US1786947A - Method of cracking oils - Google Patents

Description

Dec. 30, 1930. R. c. HOLMES E1' AL METHOD OF CRACKING OILS- Original Filed June 26, 1919 5 Sheets-Sheet l @www /NVENTORS @MIM Dec. 30, 1930. R. c. HOLMES ETAL 1,786,947

METHOD OF CRACKING OILS Original Filed June 26, 1919 3 Sheets-Sheet 2 MM A TTD/NYE Y Dec. 30, 1930. R. c. HOLMES E'r AL 1,786,947

METHOD OF CRACKING OILS original med June 2e, 1919 s sheets-sheet s l? C /NVENTO/e s /gy 7j A TTR/VEY Patented Dec. 30, 1930 UNITED STATES PATENT OFFICE RALPH C. HOLMES, F NEW YORK, N. Y., AND FREDERICK T. MANLEY, OF HOUSTON, TEXAS, ASSIGNORS, BY MESNE ASSIGNMENTS, TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE METHOD OF CRACKING OILS Original application led June 26, 1919, Serial No. 306,936. Divided and this application led April 9, i 1926. Serial No. 100,790.

` Our invention relates tothe art of cracking 01 decomposing hydro-carbon oils for the purpose of converting heavier products, such as gas oil and fuel oil', into lighter products, 5 such as naphtha, gasoline and kerosene. More particular our invention pertains to processes of the above indicated character, in which the application of heat and pressure is employed.

This-application is a division of our copending application, Serial No. 306,936, filed June 26, 1919 which has matured into Patent 1,583,973.

We are aware that many processes have been proposed for the purpose of cracking hydro-carbon oils by means of heat and pressure, but it has been our aim to provide a process suitable for use on a commercial scale for the quantity production of gasoline or the like, by avoiding the objectionable features and difiiculties which are adherent in the arrangements hitherto proposed.

When sufficient heat is applied to a container or converter to effect decomposition of the petroleum oils therein, the walls of the container are very 4likely to be burned or,

weakened because the temperature is necessarily high, the vapor contained above the liquid level is a poor conductor of heat and carbon is deposited on the interior walls as a result of the decomposition of the hydro-carbon oils. This carbon deposit may be built up to a considerable thickness and is a poor conductor of heat, so that it greatly increases the likelihood of the metal walls being burned or overheated. Furthermore, the heat applied to the walls at the vapor space and at the surface of the liquid tends to overheat the oil and to break up the vapors into fixed gases.

Any overheating or burning of the walls is particularly undesirable and dangerous when considerable internal pressure exists in the converter. These diiiiculties have in fact materially curtailed the life of the apparatus of this character hitherto, and have limited the feasible pressures and temperatures which could be employed, making it impossible to utilize a relatively high pressure such as 150 to 200 pounds to the, square inchwhich we have found are productive of a higher yield of gasoline with the formation of less unsaturated hydro-carbons and fixed gases-in large capacity commercial apparatus.

Accordingly, it is one of the objects of our invention to largely obviate these difficulties 1. By applying heat to a converter intermediate its ends and below the level of the oil therein, so that heat is absorbed by the oil, and neither the oil or the converter are overheated.

2. By providing apparatus of relatively large capacity composed of aplurality of units preferably in the form of vertical stills,

free from tubes or objectionable' joints and so arranged that the heat is distributed over a large area intermediate their ends, instead of being concentrated at any one point.

3. By passing the oil at a cracking temperature through a series of converters or stills in succession and arranging for withdrawing residue oil from one or more of the stills near the end of the series where the cracking is most nearly complete and to which a lesser quantity of external heat is applied.

4. By utilizing effective means for scraping the carbon from the interior surface of each still.

5. By continuously introducing the fresh oil into the body of oil in the still to which the greatest quantity of heat is applied and where, in consequence of the introduction of the cooler charging oil, the rate of heat absorption may be increased with safety.

