Патент USA US2406748код для вставки
sept. 3, 1946. 2,406,748 N. L. DlcKlNsoN DESALTING 01?’ HYDROCARBON OÍIÍLS~ Filed Dec. 29, 1943 NJ?, ' ' In vem‘dr: l Norman L. Dickin‘s‘on BSN Afforney i V Patented Sept. 3, i946 2,406,748 . UNITED STATES PATENT «- OFFICE 2,406,748 Y nnsAL'rrNG oF HrDRocanBoN oiLs lNorman L. Dickinson, Baskîng Ridge, N. J., as signor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application Decembeiï 29, 1943, serial No. 516,057 5 Claims. (Cl. 196-5) . ~ 1 2 A extremely important consideration in catalytic This invention relates to the desalting of hydro conversion processes and the frequent replace carbon oils and it pertains more particularly to the desalting of reduced crudes for the prepara i ment of catalyst because of salt contamination tion of charging stock to catalytic cracking proc esses. Many crude petroleum oils contain large 5 Would be economically prohibitive. The problem of removing salt from crude pe troleum oils has confronted the industry from its amounts of salts, particularly sodium chloride, very beginning and enormous amounts of re calcium chloride and magnesium chloride. The search have been conducted in an effort to solve amount Voi such salts varies with the crudes, Some this problem. Numerous processes have been pro crudes containing only traces of salt, others con- 10 posed and some of them used with varying de taining about .0l to .2 pound per barrel and some grees of- success but all of them are expensive containing as much as 5 pounds or more per barand for the most part they do not reduce the rel.` Thesalt content of typical Mid-Continent crudes is usuallyV within the approximate range salt content to the extent suliicient for charging stocks in catalytic cracking processes. An object of .04 to .l5 pound per barrel. Since thisr salt is 15 of my invention is to provide an improved method largely concentrated in the residuum on distillaand means for removing salt from oils and par tion and the residuum or reduced crude is fre'ticularly from reduced .crudes which method will quently 50% to 15% of the total crude it will be be characterized by lower capital investment costs seen that the amount of salt in the residuum may and operating costs than any processes heretofore range from about 0.1 to `1 pound per barrel even 20 known. A further object is to obtain higher yields in the case of Mid-Continent crudes and may be of desalted charging stocks from reduced crudes from .5 to 5 or more pounds per barrel in the case than could be obtained by any other known'proc of crudes initially higher in quantities of salt. ess. A further object is to provide a desalted An object of my invention is to provide an imcharging stock of higher quality and speciñcally proved method and means forremoving salt from 25 to avoid the existence of cracking conditions in such oils and particularly from such reduced the desalting ystep so that no low octane number crudes. gasoline will be produced and so that the value The salt removal problem is particularly aggraof the charging stock will not be otherwise im vating in the preparation of charging stocks for paired. ' è catalytic cracking processes. Heretofore catalytic 30 A further object is to remove along with the cracking has been eiïected only on distillate oils salt certain high molecular Weight substances or the vaporizable portions of reduced crudes. It which are deleterious' in catalytic cracking oper is impossible'to effect complete vaporization of reations but which may serve a useful purpose for duced crudes Without carbonization and if such other uses even in the presence of removed salt. vaporization is effected by thermal means it re- 35 Other objects Will be apparent as the detailed 'suits in the production of loW boiling oils of undesirably low knock rating, i. e. gasolines having description of the invention proceeds. I have discovered that when a reduced crude of an A. S. T. M. octane number of the order of 55 high salt content is admixed With propane in to 60. In order to vavoid this undesirable thermal k amounts of about 3 to 5 liquid volumes of propane cracking oi residual cracking stocks it has been 40 per volume of reduced crude, heated to a tem proposed to inject these stocks directly into a perature Within the approximate range of 140jto catalytic cracking reactor to'which the necessary 185° F. under sufñcient pressure to prevent va heat for conversion is supplied by other means. porization of the propane, and introduced into an Provision can be made for burning the additional `eii‘icient settling zone which is likewise main carbonaceous deposits which are laid down in 45 tained under sufficient pressure to prevent