented, 21, 1934 omm imm PATENT OFFICE '1 I 1.011.252 I mrrnon roa rasa'rmo irrn'aooaaaoss' v Walter M. Cross, Kansas City, Mo. assignor, by

mesne assignments, to Gasoline Products COM-r pany, Inc, Wilmington, Del, a corporation of Delaware Application October so, 1923, Serial No. 671,591

I Renewed September 2'1, 1933 3Claims.

My invention relatesto the art of producins gasoline, and similar light hydrocarbons from fuel oil and similar relatively heavy hydrocarbons. a

This process is an improvement on .such proccases as are divulged by Patents No. 1,203,312 issued October 31, 1 910, No. 1,326,851 issued December 30, 1919, No. 1,423,500, issued July 18, 1922, and No. 1,437,229 issued November 28, 1922.

This application is a continuation in part of a previous application, .Serial No. 049.478, flied,

July 5, 1923.

,In the operation of a process explained by the above mentioned patents and particularly Patout No. 1,423,500 the oil is pumped through a coil or heating tube in the furnace from which it is discharged into a reaction chamber. 'Ihe reaction chamber and furnace tubes are maintainedat pressures controlled to cause the conversion of the oil undergoing treatment to take place while the oil is in substantially the liquid phase. By this operation, very little of the heat added to the oil isused in vaporization, practically all being utilized in bringing the oil to a 25 cracking temperature and then carrying out the cracking reaction. This method of operation results in a substantial conservation of fuel compared with other processes, the fuel consumption being'considerably less than in those processes involving distillation from the cracking zone. In normal operations, the oil which has undergone cracking, is released as a hot synthetic crude from the highpressure down to substantially atmospheric pressure resulting in the absorption of a large amount of heat in expansion and vaporization. In the case of kerosene and gas oil the amount of oil vaporized is sumcient to leave only a very small residue or bottom, which has the characteristics of fuel oil and ordinarily amounts to onlyfrom 5% to of the oil undergoing distillation. When a fuel oil is cracked, say of approximately Baum gravity, in place of the gas oil or kerosene, the synthetic crude issuing from the reaction chamber does not contain sumcient heat to distill ordinarily more than about 50% of the cracked fuel oil into benzine and gas oil, the latter being utilized as a recharging stock. The result is that this process, while operating on fuel oil to satisfactorily'crack it, does not supply enough heat tothe oil to obtain a sufllclently large percentage, of recharge stock, when the pressure is released, and without adding additional heat to the distillation stage. In some instances, when cracking kerosene or 1mm distillates, the amount vaporized by the "contained heat of the synthetic crude is exces- 'sive, leaving nothing but asphalt'and coke in tthleegaporizer when the synthetic crude is dis- The aim of the present invention is primarily, then, to supply a Process in which an oil of high viscosity is heated to a temperature high enough to distill oil a major portion thereof. This on while in the heated condition, is blended with oil either of the same character or of a diiierent character, which has previously undergone cracking and is existing in the form of synthetic crude. This blending or combining of the two oils while in a heated condition, accompanied by a reduction 'of pressure upon the synthetic crude, produces an increased amount of overhead products from .the synthetic crude. and also an increased distillation of the high viscosity oil, as the vaporization of the synthetic .crude has the action of steam promoting distillation in the oilwith which it is blended. Further, from the distillationof these blended products, there is produced a more fluid bottom which contains no considerable amount of 30 free carbon, thus giving a more marketable product. Among further objects of this improved process are the following:

l. A highly eiiicient tube still, suitable for the distillation of fuel oil, crude oil, topped crude oil, and emulsified oil, is used to heat such oil to a high temperature, and upon being discharged from the tube still the heated oilsare combined in a common vaporizer with cracked products, introduced thereto from the cracking process.

2. The vaporizer is used simultaneously for the redistillation of the cracked synthetic crude oil and for the production of distillates from oil introduced from the tube still. The expanded oil from the tube still has a higher temperature than the expanded synthetic crude with the result that the oil from the tube still aids in the normal distillation of the synthetic crude, and the synthetic crude, by reason of the evolution of light vapor and volatile fractions contained therein, aids in the distillation of the heavier product introduced from the tube still. This combination makes possible the running of any cracked heavy hydrocarbons, including oil, wax distillates, gas oil, and kerosene, without any excessive amount of residue in the vaporizer.

