US1965189A - Reduction of residuum from cracking operation by distillation - Google Patents

Description

L. C. HUFF Juiy 3, 1934.

REDUCTION OF RESIDUUM FROM CRACKING OPERATION BY DISTILLATION Original Filed June 30, 1928 Q V MN Patented July 3, 1934 UNITED STATES PATENT OFFICE REDUCTION OF RESIDUUM FROM CRACK- ING OPERATION BY DISTILLATION Application June 30, 1928, Serial No. 289,342 Renewed February 11, 1932 6 Claims.

The present invention relates more particularly to improvements in a method of distilling and reducing residuum from a cracking plant in low pressure stills by the use of heated hydrocarbon oil vapors.

In one specific embodiment of the invention, the

residuum is reduced to coke in the low pressure- 'coke still by the use of heated hydrocarbon oil vapors bled from the cracking operation which produced said residuum.

By means of the present invention, the residuum may be heated at low pressure to ISO-800 F., more or less, and held at such temperature long enough for all the liquid to distill ofi and for the mass to go to coke.

V The utility of the invention as well as objects and advantages thereof will be more apparent from the following description.

The single figure in the drawing is a diagrammatic side elevational view,'partly in vertical section, illustrating a flow chart of apparatus in which the invention may be carried out.

Referring more in detail to the drawing, 1 designates a charging stock inlet line in which is interposed a pump 2 and a valve 3. The line 1 discharges into the upper portion of a suitable fractionating tower or flash condenser 4 from which the unvaporized portions of the charge are 'removed through line 5 and through the pressure imposed by pump 6, interposed in the line 7, said charging stock may be introduced into the upper portion of a dephlegmator or reflux condenser 8 of conventional design and provided with suitable bafiies. The unvaporized portion of the charging stock together with any condensate collecting in the dephlegmator 8 passes down reflux line 9 and under the influence of the hot oil pump 10 is forced into the coil 11 mounted in furnace12.

While I have illustrated the furnace 12 as being of the side-fired type, it is obvious that any other type of furnace may be employed. The oil passing through the heating coil 11 is raised to a cracking temperature through the medium of the combustion gases generated by the burners 13, said heated oil passing into the transfer line 14 in which is interposed the valve 15, from which it discharges into the upper end of an enlarged conversion and/or separating drum 16, which may or may not be internally or externally heated.

The drum 16 is of the conventional type provided with insulation, if desired, and with suitable pyrometers, pressure gauges and manholes for cleaning and repairing. p

In the drum 16 the vaporousproducts separate from the non-vaporus products of conversion, said vapors passing through the vapor outlet line 17, in which is interposed valve 18,'discharging into the lower portion of the dephlegmator 8, where said vapors are brought into heat interchange with the charging stock introduced through line '7, as heretofore described. Vapors remaining uncondensed after passing through the dephlegmator pass out through vapor outlet pipe 19, controlled by valve 20, being condensed in conventional condenser 22 and collected as liquid dis- 6S tillate in receiver 23. The receiver 23 is provided with the usual gas relief pipe 24 controlled by valve 25, and with the liquid draw-off line 26,

'controlled by valve 27. If desired, regulated portions of the distillate collecting in receiver 23 may "be diverted through the line 28, in which is interposed pump 29, and valve 30 into the dephlegmator 8 to assist in the reflux condensing action taking place therein.

The heating coil 11, drum 16 and dephlegmator 8 may be maintained under any desired conditions of pressure. Normally, these parts of the plant are maintained under a superatmospheric pressure, but this is not to be taken as a limitation of the invention.

Returning now to the drum 16, the unvaporized residuum may be withdrawn from the drum 16 through one or a number of the residue drawofi lines 31, controlled by valves 32 and discharged into a flash chamber or still 33. The flash chamher 33 derives its descriptive name from the fact that the pressure previously maintained on the residue is reduced or released altogether prior to its introduction to the flash chamber 33 which release of pressure, due to the latent heat contained in said residuum, causes vaporization of a substantial portion thereof. In this instance the valves 32 function as pressure reducing valves. The vapors separated in the flash chamber 33 may be removed through the line 34, in which may 9 be interposed valve 35, discharging into the flash condenser 4, previously described, wherein reflux condensation takes place between said flashed vapors and the raw charging stock, the material Passing down through the pipe 5, comprising 1 0 condensed flashed vapors and unvaporized charging stock.

