US1824947A - Apparatus for fractionation of certain hydrocarbons - Google Patents

Description

2 Sheets-Sheet Sept. 29, 1931. H. s. DAVIS ET AL APPARATUS FOR FRACTIONATION OF CERTAIN HYDROCARBONS Filed Aug. 5, 1926 Sept. 29, 1931. H. s. DAVIS ET AL 1,824,947

APPARATUS FOR FRACTIONATION OF CERTAIN HYDROCARBONS Filed Aug- 5. 1926 2 Sheets-sheet 2 m or pyrogenesis.

15, as Well as gen, methane, very reactive highl Patented Sept. 29, 10931 UNITED STATES PATENT oF-FICE HARCLD S. DAVIS, 0F BELMONT, AND WALLACE J'. MURRAY, 0F READING, MASSACHU- SETTS, ASSIGNORS, BY MESNE ASSIGNMENTS, TO PETROLEUM CHEMICAL CORPORA- TION, OF'NEW YORK, N. Y., A CORPORATION OF DELAWARE APPARATUS FOR FRACTIONATION 0F CERTAIN HYDROCARBONS Application filed August 5, 1926. Serial No. 127,282.

rThis invention relates to improved apparatus for the separation of hydrocarbon mixtures rich in olefines into fractions of predetermined characteristics and free from substantial admixture With each other.

rlhe mixture treated may be derived from petroleum, peat, coal, oil shales or other carboniferous natural materials by subjecting these to controlled heating for cracking The mixtures capable of being made by appropriately heating such substances generally contain ethylene, propylene, butylenes, amylenes, hexylenes an higher olefines of the general formula CnHgn, diolefines, ethane, methane and hydrogen, occasionally higher paraffines and naphthenes, and certain tarry reaction products of relatively high boiling point.

`This invention provides for the fractiona- 2@ tion of the eiiux from cracking treatment and is particularly adapted to the treatment of the mixture resulting from as complete generation of oleiine hydrocarbons as is practicable, and usually containing hydrocracked hydrocarbons such as the diole nes, isobutylene, trimethylethylene, unsymmetrica methyl-ethyl-ethylene; and other olenes such as propylene, butene-l, butene-2, pentene-1 and pentene-2; hexylenes, and homologous olefines of a higher number of carbon atoms. Fractions containing one or more of these substances are valuable for treatment for the production of alcohols and other derivatives or intermediates of derivative' substances; as Well as valuable in the form of group mixtures of certain boilingpoint ranges as motor-fuel; and valuable for other uses for which petroleum naphthas may be 4o employed. We refer to the process invented by Harold S. Davis and Wallace J. Murray described and claimed in their application Serial No. 10,992, filed February 24, 1925, which process contemplates the fractionation of such material as that upon Which this apparatus is adapted to operate, for more detailed description of andl claims to certain steps well adapted to be practiced by use of devices according to the present invention,

and for disclosure of further steps useful for d` fractions of hydrocarbons from Ithe hot vaporous eilux of a Cracking operation, for example from the vapor phase cracking of petroleum, for utilization in subsequent chemical treatments for the derivation of alcohols and related compounds.

A further object is to provide apparatus operating to fractionate the material treated and conserve the products of cracking by their segregation into groups according to their chemical reactivity, for example toward sulfuric acid. It is desirable, for example, to separate butylene from propylene to provide the most advantageous products for converl sion respectively into butyl and isopropyl alcohols, as explained fully in said application Serial No. 10,992.

It is a practical observation of operation in and by apparatus corresponding to this invention that the preparation of secondary alcohols with the aid of sulfuric acid absorption of olefines is advantageously to be practiced on olefines of the homologous series containing hexylenes in the substantial absence of any members of the series of a higher number of carbon atoms than the hexylenes, in order to avoid the risk of polymerization of the higher members of the series. On the other hand, the oletines of such higher orders are valuable constituents of motor-spirit products. The present apparatus is therefore ordinarily operated and designed especially to effect a closely cut separation into a gaseous fraction containing propyleno and ethylene, a fraction containing but-ylenes, amylenes and liexylenes, and a motorspirit fraction containing the higher olefines.

