US2876865A

US2876865A - Cooling hot gases

Info

Publication number: US2876865A
Application number: US620072A
Authority: US
Inventors: Jr Joseph R Cobb
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1956-11-02
Filing date: 1956-11-02
Publication date: 1959-03-10
Anticipated expiration: 1976-03-10

Description

March 1K0, 1959A l l J. R.r.c:oBB, JR

' COOLING HOT GASES Filed New. z, 195e INVENTOR. J.R. COBB,JR.

A T T0 RNEVS United States Patent O COOLING Hor GASES Joseph R. Cobb, Jr., Bartlesville, Okla., assignor tol Phillips Petroleum Company,V a corporation of Delaware Application November 2, 1956, Serial No. 620,072

11 Claims. (Cl. 1S3-120) This invention relates to a method and apparatus for preparingy low molecular weight hot cracked gases con taining easily' polymerizable materials for subsequent processing under pressure. In one aspect it. relates to a method and apparatus for conducting such. an operation with the production and deposition of a minimum of' polymeric material on the inner surface of' equipment exposed to the cracked gases. In another aspect it relates to a methodV and apparatus for preparing such gases for processingy at a higher pressure than the pressure at which they were produced, with a minimum of? heat exchange surfaces and. with a minimum of cooling.

It is known that ethylene and other low molecularl weight unsaturated hydrocarbonsl can 4dvantageously bel produced by high temperature crackingbf light hydrocarbons such as ethane, propane,.-buta`r`te`or other'hydr carbons. The present invention is'co'ncerned primarily with the problem of cooling,l the eiliuenktgases from such' a; cracking process and with their l pression in such a manner as to obtain the gasesfat pressure suitable for' subsequent high pressure proczessingV without forma-- tion of solid polymeric material orwith the `formation of a minimum of deposited polymeric material on surfaces to which the gases are exposed. The deposited solid polymeric material is believed'mainlytheresult of polymerization of diolenic material. such asbutadiene` and cyclopentadiene in the ethylene containing gases produced in the above mentioned hydrocarbon cracking. The amount of polymer formed is believed to be a function of the amount of certain tracev hydrocarbons in the Cg-Cm range which are believed to catalyze this polymerization.

The present invention employs a combination of water quenching and oil quenching steps. Novell heat exchange steps are employed in combination with furnace` etlluent quenching. in such a manner as to avoid deposition of solid polymeric material on the Walls ofl the processing equipment. Mainly the invention comprises av method for preparing hot feed gases for subsequent high pressure processing comprising the stepsV of cooling; said hot gases by direct heat exchange .with a cool quench oil, further cooling the cooled gases by direct heat exchange with cooling Water, still further cooling` the further cooled gases by direct heat exchange with refrigerated water and compressing the still further cooled gases to a pressure suitable for said. high pressure processing.

An object of my invention is toprovide apparatus and method for cooling and compressing for subsequent processing cracking still effluent gases to a lower temperature and a higher pressure than the gases possessed when produced. A

Yet another object of my invention is to provide such apparatus and method in which polymer formation anddeposition on the inner walls of the processing equipment are reduced to a minimum.

Yet another object of my invention is:v to'provide-sucl'l a method andl apparatusl which is, easy andl simpl'efto'- construct and' to operate.

Yet another object of my in ventionv is to providev suchy a method. and apparatus which involves simplied heat; exchangev operations' in such a manner as to avoid use; of tubular heat'V exchangers.

OtherY objectsv andA advantages and features of the in@ vention. will become apparent from the following detailed description which, taken with the attached drawing; formsr a partk ofthisA specification.

In the drawing, the ligure represents, in diagrammatic form, one arrangement of apparatusY parts for carrying; out the processI of my invention.

