Патент USA US2403563код для вставки
Patented July 9, 1946 2,403,563 UNITED STATES PATENT OFFICE 2,403,563 SURGE TANK SYSTEM Marshall R. Sprinkle, Edwardsville, and Robert S. MacDuli’, Alton, Ill., assignors to Shell De velopment Company, San Francisco, Calif., a corporation of Delaware Application October 4, 1943, Serial No. 504,984 7 Claims. (Cl. 137-78) l 2 The present invention relates to surge tank sys in sour hydrocarbon distillates, and more particu tems and more particularly to surge tank sys larly in gasoline distillates, are extracted with tems for use in processes wherein absorption of solutizer solution, i. e, aqueous solutions of alkali small quantities of air or oxygen by the reactants metal hydroxides containing solutizers, is well in passing through a surge tank system is dele 6 known. The solutizer process has been described terious or undesirable.` and the several compounds particularly suitable In the majority of industrial chemical proc .as solutizers have been enumerated in the gen esses involving process ñows it has been found eral literature, for example, Rei-incr and Natural advantageous to include surge tanks Within the Gasoline Manufacturer, May 1939, pages 171 to flow system. These tanks serve to minimize or 10 176 and March 1940, pages 73 to 76; Industrial eliminate ñuctuations in ñow rates throughout and Engineering Chemistry, vol. 32, pages 257 the system and conventionally comprise a sim to 262, February 1940; Chemical and Metallurgi ple reservoir from which fluid material to be cal Engineering,` vol. 47, pages 776 to 778, Novem treated or reacted may be withdrawn at a con~ ber 1940, etc. As shown in these references, the stant rate regardless of variations of input iiow solutizer process involves the extraction of mer to the reservoir. However, since the liquid level captans whereby a spent solutizer solution is pro Within the surge tank is either continuously or duced which is continuously regenerated as by periodically changing, it is necessary to provide steam stripping, and the regenerated solution is a vent or breather arrangement in order to avoid then re-used for further extraction of mercap substantial pressure changes within the system. 20 tans. The principal purpose of the process is In some instances, particularly where the ma to sweeten sour gasoline distillates, . terial passing through the surge tank tends to It has been observed that in the course of absorb air, difficulties in the operation of the' such treatment, hydrocarbon distillates, e. g. gas process are encountered as a result of the` air oline, may deteriorate in color and the solutizer absorbed in thesurge tank, usually in the form 25 solutions, i. e. alkali metal hydroxide solutions of undesirable side reactions, excessive foaming, containing solutizers, at times tend to form rela sludging, or the like. tively stable emulsions with the hydrocarbon oil It is an object of the present invention to under treatment, probably due to gradual ac provide a surge tank system wherein contami cumulation of emulsiñers believed to be resinous 30 substances not removable by steam stripping, therethrough is substantially eliminated. Other which emulsions either reduce the throughput objects, together with some of the advantages to due to retarded settling or cause carry-over of be derived from operating according to the pres valuable solutizer. ent invention, will become apparent from the It has been found, however, that the trouble-vfollowing detailed description thereof, taken to 35 some substances, emulsiñers as well as the color gether with the accompanying drawing which is bodies, are formed through oxidation, probably a schematic flow diagram of a speciñc application of some components contained in the hydrocar of one embodiment of the invention. bon oil to be treated. One of the principal places In the present improved surge tank system, wherein undesirable oxidation and/or oxygen ab nation, by air absorption, of materials passing fluctuation in the content of the surge tank due 40 sorption normally occurs is in the surge tank to inconstant rate of liquid input thereto is com system of the process as usually operated. pensated by interñow of an aqueous displacement According to the present invention such unde medium, preferably water,lbetween the surge tank sirable oxidation may be avoided, for example in and an auxiliary tank in accordance with ñow the manner disclosed in the accompanying draw rate variations to the surge tank, and air is ex 45 ing. Sour hydrocarbon liquid free from ab cluded from the surge