US2779806A

US2779806A - Production of aromatics

Info

Publication number: US2779806A
Application number: US272145A
Authority: US
Inventors: Jr Parkin T Sowden
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1952-02-18
Filing date: 1952-02-18
Publication date: 1957-01-29
Anticipated expiration: 1974-01-29

Description

Jan. 29, 1957 P. T. SOWDEN, JR

PRODUCTION OF AROMATICS Filed Fab. 18, 1952 TO RECOVERY P ROCESS FEED INERT GAS BY PRODUCT COKE INVENTOR.

P. T. SOWDEN,JR.

A TTOEWEYS United States Patent This invention relates to i the productibii 'of "aromatics;

In one"of=its moreispecific aspects, this invention-relates to apr'oce'ss for the productionof aromatics by pyrolysis of light hydrocarbons. In another of its more' specific aspects, -it=relates to new apparatus"for carrying out=the processw In-a'nother of its more specificaspebts, it relate's tea-method ofand apparatus for the production of aromatics-Ebypyrolysis of light hydrocarbons in whioh it is possible-to controlindependently the oper'ation'of 'a soaking'zone and quench zone. i

In conventional cracking processes in which aromatics are produced by pyrolysis of hydrocarbons; a gaseous hydrocarbonfeed is heated in an especially designed furnace after which the heated gases are passed to a soaking chamber wherein furthercracking and polymerization reactions take place. This'soaking chamber has generally consistedof an empty vessel. 7 One of the difliculties experienced in this process is that pai't of the material is broken down to coke and tars; Part of these-materials deposit infthe chamber and another part is carried along with thegas stream and cause difficulties suchas plugged transfer lines and stopped valves. As a result, numerous pl ant s hut downs occur while the carbon and tar is removecllfrom the soalting chamber and other equipment, whicli isiisual-ly done' by burning'the carbon with acontrolledstrearn of air. r i

By the various aspects of this invention, one or more of the fbllowiiig objectswill'b'e obtained.

A n objec t of this invention is an improved method for the pfoduction of area-rates. A further object of this invention' is an improved method for the production ofaromatics by pyrolysis of light hydrocarbons. A further object of this invntioiris to provide new apparatus for the "production of aromatics A still'fiir'the'f o'bj'e'c't o'f this invention is to" pr'ovide' said apparatus in which'it is possible to control independently the soaking and quenching operation's' involved in the cracking process. Further objects will'be apparent to one skilled 'inthe art ou examinationbf the accompanying disclosure.

The drawing presents a flow sheet of a preferred embodiment of'myinve' en. t i n V t l invntionfhydrocarbonsare treated ih the vapor sisting 'principally'of benzene, toluene; and xylene, and a -heavy oil fraction "containing higher members of the aron iatic' ser'ies seen as naphthalene; lnfhitcene, phenanthriief'and higher members; as well as alky'l derivatives of the above compounds! The light oil produced by this process is apprtiximately85"% benzene. Where prior processes have considered coke arid'tar formation-as a detriirient iii the process, Ihavedeveloped a processwherem-a-fomiationer coke is taken advantage of, and this coke is collected asaby-product of the process.

In the proceSsQ tlie hydrocarbon feed is preheated and are allowedto react-in contact with a moving bed of action products are fed to the soakingzonell 'Where the ice coke particles or pellets; These coke particles=serve primarily as a condehsing surface on which heavy hydrocarbons degenerate to coke. This moving bed'aliso serves'to trap'coke ortar particlesand this results in a cleancra ckedgas which will not plug transferwlines and other equipment.

Following soaking; the gases are conductedto'a suitable quench zone wherein undesirable siderea'ctions are prevented. V

The carborior coke from the soaking zone is treatedso as to recover the heat thereinypatt of the carbon can be removed as a by-product, and'the balance recirculated through the system.

