US1916450A - Oil converter - Google Patents

Description

C. R. \NAGNER ET AL OIL CONVERTER July4, 1933.

Filed Jan. 25, 1930 Patented July 193s carr es stare Parser rrics CARY R. WAGNER AND ROIDOLPHE STAHL, 0F CHIC'AGO, ILLINOIS, ASSIGNORS TO GYRO PROCESS COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN OIL CONVERTER Application filed January 23, 1930.- Serial No. 422,904.

This invention relates to improvements in converters of the type employed in oil cracking processes and an outstandingobject of the invention resides in the provision of a converter wherein is provided a plurality of peculiarly arranged tubes through which the oil to be heated and cracked is passed in a vaporous state, and wherein the arrangement of the tubes in the converter is such as to provide for the eiiicient heating of the oil vapor to cracking temperatures and the main tenance of the vapors at such temperatures for desired periods of time for the purpose of securing from the oil vapor passed through the converter a maximum yield of a desired end product and minimum quantities of fixed gas and recycle stock.

It is another object of the invention to provide a converter having a novel arrangement of tubes for the passage of the oil vapors for affording a uniform heating of the oil vapor passing through the several tubes of the apparatus, so that localized overheating or underheating of the oil vapor is minimized and the oil vapors maintained under desired uniform conditionsof time and temperature in the heat supplying zones of the converter.

It is another object of the invention to provide a converter wherein the oil vapor is brought rapidly to a desired cracking temperature when first introduced into the converter and wherein provision is made for maintaining high vapor velocities during the passage of the oil vapors through heat absorbing tubes wherein a high rate of heat input is obtained.

It is another object of the invention to provide the converter with an, enlarged time chamber or tube through which the oil vapor is passed after having reached a cracking temperature and wherein the design of the time chamber is such as to permit of lower vapor velocities therethrough together with a uniform heating of the oil vapors to attain the desired rates or percentages of cracking.

F or a further understanding of the invention reference is to be had to the following description and theaccompanying drawing, wherein:

Figure 1 is a vertical sectional View taken through a converter designed in accordance withlthe present invention, 7

Figure 2 is a horizontal sectional View on the line 22 of Figure 1, and

Figure 3 is a transverse sectional View on the line 83 of Figure 1.

Referring more particularly to the drawing, the numeral 1 designates the improved converter comprising the present invention. This-converter comprises a setting consisting of the usual furnace walls constructed to minimize heat loss and to permit of the efficient utilization of the heat developed within the converter. The interior of the converter is provided with a transversely extending bridge wall 2, which divides the converter into combustion and tube chambers 3 and 4 respectively. The bridge wall 2 terminates below the roof of the setting which is preferably arched, so that the chambers 8 and 4 will be in communication over the top of said bridge wall. The combustion chamber is provided with a plurality of burners 5 which operate to produce furnace gases of requisite temperatures for carrying on the cracking operations for which the converter is designed. a v

The oils to be cracked or otherwise heattreated by the converter are delivered to the latter in a vaporized form. This is preferably accomplished by first passing the oils through a preliminary heater (notshown) wherein the oils are vaporized and from this preliminary heater or vaporizer the oils pass to the converter by way of the inlet pipe .6. This pipe communicates, as shown in Figure 2, with the horizontally placed header 7 usually arranged exterio'rly of the setting. Connected with the header 7 and extending horizontally through the upper portion of the tube chamber 4 isa row of tubes 8 which con stitute what may be termed the first pass of converter tubes. The tubes 8 are of relatively small cross-sectional area and are supported in their horizontal position and, in relatively spaced order by the end or vertical wall of the chamber l. It will be observed that these tubes are located in the upper portion of the chamber 4 in order to be located in the zone of greatest temperaturewithin the converter and due to their position these tubes are subjected to the intense heat radiated from the arched roof of the setting, as well as the convected heat energy obtained from the gases of combustion passing through the converter.