6. By supplying the highest temperature heat to the body of oil in the still where the oil is introduced and where the least cracking has beenI effected by reason of the time element essential to the cracking process and thus insuring that the largest carbon deposit occurs in the stills to which less external heat is applied.

Another object of the invention is to provide an apparatus especially adapted for continuous commercial operation on a large scale and so designed that the oil is passed successively through a series of converters that are severally maintained underv substantially uniform operating conditions and which operate concurrently upon the oil in transit therethrough to edect its conversion, the evolved vapors being taken off of the several converters as fast as they are formed and subsequently condensed and collected to constitute the ultimate product. y

To these ends, a plurality of converters, preferably of the vertical type, are disposed closely adjacent one another and are preferably arranged to be heated intermediate their ends by means of a single furnace, the structure of Which is such that the quantity of heat delivered to the respective converters may be regulated as desired. The several converters are connected above the heating zone by short and direct flow pipes, by means of which the oil which is charged into the bottom of the first converter of the series is caused to flow `successively through the remaining converters. Above the connecting iiovv pipes, the vapor spaces of the converters are in open communication through the agency of short and direct vapor line connections. The flowpipes serve to maintain approximately equal oil levels in the converters and the direct vapor line connections function to equalize and distribute the pressure developed in the several converters, which in practice has been found particularly' effective in assuring practically constant and equal oil levels. The evolved vapors are taken off, as they are formed, from one or more of the converters and are passed through a separator which condenses out the heavier constituents thereof Which are backtrapped to the bottom of the first converter of the series into Which the fresh charging oil is introduced. The lighter constituents of the evolved vapors are passed on through a condenser and are subsequently collected.

ln operation the furnace structure is so regulated that the several converters are maintained at substantially uniform cracking temperatures, and for this purpose a larger quantity of heat is applied to the first converter of the series in order to compensate for the cooling action of the charging oil and baclctrapped condensate. Although maintained at the same cracking temperature as the other converters, comparatively little conversion actually takes place in the first converter on account of the short time interval to Which the oil is subjected to cracking temperature-s therein. Consequently, very little carbon and heavy residue is produced in this converter. The bulkl of the conversion is effected in the remaining converters and the largest amount in the last of the series, in which, therefore, the greatest amount of carbon and heavy residue is deposited. It is from the last converter that the bulk of the carbon and residue is Withdrawn and for this purpose a residuedraW-oif pipe is connected to the bottom thereof Where the residue collects in an undisturbed state and may be removed with facility. The bottom of all of the converters are provided With residue draw-offs, which communicate With a common discharge pipe so that it is possible to remove residue from any or all of the converters if desired, although in operation it is usually preferable to Withdraw the residue from the last one or two converters of the series.

With the construction and operation thus briefly set forth, it will be understood that all of the converters operate concurrently and under substantially like operating conditions upon the oil in transit through them and that, therefore, the vapors evolved in the respective converters are substantially alike in characteristics, at least to the extent that they may be co-mingled and collected together to form the ultimate light product resulting from the process.

Other more specific objects of our inventionare to provide for controlling the distribution of heat among the several stills which make up the battery, so as to improve the regulation of the apparatus; to provide means for establishing and safely maintaining, Without leakage, an operative connection between a rotary mechanical scraper inside of each still and suitable driving apparatus outside thereof; and to provide for conserv- 1ng heat by arranging for a heat exchange between the residuum, drawn from the stills at the bottom and the fresh oil prior to the time it is charged into the battery.

Other objects and advantages of our invention and features by Which they are attained Will be set forth hereinafter and we will now describe the same with reference to the illustrative embodiment thereof shown in the drawings and point out the novel features thereof in the appended claims.

Referring to the drawings: Figure l is a partially diagrammatic elevation of apparatus arranged and constructed for practicing the process of our invention.

Figure 2 is a sectional elevation of a furdrawn to a larger scale than the semi-diagrammatic view of Figure 1.