tank by maintaining a va sorbed airor oxygen is passed from conduit l5 por blanket over the liquid level in the auxiliary into surge tank I from whence it passes through tank, as will be explained in detail below. conduit 2 into extractor 3 wherein it is counter For purposes of illustration, the invention will currently contacted with fresh sclutizer solution 50 be described in relation to its application to a entering through conduit 8, Spent solutizer so specific process wherein a surge tank is normally lution passes out of extractor 3 through conduit included and wherein air absorption by materials 9 and thence through conduit Il to be regener passing through the surge tank is objectionable. ated. Treated hydrocarbon liquid and small The solutizer process, by means of which mer amounts of entrained solutizer solution pass out captans and other weak organic acids contained 55 of extractor 3 through` conduit 4 to washer 5 2,403,563 3 4 other material which is normally in a vapor state at the temperature of operation, is relatively in soluble in water, and does not contain air or oxy wherein they are countercurrently contacted with water entering washer 5 through conduit 1. The wash water, including spent solutizer solution re moved from the hydrocarbon stream, passes out gen, may be utilized. Suitable examples of such materials include, for example, nitrogen, meth ane, ethane, butane, propane and the like. Although the present improved surge tank sys of washer 5 through conduit Iû to contact I I, the treated and washed hydrocarbon liquid passing through >condu-it 6 to utilization, storage or fur- , tem has been described with particular reference lto its use in combination with the solutizer gaso line sweetening process, it will be readily under ther treatment. A water level is maintained in surge tank I and in tank I3, conduit I2 permitting passage of stood that the principles of operation and con struction have wide applicability in any surge tank `arrangement wherein it is necessary or de water in lboth directions. A blanket of fuel gas is maintained above the water level in tank I3. In normal operation, sour hydrocarbon liquid is withdrawn from surge tank I through conduit 2, the rate of flow being controlled by valve I1 or other suitable means. If the rate of flow of sour hydrocarbon liquid to surge tank I through con duit I5 should temporarily exceed the rate of sirable to exclude oxygen from a system wherein a water-immiscible liquid is passed through a surge tank. For example, the problem of oxygen exclusion also arises in the separation of butadiene, pen tadiene, hexadiene, etc., from other C4, C5 and withdrawal from surge tank I, water is displaced from surge tank I and forced through conduit 20 Ce hydrocarbons respectively, oxygen causing the formation of gummy materials as well as foam I2 'to tank I3, in turn forcing fuel gas from the ing and emulsifying agents; or in the separation top of tank I3 to a gas reservoir (not shown), of benzene, toluene, xylenes, etc. from narrow such as a conventional water-sealed gasholder, boiling hydrocarbon mixtures containing them for example, which delivers gas under a slight positive pressure. Conversely, when the rate of 25 by extractive distillation with phenol, oxygen in this case causing corrosio-n in the reboiler of the extractor, or sludging of the phenol, or both; or in the polymerization of oleñns with phos phoric acid or other solid catalyst, oxygen caus withdrawal from surge tank I is less than the rate of input, the water level in surge tank I will rise, water flowing by gravity from tank it through conduit I2, and an equivalent quantity of fuel gas will pass through conduit I4 to replace the water` exiting from tank I3. A purging conduit IB `including valve I9 is also provided in tank I3 in order to avoid entrap ment of an .air pocket when starting operations. Thus, in putting the unit in operation, the sys tem may be first charged with fuel gas admitted through conduit I4, valves I6, i9, 23 and 25 being closed during this purging operation. Valves 2l! and 2| are then opened and a quantity of water admitted to tank I3 through conduit I6, and to surge tank I through conduit I2, valve I9 being opened meanwhile for a suflicient period of time to insure escape of any air entrapped in tank I3. When a suitable liquid level has been at tained in surge tank I, valve 23 is opened and flow of sour hydrocarbon liquid to surge tank I permitted, resulting in a back pressure within surge tank I and preventing further flow of water thereto from -tank I3 and