Nov. 5, E946. A. J. L. HUTCHINSON l 2,410,583 SEPARATION oF HYDRATE -FoRMING> COMPONENTS 0F GAsEoUs MIXTURES Filed July l0, 1945 êQLIÈSÃ hn@as.A. I 2 Sheets-Sheet 1 ov. 5, 1946. l A. J. l.. vl-«zUTcl-nNsoN 29430533 SEPARATION OF HYDRATE-FORMING~ COMPONENTS OF GASEOUS MIXTURES Filed July l0, 1943 2 Sheets-Sheet 2 v Patented Nov. 5, 1946 2,410,583 UNITED STATES PATENT ortica 2,410,583 SEPARATION 0F HYDRATE-FORMING COM PONENTS 0F GASEOUS MIXTURES Arthur J. L. Hutchinson, San Marino, Calif., as signor to The Fluor Corporation,> Ltd., Los Angeles, Calif., a corporation of California Application July 1o, 194s, serial No. 494,164 10 Claims. (ol. 26o-_676) 2 This invention has to do with improved proc esses for the separation from normally gaseous mixtures containing one or more hydrate-form hydrate-forming zone, and thus maintained in a state of continuous circulation between the two zones. ing components, of one or more components in Another object of the invention is to provideA capable of forming hydrates, or at least which do not form hydrates under the conditions of treatment in the process. More particularly the invention is directed to the separation from hy for a high degree of separation of the inert com ponents from the gas, by the formation of a hy drate phase characterized by `its readiness of formation, stability and low vapor pressure, all drocarbon gases such as natural gas or reñnery of which properties tend to permit segregation tail gas, of undesirable or inert gases, of which l() out of the gas of the maximum percentages of nitrogen and hydrogen may be taken as typical. its hydrate-forming components. In this respect, the invention contemplates treatment of the hy drocarbon in the presence of an additive, to pro This application is a continuation-in-part of Hutchinson application Serial No. 392,186, filed May 6, 1941, on Fractionation of hydrate-forming duce what may be referred to generally as a mixed hydrate of the hydrocarbons and additive, l hydrocarbons, and Hutchinson application Serial No. 407,036, ñled August 14, 1941, on System for characterized by its readiness of formation and considerably lower vapor pressure, and therefore greater stability, than the pure hydrate of the forming and storing hydrocarbon hydrates. Generally speaking, the present process in volves phase segregation of hydrate-forming hy drocarbon components, from inert or- non-hy same hydrocarbon at the same temperature. 20 drate-forming components, by converting the former to their solid hydrates and separating the non-hydrated fluid phase. The invention broadly contemplates the use of any suitable additive. capable of forming with hydrate-'forming hydrocarbons, a mixed hydrate, One basically dis or hydrate complex, as hereinafter designated, tinctive aspect of the process, is the method whereby the hydrates may be subjected to con 25 the mixed hydrate having the property of sub stantially lower vapor pressure than the vapor tinuous dissociation in a single zone receiving a pressure of the hydrate of the hydrocarbon com stream of the hydrates, with the end result that ponent of the mixed hydrate. Suitable additives fall within the general class of halogenated hy the raw gas being Atreated undergoes continuous separation into two continuously ñowing streams of its hydrocarbon ' and inert components. 30 drocarbons which are liquid at 0° C. and are Specifically, the invention contemplates subject ing the gas in a conversion zone and in the pres ence of water, to pressure and temperature con ditions causing hydration of the component or components to be hydrated, separating the non 36 hydrated gas, and continuously transferring the hydrates to a suitable decomposition zone where in the hydrates undergo continuous dissociation and reconversion into gas. ' Transference'of the hydrates from the conver chloride, bromoform, chloroform, ethylene di chloride, methylene chloride, methyl iodide, methylene iodide, and the tri-halogen compounds For purposes of de 40 scription, carbon tetrachloride will be referred sion zone to the decomposition zone may be facili tated by the use of a hydrate carrier ñuid, which ' in the broad aspects of the invention may be> any suitable ñuid medium capable of entraining and aiding the transference of the hydrate crystals. I may employ as the carrier ñuid, re sidual liquid remaining after the hydration, or capable of forming with a hydrate-forming'hy drocarbon under proper temperature and pres sure conditions, a mixed hydrocarbon-halo genated hydrocarbon hydrate. Included among such halogenated hydrocarbons are carbon tetra of methane andV ethane. to hereinafter as the additive, with the under standing that it is to be regarded as typical of suitable additives in general, and of the- class