US1402455A - Apparatus for refining hydrocarbons - Google Patents

Description

APPLlCfiTlON FILED NOV. 20, I916.

Patented Jan. 3, 1922,

1&02355.

2 SHEETS-SHEET I.

WITNESSES ATTORNEY W. O. SNELLING.

APPARATUS FOR REFINING HYDROCAHBONS.

APPLICATION FILED NOV;20, 1916-,

2 2. 92 1T 4 mm J dw m2 6 t a D1 a 3 I T l 1 v \f 3 x I 3 4 4 4 l v INVENTOR 4 ATTORNEY WITNESSES:

-zene, toluene, xylene and the like.

NETE rat are.

WALTER O. SNELLING,.OF LONG ISLAND CITY, NEW YORK.

AIPARATUS FOR REFINING HYDROCARBONS.

Specification of Letters Patent.

Patented J an. 3, 1922.

Application filed November 20, 1916. Serial No; 132,297.

To all @0710? it may concern Be it known that I, lVAL'rEn O. SNELLING,

a citizen of the United States, and a resident of Long Island City, in the county of Queens particularly, my invention is concerned with the cracking or thermal decomposition of hezwy hydrocarbons in the vaporous condition, and has for its obj ect to provide suitable apparatus for carrying into effect a process of vapor-phase hydrocarbon cracking which is described and claimed in my 'copending application for Letters Patent, Serial No. 132,296, filed concurrently with the present application on November 20,

1916. Several forms of apparatus will be hereinafter described, such apparatus being adapted to operate either continuously or intermittently, and being provided with means for widely varying the reaction conditions to which the hydrocarbons under treatment aresubjected.

The fact has long been recognized that heavy hydrocarbons, such asthose contained in natural petroleums, are decomposed or cracked into derivative hydrocarbons of lower molecular weight when subjected to considerable degrees of heat, and although the mechanism of the reactions involved is as yet but imperfectly understood, the crack-v ing of hydrocarbons has been practiced to a considerable extent upon acommercial scale. Hydrocarbons will decompose, or become cracked, either. in the liquid state, in the vapor state, or in a system containing both liquid and vaporous hydrocarbons, and the degree of the decomposition, as well as the resulting amount of lower-boiling products, will increase, in general, as the applied tem perature is increased, the quality of the .resulting products being controlled by the pressure under which the cracking takes place. It has heretofore been the usual practice to bring about the cracking reaction by More heating the hydrocarbons in a closed vessel containing both liquid and vapor directly in contact with each other. Under these circumstances, the pressure within the container mounts up rapidlyas the temperature is increased, and soon reaches a point that is dangerous to the apparatus. Two-phase. cracking processes have also the inherent de-- fect that the temperature and the pressure employed are dependent upon each other, so,

that thelhigh temperatures which are de; si'rable for certain cracking operations cannot be obtained without setting up unmanageable pressures.

I have discovered that if the hydrocarbons to be cracked are vaporized, and the vapors segregated and subjected to the requisite -heat and pressure whilesubstantially out of contact with the original liquid hydrocarbons, greatly improved products will result, particularly if the cracking is performed under the conditions which I have found to be most desirable and which will be described below. By thus treating the hydrocarbon vapor out of contact with the original body ,of liquid hydrocarbons, suitable cracking temperatures can be employed, without dealing with the pressures that would correspond to such temperatures. in atwo-phase system. The pressure upon the vapors may be controlled independently of the temperature and a sufficiently high pressure should always be employed to keep down the formation of unsaturated hydrocarbons. The general principle of vapor-phase cracking,

by the application of heat and pressure to hydrocarbon vapors in the absence of liquid hydrocarbons, is described and claimed in my c'opending application for Letters Patent Serial No. 7 68,618, filed May 19, 1913.

Several embodiments of my invention are shown in the accompanying drawings, in

which:

Fig. 1 is a diagrammatic side elevational View, with parts in section, of a vaporcracking system includin inclined cracking tube. Flg. 2 IS a dlagrammatic and partly sectional view of another 'form of apparatus, involving the use of a vertical tube heated by electrical means. Fig. 3 is a fragmentary view of a modified portion of the structure of Fig. 2. F1g. 4 is a diagrammatic vertical sectional View, slmia horizontal or lar to Fig. 2, but showing additional means for rendering the process continuous by the constant removal of the cracked products.