3. The process permits blending of high speciflc gravity and low viscosity o ls such as would remain from the distillation of the synthetic crude with high viscosity, and comparatively low 110 specific gravity fuel oil such as remains from natural crude, or natural fuel oil produced from the low pressure treatment'in the tube still. It is particularly adapted to the skimming of light crude oil, emulsified oil, or refinery slops, from which the gasoline, water, light distillates, as well as heavy di'stillates, may be removed. Such crude oils may be cycled through in such man ner that in the first cycle only the light distillates as well as the heavy gas oil are obtained, the crude being topped in the tube still.

The single figure shows the general layout of this type of plant. 1 is a line gathering the, oil from the source of supply not shown; 3 is the line gathering the oil from the fuel oil tank; a

2 is a valve in oil supply line; 4 is a valve in oil supply line from fuel oil tank; 5 is an intake line to pump 6; 7 is a charging line from charging pump to furnace; 8 is a furnace; 9 designates furnace tubes connected in series to form .a continuous coil; 10 is a furnace stack; 11 is discharge line from the tubes or 00119 in furnace 8; 12 isa valve; 13 is a charging line to evaporator; 14 is an evaporating tank or tower; 15 is a liquid level regulator; 16 is a valve controlled by regulator 15; 1'1 is an oil discharge line; 18 is a cooling box containing coils; 19 is a rundown line; 20 is a run-down tank; 21 is a vapor line; 22 is a dephlegmating tower; 23 is a level regulator; 24 is'a valve controlled by regulator 23; 25 is an oil discharge line; 28 is a run-down line; 30 is a gas separator; 31 is an oil line; 32" is a run-down tank; 33 is a gas discharge line; 34 is a furnace; 35 is an oil supply line; 38 is a pump; 37 is a pump discharge line; 38 designates economizer tubes connected in series to form a continuous coil-section; 39 is a transfer line; leading from the economizer tubes 38; 40 designates furnace tubes connected in series to form a continuous coil section; 41 is a furnace discharge line leading from tubes 40: 42 is a box elbow for control instruments; 43 is a reaction chamber; 44 is a pressure indicator; 45 is a transfer line; 48 is a pressure relief or reducing' valve.

It is understood that the character of the appa ratus and the manner in which the different stages are connected may be varied without departing from the spirit of the invention. Y

Briefly, the manner in which the process is cperated is as follows: Fuel oil, crude oil, topped crude oil, emulsified crude oil'or refinery slops are introduced through the line 1, valve 2 being open and valve 4 being closed. The pump 8 draws the oil inthrough the line 5 and discharges it through the line 7 into the furnace tubes 9 where it is heated to a temperature required to produce the amount of distillation required. When it is only required to skim the crude oil, the temperature would range approximately between 410 1''.

and 800 F. more or less. In treating fuel oil or topped crude oil the temperature would be in the neighborhood of 850 F. more or less, depending upon the particular requirements and the properties of the oil.

The oil passes through the tubes 9 at sufficient velocity to keep the walls of the tubes clean and scoured. The pressure ordinarily does not exceed pounds measured in transfer line 11, although higher pressure may be used under certain conditions. Normally during the operation the valve 12 is only partially opened so that the hot fluid oil passes out into the line 13 and thence to the evaporator or vaporizer 14. The pressure in the vaporizer is controlled by valves 4'1 and 48 and is normally at substantially atmospheric pressure, or from 10 to 15 pounds per square inch above atmospheric, according to character and amount of distillation required. All of the lighter fractions of the oil are vaporized, the vapors passing out through the line 21. It has been found advantageous to the operation of the process to position a separator or purifier such as a steam separator in the top of the vaporizer 14. The purpose of the separator (not shown) is to eliminate the entrained vapor or heavy fog carried along mechanically by the volatilizedoil.

