US1948890A - Process for treating hydrocarbon vapors - Google Patents

Description

Feb. 27, 1934. w. F. slMs Er AL PROCESS FOR TREATING. HYDROCARBON VAPORS Filed Feb. 1e, 1928 :s sheets-sheet 1 amando/0S 75m/ll.

Feb. 27, 1934. w. F. slMs Er A1. 1,948,890

PROCESS FOR TREATING HYDROCARBON VAPORS FiledvFeb. 1e, 1928 s sheets-sheet 2 Feb..27, 1934. w. F. SIMS Q -m'. A r1,943,890

PROCESS FOR TREATING HYDROCARBON VAPORS Filed Feb. 1e. 1928 s sheets-sheet 3 ucts.'vapors from shale oil products, etc., with.

nanas ses. 2 7, i934 ATENT OFFICE PROCESS FOR TREATING HYDROCBBON VAPORS Willis F. Sims and Venus U. Cloer, Wichita Falls.

Tex., assignors to Panhandle Reilning Company, Wichita Falls, Texas Tex., a corporation o! Application February is, 192s. serial 110.254.753

6 Claims.

0ur invention relates to the treatment of. hydrocarbon oils, and more especially to such treatment for the purpose of reducing higher boiling compounds to lower boiling compounds, commonly called cracking. The invention has for its object the production of a'n improved process of cracking, and we attain this object by treating hydrocarbon vapors, which may be vapors from petroleum products, vapors from coal tar prodheat and under subatmospheric pressure in such a manner that the higher boiling constituents are broken down to lower boilingv compounds similar to gasoline or related light oils, and recovering the gasoline-like material and related light oils so produced.

Very briey stated, according to this invention, the oil to be treated is i'lrst heated under pressure (which may vary from to 60 lbs. or even higher according to the character and grade of the oil being treated), until suiiicient thermal energy is accumulated for vaporization of heavy fractions, is then released into a ashpot positively maintained under subatmospheric pressure wherein it nashes into vapors, is then passed through an open connection to a cracking still, which may be a pipe still of approved construction, which is also under subatmospheric pressure, preferably lower than that maintained on the ilashpot, is then passed through fractionl ators or dephlegmators to a vapor outlet from which it goes to a cooler or condenser and separator. Two features are oi. importance, viz., the maintenance ot subatmospheric pressure on the forwardly proceeding vapors in the ashing zone and in the cracking zone, whatever the form of apparatus may be, and the subsequent handling of the cracked vapors in `such manner as to permit reiiux distillate and make-up oil to be pumped'back to the iiashing zone through heat exchangers adapted to absorb heat from the cracked vapors. We shall describe herein power actuated pumping means for positively maintaining the vacuum `onsubatmospheric pressure on the cracking still and the ashpot. Our invention includes the positive maintenance of this low pressure through these two' stages or pieces oi apparatus in every case, and according to the character oi the oils being treated, upon other portions of the system. The suction or vacuum pumping means doing this work is piped so that it may be connected at will either with the vapor outlet of the separator or at a point between that and the cracking still. We shall claim thisvariable method of connection herein, and we shall also claim the broad idea of positively maintaining 'subatmospheric pressure on the cracking still and on the flashpot, and the specific ideas of including the vacuum pump therefor -directly between the cracking still or zone and the first Iractionator. as well as on the output of the separator.

For a full understanding of our process, ref- `erence should be had to the accompanying drawings, in which Fig. 1 is a diagrammatic representation, with parts in section, of the principal pieces of apparatus required to practice our invention.

Fig. 2 is a ow sheet showing the several steps in the course of the oil when the vacuum pump is hooked up on the cracking still and ilashpot only, with its output going to the first fractionator.

Fig. 3 is a similar ilow sheet showing the flow when vacuum is maintained on the entire plant through the terminal separating and rec g drum.