When cracking such feed materials as ethane, propane,l butane or other relatively low molecular Weight hydrocarbons or mixturesof such materialsfor the production of ethylene, forexample, easily polymerizable hydrocarbonsv such asacetylene, alkyl substituted acetylene, butadiene, cyclopentadiene, and heavier olenic and d'iolefinicv hydrocarbons are unavoidably produced. However, evidence is; available to show that where the C3,v through C12 fraction produced in some quantity in crack'- ing any hydrocarbon has been' removed, polymer production. is retarded* By` use of my invention the amount of' CgA-Cm. hydrocarbons taken to the first stage of compression isl reduced to about one. fourth of that which goes to the compressors using a conventional scheme: In conventional operations iuvolvinghandling of. gases;1 containing ethylene and' such easily;"pol'frrrerizablefma terials, polymers form on the. inner processing equipment as pipes, hea compressor rotors or cylinders anlthv y conditions equipment has to bel'shut down. and exchange and compressor rotors or cylinders" leaned of Ideposite' polymers. Deposited polymers on inner surface of s119171 equipment greatly reduce heat exchange eiiciencies"as`A` is well known. My invention provides a process'and My process was' particularly devised so asto avoid the' use of conventional heat exchangers. Furthermorefmy-f' process. involves cooling the cracked gases to tempera@ 1 tures below ordinary cooling water temperatures.

Referring now to the drawing, a charge stock material which is ethane, propane, butane, and isobut'ane, or rni'x-y turesy ofl two or more of these hydrocarbons'. or otherxv low molecular weight hydrocarbons suitable for use inV producing such amaterial as ethylene, is introducedv from; a source, not. shown, into my system through a* conduit' I1'. A pump 13 transfers the feed material through a; heat exchanger 15 intol a cracking furnace 17. Heat ex,.-y changer 15 is intended to supply sutlicientheat to vapori'ze. feed stock liquid to make certain that only Vaporousl feed' enters the cracking furnace. Eliluent from the crackingv furnace is passed through a pipev 1,8, quench water isadded there to from. a pipe 2t), the water being vaporized by the hot gases'. The furnace ellluent and water vapor mixture is passed into aquench tower 2l. Pipe- 1'9" communicates with` the quench tower at anl elevation near its bottom.. The vapors so introduced into the lower portion of this quench tower how upwardly in countercurrent relation to quench, oil sprayed into the towerAY through a spray ring 42. Battles 39 or other suitable vapor-liquid' contact equipment are provided for promoting eliicient contacting of vapor and oil. Partially cooled vapors are passed through the central portion or' a liquid'.` take-olf tray such as a do-nut tray 43 and rise onupward' through the tower; Water from a pipe 31 is sprayed by: a spray 41 at an elevation appreciably above. the level'of they do-nut tray to provide further cooling for the ascend-.- ingl vapors... Vapor-liquid' contacting is promoted in thief. section of' the quench tower by bafiies: 3.9. Additional- 'Under sont 3 water which is cooled by refrigeration to a temperature well below atmospheric is introduced at a level near the top of the tower throughfa spray ring 37. Additional bales 39 or other vapor-liquid contact promoting apparatus is also provided in this upper section of the tower. Cooled vapors leave the tower through a pipe 23 and pass to a knock out drum 55 for separation of any liquid formed in the overhead pipe 23 or carried thereinto from the tower 21. Liquid separated in knock out drum 55 is removed by way of pipe 57 for such disposal, depending upon its composition, as desired. Vapors separated in drum 55 are passed on through a pipe 59, are compressed in a compressor 61 and are passed on into the lower portion of a second cooling tower 63. This tower is also provided with baflies 71 or other suitable vapor-liquid contacting apparatus. Cooling water at conventional cooling water temperatures is sprayed through a lspray ring 73 to cool the vapors heated by compressor 61 while refrigerated water is sprayed into the gases in the upper portion of tower 63 through a spray ring 69. Cooled gases leave cooling tower 63 by way of a pipe 65 and are compressed in a compressor 81 to such a pressure as desired in a subsequent processing operation. Suchan operation can be an absorption operation for extracting the ethylene from the cracked gases. Any condensate passing through the portion of conduit 65 down stream, as regards direction of ow from compressor 81, is separated in a knock out drum 83. Separated liquid is removed through a pipe 85 for disposal as desired, and depending on its composition. Vapors separated in .this knock out drum are passed to, for example, such a subsequent processing operation as an absorption operation. Such an 'operation is illustrated as being carried out in an absorber 89, lean absorptionoil being introduced thereinto by way of a pipe 93 and rich oil being removed therefrom through a pipe 95. Gases deleted of the absorbed constituent or constituents are removed from the absorber through a pipe 91.

l Hot quench oil in the bottom of the quench tower- 21 is passed therefrom through a pipe 25 to the aforementioned heat exchanger 15 to provide suflicient heat for Vaporizing the feed stock to the operation. The quench oil cooled in this heat exchanger is passed directly through a pipe 27 to spray ring 42 or in some cases it is desirable to cool further by atmospheric or other cooling the quench oil prior to its introduction through spray ring 42.

