US1462247A - Treatment of hydrocarbons - Google Patents

Description

July 17, 1923. 1,462,247

I w. F. RITTMAN TREATMENT OF HYDROCARBONS File e 1917 2 Sheets-Sheet 1 WQMNJWWM WWW July 17, 1923. 1,462,247

' w. F. RITTMAN TREATMENT OF HYDROCARBONS Filel Feb. 5, 1917 2 Sheets-Sheet 2 WITNESSES INVENTOR Patented July 17, 1923.

UNITED STATES PATENT -TJFFICE.

WALTER F. RITTMAN, 0F PITTSBURGH, PENNSYLVANIA.

TREATMENT OF HYDROCARBONS.

Application filed February To all whom it may concern:

Be it known that I, WALTER F. Rrrr MAN, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, a citizen of the United States, have invented or discovered certain new and useful Improvements in the Treatment of Hydrocarbons, of which improvement the following is a specification.

In the cracking of heavy petroleum hydrocarbons for the production of low boiling hydrocarbons, it is desirable that a process or method of operation be available whereby all types of petroleum oils boiling above the highest boiling point of the loW boiling material desired to be produced, can be used instead of only certain types of high boiling hydrocarbons such as gas 011 and heavy fuel oil. Heretoforc it has been proposed to decompose or crack high boiling hydrocarbon products, such as those boiling above 27 5 C. in a still under pressure, and various methods of accomplishing this result have been proposed. Such operations are subject to the inherent difficulty of raising relatively low boiling oils, such as kerosene, etc., to an eificient cracking temperature without such a corresponding increase in pressure as to be beyond the limits of a still to withstand. As the commercially effective cracking temperature is generally in excessof 400 0.,

the difiiculty and danger incident to raising the oil having a boiling point at and below 275 C. to a cracking temperature in a still, will be clearly appreciated when it is recalled that to raise the temperature of water from 100 C. (its boiling point at atmospheric pressure at sea level) to 200 C. re-

quires a pressure of about 212 pounds. By reason of the operativedanger and difliculty above stated, more than one-fifth of crude petroleum cannot be treated by procemes above referred to.

It is well recognized in the art that in all pressure distillation processes today in operation, oils with a. Baum gravity lighterthan about 36 cannot be held in the-still until their boiling temperature is increased to above cracking temperature. -Theoretically, at lea-st, these oils can be held in the still until their cracking temperatures are below their boiling temperatures, but the practical limits of the material entering into the construction of the stills used for this purpose, have made it impractical to date,

5, 1917. Serial N0. 146,719.

ing temperature is lower than the b0iling temperature and the oil cracks before it boils. This invention recognizes this limitation of pressure distillation processes and through stage two, wherein the relatively lighter oils, just referred to, are treated in the gaseous phase, Where the question of boiling point has no relation to the physical strength of apparatus necessary, this limitation is avoided.

The present invention is a process involving two separate and distinct stages of cracking. In one stage, the oil in the form of a liquid in the presence of large quantities of gaseous products from the cracking of the same liquid (i. e. a two phase sys tem) is subjected to a temperature in excess of 300 C. and a pressure of 30 or more pounds per square inch; and in the other stage, the relatively low boiling hydrocarbone, but not sufliciently low boiling to be commercial gasolene, given off from stage one, are subjected while in a single gaseous phase, and where the liquid phase is substantially absent, to a temperature in excess of 400 C. and toa pressure in excess of 30 pounds per square inch. Opinions among petroleum technologists vary regardin the,

cracking of petroleum where both liqui and gases are present as in a pressure distillation process, as to whether cracking occurs in only the liquid subjected to the highest temperature and where one would naturally believe that practically all cracking took place, or whether cracking takes place both in the liquid and in the vapors above the pressure in excess of 30 pounds per square V inch, at high or cracking temperature and provision is made for segregating from the hydrocarbons formed in the still those having a boiling point at or below gasolene, i. e.,up to 150 degrees to 200 degrees (3., and for the re-treatment of a portion or all of the other hydrocarbons from the still, in a single or gaseous phase, forming the other stage of the process described herein.