Referring to the drawings, and rst t Fig. ,1, the principal pieces of apparatus employed in the operation of our process are the preheater 57, the flashpot 1, the cracking still 56, the dephlegmators or fractionators 6-7-8, and the suction pump 14 connected between the pipes -40 and the pipes 39-42 whereby the pump may be connected either between the cracking still 56 and the rst dephlegm'ator 6 or between the separator or receiving drum 10 and the absorption tower 11, which will be presently referred to. The pies 30--40 and 39--42 are provided with valves 3, 5, 46, 19, 20, 21 and 25. Eachfof the dephlegrnating towers 6 7-8 contains in its top a heat exchanger 26, 27 or 28, whose superficial area and capacity isl increased in the direction oi iiow by increasing .the number of coils. It is to be observed that not only does the temperature become higher in the towers 8, 'i and 6 in that order, but the temperature and the boiling point oi the vapors in each succeeding fractionator 6, 'Z and 8 in that order become lower. The input ci the iirst of these heat exchangers 2S is connected through the valved pipe 32 to the output ci the pump i5, vwith valved branch 31 to the top ci the absorbing tower il, the flow from which is regulated by valve 35. From the output end of the heat exchanger 2t, the pipe 22 extends to the ashpot l direct, without going tothe preheater 57. Charging stock is ied'into the preheater under pressure by the pump 54 and. in order to build up pressure and accwnulate the ts in the coil 5'?, the valve titl) 23 is provided which in operation is complementary to the valves 35 and 38., Means are provided to regulate the heating of the reiiux fractions and the maire-up oil in the heat exchangers 27--28. rihese are shown in the drawings asbypasses controlled by valve 13S-37, which like the other valves described can be set at any thing from closed to open.

The function of the pump l2 is to draw od the heavy precipitate or tarry matters from the bottom. or tower 6; the iunction of pump i3 is to draw oif heavy gas oil which is thrown down in the bottom of tower 7, and return the same in part through valve 1S to the middle section of tower 6 and in part through valve Li7 to the heat exchanger 26 as reflux to be retreated. The runotion of pump la is to produce suction either directly through the valve ti on the output or the cracking stili 56, (and conversely to build up ahead of it through pipe 30 and valve 5 a con stant positive pressure, that is to say a pressure at or above atmospheric in the towers 67)'; o r through the valve 2i on the output 3G oi the sep arator or receiving drinn l0 and so through the entire system opy the output of the cracking still 56. The function of the pump 15 is to withdraw light gas oil from the bottom of tower ii, drawing it through the heat exchanger 17 and discharging it either in whole or in part through the valved branch 3i into the upper part of absorption tower ll., or in whole or in part through the valved branch 32, into the heat exchangers 28--27--26, according to the settings of the valves 3l and 32.y The portion discharged through the valve' into the tower l1 has for its function the absorption of gasoline-like fractions which have become entrained with the 'fixed gases. The entrained gasolinelile material is stripped from these gases and absorbed by the oil entering the head of the tower through the valve 31. This tower as well as the towers 7 8 is a bubble tower, but it is'to be understood that any preferred apparatus may be employed which will afford a large superficial area over which gases passing in one direction and the oil passing in the other may come into contact.

The pipe 60 from the pump 15 is provided with a branch 34 through which make-up oil is supplied to the system. This make-up oil as its name indicates, is to supply in part or in whole, the losses due to conversion, condensation, and removal ofvportions of the oils from the system through the cooler 9 and the separator 10, or

otherwise. Since this make-up oil may be in part used through the valve 31 as an absorbing agent in the tower 11, for which purpose light gas oil is also drawn by pump 15 through the heat exchanger 1'7 from the bottom of tower 8, obviously the make-up oil to cover this purpose may be gas oil. In such case it may be assumed, as will be understood by those skilled in this art, that the charging stock supplied from pump 54 is also gas oil. It will be also understood however by those skilled in the art that our method 14 is included directly between the ouput of thev cracking coil 56 and the input of the fractonator tower 6. In this position the pump maintains a subatmospheric pressure in the crackingcoil and the fiashpot, and an atmospheric or superatmospheric pressure on the vapors passing into the fractionator 6 and through the-rest of the system.

