US2085027A

US2085027A - Method of producing low boiling hydrocarbons

Info

Publication number: US2085027A
Application number: US369175A
Authority: US
Inventors: William O Keeling
Original assignee: Individual
Current assignee: Individual
Priority date: 1929-06-07
Filing date: 1929-06-07
Publication date: 1937-06-29
Anticipated expiration: 1954-06-29

Description

June 29, 1937. w. o. KEELING 210851027 METHOD OF PRODUCNG LOW BOILING HYDROCARBONS Filed June 7, 1929 D N N 63 Patented June 29, i937 naar? J SAVTS TNT FFEE i METHQD F PRODUCING LOW BOILING HYDROCARBONS William 0. Keeling, Independence, M0.

Application .lune 7, 1929, Serial No. 369,175

2 Claims.

` This invention relates to a process of and apparatus for converting highiboiling hydrocarbons into low boiling hydrocarbons, and has for its object to provide, in one continuous operation and in a manner as hereinafter set forth for the cracking of the heavy ends of the cracking stock in the vvapor phasel by the introduction of fresh hot gases or vapors at one or more xed independent points and further for distilling off the ,10 lighter ends of the cracking stock resulting in an unusually satisfactory and inexpensive product, the properties of which are substantially gravity A. P. I. 45 to 55, aniline cloud point under 30 C., unsaturates (by H2SO4) between 20-50%, A. S. 5 T. M., boiling point rangesY as for. commercial gasolines, I-I. U. C. R. 5.5 to 7.0,and iodine No. 150 to 250.

This application is a continuation in part of my copending application, Serial No. 223,054, filed September 30, 1927. v

A further yobject of the invention resides in the maintaining of the cracking 4temperature by theintroduction of fresh hot gases or vapors at xed independent points without the supplying 95 of air for combustion purposes tothe cracking chamber or chambers whereby the cracking operation,V in accordance with this invention is carried out at a materiallyless,V expense with respect to the processes now employed for they same 30 purposes. .i l i A further object of the invention is to provide,

in a manner as hereinafter set forth, whereby the cracking is hadwith the avoiding of excessive deposition of carbon and with a exible control of cracking temperature. f

A Vfurther object of the invention is to provide, in a manner as hereinafter set forth, the'combination of cracking and distillation in one unit.

A further object of the invention is to provide,

,lo in a manner as hereinafter set forth, whereby a conservation of heat is had due to direct contact between the heating agents and oil to be cracked and the oil to be distilled.

A further object of the invention is to provide,

45 in ai-manner as hereinafter set forth, for the introduction of fresh hot gases or vapors, of any kind at a plurality of fixed, independent points and then expanding the mixture after the introduction of each fresh charge of hot gas or vapor.

,7,0 A further object ofthe invention is to provide,

in ak manner as hereinafter set forth, for regulating the temperature of the fresh hot gas or vapor at each point of introduction in order that the composition of the cracked products 55 may be varied as desired,

A further object of the invention is to provide, in a manner as hereinafter set forth, whereby after the last expansion of the mixture, the heat in the cracked oil vapors and heating gases or vapors is utilized to distill off the lighter end of the charging stock.

A further object of the invention is to provide, in a manner as hereinafter set forth, whereby the vapors and gases pass through fractionating columns where the various fractions can be separated.

A further object of the invention is to provide, in a manner as hereinafter set forth, for recirculating the gases or vapors, using part or all of them to vaporize cracking stock or to crack a vaporized charging stock. i

A further object of the invention is to provide for compressing oil vapors and fixed gases, if desired, before finally condensing the former.

With the foregoing and other objects in View the invention consists of the new, novel, improved, 20 expeditious means in a manner as hereinafter referred to for converting high boiling hydrocarbons intol low boiling hydrocarbons by cracking, but it is to be understood that changes in the details of the process and apparatus can be had which will fall within the scope of the claims hereunto appended.