The non-volatilized. oils accumulating in the ,bottoegi of the vaporizer 14 are discharged as controll by the level regulator 15 which operates the automatic valvb 18 and allows the heavy residual oil to pass out through the line 1'! through cooling coils and into the run-down tank 20 where the heavy fuel oil is accumulated. The vapors passing out through the line 21 are introduced in to the dephlegmating tower 22 which may be of standard construction. Suitable means for cooling this denhlegmator may be used such as air radiation, heat exchange, or the pumping in of a cooler liquid refluxing medium. Any benzine that may be present is carried over with the vapor through the line 28 and the refluxed products or residues accumulating in the bottom of the dephlegmator are discharged by control valve 24 operated through thelevel regulator 23. Theoil withdrawn from the bottom of the dephlegmator passes out through line 25 and cooling box 18 into tn; linetfi8 and thence to the run-down tank 2'1 w ere e gas oil and h collected. 7 eavier distlllateslare The benzine including the lighter va rs passing over the top of the dephlegmato through line 28 is directed through the cooling or condenslng box thence through the line 29 and gas separator 30 and finally to the run-down tank 32 through the line 81.

The gas from the gas separator may be used circulated through the economizer tubes as.

From this section of tubes the oil is further circulated through the hotter portion of the furnace where it is raised to a cracking heat. In this condition it is directed through the transfer line at temperatures ranging normally between 800 to 900 F., depending upon the oil undergoing treatment. The oil inthe reaction chamber and the-heating tubes is substantiallly at the same pressure, there being merely such difference as will permit oil to fiow from one stage to the other at a high rate of speed. The period of travel, through the successive stages of treatment, is controlledto produce the desired amount of conversion in the particular type of oil treated. The reaction chamber is preferably heavily insulated against loss of heat by radiation, and appreciable influences of the atmospheric changes.

This treatment produces a synthetic crude which contains from 20 to 70 of ordinary commercial gasoline. The synthetic crude, at a temperature of 700 F. more or less, is discharged or released into the vapor column 14. Concomitant with this release of pressure, there is a vaporization of, say, from 50% to 98% of the synthetic crude, depending upon the quality of the oil therewith.

At this juncture. the synthetic crude is combined with the oil from the furnace tubes 9 in the common line 13 where the two are completely blended. Since the synthetic crude carries a considerable amount of gas, in addition to the vapors involved, it acts similarly to the injection ofsteam,

producing a vaporization of considerably more of the oil coming from the furnace tubes 9 than would otherwise .be the case. At the same time, the oil coming from the furnace tubes 9 has a higher temperature since it has not been subjected to considerable cracking and is not cooled by its release through valve 12 as the pressure drop is relatively slight. The-result is that it has a considerably higher temperature and raises the temperature of the synthetic crude causing more of it to vaporize. Such being the case, approximately 70% of the oil coming from the reaction chamber 43 is vaporized even when fuel oil is used as a charge stock to the cracking stage; whereas, if the two oils were not blended in the manner explained, probably not more than, say, 50% of the oil would be vaporized.

The fuel oil residue unvaporized in the column 14 is drawn of! and collected in the run-down tank 20. The vapors of-benzine, gas oil, as well as the fixed gases, pass over through line 21 into the dephlegmator tower 22. In this tower,

relatively heavydistillates-including the gas oil cut-are refluxed and are drawn oil into the rundown tank 27. This tank normally contains both the original charging stock or gas oil and recharging stock resulting from the refluxcondem sation of the vapor in the dephlegmator. The benzine, including the more volatile fractions and fixed gases, passes over from the top of the dephiegmator through the line 28 to a gas separator 30 wherein the gases and liquid are divided, -the gas being utilized either for fuel or in the production of gasoline similar in character to casinghead gasoline while the liquid is collected as distillate in tank 32.

The fuel oil, gas oil, distillate, kerosene or' topped crude, may be treated in the cracking furnace, but ordinarily a greater total yield of light distillate is obtained by treating the heavy oil first in the furnace 9. I

The process permits a larger ratio of ultimate gasoline yield to the carbon formation particularly as applied to fuel oil.