In all of the several forms of apparatus herein shown, hydrocarbon oil is delivered, drop by drop or in .a slow stream or spray, into a vaporizing chamber which is main tained at a suitable temperature above the boiling point of the oil but below the temperature at which substantial cracking occurs. The oil vapor pass freely from the vaporizing chamber into a highly heated cracking tube provided with a regulable outlet for maintaining suitable pressure in the tube, and means are provided for heating the cracking tube, for condensing the cracked vapors, and for collecting the gaseous and tarry products of the cracking reaction.

Referring now'to Fig. 1 of the drawings, an oil reservoir 1, which may be a strong steelbottle, is connected by means of a pipe 2 to a sight dropper 3 provided with a regulating valve 4. A pipe 5 leads from the sight dropper 3 to a T union'6 which is heated by means of a suitable burner 7 and is connectedto one end of a cracking tube 8 disposed'in a combustion furnace 9 where the tube is heatedby the usual battery of burners 10. The tube 8 may suitably be given a slight downward inclination toward its discharge end, which communicates with a liquid-cooled condenser coil 11 that discharges through a pipe 12 provided with a regulating valve 13 and extending into a c0llecting vessel 14 having a gas outlet 15. A pressure-equalizing by-pass' 16 connects the T union 6 to a pipe 17 communicating with the upper end of the oil reservoir 1 and with a gauge 18 which indicates the pressure in the system. Catalytic material may, if desired, be placed in the tube 8, such catalytic material consisting, for example, of iron turnings, alundum saturated with copper sulfate, or the like.

In the operation of this form of apparatus, the oil'to be treated is placed in the reservoir 1 and the cracking tube 8 is heated by means of the burners 10 to the required cracking temperature, which varies in accordance with the nature of the oil under treatment and with that of the desired product, and which may range from 300 C. to 500 C. or even higher, temperatures of 600 (J. to 800 0. being useful for certain 'purposes. For the production of the maximum quantity of gasolene-like liquid hydrocarbons from Pennsylvaniacrude petroleum, the tube 8 may be heated to dull red heat, about 47 5 C. to 500 C. The valx e 4 is then manipulated to deliver oil drop by drop through the sight dropper 3 and the pipe 5' to the T 6, where the drops are 'quickly vaporized.

he vapors enter the cracking tube and which the are there decomposed, under the combined influence of heat'and of the pressure devel- From the cracking tube, the cracked vapors and gases pass to the condenser 11, from which the condensed hydrocarbons and permanent gases are conducted throu h the pipe 12 to the receptacle 14. ertain amounts of permanent gases, hydrogen, methane, ethane, ethylene, etc., are always produced in the cracking operation. A portion of thesemixed gases remain in the cracking tube and the remainder is carried through the condenser with the cond'ensable vapors and withdrawn from the receptacle 14 through the pipe 15 and utilized to supply the gas burners 10 or in any other suitable manner.

The apparatus shown in Fig. 2 differs from the system of Fig. 1 in that the cracking tube is vertical, is heated by electrical means, and is provided with auxiliary means forsubdividing and vaporizing the heavy oil before it enters the cracking tube. The reservoir 1, pipe 2, sight dropper 3, valve 1, pipe 5, by-pass 16, pipe 17 and gauge 18 are constructed like the corresponding parts in Fig. 1 and perform like functions. In this form of apparatus, however, the tube 5 communicates with a vaporizing chamber 25 containing steel wool, fragments of metal or refractory material, or other small objects, which serve to subdivide and extend the drops of oil which fall through the pipe 5. The chamber 25 is ordinarily kept sufii-' ciently hot for rapid vaporization of the oil by heat from the cracking tube 26, with chamber 25 communicates through a short connector 27. If desired, the chamber 25' may be provided with additional heating means.

The upper end of the cracking tube 26 is heated to the required oil-cracking temperature by means of electric energy supplied,-

from any convenient source, through conductors 28 to electrodes 29, the ends of which are embedded in a mass of granular carbon or other conducting material 30 which surrounds the crackin tube 26 and is enclosed within heat-insulat1ngwalls'31 of firebrick or the like. The lower end of the tube 26 is provided with a screw cap 32, or other suitable removable closure, andis immersed in water or'other cooling fluid 33 contained in a vessel 34.

