US2296992A - Separating hydrocarbon fluids - Google Patents

Description

Sept. 29, 1942. *ww W, GARY SEPARATING HYDROCARBON FLUID Filed July 21,` 1939 Aw, Y

R Y E. o VW` mf fm M J 9 A .l/ NSQ n Patented Sept. 29, 1942 SEPARATING HYDROCARBON FLUIDS Wright W. Gary, Manhasset, N. Y., assignor to The M. W. Kellogg Company, New York, N. Y., a corporation of Delaware Application July 21, 1939, Serial No. 285,654

2 Claims.

This invention relates to the treatment' of hydrocarbon fluids and more particularly relates to the stabilization of crude hydrocarbon oil and recovery of valuable light hydrocarbon constituents naturally occurring in crude' hydrocarbon oil.

Crude petroleum oil as it is taken from the ground normally contains appreciable quantities of methane, ethane, propane and butane'which impart to it a relatively high vapor pressure. Reneries are usually located at large distances from the oil wells and it is necessary to transport the crude petroleum oil to the reneries. To transport the crude oil coming from the well it is iirst pumped into storage tanks and then may be transferred to and from holds of tankers, or it may be pumped through pipe lines to a renery and again introduced into storage tanks. While standing in storage tanks and during transfer to and removal from the tanker holds, the light hydrocarbons evaporate from the crudeV oil and carry off valuable hydrocarbons from the crude oil which are lost from the crude oil.

Since the vapor pressure of methane and ethane is highest of the constituents in the crude oil,l these hydrocarbons have the greatest tendency to evaporate and in such evaporation these light gases take with them appreciable quantities of propane and butane and smaller quantities'of higher hydrocarbons within the gasoline boiling range. In this way valuable constituents are lost from the crude oil by evaporation. While these losses are relatively small on a percentage basis, the loss of the valuable constituents becomes appreciable when it is considered that large amounts of crude oil are transported from oil fields and treated in refineries.

The stabilization of the crude Voil according to my invention is done in the oil field in the vicinity of the oil `well or wells, The crude oil is stabilized and prepared for transportation over long distances to refineries and at the same time valuable light hydrocarbons are recovered from the crude oil. By stabilizing the crude oil in the eld, my invention has other advantages. In the oil field there are large amounts of oil well sepa rator gas or natural gas and while normally it is not profitable to transport such gas to the reiineries for recovery of valuable constituents therefrom, it is protable to absorb valuable constituents from the oil Well separator gas in the field by using my invention. The oil well separator gas or natural gas is treated with the crude petroleum oil coming from the wel] in an absorber zone or the like to absorb desired constituents from the natural gas in the crude oil and to produce an enriched crude petroleum oil. The unabsorbed gases are discarded. The enriched crude oil is then passed to a stabilizing zone wherein it is heated and fractionated under superatmospheric pressure to remove light gaseous hydrocarbons containing Valuable hydrocarbons and to recover a stabilized crude oil which may be transported to refineries without losing valuable constituents from the crude oil in the transportation.

During stabilization the gases which pass overhead are cooled and some of the heavier constituents thereof, such as Cs and C4 hydrocarbons, are liquefied and may be passed to a e011-, version zone, such as a polymerization zone, in the vicinity of the oil well or wells to produce normally liquid hydrocarbons containing gasoline constituents. 'Ihe uncondensed and unliqueed gases contain relatively large percentages of methane and ethane but also contain appreciable amounts of propane and butane. To recover propane and butane, lthe unliquefied gases are returned to the absorber zone for further absorption treatment with the crude petro-y leum oil. If desired, a portion of the stabilized crude petroleum oil may be separately introduced into the absorber zone or may be introduced along with the unstabilized crude oil as an absorbent liquid. However, only unstabilized crude.

petroleum oil may be used in the absorber. Also some of the unstabilized crude rectly introduced into the stabilizer zone to stabilize a portion of the crude oil and to recover valuable lighthydrocarbon constituents therefrom.

In the drawing the gure represents a diagrammatic showing of apparatus adapted to be used in carrying out my invention.

Referring now to the drawing the reference character l designates a line through which unstabilized crude petroleum oil taken from the well or from a storage tank adjacent the well is passed by means of pump I2. A portion of the unstabilized crude oil is passed through line I4 and introduced into the upper portion of an absorber tower I6 as absorbent liquid. Or the unstabilized crude may be passed through line I1 and introduced into an intermediate portion of the absorber tower l5. Another portion ofthe unstabilized crude oil may be passed through line i8 and introduced into a stabilizer 20 Wherein the unstabilized crude is fractionated and stabilized by removing volatile constituents therefrom.

oil may be di-V The stabilized crude petroleum oil, having been freed of substantially all the C4 and lighter hydrocarbons, is withdrawn from the bottom of the stabilizer 2li through line 22 and passed through cooler 23 to cool the stabilized crude and a portion thereof may be passed through line 24 by pump 2S and introduced into the upper portion of the absorbed tower I' as a part of the absorbent liquid in tower I'. Where part of the stabilized crude is returned to the absorber tower I6 to act as absorbent liquid, it is preferably introduced into the top or upper portion of the tower and above the point'of introduction of the unstabilizcd crude to absorb butane which may have been vaporized from the unstabilized crude in the tower. lThe rest of the stabilized crude oil may be withdrawn from the system through line 29 and transported to a renery for further treatment.