Like parts are designated by the same reference characters in all the figures.

The apparatus illustrated, comprises in general a attery of stills designated respectively 1, 2, 3 and 4, a furnace 5, an air condenser or separator 6, a water condenser 7, a pressure regulator 8, a feed pump 9 and a heat exchanger 10.

The furnace 5, as clearly shown in Figures 2, 3 and 4, comprises a combustion chamber 11, having a bridge 12, a perforated inclined arch 13, and a secondary arch 14 providing openings into conduits 15; a heat defiecting wall 16, side walls 17, a horizontal base 18, raised a few feet above the floor or foundation, a top wall 19, and al plurality ofperforated partition walls, 20, 21 and 22, which together with the heat deiecting wall 16 provide a plurality of chambers 23, 24, 25 and 26 in which the stills 1, 2, 3 and 4 are respectively disposed.

Each of the stills is vertically arranged and its lengthis considerably greater than the vertical height of the chamber in which it is located so that it extends materially below the base wall 18 and considerably above the top wall 19. In this way the intermediate portion of each still is disposed within the furnace where it is'subjected to high temperatures and both the bottom and top extend outside the heating zone. Conduits 27 and 28 are formed along the sides of the furnace heating chamber aty the bottom, and are provided with adjustable dampers 29, 3Q, 31 and 32 which regulate the heat supplied to the still chambers from the conduits. Of

i course, separate furnaces for the respective stills may be used if desired.

We prefer to utilize stills of large capacity and as hereinafterexplained to keep them filled with oil toa predetermined level above the zone of direct heat application as indicated by gauges 70, so that the cracking process may be continued without interruption, and the overheating of the stills, and the production of fixed gases prevented.

The stills are directly interconnected in series-relation by short lengths of relatively large sized fiow line pipes 33, 34 and 35 and are preferably interconnected by similar vapor line connections 36, 37 and 38. The val por spaces of the several stills are thus in free and open communication and, therefore, any tendency to effect an unbalance or unequal pressure distribution among the several stills of the batteryduring their operation is immediately relieved and an equalization of pressure isl at once established. Thus, regardless of any'incipient Y pressure variations, substantiallyuniform and equalized pressure operating conditions are maintained throughout the battery, and inasmuch as they are also maintained at sub- -stantially uniform cracking temperatures,

all of the stills operate concurrently to produce or evolve substantially the same product. The iioW line pipes serve to conduct the oil from one still to another successively and also to assist in establishing uniform oil levels in the several stills, thereby contributing to the maintenance of similar operating conditions andv the production of substantially like products in the several stills.

As clearly shown in Figure 1 the stills are connected at the bottom through a residue manifold 39 to a tank 40 which forms a part of the exchanger 10, valves 41, 42, 43 and 44 being arranged to control the respective branches of the several stills.

The exchanger 10, in addition to the tank 40, comprisesl a coil v45 Which is disposed Within the tank 40 and forms a part of the draw-off pipe 49 provided with two branches v 50 and 51 vconnected respectively to the top and bottom of the tank 40 and having valves 52 and 53.

The separator 6 comprises, as illustrated, two sections 54 and 55, but may, of course, consist of one or more sect-ions as desired. Each section comprises a pair of spaced drums 56 connected by vertical tubes or pipes 57. The drum 56 at the bottom of the separator section 54 is connected by a vapor line 58 to the top of the still 4 and top drum of the 'same section 54 is connected to the bottom drum of the separator section 55 by a pipe 59.

There is a'back trap line 60 connected at one end to the bottom drums 56 of the air condenser and at the opposite end to a point near the bottom of the still 1. The top drum of the separator section 55 is connected by a vapor line 61 to a coil 62 of the condenser 7, the opposite end of the coil being connected by a pipe 63, having an outlet valve 64,*to the pressure regulator or receiver 8.