As illustrating one form of an apparatus capable'of carrying out the process, in accordance with this invention, for converting high boiling hydrocarbons into low boiling hydrocarbons, reference is had to the accompanying drawing which illustrates such apparatus diagrammatically. The manner of converting high boiling hydrocarbons into low boiling hydrocarbons and for distilling olf the lighter ends of the cracking stock, the converting and distilling being carried on continuously and in one unit is as follows:

Cold charging stock to the unit is split into two streams, one of which goes through the iinal heat exchanger or `partial condenser to extract heat from the fractionated gasoline and fixed gases and part goes through reflux condensers in the top of each column or tower, either in series 4- or in parallel. 'Ihe apparatus or unit as illustrated shows it going through each column in series. The stream from the partial condenser next passes through a heat exchanger, not shown, through which the hot residuum from the Vaporizing column is pumped and cools the residuum down so that it can be pumped to storage.

The two streams of charging stock next come together again and empty on to one of the decks or trays in the stripping column, said tray being determined by the nature of the charging stock. The stock travels down the column counter-current to hot ascending gases or vapors or mixture of both. The lighter ends of the charging stock are distilled off over into the iirst fractionating column or tower. The hot bottoms are pumped to the vaporizer column.

The oil vapors from the cracking Zone together with those from the stripping column pass into the bottom of the iirst fl'actionating column where the heaviest ends of the o-il are fractionated out and returnsto the bottom of the column from where it is picked up by pump and pumped to the vaporizer column. It can be heated to a temperature above its vaporization temperature enroute if desired. The vapors and gases pass to the second fractionating column where all the remaining hydrocarbons of boiling point greater than those contained in gasoline are fractionated out and refluxed back to the vaporizer column. This refiuxed oil can be drawn ofi from the botto-m of the column and sold as furnace distillate or can be mixed with the refluxed oil in the first column, and pumped to the vaporizing column or first mixing chamber as cracking stock.

The remaining vapors and the fixed gases leave the top ofthe second fractionating column and pass through the partial condenser where they give up part of the heat they contain to the cold incoming charging stock or are compressed before going to iinal condenser. Any condensed gasoline is trapped off from the partial condenser to the separator. From the partial condenser the remaining vapors and gas pass through a Water cooled condenser where the rest of the condensible vapors are condensed. The fixed gases and condensed gasoline next go to the separator where the iixed gases and gasoline are separated. The gasoline is drawn off .and pumped to storage.

The 'xed gases containing a small amount of 'uncondensed gasoline vapors are: drawn from the separator, compressed and sent through an absorption unit to remove the uncondensed gasoline. If gases are of suiiicient pressure before going to the final cooler the compression step is unnecessary. After this stripping, the fixed gases pass through a heater and thence through a manifold to the mixing chambers.

If the unit is operating on crude oil or residues, the bottoms from the stripping column may be introduced into the vaporizing column. The bottoms from the first and second fractionating columns may be introduced into the iirst ,mixing chamber and there vaporizedY or may be also introduced into the vaporizing column and there vaporized.

If the unit is operating on gas oil, the bottoms from the stripping column may be introduced into the vaporizing column and the bottoms from fractionating columns l and 2 introduced either into Vthe mixing chamber or into the vaporizer column for vaporization.

- A portion of the bottoms from the vaporiaing column can be recirculated over the column to insure the greatest possible amount of volatile materials has been distilled off and the remainder can'then be drawn off through the reboilers of the fractionating columns toY help heat the re fluxed oil from these towers.

The oil vapors and fixed gases passing from the top of the Vaporizer column are mixed with fresh hot gases or vapors in the second mixing chamber and after thorough mixing to insure complete heat exchange, are expanded in the first reaction chamber Where such lilrlg Occurs as the temperature permits. On leaving the top of this reaction chamber, the mixture is again mixed with another fresh charge of hot gas or vapors and after thorough mixing for heat exchange is expanded into the second reaction chamber where such cracking takes place as the temperature permits. This can be repeated as many times as desired. Y

The mixture of hot gases and vapors leaves the last reaction chamber and enters the bottom of the stripping column. As it ascends this column it heats the charging stock and distills oii the light ends. The term hot gases is to mean hot gases or hot vapors.