In the practice of the invention, means for operation. are provided wherein crude oil, from which the low boiling parts have not been distilled, may be introduced lIltO" the distillation apparatus and the distillation carried on in the ordinary manner at atmospheric pressure until the desired low boilingparts have been removed. The distillation is then proceeded with under pressure and further low boiling products produced through cracking of the still contents. If desired, as soon as the gasolene is distilled ofi", materials boiling just above gasolene, but too volatile to be held in the cracking still, can be fed to the cracking retorts wherein the distillate'is vaporized and cracked into lower boiling hydrocarbons. Pressure is then applied to the still so that the boiling temperature of the hydrocarbons will be sufficiently high to effect cracking in the still, i. e., cracking in a single and gaseous phase will then come into operation and from. that time forward both stages will operate simultaneously but successively.

It is characteristic of this invention that the relative advantages of the pressure-distillation method of cracking and the vaporphase cracking are so combined as to bring about a continuous operation in which the material or materials to be cracked move progressively from the. one manner of cracking to the other. In the pressure distillation stage of this invention, very large volumes of material (as high as 1000 bbls. of oil) are subjected in a mass to cracking treatment for relatively long periods of time (i. e. from 20 to 50 hours) until the maximum yields from the entire body have been obtained, whereas in the vapor-phase cracking only very small quantities, as for example, gallons, are subjected to treatment at any one period of time and then only for a few seconds. Approximately the same capacities over a long period of time are attained in these two stages, but with diverse methods of treatment. In thepressure-distillation cracking stage, the material will become progressively heavier as the cracking proceeds, one method of operation hereinafter described, permits of the return to the still of the heavier parts for further cracking, until the operation is completed, when the residue is removed and another still connected. Where desired, the heavy parts of the first pressure-still cracking may be returned to a separate still. In the vapor-phase cracking the material to be cracked while in a vaporous state, is continuously maintained of uniform composition, since all the cracking possible in a single operation is accomplished by the single passage of such vapors from the retort under suitable cracking conditions.

In the accompanying drawings forming a part of: this specification, Fig. 1 is a view in elevation, illustrating a form of apparatus adapted for the practice of the invention described herein; Fig. 2 is a similar view, showing a plant embodying a plurality of cracking stills and retorts; Fig. 3 is an elevation showing a modification of the plant.

In the practice of the invention, the raw oil to be treated is charged into a still 1 of any desired type and adapted to be heated by any of the known or suitable means employed for that purpose. From the still extends a pipe 2 which may be made of such size and length as to effect a condensation of the higher boiling products formed in the still, but it is preferred that the pipe be connected to a fractional condenser 3 of any suitable type or construction adapted to effect a condensation of the heaviest products formed. The condensate from this condenser 3 passes into a tank 4. If in the condenser 3 only the heaviest products are condensed out, and discharged into a tank 4, the latter may be connected by a pipe 5 to a still 1, a preheater being preferably arranged in the pipe 5. But if the condenser 3 is so operated as to condense out all the hydrocarbons except those adapted to form the desired end product, i. e., one having a boiling point at or below 150 to 200 0, then the tank 4.- will be connected by a pipe 7 to a retort 8. In case the condenser 3 is so operated as to segregate only the heaviest products which it is undesirable to retreat in a single stage or-gaseous phase, the remaining vapors would pass to a second condenser 9 in which products adapted to gaseous phase retreatment are condensed out and discharged into a tank 10 which is connected to the pipe 7 The vapors discharged from the condenser 9 will flow into the condenser 11, where they are condensed. The liquids flowing through the pipe 7 may, if desired, be preheated and then forced into the retort 8 where they will be subjected to conditions of temperature and pressure and for a period of time suitable for the formation of the desired end product, as described and claimed in applications Serial Number 29020, filed May 18th, 1915, and 85603 filed March 24th, 1916. If desired,

the raw material may be first treated in the retort 12 in the manner above described and then that part of the product formed in the retort, having a boiling point above, say 275 C. and segregated from other prodnets in condensers 13 or other suitable means, may be charged into the still 14 and cracked under pressure, the vapors result ing from the distillation and cracking being condensed in the usual or any suitable manner.

I claim herein as my invention:

The process herein described for forming a low boiling hydrocarbon from a high boiling hydrocarbon which consists in cracking the high boiling hydrocarbon, segregating from the products of cracking the end product desired and then cracking the remaining hydrocarbons, one of the cracking operations consisting in subjecting the hydrocarbons in a relatively large liquid mass, to heat and pressure suitable for the production of the end product desired, segregating such end product, and the second operation consisting in vaporizing the material remaining after such segregation and subjecting such vapors to heat and pressure and for a period of time suitable for the formation of the desired end product.

In testimony whereof, I have hereunto set my hand.

WALTER F. RITTMAN.

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