The apparatus just described is set in operationby closingthe circuit through the electrodes 29 and, when the upper part of the tube 26 becomes sufficiently hot, allowing drops of heavy oil to fall at a definite rate through the sight dropper 3, the rate of dropping being readily regulated by means of'the valve 4. As each drop of oil falls upon the hot fragmentary material cracking of previous portions of hydrocarbon vapors. The pressure in the cracking chamber is indicated upon the gauge 18 and may be regulated by means of a relief valve 35 if the pressure becomes too high. The condensable portions of the cracked hydrocarbons are collected in the cooled lower part of the tube, which may, of course, be

as long and as c'apacious as desired, and

which should preferably be of sufiiciently large diameter to. permit the condensable vapors to sink freely through the lighter permanent gases. When the desired quantity of heavy oil has been treated, the electric heating circuit is opened and the valve 4 is closed, and when the cracking tube is sufliciently cool, the condenser 34 is removed, 7

the valve 35'is opened and the liquid cracked products are drawn off by removing the cap 32. Such tarry matter and carbon particles as are developed in the cracking process col-' lect, for the most part, in the cap 32.

vAnother means for drawing ofli cracked products from the tube 26 is shown in Fig. 3, and consists of a needle valve 36 connected toj' a short pipe- 37 that extends through the'cap 32 into the tube 36. By opening this needle valve slightly from time to time,

the cracked liquid products may be readily withdrawn, together with such portions of the gases as need to be drawn off in order tobregulate the pressure in the cracking tu e.

The apparatus shown in Fig. 2 is well adapted for treating limited quantities of oil under diiferent heat and pressure conditions, for the purpose of investigating the behavior--of different oils in the vaporcracking process, and for determining the specific degrees of heat and pressure necessary to produce particular cracked products. When it is desired to operate continuously with the vertical-tube form of apparatus and to produce large quantities of a single end product, the principles of this apparatus may be utilized in the arrangement illustrated in Fig. 4.

Asshown in the latter figure, a vaporizing chamber 25, filled either wholly or in part with fragmentary material as in the apparatus of Fig.2, receives oil from thefeeding pipe 5 and communicates, through a reticulated plate 39, with the upper end of a vertical', unobstructed cracking tube 40 constructed to withstand the pressures generatedtherein. The tube ,40 is surrounded by a heat-insulating jacket 41,-of firebrick or the like, containing spaced annular pockets 42 disposed adjacent to the tube and filled with granular carbon or other suitable resistance material. Two electrodes 43 are inserted into each of the carbon-filled pockets 42 through openings in the jacket 41, and

are connected inparallel across line conductors 44 and 45 which are supplied with en ergy from any convenient source such as a generator 46, the circuit being regulated by means of a rheostat 47, The current through each pair of electrodes 43 is controlledby means of a switch 48 for regulating the heat applied to the several parts of the tube 41. a Any suitable means for heating the cracking tube 40 may of course be substituted for the electric heaters shown.

The bottom of the cracking tube 41 is in free gravity communication with a receptacle 50, from the upper part of which a pipe 51, provided with a valve 52, leadsto a con denser 53 that discharges into a gasoline receptacle 54 through .a pipe 55 provided with a valve 56. A pipe 57, having a control .valve 58, communicates with the upper part of the receptacle 54 for drawing off any excess of permanent gases that may accumulate therein. A pipe 59, provided with a valve 60, enters the upper end of the cracking tube 40 for relieving the pressure in the tube, when desired, by. drawing off some ofv the accumulated gases therefrom, or for introducing hydrogen or permanent hydrocarbon gases to supply any deficiency that may exist, particularly at the beginning of a run. A pressure gauge 61 may suitably be attached to the pipe-51 between the valve 52 and the condenser 53, since it is often desirable to maintain a controlled pressure in the condenser independent of the pressure in the cracking tube and in the remainder of the system.