In oil elds there are large amounts of oilivell separator gas or natural gas which are allowed to pass into the atmosphere and lost or the gas is burned. As my stabilization process is carried out in the vicinity of oil wells in an oil eId, I am enabled to treat the natural gasV from the Wells in the absorber tower i6 for the recovery of valuable hydrocarbons. It is well .known that natural gas contains light normally gaseous hydrocarbons, such as methane and ethano, higher molecular weight hydrocarbons within the gasoline boiling range and also contains hydrocarbon constituents which may be used in a conversion zone, such as a polymerization zone, to produce normally liquid hydrocarbons containing gasoline constituents. rIhe natural gas which is to be treated is passed through line 30 and introduced into the lower portion of the absorber tower I6 wherein it is directly contacted with crude oilused as absorbent liquid and the crude oil absorbs the valuable hydrocarbon constituents, such as propane and higher hydrocarbons, from the natural gas. The absorber tower is provided with spaced horizontally extending plates or trays 34 to provide intimate contact between the crude oil and the gas. While I have shown this form of absorber tower, it is to be understood that other forms of absorbers such as packed towers for example may be used.

f desired, the crude oil used as absorbent liquid may be cooled before being introduced into the absorber I6 or intercoolers may be used in connection with the absorber tower i5. During absorption the absorbent liquid becomes heated and as a cool or cold absorbent liquid will absorb more gas than a warm absorbent liquid, cooling of the kind above described may be used.

The absorber tower I5 may be operated under a pressure of about 150 to 450 lbs. per square inch depending on the compositions of the crude oil and natural gas being introduced into the absorber tower. If the natural gas is available at a pressure lower than that which exist-s in the absorber tower, a pump or compressor may be provided in line 36 to raise the pressure on the natural gas. The unstabilized crude cil and the stabilized crude oil, ii it is introduced into the absorber tower I6, are intimately contacted with the natural gas in the absorber tower i6 and absorb large quantities of C3 and C4 andhigher hydrocarbons from the natural gas. The unabsorbed gases leave the top of absorber tower I6 through line 38 and may be passed to the atmosphere and discarded or may be otherwise as desired, as for fuel, for example. The unabsorbed gases contain a relatively large perstabilizer is provided with spaced horizontally extending plates or trays 44. The liquid in the bottom of the stabilizer is heated by means of a coil 48 which may be heated by steam or in any other suitable manner in order to strip light 'hydrocarbons from the crude. The stabilizer is operated under a pressure of about 300 lbs. per square inch and the bottom temperature of the stabilizer is about 550 F. The temperature and pressure may be varied, if desired.

The enriched crude oil, together with unstabilized crude which may be added to the stabilizer` zone 20 through line I8 as above described, is fractionated and stabilized in the stabilizer 2B to remove light undesired normally gaseous hydrocarbons containing methane and ethane. These light constituents carry over higher molecular hydrocarbons with them and it is desirable to remove the valuable higher molecular weight hydrocarbons from the gases. The gases and vapors resulting from the fractionation pass overhead from stabilizer 20 through line 52 and are cooled by passing through condenser 54. During this cooling some of the higher molecular weight hydrocarbons which have been carried over with the lighter gases are liquefied and condensed and the liqueed and condensed constituents are separated from gases in the separator 56. The liqueed constituents contain mostly C3 and C4 hydrocarbons, and if desired C2 hydroycarbons, which may be further treated in a conversion zone, such as a polymerization zone, to produce normally liquid hydrocarbons. Such a polymerization zone would preferably be located adjacent the stabilizer and the C3 and C4 hydrocarbons would be converted in the oil field to liquids containing gasoline constituents.

The uncondensed gases pass overhead from the separator 56 through line 58 and are introduced into the lower portion of the absorber tower I5. These gases carry over valuable higher molecular weight hydrocarbon constituents and by treating the gases in the absorber tower le, the valuable hydrocarbon constituents are recovered therefrom by the crude oils which act as absorbente. The liqueed constituents in separator 56 are withdrawn Athrough line Si! and a portion thereof passed through line 62 by pump eli and introduced into the upper portion of the stabilizer 20 as reflux. The rest of the liqueed gases are withdrawn from the system through line 66 and preferably passed through line 66 by pump 61 to a polymerization zone 68 in a heater 10 wherein the gases are maintained under suitable temperature and pressure conditions to eiect the desired conversion thereof into higher boiling hydrocarbons containing gasoline constituents.