consisting of the halogenated hydrocarbons. The additive, e. g. carbon tetrachloride, may be introduced, as later described, to the hydrate forming zone in which it is converted. together a non-aqueous liquid, such as kerosene or other with the hydrocarbon, into a mixed hydrate. The mineral oil fraction, to particular advantage be exact nature and composition of the resulting cause of its further utility as a dispersing medium 50 hydrate complex is not known at present, and l for water particles to be consumed in the hydra- tion, and also for the later described additive, if used. After separation from the -hydrates or consequently the expression “mixed hydrate” is used as a term of designation, rather than of definition, and is not intended _to be limitative hydratable components. as in the decomposition with respect to any particular form or composi zone, the carrier liquid may be returned to the 55 tion of the hydrate complex. That composition 2,410,583 4 may lbe in the nature of 'a depressed vapor vpres sure mixture of the two hydrates, or of a double hydrate of the hydrocarbons and carbon tetra-' chloride, or it may involve a solution of some of the hydrocarbon in the carbon tetrachloride hy drate, or a solution of some of the carbon tetra chloride in the hydrocarbon hydrate. Whatever its exact composition may be, the mixed hydrate has the important property oi.' low vapor pres sure, of which advantage may be taken for the purposes of the present process. The invention contemplates various additional particular features of operation, such as partial hydration oi' the hydrocarbon components of the gas alone, followed by hydration of unconverted hydrocarbons together with the additive. Con gated into hydrated hydrocarbon components which, together with any higher boiling non hydrate-forming hydrocarbon components, are continuously withdrawn from the base of the column through line I3, and gaseous inert con stituents which are separately and continuously withíi‘rawn from the top of the column through line . The hydrate formed in column-I I, and which preferably is a mixed hydrocarbon-carbon tetra chloride hydrate, is continuously discharged in a stream of the carrier liquid, e. g. kerosene, through lines I3, I3a and heat exchanger I5 into the hydrate decomposition zone I6. The pressure on the hydrates may be reduced at the discharge side of valve I'I should it be desired to facilitate dissociation of the hydrates by virtue of the re templated also are methods for the recovery of duced pressure. Ordinarily, however, it may be the additive from both the separated hydrocarbon desired to decompose the hydrates at increased and inert gas streams, and return of the re 20 pressure in order to permit absorption recovery covered additive to the hydrate-forming zone. of the carbon tetrachloride at pressures suñl All the objects and features of the invention ciently high for most eñicient operation. Ac will be more fully explained, and understood to cordingly, 'the hydrate-carrier stream may be better advantage from the following descrip forced by pump P into zone I6, wherein the tion of a'typical system 'illustrated by the ac hydrate dissociation may occur under any desired companying drawings, in which: Fig. 1 is a schematic layout, in flow sheet form, While the hydrate decomposition zone I6 may illustrating a typical system embodying the in be of any suitable type and form, it is preferred vention; and pressure. Fig. 2 is a View, largely diagrammatic, showing - Y to use a vertically extended column to more effec the hydrate-forming zone in vertical section, and 30 tively remove hydrate-forming hydrocarbons and carrier liquid from the gas going to the outlet including also a secondary hydrate decomposition line I8. Heat may be supplied to the column I6 zone to be used if required. It will be understood that the gas fed to the ' in any suitable manner, as by a bottom coil heater I9, to eiîect complete dissociation of the system under pressure through line Ill, may con sist of any of various mixtures of one or more 35 hydrate. The residual carrier liquid is dis charged through line 20 and exchanger I5 for hydrate-forming components, with one or more recirculation to the hydrate-forming zone I‘I, inert constituents which either are incapable of after again mixing the carrier with water and forming hydrates under any conditions, or under the particular conditions existing in the hydrate carbon tetrachloride. Any suitable methods and forming zone. As illustrative, assume that the 40 apparatus Imay be employed at 2| for mixing system is to be operated for extracting from a _ and proportioning4 the carrier liquid, water and natural gas containing hydrate-forming hydro carbon tetrachloride to be recirculated, and for