The water introduced into quench tower 21 through spray ring 41 is ordinary plant cooling Water, the water originating from a source, not shown, and passing by way of a pipe 29 for use in the operations described herein. From pipe 29 plant cooling water is passed on through a pipe 31 in to the above mentioned spray ring 41. A portion of the water from pipe 29 is passed through conduit 33 and is refrigerated in a heat exchanger 35 prior to introduction through spray ring 37 into the upper cooling section of quench tower 21. The water introduced through spray ring 37 and that introduced through spray ring 41 collect on the do-nut or take-off tray 43 and the collected water and condensed oil are removed therefrom by way of a pipe 45 and are passed into an oil-water separator 47. In this separator oil separates as an upper layer and is removed through a pipe 49 for such disposal as desired. The water layer from the bottom of separator 47 is passed by way of a pipe 51 to a conventional plant cooling tower such as is ordinarily used in industrial plants.

A portion of the water from the plant cooling towers, not shown, and entering my system by way of pipe 29 is by-passed from quench tower 21 and flows through a` pipe 75 for use in the cooling tower 63. A portion of the water from pipe 75 is passed through a pipe 77 and thence through the spray ring 73 for cooling the gases in the lower portion of this vessel. The remainder of the water from pipe 75 is passed through a refrigerated exinto the upper portion of cooling tower 63 through the spray ring 69.

While propylene is a preferred refrigerant for the refrigerated exchangers 35 "and 79, other refrigerants, such as sulfur dioxide, butano, isobutane, etc., are used under some conditions. Such refrigerant systems are well known in the art.

A vent pipe 53 is provided for the oil-water separator 47 in case pressure relief is necessary.

Water sprayed through spray rings 69 and 73 and condensed oil flow to the bottom of cooling tower 63 and are removed therefrom by way of a pipe 67 and is combined with the water from pipe 45 for passage into the oil-water separator 47.

In describing briefly the above operation it will be realized that such equipment as valves, ow controllers, ratio flow controllers, meters, pressure indicating and recording equipment and the like are provided at proper process points for maintaining proper control of the process. Such equipment, their installation and use, are well understood by those skilled in the processing art.

As a specific example of the operation of the process of my invention, a mixture comprising normal butane and isobutane is introduced into furnace .17 through conduit 11. These two gases are supplied in the ratio of 972 mols of normal butane to 28 mols of isobutane. From a pipe 16 is introduced into this feed mixture 249 mols of water per 1,000 mols of the feed mixture in the form of steam. The hydrocarbon and steam mixture is heated rapidly in furnace 17 to a furnace outlettemperature-` of about 1,500 F. Inlet pressure to the furnace is about 85 pounds per square inch yabsolute (p. s. i. a.). .An appreciable pressurevdrop occurs on passing through the furnace and the gases issue therefrom into pipe 18 at a'pressure of about 20 p. s. i. a. at the above mentioned about 1,500 F. 1,240 mols of liquidI water at approximately 100 F. are introduced into pipe 18 from pipe 20 to quench the furnace eluent to about 900 F. to prevent or at least retard further cracking or undesired side reactions.

Quench oil is supplied to quench tower 21 at about 140 F. and at a rate of about 1,920 mols per 1,000 mols of feed gas. The quench oil cools the hot gases from the water quench temperature of about 900 F. to about 180 F. By this heat exchange the quench oil is heated to about 375 F. and the quench oil at this temperature is used in exchanger 15 for making certain that the feed to the operation is in the gaseous condition. As mentioned above, additional heat exchange can be employed to cool the quench oil from exchanger 15, if desired, prior to reintroduction into tower 21 to make certain that the oil introduced thereinto has a temperature of about 140 F.

