US1711869A - Process for the continuous distillation of hydrocarbons with simultaneous cracking of high-boiling into low-boiling hydrocarbons - Google Patents

Description

H. WOLF PROCESS FOR THE CONTINUOUS DISTILLATJION OF HYDROCARBONS May 7, 192.

WITH SIMULTANEOUS CRACKING OF HIGH BOILING s N O m A% C9 0 1 R D Y4 H2 G Nt 3 MS d M W1 L 0 T N I Patented May 7, 1929;

[ UNITED STATES PATENT OFFICE,

' HEMEANN WOLF, or BADHOMBURG VOR DER norm, GERMANY, ASSIGNOB 'ro can i IBUROL AKTIENGESELLSCHAFT', or SCHAFFHAUSEN, SWITZERLAND, A CORPORA- TION or SWITZERLAND.

PROCESS FOR THE CONTINUOUS ICISTILLATION 0F H YDROCARIBONS' WITH SIMUL- TANEOUS CRACKING 0F HIGH-BOILING INTO LOW-BOILING HYDROCARBONS.

This invention relates to improvements in the process for the conversion of high boiling into loW boiling hydrocarbons.

In the various processes of cracking of hydrocarbons such as paraflines, olefines, naphthenes and cyclic hydrocarbons, such as naphthalene, 'xylols and the like and such mixtures of such hydrocarbons as are present in mineral oils and tar products, by heating under pressure to above the dissociation temperature whilst maintaining the cracked products as a mixture of liquid and gaseous phases it has been found'that after-reactions occur in the expanded mixture in consequence of which the optimum state is reversed Whilst the amount of low boiling products which it is desired to obtain, is diminished and carbonaceou's products separate out.

The present invention aims at overcoming this disadvantage by suddenly reducing the temperature of the mixture of liquid and gaseous products obtained in cracking processes immediately on leaving the 'heating zone, to below the critical temperature at which after-reactions occur before a separation of the liquid and gaseous phases is possible and whilst the mixture is simultaneously completely expanded by being admitted to a region of atmospheric-pressure are prevented and the optimum formation of the desired products effected in the heating chamber, is stabilized. p In carrying out the invention, the reductionin temperature of the cracked products is efiected by direct cooling by means of coldv or cooled hydrocarbons. By thus directly intermixing the cracked product with cold oils, the cracked products are moreover di-' luted and their reactivity is further diminished. Y I

By way of example, in carrying out the present process, a middle oil is cracked in a continuous process which results after cracking in a mixture of liquid and gaseous phases, for example by heating same in a coil system under pressure, or by passing same through a heated metal bath under pressure, under suitable conditions of temperature, pressure, time of passage, or by means of a catalytic cracking process permitting con Application filed Septeinberfi, I925, Serial No. 58,358, and in lirermanyNovember 3, 1924.

tinuous Working. Immediately aft-er issuing from the cracking apparatus and before a separation-of the liquid and gaseous phase is possible, the cracked product thus obtained is caused to expand freely below oilcontained in a vessel, if desired with the employment of a Korting circulating nozzle. In order to ensure better subdivision, the oil vessel may be filledwith Raschig rings or other suitable surfaces.

The amount ofthe cooling oil and its temperature is so selected in relation to the amount of the cracked product, that a sudden cooling is efi'ected to temperatures which exclude any after-reaction. Temperatures of about 250 to 300 C. are generally suifi-" cient for this purpose, and-the mixing temperatures may be lower or higher, according to the charging stock used, but not essentially above 300. Any hydrocarbon oil may be employed as cooling oil, e.g. any crude oil or crude oil residue which need not have a specially low temperature as the cooling effect can be adjusted according to the rate of flow of the oil. Any part of the cracked product absorbed by the crude oil or of the crude oil residue can be recovered by distillation'in a crude oil distillation plant linked together with the cracking plant, by which means a simultaneous distillation of the crude oil or crudeoil'residue is effected and their corresponding distillation products are also recovered, and may serve partly or Whollyas charging stock for the cracking process.

The advantage of this mode of operation is thatthe heat ofthe crackingprocess is utilized almost entirely or partially for the distillation process depending on the rate of cooling of the cracked products by the cooling oil. A further advantage of this mode of operation resides in the fact that the suppression of the after-reaction completely avoids any" formation of carbonaceous products or even coke. All such carbon-formers remain in the mixed oil and thus in the residue of the separate crude-oil distillation'process.

.In order more clearly to understand the invention, reference is made to the accompanying drawing which shows by wayof ex ample one embodiment of apparatus v suitable for carrying the process into practical effect. The oil to be cracked supplied to the pump P, from the tank A through the suction conduit 1 is delivered through theconduit 2 into the coil 3 in tank B. The oil delivered by the pump P is heated by the hot oil contained in the tank B which has a temperature of about 250 C. and cools thisoil by 50 and more. The thus pre-heated oil delivered by the pump P passes through pipe line 4 and enters the cracking furnace F passing for example through a cracking coil 5 of such dimensions as to effect thorough cracking. The cracked products issue fromthe furnace F through line 6 and pass the automatic safety valve 7 and are thus expanded to athnospheric pressure. The gases and vapours thereupon pass through the circulating nozzle ,8 at an extremely high speed, aspirate the cold'oil from the bottom of tank B for example through the apertures 9, and ascend through conduit 10 through the oil in tank B. Here they encounter the baffle 11 and are separated partly into liquid which returns to tank B and partly into gases and vapours which pass through the connecting pipe 12 into the dephlegmator C, where they are dephlegmated to the'desired fipal boiling point of benzine. The dephlegmated portion passes through siphon 18 into tank D, whereas the gases and vapours pass through pipe 13 into a condenser and tanks not shown. The oil of the tank B flows continuously through siphon 14 into a separate crude oil distillation plant (not shown) where it is re-distilled. The heat required for this purpose is small because the'oils already have a temperature of up to 250 C. when entering this plant. 7

In addition to the nozzle action at the apertures 9 a circulation is provided by the regula ting valve 15 so that cold oil can be brought directly in an abundant amount into the expanding spray.