supplying any necessary make-up carrier, water carbons included in the C1, C2, and Ca range, an and carbon tetrachloride. _It is contemplated inert fraction containing a high percentage of nitrogen, the nitrogen content for example run 45 that the resulting mixture may be in the form of an emulsion formed by suitably mixing and ning as high as from 10 to 15% >by volume of agitating the carrier liquid, water and carbon the natural gas. In order to reduce the heat load tetrachloride together _with an emulsifying agent, (resulting from the heat of hydrate formation) for example dioctyl sodium sulfo succinate, known on the hydrate-forming column II, the gas first may be passed through one or more coolers I2 ' commercially as "Aerosol OT.” The mixture, or emulsion, is discharged by pump 22 through line within which the gas temperature may be lowered as desired. ‘Within column II, the gas is con 4 23 and cooler 24 to the top of the hydrate tacted with Water, and preferably also with a non-aqueous carrier liquid and a hydrate forming column II. Where operation of the co1 forming additive, under temperature and pressure ' location of a carrier liquid-water mixture, all as later explained, such mixture, containing no carbon tetrachloride, may be supplied from the conditions causing conversion to their solid hy drates of substantially all, or at least a greater portion of the hydrate-forming components of the gas. 'I‘he more particular details and aspects umn requires the introduction at an intermediate mixing and proportioning plant 2I by pump 26 through line 21. of the hydrate formation within the column II, The _ hydrocarbon gas leaving column I6 will be described later with reference to Fig. 2. through line I8, and containing water and carbon .At this point itvwill suñ‘lce to observe that the tetrachloride vapors, may be passed directly gas and water may be contacted within the through line 28 to the extractor 29, or the gas column II under any suitable temperature and may be subjected to partial condensation in con pressure conditions at which the desired degree 65 denser 30 to provide a suitable amount of con of hydrate formation will occur, for example at densate to be returned from accumulator 3I a temperature between 35 and 45". F. and under through line 32 and pump 33 to the column I6 as pressure between 400 and 650 pounds per square reñux, the uncondensed gas passing through line inch. The presence of the additive, if used, may 34 connecting with the extractor feed line 28. lower very considerably the required pressure 70 'I'he carbon Atetrachloride content of the hydro for the hydrate formation at a given temper carbon gas stream is extracted in column 29 by ature, or conversely, permit the Vuse of consider intimately vcontacting the rising gas stream ably high temperatures to effect the hydrate therein with a downwardly flowing absorption formation under a given pressure. As a result liquid, such as a fairly high boiling mineral oil of its treatment in column II, the gas is segre fraction, in which the carbon tetrachloride is re 2,410,583 5. covered by absorption. The extractor column to be sent to the mixing and proportloning plant may be operated at any suitable pressure and 2 I. oil rate to eiîect solution from the gas phase of The non-hydrated gas rising from the bottom the carbon tetrachloride vapor. The purified hy section of the column 60 flows through the baiiled drocarbon gas is taken from the column through el vapor neck 1I extending above plate 12, into the line 35 for such disposal as may be desired. upper section of the column wherein the gas is Water condensate accumulating within the bot contacted with a down-flowing stream of mixed tom of the extractor, may be intermittently or or emulsifìed non-aqueous carrier liquid, water continually drawn olf through ‘line 36. and additive such as halogenated hydrocarbon, The inert gas, containing some carbon tetra 10 e. g. carbon tetrachloride. The latter mixture or ' chloride and withdrawn from the hydrate-form emulsion entering the column through line 25 ing zone through line I4, may be similarly given and cooler 13 may contain the carrier, Water and an absorption oil treatment for extraction of the . carbon tetrachlorite in any desired proportions, carbon tetrachloride. Accordingly, the inert gas so long as the water present in the column is stream may be introduced from line I4 into a, sufficient for formation of the mixed hydrate, and second extractor column 31 wherein the gas is. the quantity of carrier liquid is adequate for en contacted with down-flowing absorption oil. trainment and transference of the formed hy Carbon tetrachloride-free gas is taken from the drates. The carbon tetrachloride content of the top ofthe column through line 