The oil quenched gases pass through the do-nut tray 43 and rise upward and are cooled by plant cooling water from spray ring 41 to about 116 F. The refrigerated water, cooled by propylene refrigeration in exchanger 35, is sprayed into the top of this tower at a temperature of about 52 F., the gases being cooled thereby to a temperature of about 58 F. The refrigerated water from spray ring 37 and the plant cooling water from spray ring 41 reach the do-nut tray at a temperature of about 150 F. The refrigerated water from spray ring 37 changer 79 and on through a pipe 80 for introduction 75 reaches a temperature of about F. by the time it reaches the top of spray ring 41. The cooled gases leave the top of this quench tower through pipe 23 at a temperature of about 58 F. and at a pressure of about 18 p. s. i. a. It is noted that the cracked gases and steam entering quench tower 21 have a pressure of about 20 p. s. i. a. and experience a pressure drop of only about 2 p. s. i. a. on passing' through the length of this quench tower. That point is one of the important advantages of my invention, that is, the pressure drop experienced by the relatively low pressure gases is relatively small ou passing through this heat exchange operation. It is realized that the same flow of gases passing through conventional tube heat exchangers for indirect heat exchange would? experience a much greater pressure drop by the time they were cooled to the same temperature at Whichthe gases leave quench tower 21. Furthermore, at these relatively low pressures large heat exchange surfaces are required. As a result of the relatively low pressure drop in quench tower 21, the compression load ofa subsequent compressor is greatly reduced for compressing the cooled gases to a subsequent processing pressure. Compressor 61 compresses the 18 p. s. i. a. gases to a pressure of about 67 p. s. i. a. and the gases experience an increase in temperature from about 58 F. to. about 250 F. by this compression. At this orlower temperatures polymer formation is quite small.

The oil condensed by the refrigerated water in the upper portion of. vessel 21 contains an appreciable amount of the hereinbefore mentioned C8 to C12 hydrocarbon fracare` thoseV for` vaporizing the feedstock (i151) andforzthel propylene refrigeration (35, 79) of the water. Thezwaterr issuing from. the. propylenearefrigerated exchangers. and:` 79 has atemperaturei ofk about 52 F. and the, propyliene issuing therefrom hasv a: temperature. ofk about 42r F. I nd that while other refrigerants can beY successfullyused ink this: service, propylene. is well suited to the op-V eration. andr is` a preferred refrigerant. The particular propylene.- refrigeration. systememployed can be one constructed along conventional lines,v the only specific. requirement being that. itbe adapted to cool the. water in the refrigerated exchangers to a temperaturev of about 52 F.

Summing up'the. operation ofthe above example is the: following; table. which givesl product compositions; with` respect to hydrocarbons and .water contents a-t various processing points. The compositions are given in terms: of,` pound mol-sv per hour.

Processing Point (19) (27) f' (25)l (23) (45) (65) (67) Feed to Quench Quenchl Over- Water lCooled Mols per Hour Quench Oil Oil head Out Over- Bottoms Tower In Out 15D,o F f Head (31) Cooling tower water in at 110 F., 31,200 mols per hour.

(33) Refrigerated water in at 52 (77) Cooling tower water-inv at 1109 F E., 3,620mols per hour.

l., 580 mois. per hour.

(79) Reirlgerated Water in at 52' F., 639 mols per hour.

tion. As previously mentioned, my process removes more of these C8 to C12 hydrocarbons than do conventional processes. By removing a greater proportionV of these hydrocarbons a somewhat higher compressor outlet temperature of the ethylene containing stream (about 250 R), can be tolerated without excessive fouling of process equipment over that tolerated by prior art processes in which compressor outlet temperatures are held to about 200 F. to avoid excessiveY polymer deposition.

In order to compress further these gases I provide the additional cooling tower 63 in which an additional quantity of plant cooling water is sprayed through spray ring 73 and additional refrigerated water is sprayed through spray ring 69 to cool again the gases to a temperature of about 58 F. The plant water through spray ring 73 and the refrigerated water through spray ring 69 have the same corresponding temperatures as those utilized in quench tower 21. The 52 F. water from spray ring 69 increases in temperature to about 102 F. by the time it reaches spray ring 73. Plant water at 110 F. combines with this 102 F. Water and they reach a temperature of about 140 F. in the bottom of this cooling tower. The gasesv are cooled in the lower portion of this tower to a temperature of about 116 F. by the time they pass the spray ring 73 into the upper portion of the tower. Cooled gases leave tower 63 at a temperature of about 58 F. and at a pressure of about 65 p. s. i. a. and upon further cornpression in compressor Si the gases reach the subsequent processing step illustrated by absorber 89 at about 100 F., i. e., at ambient temperature, and at a pressure of about 170 p. s. i. a. By ambient temperature, ,I meanf atmospheric temperature. Y