Novel features of my invention will become apparent upon consideration of the accompanying drawingwheree in the apparatus is shown in detail. The principalzones of this apparatus consist ofa quench zone 10, a'soaki ng zone 11, and a pellet temperature control zone 12, which may be of any shape but are generally circular in cross section; andare closed at theirupper and lower ends except where inlet and outlet conduits, hereafter discussed, are provided. An elevator, such as gas-lift 13 is pro vided which eittends from a level below the lowermost part of chamber 12 toa levl above the uppermost part of chamber 110, and serves to convey circulating material upwardly. Pressurizer 14 is connected to the lower end portionof gas-lift 13 bymeans of conduit 16, and to theupper end of said gas-lift by means of conduit 17. Solid material conduit 1% connects the upper end piortionof"gas-lift 1'3 and'the'uppe'r end portion of chamber 11), and conduit 19 connects the lower end portion of chairlber 12 with theilowerjend portionof gas-lift 13, conduit 19 "being provided with flow controller '21 and rniovalcoiiduitflzt Conduit'23 extends from the lower endfportion of ch'anibe'rit) to'theupperend portion of chamber llandjco u it 24jproyided with fiow controller 25, eit tendsffrom' flowerend portion'of chambert ll to the "upprendp'ortion of chamber 12. Bypass con duit 26 extends between conduits23 'arid 24 and is pro vided'withmy p renew? controller 27, said controller 27 beingldcafedheaf'the pointat which conduit 26 con nects withcbiidiiit"2 l The fiow coiitrollers are illustrated as starves but slide valves or known types of valves can be used; i

F rna'ce zsis pmvided to prelreat the feed, said'feed being pa'ss'e to the coils29*of said furnace by means of conduit '31. Conduit 32 extends fromthe furnace and dividesinto conduit fiia, communicating with the lower end of zone'11', and conduit 34:; communicating with the upper end of zone: ii -1, said latter conduits being provided with valves '36 and'37. Conduit 38 communicates with the lower end-of zone ll and conduit '39 communicates with the upper end of zone 11, said conduits joining to form conduit 41, said conduit communicating with the lowerend-por'tion'of zone 10. Valves'42 and43 are provided in

conduits

38 and 39, respectively. Conduit 44 extends frofrfthe uppergen'd'portion of zone 10.

Waste heat recovery boiler 46 is provided near zone 12 and is connected to zone 12 by means of conduit 47. Conduit 48 is provided extending into the lower portion ofzone'12.

In the operation of'my process; the hydrocarbon feedstream to be cracked is passed through the coils 29 of furnace 28 where it is preheated. This is essentially a rapid heat transfer process and is conducted at pressure slightly aboveatmospheric;' Thereafter, the heated remajor part of the'reaction takes place, after which they are conducted to que'n'ch zone 10. I prefer to use concurrentflow the soaking zone, i e. passingthe gas into the upper portion of said zone through

conduits

32 and 34,-and utilizing conduits 38'and 4l to convey the products to the quench zone. However, the apparatus is designed so that countercurrent flow can be carried out by passing the products from the furnace 28 to the soaking zone 11 through conduit 33 and removing these products from zone 11 by means of conduit'39. Concurrent flow generally provides better control in the soaking zone.

Coke pellet flow in this process is as follows, starting arbitrarily with quench zone 10. As hereafter described, the pellets supplied to this zone should be cooled to a temperature low enough to quench the products to a temperature so that no further reactions will occur in the apparatus following this zone. From zone the pellets flow downwardly by gravity through conduit 23. A portion of the pellets flow into soaking zone 11 and generally a major portion is by-passed around zone 11 by means of conduit 26. The coke pellets which are passed tothe soaking zone 11 serve primarily as a condensing surface on which heavy hydrocarbons may degenerate to coke. The moving bed also serves to trap coke or tar particles, thus generating a clean cracked gas which Will not foul the transfer lines and subsequent equipment. Coke particles are removed from zone 11 and, in combination with the pellets passed through by-pass conduit 26, flow by gravity into pellet temperature control zone 12. In this zone, the major portion of the heat contained in the coke is removed therefrom. I prefer to remove this heat by direct contact with an inert gas supplied by conduit 48, which subsequently generates steam in an outside heat recovery unit 46. However, the heat may be removed indirectly by water or gas circulation in tubes or other suitable heat transfer surface. This step enables me to control the temperature of the coke pellets supplied to the heating zone.