38. Water ac mixture or emulsion is not critical and may run cumulating in the bottom of the column is with 20 in the neighborhood of 10% to 90%, depending drawn through line 39. upon various considerations including the quan The absorption oil streams with their absorbed tity and composition of the hydrate-forming hy carbon tetrachloride, are withdrawn from the ex drocarbons in the gas being treated. Intimate tractors 29 and 31 through lines 39a and 40 to be association of the gas and liquid mixture intro taken through line 4 I, heat exchanger 42 and line duced through line 25, results in the formation 43 to a still 44 supplied with heat as by the bottom within the upper section of the column of what coil 45, and also, if desired. by live steam through has been termed the mixed hydrocarbon-carbon line 45|. In still 44 the absorption oil is heated tetrachloride hydrate. The latter forms at stages suiliciently to vaporize the carbon tetrachloride, or on the bubble trays progressing upwardly the latter passing through li'ne 46 to condenser within the column, and the formed hydrate is 41 and the condensate accumulator 48. A por continuously flushed downward through the tion of the condensate may be returned through trays in the carrier liquid into vchamber 14 from line 49 and pump 50 to the top of the still as which the hydrates are transferred through line I3 to the decomposition zone I6. reflux. From accumulator 48 the carbon tetra chloride is discharged by Dump 5I «through line i In the upper section of the column, the gas is 52 to the mixing and proportioning plant 2 I. The effectively depleted of its hydratable hydrocar stripped absorption oil leaving the bottom of the bon content by reason of the hydrate-forming still through line 53 is forced by pump '54 through load on this section of the column having beeny exchanger 42, line 55, cooler 56 and the branch reduced by and to the extent of the hydrates lines 51 and 58 into the extractor columns 29 and forming in the bottom section of the column. 31. Complete final hydration of the hydrocarbons is Further consideration now may be given the further and effectively assured by reason of the operation of the hydrate-forming column II and relative ease of formation of the mixed hydro the methods contemplated for securing high per carbon and carbon tetrachloride hydrate, and its vccrmparatively low vapor pressure and resultant centage removal, in the form of their hydrates, of stability. the hydrate-forming componentsl of the gas Reference previously has been made to. pre treated. Referring to Fig. 2, the hydrate-forming zone I I may consist essentially of a fractionating column 60 containing a vertical series of bubble trays conventionally illustrated at ISI~ According to the method of operation specifically illustrated, the precooled gas introduced to the bottom of the column through line III rises through the lower series of bubble trays 6I in intimate contact with a mixture or emulsion of the non-aqueous carrier liquid and water Dre-cooled in cooler 62 and introduced to an intermediate location in the cooling of the gas, as well as the water and car rier liquids, to compensate for heat of hydrate formation.f Such heat may further be compen sated by the withdrawal of heat of hydrate for mation from within the column itself. Typically, the several bubble trays 6I may carry cooling coils 15 to which a ‘suitable refrigerant or cooling fluid is supplied from line 16 through manifold 11 and the valved branches 18, the valves 19 being individually adjustable to permit selective with this carrier and water stream produces par temperature ,control on any of the trays. After passage through the coils 15, the cooling fluid tial hydration of the hydrate-forming hydrocar enters the outlet manifold to be discharged column through line 63, Co-mingling of the gas through line 8|. bon components of the gas, the resulting hy According to the method just described, hydro drates being entrained in the carrier liquid and carbon hydrates are formed in the lower section carried downwardly through the usual overflow of the column, and the mixed lhydrocarbon-car pipes 64 to the bottom of the column. The hy bon tetrachloride hydrate is formed in the upper drates thus are transferred in the carrier liquid section of the column, by selective introduction Y through line 65 (and by pump P’ if desired), and of the two aqueous liquids through lines 63 and the heat exchanger 66 into a hydrate decomposi 25 and separate withdrawal of the hydrates tion zone 61 supplied with heat by the bottom through lines 65 and- I3. If desired, the entire coil 68. In column 61 the hydrates are dissoci column may be used for the formation of the ated to release the hydrocarbon gas for removal .mixed hydrate, in which vevent plate 12 may be and such use as may be desired, through line 69. replaced by a bubble cap tray 6I, the water-car If desired, the latter may connect into line 35 of rier inlet line 63 dispensed with, and the com Fig. 1. The residual carrier liquid and water may be withdrawn through line 10 and exchanger. 