For example, the liquefied normally gaseous hydrocarbons may be heated to a temperature of about 750 F. to 1300 F. while under a pressure of about 400 to 3000 lbs. per square inch to effect polymerization of the normally gaseous hydrocarbons into normally liquid hydrocarbons. If a predominantly aromatic liquid product is desired, higher temperatures and `lower pressures with a shorter period of reaction time may be used. In the latter case the temperature is about 1200 F. to 1'150 F. and the pressure ranges from about atmospheric to about 200 lbs. per square inch.

'I'he products of conversion leave the polymerization zone 68 through line 14 and are introduced into a fractionating tower 16 to separate heavy polymers higher boiling than gasoline, a motor fuel fraction containing gasoline constituents and gases. The heavy polymers are withdrawn from the bottom of the tower 16 through line 18 and are passed through a cooler 80 and the cooled heavy polymers are then preferably passed through line 82 for admiXture with the stabilized crude oil passing through line 29. If desired, a portion of the heavy polymers may be withdrawn from the system through line 84.

The motor fuel containing gasoline constituents collects on a trapout tray 90 in the tower 16 and is withdrawn from the trapout tray through line 88. The motor fuel is a premium one having a high anti-knock value and may be used for blending with other gasolines or may be used as such. The recovered motor fuel may be transferred to suitable containers such as drums or the like. The light gases leave the top of the tower 16 through line 92 and may be either returned to the line 66 for recycling through the polymerization zone 68 or the light gases may be introduced into the lower portion of the absorber I6 wherein valuable constituents are recovered from the light gases by the absorbent liquid used in the absorber I6. Suitable reflux is provided for fractionating zone or tower 16.

In the stabilizer 20 the enriched crude oil, and the unstabilized crude oil, if it is introduced into the stabilizer, are fractionated and the light normally gaseous constituents such as methane and ethane are mostly removed therefrom. When using unstabilized crude as absorbent liquid, about 90% of the butane and 60% of the propane in the unstabilized crude oil and the natural gas are recovered as a liquid product and are withdrawn through line 66. Where a larger recovery of propane and butane is desired, stabilized crude is preferably introduced into tower I6 through line 24 at a point above the point of introduction of the unstabilized crude through line I1, and the stabilized crude absorbs butane vaporized from the unstabilized crude in the tower I6. Further down in the tower I6 where the unstabilized crude oil is introduced through line l1, the two crudes are mixed and the admixed stream acts as absorbent liquid for the rest of the absorber tower I6.

The stabilized crude oil withdrawn through line 29 has a much lower vapor pressure than the unstabilized crude oil and may be transported from the eld to refineries without the loss of any large amounts of valuable hydrocarbon constituents.

The cool liqueed hydrocarbons before being passed to the heating zone 68 may be preheated by being indirectly contacted with hot stabilized crude being withdrawn from stabilizer 2B through line 22 and in this way cooling of the hot stabilized crude is assisted. The preheated hydrocarbons are then further heated in conversion zone 68 as above described.

While I have shown one form of apparatus and have disclosed one form of a complete process according to my invention it is to be understood that these are by way of example only and various changes and modifications may be made without digressing from the spirit of my invention.

I claim:

1. A process for the separatio-n of light hydrocarbons including methane and ethane from a Crude petroleum oil and the recovery of desired hydrocarbons from said separated light hydrocarbons and from a hydrocarbon gas mixture which comprises introducing unstabilized crude oil into an absorber, introducing gaseous hydrocarbons into said absorber and contacting them therein with the unstabilized crude oil to absorb higher molecular weight hydrocarbons in the crude oil, withdrawing crude oil enriched with absorbed constituents from said absorber and passing it to a stabilizer to vapo-rize and remove said absorbed constituents and other light hydrocarbons and yield stabilized crude oil, condensing desired hydrocarbons from said removed vapors, contacting a portion of said stabilized crude oil with gaseous hydrocarbons which have been contacted but not absorbed by said unstabilized crude oil to absorb additional amounts of higher molecular weight hydrocarbons, and combining said portion with said unstabilized crude.

2. A process for the separation of light hydrocarbons including methane and ethane from a crude petroleum oil and the recovery of desired hydrocarbons from said separated light hydrocarbons and from a hydrocarbon gas mixture which comprises introducing unstabilized crude oil into an absorber, owing gases containing hydrocarbons upwardly through said absorber in countercurrent contact with the introduced crude oil so that the crude oil absorbs higher molecular weight hydrocarbons from the gases, withdrawing crude oil enriched with absorbed constituents from the bottom of said absorber and passing it to a stabilizer to vaporize and separate light hydrocarbons therefrom and to produce stabilized crude oil, withdrawing stabilized crude oil from said stabilizer and returning a portion thereof to said absorber at a point above the point of introduction of said unstabilized crude, condensing desired hydrocarbons from said separated light hydrocarbon vapo-rs and introducing the uncondensed portion into said absorber with additional amounts of said gases containing hydrocarbons.

WRIGHT W. GARY.

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