pro such operations but the accumulation on the catpane vaporization, the salt can be carried out of alyst of inorganic salts from salt-bearing oils the solution With other propane insoluble mate ruins the catalysts. An> object of my invention rials which are present in the reduced crude and is t0 provide a method and means for the cata- Withdrawn as a separate stream from the base of lytic cracking of such heavy reduced crudes of 50 the settling zone. While propane is the preferred high salt content Without «formation of low antisettling agent for this desalting operation, other knock gasolines and without deleteriously afiectnormally gaseous hydrocarbons or mixtures ing the .activity of the catalyst.r The importance thereof may be employed, higher temperatures of safeguarding catalyst activity can not be over- and lower pressures being used in the case of bu 'emphasized because the cost of the catalyst isan 55 tane and lower temperatures and higher pressures 2,406,74s 4 3 distributed in streams flowing between these in the case of ethane. The normally gaseous hy drocarbons should preferably be saturated al baflles so that the baffles do not impede flow but though the presence of oleflns is not as objection do avoid possible turbulence and provide surfaces on which settled droplets may coalesce and run able in this process as in the process for producing lubricating oils by conventional propane deas 5 down to the base of the settler without inter fering with the settling operation. By using such phalting methods. The amount of normally gas sloping baliles each particle only has to settle a eous hydrocarbon employed should be Within rather closely deiined limits which in the case of propane are from 3 to 5 volumes, about 4 volumes per- volume of reduced crude being preferred. The high propane-to-oil ratios employed in pro pane deresining processes for lubricating oil man ufacture are unnecessary and undesirable in the propane desalting operation, and the reduced crudes for desalting are usually not of the same type as those used for the manufacture `oi lubri eating oils. The invention will be more clearly understood from the following descriptionbf a 14,250 barrel per stream day deasphalting plant employed for the preparation from a salt-bearing reduced crude of a charging stock for a iluid cata lytic cracking system. The accompanying drawing which forms a part `of .this specification is a diagrammatic ilow sheet of a commercial desalting plant, Any salt-bearing reduced crude may be em ployed as a charge to the system, examples being an 18.7° A. P. I. East Texas-Magnolia reduced crude, a 21.2° A. P. I. gravity South Louisiana re duced crude, a 16.2° A. P. I. gravity New Mexico reduced crude, etc. few inches before it is coalesced on one of the collecting plates and thus effectively removed from the solution. Any eflicient type of settler may be used but the sloping baille type herein above described has been found to be very efûcient and to give excellent results. The salt is entrained or carried by the heavy materials which settle out in settlers 22 and 22’ and these settled liquids are withdrawn through lines 23 and 23’. The relatively salt-free pro pane solution is removed from the opposite side of the settler and preferably from the top thereof through lines 24 and 24’. These solutions pass through pressure reducing valves 25 and 25’ wherein the pressure is reduced to approximately 280 pounds and the temperature reduced to ap proximately 136° F. Each of the salt-free streams after the pressure reducing step will contain about 82,300 pounds per hour of oil, 122,500 pounds per hour of liquid propane, 85,500 pounds of propane vapor. These streams are then introduced by lines 29 and 26’ into depropanizers 21 and 21’ 30 Which operate at about 180° F. and about 280 These reduced crudes are pounds gauge. pressure. The depropanizers are preferably about 15 to 30% of the total crude and their salt contents may range from .05 to 1, usual ly from .1 to .5 pound per barrel. Such charge is heated by steam coils 28 and 28’. About 182,400 introduced from source l0 at a temperature of line 29 and line 29', this propane being returned through back pressure valve 30, line 3I and con denser system 32 and finally returned at a tem perature of about 120° F. to storage tank I I. The liquid stream which flows over bañ‘les 33 and 33’ is Withdrawn in amounts regulated by liquid level control valves 34 and 3'4’ through lines 35 and 35’ to depropanizers 36 and 36’. These depropanizers are likewise heated by steam coils 37 and 37’ `for maintaining a temperature of about 260° F. and a pressure of about 270 pounds gauge. About 15,650 pounds