US1822753A - Method for cracking oil - Google Patents

Description

C. L. SMITH METHOD FOR cRAcxING oIL Filed Jan. 25, 1929 Sept. 8, 1931.

Patented Sept. 8, 1931 UNITED STATES PATENT OFFICE CLYDE Il. SMITH, OF CHICAGO, ILLINOIS, ASSIGNOR TO GYRO PROCESS COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN METHOD FOR CRACKING OIL Application led January 25, 1929. Serial No. 335,062.

This invention relates to improvements in the art of cracking hydrocarbon oil, and has particular reference to cracking processes wherein the oil, while undergoing molecular decomposition, is in the vapor phase and maintained at temperatures in excess of 1000o F.

Itis a primary object of the present invention to provide a system for the cracking of hydrocarbons in the vapor phase so'formed andoperated as to admit of continuous iiow of the. oil undergoing treatment and Wherein provision is made for fractionating the charging stock prior to the introduction lof the latter into the converting zone or zones of the system, whereby each converting zone receives charging stock having relatively narrow boiling range limits.

-In accordance with the present invention a battery of two or more converting units may be utilized and ahead of these units fractionating apparatus is provided whereby each converter receives vaporized hydrocarbons having relatively close boiling ranges. Through the medium of this system optimum temperature conditions can be maintained in each converter to conform with the characteristics of the hydrocarbons under heat treatment therein, the arrangement providing for a maximum yield of a desired end product from a charging stock initially introduced into the system with but a minimum formation of fixed gas.

In vapor phase systems of oil conversion wherein the original charging stock possesses a relatively wide boiling range considerable difficulty isencountered when the hydrocarbons are subjected to the high vapor temperatures prevailing in the cracking zone in preventing over cracking of the lighter compounds and under cracking of the heavier or higher boiling point compounds. Over cracking of the hydrocarbons results often in excessive gas formation, while under cracking results in an inferior end product or in the 4formation of excessive quantities of recycle stock. Thus, if the oil under treatment in a. given converter has a fairly narrow boiling range the temperature conditions within the converter may be care- .fully controlled, together with other factors,

such as the velocity of vapor travel through the converter and the time of conversion, to procure very close and accurate -control of the heat treatment imparted to the oil vapors while traversing the converter, which results in a high rate of conversion with each through put of the charging stock as well as minimum gas formation.

For a further understanding of the invention reference is to be had to the accompanying drawings, wherein:

Figure 1 is a diagrammatic view disclosing my improved system of oi'l conversion; Figure 2 is a similar` view of a slightly modified form of the invention. a.

Referring morevparticularly to the drawings the numerals l, 2 and 3 indicate pipe stills or other suitable type of heaters. Each of these pipe stills is formed to include a setting provided with a transversely extending bridge wall which separates the setting into burner and tube compartments. The tube compartments are provided with banks 4 of oil circulating tubes. The temperature within the pipe stills is regulated so that while the oil is heated to an extent suiicient 'to effect the vaporization of a large percentage thereof, any substantial cracking of the oil is not permitted to-occur. For example, the temperature of the oil vapor leaving the outlet line 5 of the pipe still I may be approximately 600o F. The oil vapor flows from the pipe line 5 into an evaporator 6, which serves to eHect fractionation of the oil vapor. Thus all of the oils which do not vap'orize at a temperature of 600o F. condense as liquids in the bottom of the evaporator 6 orv from which they may be drawn off by way of a valve pipe line 7.

The vapors..` released from the top of the evaporator 6 flow by way of a pipe line 8 into 'the setting of a converter 9 and through a tube bank 10 arranged within said setting. The rate of flow of the vapors through the converterlO and the internal temperatures of said converter result in heating the oil vapors to cracking temperatures of approximately 11509 F. These cracked vapors are then discharged into a jet condenser 11 into which the charging stock obtained from the tank 12 is introduced, the charging stock being at approximately atmospheric temperatures or slightly higher. The charging stock comes into direct contact with the heated oil vapors leaving the converter 10, resulting in shock chilling said vapors to arrest or quench the conversion reactions in a substantially instantaneous manner. In this connection a sufficient quantity of the charging stock is introduced into the jet condenser to drop immeditely the temperatures of the oil vapors leaving the converter from 1150 to a temperature not in excess of 600 F. The oil which remains in vapor form after being so reduced yin temperature Hows by way of a pipe line 13 to a fractionating tower 14, and after passing upwardly through the fractionatingtower the vapors are led by way of a line 15 to a condenser 16 and thence to a storage tank or other treating apparatus 17. The liquids which accumulate in the bottom of the fractionating tower 14 where a substantially constant liquid level is maintained. Excess liquid which may accumulate in the 'bottom of the tower 14 may be by-passed through a line 19 to a storage tank 20, which may communicate with the tank 12 by means of a line 21. Also leading from the bottom of the fractionating tower is a pipe line 22 in which is located a pump 23, the latter being provided in order to force the charging stock through the coil bank 4 of the pipe still 1. This arrangement provides for continuous operation.