This pressure regulator has the form of a drum and is provided With a gauge 65 to indicate the liquid level therein. It has a condensate outlet 66 controlled by a valve 67 and a gas outlet 68 controlled by a valve 69.

In order to keep the sides of the walls of the stills free from carbon deposits, each still is provided with a positively operating scraper device comprising a rotatable shaft 71 extending vertically through the centre of the still and carrying a plurality of Scrapers Y the relativel pors around the shaft from the still in which high temperatures and pressures are maintained, oil cooled sleeves or pipes extend upwardly from the stills at the top and loosely surround the shafts, a stuffing box of suitable construction being located at each end of each sleeve, thus providing two series related barriers against leakage. The sleeves are connected in multiple relation to a drum 77 by means of pipes 78, and some suitable liquid, preferably a heavy lubricating oil, is circulated from the drum through the sleeves by means of a pump 76. The quantity of oil in the storage tank 77, is sufficiently eat to insure that relatively cool oil is supplied to the sleeves,v

By this means the stuffing boxes at the outer ends of the sleeves, are completely protected from destructively high temperatures and since pressure is maintained within the sleeves at least as high, and preferably slightly higher than the pressure in the stills, all possibility of leakage of vapor from the stills is avoided.

In the operation of the apparatus the stills are charged with oil to approximately the level of the How line pipes and heated until the vapor pressure due to distillation is built up to a predetermined degree which may be regulated by a vapor outlet valve 69 of the pressure regulator 8. The pressure which 'we now believe to be preferable is from 150 to 200 pounds per square inch but the process is operative with pressures which may be varied quite widely say, from 75 pounds upward. In any case, the pressure is substantially uniform, not only in the respective stills but throughout the system, including the separators and condenser coil 62 by reason of the open pipe connections between these parts and the stills.

Under the desired equalized pressure conditions the temperatures are increased so that the bodies of oil in the several stills are maintained at substantially uniform temperatures of sufficient intensity to crack or decompose a portion of the oils therein. The amount of heat supplied to the stills 2 and 3, is regulated by properly setting the dampers 29, 30, 31 and 32 and if the furnace is regulated to supply a suitable heat to these stills as well as to the last still 4. of the series, it is evident that heat will be supplied to still 1 in a greater quantity and at a considerably higher temperature by reason of its close proximity to the combustion chamber. However, since cool charging oil and backtrapped con ensate are introduced into this still the oil therein is maintained at substantially the same cracking temperature as that in the other stills, the excess of heat in quantity and temperature supplied to the first still serving to compensate for the cooling action of' the charging oil and backtrapped condensate.

By reason of the vaporization and distillation of the oil the liquid level would fall gradually and the carbon would increase in the stills if no fresh oil was supplied. Under these conditions the danger of overheating and destroying the stills and of overheating the oil, would be continually increased.

However, we maintain the oil level by continuously charging a suitable amount of fresh oil into the first still and consequently apply heat at all times to the stills below the liquid level of the oil therein.

The cracking process is not completely effected when the temperature of the oil reaches 4a sufficiently high degree, but the cracking temperature must be maintained for a material period of time in order that the oil may be largely converted. In other words, as soon as the proper temperature is reached cracking commences and continues for a considerable length of time before the body of oil is converted. In our apparatus the necessary time element is provided for, in the passing of the oil in succession through the series of stills which operate concurrently to convert the oil therein into low boiling products. While a certain amount of cracking takes place in the first still, the temperature of the oil being substantially uniform throughout all the stills, a greater proportion of the oil is converted in t-he succeeding stills, and,

consequently, the deposit of carbon is comparatively slight in the first still to which fresh oil is supplied and increases to considerable degree in the other stills and is greatest in the -last still.

Attention is particularly directed to the fact that according to our arrangement heat is applied at the highest temperature and in the greatest quantities to the first still where the slightest amount of carbon is deposited. This is a particularly important feature of our invention and enables us to utilize higher pressures relative to the size and capacity of the apparatus, than have been feasible hitherto.

