US2224227A

US2224227A - Method of recovering gasoline from gases

Info

Publication number: US2224227A
Application number: US203860A
Authority: US
Inventors: Jr Percival C Keith; Jr Henry M Nelly
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1938-04-23
Filing date: 1938-04-23
Publication date: 1940-12-10
Anticipated expiration: 1957-12-10

Description

DeC l0, 1940- P. c. KEITH, JR., Erm. 2,224,227

METHOD OF RECOVERING GASOLINE FROM GASES .nlll

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I A ORNEY l INVENTO l// 6' /1/6/ RNW g IVI Patented Dec. 10, 1940 UNITED STATES PATENT OFFICE .METHOD F RECOVERING GASOLINE FROM GASES Application April 23, 193s, serial No. 203,860

7 Claims.

Our invention relates to a method of recovering gasoline from gases.

Customary absorption systems used for recov-v ering gasoline from gases are not efilcient when the gases which are to be subjected to absorption are lean.

One object of our invention is to provide'aV method of recovering gasoline from lean gases.

Another object of our invention is to provide an economical method of recovering gasoline and other liquid fractions from natural gases containing the same.

Other and further objects of our invention will appear from the following description.

The accompanying drawing which forms part of the instant specification and is to be read in conjunction therewith is a schematic view of one form of apparatus capable of carrying out the method of our invention.

20 It has been suggested to use low temperature rectification for the recovery of gasoline from gases. We have found, however that when this is attempted gas hydrates form, which clog the lines and prevent further operation of the proc- 25 ess. In general, our invention contemplates .the dehydration of the gas before its reduction in temperature. 'Ihe dehydration is conducted to such an extent that, at the temperatures involved, gas hydrates will not form.

30 More particularly referring now to the drawing, a feed g-as is charged through pipe I into a gas scrubber or knock-out drum 2. In a typical plant adapted to carry out the method of our invention, we have been able to recover 11,800 gallons of gasoline per day,. charging 10,000,000 cubic feet of gas per day. The scrubbing liquid may be any desirable liquid such as a slop crude, which is introduced into the scrubbing drum 2 through line 3, removed through 40 line 4, and pumped by pump 5 to slop crude storage. through pipe 6 at atmospheric pressure and at a temperature of about 100 F. The gas from pipe 6 passes through pipes 1 and 8 to compressors 9 45 and lll in which the gas is compressed to a pressure of about 75 pounds per square inch at which pressure the temperature will be about 270 F. The gas leaves the compressors 9 and I0 through pipes II and I2 and passes into pipe I3 into a 50 heat exchanger I4 into which cooling Water is introduced through pipe I5. The heat exchanger is such that the gas leaving the heat exchanger I4 through pipe I6 will be at a temperature of about 100 F. This gas enters heat 55 exchanger I1 in whichit is reduced in temper- The scrubbed gas leaves the drum 2A ature by heat exchange with a chilled gaseous medium. This chilled gas is withdrawn from vflash drum I8 through pipe I9 by which it is conducted to heat exchanger Il. The chilled gas is normally at a temperature in the vicinity of 5 p -30 F. The rate of flow of the feed gas is such with respect to the rate of flow of the cooling gas that the feed gas leaving lthe heat exchanger I1 through pipe 20 will be at a temperature of l about 41 F. 'I'his temperature is sulcient to 10 liquefy considerable Water and liquid fractions contained in the gas. 'I'he cooled feed gas is introduced from pipe into a Water separator tank 2I from which water is withdrawn through pipe 22. At the temperatures involved and for 15 the rate of feed given in a plant operated according to our invention, about 1200 pounds of Water perhour were withdrawn from the water separator drum 2l. About 200 gallons of gasoline per hour were also precipitated. 'I'his gasoline 20 was withdrawn from the separator 2| through pipe 23 and pumped by pump 24 through pipe 25 for introduction into the stabilizer tower 26 via pipes 2l and 28. The cooling gas introduced into the heat exchanger I'l'through pipe I9 is 25 Withdrawn from the heat exchanger through pipe 2l and introduced into a manifold 28" from which it may be Withdrawn through pipes and 29 for use as fuel or discharged as tail gas through pipe 3I. 1f desired, tail gas may be used 30 as a revivifying medium for the

