US2274094A

US2274094A - Refining process

Info

Publication number: US2274094A
Application number: US379391A
Authority: US
Inventors: Walter H Rupp
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1941-02-18
Filing date: 1941-02-18
Publication date: 1942-02-24
Anticipated expiration: 1959-02-24

Description

' mgm 12 8 9 2@ Feb. 24, 1942. w. H. RUPP l 2,274,094

REFNING PROCESS Filed Feb. 18, 1941 /N/ 'r/AL y l cooA /NC ssc ONDA RY l ZONE oNruss/alv l kzam: g I.

:ww 2 n 2q l 2232? .same by various processes.

Patented Feb. 24, 1942 UNITEDVSTATES PATENT OFFICE REFINING PROCESS walter 1i. Rupp, Mountainsiae, N. J., assigner to Standard Oil Development Company, a corporation of Delaware Application February 18, 1941, Serial No. 379,391A

4 Claims. Cl. 62--175.5)

The present invention is concerned with a process for the segregation and recovery of valuable hydrocarbon constituents from feed gas mixtures containing the same. The invention is more particularly directed to an Aimproved process comprising compressing, cooling and stripping stages by which it is possible to eiliciently and economically recover and segregate hydrocarbon constituents containing four or more carbon `atoms in the molecule from normally gaseous hydrocarbon feed constituents containing the same.

vIn accordance with the present process, feed gases containing recoverable hydrocarbons, se-

.cured in the refining of petroleumv oils, as for example from distillation, reforming, cracking or related refining operations, are compressed and the hot gases separated into primary and secondary feed gas streams. The primary feed gas stream is cooled and passed into an initial separation zone in which the liquid condensate is separated as a primary condensate from the uncondensed vapors. The uncondensed vapors are withdrawn from the initial separation zone,

further compressed, cooled, and passed into a secondary separation zone. The liquid condensate from' the secondary separation zone, and preferably at least a portion of the primary condensate, are combined and passed to a stripping zone in which the condensates countercurrently the quantities of the feed gases are relatively W, v

or when the feed gases are derived in rather isolated areas where steam generation facilities are not available for reboiling. Inaccordance with my process, valuable hydrocarbon constituents may be readily and elciently segregated from feed gases containing the same, utilizing a novel arrangement of compressing, cooling and strip- I ping zones.

contact the secondary stream of hot feed gases.`-

A stripped liquid hydrocarbon product substantially free of undesirable hydrocarbon constituents is withdrawn from the bottom of the stripping zone, whileuncondensed gases are withdrawn overhead from the stripping zone and combined with the primary stream of hot feed gases passed to the initial cooling zone.

lt is well-known in the art to segregate valuableY hydrocarbon constituents which may be utilized in motor fuels from gases containing the For example, it is known to contact feed gases containing recoverable hydrocarbons which may be included in motor fuels and thc like with various solid adsorbents which have a preferential selectivity for the valuable hydrocarbon constituents. The adsorbed hydrocarbons are recovered from the adsorbent usually by heating the same. The common practice, however, for the recovery of these hydrocarbon constituents-is to countercurrently contact feed gases under various temperature and pressure conditions with an absorption oil. The rich absorption oil containing the dissolved hydrocarbons is withdrawn from the bottom of the The process of my invention may be readily understood by reference to the attached drawing illustrating modifications of the same. For purposes `of illustration, it is assumed that the feed gases comprise hydrocarbon constituents, having from one to seven carbon atoms in the molecule, and are derived from crude wfll separators. These gases are introduced into. an initial compression zone I by means of feed line 2. These gases are compressed in zone I and are withdrawn IIJ-.means of line '3. The hot compressed feed ga's stream withdrawn from zone I is segregated into a primary feed gas stream, which stream is passed to initial cooling zone 4, and into a secondary feed gas stream which stream is removed by means of

line

2,2. The primary stream passed into initial cooling zone i is withdrawn by means of line 5, and introducedinto initial separation zone 6. Condensed liquid is withdrawn from initial separation zone E by means of pump t and line 9. The desired liquidlevel is maintained in initial'separation zone 8 by means of a oat control valve arrangement I0. Uncondensed vapors are removed overhead from initial separation zone 6 by means of line I I, passed to secondary compression zone I2, withdrawn `in any manner desirable.