Referring to Fig. 3, the same parts and the same operation are apparent, with the exception that instead of being connected directly between the cracking coil 56 and the rst fractionator tower 6, as in Fig. 2, the pump le is shown disconnected from the circuit of Fig. 2 and con-a nected between pipe 30 leading from the sepa" rator i0, and pipe 42 leading to the absorbing tower il. With this connection it will be found that suction exists together with a subatmospheric pressure produced thereby all the way back from the pump .if-i through the pipe 30 and the separator 10, through the cooler 9 and the fractionating towers 8, 7 and 6, through valves 5 and 3 which are now opened, (the valves 4 and 19 being understood to be closed and thereby eliminated) and through the cracking coil 56 and the open connection therefrom to the flashpot 1. By these means the entire system is placed under subatmospheric pressure, and this speciiic mode of operation of the process will be claimed herein.

The operation of the system thus described is as follows: charging stock is pumped into the primary heater 57 by pump 54 and is heated inthe furnace 2a at first by burners 52h and afterward by heated gases and products of comm bustion from furnace 2, to a temperature of from 400 F. to 800 F. which is above the equilibrium boiling point at the subatmospheric pressure maintained in the flashpot, that is to a point higher than that required for vaporization of the grade of oil under treatment, or` in other Words, the charging oil is heated under pressure. It is then admitted through valve 23 to the fiashpot wherein it instantly passes into the vapor phase. The reduced pressure causes more of the hot oil, or superheated oil, ,entering the flashnet l2!) to be vaporized than is possible at .atmospheric pressure. It also reduces the tendency of the .vapor to be condensed by the walls of the ashpot. That vapor which does condense will be a heavy residuum and is removed from the flashpot 1 lthrough line 24, by a pump not shown in the drawings. In this vapor form the oil is drawn in a turbulent, rapidly moving body through the cracking coil 56 wherein it is heated to a temperature preferably vfrom 1000 F. to 1200 F., and through the valved pipe 5 into the tower 6. In this tower the first separation takes place, the vapors as they rise meeting the gas oil from pump 13 entering the tower through valve 18 and also encountering the surfaces of the heat 136 exchanger 26. The result is a cooling and deposit of heavy fractions or a tarry asphaltic mixture which is removed from the system by the pump 12. The heavy gas oil admitted through the valve 18 dilutes this tarry mixture so as to pre- 140 vent the deposit of any dried coke or tar in the tower. Y

The vapors thus initially cleansed are at a temperature of from 650 F. to 720 F. and pass over the first gooseneck into the lower part 011 the second tower 7 and rise up through the bubble pans and through the recticulations of the heat exchanger 27. There is thrown down` in this tower (assuming the crude to be of average formula) heavy gas oil, which is drawn ntf' by l the pump 13 and carried back to the tower 6 as above stated. That part of it which is not required for washing out the tar referred to, is passed upward by opening the valve 47 to the heat exchanger 26 and thence through pipe 22 to the flashpot for retreatment. The contact of the vapors with the heavy gas oil over the bubble pans or their equivalent serves to strip ab-l sorbed light oils from the heavy gas oil before it is drawn off. The vapors, having given up more heat through the heatexchanger 27, pass through the second gooseneck tothe lower part of the third tower 8 through which they bubble up as before and in addition to the bubble pans, they pass through the reticulations of the heat exchanger. 28. The condensate in this case is a light gas oil, which is stripped of absorbed gasoline-like material or other light oils by the rising vapors, and the low boiling fractions remaining as vapors or fixed gases go over through the top of the tower and the third gooseneck to the cooler 9 wherein condensable portions are condensed and pass to the separator 10. Valved pipe 29 leads from this separator 10 to storage, while the pipe goes to the pipe 42 and thence to tower 11, carrying the cooled fixed gases with exchanger. 17, it should be noted, must be of.'

