US2140342A - Distillation process for hydrocarbon oils - Google Patents

Description

Dec. 13, 1938- J. s. WALLIS ET AL DISTILLATION PROCESS FOR HYDROCARBON OILS 5 Sheets-Sheet l Filed Feb. 23, 1934 ///.'s KW A TORNE Y m. NSS

MNYQS Dec- 13, 1938- J. s. wALLis ET AL DISTILLATION PROCESS FOR HYDROCARBON OILS Filed Feb. 23, 1934 3 Sheets-Sheet 2 /N VENTORS A f TOR/VEP Dec. 13, 1938.

`J. s. WALLIS Er A1.

DISTILLATION PROCESS FOR HYDROCARBON OILS Filed Feb. 23, 1934 3 Sheets--Sheefl 3 Patented Dec. 13,1938

UNITED STATES PATENT OFFICE DISTILLATION PROCESS FOR HYDE()- CARBON OILS Application February 23, 1934, Serial No. 712,536

Claim!- (Cl. 1965-77) Our invention relates to a distillation process for hydrocarbon oils and more particularly to a vacuum distillation process in which a steam jet pump is used to transfer "steam and/or uncon- .5 densed overhead products from a stripping or flash tower at high vacuum to a; fractionating tower at medium vacuum.

It is known that vapor condensers may be used to create a condition o! low absolute pres- '10 sure in a flash evaporation zone or in a stripping zone. This pressure is, however, limited by the temperature of the available cooling water. An even lower absolute pressure can be obtained by using a thermo-compressor or ysteam jet such as l5 is disclosed in the Kramer Patent 1,619,348 or in the Schulze Patents 1,488,709 and 1,934,150. It is to be noted, however, that in the process as disclosed in the Kramer patent, the steam from the thermo-compressor is dischargedvdirectly into a barometric condenser. The Schulze process is applicable, particularly, to dry vacuum distillation wherein no stripping steam is used in either a flash evaporation zone or in a stripping section. It is an object of our invention to reduce the total amount of steam required when relatively large amounts of vapors are being withdrawn by a thermo-compressor or lsteam jet pump from a ilash evaporation or stripping tower by condensing hydrocarbon vapors out oi.' the steam, reheating the condensate, and separately introducing the heated condensate and the uncondensed products toa fractionating tower maintained at a higher absolute pressure than that in the flash *or* stripping tower. p 1

It isa-further object of our invention to provide a process for obtaining a low absolute pressure inA a flash tower or stripping tower by means of a steam jet pump or thermo-compressor while utilizing the steam from the pump or compressor to's'ecure increased vaporization in a fractionating tower at a low temperature, as a result of the partial pressure effect. l

It is a further object of our invention to provide 45 a novel double flash high vacuum distillationsya 4tern for producing low penetration asphalt and a high yield of cylinder stock from an asphaltic reduced crude petroleum'oil.

Another object of our invention is' to provide 50 a double ilash high vacuum distillation system in which the asphaltic ilux bottoms from a fractionating tower maintained at high vacuum are externally heated, ashed at a higher wet or dry vacuum maintained by a thermo-compressor or 55 steam jet pump, and light overhead products are tower either with the steam from the themen=` compressor or separately as a condensate.

In the accompanying drawings which form part 10 of the instant specication and which are te he read in conjunction therewith and in which like reference numerals refer to like parts throughout the several views;

Figure 1 is a schematic drawing of a preferred .15 embodiment of ourl invention in which the 'vapors from a flash or' stripping tower are condensed and reheated before introduction to a fractionating tower and in which a thermowompreescr discharging into the fractionating tower is used 2o to maintain a low absolute pressure on the dash tower.

Figure 2 illustrates a'diagrammatic view of a modification of our invention in which 'a thermecompressor or steam jet pump is used to maintain a low absolute pressure on a flash tower and 'in which the steam and overhead products from the ilash tower are introduced to a fractions-ting tower at a higher absolute pressure.

` Figure 3 illustrates another modication of our 30 invention in which a thermo-compressor or steam jet pump is used to maintain a low absolute pressure on a stripping or flash tower, the exhaust steam and the overhead products from the strip-n ping tower being returned to the iractionating tower.