yfrom said latter zone by meansy of line I3, cooled means of line I8, heated in heating zone i9 if desired, and combined with the liquid condensate withdrawn from initial separation zone 0. The combined condensates are introduced i'nto stripping zone 2| in which they countercurrently contact the segregated secondary feed stream of hot compressed gases which is removed from initial compresion zone l and segregated from said primary stream. These gases are introduced into the bottom section of stripping zone 2l by means of line 22. A liquid fraction substantially completely free of undesirable hydrocarbon constituents is removed from the bottom of stripping zone 2I by means of line 23, cooled in cooler 24 and withdrawn from the system by means of line 25. This product is substantially free of undesirable relatively low boiling constituents, is appreciably more stable than the condensates removed from the initial and secondary separation zones and thus may be incorporated in motor fuels or preferably employed as an intermediate feed stockhfor alkylation, isomerization or other allied processes. Uncondensed gases are withdrawn from stripping zone 2i by means of line 26 and mixed with the primary feed gas stream prior to cooling the same in initial cooling zone d. Under certain conditions it may be desirable to withdraw at least a part of the condensate from the initial separation zone from the system by means of line 2l.

The process of the present invention may be' widely varied. The process may be adaptedv for the segregation ofany particular hydrocarbon fraction desirable constituents from any feed gas containing the same. The process, however, is particularly adapted for the segregation of hydrocarbon constituents containing four or more carbon atomsfrom feed gases comprising hydrocarbon constituents containing one to seven carbon atoms in the molecule. The invention is especially adapted for the processing of gases of this character which are derived from crude oil well separators. It is, however, to be understood that the invention may be employed for treating feed gases derived from any refining, distilling, cracking, reforming or related operations. In general, it is preferred that the feed gases be compressed in the initial separation zone to a pressure in the range of about 200-400 lbs. per square'inch, preferably to a pressure of about 260-320 lbs. per square inch. It is desirable that the temperature of the gases be raised to a temperature in the range from about 200 to 300 F., preferably to a temperature in the range from about 225 to 275 F.

The relative proportions of the primary and secondary feed gas streams may vary considerably depending upon the character of the feed gases andalso upon general operating conditions. In general it is desirable that the secondary feed gas stream comprise at least 50% of the total feed gases. Particularly desirable results are secured when the secondary feed gas stream comprises at least 75% of the total feedgas.

The extent to which the primary feed gas stream is cooled in the initial cooling zone will vary considerably and will depend to a large extent upon the character of the feed gases. However, it is preferred that the primary gas stream be cooled in the initial cooling zone to a temperature below about 120 F., preferably to a temperature below about 100 F. In general, it is desired to condense approximately 5% to 25% by volume of the primary feed gas stream constituents.

The gases removed from the initial separation zone are compressed to a relatively high pressure in the general range from about 900 to about 1800 pounds per square inch. Particularly desirable results are securedwhen these gases are compressed to a pressure in the range above about 1500 pounds per square inch. The compressed gases are similarly cooled in the secondary cooling zone to a temperature below about 125 F., preferably to a temperature in the range from about F. to 100 F. When operating without the stripping "zone, a condensate is produced 'which contains a large percentage of hydrocarbons containing three or less carbon atoms in the molecule.

Although operating conditions in the stripping zone may be adjusted within relatively wide limits, it is preferred to maintain a pressure in the stripping zone in the range from about 190 pounds to 390 pounds per square inch and to maintain the temperature within said zone in the range from about 150 F. to 250 F'.