The oil vapors enter the tubes 8 at approximately a temperature varying between 650 to 750 F., and due to the small cross-sectional area of the tubes 8, for example, three inches outside diameter, the vapors pass at high velocities varying from 1500 to 3000 feet per minute. Therefore, by reason of the location of the tubes 8 in the converter, the velocity of vapor flow through the tubes and the relatively large amount of heated surface provided by said tubes in proportion to the total quantity of oil vapor passin there through, said vapors upon entering the tubes 8 are substantially instantaneously raised to an active cracking temperature usually in excess of 1000 F. At least, the vapors attain this temperature before their discharge from the outlet ends of the tubes 8. By providing the enlarged inlet header 7 each of the tubes 8 receives a substantially equal quantity of oil vapor so that a uniform heating of the oil in the tubes 8 is obtained. It is important, however, that the oil vapors should be practically free of liquid constituents when introduced into the tube 8, and this condition can be obtained by any suitable preheating of the oil vapors prior to their delivery to the tubes 8.

The cracking of oils involves two important factors, namely, time and temperature. The desired cracking temperature is obtained in the first pass of tubes 8 and the time factor is obtained by the apparatus now to be'described. Connected with the discharge ends of the tubes 8 on the opposite side of the converter as regards the header 7 is a second header 9 into which the vapors passing through the tubes are all dischar ed. The header 9 includes a downwardly disposed connection 10 with which is connected the vapor entrance end of one or more enlarged tubes 11. In this instance but one of the tubes 11 has been disclosed, but it will be understood that one or more of such tubes may be employed, this number, of course, depending upon the number of tubes in the first pass 8 and the capacity of the converter. The time chamher or tube 11 may consist of an elongated tube possessing an outside diameter of approximately 10 inches. The area of this tube is such that the vapor velocity therethrough will be at least no higher than those which obtain in the tubes 8, irrespective of the increase in the volume of oil vapors by rise in temperature and to decreased back pressure. Usually, the vapor velocities in the tube 11 are appreciably lower than those which obtain in the tubes 8. It will be observed that the tube 11 is located in a zone of lower temperature in the converter 1 than the tubes 8 and is heated by the furnace gases after considerable heat has been absorbed from the latter by the oil vapor flowing through the first pass of tubes. At this point it may be well to call attention to the fact that the tubes 8 are protected from dangerous overheating by reason of the fact that heat is rapidly removed from the walls of the tubes 8 by the rapid flowing oil vapors which travel therethrough, so that the latter tubes possess a long life even though located in the high temperature zone of the converter.

The tube 11 may be of any desired length and it is not only positioned in the lower portion of the tube chamber 4, but extends longitudinally through a laterally extending stack outlet 12 by which the furnace gases are led from the converter 1 to the oil vaporizer or preheater and thence to the atmosphere. Therefore the length of the tube 11 as well as its increased cross-sectional area provides for the maintenance of the oil vapors within the tube 11 for the desired period of time necessary to secure an efficient rate of cracking. The converter temperatures surrounding the tube 11 are sufficient to continually supply heat to the oil vapors traveling therethrough in order to keep said oil vapors at a temperature preferably above 1000 F. and to overcome loss of temperature by reason of the endothermic nature of the cracking reaction. The tube 11 therefore cannot be considered merely as a so-called soaking chamber of the type frequently found in liquid phase cracking apparatus, since in such soaking chambers no eifortis made to supply the oil with extraneously applied heat, whereas the tube 11 is located directly in a highly heated furnace zone and receives heat from the burners 5.

Another advantage in employing the single time chamber or tube 11 resides in the fact that the oil vapors traveling therethrough are uniformly heated so that under or over cracking of the oil vapor is precluded and a desired uniform cracking temperature obtained. VVhere the oil vapors travel through a plurality of tubes arranged in multiple such iio as in the first pass of tubes 8, obstructing carbon deposits or imperfections in the matter of distributing the heat of the furnace uniformly around all of the tubes, is likely to result in an uneven heating of the oil vapors to cracking temperatures. If this condition persists throughout the entire travel of the vapors through the heater the desired average cracking temperature of at least a portion of the vapors cannot be secured. The

result is that if the vapors are overheated above the desired cracking temperature, ex-

c'essive quantities of gas or incondensables are produced which lower the rate of conversion or the percentage of recovery of the desired end product with each throughput of the vapors through the converter. Conversely, if the oil vapors are underheated substantiallythesame general results obtain,