In general, our invention as disclosed in ure 1 provides a process by which a reduced crude is heated and flashed toremove the asphalt er iiux bottoms. A low absolute pressure is main 49 tained on the flash tower by means of a the compressor which serves to remove as ov t. products, the reduced crude vapors and process steam used as a stripping medium. Substantially all the hydrocarbon vapors are condensed out of the steam which is introduced with the jet steam i to a iractionating tower to function as a stripping medium. The condensate is reheated progressively by suitable heat exchangers and a tube still before being introduced to the iractionating 5o tower. By condensing the vapors from the hash zone and pumping them as a liquid into the frac tionating tower at a higher absolute pressure,

the quantity ci steam required to transfer vapors and condensate from the iiash tower to the frac 55 tionating tower is greatly reduced below that required to transfer the whole in the vapor State. 'I'he heating of the condensate which is partially due to het exchange with the vapors from the flash tower raises the temperature of the condensate to a point permitting it to vaporize sumciently in the fractionating tower to recover the overhead products.

The `iet steam from the thermo-compressor and the process steam from the ash tower when introduced to the fractionating tower operating at a.l higher absolute pressure serve to lower the par-f' tial pressure in this tower and effect vapor-ization at a lower temperature than would be necessary for a single flash system.

'I'he process is also applicable to a system for recovery of heavy cylinder stock from the ux bottoms of reduced crude subjected to fractionation. In this case, as disclosed in Figure 2, the bottoms after heating, if necessary. are dashed, the..v heavy cylinder stock vapors being taken oil.' overhead. A lower absolute pressure is maintained on the ash tower than on the fractionating tower by a thermo-compressor functioning as before. 'I'he condensate in this case may be removed directly as a heavy cylinder stock. i

under a low absolute pressure of from twenty- However, inasmuch asthe quantity of vapors taken of! overhead from the ash tower will be l much less in this case thanin the operation of Figure 1, it may be desirable'to introduce these vapors and the Jet steam directly into the iractionating tower. The condenser in such case would be bypassed.

The process as applied to Figure-3 is substantially the same as that in Figure 2 save that a side stream strippingr tower is substituted i'orrthe ash tower. The relatively low quantity lotra pors taken overhead may make bypassing ofthe condenser feasible without greatly increasing the steam consumption o! the Jet.

Referring now more particularly to Figure l. an asphaltic reduced crude, for example, is charged through a line I to a convectionsection 2 in a fumace setting 3 where the viscosity isglowered and a preliminary heating takes place. The charge from this section is transferredby means `of a line 4 to a radiant heating section l of the ,furnace where the oil is partially vaporized before being introduced through aline 3 to a ash tower 1. Vapors evolved in this towerfare taken oi! overhead v'through a line 3 which passes through a vapor heat exchanger 3 to a surface condenser I0. Cooling water is fed to thisY con denser through a line II and after circulation is removed through a line I2. A steam Jet pump I3 is connected through a line I4 with the receiver of condenserl Vand through line 3 with flash tower 1. Live steam is introduced to the jet pump I3 by means of a line I5. Steam exhausted from the pump I3 is introduced through a line I6 to the bottom of the fractionating tower I1. It -is to be understood, however, that line I8 may be connected to the fractionatlng tower either above or below the ash section or main point of charge entrance to the i'ractionating tower. The condensate from I0 is pumped from line I3 by pump I9 through heat exchangers 3 and 20 to the convection section 2| of the furnace setting 3. A line 22 connects the convection section 2| with the fractionating tower I1. A line 23 serves as a draw-off line for the bottoms from the tower 1 which pass through .the heat exchanger 2U to the cooler 24 and thence to storage. A series oi'` bubble trays 2l are-located within the tower I1. A vapor draw-oi! line 26 is connected to a condenser 21 which is provided with cooling water through a line 28. A line 30 is provided for the removal of condensate from the receiver 29. A barometric condenser 3I is connected with the receiver 29 through a line 32, a vacuum being maintained on the barometric condenser by means of the steam jet air pumps 33 connected therewith through a line 34. A line 35 connects the barometric condenser with the hot well 3B. Process steam may be introduced to the flash tower 1 and the fractionating tower I1 by means of lines 31 and 38 respectively.