Another object is to provide apparatus adapted inthe treatment of materials of the class mentioned to effect a maximum separation of hydrocarbons boiling under 225o C. from the other fractions mentioned, for the purpose of providing material capable of relining treatment to produce a motor fuel having optimum anti-knock properties, while recovering for further treatment a clean hydrocarbon cycle stock free from heavy carbonaceous or tarry bodies, and comprising in part any unchanged portions of the original material fed to the cracking retorts.

The preferred operation of apparatus according to this invention produces as products of the operation (l) A gaseous fraction containing ethylene, propylene, methane and hydrogen, and substantially free from olefines more reactive and higher boiling than propylene; for example, butylene;

(2) A fraction comprising butylene, amylenes and hexylenes adapted to be maintained liquid under pressures not greatly exceeding atmospheric pressure at normal temperatures;

A crude naphtha fraction of which about 90% distills off at temperatures under 225o C., and suitable after refining treatment for use as a motorfuel; y

(4) A cycle stock fraction substantially boiling within the range of the original gas i oil or other feed stock treated in the cracking retorts supplying material for operation of this apparatus;

(5) A fuel oil containing the tarry reaction products of cracking, if any, and other hydrocarbons unsuitable for inclusion in the cycle stock fraction.

The invention will be described as embodied in apparatus comprising apreferred species only of apparatus according to the l genus of the invention. As shown in the acy C., and be received in a tarry liquid separator 1, (shown in plan) containing a baille 7b causing the vapors to bubble through accumulated liquid'held at a constant level, and therefore adapted to pass gases and vapors through pipe 2, and deliver solids if any, and residual material condensed or collected together by a liquid shower in separator 1, through pipe 3 to cooler 4, to storage tank 5, for fuel oil and tar. Tarry) liquids in the efflux 7 may be expected to e in foggy or globular distribution in the. gaseous stream, and preferably their separation is facilitatedY by showers from branch pipes 8 of pipe 9, from a pump 10 receiving a liquid condensate through pipe 11 from a liquid separator chamber l2 in series with a primary cooler 13 (which may be any preferred kind of aerial condenser) into which pipe 2 delivers. It will be understood that cooler 13 is not relied upon to condense all of the materials of the cycle stock or motor-spirit range of boiling points or lower boiling points, but functions as a dephlegmator.

The efHuX pipe 14 passes through a condenser 15, preferably water-cooled which in turn delivers to a gas-liquid separator 16, whence the liquid condensate is delivered by a pump 17 through a pipe lin-e 20, see Fig. 2, to a certain motor spirit fractionating tower l90 presently mentioned. The vaporous'eiilux from the separator 16 may pass through a meter M adapted to indicate the rate and amount of iow of the uncondensed gases and vapors at this point in the flow produced by the vapor phase cracking system delivering through the pipe 7.

The vaporous eiliux from the separator 16 is delivered through the pipe 18 to the intake side of a compressor 21, in turn delivering through pipe 22 to a Cooler 23 delivering into a gas-liquid separator 24 having a liquid educt pipe 25 to a pump 19 and a vapor and gas educt pipe 26 delivering into the bottom of an absorption tower 30. Material already in a liquid state in the separator 24 is forced un.

der pressure by pump 19 through pipe line 27, Figs. 1 and 2, which delivers the matters liquid by compression and condensation in the receiver 24 to a point in the upper part of a fractionating column, which may be of any usual bubble-plate type, for example as illustrated at 31, Fig. 2, and adapted to work at a relatively heavy gas pressure. Preferably pipe 27 delivers through a storage vessel 27a and pump 27 b, Fig. 2.

Thetower 30 is adapted and arranged to provide means for the selective absorption from the gases and vapors delivered through the pipe 26 of those constituents capable of being taken into solution in the cold in an absorbingr medium such as a neutral oil ofrelatively high boiling point, of which the socalled straw oil7 fraction of petroleum is one useful example. Tower 30 is therefore arranged to receive for countercurrent contact between the vapor delivered through the pipe 26 and a suitable absorption oil a continuous liow of absorption oil, delivered for example by the pump 37 receiving oil from the cool absorption oil storage tank 38, Fig. 1, through the pipe 36 against a gas pressure maintained by compressor 21.