It will be noted that in the illustration givenl hereinabove I have not employed a tube-containing heat ex-y changer for any cooling step of the cracked gases. The only tube containing heat exchangers whichv I `haveused,

In the abover illustrated process a smaller than converttional pressure drop was experienced on passing through quench tower 21 and cooling tower 63 than through conventional tube containing heat exchangers, and therefore lessl horse power isrequired for compressing the final cooled gases to the same' pressure of about 170 p. s. i. a. at F. When using conventional tube containing exchangers, the horse power required per hourk per 1,000 pound molsv of feed: gas tov the. system for this compression is 4,390 in comparison to only 3,690. horsepower required in the process. abovey described, including refrigeration requirementsz. This. diterencez in power require mentA is appreciable when considered on a 1,000 pound. mol feed gas-basis'.

From the above detailed description it'. is. seen that my invention causes less pressure drop of gases being cooled. than when employing tubey containing heat exchangers, which, as mentioned, resultsin a saving in compression requirements. Furthermore, by being able to avoid entirely the use of tube containing eat exchangers there is no fouling of heat exchange surfaces because of deposited polymer, with the result'that stand-by exchangers need not be provided when the exchangers which havei been on stream' need. to be tty-passed for cleaning purposes. As isl well known, such cleaning of' heat exchangers is a costly operation. v

Furthermore, by use of' an oil quench and direct water quench (refrigerated.) cooling steps, polymer forming agents are removed` from the cracked gas streamv to aconsiderable. extent. by solution in the oil and such removal' further assists in elimination of deposited polymer on the processing equipment. Also, the smaller pressure dropk through by direct quenchand heat exchangers requires less compression and, therefore, less heating, of the gasesl and less heatngpby compression also assists in reducingpolymer formation and deposition on the processing equipment.

While I have disclosed

compressors

61 and 81 as being single stage compressors, they can, if desired, be multistage compressors. In like manner, I have disclosed two cooling

vessels

21 and 63, but it will be obvious that depending on the service, more than two cooling stages are used where required, each involving use of plant cooling water and refrigerated water, the flrst stage obviously employing quench oil as disclosed in vessel 21.

The quench oil employed is substantially any heavy oil, parainic or aromatic, which will flow and can be sprayed at the lowest temperatures involved. A preferred oil is a heavy aromatic oil which is produced in the cracking operation and permitted to accumulate in the process. Oil for starting the operation and make up oil, if required, is introduced into the system through a pipe 26. However, if an excess of oil is produced Vin the operation over that required for quenching and heat exchange purposes, this excess oil is removed through pipe 26. Such an oil as is suitable for quench purposes in my operation has the following characteristics:

Specific gravity at 60/60 F.=l.0655

Kinematic viscosity at 100 F.=14.38 centistokes Kinematic viscosity at 210 F.=2.86 centistokes Bureau of Mines correlation index=133 ASTM distillation, corrected to 760 mm. Hg

In the operation of my process utilizing such a feed stock as herein disclosed there is little undesirable polymer formation in compressors and piping as long as temperatures of the ethylene containing gases are maintained at about 250 F. and below. Itis believed that the quench oil absorbs out a portion of the easily polymerizable material, but that material remaining in the gases undergoing treatment does not polymerize and deposit on equipment to any great extent as long as the temperature is maintained at about 250 F. and below.

While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto.

It .has been found that when the temperature of the gases leaving the quench tower 21 through line 23 is below about 60 F. that compressor 61 will run much longer without polymer deposit therein than if the temperature is above about 60 F., so that as to this specic aspect of about 60 F. in line 23 this temperature is in fact critical to complete polymer removal by the time the iluid undergoing treatment leaves vessel 21.

I claim:

1. A process for preparing low pressure, high temperature cracked gases containing ethylene and easily polymerizable hydrocarbons for subsequent processing at a pressure higher than said low pressure and at ambient temperature comprising the steps of quenching said high temperature cracked gases by direct heat exchange with a cool quench oil, cooling the quenched gases by direct heat exchange with plant cooling water, further cooling the cooled gases by direct heat exchange with refrigerated water, compressing the further cooled gases to such a pressure that the compressed gases issue from said compress or at a temperature of about 250 F., cooling the compressed gases by direct heat exchange with plant cooling water, still furthercooling these latter cooled gases by direct heat exchange with refrigerated water, and compressing the still further cooled gases to such a pressure higher than the aforesaid low pressure that compressed gases issuing from this latter compression step issue therefrom at substantially ambient temperature.