In order to treat the oil discharged in liq-' uid form'from the bottom of the evaporator 6, the pipe line 7 extends to a pump 24 which is employed to force the hot oil, derived from the bottom of the evaporator 6, through a tube bank 25 situated in the setting of the pipe still 2. The temperature of the pipe still 2 is regulated so that the oil discharged in vapor form from the outlet side of the tube bank 25 possesses, for illustration, a temperature of approximately 650 F. This vaporized body of oil is then led into a second evaporator 26 corresponding in construction, design and operation to the evaporator 6. The evaporator 26 serves to fractionate the oil vapors contained therein so that there may be collected within the bottom thereof the fractions which do not vaporize at a temperature of approximately 650 F. The vaporized fractions, however, passes overhead from the evaporator 26 and are led into the coil bank 27 of the converter tubes arranged within a second converter 28. In this converter the vapors are heated to a temperature of approximately 1130 F. and are discharged into a second jet condenser 29. This condenser receives its supply of charging stock from the tank 12, the said charging stock serving to elfect an instantaneous drop in the temperature of the vapors discharged from the converter 28 from, for example, 1130 to a temperature below or not in excess of 600 F. The vapors remaining in the condenser 29 pass by way of a line 30 into the fractionating tower 14, while the liquids which accumulate in the bottom of the jet condenser 29 flow by way of a pipe line 31 to the lower portion of the fractionating tower.

In the event the system embodies three' converters, it will be understood that any desired number of such converters may be employed in excess of two, the liquid oil deposited in the bott-om of the evaporator 26 is conducted by Way of a pipe line 32 and by means. of a pump 33 to a coil bank of tubes 34 located in the pipe still 3. Within this pipe still the temperature conditions are so regulated as to produce outlet temperatures of the oil vapors inthe neighborhood of-725 F., and the oil vapors of approximately this temperature are discharged into a third evaporator 35, which corresponds in function and construction to the evaporators 6 and 26, previously described. The oils which do not vaporize without molecular decomposition are collected as liquids in the bottom of the evaporator 35 and may be withdrawn therefrom by way of the outlet 36 usually in the form of fuel oil. The vapors of the evaporator 35, however, pass overhead by way of the line 37 and are conducted to a tube bank 38 arranged within the setting of a third converter 39... Temperature conditions are maintained within thesetting of this converter to heat the oil passing through the bank 38 to a temperature of roughly, 1110 F., and at this latter temperature the oilvapors are released to a third jet condenser 40. This condenser also receives its charging stock from the tank 12 and operates to instantly check conversion reactions, sharply reducing the temperature of the oil vapors released from the converter 39 to a non-reactive temperature not in excess of 600 F. The vapors remaining in the jet condenser 40 pass by way of the pipe line 41 to the fractionating tower 14, entering the latter at the same part as the vapor lin'es 13 and 30, While the liquids which accumulate in the bottom of the condenser 40 are forced by way of the pipe line 42 to the lower portion of the-fractionating tower and enter the latter at approximately the same part as do the lines 18 and 31. Itis within the province of the invention to employ separate fractionating towers for each of the converters althoughv in practice this has been found to be unnecessary since more economical results are obtainable with the use of but the single tower. It is also within the scope of the invention to utilize but a single jet condenser, but from a` standpoint of reducing or minimizing the liberation of free carbon it has been found this reason principally the separate units are utilized. Again, as shown in Figure 2 the separate pipe stills may be eliminated and the tube banks 4a, 25a and 34a situated within a single housing or setting. I therefore do not desire to be limited to the specific flow arrangement above set forth but reserve the right to employ all such modifications thereof which fall properly within the scope of the present invention.

It will be seen from the foregoing that each of the converters 10, 28 and 39 receive vapors having close boiling ranges and this enables the lfactors governing conversion, to Wit, temperature,`time and pressure, to be regulated to the best advantage within each converter. From a v practical operating standpoint this results in an increased rate of conversion and the oils passing through the converter, an increased yield as a final de.- sired end product from the entire quantity of charging stock introduced into the system, reduced fixed gas formation, minimized carbon liberation, better heat transfer and generally more economical and eflicient operation.

What is claimed is:

l. The continuous method of cracking oils in the vapor phase, which comprises passing a charging stock oil having a relatively wide boiling range in the'form of an elongated stream of restricted cross-section through a primary distillation zone, in heating the stream of charging stock during its continuous movement through said zone to temperatures suiiiciently high to vaporize the lighter constituents of said charging stock, continuously separatin the vaporized and unvaporized fractions t ereof, continuously assing without interruption the vaporize action through a primary conversion zone wherein said vaporized fraction is heated to conver.

sion temperatures in excess of 1000.J F., in passing directly the unvaporized fracstream of charging stock during its continuous movement through said zone to temperatures suiciently hi h'to vaporize the lighter constituents of saidg charging stock, continuously separating the vaporized and unvaporized fractions thereof, continuousl passing without interruption the vaporized7 raction through a primary conversion zone wherein said vaporized fraction is heated to conversion temperatures in excess of 1000 F., in passing directly the unvaporized fractions in an elongatedstream of restricted cross-section through a second distillation zone wherein said fractions are heated to temperatures higher than those prevailing in said primary distillation zone, subjecting the products discharged from said secondary zone of distillation to a second separating step to separate therefrom the vaporized from the unvaporized fractions thereof,- and in continuously passing the lighter vaporized fractions through a second converting zone wherein the vapors are heated to a converting temperature in excess of 1000 F. but less than said first named conversion temperature, dephlegmating the combined vapors from the primary and secondary converslon zones, and condenslng and collecting the blended distillate.

In testimony whereof I aflix my si nature.

CLYDE L. S ITH.

tions. in an elongated stream of restricted cross-section through a second distillation zone wherein said fractions are heated to temperatures higher than those prevailing in said primary distillation zone, subjecting the products discharged from said secondary zone of distillation to a second separating step to separate therefrom the vaporized from the unvaporized fractions thereof, and in continuously passing the lighter vaporized fractions through a second converting zone` wherein the vapors are heated to a converting temperature in excess of 1000 F. but less than said lirst named conversion temperature. s,

2. The continuous method of cracking oils -in the v apor phase, which comprises passing a charging stock oil having a relatively wide,

boiling range in the form of an'elongated stream of restricted cross-section through a prlmary dlstillatlon zone, in heating the

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