per hour of propane vapor is withdrawn from the top of depropanizers 36 and 36’ through lines 38 and 38', this pro pane vapor then being passed through lines 39 and 40 to line 3 I, condensed system 32 and storage tank II. The liquid which flows over baffles 4I and 4I’ is then Withdrawn in amounts regulated by liquid level control valves 42 and 42’ and introduced through line 43 to desalted oil stripping tower 44. About 164,600 pounds per hour of oil containing about 13,900 pounds per hour of propane is thus charged to the stripper which is maintained at a about 200° F. The propane in this example is a technical grade which may contain about 1 to 3% oi ethane and small amounts of isobutane and bu tane. The word “propane” is used herein and in 40 the accompanying claims is intended to mean a normally gaseous hydrocarbon of substantially the characteristics of propane, i. e., to include mixtures of propane with small amounts of other , normally gaseous hydrocarbons. The propane is 45 `stored in tank II at a temperature of about 120o F. and a pressureof about 255 pounds per square inch (all pressures being gauge pressures). y57,000 barrels per day or 424,000 pounds per hour of propane are Withdrawn from tank I I through 50 line I2, one half of it being pumped by pump I3 to line I4 and the other half being pumped by pump I5 to line I5. The 14,250 barrels per day or 194,000 pounds per day of charge are in troduced to the system through pump I'I, half 55 of the charging stock being introduced through 110W control valve I8 to line I4 and the other half being introduced through iiow control valve I9 pounds per hour of propane vapor is removed from the top of these depropanizers through to line I6. If desired of course separate pumps temperature of about 250° F. and a pressure of may be used for introducing charge and in fact 60 about 5 pounds gauge. Live steam is introduced one charging stock may be treated in one portion through line 45 for stripping the propane from of my system while another charging stock is the oil, the propane and steam being taken over being treated in another part. The propane head through lines 46 and 41 to jet condenser charging stock streams from lines I4 and I6 are 48 for condensation of the stripping steam. raised from a temperat-ure of 137° F. to 185° F. by 65 Desalted oil is withdrawn from the base of steamheaters 20 and 20', and at this tempera stripper 44 through line 49 by pump 5I) which op ture the mixture is introduced through lines 2| erates to maintain a constant liquid level in the and 2 I ’ into settlers 22 and 22' which are designed lower part of the stripper, The desalted oil to operate at a temperature of 185° F. and a pres amounts to about 12,350 barrels per stream day sure of 525 pounds per square inch. These settlers 70 and it is substantially free from salt. Thus a are preferably large cylindrical tanks mounted at charging stock which contains .35 pound of salt a slight angle to the horizontal and they are pref per barrel can be desalted in this system so effec erably provided `with sloping lbaffles at intervals tively that the salt content on the finished oil ofß or 4 inches, the slope of the baiiies being ,_ Y Will- be less than .0017 pound per barrel which about 45 degrees. The charge to the settlers is 75 is less than l/zou of the amount of salt in the . 2,406,1148 , 6 original charge and is so small as to be prac# tically negligible. L ' ' The heavy liquid containing salt may be passed from lines 2'3 and 23’ thru coils 5l and 5I' in furnace 52 and'heated from an entering'temper ature of about 185° F. to a transfer line temper ature of about 400° F. The streams are then com bined and introduced by line 53 into flash or vapor separation drum 5d Vwhich is operated at a tern perature of about 400° F. and pressure of about 10 270 pounds per square inch. Propane vapor is withdrawn from the top of this drum at the rate of about'l3,300 lbs. per hour and conveyed by line 55 to lines 4'0- and’ 3! for condensation and return tostorage drum il. The remaining salt-containing liquid», about 29,400 pounds per hour of salt plus heavy com ponents from the reduced crude, and about ’700 pounds per hour of liquid propane, is withdrawn ple. The catalyst may be rendered more stable at high temperatures by the addition thereto of zirconia, aluminum Vfluosilicate or other stabilizer. The catalytic cracking is effected at a temper ature within the approximate range of '750 to 1050° F., preferably about 900 to 950° F., e. g. about 925° F. The pressure at which catalytic cracking is eifected may be of the order of atmos pheric to 50 pounds or more per square inch, preferably about 5 to 15 pounds