The tower 30 may have any usual bubbleplates appropriate to liquid absorption of a countercurrent of vapor or gas. In the preferred construction, the maximum temperature of the absorption oil is arranged to be controlled, andthe preferred way of doing g this is to provide the tower 30 with a suitable series of refrigerating coils 40 placed in series with the educt pipe 41 and induct pipe 42 of a circulating system for a preferably gaseous refrigerating fluid, such as ammonia gas, being exhausted into a refrigerating unit 45, of any desired type, through the inductpipe 42.

The tower 30 is preferably equipped with a liquidactuated overflow control chamber 43 of any usual or preferred type suitably controlling a valve 44 in the pipe line 46 to a pump 47 delivering by pipe 48 through one side of a heat exchanger 49, and thence delivering to a heater, shown as a pipe still 50, of any usual or suitable construction, arranged to be heated by a gas blast 51 or otherwise, and delivering through a pipe line 52 to any suitable device for stripping the absorption oil of its absorbed gases and vapors; for example a stripper column or tower of the bubble-plate rectifier type as shown at 60.

The stripping tower 60 may be aided to operate at will by steam delivered through the intake 61, and may be provided with any usual type of overflow control means in a chamber 62 operating a valve 63 in an educt pipe 64 leading to4 a pump 65 delivering through pipe line 66 to one side of the heat exchanger 49, and thence through cooler 67 to the cold absorption oil storage tank 38. The tower 60 may be provided with any usual overhead condenser 70 having a trapped reflux leg 71 having therein a weir 72 for delivering liquid overflow through pipe 73 and through one side of a refrigerating heat exchanger 74 which may comprise two coils 7 4a and 74" in series having a separator 74S between them, for removal of condensed water, and thence through a gas-liquid separator 75 having a gas overflow pipe 76 leading to the intake side of the com ressor 21; and therefor@ adapted t0 provide for the refiux passage of gases, or vapors still in the gaseous state, in the separator 7 5 through compression at 21, cooling at 23, separation at 24 and absorption treatment in the tower 30.

Liquid efflux from the receiver 75 is forced by the pump 78 through the pipe 77 into the pipe line 27 above mentioned, leading the liquids by condensation from separator 75, and by compression from separator 24, to treatment in tower 31. The refrigerating heat-exchanger 74 is suitably cooled, for eX- ample by refrigerating gas effluent from the refrigerator unit 45 through the pipe line 79, and being exhausted into the refrigerator unit through the pipe line 80.

lt will be observed that so far as above described. a primary condensate of the effluxv from the tube 7, consisting of highboiling substances, has been taken out at the bottom of the separator chamber 12, and utilized as reflux liquid in the tar separator 1; and that a secondarycondensate (which may be refel-red to as av synthetic crude) appearing at the bottom of the chamber 16 has been forced boiling range characteristics of the through the line 20. This line 20 which may lead through a suitable storage vessel 20a and ump 20", delivers to an appropriate place in the height of a suitable fractionating tower of the bubble-plate type shown at 90, Fig. 2, from which a distillate of predetermined endpoint may be taken off through the pipe 91 and cooler 92. Induct pipesinto and educt pipes from fractionating tower 90 may have valved manifolds 90a, 90", 90c to provide for variation of the end-point of the distillate taken off. The liquid part of the flow from condenser 92 through sight box 93 is the fraction herein referred to as a motor spirit fraction becauseof the appropriate boiling range of its contents, anti-knock and other qualifications, due to its origin and mode of fractional collection, well adapting it to use after suitable refinement alone or in mixture with other hydrocarbon substances as a motor fuel. This fraction may be delivered through the pipe 94 into the crude motor spirit storage tank 95.

