US2342166A - Processing well fluids - Google Patents

Description

Feb. 22, 1944. w. B. PLUMMER 2,342,166

PROCESSING WELL FLUIDS Filed June 25. 1941 2 Shets-Sheet 1 Feb 22, 1944 w. B. PLUMMER PROCESSING WELL FLUIDS Filed June 25, 1941 2 Sheets-Sheet 2 Patented Feb. 1944 PROCESSING WELL FLUIDS William B. Plummer, Chicago, Ill., assigner to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application June z5, 1941, serial No. 399,663

1 claim. (01. 26o-essa) This invention relates to methods of hydrocarbon conversion which are particularly applicable for use in connection with wells of the so-called distillate or condensate type, although applicable also in connection with production from other types of wells when itis desired to cycle gas to repressure an underground formation. More particularly this invention relates to a combination process of distillate recovery and gas reversion.

Production from certain deep hydrocarbon reservoirs of the so-called distillate type is wholly or largely in the vapor phase although these vapors contain substantial amounts of normally liq.- uid hydrocarbons commonly including gasoline hydrocarbons and hydrocarbons boiling somewhat above the gasoline range. The existence ci' these hydrocarbons in thevapor phase in the sub-surface reservoir is due to the high pressure existing in the formation which brings about a phenomenon known as retrograde vaporlzation, whereby a hydrocarbon system which would give a liquid phase as well as a vapor phase at moderate pressures or even at atmospheric pressure exists as a single dense vapor phase in the reservoir. If gases coming from these extremely high pressure wells, e. g., at pressures of the order of 4000 pounds per square inch, are reduced in pressure to pressures of the order of 1000 to 1200 pounds per square inch, acondensate will form. In handling production from such reservoirs, the well fluids are reduced in pressure and sometimes cooled to bring about the phenomenon of retrograde condensation, whereby a large part of the normally liquid hydrocarbons and also a substantial part of three and four carbon atom hydrocarbons are thrown out in the liquid phase and separated. This liquid phase then can be stabilized or flashed at atmospheric pressures. The gases originally separated, as well as those resulting from the stabilization or flashing operation, are recycled to the underground formation from which they were produced, thereby maintaining the pressure in such formation and main'- taining or enhancing the retrograde vaporization phenomenon therein. Such procedure greatly improves the ultimate recovery from the reservoir. In some instances these gases are used for the maintenance of the pressure in or the repressuring of an underground reservoir other than that from which they originated.

It also has been proposed to recover the liquid components of high pressure well uid by a process of high pressure absorption at well head pressure or at some intermediate pressure between Well head pressure and the pressure at which the maximum recovery would be effected by pressure reduction alone.

It is an object of my invention to provide methods of improving the yield of motor fuel in connection with production from oil and gas wells and particularly with production from wells of the distillate'type-` Another object of the invention is to obtain the increased production of motor fuel without substantially diminishing the volume of gas available for recycling to the sub- -surface reservoir or for cycling to a diii'erent one.

A further object is to provide-a method for increasing the yield of motor fuel from the producing operations and simultaneously increasing the amount oi gasavailable for repressuring.

Another object of my invention is to provide a gas of improved characteristic for pressure maintenance or repressuring purposes. Another feature and object of this invention is the provision of a gas reversion process in conjunctionwith a retrograde condensation or high pressure absorption operation in which the gas reversion and distillate recovery processes are combined to accomplish results which cannot be accomplished by either process alone. More particularly it is an object of my invention to combine a distillate recovery operation and a gas reversion process using in part the same equipment for both operations.

A still further object of my invention is to provide a process wherein th.. isobutane from distillate wells may be alkylated with olens from the thermal gas reversion of the distillate. Other and more detailed objects and advantages of my invention will become apparent as the description thereof proceeds.