per square inch, e. g. about 10 pounds per square inch (gauge pressure in all cases). The flow rate or time of contact Will depend somewhat upon the catalyst, charging stock, and system employed and in a fixed or a moving bed system it may be within the approximate range of .3 to 3, for example about l volume of liquid charge per hour per volume of catalyst in the reactor with an on stream within the general` vicinity of 10 to 30 through line 56, through liquid lever controlled 20 minutesl or more. In the fluid-type or powdered catalyst vsystem' the catalyst-to-oil weight ratio valve 5T and> introduced into stripper 58 which in the stream entering the "reactor may range operates at about 400° F. and about 5 pounds per from about 1:1 to 25:1 and the Weight space square inch pressure. Live steam is introduced velocity in the reactor itself may be within the through line 59' and the stripped propane and steam is taken overhead through lines 59 and 25 approximate range of .3 to 3 pounds of charging stock per hour per pound of catalyst in the re 41T to jet condenser 48. Water is introduced into actor. jet condenser 48 which isr operated at about 2 The catalyst is periodically regenerated by pounds per square inch pressure. Water is intro combustion of carbonaceous deposits therefrom duced into the jet condenser through line bi'> at about 85° F. and this water together with con 30 usually at temperatures within the approximate range of 950 to 1150° F., care being taken to»k avoid densedA steam is removed from thel base of the unduly high temperatures. The heat of combus jet condenser> at about 110° F. through linev 62. tion may be vemployed for preheating and/or The overhead which consists of about 14,600 vaperizing charging stock as well a-s for supply pounds per hour of propane vapor is passed by line VE33 to trapout drum 04 which is operated 35 ing at least a part of the endothermic heat of cracking. When salt-bearing reduced crudes are at about l pound pressure and about 100° F., any employed as charging stock there is not only aqueous condensate being removed through line excessively large amounts of carbonaceous mate 65. Propane vapor from the top of this trap is rial deposited on the catalyst but there is also a passed by line 65 to compressor 66- and thence by lines 6l and> 3l back to the condenser system 40 deposit of salt on the catalyst and this salt de activates the catalyst in a relatively short time and propane storage drum. and makes it necessary for the entire catalyst to The depropanized material leaves the base of bel discarded. Since the cost of the catalyst is stripper 53 through line 68, pump 63 maintain one of the most important items in catalytic ing a constant liquid level in- the lower part of 45 cracking processes, it is essential that this cata stripper 53. lyst poisoning be avoided. Heretofore salt-bear The desaltedVv oil removed through line 49 is ing reduced crudes could not be used as charging excellent charging stock for catalytic cracking stocks and when overhead fractions were taken processes and- particularly for processes employ therefrom said fractions resulted in undesirably ing the so-called' huid-type operation although low yields of products characterized Vby undesir it may be used as charging stock for fixed bed ably low octane numbers. My invention makes units of the Houdry'type or moving bed units possible a substantial increase in the total amount which are commonly known to the art as the of high octane number motor fuel obtainable “Thermofor" catalytic (process. The catalysts from such reduced crudes andv at the same time employed> in all of-these processes is of substan it makes possible the use of salt-bearing crudes tially the same type and in all cases it is essential that the charging stock be substantially free from salt. The catalytic cracking may be effected with catalysts of the so-called natural or clay type which is an acid treated or activated Bentonite or Montmorillonitek clay or it may be a synthetic without rapidly deteriorating'or ruining the cata ‘ lyst. My process is particularly advantageous for reduced crudes containing upwards of about .1 pound of salt per barrel of reduced crude and « silica-alumina or synthetic silica-magnesia cata it is advantageous on charging stocks containing lyst. only .05 pound per barrel or as low as .0l pound per barrel. The salt content is substantially A suitable catalyst may be prepared by ball eliminated by my process so that desalted oils are milling silica hydrogel» with alumina or mag nesia using 2' to 30%, for example about 15% of 65 obtained in which the salt content is less than .005 pound per barrel and is usually