US2086741A - Method of converting hydrocarbon compounds - Google Patents

Description

July 13, 1937- vA. P. sAcH's METHOD OF CONVERTING' HYDROQARBQN COMPOUNDS Patented July 13, 1937v METHOD or coNvEa'rlNG nYDaocAmsoN COMPOUNDS Albert P. Sachs, New York, N. Y.,

Petroleum Conversion Corporation,

assignor to New York,

N. Y., a corporation of Delaware Application April 4, 1935 Serial No. 14,554

4 Claims.

My present invention relates to conversion (cracking) of hydrocarbon oils in .the vapor phase with the aid of a carrier gas. In the patent to Beardsley and Colony No. 1,842,319, for example, there is specifically disclosed a method of cracking in which the oil to be cracked is first vaporized and the vapor superheated to a temperature within the cracking range but with such rapidity of heating that no substantial cracking of the vapor in the superheating zone takes place, whereupon the thus heated vapor is mingled with a hot gas constituting a heat carrier under conditions which cause the oil vapor to undergo cracking at a temperature at least as high as that of the superheating. I have since discovered that the heat carrierV gas plays two important roles, one to provide the heat necessary for cracking, and the other to provide what might be called the mass-temperature effect in cracking. 'I'his conception of mass-temperature effect or, more briefly,` mass effect is quite separate from that of the heat carryingl effect and the purpose of my present invention is to provide for this mass effect even when the necessary temperature is otherwise properly provided for. l

My present invention is predicated upon my discovery that it is possible to heat the oil vapor to a temperature in excess of the mean cracking temperature (and hence the "heat carrier" gas provides no heat for cracking) provided the time during which said temperature in excess of the meancracking temperature is maintained is suinciently short to prevent substantial cracking. For example, the vapor may be superheated to a temperature around 1050 degrees F. by any suitable means and then mingled with, for example, an equal weight of gas at a temperature of 950 degrees F. thus producing a mix temperature of 1000 degrees F. and an average cracking temperature of about 990 degrees F. (Y

Thus the heat carrier gas, even though at such a lower temperature than the vapor as to provide none of the heat necessary for .initiating cracking, nevertheless contributes a mass heating effect thereto, thereby decreasing drop in tem- I0 into vaporizer II from which the heated oil I2 and peraturenue to radiation and to heat absorbed-by the endothermic cracking reaction and maintaining the average cracking temperature at a higher level. The presence of the gas, moreover, irrespective of its temperature, is also valuable in that it reduces the partial pressure of the vapors thereby favoring the formation of dehydrogenated compounds, which is desired.`

A further and important advantage of my process arises from the fact that it is vin practice more satisfactory to transfer heat through, say, a

tube or other heating surface to a vapor than it is to a gas because of the highervolume specific heat of the vapor. Thus, tubes for heating gas of low specic gravity such as would be used in the present process and which therefore has low heat capacity per unit of volume, are more subject to the danger of being burnt through easily than those tubes which are used for heating a vapor 'which has a relatively highspecific gravity and high volume specific heat, say ten times or more that yof the gas. Therefore, it is a distinct gain to be able to moderate the temperature to which the gas is heated and transfer the heat load to the vaporv heating tubes with a greater density of contained .material The problem of heating.

large quantities of gas such as are required in a vapor phase process of this type is one which has received serious consideration on the part of petroleum engineers. Apart from the possible use of combustion gases as a heat carrying medium, the means which have been available to heat a stream of gas have been either aregenerative heater or a tube heater.` .Regenerative heaters have the great merit of being able to supply large quantities of hot gasat high tempera- ,tures over long periods of time withoutinterruption dueto break-down. vTubeheaters, on the other hand, while having the advantage of lower first cost have been open to the disadvantage that tubes were prone to burn out. The present invention while contemplating the use of any source of gas at the requisite temperature makes practicable the use of tube heaters with their attendant low first cost.