In operation, oil which may be, for example, reduced asphaltic crude is heated in the convection section 2 and the radiant section 5 of the tube still 3. The heated oil and vapors from the radiant section 5 are introduced into the high vacuum ash tower 1 Where, due to the decreased pressure, further vapors are evolved-.and the asphalt or ux bottoms collected in the bottom of the tower are removed through the line 23 and passed through the cooler 24 before being sent to storage. The steam Jet pump I3, by reason of its connection to the flash vtower through the lines I4 and 8 serves to maintain this tower ve to thirty millimeters of mercury. Process steam introduced into the tower through the line 31 aids in removing the ,lighter ends from the condensate collected, which light ends pass overhead with the vapors and steam through the line 8'and the vapor heat exchanger 9 to the condenser I0. The oil vapors are condensed therein and the condensate is withdrawn through the line I8 by the pump I9 which delivers the condensate through the vapor heat exchanger 9 and the heat exchanger 2li to the convection section 2| of the tube still 3. This condensate is heated in this convection section before being 'introduced to the fractionating tower I1 through line 22. The steam and uncondensed overhead products of hash tower 1 which remain uncondensed in the condenser III are withdrawn from the receiver by the steam iet pump I3 by entrainment with the live steam introduced through the line I3. 'I'he steam exhausted from this pump is delivered directly to a selected point of the fractionating tower by the line I6. A subatmospheric pressure higher than that which exists in the flash tower is maintained in the fractionating tower I1 by means of the barometric condenser 3| and vapor condenser 21 pulling through the line 26 to the top of the fractionating tower. For example, the fractionating tower condensed in condenser 21 and separated in receiver 29, gas oil being delivered as condensate through the line 30 to storage while the steam is withdrawn and condensed by the barometric condenser 3I. It will be observed that we are enabled toA produce an asphalt of low penetration from the flash tower' with an increased yield of cylinder stock from the main tower by discharg- 'I'he oil vapors and u steam taken ofl overhead through the line 26 are.

ing the exhaust of the steam Jet pump and the.

steam from the flash tower into the bottom of the fractionating tower. By our process the temperature necessary to produce vaporization is lower than would usually be required, due to the partial pressure effect of the steam and light ends.

Referring now to Figure 2, fractionating tower I1 is connected to a flash tower 1 by means of the line 39 having a pump 40. A vapor outlet line 8 connects the vapor condenser I0` and the top of the ilash tower 1. A bypass line 8a connects the vapor line 8 with a steam jet pump I3 while the line I4 having a shut-off valve I4a connects the steam jet pump to the vapor condenser I0. A shut-01T valve I0a placed in the line 8 serves to cut the vapor condenser from the line 8 in the event that the steam jet pump I3 is desired to be directly connected to the flash tower`1. A valve 8b is placed in line 8a for a purpose which will be more fully described hereinafter. The outlet from the steam jet pump is connected to discharge into the bottom of the fractionating tower I1 by means of a line I6. Itis to be understood, however, that this is by way of example only and that this line I6 may be connected to the fractionating tower either above or below the flash point in the fractionating tower. A condensate draw-olf line I8 having a pump I9 is connected to the bottom of the receiver I 0b and serves to deliver the liquid hydrocarbons to storage. Process steam may be introduced, if desired, to the fractionating tower and ash tower by means of the lines 38 and 31 respectively. It is to be understood, however, that we contemplate operating the ash tower either under a wet or dry vacuum. A vapor draw-off line 26 is connected to the usual steam jet and barometric condenser as in Figure 1. II it is desired, a convection tube bank 4I in tube still 3 may be connected to the line 39 and so arranged that, by manipulation of the valves 42 and 43, bottoms withdrawn from the fractionating tower may be delivered to the ash tower with or without prey heating as may be desired.