Thecooled pellets are removed from the lower end of pellet temperature control zone 12 by means of conduit 19 which is connected to the lower end of gas-lift 13. By means of flow controller 21, the amount of coke passed through gas-lift 13 is controlled. By-product coke is removed from line 19 through conduit 22. This coke is utilized as chemical or electrode carbon, or burned as a refinery fuel, as desired.

An important aspect of my invention is by-pass conduit 26 and the advantages in operation which are obtained thereby. This permits control of the amounts of materials in the soaking zone and the quench zone, that is, a large amount of pellets can be circulated through the quench zone so as to provide for rapid quenching, while a much smaller amount of coke is passed into the soaking zone. In this invention, the circulation rate through the soaking zone may be varied at will while circulating a constant amount of material through the quench zone. Without the feature of this by-pass, the rate required for quenching is often too high for optimum soaking conditions. Flow controllers 25 and 27 cooperate to regulate pellet flow. Frequently flow controller 27 is left in full open position and flow controller 25 provides adjustment necessary for proper control of pellet residence time in chamber 11.

An advantage of a quenching zone of this type over the conventional direct oil or water quench is that this quench zone employing the circulating coke enables recovery of the heat which is contained in the gaseous products. Furthermore, as stated above, a cleaner product is obtained as well as the additional product, that is a good grade of petroleum coke. a 7

Should operations require such a low depth of cracking that the net heat of reaction was endothermic, heat could be supplied to the coke by inert gases and the coke would then become a heatingmedium.

The apparatus of this invention can be used for various types of cracking reactions, one of the most important being the cracking of normal butane to produce aromatic hydrocarbons and coke. In order that this invention may be fully understood, the following discussion relates to 4 such a process; the temperatures and pressures being dis closed therein are given by way of explanationand are not to be considered as limiting conditions.

Example A normal butane feed is vaporized and passed through tube cracking furnace 28 under conditions such that substantial quantities of ethylene and propylene are produced. Preferred conditions are atmospheric pressure or a few pounds thereover, a contact time of one second, and an effluent temperature of 1400 F. The furnace effl uent is passed through conduit 34 and into soaking chamberll in concurrent flow with a moving bed of granular coke, at a rate such that a contact time of 24 seconds is obtained. Under these conditions a substantial conversion of olefinic hydrocarbons occurs, accompanied by a release of heat due to the exothermic reactions occurring, and the coke and hyrdocarbons leave the soaking zone 11 by means of conduit 38 at a temperature of about 1500 F. The hydrocarbons are passed into the quench chamber 10 where they flow concurrently through the bed of granular coke and are quenched to about 600 F., said temperature being sufficiently low so that all further reactions are substantially stopped. The products can then be further cooled or condensed by conventional means to a temperature suitable for recovery and purification. Coke pellets withdrawn from the lower portion of the quench zone 10 are divided into two streams; a minor portion, which may be as small as one percent by weight, passes to the soaking chamber and the remainder pass directly to the pellet temperature control zone 12. These coke pellets, which are at a temperature of approximately 1400 F. are combined with the coke pellets from soaking zone 11 and contacted with a cooled inert gas entering said zone through conduit 48. Coke leaves the pellet temperature control zone 12 at a temperature in the neighborhood of 600 F., and the inert gas, which is heated to about 1300 F. is passed through conduit 47 to waste heat boiler 46 for the production of steam.

Typical compositions for the various streams in the process are shown in the following tabulation. This shows the products obtained when operating the above process at a feed rate of 1000 barrels per day.