The production from distillate Wells normally includes a large amount of methane and lesser amounts of higher paramnic hydrocarbons. Ordinarily this includes a substantial amount of Ca, C: and C4 hydrocarbons, a substantial amount of hydrocarbons in the gasoline boiling range, i. e... up to about 400 F., and usually some still heavier hydrocarbons in varying amounts. VIn distillate recovery, whether by retrograde condensation or high pressure absorption types of process, it is customary to recycle practically all of the C1, Cz and C: hydrocarbons and a large part of the C4 hydrocarbons to the underground formation. The desirable normally liquid hydrocarbons are recovered and are not available for recycling. Therefore, because of the diminished supply of recycle gas, pressure maintenance is not ordinarily completely successful. The process of my invention. however, uses certain of these lower hydrocarbons for the production of additional amounts of hydrocarbons boiling in the motor fuel range without seriously diminishing the supply of gases available for recycling and in many instances it serves to increase the supply and Ato improve the function of the gases in the sub-surface retrograde vaporization phenomenon. Briefly this is accomplished by first separating the distillate from gases by retrograde condensation or by high pressure absorption at pressures of about 1000 pounds per square inch or more, and maintaining the gases under said pressure. 'I'hese gases are available for recycling and since at least 90 mol per cent of the gas is returned to the formation and the cost of recompression is very considerable, it is desirable and important from an economy standpoint to reduce the pressure as little as possible. I then separate the distillate into a predominantly C3 and C4 fraction, a light naphtha In the gasoline boiling range, and a heavy naphtha. The heavy naphtha and the normally gaseous Cs and C4 hydrocarbons are fed in a common stream tol a gas reversion furnace to produce a high antiknock rating naphtha of gasoline boiling range plus gases which together with unused gas from the initial high pressure separation step are recycled to the formation. Likewise, all or a part of the total distillate can be fed to a gas reversion furnace.

My invention will be described further with particular reference to the accompanying drawings which show in Figures 1 and 2, respectively,

two alternative flow diagrams illustrating my inventlon. These drawings form a part of this specification and in them like reference numerals indicate like or corresponding parts.

Referring now to Figure l: A producing well I0 furnishes well iluids from a sub=surface reservoir which is normally a deepthigh pressure reservoir of the distillate type. A single well is shown but of course it will be apparent that the production from any number of such producing wells can be combined and that normally my process will operate on the combined production from a group of such producing wells. The well i'luids pass through valveII and then through line I2. cooler I3 and pressure reduction valve I4 to separator I5 The cooler and pressure reduction valve are controlled to give a temperature and pressure in the separator I5 which may be varied within considerable limits depending on the desired operation and particular character of the well finish. However, they are such as to give a substantial recovery of liquid hydrocarbons by means of the retrograde condensation phenomenon. The pressure in separator I5 normally will be between 800 pounds per square inch and 3000 pounds per square inch, and is chosen on an economic basis, i. e., pressure should be as high as possible in order to reduce the cost of recompressing the gases. On the other hand, a lower pressure within the retrograde condensation range permits the separation of a larger amount of the liquid phase. The lower limit of the retrograde condensation range varies with the composition of the particular well fluids and in most cases the pressure in separator I5 should be above about 1000 pounds per square inch.

Recovery of liquids in separator I5 is better at lower temperatures but the temperature used is dependent upon the economic factor involving the cost of cooling and the cost of eliminating hydrate diiculties. 'I'he apparatus can be operated at temperatures of from -25 F. to +125 F.

but ordinarily it is operated in the temperature range of 0 F. to '15 F.

Gas phase formed in the retrograde condensation separator I6 is predominantly methane but also includes ethane and minor amounts of heavier hydrocarbons. This gas phase passes through line I6 and through absorber I'I where it is contacted with recycle oil from the gas reversion operation, supplemented if desired by extraneous naphtha or the heavy portion of the distillate. The rich oil from the absorber I1 passes by lines I8 and I9 to gas reversion furnace 20. The gas phase from absorber I1 passes through line 2| andcompressor 22 and thence through line 23 and valve 24 to one or more input wells 25, through which it is recycled to the underground formation from which production was effected through well I0. Alternatively, it may be cycled to a diil'erent sub-surface reservoir for pressure maintenance or repressuring purposes. v

The liquid phase formed in separator I5 includes not only a maior part' of the normally liquid hydrocarbons present in the well fluids but also includes substantial amounts of normally gaseous hydrocarbons particularly C: and C4 vparaiilnic hydrocarbons. This liquid phase is excellent feed for the gas reversion process and can be sent by line I9 to furnace 20 and subjected to gas reversion under high pressure. However, when desired, the liquid phase can be passed from separator I5 to high pressure fractionator 21 by valved line 26. From the fractionator 2'I a light naphtha cut comprising normal butane can be withdrawn through valved line 28 and passed to blended product tank 29. The liquid product in tank 29 includes the gasoline produced both by the distillate recovery step and the gas reversion step. A heavy naphtha can be withdrawn from fractionator 2'I by line 30 and passed by pump 3I and line 32 to absorber I1 as absorber oil or withdrawn from the system by valved line 33. Auxiliary absorber oil can be furnished to the process by valved line 34 and pump 35. v