The residual product of operation at the bottom of the tower 90 is the cycle stock referred to above, which may be drawn off from the tower 90 by the appropriate operation of an overflow regulating means in exterior chamber 96 controlling the valve 97 in the pipe 49S leading through a cooler 99 to the cycle stock storage tank 100. The residue collected in the tank 100 is material of the gas oil typically used as a feed stock for the cracking operation, delivering at the educt ipe 7 above mentioned, and, if not utilized or its chemical peculiarities, the cycle stock in the tank 100 may be returned the pipe 101 to the feed end of the cracking retort. If desired, the cycle stock material may be redistilled for its contents of motor-spirit boiling range, if any, before return of the remainder to the cracking retorts.

The necessary heat input for the operation of tower 90 may be supplied by a pipe still 105 heated by the gas blast 106, or other heater, through which circulation from the bottom of the tower 90 is suitably secured, for example by the pump 107 operating in the educt pipe 108 and delivering through the pipe 109. The tower 90 is preferably equipped with an overhead condenser 110 having a trapped reflux leg 111 provided with a separator and weir 112 vented through the pipe line 115 fitted with a relief valve 115a and providing a refiux gas line to the compressor 21, for the purpose of maintaining a constant maximum pressure in tower 90 and returning through the compressor 21, cooler 23, receiver 24, and absorption tower 30 so much of the material as is in a gaseous or vaporous state at the Weir 112. r1`he liquid overflow at weir 112 passes through pipe line 141 and refrigerated cooler 142 to tank 140, presently mentioned.

Thev gaseous overflow from the top of the Liquids by compression` and condensation delivered through the pipe 27 to the tower 31 will also contain insolution a modicum of propylene, ethylene, etc. of the gaseous fraction to be collected in the tank/ 120. Therefore the pressure fractionating tower 31 is preferably arranged to include an overhead condenser 125 having a trapped reflux leg 126 provided with a gas separator 127 from which the gas overflow through the pipe line 128 is delivered through apressure relief Y valve 128 into the pipe 119 at 129.

Circulation for the operation of the tower 31 is preferably provided by a heater 130 provided with a closed steam coil 131 having valved inlets and outlets 132 and 133 respecltively. Circulation pipes 1311and 135 lead tothe heater 130 from the bottom and to an appropriate' point of the tower 31. Liquids collecting in the bottom of the tower 31 are drawn ofi' through an overflow regulator controlled valve 136 in the pipe 137 leading to the top of the motor-spirit fractionating tower 90, the point of entrance being contrrglled by manipulating valves of manifold 90 The condensate flowing past the separator and weir 112 and in the reflux leg 111 of the tower 90 (which, itwill be observed has selectively received the higher boiling fraction from the tower 31, which in turn received the liquids from theA receiver comprises a closely regulated fraction preferably containing all of the available amylenes and hexylenes; these contents, under proper conditions of temperature and pressure, also holding in solution substantially all the `butylenes passed through the units ofthe apparatus so far described, and which were taken into absorption by the refrigerated oil in the tower 30. The amylenes and hexylenes and the absorbed butylene may conveniently be 'delivered into the pressure tank 140. To avoid lost gases the temperature of the tank 140 islpreferably kept down by refrigerating the influx, or otherwise; for example the pipe 141 delivering into the tank 140 passes through the refrigerated cooler 142 connected between the outflow pipe 79 and inflow pipe l 80 for flow of the refrigerant from the refrigeration unit 45.

1t will be observed that the operation of the several units of apparatus is such as to take into absorption under pressure in tower 30 the products passing in a vaporous state the rough primary fractionation eected by the preceding condensation and compression, these products ranging to a minimum boiling pointl of -10 C.; thatthe the liquids from the primary condensation at 15, 16 and from primary compression at 21, 24 are severally fractionated at appropriate pressures in towers 'and 31; that the higher boiling through-pass from tower 31 `is also fractionated at tower 90; that the several gaseous overflows from absorption at tower 30., and fractionation under pressure at tower 31, are collectedtogether'in thepropylene, ethylene and other gas tank 120; and that the lowerboiling amylenes and heXylenes and butylene in solution, which were absorbed at tower 30, are received in a liquid state from tower 90 in pressure tank 140.