Furnace Efliuent Soaker Eflluent Component Wt. Per- Lbs/Day Wt. Per- LbsJDay cent cent 7 Heavy Oil 3.1 6, 340 11. 9 24, 350

The treatment conditions, of course, depend upon the particular material being treated. When operating on the specific feed stream mentioned above, I prefer to operate a furnace so that the output gas will have a temperature of 1200 to 1600" F. and more preferably 1400 to 1500 F., and a pressure of 2 to 15 p. s. i. g. Under these conditions, the length of time in the furnace can be one second or less, which eliminates carbon deposition within the tubes of the furnace. The reaction time in the soaking zone is dependent to a very large extent upon the temperature therein. Considering the furnace temperatures stated above, it should be pointed out that at 1400 F. the products will be the same with a 24 second reaction time as those obtained at 1500 and a reaction time of 3 seconds. The pressure in the soaking zone should be approximately the same as that in the furnace.

The coke circulation rate depends entirely uponthe;

1 circulation rate is approximately 25,000 pounds per hour. 1 Thus, it is apparent that I have invented a new process and apparatus for the production of aromatics. A subvprocess can be recovered at a high temperature level, this being due to the fact that heat is transferred from the products to the circulating carbon pellets in the quench zone and in the soaking zone, and the heat is removed from the system by the inert gas stream in zone 12. My process enables me to produce a clean hydrocarbon product and a good grade of petroleum coke.

As many possible embodiments may be made of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. Apparatus for hydrocarbon cracking and reforming comprising a first chamber; a second chamber below said first chamber; a first conduit connecting the lower end portion of said first and the upper end portion of said second chambers; a third chamber below said second chamber; a second conduit connecting the lower end portion of said second and the upper end portion of said third chambers; a third conduit connecting the lower end portion of said first chamber and the upper end portion of said third chamber; an elevator extending from a level below the lower end portion of the third chamber to a level above the upper end portion of the first chamber; a fourth conduit connecting the lower end portion of said third chamber and the lower end portion of said elevator; a product removal conduit communicating with said fourth conduit; a fifth conduit connecting the upper end portion of said elevator and the upper end portion of said first chamber; means for passing fluid heat exchange material through said third chamber; a sixth conduit communicating with one end portion of said second chamber; a heater in said sixth conduit; a seventh conduit connecting the second end portion of said second chamber with the lower end portion of said first chamber; and an eighth conduit extending from the upper end portion of said first chamber.

2. The apparatus of claim 1 in which said elevator comprises a gas lift.

3. The apparatus of claim 1 in which a flow controller is provided in said second conduit.

4. The apparatus of claim 1 in which a flow controller is provided in said third conduit.

5. The apparatus of claim 1 in which the means for passing fluid material through said third chamber comprises a conduit extending into the lower portion of said chamber and a conduit extending from the upper portion of said chamber; and a heat exchanger located downstream of said third chamber.

6. Apparatus for hydrocarbon cracking and reforming comprising a first chamber; a second chamber below said first chamber; a first conduit connecting the lower end portion of said first and the upper end of said second chambers; a third chamber below said second chamber; a second conduit connecting the lower end portion of said second and the upper end portion of said third chambers; a flow controller in said second conduit; a third conduit connecting the lower end portion of said first and the upper end portion of said third chambers;

a flow controller in said third conduit; a gas-lift extending from a level below the lower end portion of said thirdchamber to a level above the upper end portion of the first chamber; a fourth conduit connecting the lower end portion of said third chamber and the lower end portion of said gaslift; a product removal conduit communicating with said fourth conduit; a fifth conduit connecting the upper end portion of said gas-lift and heat load, which is determined by the feed rate and re- ...act1'on conditions. In the above example, where a thousand barrels a day of butane are being treated, the coke the upper end portion of said first chamberyasixth-con duit extending into one end portion of said thirdcham= her; a seventh conduit extending from the other; end

. stantial portion of the heat required or generated in the p i portion of said third chamber; aheat exchangeniii said seventh conduit; aneighth conduit communicating with one end portionof said second chamber; a furnace located in saideighth conduit; a ninthc'onduit connecting the second end portionof said second chamber and the lower end portion of said first chamber; and" a tenth conduit extending from the upper end portion of said first chamber.