less than alumina or magnesia, the ball-milled dough being dried at aV temperature of about 240° F. and then activated by heating to a temperature of about 900l to 1000° F. Alternatively, the catalyst may be prepared by Aforming a gel from dilute sodium 70 silicate in the presence of an aluminum salt by the addition of excess sulfuric acid, boiling the .002 pound per barrel. At the same time I re move from the charging stock the high molecular weight components which are objectionable in the catalytic cracking charge but may be very useful for other purposes. Y _ The reduced crudes are preferably about 10 to 30% of the total crude and are thus substantially resulting gel for an hour or two with an excess free from hydrocarbons of low or intermediate of dilutey ammonium hydroxide solution, wash-` ing', drying and heating as in the previous exam 75 boiling range. The A. P. I. gravities of such re _7, 2,406,748 8 duced crudes may be within the approximate range of 15 to 25° although beneficial results may described.' The salt may be separated from the solution of oil in normally gaseous diluent by be obtained on stocks of higher or lower gravities. means of centrifuges or other separation means. While specific operating conditions have been The diluent may be recovered in other manners, described in connection with the particular ex and in fact at least a part of the diluent may be ample hereinabove set forth, it should be under left in the oil which is charged to the catalytic cracking system. The invention is particularly stood that operating conditions will vary for dif ferent stocks processed and that various modiñ applicable to salt-bearing reduced crudes which are not «satisfactory for the manufacture of lubri cations and alternativesl may be employed both with regard to the operating system and to the 10 eating oils but are to be used as cracking stocks for gasoline manufacture. Outstanding features of conditions employed therein. I have found that the invention are the low construction and oper~ the salt can be almost completely removed from the solution in the settling drum regardless of the ating costs, the remarkable effectiveness of the salt removal, and the increased yields of high amount of heavy materials, asphaltic materials octane number cracked gasoline that are obtain and the like which may be separated and removed therewith. Simultaneously with the desalting I able from any given reduced crude without dele terious eifect on the catalyst employed in the may therefore effect varying degrees of deasphalt cracking operation. ing. The effect of propane ratio on the amount I claim: of asphalt precipitated depends to some extent 1.‘ The method of desalting reduced crude upon the nature of the reduced crude but usually which comprises maintaining a quantity of pro has the effect of decreasing the amount of asphalt pane in storage at a temperature of about 120° as the propane ratio is increased. On very short F., pumping about 4 volumes of propane from heavy reduced crudes, increasing the propane ra said storage and about 1 volume of a salt~beartio in the range between 3:1 to 5:1 may have the elïect of increasing the asphalt Iwhereas a further 25 ing reduced crude through a heating Zone to in crease the temperature of the mixture to at least increase above 5:1 tends to decrease the amount about 140° F. but not more than about 185° F., of asphalt. My desalting plant is not designed introducing the heated solution into a settling with the idea of having propane-to-oil ratio as a zone maintained at a temperature Within the controllable variable, but it is well to understand what can be expected to occur if the propane 30 approximate range of 140 to 185° F. and under a pressure suniciently high to prevent vaporization, ratio does vary. Operating temperature on the settling system separating the salt together with undissolved high molecular weight components of the re duced cruded from the propane solution of dis is intended as a controllable variable and has a deñnite effect upon the amount of asphalt pre 35 solved components in the settling zone, remov cipitated. Contrary to the usual solution laws an ing the solution from the settling zone, reducing increase in temperatures causes a decrease in the the pressure on the withdrawn solution but main taining the reduced pressure higher than pro solubility of asphalt and thus increase in the amount of asphalt precipitated. With a given pane storage pressure, heating said solution for type of reduced crude and a given propane ratio, 40 vaporizing propane therefrom, condensing said the higher the settling temperature the greater vaporized propane and returning it to