Vapors remaining uncondensed after passage through the flash condenser 4 may pass out through the vapor outlet-pipe 36, in which may 10 be interposed a valve 37, being condensed in the conventional condenser coil 38 and collecting as liquid distillate in the receiver 39. The latter may be provided with the usual gas relief pipe 40, which may be'controlled by valve 41, and 11 with the liquid draw-off line 42, which may be controlled by means of the valve 43.

Returning to the flash condenser 4, a suitable cooling medium may be introduced through the line 44 to the coil 45 disposed in the upper portion of the flash condenser, beingrernoved from said coil through the line 46. The cooling coil 45 may, of course, be dispensed with, depending upon the conditions of operation.

Returning now to the flash chamber 33, the unvaporized flashedresiduum may be removed from said chamber through one or more of the residuum draw-off lines 47, controlled by valves 48, and may be passed to any suitable cooler and thence to storage. Or, as a feature of the present invention, said residue may be withdrawn through the line 49 controlled by valve 50 and passed into a header 51 having branches 52 each controlled by a valve 53. Each of the branches 52 may communicate with a low pressure still 54 which may take any desired form for the accomplishment of the purpose for which it is used, as will be hereinafter described.

The object of providing a low pressure still 54 is to reduce the residue by distillation for the purpose of removing therefrom desirable lighter fractions contained therein so as to increase the final proportionate yield of desirable products, and in addition to convert the residue to coke. To supply heat for the purpose of this reduction by distillation, I propose to bleed a regulated quantity of vapors from the vapor line 1'7 through the line 55 by proper manipulation of the valve 55. The line 55 is provided with branches 56 and 57, 5'7, controlled respectively by valves 58 and 59, 59. The purpose of the branch 56 is to divert a regulated portion of the vapors, if desired, into the junction where the line 49 meets the header 51 whereby said heated vapors will be brought into contact with the residue from flash chamber 33 prior to the introduction of said residue into the still 54. The purpose of providing two or more stills 54 is to permit the residue in one chamber to be reduced to coke while another still is being charged with said residue.

The concept of the invention comprises the step, first of bringing the vapors and residue into contact prior to introduction to a still 54 and/or the continued introduction of vapors to a still 54 during and/or after it is charged with residue. Vapors released in the stills .54 pass out through vapor line 60, controlled by valve 61, into the header 62, passing through the separator, diagrammatically illustrated at 63 for separating entrained coke particles which may be carried over by the injection of vapors to the stills, and from the latter passing through the line 64 to the flash condenser 4. Each still 54 may be provided with the usual safety valve 65 and steam or gas release 66 controlled by-valve 67. Each of the stills 54 may be insulated to prevent loss of heat by radiation, and the heat necessary for distillation may be supplied entirely by the vapors, or said stills may be externally heated if desired.

From the foregoing it will be apparent to those skilled in this art that I have devised and perfected a very novel method of reducing and coking residue from a cracking plant in a low pressure zone, the heat for such reduction and distillation being secured by utilizing the heat given up by diverting regulated portions of the vapors produced in the cracking operation which produced the residue. It is obvious, of course, that the vapors may be withdrawn from any point in the vapor line 1'7, or if desired they may be withdrawn by tapping a separate line into the drum 16. Since the vapors leaving the top of the drum 16 will be between a temperature of 775 and 825 F.', more or less, the heat given up by said vapors will be sufilcient to effect the amount of distillation desired.

When a body of residue builds up in one of the stills 54, the incoming residue is then shut off and diverted to a second still. Hot vapors 35 are then introduced into the lower part of the first chamber into direct contact with the residue therein, which ultimately distills the liquid and cokes that part of it which does not vaporize.

The temperature conditions maintained in the still 54 can be regulated, of course, by controlling the quantity of vapors introduced thereto.