Overhead from fractionator 21 passes through partial condenser 36 to separator 31 from which gas can be taken oiI through compressor 38. These off gases can be sent by valved line 39 and line I9 to the gas reversion furnace. Alternatively all or a portion of the gases can be returned to the high pressure gas line 2| by valved line 40 and thence to the input well 25. Alternatively these gases can be returned to absorber I1 by valved line 4I and line I6 The rliquids from this separator 31 are withdrawn by means of pump 42 and a portion of them is returned to the top of the fractionator 21 through valved line 43 to serve as reflux. Another portion of the liquid fraction can be sent via valved line 44 to form part of the feed to gas reversion furnace 20. Preferably, however, it can be passed by valved line v45 to' depropanizer 46. The liquid isobutane is withdrawn from tower 46 and pumped through line 41 to alkylation reactor 48 and processed as described below. 'I'he propane and other gases-removed overhead from tower 46 by line 49 are liquefied and pumped or compressed and sent by line 39 to the gas reversion furnace 20.

All or a part of the total distillate or the combined stream of hydrocarbons including the rich absorber oil, C3 and C4 hydrocarbons, and fixed gases from the distillate recovery and/or gas .reversion can be passed through line, I8,

heat exchangers 58 and 5| to gas reversion furnace 28 for conversion into the normally. liquid hydrocarbons, particularly gasoline range hydrocarbons.

Referring to the 'gas reversion step in more detail, the hydrocarbons entering the furnace are preheated by means of heat exchangers 50 and 5I and then passed by any'desired routing through the coils lof` the gas reversion furnace. 'I'he gas reversion step is carried out at a temperature of from about 900 to about 1100 F., for example 975 F., and at a pressure of between 100 and 3000 pounds per square inch, for example 1500 pounds per square inch. It ispreferred t`o voperate the gas reversion furnace at a high pressure,

preferably at least 1000 pounds per square inch.

The hot products from the gas reversion furnace 20 pass by transfer line 52 to -the)heat exchangers and 58 where it serves to preheat the incoming hydrocarbons. If desired these hot reversion products can be quenched by the introduction of quench oil at 53. The high pressure separation of the lighter fixed gases can be madeimmediately following the thermal gas reversion process before or after tar separation. Thus hydrogen, methane, and more or less ethane, can be separated at a pressure of between about '150 and 1500 pounds per square inch, compressed and recycled to the formation.

The'gas reversion products pass by linel 52 into tar separator 54. The tar is withdrawn from the system by valved line 55. The overhead from tar separator 54 is passed by line 56, cooler 51, heat exchanger 51a, and line 58 to high pressure separator 59. This separator can be operated at a pressure of' between about 800 and about 3000 pounds per square inch. The temperature ordinarily will be below about 200 F. The recovered gas reversion products are withdrawn from the base of high pressure separator 59 in the liquid phase and passed by line 68 to stabilizer 6| which can be provided with reboiler 62. The high pressure gases from separator 59 can be taken by line 83 to high pressure line 2l and passed to input well 25.

The liquid prod ct from stabilizer 5| is passed by line 63 throug rerun tower 64 to produce a gasoline end point naphtha overhead which is withdrawn through line 65 and partial condenser 66 to separator 61. The liquid phase can be sent in part through pump 68, valved line 69 to the top of the rerun tower 64 as reflux, and in part through valved line 10 to the product storage tank 29. -Any gases accumulatedin separator 61 can be vented .through valved line 1I. A kerosene-gas oil cut is obtained as a bottoms which either may be withdrawn from the system by valved line 12 or returned as absorber oil to the absorber I1 by pump 13 and line 14, thus ultimately being recycled to the gas reversion step. If desired, this liquid product may have a comparatively low initial boiling point thereby containing the heavy portions of what is normally considered gasoline, thus producing through line 18 a light, very high octane number gas-converted product.