The vapors continuously produced by the cracking of the oils in the several stills conveniently pass over through the flow lines 33, 34 and 35, or through the vapor lines 36, 37 and 38, or both, thence through the pipe 58 to the separators, the heavier products being Although we find it convenient and efor in fact that each of the stills be provided l ously or frequently withdrawing condensate from the regulating drum 8, and residual oils from the stills into the exchanger l0 as hereinafter explained.

In order to prevent the deposit of carbon which is continuously being produced as a byproduct of the cracking or decomposing of the oils in the stills, the residue which settles to the bottom of each still may be drawn off at suitable intervals through the residue manifold 39 to the drum 40.

As already explained, the accumulation vof residual oil in the first still is slight and very radual and it is not desirable to withdraw rom this still because it contains a large proportion of uncracked oil, and consequently we prefer to either continuously or at frequent intervals draw the heavy residue vfrom the last still of the series, or the last two or the last three stills, but not from the first one. A good separation of the residue may be effected as the oil in the lower portions of all but the first still is undisturbed by the' supply of charging oil. This residue is, of course, at a hightemperature and its heat is given up to the cold oil which is beingcharged through the pipe 45 and in this way the oils are warmed or preheated to a certain extent before they are charged.

However, it is evident that the oils which are back trapped through line 60 to the bottom of still 1 and the oils which are charged through the pipe 47 are at a temperature considerably below that required for cracking and consequently, in order to compensate for cooling action of these oils and to maintain the oil in still 1 at the cracking temperature, a very much greater quantity of heat must be supplied to this still than the others.

Another greatadvantage of our invention 'will thus be apparent and arises from the fact that the highest temperature heat is applied to the still where the greatest quantity is required andwhere, therefore, the rate of heat absorption mayA safely be increased.

` The pressure and temperature in the apparatus and the rate of supply and discharge are so regulated that only those vapors which are of desired volatility are allowed to pass out through the vapor line 61 into the water condenser, the heavier fractions being condensed in the separator and returned to the bottom of the still 1', so that they may be cracked or decomposed into lighter products. In this way the apparatus is particularly adapted for the continuous production in large quantities of a product of a desired gravity distillation or quality, such as gasoline or naphtha, or other light products.

An apparatus of a preferred form and construction has been illustrated and described` for the purpose of showing a way in which this invention may be used, but the inventive thought upon which this application is based, is broader than this illustrative embodiment thereof, and we therefore intend no limitations other than those imposed bythe appended claims.

What we claim is:

' l. A process of cracking oil that comprises charging the oil into a plurality of series- .connected vertical converters through which it passes in succession, heating the converters intermediate their ends to a cracking temperature and supplying most heat to the first converter of the series, Amaintaining the liquid level in the converters above the heated intermediate portions thereof, separating out the heavier constituents of the evolved vapors` by condensation, and returning the condensate to the first converter receiving the most heat.

2. A process of cracking oil that comprises charging oil into the bottom of the first of Aa plurality of series-connected vertical converters through which it passes in succession,

heating the converters .intermediate their ends to maintain a substantially uniform cracking temperature therein while imparting most heat to the first converter of the series, maintainingthe liquid level in the converters above the heated intermediate portion thereof, and withdrawing residual oil from the bottom of the last converter of the series.

l3. A process of cracking oil that comprises charging the oil into the first of a plurality of series-connected vertical converters through which the oil passes in succession, heating the converters intermediate. their ends to maintain the oil at a uniform cracking temperature, maintaining the liquid level in the converters above the heated intermediate portions thereof, separating out the heavier constituents of the evolved va 6 v I p 1,786,947

at .substantially uniform cracking temperatures.