such a type and capacity, and so esigned, as to cool the oil passing throughit to the pump 15 so that it may be as near atmospheric temperature as possible, and to this end it may if necessary be supplemented by any known or suitable cooling device 1'1 (see Fig. 2). This oil-after passingv through the valve 31 meets the uprising xed gases, absorbs ,the gasoline-like material carried thereby and carries the same down with it tothe bottom of the tower l1 from whence it isdrawn oif by pump 16` and forced back through the heat exchanger i7 and the valve 33 into the tower 8, In passing from the tower .11A throughthe heat' exchanger 17 and into the tower 8, the gas oil with the absorbed gasolinelike material becomes heated, and in the tower 8 the gasoline-like material vaporizes, rises, and goes over the gooseneck, being condensed in the cooler 9 and passed through theseparator 10 to the storage tank. The fixed gases in tower 11 pass out of the top thereof through the waste pipe 48.

By stripping the absorbing oil of its light gasoiine-like Vcontent in the presence of the heavier vapors in tower 8, We get a product more stable under atmospheric conditions thanv is gasoline produced in the ordinary way and having the light strippings from the absorbing oil added to it afterwards. In other words, the absorbing tower 11 operating in connection with the tower d, constitutes a stabilizing system which also takes advantage of the heat available in bottoms from tower 8, and uses the same to strip the absorbing oil of its light gasoline-like content.

it is obvious that it is possible to adjust the valve and the valve 32 or the valves of the pump 54 typied at 23 so that theoriginal charg- In this` ing stock and the make-up oil will be fed in in complementary quantities and so as to maintain equivalent average temperatures and pressures in the pipes 22 and 52 leading to the fiashpoiti The valves 23 and 38 materially assist in this adjustment, so as to produce uniform average temn perature and pressure at the ashpot, whetherthe input is fresh charging stock, or wether it is reflux fractions drawn from the towers 7-8 by the pumps 13 and .15, or make-up oil entering the system through pipe 34.

. It may be noted in passing that we use the words maire-up oil for convenience as follows: make-up oil, or chargingv stock, are really one and the same thing; but in a cracking systemI of this kind there is a definite quantity of the charging stock which during operation is consumed or converted to gasoline-like material. As this conversion is edected, a quantity of the charging stock. must obviously be added to the system to make up for that quantity which has been converted and taken from the system, hence our use of'the term. make-up oil. Wehave used the words light gas oil in the description because in this case we assumed as a matter of consistency that the charging stock described was light gas oil. This 'point .should be noted, that in addition to the make-up oil which enters through the pipe 3d there are also the reiiux fractions from pumps 13 and l5 which pass up through the pipes 60 and 61. It 105 is part of the invention in this case to abstract anduse the vheat taken from the vapors in the dephlegmators 6, '1 and -f to preheat the reflux make-up oil which of course is charging stock, so that the preheater 57 may be shut down in whole or in part. In starting the system on stream, it is necessary to charge the system from the pump 54 and to preheat the fresh charging stock in the preheating still 57. After a sufficiency of this oil is introduced and heated however, the temperature of the vapors in the three towers 6, -7 and 8 willhave been raised to preheating temperature and thereafter, make-up oil or charging stock is introduced through the pipe -34 and the valve 35 and is passed through the heat exchangers 28-27--26 and the pipe 22 to the ashpot 1 as previously stated. It will now be understood that the only diiference betweenl charging oil introduced by pump 54 and by the pipe 3a and valve 35 lies in the fact that the former has to be preheated while the system is cold and therefore goes to the iiashpot through the preheater 57, while after heat has been developed and cracking and'fractionating are pro'- c'eeding, the charging stock or make-up oil is heated and goes back to the iiashpot through the heat exchangers 28`-'2'126. v

It is to be understood that the above apparatus is only one of the forms of apparatus that i may be used to obtain iight oils from hydrocarbon vapors by our process. The form of apparatus is governedlargely by the nature of the vapor under treatment. Thus, we are not limited to any particular types ofgpump, because the piston type of pump' will work equally as well as the rotary 140 pumps shown in these positions.