For the purpose of preheating any crude oil for the crude oil distillation connected to siphon 14:, the regulating valve 16 is used, the valve 15 remaining closed. Cold oil runs directly from tank D through this Valve 16 l to the expanding spray. It is thus possible to maintain at the thermometer 23 any desired temperature of for example from 250 downwardly and thus to preheat to a certain degree, any'desired amount of the oil to be distilled. The-regulating valve 15 may be slightly opened depending on the amount of crude oil at disposal. In any case cold oil comes into the most intimate contact-with 'the expanding spray in such abundant amounts, that the cracking temperatures of for example 450 C. are instantaneously reduced to 250 C. by which means any afterreaction which would be'coupled with sep:

aration of carbon, ceases ordoes not occurat all. Moreover further after-reactions due to polymerization of unsaturated hydrocarbons are rendered impossible. The optimum conditions of about 450 0. present in the cracking coil-orany other cracking system are maintained by this sudden cooling even after expansion. Moreover the heat employed in-the'cracking process is utilized to a large extent in the separate crude-oil diseffected by oil or gas burners-24.

It may be mentioned that it is known to cool crackedproducts after their production under pressure or in an expanded state. In all these known cooling processes however either the cooling of the cracked products takes place only gradually in which case the success of the present invention, which lies in the suddenness of the cooling, cannot be attained, or in other known processes in which, for example, the heating is efl'ected in retorts or stills, the cooling is effected only in one phase (i. e.,.the vapour phase) .in which no stabilization is required. The essence of the present invention however lies in the expansion of mixture of phases consisting of liquid and gaseous phases in which the equilibrium attained in the cracking chamber on expansion would be adversely influenced by the separation of carbon and partial polymerization. of the low boiling hydrocarbon formed in the cracking chamber. Accord ing to the .present invention however this is completely obviated by causing the formed mixture of gaseous and liquid phases to ex pandrbelow a column of oil, by which means the equilibrium present in the cracking chamber remains constant even after the expan sion, due to the sudden cooling.

I claim 1. A process for the conversion of high boiling hydrocarbons into those of lower boiling point which comprises the steps of forcing said high boiling hydrocarbons under pressure through a tortuous path in indirect heat interchange proximit to a body of washing oil, conveying the higll boiling hydrocarbons from said indirect heat interchan e proximitywith said body of washingoil ishrough a further tortuous path and simultaneously said body of washing oil, thereby heating said washing oil and at the same time cooling said cracked hydrocarbons to a temperature below that at which after-reactions can take place, introducing said cracked hydrocarbons into said washing oil in such a manner as to aspirate fresh Washing oil into said body, de-

phlegn'iating and recovering the vapors and imity with said body of washing oil through a further tortuous path and simultaneously heating same to a temperature at which cracking of said high-boiling hydrocarbons takes place, thereupon reducing the pressure on the cracked hydrocarbons and thus imparting a high speed of flow thereto, introducing the expanded and rapidly flowing cracked hydrocarbons into the aforesaid body of washing oil, thereby heating said washing oil and at the same time cooling said cracked products to a temperature below that at which afterreactions can take place, effecting said intro duction of said cracked products into said washing oil in such a manner as to aspirate fresh washing oil into said body of washing oil, condensing the vapours evolved by said body of washing oil and returning the heavier condensate to said body.

3. An apparatus for the conversion of high boiling hydrocarbons into those of lower boiling point, comprising a tank, a preheating coil: immersed in a body of oil in said tank, a heated cracking coil in communication with said preheating coil, a line 'from said cracking coil leading to said body of oil, an expansion valve in said line, an injector device beyond said expansion valve, a communication between the suction side of said injector device and a source of supply for said body of oil, a baffled and apertured conduit at the delivery side of said injector device adapted to produce a circulation in said body of oil and to act as a vapour separator, overflow means for withdrawing a portion of said body of oil and means for condensing vapours evolved from the main body'of oil.

4:. An apparatus for theconversion of high boiling hydrocarbons into those of lower boiling point, comprising a tank, a preheating coil immersed in a body of oil in saidtank, a heated cracking coil in communication with said preheating coil, a line from said crack-.

ing'coil leading to said body of oil, an expan'sion valve in said'line, an injector device beyond said expansion valve, a communication between the suction side of said injector device and a source of supply for said body of oil, a cylinder leading from the delivery side of said injector device into said body of oil, said cylinder being apertured at the end adjacent said injector device and baflled at the end remote from said injector device and being adapted to produce a circulation in said.

body of oil and to act as a vapour separator,

' overflow means for withdrawing a portion of said body of oil and means for condensing vapours evolved from the main body of oil.

5. An apparatus for the conversion of high boiling hydrocarbons into those of lower boiling point, comprising a tank, a preheating coil immersed in a body of oil in said tank, a heated cracking coil in communication with said preheating coil, a line from said cracking coil leading to said body of oil, an expansion'valve in said line, an injector device beyond said expansion valve, a communication between the suction side of said injector device and a sourcetof supply for said body of oil, a bathed-and apertured conduit at the de livery side of said injector device adapted to produce a circulation in said body of oil and to act as a vapour separator, overflow means for Withdrawing a portion of said body of oil, means for condensing vapours evolved from the main body of oil and means for returning the heavier condensate into said main body of oil.

In testimony whereof I- have signed my name to this specification.

HERMANN WOLF.

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