In order to illustrate the invention further, the following example is given which should not be construed as limiting the invention in any manner whatsoeverz- Feed gases comprising hydrocarbon constituents containing from one to seven carbon atoms in the molecule were compressed in an initial compression zone to about 265 pounds per square l`inch. The temperature of the compressed gases was about 203 F. These gases were segregated into a primary feed gas stream comprising about 25% of the total feed gases. This stream was cooled in an initial cooling zone to about F. whereby the pressure of the same was reduced to about 230 pounds per square inch. The uncondensed vapors were separated from the condensate in an initial separation zone and were compressed to' a pressure of about 940 pounds per square inch, whereby the temperature of the same was increased Yto about 200 F. These gases were cooled in the secondary cooling zone to a temperature of about 90 F., whereby the pressure of the gases wasL` reduced to aboutl 910 pounds per square inch. The liquid condensates from the initial separation zone and from the secondary separation zone were combined and introduced into the top of a stripping zone at a pressure of about 260 pounds per square inch. These condensates countercurrently contacted the remainder of the feed gases which had been segregated into a secondary feed gas stream in said stripping zone. under conditions in which the temperature at the bottom of the stripping zone was maintained in the range from about F. to F.

` Liquid Feed gas Gas from v to primary secondary pggglet c ompresseparation stripper sion zone zone zone Mol Mol Mol 2. 4 1 5 z3. o I 3. 4 2. 2 32. 0 1. 6 0. 6 23. 0 l o. e o. 1 11.0

t l Volume -per cent.A 100 95. Ilv 4. 4

Nomar-0" with the sub-n`umeral represents the number of' the compressed gases Without cooling into a primary feed gas stream and into a secondary feed gas stream, cooling said primary feed gas stream in an initial cooling zone, passing the mixture from said initial cooling zone into an initial separation zone wherein a separation is made between uncondensed vapors and the liquid condensate; passing said uncondensed vapors into a secondary compression zone, followed by cooling the same in a secondary cooling zone, passing the mixture from said. secondary cooling zone into a secondary separation zone wherein a separation is made between uncondensed vapors and a liquid4 condensate, combiningrthe condensates from said initial separation zone and said secondary separation zone and countercurrently `contacting these condensates with said secondary feed gas stream in a stripping zone under conditions to withdraw as a liquid bottoms from said stripping zone a liquid product substantially free of undesirable hydrocarbon constituents.

2. Process as defined by claim 1, in which said compressed feed gases withdrawn from said initial compression zone are segregated into a primary feed' gas stream comprising about 25% of the total volume of feed gases and into a secondary feed gas stream comprising about '75% of the total feed gases.

3. Process for the recovery and segregation of hydrocarbon constituents containing three or more carbon atoms in the molecule from feed gases containing the same, comprising hydrocarbon constituents containing from one to seven carbon atoms in the molecule, which comprises compressing the feed gases in an initial compression zone to a pressure in the range from about 200 to about 400 pounds per square inch. segregating said compressed gases into a primary feed gas stream and into a secondary feed gas stream, cooling said primary feed gas stream to a temperature below about 125 F., separatingr a liquid condensate from uncondensedvapors vin an initial 'separation zone, compressing said uncondensed vapors from said initial separation zone in a secondary compression zone to a pressure in the range above 900 pounds per square inch, cooling said compressed gases removed from said secondary compression zone in a secondary cooling zone, and separating a. liquid condensate from uncondensed vapors in a secondary separation zone, combining the condensates removed from the initial separation zone and the secondary separation zone, and countercurrently contacting the condensates with said secondary feed gas stream in a stripping zone at a pressure of above about 190 pounds per square inch and at a temperature above about 150 F., whereby a bottoms stream is removed from said stripping zone which is substantially free of hydrocarbon constituents containing less than two carbon atoms in the molecule.

4. Process as dened by claim 3, in which said compressed feed gases withdrawn from said initial compression zone aresegregated into a. primary feed gas stream comprising about 25% of the total volume of feed gases and into a secondary feed gas stream comprising about 75% of the total feed gases. Y

' WALTER H. RUPP.