The apparatus described above when operated on vapors from petroleum gas .oil of approximately 30 Baume gravity, with a vacuum capable of holding up a 5-inch column of mercury 145 maintained on the system at the separation drum exit 30, gave a yield of 16l to 60 percent according to the character and grade of the crude, of' light A oils having a New Navy ganoline boiling range and 3 to 5 percent of absorbed @t oils which 150. /f

herein and according to our method gives the fol--Y lowing results:

having an I. B. P. of 394 F. and an E. P. of 620 F. l

Time on stream:

96 hours.

Yields Gallons Percent Charging stock 208.02 100. 00 Gasoline like material 108. 53 52. 17 esidue 46. 51 22. 36 Loss as gas 52. 98 25. 47

Total 20s. o2 10o. ec

Temperatures Degrees Fahrenheit Preheating tubes 640 Flash pot 610 Vapors from cracking tubes 1020 Furnace temperature below tubes 1275 Furnace temperature above tubes- 980 Tests on products ,from processing Having thus described in general the operation of our system, it may be remarked that by varying the combinations of valves, pumps, direct and reflux feed, it is possible to use the same apparatus in various ways and for diierent operations, with dilerent' classes of oils. The type of equipment used on our process will, of course, also vary with the kind of vapors under treatment. The equipment shown. in our drawings is that used when operating'on vapors produced from 28 to 36 Baume gravity gas oil derived from petroleum. The apparatus as shown is designed to crack the vapors in the most' efficient way, and then remove the heat from the cracked vapors in such a manner that the heat so removed will not be lost but taken up by oli that is to be va porized and returned to the cracking zone. In this case the heat is removed in four successive stages, in such a manner as to cause the vapors to condense forming into four different products, one of these products being the finished gasolinelike material or related light olL-the desiredv product for which the plant was designed,-an other product being a heavy residuum, and the 7-5 two other products being a heavy and light gas oil respectively which are used in the system to maintain the desired temperature on the incoming vapors, and as an absorbing oil to remove the very light gasoline-like material that is entrained yin the gas from the separator drum.

Regarding the relation of the pressures in different parts of our apparatus, it may be stated that in actual practice we carry from 15 to 60 pounds pressure on our primary still 2a, from 12 to 14 poundsabsolute pressure on the flashpot 1, and from 6 to 14 pounds pressure absolute on our cracking zone 2 and towers 6, 7, 8 and 11.

What we claim is:

l. The method of treating hydrocarbon oils to produce lower boiling 'hydrocarbons from higher boiling hydrocarbonsV which comprises the iollowing steps: forcing charging oil under regulable pressure into a preheating zone, preheating the same therein to a temperature suiiicient to flash the oil into vapor at lsub-atmospheric pressure, while maintaining in said zone a pressure above atmospheric, releasing said oil from pressure in the preheating zone into an expanded flashing zone to flash into vapor substantially the entire amount of said oil while maintaining sub-atmospheric pressure, drawing only the vapors pro# duced in the flashing zone through an open connection into a cracking zone which is under a lower sub-atmospheric pressure, drawing out' the cracked vapors so as to maintain the said low `pressure, passing them through fractionating zones, and passing the desired vapors from the last fractionating zone to cooling and separating zones.

2. The process described in claim 1 in which the charging oil is released from the preheating zone into the flashing zone under sub-atmospheric pressure while pumping on the outlet' of the separating zone to maintain said subatmospheric pressure back through the cooling, fractionating, and cracking zones to the flashing zone.