5. A process of cracking oil that comprises charging the oil into the first of a plurality of series-connected converters and overflowing the oil from one converter to another to cause the oil to traverse the converters in succession, heating the converters below the liquid levels and above their bottoms to a cracking temperature by firing the series of converters at one end` and passing the hot products of combustion in contact with 'the series of converters from first to last, equal-` izingv the pressures within the several converters by freely interconnecting the vapor spaces thereof above the liquid level, withdrawing residual oil from the bottom of the last converter of the series, removing' the evolved vapors, as formed, from the converters, separating out the heavier constituents thereof and returning the hot condensate' to the lower portion of the first converter for repassage through the series.

6. A process of cracking-oil that comprises passing the oil in succession, through a plurality of series-connected converters, heating the. converters to a cracking temperature Y while im artin mos/t heat to the first conjfP g verter o the series receiving the charge, equalizing the pressures within the several convertersby directly interconnecting their vapor spaces above the oil levels, removing all of the vapors evolved inthe converters, separating out the heavier constituents thereof by condensation, and'returning the hot condensate directly to the first converter of the series for retreatment.

7. A process of cracking oil that comprises charging the oil into the irst of a plurality of series-connected vertical cylindrical converters, heating the converters below the liquid levels and above their bottoms to a cracking temperature, removing all of the vapors evolved in the series of converters from the last converter, condensing the heavier constituentsthereof and returning the condensate to the first converter.

8. A process of cracking oil that comprises passing the oil in succession, through a plurality of series-connected converters,

heating the converters to maintain the oil' therein at a uniform cracking temperature while impartin most heat to the first converter of the serles, removing the vapors from the converters, as formed, condensing the heavier constituents thereof, returning the condensate to the first-converter of the series and maintaining substantially uniform vapor pressures throughout the system.

9. A process of cracking oil that comprises passing the oil in succession, through a plurality of series-connected converters communicating one with another, at their liquid'levels, heating the converters-below the liquid levels and above their bottoms to a uniform 'cracking temperature while imparting most heat to the first converter of the series, equalizing the pressures in the converters by freely interconnecting their vapor spaces above the liquid levels, removing all of the evolved vapors from the several converters, separating out the heavier constituents thereof, returning the condensate to the lower portion of one of said converters for retreatment, separately condensing the lighter constituents of the evolved vapors, continuously charging the oil into the first converter of the series and removing residual oil from certain of the converters during the cracking operation.

10. A process of cracking oil that comprises charging the oil into the rst of a plurality of series-connected converters and passing the oil from one converter to another in succession, at the liquid levels, externally, heating the converters below the liquid levels to overflowing the oil from one converter to another at their liquid levels, heating the convertersy to a uniform cracking temperature by passing products of combustion in contact with said converters in succession from first to last, equalizing the pressures within the converters by freely interconnecting the vapor spaces thereof above the liquid levels, removing the evolved vapors from the converters, returning the heavier constituents thereof in the form of a condensate to the first converter of the series for retreatment and independently withdrawing residual oil from the lower ends of the respective converters.

12. A process of .cracking oil that comprises passing the oil in succession, through a plurality of series-connected converters, heating the converters intermediate their ends to a uniform cracking temperature, maintaining uniform liquid levels in the converters above the heatedportions thereof, removing the evolved vapors from the converters, as formed, condensing the heavier constituents thereof, returning the condensate to the first converter of the series for retreatment, removing residual oil from the unheated bottom of the last Aconverter and effecting a heat exchange with the charging oil entering the first converter of the series.

News? 13. A method of cracking oils under pressure, which comprises charging oils into one of a series of connected converters or stills and passing the oils through the stills' in succession, externally heating the' stills to severally maintain all of the stills at a Lilostantially uniform cracking temperature, and arranging to supply the most heat to the still being charged to compensate for the cooling action of the charging oil.

In Witness whereof l have hereunto set my hand this 3rd day of April, 1926.

RALPH C. HOLMES. In Witness whereof I have hereunto set my hand this 30th day of March, 1926. FREDERCKT. MANLEY.

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