In the operation of the system shown in Fig. 4, crude petroleum or other heavy oil is dropped at a regular rate, controlled by the valve 4, into the vaporizing chamber 25., is quickly vaporized, passes as'vapor into the cracking tube 40, and is there decomposed, all as described in connection with Fig. 2. The'cracked vapors, however, instead of being condensed in the cracking tube itself, pass into the receptacle 50, accompanied by the tarry matter and carbon whichmay be produced in the cracking operation. Such. solid and semi-solid matter I therefore restricted only by densing system is regulated C. to 700 C. or 7 50 is deposited in the receptacle 50 and the vapors pass through the pipe 51 and the condenser 53 to denser 53 may be replaced by a battery of condensers maintained at different temperatures if it is desired to directly fractionate the cracked hydrocarbons.

The pressure in the. cracking and convalve 56 or the valve 60, preferably the former if the pressure in the condenseris to be the same as that in the cracking tube. The pressure in the cracking tube may, if desired, be controlled independently of the pressure in the condenser by means of the valve 52. Whena condensing .system of large cooling area is employed, it is sometimes difiicult to maintain a sufiicientlyhigh pressure in the cracking tube, especially when working with an oil giving readily condensable products and low yield of permanent gases. Under such conditions, it is often advantageous to close the valve 52 until a sufficiently increased pressure is ob-' tained in the cracking tube.

The nature and amount of the products of my process'may be widely varied by changing the conditions of temperature, pressure and time under which the hydrocarbons are treated. In general, high pressures give larger and better yields of cracked products, and the pressures to be used are the practical limits of the apparatus employed. Variations in temperature produce corresponding variations in the nature of the products, the formation of low-boiling paraflin. hydrocarbons being promoted by relatively low temperatures of the order of 400 C. to 500 C., while cyclic hydrocarbons such as benzene and toluene, are produced at higher temperatures, ranging from 500 C. or 550 C. The proportions of any particular hydrocarbon may be controlled by varying the temperature within the ranges indicated above.

The forms of apparatus shown in Figs. 2 and 4:, particularly the system shown in the latterfigure, have the advantage that the free carbon which is necessarily produced to a greater or less degree in all oil-cracking operations, is not collected upon the walls of the cracking chamber, but, for the most part, falls freely to the bottom of the chamber and is collected either in the cap or in the tar trap 50. When the cracking tube is horizontal, or inclined but slightly, the

carbon often tends to form a hard cakeupon the tube wall, and if 'the tube. is kept in operatlon for a long time, the accumulated the receptacle 54. The conby means of the carbon may interfere to a considerable degree with the transfer of heat to the vapors' spects within the limits of my invention,

and it is therefore to be understood that my invention comprehends all such modifications and adaptations of this apparatus as fall within the scope of the appended claims.

I claim as my invention:

1. The combination with a liquid reservoir, of a .vertical, elongated, externally heated reaction chamber disposed beneath and in communication with the said liquid reservoir, a vaporizing chamber disposed between the said liquid reservoir and the said reaction chamber, means for establishing superatmospheric pressure in the said reaction chamber by equalizing the'pressures above and below the liquid in the said reservoir, and means for restraining the outflow of vapors and gases therefrom.

2. The combination with a liquid reservoir, of a vertical, elongated, externally heated reaction chamber disposed beneath the said liquid reservoir, a vaporizing chamber disposed at the top of the said reaction chamber, a valve and sight feed for controlling the flow of liquid from the said reservoir to thesaid vaporizing chamber, a pipe connecting the said vaporizing chamber with the top of the said reservoir, and. a pressure gauge communicating with the said pipe.

3. The combination with a liquid reservoir, of a vertical, elongated, externall heated reaction chamber disposed beneat and in communication with the said liquid reservoir, a vaporizing chamber disposed at the to of thesaid reaction chamber, a valve and sight feed for controlling the flow of liquid from the said reservoir to the said vaporizing chamber, subdivided refractory material disposed in the said vaporizing chamber, a pipe connected from the said vaporizing chamber to the top of the said.reservoir. a pressure gauge communicating with the said pipe, a receptacle disposed be neath the said reaction chamber, a valve for drawing ofi' liquid and solid products from the said receptacle, and a condenser communicating with the said receptacle, the said condenser being provided with valves at. its inlet and outlet ends.

In testimony whereof, I have hereunto subscribed my name this 17th day'of No-v

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