7. A method'ofhydrocarbon cracking and reforming comprising introducing relatively cool coke-pellets into aquenching"zone;"gravitating said pellets from thelower portion of said zone; dividing said pellets into first and second portions; passing the first portion into the upper portion of a soaking zone; passing a hydrocarbon stream in gaseous form which has been preheated to reaction temperature into said soaking zone; thereafter passing a resulting product stream from said soaking zone to said quenching zone; removing the quenched gaseous product from the upper end of said quenching zone; gravitating said coke pellets from the lower end of said soaking zone; combining said first and second portions of said pellets; passing said combined stream of pellets into a pellet temperature control zone; cooling said pellets in said zone with a heat exchange fluid; gravitating said pellets from the lower portion of said pellet temperature control zone; elevating said pellets from the lower end portion of said pellet temperature control zone to an upper end portion of said quenching zone; and removing a portion of said pellets as a product of the process.

8. A method of hydrocarbon cracking and reforming comprising introducing coke pellets at a temperature of approximately 600 F. into a quenching zone; gravitating said pellets from the lower portion of said zone; dividing said pellets into first and second portions; passing the first portion into the upper portion of a soaking zone maintained at a temperature of from 14-00" F to 1500 F.; passing a hydrocarbon stream in gaseous form which has been preheated to a temperature of approximately 1400 F. into said soaking zone; passing a resulting gaseous product stream from said soaking zone to said quenching zone; removing a quenched gaseous product from the upper end of said quenching zone; gravitating the coke pellets from the lower portion of said soaking zone; combining said first and second por-- tion of said pellets; passing said combined stream of pellets into a pellet temperature control zone; cooling said from the lower portion of said pellet temperature control zone; introducing said pellets into the lower portion of a gas-lift zone; lifting said pellets in said zone; from which zone said pellets are passed to said quenching zone, thus completing a pellet cycle; and removing a portion of said pellets as a product of the process.

9. The method of claim 7 in which heat is recovered from the heat exchange fluid which is heat exchanged with the pellets in said pellet temperature control zone.

10. A method of hydrocarbon cracking and reforming comprising introducing coke pellets at a temperature of approximately 600 F. into a quenching zone; gravitating said pellets from the lower portion of said zone; dividing said pellets into first and second portions; passing the first portion into the upper portion of a soaking zone maintained at a temperature of from 1400' F. to 1500 F.; passing a hydrocarbon stream'in gaseous form which has been preheated to a temperature of approximately 1400 F. into said soaking zone; passing a resulting gaseous product stream from said soaking zone to said quenching zone; removing a quenched gaseous product from the upper end of said quenching zone; gravitating the coke pellets from the lower portion of said soaking zone; combining said first and second portion of said pellets;

passing said combined stream of pellets into a pellet temperature control zone; cooling said pellets to a temperature of approximately 600 F. by heat exchange with an inert gas; gravitating said pellets from the lower portion of said pellet temperature control zone; introducing said pellets into the lower portion of an elevating zone; lifting said pellets in said elevating zone, from which zone said pellets are passed to said quenching zone. thus completing a pellet cycle; and removing a portion of said pellets as a product of the process.