After coke is formed in one of the stills 54 steam may be admitted for cooling purposes, after which water may be introduced and then the coke may be removed by pulling a cable imbedded therein in the same way that coke and carbon is now removed from reaction chambers. It is obvious that the vapors used for distilling the residue may originate in a cracking operation other than the 10 In addition to the other features noted above, 10 according to the present invention it may be pointed out that it is of tremendous advantage in commercial operation to combine cracking, flashing and coking in a single continuous operation. The vapors released in the distilling and coking operation are returned to the cracking system for further treatment. Steam may be introduced to the stills 54 through the lines 68, controlled by valves 69. Since the shell may take any of the conventional forms of a still,

it is cleaned out and evacuated by any of the well known means for cleaning shell stills.

I claim as my invention:

1. A process which comprises continuously removing heated residue from a cracking plant operating under superatmospheric pressure while said plant is in operation, reducing the pressure thereon to vaporize substantial portions thereof by means of the latent heat contained in said residue, removing the residue from the latter operation and distilling same by bringing into direct contact therewith heated hydrocarbon oil vapors, comprising a controlled quantity of vapors produced in the same cracking operation which produced the residue, and continuing the distillation of said residue to coke without recirculating any undistilled portion of said residue to said cracking plant.

2. A process which comprises continuously removing heated residue from a cracking plant,

operating under superatmospheric pressure, while said plant is in operation, reducing the pressure thereon to vaporize substantial portions thereof by means of the latent heat contained in said residue, removing the residue from the latter operation and distilling same by bringing into direct contact therewith heated hydrocarbon oil vapors, continuing the distillation of the residue to coke without recirculating any undistilled portion of said residue to said cracking I50 Instead of utilizing vapors, a 105 plant, recracking hydrocarbon constituents 'evolved from the residue and utilizing the resultant cracked vapors as at least a portion of said heated vapors.

3. A hydrocarbon oil cracking process which comprises subjecting the oil to cracking conditions of temperature and ,pressure in a cracking zone, removing vapors and unvaporized oil from the cracking zone, flash distilling the unvaporized oil in a flashing zone by pressure reduction, removing the residue from the flashing zone and introducing the same to a coking zone, introducing a portion of the vapors removed from the cracking zone into the residue in the coking zone and distilling the residue to coke in the coking zone without recirculating any undistilled portion of said residue to said cracking zone.

4. A hydrocarbon oil cracking process which comprises subjecting the oil to cracking conditions of temperature and pressure in a cracking zone, removing vapors and unvaporized oil from the cracking zone, flash distilling the unvaporized oil in a flashing zone by pressure reduction, removing the residue from the flashing zone and introducing the same to a coking zone, and distilling the residue to coke in the coking zone by injecting hot cracked hydrocarbon vapors thereinto and without recirculating any undistilled portion of said residue to said cracking zone.

5. A hydrocarbon oil cracking process which comprises passing the oil through a heating zone and heating the same therein to cracking temperature under pressure, discharging the heated oil into a vapor separating zone and separating the same therein into vapors and residue, separately removing the vapors and'residue from the separating zone, dephlegmating a portion of the removed vapors and returning resultant reflux condensate to the heating zone, flash distilling the removed residue in a flashing zone maintained under lower pressure than the separating zone, removing the remaining residue from the flashing zone and reducing the same in a coking zone to coke by injecting thereinto another portion of the vapors removed from the separating zone and without recirculating any undistilled portion of said residue to said heating zone, the last-mentioned vapors being passed from the separating zone into the residue without any substantial cooling.

6. A hydrocarbon oil cracking process which comprises subjecting the oil to cracking conditions of temperature and pressure in a cracking zone, removing vapors and unvaporized oil from the cracking zone, flash distilling the unvaporized oil in a flashing zone by lowering the pressure thereon, reducing the unvaporized oil to coke in a coking zone independent of said flashing zone by injecting hot cracked vapors thereinto and without recirculating any undistilled portion thereof to said cracking zone, combining and condensing the vapors evolved from the unvaporized oil by its flashing and reduction to coke thereby forming condensate, subjecting condensate thus formed to cracking conditions of temperature and pressure and utilizing the resultant vapors, without prior cooling and condensation thereof, as at least a portion of said hot cracked vapors.

LYMAN C. HUFF.

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