Referring to the drawing the apparatus as ilu lustrated includes a stripping column l provided with spaced, superposed trays 2 and a reflux condenser 3 therein at the top thereof.' A primary and a secondary fracticnating column Il, 5 respectively, having therein at the tops thereof reflux condensers 6, 'iy tionating column has arranged therein spaced, superposed trays 8. The apparatus further includes primary and secondary reaction chambers 9, I respectively, a Vaporizing column ii provided with spaced, superposed trays I2, an absorption tower i3, a separator Id, a heat exchangerV I5, a water cooled condensing coil I5, a heater Il, a pair of reboilers I3, I9 and a series of mixing Zones 2i), 2l, and 22.

The condenser 3 discharges into the top of column I. The condenser 6 is closed to column 4 and opens into condenser 3 by a pipe branch 23 between columns I and il. The condenser 'i is closed to column 5 and opens into condenser 6 by a pipe branch 24 between columns 5 and ,5.

The apparatus further includes an incoming stock charging line 25 provided with a pair of branches 26, 27, the former extending throughV the heat exchanger I5 and opening into the discharge 28 of condenser 3. The branch 2I`opens into the condenser 1. Leading from the bottom of the heat exchanger I5 and opening into the top oi' column 5 is a carrying oi pipe 29 for the resultant product with the hot gases and vapors.

Leadingv from the heat exchanger I5 to the separator i4 is a valve controlled pipe 3E for discharge of the heavier products.

Leading from the top of the heat exchanger I5 to the coil I6 is a valve controlled carrying ofi pipe 3l and communicating with the pipe 3| and coil It is a by-pass 32 having interposed therein a pump 33. Leading from the bottom of coil I6 and opening into the top of separator I4 is a discharge pipe 3G. The separator It is closed. A valve controlled gasoline draw oft pipe 35 leads from the bottom of separator I4.

The apparatus further includes a valve controlled carrying ofi pipe 36 leading from separator Ill to a pump 31 which opens into the bottom of tower I3. The pipe 35, in proximity to and above the controlling valve S8 thereof has extended therefrom a valve controlled branch 39 which opens into tower I3. Extending from th-e tower I3 to mixing chamber 2g and also through heater I 'I is a hot gas or vapor supply pipe e3 having valve controlled branches 4I, 2, the former opening into mixing chamber 2l and the latter into mixing chamber 22.

Leading from the top of column II, communicating with mixing chamber 2l and opening into the bottom of reaction chamber 9 is a conductingfpipe 43. Leading from the top of reaction chamber 9 is an outlet pipe Lili which opens into mixing chamber 22 and extending from the respectively. Each fraclatter to the bottom of reaction chamber I0 is a conducting pipe 45. Extending from the top of reaction chamber I 0 to the bottom of stripping column I is a conducting pipe 46. Leading from the top of column I to the bottom of primary fractionating column is a conducting pipe 41 and leading from the top of column 4 to the bottom of secondary fractionating column 5 is a conducting pipe d8.

The reboilers I8, I9 are arranged below columns 4, 5 respectively, and discharge pipes 49, 50 respectively lead from columns d, 5 respectively, and opening into reboilers I8, I 9 respectively. Reboiler I8 is provided with a valved discharge pipe 5I which opens into branch 52 of a heated stock supply line and the latter further includes

branches

53, 55, 55 and 56 and a pump 56. The branch 52 leads from reboiler I 9 to pump 56'. Branch 52 hasr a controlling valve 52 in proximity to reboiler I9. Pipe 5I opens into branch 52 below reboiler I8. Branch 53 leads from pump 56 to branch 54 and the latter opens into branch 55. Branch 5B leads from the bottom of column I to the lower end of branch 55 and the latter is adapted to communicate with the mixing chamber 20. Communication between branch 55 and chamber 20 is controlled by a valve controlled branch 5l'. Leading from branch 55 to column II is a series of superposed valve controlled

inlet branches

58, 53, 50, 6I and 62 having associated therewith shut-

01T valves

53, 64, 55, BB and 51 arranged in branch 55 above the points of communication between said inlet branches and branch 55. Below inlet branch 62, branch 55 is provided with a controlling valve 68. The hot gas or vapor supply line 40 has a controlling valve 69 in proximity to mixing chamber 2li and the controlling valves for the branches 4I, 42 of line l0 are indicated at l0, 7| respectively.