since larger quantities of recycle stock'are' from into a singletime tube such unevenheat-- ing of the oil vapor is positively prevented intended to cover such an arrangement The and desired optimum cracking temperatures secured. The vapors released from the time tube 11 pass into a conversion arrester 13, which consists of an enlarged vessel into which cold oil is sprayed by the operation of the nozzle 14. This cold oil which constitutes the charging stock, is thus brought in a finely divided state into contact with the highly heated cracked vapor, with the result that through the heat interchange provided, the temperature of said vapors is sharply reduced from an active converting temperature in excess of 1000 F. to a non-converting temperature not in excess of 600 F. This operation results in minimizing the deposition of free carbon in the system following conversion. The oils remaining in vaporous form pass from the arrester by way of the outlet line 15 and are led to suitable fractionating apparatus (not shown) to secure the separation of the desired end products. The liquid remainingin the arrester is withdrawn by way of an outlet line 16 and may be used as recycle stock. a r

In view of the foregoing it will be seen that the oil vapors are heated in the first row of tubes quickly and substantially instantaneously to a conversion temperature and at the same time the tubes are protected by the rapid flow of the oil vapor in order that the vapors may absorb and readily remove the heat from the walls of the tubes, keeping the latter at a proper operating temperature to minimize the danger of overheating. In low pressure systems the tubes 8 are arranged for parallel oil flow by the multiple order of the tubes. If higher pressures are used, for example, pressures in excess of 50 pounds per square inch, the oil vapors may traverse the tubes 8 serially, and the present invention is merged vapors discharged from the tubes 8 then travel at a desired velocity through the elongated time tube 11' wherein thetemperature of the vapors is maintained substantially constant without appreciable fluctuation. By thus controlling the time element and by being able to keep the oil vapor temperatures uniform the converter will produce a maximum'yield of hydrocarbons having the boiling range of gasoline. Dry vapors preferably are introduced into the tubes 8 to minimize coke, deposit in these elements of re stricted cross-section. The arrester 13 is also important in the cooling of the vapors for the purpose of abruptly terminating the conversion reactions, it having been discovered that by sharply dropping the temperature of the vapors from a cracking temperature in excess of 1000 F. to a fractionating temperature below 600 F. little or no free carbon ac-' cumuiates in the converter or the apparatus immediately following the same. By bringing the'cold make-up stock into contact with the heated vapors this object is obtained in avery effective manner and at the same time 1n an economical one, slnce the make-up or charglng stock is thereby preheated, vapor ized and partially cracked without involving extraneous or additional heating.

While the invention has been described in detail, it will be understood that variations may be made therein from the specific disclosure herein set forth without departing from the spirit of the following claims.

WVhat is claimed is:

1. In a converter for cracking hydrocarbon oils in the vapor phase, a heat confining wall structure, a bridge wall arranged within said wall structure and dividing the latter into spaced burner and heating chambers, the said chambers being in relative communication over the top of said bridge wall, burner means arranged within said burner chamber for generating high temperature combustion gases, a duct communicating with the lower end of said heating chamber and extending laterally therefrom, a row of substantially horizontally arranged tubes, each tube possessing a restricted cross sectional area, arranged in the upper portion of said heating chamber on one side of said bridge wall, means for passingvaporized oils through each 'allel order to effect the heating of said vaporized oils to converting temperatures, a single header arranged to receive the highly heated vaporized oils discharged from said tubes, and a single elongated tube of greater cross sectional area than any one of said first named tubes arranged in the lower portion of said heating chamber and extending through said duct and subject to the heat of the combustion gases following the passage of the latter substantially downwardly over said first-named tubes, said furnace gases after passing from the lower portion of said heating chamber be,- ing delivered to said duct for longitudinal travel therethrough in prolonged contact with the tube of greatercross sectional area.

2. In a converter for cracking hydrocarbon oils in the vapor phase, a heat-confining wall structure provided with a chamber, means for generating and supplying said chamber with highly heated furnace gases, a bank of tubes each of relatively restricted cross-sectional high velocity through said tubes, whereby said vapors are rapidly heated to desired conversion temperatures, an outlet header into which the highly heated multi le streams of.v

vapor are delivered following t ieir discharge from said tubes, :1 single elongated tube arranged in the lower temperature region of said chamber and subject to the remaining heat of said furnace gases following the pas-- sage of the latter over said first named tubes, and a duct communicatingwith andextending laterally from said chamber and in which the tures.

- GARY R. WAGNER. RODOLPHE STAHL.

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