Gases from the stabilizer 6| are taken oil throughline 15 and partial condenser 16 to separator 11. by pump 18 and valved line 19 to the top vof stabilizer 6| as reflux or by valved lines 88, 8l,

' and 41 to alkylation reactor 48. -Another portion can be routed through valved line 82 and line The liquid phase .can be sent in part i8 to the gas reversion furnace 20. In the preferred embodiment, however, the oleflns contained in the liquid phase withdrawn from sepu arat'or 11 are alkylated with the isobutane recovered from the well distillate. Trapout 84 is provided to recover from stabilizer 6| a propanepropylene cut with some C2 and C4 hydrocarbons which are sent by line 8l to alkylation reactor 48. The gas'phase from separator 11 passes by compressor 18,in line 19 to high pressure gas line 2| and thence to the input well 25. Likewise, the gases leaving compressor 18 can be introduced into lines 19a and 4I and thence absorber |-1 by linel6.

Referringfmore in ldetail to` the alkylation process, the olefins via, line 8| and the isobutane fraction recovered from depropanizer 46 are'passed to alkylation reactor 48.

The reactor 48 can be of any type in which intimate contacting of the feed wtih the catalyst is accomplished.

Concentrated sulfuric acid containing between about 93% and about 101.5% HzSO4 and preferably about 9697% HaSO4 at temperatures of between about 15 F. and about 95 F. and preferably at about 65 F. is a particularly effective catalyst for the alkylatlon of paraflins with olefins. According to my process the isobutane Ipresent in line 41 is alkylated with olefins of 3 and 4 carbon atoms using as a catalyst sulfuric acid of the above concentration under the above bonditions.

The emulsied hydrocarbon-acid mixture from reactor 48 is directed to separator 86 through line 85. In separator 86 suflicient additional contact between the catalyst and the feed stock is accomplished to obtain additional alkylation. The emulsion in separator 86 breaks, the alkymer and unreacted gases passing overhead through line 81 andthe separated acid being withdrawn through line 88. This acidv can be recycled to reactor` 48 through line 89 or withdrawn, or a portion of it can be recycled and a portion of it continuously withdrawn for regeneration.

A portion of the lkymer and unreacted hydrocarbons can be recycled to reactor 48 from line c 81 through valved line 90. It is desirable to neutralize or Wash the reaction products before introducing into a fracticnator to'prevent acid, SO2, etc., from carrying. over. To accomplish this washing tower 9| can be provided wherein the product from line 81 is contacted with water or dilute caustic, or both. The product is then cooled in cooler 93 and passed by line 92 to fractionator 21. In fractionator 21 an alkymer of gasoline boiling range is separated and withdrawn through line 28 by which it can be directed ,to blending tank 29 or Withdrawn for separate use through valved line 94. Any hydrocarbons heavier than gasoline are Withdrawn ,through line 30 and rejected from the system by valved line 33 or sent by lines 3| and 32 as absorber oil in tower I1. Unconverted gases pass overhead from fractionator 21, partial condenser 36 and separator 31.

While the simple flow diagram and arrangement of apparatus shown in Figure 1 is advantageous in many respects it is also desirable in some instances to use more extensive processing and equipment. This is particularly true where large production is available and where the characteristics of the formation and well uids are such that the production of the well or wells declines only very slowly so that a high capital investment is Justied in obtaining increased efilciencyb Figure 2 illustrates some of these possibmtiesi Referring to Figure 2 in more detail the production from one or more producing Wells which* are preferably of the distillate type passes through line cooler ||2 and pressure reduction valve' ||3 to separator absorber 4, which. if valves 5 Yand ||6 are closed and no absorber oil is introduced, operates as a retrograde condensation separator similar to thatshown in Figure 1. One difference, however, is thatFigure 2 shows the use of an antifreeze system as one method of preventing natural gas hydrate trouble. A liquid or gas antifreeze material, for example calcium chloride brine, can be circulated with the well fluids through'- pressure reduction valve III and this serves to prevent the formation of natural gas hydrates. In the case of liquid antifreeze material the antifreeze separates at the bottom of vessel ||4 and is'withdrawn by valved line under control of float ||8 which floats at the interface between the antifreeze and the hydrocarbons. The antifreeze is withdrawn to a regeneration, storage and recycling system ||9 from which it goes back into the line either preceding or following cooler I2. In Figure 2 the regenerated antifreeze is returned by valved line |20 between cooler ||2 andV pressure reduction valve ||3.