2. In the process of claim 1 wherein said refrigerated Water possesses a temperature of about 52 F.

3. In the process of claim l wherein said plant cooling water possesses a temperature of about 100 F., and said refrigerated water possesses a temperature of about 52 F., and said ambient temperature is about 100 F.

4. ln the process of claim l wherein the first mentioned compression step compresses said gases to a pressure of about 67 p. s. i. a. and the second mentioned compression step compresses the still further cooled gases to a pressure of about 170 p. s. i. a.

5. A method comprising quenching hot cracked hydrocarbon gases by direct heat exchange with a cool quench oil in a first quench zone, withdrawing quenched gases from said first quench zone and cooling the withdrawn gases by direct heat exchange with plant cooling water in a first cooling zone, passing cooled gases from said first cooling zone into a second cooling zone and therein further cooling the cooled gases by direct heat exchange with refrigerated water, withdrawing further cooled gases from said second cooling zone, combining the refrigerated water from said second cooling zone with the plant cooling water in said first cooling zone and withdrawing the combined stream of Water from said first cooling zone, compressing the withdrawn further cooled gases in a compression zone to such a pressure that the compressed gases issuing from the compression zone issue therefrom at a temperature below which easily polymerizable materials in said cracked gases form solid polymeric material, cooling the compressed gases in a third cooling zone by direct heat exchange with plant cooling water, further cooling these latter cooled gases in a fourth cooling zone by direct heat exchange with refrigerated water, combining the water from the fourth cooling zone with the water in the third cooling zone and withdrawing this combined water from said third zone, withdrawing the cooled gases from said fourth cooling zone, compressing these latter cooled gases in a second compression zone to a pressure that the compressed gases issue therefrom at ambient temperature, said compressed gases at ambient temperature being suitable for subsequent processing.

6. In the process of claim 5 wherein the temperature of said refrigerated water is about 52 F., said ambient temperature is about F. and the pressure of the gases issuing from said second compression zone is about p. s. 1. a.

7. A method for preparing high temperature cracked hydrocarbon gases containing easily polymerizable constituents for subsequent high pressure processing comprising cooling the high temperature cracked gases by quenching with water to a temperature of about 900 F., quenching the water quenched gases by direct heat exchange with a cool quench oil, cooling the oil quenched gases by direct heat exchange with plant cooling water, and further cooling the cooled gases by direct heat exchange with refrigerated water, and subsequently compressing the further cooled gases to a pressure suitable for subsequent processing whereby the temperature of the compressed gases is maintained at a value below that at which solid polymers are formed and deposited on the walls of the processing equipment.

8. A process for preparing low pressure, high temperature cracked gases containing ethylene and easily polymerizable hydrocarbons for subsequent processing at a pressure higher than said low pressure and at a temperature below said high temperature comprising the steps of introducing a cool quench oil into the upper portion of a high temperature quench section of a heat exchange zone, introducing said low pressure, high ternperature gases into the lower portion of said high temperature'quench section, introducing plant cooling water into the upper portion of a first water cooling section of said zone, the lower portion of said first water cooling section being above and in communication with the upper portion of said quench section, introducing refrigerated water into the upper portion of a second water cooling section of said zone, the lower portion of said second water cooling section being above and in communication with the upper portion of said iirst water cooling section, counter-currently contacting said cool quench oil and the introduced high temperature gases in said quench section whereby said introduced gases are quenched, passing the quenched gases from the upper portion of said quench section into the lower portion of said first water cooling section and therein countercurrently contacting said quenched gases with said plant cooling water whereby said quenched gases are cooled, passing the cooled gases from the upper portion of said first water cooling section into the lower portion of said second water cooling section and therein countercurrently contacting same with the introduced refrigerated water whereby the gases are further cooled, mixing the countercurrently contacted refrigerated water with the introduced plant cooling water prior to the countercurrent contacting of the quenched gases with said plant cooling water, withdrawing the further cooled gases from the upper portion of said second water cooling section and compressing same to a pressure higher than the aforesaid low pressure, withdrawing the compressed gases from the cornpressing step at a temperature below which appreciable polymerization of said polymerizable material occurs, withdrawing countercurrently contacted quench oil and the mixed plant cooling water and refrigerated water respectively from the quench section and the rst water cooling section of said heat exchange zone, introducing the compressed gases into the lower portion of a second heat exchange zone, introducing plant cooling water into said second zone at a level about midway from top to bottom thereof, introducing refrigerated water into said second zone at about the top thereof, the portion of the second zone above the level of introduction of said plant cooling water being the upper portion and the portion below said level being the lower portion thereof, countercurrently contacting the introduced compressed gases with a mixture of the last mentioned plant cooling water and the last mentioned refrigerated water as subsequently produced in said lower portion of this second zone, passing these latter countercurrently contacted gases into the upper portion of said second zone and therein countercurrently contacting same with the refrigerated water introduced into said second zone, passing this latter countercurrently contacted refrigerated water into the lower portion of said second zone and mixing same with said plant water introduced thereinto as said mixture of cooling Water and refrigerated water as subsequently produced, withdrawing the nally countercurrently contacted gases from the upper portion of said second zone, compressing these latter withdrawn gases to a pressure higher than the aforementioned compression step, withdrawing these nally compressed gases from this latter compression step at an ambient temperature and withdrawing the countercurrently contacted plant cooling water and refrigerated water from the lower portion of said second zone.