In operation, the flux bottoms of the fractionating tower I1 are pumped by the pump 40 through the line 39 or 39a toA the ash tower 1 where the oil is vaporized either with or without process steam and the vapors and steam taken oil overhead through the line 8. A high vacuum of from ten to twenty-five millimeters of mercury is maintained in the ash tower as a result of the operation of the steam jet pump I3 and the vapor condenser I0. 'I'he overhead products from the flash tower comprising, for example, oil vapors 'and steam, may be delivered to the vapor condenser IU wherein oil vapors are condensed, the condensate being withdrawn through line I8 by means of pump I9 and sent to storage. The uncondensed products are entrained by the high velocity jet I5 of the steam jet pump I3. In this event, uncondensed products from the flash tower and the jet steam are delivered together through the line I8 to a selected point above or below the flash point in the fractionating tower I1. In the case of asphalt bottoms being ashed in the tower 1, any material taken overhead would probably be cooled suillciently by the steam jet pump so that it would be returned to the fractionating tower partly as a liquid. In order to prevent contamination or the bottoms in the fractionating tower, a return of the flash tower overhead condensate to a point above the point of cylinder stock draw-oil' would be advisable, instead of returning this condensate to the base of the fractionating tower. It may be desired to deliver the overhead products from the flash tower directly to the steam jet pump I3. In such case the valves Illa and I 4a would be closed and the valve 8b opened. Steam and oil vapors from the ash tower delivered to the steam jet pump I3 would be directly compressed and delivered together to the fractionating tower I1.

Referring now to Figure 3, the fractionating tower I1 is connected by means of a sidestream withdrawal line 39 to the stripping tower 1, from which a condensate withdrawal line 23 leads to storage. Stripping steam may be introduced into the stripping tower 1 by means of the line 31. The light ends and stripping steam from` this stripping tower 1 are taken olf overhead through the line 8. A condenser I0 is connected to the line 8 and to a steam `iet pump I3 by a line I4 having a valve I4a.. An auxiliary line 8a having a valve 8b connects the vapor draw-off line 8 with the steam jet pump I3. The valve Illb is provided in the connection between the condenser I8 and the line 8. A condensate withdrawal line I8 connects the condenser I0 with a selected point on the fractionating tower I1. The products ex hausted from the steam jet pump I3 may be returned to the fractionating tower through the line I9 having a valve I9a. It is to be understood however, that the location of these return lines with respect to the flash point 22 of the fractionating tower is by way of example only, it being within the contemplation of our invention to return the exhausted products to any selected point up and down the tower.`

In operation, oil is heated and introduced into the fractionating tower I1 at the point of flash 22. The vapors evol/ed rise upward through the tower forming pools of condensate on the various fractionating plates. A selected fraction is withdrawn as a side streamthrough the line 39 and introduced to the top of the stripping tower 1 wherein the light ends are stripped by steam entering through the line 31. 'I'he stripped oil is delivered to storagethrough the line 23. 'Ihe vaporized light endsand stripping steam are taken off overhead through the line 8. If separation of the oil vapors and steam is desired, the valves Ia and Haare opened and the valve 8b is closed. Oil vapors will then be condensed in the condenser I0 and delivered as a condensate through the line I8 to the fractionating tower I1 while the uncondensed products are entrained by the steam jet I5 of the pump I3 and delivered with the exhaust steam through either the line I8 or I9 to the fractionating tower I1. 'I'he point of return, of course, will depend upon the character of the side stream being stripped. It may be desirable, when the amount of overhead vapors is small, to compress the stripping steam and vapors together by means of the steam jet pump and deliver4 the products exhausted from this pump directly to the fractionating tower I1. In such a case the valves IIIa and I4a will be closed and the valve 8b opened so that the overhead products will be delivered directly to the steam jet pump without passage to the condenser. A vacuum is pulled on the main fractionating tower by means of a steam jet and barometric condenser connected to the line 26 as in Figure 1. This vacuum is less than that existing 'in the stripping section.

It will be observed that we have accomplished the objects of our invention. We have provided a high vacuum system of double flash distillation in which a thermo compressor or steam jet pump obvious that variouschages maybe made in -details within the scopel of our claims without departing from the spirito! our invention.I It is,

is used to create a high vacuum in a stripping section or ilash tower. at the same time this serves to return the stripping steam and exhaust steam jet to a. frationating' tower at a less vacuum in order thatthe partial pressure effect oi.' the steam may be utilized to cause Vaporlzatlon in the fractionating tower atlaI lower temperature than is possible with a single flash system of distillation. y It vwill be understood that certain features and suis-combinations are oi utility and may be employed without reference to other features and sub-combinations. ljhisis contemplated by and iswithin the scope oi ourl claims. `It is-further therefore, to be understood that our invention is not tobe limited to the specific details shown and described.