It will be understood, however, that some of these apparatus arrangements may be omitted depending upon the character of the well uids and the character of the subsequent operations. thus for example, if the well fluids are available at moderate pressures, for instance, 1500 to 3000 pounds per square inch, a pressure reduction ordinarily will not be needed and is not desirable. If the product is very low in water content or if the absorber ||4 is operated at a temperature above that at which hydrates form under the particular conditions involved, the antifreeze step can be omitted. An alter-native method of avoiding the natural gas' hydrates is to dry the well fluids by passing them through a drier. calcium chloride for example. In such an operation it is desirable to have'two or more drying chambers with one on stream while the second is regenerated.

The well fluids enter a high pressure separatorabsorber ||4 and the gases, chiey methane, pass from the separator into line |2| and compressor |22, shown controlled by the pressure in line |2|, through line |23 and valve |24 to one or more input wells |25. The liquid hydrocarbons are withdrawn from vessl ||4 through valved line |25 to surge tank |21.. The now of distillate uid from vessel ||4 is controlled by the depth of the liquid hydrocarbons within the separator-absorber and float control valve |28 can be provided for this purpose. Thesurge drum can be operated at about the same pressure as separator ||4. Thus for instance the retrograde condensation separator-absorber ||4 can be operated at about 1500 pounds per square inch and the surge drum |2'| operated at about 1200 pounds per square inch.

The liquid from surge drum |21 can be passed by valved lines |29, |30 and |3| to high pressure gas reversion furnace |32. Likewise, all or a portion of the liquid product withdrawn from the separator-absorber ||4 can be passed through pressure reduction valve |33 and one of valved lines |34 into stabilizer |35. Before entering the stabilizer all or a part of the liquid can be passed in heat exchange with the stabilized product by wholly or partially closing valve |36 and opening butane are removed and the stabilizer is operated' at such pressure. top temperature and reflux ratio as to eliminate part of the gaseous hydrocarbons as are not desired in the finished motor fuel. Reflux can be furnished by passing the overhead from stabilizer |35 through a partial condenser |39 to a separator |40 from which a part of the liquid phase can be pumped by means of pump |4| through valved line |42 back into the top of stabilizer |35. When desired reboiler |43 can be provided near the base of stabilizer |35.

The liquid product from tower |35 includes one' source of the liquid feed to the gas reversion process. It is withdrawn through heat exchanger |38 and valved line |44 to rerun tower |45 which is provided with a dephlegmating coil |45 and reboiler |41. Stabilized gasoline of a desired end point is taken off overhead through line |43, passed through cooler |49 and by line |50 ultimately is carried to blended product storage |5|. However, intermediate storage |52 and light naphtha draw-oir |53 can be provided. The heavy distillate withdrawn from the bottom of rerun tower |45 constitutes the main liquid stream to the gas reversion furnace |32. However, extraneous naphtha can be introduced to the system by valved line |54, for example.. When desired a portionof the heavy naphtha withdrawn from rerun tower |45 by line |55 can be sent via valved lines |56 and |51 to the high pressure absorber ||4 as an absorber oil. When the vessel ||4 is operated merely as a retrograde condensation separator, substantially all of the recycle gasV oil and heavy naphtha is pumped to the gas reversion furnace |32 by valved lines |58 and |3|.

Overhead from fractionator |35 passes through partial condenser |39 to separator |40 from which gas can be taken oli.' through valvedline |59. These off-gases can be sent by valved line |59a to the gas reversion furnace as charging stock or by valved line |59b as fuel in the furnace. Alternatively, all or a portion of the gases can be returned to the high pressure gas line 2|. The liquids from separator |40 are withdrawn by means of pump |4| and a portion of them is returned to the top of the fractionator |35 through valved line |42 to serve as reflux. Another portion of the liquid fraction can be sent to form part of the liquid feed to the gas reversion furnace. Preferably, however, it can be passed by valved line |60 to depropanizer |5|. The liquid isobutane is withdrawn from the depropanizing tower |8| and pumped through line |62 to alkylation reactor |83 and processed as described hereinbelow. The propane and other gases removed overhead from tower |5| by line |64 are compressed and sent by line |55 to the gas reversion furnace |32.