driers

32 and 33 as will be hereinafter more fully pointed out. The cooled gas, freed of precipitated Water and gasoline, is removed from the separator 2l through pipe 34 and passed to the drying step. 35 The gas will be substantially at 4the same temperature in pipe 34A as when it entered the separator, namely at about F. 'Ihe

driers

32 and 33 comprise chambersk35 and 36 adapted to be operated alternately. The gas'from pipe 34 40 is introduced into the manifold 31. By opening the valve 38 and closing valve 39, drier 32 will be the one in use. A body of an adsorptive medium 40, such as silica gel, serves to adsorb moisture from the gas. The temperature of the gas entering the drier is above that at which the gas hydrates will form. The drying is such that the gas may now be chilled to a much lower temperature, enabling the recovery of substantial amounts of gasoline from the gases being subjected to our process. The dried gases leave the drier 32 through manifold 4I and pass into pipe 42. When drier 32 is in use, valve 43 will be open and valve 44 will be closed. After drier 32 has been in use for a period, it becomes humidied and its dehydratingability decreases. When this point is reached,

valves

38 and 43 are closed and valves 99 and 44 are opened. Valve 45 is opened, permitting tail gases from manifold 28 to pass through heat exchanger 46 in which the gases are heated by superheated steam introduced through pipe 41, lto a temperature of about 325 F. Valve 48 is closed and valve 49 is opened. The gases leaving the heat exchanger 46 through pipe 50 may pass through the chamber 35, heating the body of silica gel 40 and evaporating moisture therefrom. The drying gases that oo ntain moisture leave the drier 32 through pipe 5I and valve 52 being open and valve 53 being closed, the gases will pass through pipe 54 to the 'tail gas manifold 28. The heating of the gases expands them, causing them to flow through pipe 54 into the manifold 28. It will be understood, of course, that the drying gases may be directed to drier 33 by opening valve 48 and closing valve 49 when drier 32 is in use.

The dehydrated gases from pipe 42 pass into a heat exchanger 55 where they are chilled to a very low temperature. The cooling medium for the chilling passes to a heat exchanger 55 through pipe 56 and may comprise liquid propane, withdrawn by pipe 56 from propane ash drum 51. In chilling the gases in heat exchanger 55, some -of the propane will be vaporized. 'Ihe propane vapors leave the heat exchanger 55 through pipe 58 and pass into the propane flash drum 51, whence they are removed through pipe 59 and pass to a compressor 60, whence they are compressed to about 240 pounds per square inch. The propane gas in pipe59 will be at a temperature of about 40 F. and at a pressure of about 13 pounds per square inch. The propane leaving the compressor 60 through pipe 6| will be at a temperature of about 135 F. The hot compressed propane is passed through a cooler 62 in heat exchange with a cooling medium such as water introduced through pipe 63 in which Ithe propane is cooled to a temperature of about F. The cooled propane leaves the heat exchanger 62 through pipe 64 and passes into a propane receiver 65. The propane is withdrawn from the receiver 65 through pipe 66 and passed to a heat exchanger 61. In the heat exchanger 61, the propane is cooled by heat exchange with unstabilized gasoline, introduced through pipe 68, being withdrawn by pump 69 from flash drum I8. The unstabilized gasoline passing through the heat exchanger 61 is introduced thereto at a temperature of about 30 F. 'I'he propane leaves the heat exchanger 61 through pipe 10 at a temperature of about 40 F. and is introduce into the propane flash drum 51.

The gases leaving the heat exchanger 55 will be cooled to a temperature of about 30 F. This low temperature will precipitate gasoline and low boiling hydrocarbons. The condensed liquid and uncondensed 'gases are withdrawn from the heat exchanger 55 through pipe 1I and are introduced into the flash drum I 8. The gaseous hydrocarbons are withdrawn from the flash drum I8 through pipe I9 as heretofore described. The liquid condensate is withdrawn from the flash drum I8 through pipe 12 controlled by Valve 13 and pumped by pump 69 through heat exchanger 61 as pointed out above.