References Cited in the file of this patent UNITED STATES PATENTS 2,389,636 Ram-seyer Nov. 27, 1945 55 Happel Apr. 13, 1948 Simpson Sept. 7, 1948 Huff Mar. 8, 1949 Crowley Apr. 5, 1949 Utterback et al. July 26, 1949 Arnold Nov. 1, 1949 Crowley Dec. 6, 1949 Johnson Jan. 3, 1950 Garbo Oct. 24, 1950 Ardern July 24, 1951 Quigg et al. Oct. 23, 1951

Claims

1. APPARATUS FOR HYDROCARBON CRACKING AND REFORMING COMPRISING A FIRST CHAMBER; A SECOND CHAMBER BELOW SAID FIRST CHAMBER; A FIRST CONDUIT CONNECTING THE LOWER END PORTION OF SAID FIRST AND THE UPPER END PORTION OF SAID SECOND CHAMBERS; A THIRD CHAMBER BELOW SAID SECOND CHAMBER; A SECOND CONDUIT CONNECTING THE LOWER END PORTION OF SAID SECOND AND THE UPPER END PORTION OF SAID THIRD CHAMBERS; A THIRD CONDUIT CONNECTING THE LOWER END PORTION OF SAID FIRST CHAMBER AND THE UPPER END PORTION OF SAID THIRD CHAMBER; AN ELEVATOR EXTENDING FROM A LEVEL BELOW THE LOWER END PORTION OF THE THIRD CHAMBER TO A LEVEL ABOVE THE UPPER END PORTION OF THE FIRST CHAMBER; A FORTH CONDUIT CONNECTING THE LOWER END PORTION OF SAID THIRD CHAMBER AND THE LOWER END PORTION OF SAID ELEVATOR;A PRODUCT REMOVAL CONDUIT COMMUNICATING WITH SAID FOURTH CONDUIT; A FIFTH CONDUIT CONNECTING THE UPPER END PORTION OF SAID ELEVATOR AND THE UPPER END PORTION OF SAID FIRST CHAMBER; MEANS FOR PASSING FLUID HEAT EXCHANGE MATERIAL THROUGH SAID THIRD CHAMBER; A SIXTH CONDUIT COMMUNICATING WITH ONE END PORTION OF SAID SECOND CHAMBER; A HEATER IN SAID SIXTH CONDUIT; A SEVENTH CONDUIT CONNECTING THE SECOND END PORTION OF SAID SECOND CHAMBER WITH THE LOWER END PORTION OF SAID FIRST CHAMBER; AND AN EIGHT CONDUIT EXTENDING FROM THE UPPER END PORTION OF SAID FIRST CHAMBER.

7. A METHOD OF HYDROCARBON CRACKING AND REFORMING COMPRISING INTRODUCING RELATIVELY COOL COKE PELLETS INTO A QUENCHING ZONE; GRAVITATING SAID PALLETS FROM THE LOWER PORTION OF SAID ZONE; DIVIDING SAID PALLETS INTO FIRST AND SECOND PORTIONS; PASSING THE FIRST PORTION INTO THE UPPER PORTION OF A SOAKING ZONE; PASSING A HYDROCARBON STREAM IN GASEOUS FORM WHICH HAS BEEN PREHEATED TO REACTION TEMPERATURE INTO SAID SOAKING ZONE; THEREAFTER PASSING A RESULTING PRODUCT STREAM FROM SAID SOAKING ZONE TO SAID QUENCHING ZONE; REMOVING THE QUENCHED GASEOUS PRODUCT FROM THE UPPER END OF SAID QUENCHING ZONE; GRAVITATING SAID COKE PALLETS FROM THE LOWER END OF SAID SOAKING ZONE; COMBINING SAID FIRST AND SECOND PORTIONS OF SAID PELLETS; PASSING SAID COMBINED STREAM OF PELLETS INTO A PELLET TEMPERATURE CONTROL ZONE; COLLING SAID PELLETS IN SAID ZONE WITH A HEAT EXCHANGE FLUID; GRAVITATING SAID PELLETS FROM THE LOWER PORTION OF SAID PELLET TEMPERATURE CONTROL ZONE; ELEVATING SAID PELLETS FROM THE LOWER END PORTION OF SAID PELLET TEMPERATURE CONTROL ZONE TO AN UPPER END PORTION OF SAID QUENCHING ZONE; AND REMOVING A PORTION OF SAID PELLETS AS A PRODUCT OF THE PROCESS.