said stor will be the amount of asphalt separated. age, reducing the pressure on the remaining pro The range of temperature in the settling ves pane solution to approximately 5 pounds per sels may vary Within the approximate limits of square inch, stripping said solution with steam 140 to 185° F., 140° F. giving minimum asphalt 45 for removing propane therefrom, condensing the production and 185° F. giving maximum asphalt stripping steam with a jet of relatively cool Wa production which is usually desired along with ter, separating water from propane vapors, com the desalting of the reduced crude. pressing, condensing and returning said propane It is essential that the propane be kept in liquid vapors to said propane storage. condition in the settling zone since the vaporiza~ 50 2. The method of desalting a reduced crude tion of any propane in the settlers Iwill prevent which comprises main-taining a quantity of pro proper settling of the lower phase and thus inter pane in storage at elevated pressure and at an within the limits for which the plant is designed fere with the desired desalting operation. Usu elevated temperature which is substantially be ally a reasonable pressure on the settling Zone is low about 140° F., mixing about 3 to ’5 volumes maintained above the amount calculated for com 55 of propane from said storage with about 1 volume plete liquid phase conditions and it is important of a salt-bearing reduced crude, heating said mix in determining the pressure to take into account ture and holding it in a settling zone at a tem any small amounts of ethane that may be present perature within the range of about 140° to 185° in the propane. With the exception of the two F. under a pressure sufficiently high to prevent strippers and the jet condenser the pressures em vaporization for a time sumcient to effect sepa ployed at various stages following the settlers are controlled primarily by the pressure maintained ration of salt together with undissolved high molecular weight components of the reduced on the propane storage tank. The high pressure crude from the propane solution of dissolved com ñashpropane recovery units can be said to “float” ponents in the settling zone, removing the solu on the propane storage tank, i. e. to carry such 65 tion from the settling zone, reducing 4the pres pressure as is necessary to make the vapors from these vessels move through the lines and con densers back to the storage tank. The pressure on the two strippers and on the jet condenser is reduced to atmospheric pressure in order to facilitate complete vaporization of propane and the propane thus released is compressed for re~ turn to the condenser and sto-rage system. As above stated, my invention is not limited to the precise system and conditions hereinabove sure on the withdrawn solution but maintaining the reduced pressure higher than the propane storage pressure, heating said solution for vapor lzing propane therefrom, condensing said vapor» ized propane and returning it without compres sion to said storage, reducing the pressure on the remaining propane solution to a level from about atmospheric to about 5 pounds per square inch gauge, stripping said solution at the reduced 75 pressure with steam for removing propane there' 2,406,748 from, condensing the stripping steam from pro pane vapors liberated in the stripping step and compressing, condensing and returning said pro pane vapors to said propane storage. 3. The method of claim 2 wherein the salt bearing reduced crude contains onli»T the residual components of a crude petroleum oil after vapor izable components have been removed to the ex tent of at least about 50% of the total crude. 4. The method of claim 2 wherein the salt bearing reduced crude contains at least about .05 pound of salt per barrel. 5. The method of claim 2 which includes the 10 from the settling zone to a heating zone, heat ing said materials to atemperature of lapproxi mately 400° F., separating propane vapors from the heated materials at a pressure which is high er than the propane storage pressure, condens ing the separated vapors and returning them to said propane storage, reducing the pressure of the remaining materials to about atmospheric to about 5 pounds per square inch, stripping said materials with steam at said reduced pressure for removing residual propane vapors, condensing and separating steam from said residual propane _vapors and compressing, condensing and return ing said propane vapors to said propane stor steps of passing separated salt and undissolved high molecular Weight components of the reduced 15 age. crude together with propane associated therewith NORMAN L. DICKINSON.