. Having thus described our invention, what we claim is:

1. A process for distilling hydrocarbon oils including the steps of heating a hydrocarbon oil, vaporizing lighter hydrocarbons oi the heated oil in a ash zone in the presence of steam, removing hydrocarbon vapors and steam from the flash zone and condensing the vapors from the steam and vapors in a condensing zone, removing uncondensed vapors and steam from the condensate formed in the condensing zone by entraining the vapors and steam with a high velocity steam jet in an entrainment zone whereby the condensing zone and the flash zone are subjected to a low absolute pressure, removing the condensate from the condensing zone, heating the condensate and introducing it into ai'ractionating zone having a higher absolute pressure at ythe point of ilash than that in the ilash zone and discharging the iet steam and entrained products from the entrainment zone into the fractionating zone.

2. 'I'he process of claim 1 in which the absolute pressure in the ilash zone is between twenty-live and thirty millimeters of mercury, and the absolute pressure in the fractionating zone at the point of iiash is about seventy-five millimeters of mercury.

3. A distillation process comprising the steps of introducing into a stripping zone a stream of heated oil, subjecting the heated oil therein to a sub-atmospheric pressure whereby relatively light hydrocarbons of the oil are vaporized, continuously removing a stream of vapor from said stripping zone and passing the vapor stream through a condensing zone, subjecting the vapor stream during its passage through said condensing zone to a sub-atmospheric pressure and coo1` ing the vapor whereby a vapor condensate is formed,'=entraining vapor uncondensed in said condensing zone with a high velocity steam jet to increase the pressure on said uncondensed vapor and to maintain a sub-atmosphericpressurel in said condensing zone and in said stripping zone, separately heating a stream of the vapor condensate, introducing the stream of heated condensate into a fractionating zone and subjecting said condensate therein to a sub-atmospheric pressure higher than that in said stripping zone, and eecting ya separation of said condensate in said fractionating zone into a plurality of fractions oi'- successively higher boiling points, and discharging said jet ysteamfand entrained vapor into said fractionating zone.

4. A process for separating cylinder stock and a low penetration-asphalt from .asphalt containing reduced crude petroleum oil comprising the steps of ilowing the oil through a. heating zone wherein the oil is heated and into an enlarged ilash zone wherein the heated oilis subjected to a sub-atmospheric pressure sufficiently low to vaporize a majority of hydrocarbons lower boiling than the desired asphalt product, stripping the unvaporized oil in the ilash zone with steaml to vaporize substantially the remainder ci hydrocarbons lower boiling than the desired asphalt product, removing the stripped oil from the flash zone and from the process as the desired low penetration asphalt product, separately removing a mixture of the oil vapors and the stripping steam from the ilash zone and passing the mixture without substantial change in pressure through a cooling and condensing zone wherein oil vapors are condensed out of the mixture. pumping the oil condensate through a heating zonejwherein it is heated and into a fractionating zone wherein the heated oil condensate is sub-y Jected to to a sub-atmospheric pressure which in the region where the heated oil condensate enters is higher than the pressure in said flash zone yet sumciently low as to vaporize the majority o f hydrocarbons lower boiling than the desired cylinder stock product, stripping the unvaporized oil porizing relatively low boiling hydrocarbons of the heated oil in a flash zone, separately removing unvaporized oil and oil vapors from the ilash zone and diverting the unvaporized oil from the process, cooling the removed vapors in a conl densing zone to form a vapor condensate, maintaining a sub-atmospheric pressure in the flash and condensing zones by entraining vapors un- ,condensed in said condensing zone with a steam Jet, discharging the iet steam and entrained vapors into a iractionating zone, heating the vapor condensate, introducing the heated condensate into said fractionating zonewherein the absolute pressure in the region of introduction of the heated condensate to said zone is higher than that in said flash zone and fractionati'ng the con densate in said fractionating zone.

CHARLES T. CHAVE.

n JOHN s. WALLIS.

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