Leading from the bottom of column II is a valve controlled fuel line 'I2 which extends to storage not shown. The line 'I communicates with a pump 'I3 from which leads a vertically disposed branch 'I5 opening into column II. The line 'I2 passes through the reboilers I8, I 9. Leading from reboiler i9 is a valve controlled conducting line l5 which extends to storage not shown. Leading from the bottom of tower I3 is a valve controlled conducting line 'i6 extending to a fat oil still not shown.

With the cracking and fractionating part of the system working at low pressures, the combined gases and vapors from fractionating tower are drawn into pump 33 and compressed to desired pressure before they are discharged into condenser. This makes possible the use of a smaller condenser surface and because of the increased pressure, reduces the amount of gasoline vapors carried through the condenser by the fixed gases. If the system pressure is sufliciently great this pump can be bypassed, the vapors and gas from fractionating column discharging directly into condenser through bypass 32.

The pump 'I3 is used to pump part of the bottoms from the vaporizer column up over the top of the column to insure thorough stripping of all charging stock from the bottoms.

The branch line 'lli carries the oil from the discharge outlet of pump 'I3 and discharges the oil onto the top decks of the Vaporizer column.

The tower I3 is an absorption tower where uncondensed gasoline vapors from the condenser and separator, carried along with the uncondensed gases, are stripped from these gases by means of absorption oil. This tower serves the same purpose as does an absorption tower in a gasoline recovery plant extracting gasoline from natural gas.

The pump 31 is used to compress gases-and vapors before theirl admission to the absorption tower if a pressure greater than that in condenser or separator is desired. When the pressure in the condenser and separator is sufiiciently great the pump 3l can be bypassed and the gases and vapors are admitted to the absorption tower through the bypass line 39.

The pipe 30 is used to draw off any gasoline condensate from the heat exchanger to the separator.

The reboilers I8 and I9 are sumps at the bottoms of the fractionating columns into which the reflux oil from each column gravitates. These reboilers are heated by closed coils through which hot residuum from the vaporizer column passes so that all light ends in the reflux are re-vaporized and again ascend the columns.

Valves

53, 64, 55, E6, B7 are manifold va-lves so arranged that the oil from reboilers I8 and I9 and bottom of stripping column can be introduced onto any plate of the vaporizer column desired.

The heat exchanger referred to is of conventional construction. Wherever exchangers are employed it should be understood one or more may be used and that all are of conventional design.

An example of working conditions and kinds and proportions of material is as follows:

The charging stock is a topped residuum from a Mid-Continent crude. The gas used is a 50-50 mixture of methane and hydrogen. The residuum is charged into the stripping column I at substantially atmospheric temperattue. 'Ihe residuum is heated to approximately 650 degrees Fhr. by contact with the hot gases and cracked vapors from the last reaction chamber. At this temperature approximately 50% of it is vaporized, (the partial pressure effect of the gases enabling maximum vaporization at this low temperature.) The hot residuum is picked up by pump from the bottom of the stripping column and pumped through mixing chamber 25 or onto the lower trays in the vaporizer column I i. Condensed gas oil is picked up by pump from the bottoms of fractionating columns I .and 5 after passing through reboilers I3 and I9 where it is raised to approximately 590 degrees li'hr., and is discharged either into the mixing chamber 2!) or into the ,f

upper decks of the vaporizing column.