My invention-will be best understood by refi and vapor mixture passes through pipes I3 to flash drum I4, the iiashing operation being assisted preferably by means of a stream of gas I introduced through pipe I3 from the gas heater Y I5, being supplied thereto through pipe I6. The amount of flash gas, however, is insufficient to have any appreciable eiect upon the cracking operation. The vapor so produced which is substantially dry owing to the action of the hot gasused in the flashing operation is then led from the ilash drum through pipe |8 to superheater I9 wherein its temperature may be raised rapidly from its' vaporizing temperature, say 700 degrees F. or under, to a temperature as high as 1100 but preferably in the range of 1000 to 1050. The superheated vapor then passes at high velocities to a mixing chamber wherein it is commingled with a mass-eiect gas admitted thereto i. through pipe 2|, said gas having been heated by means of the heater 22 with which gas inlet pipe I6 communicates. The temperature of the mass effect gas may be accurately regulated by admitting slight quantities of relatively cold gas as required from the pipe I6 into the pipe 2| through the valved pipe 23. From the mixing chamber 20, the mixture of hot vapor and gas passes through pipe 23a to the reaction chamber 24 wherein opportunity is given the vapor to crack by reason of the temperature range over which it is maintained for a suitable period of time. The cracked vapors are then conducted from the reaction chamber to the fractionator 25 functioning to condense fractions heavier than the gasoline. The vapor of the latter leaves the fractionator through pipe, 26 and passes to condenser 21 wherein the gasoline fractions are condensed out and are collected in an accumulator 28. The residual gases plus vapors which remain uncondensed pass through pipev 29 into an absorber 30 wherein the light vapors are stripped from the gases, the latter leaving the absorber through pipe 3|. Part of the gas may be then stored in gas holder 32 while the remainder is recirculated back into the system through pipe 33 connecting with pipe I6. The recycled gas consists principally of hydrogen and methane with smaller quantities 0f the lower hydrocarbons such as ethane and ethylene and propane and propylene and other hydrocarbons.

The amount of gas added will be determined first of all by the temperature range over which it is desired that the cracking take place and secondly by the temperature of the gas. In general, the process ceases to be highly economical when the temperature of the gas added is more than say 100 degrees F. below the temperature of vapor. Also, I have found an initial cracking temperature of around 1000 degrees to be desirable as producing a gasoline having good antiknock qualities and low gum content although temperatures as high as 1100 degrees may be employed should special circumstances require it, 0r a temperature lower than 1000 degrees, as for example a temperature slightly above 900 degrees, may be used. 4

I claim:

1. In the method of converting petroleum oils into compounds suitable as motor fuels, the steps which consist in subjecting the petroleum oil to vaporizing conditions, superheating the produced vapor in a superheating Zone to a temperature between 950 and 1100 F., but passing the vapor through said superheating zone so rapidly that no substantial cracking of the vapor takes place therein and then immediately passing the superheated vapor to a zone wherein it is mixed with a streamof heated gas having a temperature lower than that of the said superheated vapor but within 100 F. of said vapor temperature and in a proportion to establish an initial reaction temperature in excess of 900 F., allowing conversion of the vapor to take place by virtue of the heat present in said vapor-gas mixture by permitting a suitable reaction time to be effective, and subjecting the mixture to liquefaction conditions to separate out compounds suitable as motor fuels.

2. The methodaccording to claim 1 in which the gas added is of the order of equal weight of the vapor.

3. In the method of converting petroleum oils into compounds suitable as motor fuels, the steps which consist in subjecting the petroleum oil to vaporizing conditions, superheating the produced vapor ina superheating zone to a temperature between 950 and 1l00 F., but passing the vapor through said superheating zone so rapidly that no substantial cracking of the vapor takes place therein, and then immediately passing the superheated vapor to a zone wherein it is mixed with a stream of heated gas that has been heated to a temperature lower than that of the said superheated vapor but within 100 F. of said vapor temperature and in a proportion to establish an initial reaction temperature in excess of 900 F., allowing conversion of the vapor to take place by virtue of the heat present in said vapor-gas mixture by permitting a suitable reaction time to be effective, subjecting the mixture to liquefaction conditions to separate out compounds suitable as motor fuels, leaving a residual gas, recovering said residual gas, and carrying out the gas heating step of the next cycle by heating said gas inA a heater of the tube type.

4. In the method of converting petroleum oils into compounds suitable as motor fuels, the steps which consist in subjecting the petroleum oil to vaporizing conditions, superheating the produced vapor in a superheating zone to a temperature between 1000 and l050 F., but passing the vapor through said superheating zone so rapidly that no substantial cracking of the vapor takes vplace therein, and then immediately passing the superheated vapor to a zone wherein it is mixed with a stream of heated gas having a temperature lower than that of the said superheated vapor but Within 100 F. of said vapor temperature and in a proportion to establish an initial reaction temperature in excess of 900 F., allowing conversion of the vapor to take place byv virtue of the heat present in said vapor-gas mixture by permitting a suitable reaction time to be effective, and subjecting the mixture to liquefaction conditions to separate out compounds suitable as motor fuels. Y

ALBERT P. SACHS.

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