9. A method for preparing high temperature cracked hydrocarbon gases containing easily polymerizable constituents for subsequent high pressure processing comprising cooling the high temperature cracked gases by quenching with water to a temperature of about 900 F., quenching the water quenched gases by direct heat exchange with a cool quench oil, cooling the oil quenched gases by direct heat exchange with cooling water, and further cooling the cooled gases by direct heat exchange with further cooled Water, and subsequently compressing the further cooled gases to a pressure suitable for subsequent processing whereby the temperature of the compressed gases is maintained at a value below that at which solid polymers are formed and deposited on the walls of the processing equipment.

10. A method for preparing high temperature cracked hydrocarbon gases containing easily polymerizable constituents for subsequent high pressure processing comprising cooling the high temperature cracked gases by a water quench to a temperature at least to retard undesired side reactions, quenching these water quenched gases by direct heat exchange with a cool quench oil, cooling the oil quenched gases by direct heat exchange with plant cooling water, and further cooling the latter water cooled gases by direct heat exchange with refrigerated water, and subsequently compressing the further cooled gases to a pressure suitable for subsequent processing whereby the temperature of the compressed gases is maintained at a value below that at which solid polymers are formed and deposited on the walls of the processing equipment.

11. A process for preparing low pressure, high temperature, cracked gases containing ethylene and easily polymerizable hydrocarbons for subsequent processing at a pressure higher than said low pressure and at ambient temperature comprising cooling said high temperature cracked gases by a water quench to a temperature of about 900 F., quenching the water quenched gases by direct heat exchange with a cool quench oil, cooling the oil quenched gases by direct heat exchange with plant cooling water, further cooling the latter cooled gases by direct heat exchange with refrigerated water, compressing the finally cooled gases to such a pressure that the compressed gases issue from the compressor at a temperature of about 250 F., cooling the compressed gases by direct heat exchange with plant cooling water, still further cooling the latter cooled gases by direct heat exchange with refrigerated water, and compressing the still further cooled gases to such a pressure higher than the aforesaid low pressure that compressed gases issuing from this latter compression step issue therefrom at substantially ambient temperature.

References Cited in the tile of this patent UNITED STATES PATENTS

Claims

1. A PROCESS FOR PREPARING LOW PRESSURE HIGH TEMPERATURE CRACKED GASES CONTAINING ETHYLENE AND EASILY POLYMERIZABLE HYDROCARBONS FOR SUBSEQUENT PROCESSING AT A PRESSURE HIGHER THAN SAID LOW PRESSURE AND AT AMBIENT TEMPERATURE COMPRISING THE STEPS OF QUENCHING SAID HIGH TEMPERATURE CRACKED GASES BY DIRECT HEAT EXCHANGE WITH A COOL QUENCH OIL, COOLING THE QUENCHED GASES BY DIRECT HEAT EXCHANGE WITH PLANT COOLING WATER, FUTHER COOLING THE COOLED GASES BY DIRECTED HEAT EXCHANGE WITH REFRIGERATED WATER, COMPRESSING THE FURTHER COOLED GASES TO SUCH PRESSURE THAT THE COMPRESSED GASES ISSUE FROM SAID COMPRESSOR AT A TEMPERATURE OF ABOUT 250* F., COOLING THE COM-