Hot gas at about 1100-1200 degrees Fhr. is introduced into the bottom of the column through mixing chamber 29, and passes up through the column beating up the oil and vaporizing the gas oil fractions. 'Ihe temperature of the fuel oil drawn off from the bottom of column averages 650 degrees-700 degrees Fhr. and that of the oil on the top trays 500-650 degrees Fhr. The combined oil vapors and gases leave the vaporizing column and pass through mixing chamber 2| where they are contacted with hot gas at about 1300 degrees Fhr. so that the temperature of the mixture is about 960 degrees Fhr. The proportion of gas to oil at this point is about 60 cu. ft./gas to every gallon of oil vaporized in II. The mixture is discharged into the first reaction chamber 9. Due to the heat absorption incident to the cracking reaction the temperature of the mixture leaving chamber 9 is about 935 degrees Fhr. The mixture then passes through the mixing chamber 22 where it is mixed with hot gas at about 1300 degrees Flir. Sufhcient gas is introduced to raise the temperature of the resulting mixture to about 975 degrees Fhr. At this point the ratio of gas to oil is about cu. ft. of gas per gallon of oil vaporized in column ll. If more than two reaction chambers are employed the same procedure is' employed so that the cracking temperature is maintained at about 970 degrees Fhr. at the entrance to each reaction chamber. At' the exit of the last chamber the temperature of the mixture is about 940 degrees F111. The temperature is reduced during the passage through the stripping column to 450 degrees Fhr. and through the fractionating towers so that at the exit of the last fractionating tower the temperature is about 200 degrees Fhr. The ratio of gas to oil is calculated at atmospheric temperature and pressure.

The effect of time on ultimate yield is substantially as shown:

1 Temperature at start ol cracking reaction only and is not the nni form temperature during entire cracking reaction.

With a cubical capacity of 30,000 cu. ft. for each of the reaction chambers, two would result in a total capacity of 60,000 cu. ft. If three be used a total capacity of 90,000 cu. ft. will result. If the compressor capacity is such that thev gas is circulated at the rate of 15,000 cu. ft. per minute, the cracking time for two chambers would be 4 minutes and for three chambers would be 6 minutes. By bringing the cracking temperature up to 975 degrees Fhr. at the entrance of each chamber, the total conversion would be approximately 15.75% for each chamber or 31.50% for two chambers or 47.25% for three chambers, etc. If fresh hot gas be not added at the entrance of each chamber the total conversion would be 15.75% 975 degrees Fhr. in the first chamber, 9.0% @l 925 degrees Fhr. in the second chamber, and approximately 3%I 875 `F. in the third chamber etc., or a total of 24.75% for two chambers and 27.7% for three chambers etc.

If the volume of gas circulated be cu. ft./ gal. of oil, at atmospheric pressure the capacity of the system Would bev approximately gallons per minute. If the System pressure be absolute, the capacity of the same unit would be gallons/minute. Since the oil is vaporized before entering the cracking zone, the only effect of pressure is to increase the charging capacity of a unit of fixed cubical volume.

What I claim is:

1. In a process in which a hydrocarbon oil is heated to vaporizing temperatures and separated into vapors and unvaporized oil and the vapors admixed with hot gases in successive steps and time intervals of reaction are permitted after each successive adrnixture of hot gases, the improvement which comprises admixing the hot gases with the oil vapors in a` mixing zone in'such quantity and amount as to raise the oil vapors to active vapor phase cracking temperature, and supplying the time interval of reaction by reducing the Velocity of flow of the mixture, and permitting the cracking to take place substantially solely by the sensible heat of the hot carrier gas.

2. In a process in which a hydrocarbon oil is heated to vaporizing temperatures. and separated into vapors and unvaporized oil and the vapors admixed with hot hydrocarbon gases in successive steps and time intervals of reaction are permitted after each successive admixture of hot hydrocarbon gases, the improvement which comprises admixing the hot hydrocarbon gases with the oil vapors in a mixing zone in such quantity and amount as to raise the oil vapors to active vapor phase cracking temperature, and supplying the time interval of reaction by reducing the velo-city of ow of the mixture, and permitting the cracking to take place substantially solely by the sensible heat of the hot hydrocarbon carrier gas.

WILLIAM O. IiEELING.