When a fuel oil is subjected to more distillation and a considerable portion distilled off, the resulting bottom is a heavy viscous substance like asphalt; on the other hand, where fuel oil is subjected to a cracking reaction there is an excessive formation of carbon producing a bottom which is contaminated with an objectionable amount of free carbon. If, however, the fuel oil is only partially cracked and is blended with the synthetic crude, such as that explained, the resulting bottom contains but a small amount of free carbon which is not objectionable. This latter product is readily marketed while an oil containing considerable quantities of free carbon, such as is contained in the cracked product, must be blended with gas oil or the like to be utilized commercially as fuel oil.

Further characteristics which have been noted in the blending of oil and distillates while in a heated condition, are that they are more susceptible to treatment, permitting objectionable qualities to be more readily eliminated than when blended in a cold state. For example, benzine j v 4 1971 95b charged and a corresponding temperature, drop recovered from the oils blended while in a heated condition, may be more readily decclorized, also a recharging stock recovered by the blending of the products as herein explained may be retreated in the cracking stage with less premature carbon deposition than a recharging stock recovered from the normal treatment of oils.

The t pping furnace is much less expensive to construct than the cracking unit as the material is not required to withstand the excessive pressure to which the cracking portion of the apparatus is subjected.

I claim as my invention:

i. A- process of treating hydrocarbon oil comprising charging oil of relatively diil'erent molecular weights toseparate stages of treatment, subjecting a heavy charging oil in one heating stage to a temperature sufdcient to distill oi! as major portion thereof without substantial cracking, subjecting a relatively light oil consisting substantially entirely of a normally liquid distillate oil stock in the second stage to heating to raise it to a cracking temperature and thence passing the heated oil to a separate reaction zone wherein it is maintained at. the desired cracking 10o temperture while maintaining the oil under pressure regulated to produce cracking substantiallyin the so-called liquid-phase, blending the oils from the separate stages and distilling oh the volatile portions of the combined oils under substantially atmospheric pressure in a separate vaporizing stage wherein the lighter'fractions of the combined oils are evaporated and there is produced a fuel oil residue having a high degree, of fluidity and a low content of free carbon, iw subjecting the vaporized portions to a fractionating operation and thence to a final condensing operation, withdrawing reflux condensate from said fractionating operation and supplying it to the said second stage as distillate charging stock therefor, withdrawing the unvaporized residue from the vaporizing stage, and mixing unvaporized residue so withdrawn with the charging stock supplied to the said heating stage first named.

2. A process of cracking heavy hydrocarbon oils which comprises heating a heavy oil in a coil to a temperature suificient to vaporize a large portion thereof but insuilicient to crack a substantial portion of the oil, passing the oil to a vaporizing stage, simultaneously passing a lighter oil consisting substantially entirely of a normally liquid distillate oil through a heating coil under a pressure above three hundred pounds to heat it to a cracking temperature and thence passing the oil through a separate reaction zone where substantial cracking occurs, reducing the pres-' sure on the cracked products and introducing them into the said vaporizing stage wherein the lighter fractions of the combined oils are vaporized and there is produced a fuel oil residue having a high degree of fluidity and a low content of free carbon, withdrawing residue from said vaporizing zone and mixing residue so withdrawn with the charging oil supplied to said first mentioned coil, fractionating the vapors separated ln said vaporizing zone, and passing reflux condensate from said fractionating operations to the second mentioned heating coil as distillate charging stock therefor.

3. A process of treating hydrocarbon oil comprising charging oils of relatively different characteristics to separate stages of treatment, passing one of the oils which consists of a relatively heavy oil stock to a stage wherein it is subjected to a temperature suiiiciently high to distill off a 150 -mnjo2- yortion but cient to creek a sub stantiaiportion of the oil, passing the other oil which consists of a normally liquid distillate oil stock in a. stream through unheated passageway where heatis supplied at n mpid rate to mine it w a, cracking temperature, but withnut efiecting substantial decomposition, thence mg the heated oil to a seperatereaction zone where cracking occurs aummntinilyin liquid phase, re ducing the pressure on the oil otter leavinr said zone, blending thetrented oils from both stages in n distilling zone wherein the lighter tmtione therefor.

WALTER M. CROSS.

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