In the example which is being used throughout this specification, the gasoline leaves the heat exchanger 61 through pipe 14 at a temperature of about 90 F. In pipe 14, the gasoline is joined by the gasoline precipitated in the separator 2| and the unstabilized gasoline passes into heat exchanger 15 through pipe 21. In the heat exchanger, it is heated to a. temperature of about F. and at this temperature, it enters the stabilizer 26 through pipe 28. The gasoline is reboiled in stabilizer tower 26 in reboiler 16 which is supplied steam through pipe 11. The bottom of the tower is kept at a temperature of about 222 F. and is operated under a pressure of 140 pounds per square inch. The vapors leaving the top vof the stabilizer through pipe 18 are at a temperature of about F. They pass through a heat exchanger 19, supplied with a cooling medium through pipe 80 and are cooled therein -to a temperature of about 100 F. The condensate passes from heat exchanger 19 through pipe 8I into a refiux drum 82 from which reux is withdrawn through pipe 83 and pumped by pump'84 through pipe 85 to the tower as a control reiiux, keeping the top tower at about 100 F. Stabilizer gas is vented through pressure control valve 86 bypipe 81. The stabilizer gas maybe passed to the tail gas manifold 28. The stabilized gasoline is withdrawn from the stabilizer tower 26 through pipe 88 and passes through heat exchanger 15, being withdrawn therefrom through pipe 89 and passing to storage tanks 90 and 9I whence it is withdrawn through manifold 92. The stabilized gasoline leaving the heat exchanger 15 wiil be ata temperature of about 100 F.

It is to be understood that the temperatures and pressures used throughout this specification are by way of illustration only and not by way of limitation.

It will be seen that we have accomplished the objects of our invention. We have provided a method of recovering gasoline from lean gases by low temperature rectification and stabilization while avoiding the formation of gas hydrates. The use of lean tail gas to revivify the driers and the drying of the precooled tail gas before final chilling to prevent the formation of gas hydrates are novel features, enabling the employment of our invention to recover valuable low boiling liquid hydrocarbons suitable for use as a motor fuel from lean hydrocarbon gases. The recovery of the valuable liquid hydrocarbons by means-of our method could not be accomplished by conventional absorption or rectification methods.

It will be understood that certain features and subcombinations are of utility and may be ernployed without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. obvious that various changes may be made in details within the scope of our claims without departing from the 'spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus describedour invention, we claim:

1. A method of recovering gasoline from mixtures of hydrocarbon gases which comprises compressing hydrocarbon gases, cooling the compressed gases to a relatively low temperature above the freezing point of water and above that at which solid hydrocarbon hydrates will form to condense water and some gasoline, separating the water from the remaining gases and separating the gasoline from the remaining gases, passing the remaining gases through a dryer zone to remove substantially all the moisture from such gases, then reducing the temperature of the re- It is further maining dried gases to a relatively low temperature below the freezing point of water to condense gasoline, combining the gasoline separated in the two cooling stepsand introducing it into.

a stabilizing zone for stabilizing the gasoline.

2. A method of recovering gasoline from mixtures of hydrocarbon gases which comprises compressing hydrocarbon gases, cooling the compressed gases to a relatively low temperature above the freezing point of water and above that at which solid hydrocarbon hydrates will form to condense water and some gasoline, separating the water from the remaining gases and separating the gasoline from the remaining gases, passing the remaining gases through an adsorbing agent in a dryer zone to remove substantially all the moisture from such gases, then reducing the temperature of the remaining dried gases to a relatively low temperature below the freezing point of water to condense gasoline, passing the cooled gases and gasoline to a separating zone to separate gasoline from cold gases and using the separated cold gases for initially cooling the compressed gas at the beginning of the method and thereafter heating the separated gases and using the heated gases as a drying medium for revivifying the adsorbing agent in another dryer zone.