3. The method of treating hydrocarbon o' s to produce lower boiling hydrocarbons from htgher boiling 'hydrocarbons which comprises the fol-- lowing steps, forcing charging oil into a preheating zone, preheating the same therein while maintaining in said zone a pressure above atmospheric, releasing said oil from pressure in the preheating zone into a hashing zone while maintaining therein subatmospheric pressure by drawing the vapors produced in the ashing zone through an open connection into acracking zone under a lower subatrnospheric pressure, drawing out the cracked vapors so as to maintain said low pressure, passing them through Afractionating zones, passing the desired vapors from the last fractionating zone to cooling and separating zones, and after the system is on stream, reducing said initial charging oil, preheating make-up oil in the fractionating zones under pressure and thereafter releasing the make-up oil from pressure into the ashing zone.

4. The method of treating hydrocarbon oils to produce lower boiling hydrocarbons from higher boiling hydrocarbons which comprises the following steps, forcing charging oil into a preheating zone, preheating the same therein while maintaining in said zone a pressure above atmospheric, releasing said `oil from pressure in the pneheating zone into a flashing zone while maintaining therein subatmospheric pressure by drawing the vapors produced in the flashing zone through an open connection into a cracking zone under a lower subatmospheric pressure, drawing out the cracked vapors so as to maintain said dit low pressure, passing them through iraotionating zones, passing the desired vapors from the last iractionating zone to cooling and sepaating zones, the cracked vapors being passed through the fractionating zones in tandem and cooled therein in successive zones so as to throw down tar in the rst zone, heavy gas olin the second Zone, and light gas oil in the third zone, pumping the vheavy gas oil from the second tothe rst fractonating zone to soften and remove the tar therefrom, and pumping light gas oil from the third fractionating zone bach through the `fractionating zones in conductive relation to but out of contact with the vapors therein, to the flashing zone.

5. rhe method of treating hydrocarbon oils to produce lower boiling vhydrocarbons from higher boiling hydrocarbons which comprises the following steps: forcing charging oil ntoa preheating zone, preheating the saine therein While maintaining in said zone a pressure above atmos pheric, releasing said oil from pressure in the preheating Zone into a flashing Zone while maintaining therein subatinospheric pressure by drawing the vapors produced in the hashing Zone through an open connection into a cracking zone under a lower subatrnospheric pressure, drawing out the cracked vapors so as to maintain said low pressure, passing them through fractionating zones, passing the desired vapors from the last fractionating zone to cooling and separating zones, the cracked vapors being passed through the fractionating zones in tandem and cooled therein in successive zonesso as to throw down tar in the iirst zone, heavy'gas oil in the second zone, and light gas oil in the third zone, pumping the heavy gas oil from the second to the first fractionating zone to soften and remove the tar therefrom, and pumping light gas oil from the third fractionating zone back through the iractionating zones in conductive relation to but out of contact with the vapors therein, to the flashing zone, said reflux condensate from the third fractionating zone being exposed in successive fractionating zones by means of heat absorbing sur faces increasing successively in superficial area from the last to the rst, whereby both the heating effect on the reiiux oil and the cooling effect on the vapors under fractionation may be suitably adjusted.

6. The method of treating hydrocarbon oils to produce lower boiling hydrocarbons Afrom higher boiling hydrocarbons which comprises the following steps: forcing charging oil into a preheating zone, pre-heating the saine therein while maintaining in said zone a pressure above atmospheric, releasing said oil from pressure in the preheating zone into a flashing zone while maintaining therein subatinospheric pressure by drawing the vapors produced in the flashing zone through an open connection into a cracking zone under a lower subatmospheric pressure, drawing out the cracked vapors so as to maintain said low pressure,. passing them through fractionating zones, passing the desired vapors from the last i'ractionating zone to cooling and separating zones, the cracked vapors being passed through the fractionating zones in tandem andl cooled therein in successive'steps so as to throw down condensate therein, pumping condensate from a fractionating zone back under pressure as renur through the said fractionating zones in heat conductive relation to but out of contact with the vapors therein causing the same thereby to absorb heat from the cracked vapors, and nally passing the same into the flashing zone for retreatment.

WILLIS F. SIMS. VENUS U. CLOER.

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