'lhe apparatus thus comprises meansfor the segregation under pressure of hydrocarbons corresponding substantially in boiling range to the butylenes, amylenes and heXylenes from other products ofdvapor phase cracking. These means further comprise devices for condensation of the'said hydrocarbons in two stages, severally of compression with cooling, and of absorption of condensibles from residual bodies remaining gaseous under the temperature and pressure of this stage; and means for 'fractionation under pressure to separate the said hydrocarbons respectively from higher-boiling liquids and retained gases having .liquef-action temperatures at the available pressure below a convenienttemperature,e..g. 10 C. Ancillary to these effects of the apparatus, the tower 31 is a device for topping liquids by condensation and compression under continued pressure, and the tower 90 is a device for separating light, intermediate and higher fractions by bottoIning out cycle stock and motor-spirit products. K

In addition to the operations of the apparatus which result in collection, as mentioned, of gases of boiling points below about 10 C. (in tank 120), of materials liquid at normal temperaturesunde slight pressureand having an end boilingpoint at about 100 C. (in tank 140), operations at tower 90 result in delivery into tank of crude motor-spirit having a boiling-point range of from about o C. to about 225 C.; and collection in tank 100 of a remainder boiling above 225.

Ve claim:

1. Apparatus for separating sharp boiling point fractions from roducts of cracking petroleum oil, comprising a fractional umn connected to said condensate outlet,

vmeans for takingktop, bottom and side cuts from said first rectifying column, a vapor outlet from said fractional condenser, an ablica ilo

sorber connected to said vapor outlet, an abi sorber outlet for unabsorbed hydrocarbon gases, a stripper operatively connected to strip absorbed hydrocarbons from absorption oil delivered by said absorber, a second rectifying column, a pipel delivering. said stripped hydrocarbons into said second rectifying column, and means for taking top and bottom cuts from said second rectifying column.

2. Apparatus for separating sharp boiling point fractions from products of cracking petroleuln oil, comprising a tar separator, a tar outlet therefrom, a vapor outlet therefrom, a fractional condenser connected to said vapor outlet, a condensate outlet from said fractional condenser, a first rectifying column connected to said condensate outlet, l

means for taking top, bottom and side cuts from said first rectifying column, a vapor outlet from said fractional condenser, an absorber connected to said vapor outlet, an absorber outlet for unabsorbed hydrocarbon a stripper operatively connected to strlp absorbed hydrocarbons from absorption oil delivered by said absorber, a second rectifying column a pipe connected to deliver said stripped hydrocarbons into said second rectifying column, and means for taking top HAROLD S. DAVIS. Signed by the said WALLACE J. MURRAY, at Fall River, Mass., this 2d day of August,

- WALLACE J. MURRAY.

and bottom cuts from said second rectifying Y column.

3. Apparatus for separating sharp boiling point fractions 'from products of cracking petroleum oil, comprising a fractional condenser, a condensate outlet from said fractional condenser, a first rectifying column connected to said condensate outlet, means for taking top, bottom and side cuts 'from said first rectifying column, a vapor outlet from said fractional condenser, al compressor connected to said vapor outlet, a separator in series With said compressor, a vapor outlet from said separator, an absorber connected to said vapor outlet, an absorber outlet for unabsorbed hydrocarbon gases, a stripper operatively connected to strip absorbed hydrocarbons from oil delivered by said absorber, a second rectifying column a pipe delivering said stripped hydrocarbons into said second rectifying column, and means forl taking top and bottom cuts from said second rectifying column.

4;. Apparatus for separating sharp boiling point fractions from products of cracking petroleum oil, comprising a tar separator, a tar outlet therefrom, a vaporf outlet therefrom, a fractional condenser connected to said vapor outlet, a condensate outlet from said fractional condenser, a rectifying co1- umn connected to said condensate outlet,

means for taking top, bottom and side cutsf.'1 v I from said first rectlfying column, a vaporl outlet from said fractional condenser, a com*- pressor connected to sa1d vapor outlet, a separator in series with said compressor, a va-A

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