3. A method of recovering liquid hydrocarbons within the gasoline boiling range from mixtures of hydrocarbon gases containing gasoline constituents which comprises cooling said hydrocarbon gases under superatmospheric pressure to a relatively low temperature above the freezing point of water and above that at which solid hydrocarbon hydrates will form to condense water and some gasoline,.separating Water, liquid hydrocarbons containing gasoline constitutents and remaining gases from each other, passing gases thus separated through a dryer zone at atemperature above that at which solid hydrocarbon hydrates will form to remove substantially all of the moisture from such gases. reducing the tem perature of the thus dried gases to a relatively low temperature below the freezing point of water to condense liquid hydrocarbons containing gasoline constituents and stabilizing gasoline separated in the two cooling steps.

4. A method of recovering liquid hydrocarbons within the gasoline boiling range from mixtures of hydrocarbon -gases containing gasoline constituents which comprises cooling said hydrocarbon gases under superatmospheric pressure to a relatively low temperature above the freezing point of water and above that at which solid hydrocarbon hydrates will form to condense Water and some gasoline, separating water, liquid hydrocarbons containing gasoline constituents and remaining gases from each other, passing gases thus separated through a dryer zone at a temperature above that at which solid hydrocarbon hydrates will form to remove substantially all of the moisture from such gases, reducing the temperature of the thus dried gases to a relatively 10W temperature below the freezing point of water to condense liquid hydrocarbons containing gasoline constituents, combining gasoline constituents separated in the two cooling steps and introducing combined constituents into an enlarged zone wherein volatile constituents are removed.

5. A method of recovering liquid hydrocarbons within the gasoline boiling range from mixtures of hydrocarbon gases containing gasoline constituents which comprises cooling said hydrocarbon gases under superatmospheric pressure to a relatively low temperature above the freezing point of water and above that at which solid hydrocarbon hydrates will form to condense water and some gasoline, separating water, liquid hydrocarbons containing gasoline constituents and remaining gases from each other. passing gases thus separated through a dryer zone at a temperature above that at which solid hydrocarbon hydrates will form to remove substantially all of the moisture from such gases, reducing the temperature of the thus dried gases to a relatively low temperature below the freezing point of water to condense liquid hydrocarbons containing gasoline constituents, separating liquid hydrocarbons containing gasoline constituents from cold gases and utilizing separated cold gases thus obtained for initially cooling the hydrocarbon gases under superatmospheric pressure.

6. A method of recovering liquid hydrocarbons within the gasoline boiling range from mixtures of hydrocarbon gases containing gasoline constituents which comprises cooling said hydrocarbon gases under superatmospheric pressure to a relatively low temperature above the freezing point of water and above that at which solid hydrocarbon hydrates will form to condense water and some gasoline, separating water, liquid hydrocarbons containing gasoline constituents and remaining gases from each other, passing gases thus separated/through a dryer zone at a temperature above that at which solid hydrocarbon hydrates will form to remove substantially all of the moisture from such gases, reducing the temperature of the thus dried gases to a relatively low temperature below the freezing point of water to condense liquid hydrocarbons containing gasoline constituents, separating liquid hydrocarbons containing gasoline constituents 4from cold gases, heating cold gases thus obtained and using the heated gases as a drying medium for revivifying the absorbing agent in another dryer zone.

'1. A method of recovering gasoline from mix- .tures of hydrocarbon gases which comprises cooling hydrocarbon gases under superatmospheric pressure to a relatively low temperature above the freezing point of water and above that at which solid hydrocarbon hydrates will form to condense water and some gasoline. separating the water from the remaining gases and separating the gasoline from the remaining gases, passing the remaining gases through a dryer zone at a temperature above that at which solid hydrocarbon hydrates will form to remove substantially all of the moisture from such gases. then reducing the temperature of the remaining dried gases to a relatively low temperature below the freezing point of water to condense gasoline, combining the gasoline separated in the two cooling steps and introducing it into a stabilizing zone for