Referring to the gas reversion step in more pounds per square inch, for example 1500 pounds per s quare inch.

The hot products from the gas reversion furnacel82 pass by transfer line |61 to the heat exchangers |66 where they serve to preheat the incoming hydrocarbon stream, or, if desired, these hot gas reversion products can be quenched. The high pressure separation of the lighter fixed gases can be made immediately following the thermal gas reversion process either before or after tar separation. Thus hydrogen, methane and more or less ethane can be separated at a pressure of between about 750 and 1500 pounds per square inch, compressed and recycled to the formation.

In the embodiment illustrated in Figure 2 the gas reversion products pass by line |61 into tar separator |68. The tar is withdrawn from the system by valved line |69. The overhead from tar separator |68 is passed by line |10 to a cooler |1|, heat exchanger |12, and by line |13 to the high pressure separator |14. The heat exchange medium in exchanger |12 can be the cold distillate withdrawn from vessel I I4. The high pressure separator following the gas reversion process can be operated at xa pressure of between about 800 and about 3000 pounds per square inch. which is substantially the pressure at the outlet of the gas reversion furnace. The temperature ordinarily will be below `about 200 F.

The recovered gas reversion products are withdrawn from the base of high pressure separator |14 in the liquid phase and passed by line |15 to fractionator |16 and ultimately to stabilizer |11. The feed from the high pressure separator to the fractionator can be passed in heat exchange with the bottoms from the stabilizer |11 if desired.

Ordinarily the fractionator |16 is operated in such fashion that a liquid phase is removed as bottoms, which can be used as liquid feed to the gas reversion step, and a gas phase is taken overhead to stabilizer |11. Fractionator |16 can be supplied with dephlegmating coil |18 and a reboiler |19. The overhead from this fractionator |16 passes into stabilizer |11 via line |88 and one of the alternative valved lines |8|. The motor fuel fraction can be withdrawn from the stabilizer |11 by valved line |82 and passed to storage through cooler |83 which can be an exchanger online |16. The overhead from stabilizer |11 passes through line |84 and partial condenser |85 to separator |86. A portion of the liquid phase from this separator can be passed by pump |81 through valved line |88 to serve as reux in stabilizer |11. The remainder of the liquid phase can be recycled through valved line |89 and line |65' to the coils of the gas reversion furnace |32. which cannot be condensed by condenser |85 and Those materials appear as the gas phase in separator |86 can be used as fuel, can be compressed and recycled to the high pressure gas reversion process, or can be compressed and recycled to the high pressure gas line |2|. Thus it can be passed through valved line |90, compressor` |9|, valved line |92, etc., to the coils of the gas reversion furnace |32, or through valved line |93 to burner |94 or fuel gas storage |96, and/or it may be passed through valved line |96, compressor |91, etc., to one or more input wells |25. In many instances it will be possible to eliminate part of the compressors illustrated, since ordinarily it will. not be desired to use all of the possible alternative arrangements as shown.

Reverting now to the bottoms from fractionator |16, these contain gasoline range hydrocarbons and unconverted gas oil, and can, if desired, be passed in heat exchange with the recycle gas oil withdrawn from bubble tower |98 by closing valve |99 and opening valves 200. This bubble tower |98' is conventionally equipped with dephlegmating means 20| and reboiler 202. It is so operated as to eliminate a heavier-than-gasoline bottoms and a gasoline overhead. The latter is passed to condenser 204 and by line 205 to blended storage tank |5| while the bottoms pass through heat exchanger 203 and are recycled to gas reversion furnace |32 by valved line 206 and line |58, or withdrawn as a kerosene cut byvalved line 201, or passed through cooler 208 and by line |61 to be used as absorber oil in vessel II4. The gasoline fraction recovered from bubble tower |98 can be blended with the products in storage tank |51 -or may be withdrawn by valved line 209 for further treatment or use.

Referring more in detail to the alkylation process, the oleiins via line 2 0 and the isobutane fraction recovered from depropanizer |6| are passed to alkylation :reactor |63. A trapout 2|| is pro,` vided to recover from stabilizer |11 a propanepropylene cut with some Ca and C4 hydrocarbons "p which are sent by lines 2|2 and 2|0 to the alkylation reactor |63. Alternatively these hydrocarbons can be obtained by valved line `2|3 from separator |86. The reactor |83 can be of any type in which intimate contacting of `,the fee with the catalyst is accomplished.