66 75 position of the stream introduced to the top of the column through line 25, adjusted to contain asiduos suiiicient carbon tetrachloridev and water for ' conversion of all the hydrate-forming hydrocar temperature, separating said gaseous. inert con stituent from the mixed hydrate, transferring bons of the gas to a mixed hydrocarbon-carbon tetrachloride hydrate. When- the column is op erated‘in this manner, the mixed hydrate with drawn through line 65, instead of through line I3, may he taken through the valved line 83 into line I3 for delivery to the decomposition zone I6, all as illustrated in Fig. 1. I claim: said mixed hydrate from said conversion zone to a decomposition zone, therein heating and dis "sociating the hydrate, recovering said additive from the products of the hydrate dissociation, and returning the additive to the conversion zone. 5. The method of treating a gas comprising a - _ 8 carbon components alone and at corresponding l0 mixture of hydrate-forming hydrocarbon com » 1. The method of treating a gas comprising a ponents and an inert non-hydrate-forming con mixture of hydrate-forming hydrocarbon com ponents and an inert non-hydrate-forming con-_ stituent to separate said inert constituent, that includes contacting said gas with Water and a stituent to separate said inert constituent, that hydrate-forming halogenated aliphatic hydro includes contacting said gas with water and a halogenated aliphatic hydrocarbon in a conver sion zone under temperature and pressure con ditions causing formation of a mixed hydrate ci' carbon additive in a conversion zone under tem said hydrocarbon components and halogenated hydrocarbon, said mixed hydrate having sub perature and pressure conditions causing forma stantially lower vapor pressure than the hydrate '_ tion of a mixed hydrate of said ìhydrocarbon of said hydrocarbon components alone and at components and additive, said mixed hydrate corresponding temperature, separating said gas having substantially lower vapor pressure than eous inert constituent from the mixed hydrate, the hydrate of said hydrocarbon components transferring said mixed hydrate from said con alone and at corresponding temperature, sepa version zone to a second zone and therein dis rating said inert constituent from the mixed hy drate, continuously removing the hydrates from 2.5 sociating the hydrate to vaporize the halogenated hydrocarbon and said hydrocarbon components, said zone and dissociating the removed hydrates, and recovering the halogenated ¿hydrocarbon recovering said additive, and returning the addi from the resulting vapors. _ tive to the conversion zone. ' 6. The method of treating a gas comprising a 2. The method of treating a gas comprising a vmixture of hydrate-forming hydrocarbon compo 30 mixture of hydrate-forming hydrocarbon com ponents and an inert non-hydrate-forming con nents and an inert non-hydrate-forming con stituent to separate said inert constituent, that stituent to separate said inert constituent, that, includes contacting said gas with water intimate ly mixed with a non-aqueous liquid and a hy includes contacting said gas with water and a halogenated aliphatic hydrocarbon in a conver sion zone under temperature and pressure con ditions causing formation of a mixed hydrate of said hydrocarbon components and halogen drate-forming halogenated aliphatic hydrocar bon additive in a conversion zone and under tem perature and pressure conditions causing forma tion of a mixed hydrate of said hydrocarbon com ated hydrocarbon, said mixed hydrate having ponents and additive, said mixed hydrate having substantially Alower vapor pressure than the hy drate of said hydrocarbon components alone at corresponding temperature, and separating said inert constituent from the mixed hydrate, con tinuously removing the hydrates from said zone substantially lower vapor pressure than the hy 40 drate' of said hydrocarbon components alone and and dissociating the removed hydrates, recover 45 ing said additive, and _returning the additive to at corresponding temperature, separating said gaseous inert constituent from the mixed hy drate, transferring said mixed ‘hydrate from said conversion zone to a second zone and therein dis sociating the hydrate to vaporize the halogenated hydrocarbon and said hydrocarbon components, extracting the halogenated hydrocarbon from the resulting vapors in absorption oil, heatingthe absorption oil to vaporize the halogenated