VConcentrated sulfuric acid containing between about 93% and about 101.5% H2504 and preferably about 969'1% H2SO4 at temperatures of between about 15 F. and about 95 F. and preferably at about 65 F. is a particularly effective catalyst for the alkylation of paraffns with olens, According to my process the isobutane introduced by line |62 is alkylated with olens of 3 and 4 carbon atoms using as a catalyst sulfuric acid of the above concentration under the above conditions.

The emulsied hydrocarbon-acid mixture from reactor |63 is directed to separator 2|4 through line 2|5. Inseparator 2|4 sufficient additional contact between the catalyst and the feed stock is accomplished to obtain additional alkylation. The emulsion in separator 2 4 breaks, the alkymer and unreacted gases passing overhead through line 2|6, the separated acid being withdrawn through line 2|1. This acid can be recycled to reactor |83 through line 2|8 or withdrawn, or a portion of it can be recycled and a portion of it continuously withdrawn for regeneration. A portibn of the alky'mer and unreacted hydrocarbons can be recycled to reactor |63.

It is desirable to neutralize or wash the reaction products before introducing into a fractionator to prevent acid, SO2, etc., from carrying over. To accomplish this washing tower 2|9 can be provided wherein the product from line 2 I6 is contacted with water or dilute caustic. The product is then cooled in cooler 220 and passed by line 22| to fractionator |35. In fractionator |35 an alkymer of gasoline boiling range is separated and withdrawn through line |44 by which it can be directed to rerun tower |45. Any hydrocarbons heavier than gasoline are separated in the rerun tower and rejected from the system by valved line222 or carried by lines |56 and |51 as absorber oil in tower ||4, or passed to the gas reversion furnace by lines |58 and |3|.

Although I have described a system wherein the same tractionating toweris used on the rei covered distillate and the alkylation product, it is also contemplated that separate iractionating systems can be used.

Vessel Il when operated as an absorber usually can be operated at a somewhat higher pressure and, if desired, at a slightly higher temperature than when used as a retrograde condensation separator. Thus as an absorber its pressure may range from 1000 pounds per square inch to 4000 pounds per square inch, usually from about 1200 to 3000 pounds per square inch, for example 2000 pounds per square inch. The absorber oil in any kdesired ratio, for example 2 gallons to 6 gallons per thousand cubic feet of gas, can be introduced above baiiles 223, or part"`of it or even all of it passed through cooler I2 into the absorber along with the well uids. The absorber oil, comprising heavy distillate bottoms from rerun tower |45, recycle gas oil from bubble tower |98, or a mixture of heavy distillate and recycle gas oil, is removed from vessel ||4 along with the distillate l hydrocarbons and nds its way through surge drum |21, stabilizer |35, and rerun tower |45.

It will be understood, of course, that the various ilow diagrams presented are merely illustrative oi. some oi the possibilities and that other alternatives will occur to those skilled in the art in the light of this description and that my invention is not restricted to the details shown. On the other hand, it will also be understood that these flow diagrams are simplied for purposes or convenience and that various items of pumping and compressing equipment, insulation, control devices, sai'ety equipment and various other details are not indicated.

'I'his is a continuation-impart oi my application Serial No. 353,633, entitled "Processing well fluids, illed August 22, 1940.

I claim:

A method of recovering distillate hydrocarbons.

from high pressure well iluids and for the pro duction of increased amounts of motor fuel hydrocarbons from said well fluids which comprises separating from said well fluids at pressures within the retrograde condensation a liquid fraction, subjecting the total liquid fraction to a iractionation in the presence oi an alkylate derived from the source deiined below, recovering an isobutane fraction, a propane fraction, a. gasoline fraction and a residual liquid fraction. subjecting the residual liquid fraction and said propane fraction to a thermal conversion, separating a gas rich in C2-C4 oleiins from the gaseous products of the conversion step, alkylating said isobutane fraction with said Cz-C4 loleiins to form hydrocarbons in the gasoline boiling range, fractionating the total alkylate with said liquid fraction, and recovering a combined alkymer and Well fluid fraction oi gasoline boiling range.

WILLIAM B. PLUMMER.

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