hydro carbon therefrom, and condensing the halogen the conversion zone. 3. The method of treating a gas comprising a mixture of hydrate-forming hydrocarbon com ponents and an inert non-hydrate-forming con 50 ated hydrocarbon vapors. « stituent to separate said inert constituent, that 7. The method of treating a gas comprising a includes contacting said gas with Water and car mixture of hydrate-forming hydrocarbon com bon tetrachloride in a conversion zone under ponents and an inert non-hydrate-forming con temperature and pressure conditions causing for stituent to separate said inert constituent, that mation of a mixed hydrate of said hydrocarbon includes contacting said gas wtih Water and a components and carbon tetrachloride, said mixed hydrate having substantially lower vapor pres sure than the hydrate of said hydrocarbon com ponents alone at corresponding temperature, and vaporizable halogenated aliphatic hydrocarbon additive in a conversion zone under temperature and pressure conditions causing formation of a separating said gaseous inert constituent from 60 mixed hydrate of said hydrocarbon components and additive, said mixed hydrate having substan the mixed hydrate, continuously removing the tially lower vapor pressure than the hydrate of hydrates from said zone and dissociating the re moved hydrates, recovering said additive, and i said hydrocarbon components alone and at cor responding temperature, separating said Ygaseous returning the additive to the conversion zone. 4. The method of treating a gas comprising a 65 inert constituent from the mixed hydrate, and contacting the separated gas with absorption oil mixture of hydrate-forming hydrocarbon com to extract therefrom the additive carried by 'the ponents and an inert non-hydrate-iorming con gas from the conversion zone. stituent to separate said inert constituent, that 8. The method of treating a gas comprising a includes contacting said gas with water and halogenated aliphatic hydrocarbon additive in a 70 mixture of hydrate-forming hydrocarbon compo nents and an inert non-hydrate-forming con conversion zone under temperature and pressure stituent to separate said inert constituent, that conditions causing formation vof a mixed hydrate includes treating said gas to partially hydrate of said hydrocarbon components and additive, said hydrate-forming components, then contact said mixed hydrate having substantially lower ing the residual gas wtih water and a hydrate vapor pressure than the hydrate of said hydro 75 forming halogenated aliphatic hydrocarbon ad 2,410,588 10 _ditive under temperature and pressure conditions causing formation of a mixed hydrate of the hy drocarbon components and additive, said mixed hydrate, dlssociating the mixed hydrate, and re covering said additive from the products of the hydrate dissociation. hydrate having substantially lower vapor pres 10. The method of treating a gas comprising a mixture of hydrate-forming hydrocarbon com ponents and an inert non-hydrate-forming con stituent to separate said inert constituent, that sure than the hydrate of said hydrocarbon com ponents alonev and at corresponding temperature, separating said inert constituent from the mixed hydrate, dissociating the mixed hydrate, and re includes treating saidegas to partially hydrate said hydrate-forming components, then contact covering saidadditive from the products of the hydrate dissociation. 9. The method of treating a gas comprising a mixture of hydrate-forming- hydrocarbon com ponents and an inert non-hydrate-forming con 10. ing the residual gas with water and carbon tetra chloride under temperature and pressure condi tions causing formation of a mixed hydrate of the hydrocarbon components and carbon tetra stituent to separate said inert constituent, that chloride, said mixed hydrate having substantially includes treating said gas to partially hydrate lower vapor pressure than the hydrate of said said hydrate-forming components, then contact 15 hydrocarbon components alone and at corre ing the residual gas with water andI a halogen sponding temperature, separating said inert con ated aliphatic hydrocarbon under temperature stituent from the mixed hydrate, heating and dis and pressure conditions causing formation of a sociating the hydrates producedrby said partial mixed hydrate of the hydrocarbon components hydration of said components, heating and dis 20 and halogenated hydrocarbon, said mixed hy sociating the mixed hydrate, and separating car drate having substantially lower vapor pressure bon tetrachloride from the vapors resulting from than the hydrate of said hydrocarbon compo dissociation of the mixed hydrate. nents alone and at corresponding temperature, separating said inert constituent from the mixed ARTHUR J. L. HUTCHINSON.