permitting the desired liquid level to 'be attained in tank I3, whereupon valve 2| is closed. The system will then operate automatically to take care of fluctuation in feed rate to surge tank I, as described above. Water may be withdrawn from the surge tank system, ing gumming of the catalyst, thereby shortening its useful life, etc. In virtually all commercial plants wherein processes such as those above described are carried out it is both necessary and desirable to include one or more surge tank sys 35 tems, and it is in such systems that contamina tion o-f the product or reactants with oxygen often occur. Such contamination may be en tirely obviated by use of the surge tank system described in the present specification. 40 We claim as our invention: l. In an arrangement for minimizing iiow fluc tuations in a flow system the combination com prising a closed surge tank, a closed auxiliary tank, flow communication means between said 45 surge tank and said auxiliary tank, an Iaqueous displacement medium comprising water in said surge tank and said auxiliary tank, said flow com munication means terminating beneath the liq uid level of said aqueous displacement medium 50 in said surge tank and said auxiliary tank, means lfor introducing a substantially water-immisci ble oxidizable fluid material having a density less than that of water to said surge tank, means for withdrawing said substantially water-immiscible when desired, through conduit 24 by >opening 55 oxidizable ñuid material from said Vsurge tank and means for maintaining an oxygen excluding valve 25. vapor blanket above the liquid level of vsaid aque ous displacement medium in said auxiliary tank. 2. In -an arrangement for minimizing flow if desired or useful for a particular purpose, as 60 fluctuations in a flow system the combination comprising a closed surge tank, a closed auxiliary for example it may be advantageous to include tank, flow communication means between said varying amounts of salts, acids, alkalis, wetting surge tank and said vauxiliary tank, an vaqueous agents or alcohols and the like in the displace displacement medium in said surge tank and said ment medium for various purposes. auxiliary tank, said flow communication means It has been found that the maintenance of an terminating at each end beneath the liquid level inert blanket over the water in tank I3 is an es of said aqueous displacement medium in said sential feature of the invention since, in the ab surge tank and the liquid level of said aqueous sence of such a blanket, suiiicient air is absorbed displacement medium in said auxiliary tank, re by the water in tank I3 and transmitted to surge tank I, wherein it is taken up ‘by the hydrocarbon 70 spectively, said aqueous displacement medium normally tending to ñnd a common level by grav material, to seriously interfere with the opera ity flow through said flow communication means, tion of the sweetening process. Although fuel means for introducing a substantially water-im ‘gas is a particularly suitable material for the miscible oxidi'zable fluid material having a `den purpose of forming an inert blanket over the water in tank I, it will be appreciated that any 75 sity less than that of water to said ‘surge tank, Although Water alone is generally to be pre ferred as the aqueous displacement medium, other primarily aqueous media may be employed 5 2,403,663 means for withdrawing said substantially water immiscible oxidizable ñuid material from said surge tank and kmeans for maintaining an oxygen excluding vapor blanket above said liquid level of aqueous displacement medium -in said auxil iary tank. iary tank, ilow communication means between ' said surge tank and said auxiliary tank, water bodies in said surge tank and said auxiliary tank, said flow communication means terminating at one end beneath the water level of said water body in said surge tank and at the other end be neath the water level of said body of water in 3. In an arrangement for minimizing ñow fluctuations in a 'flow system, the combination said auxiliary tank, said water bodies normally comprising a closed surge tank, a closed auxiliary tending to ñnd a common level by gravity iiow tank, flow communication means between said 10 through said iiow communication means, means surge tank and said auxiliary tank, water bodies for continuously introducing to said surge tank in said surge tank and said auxiliary tank, said liquid hydrocarbon material having a .density i'low communication means terminating at one less than that of water, said hydrocarbon mate end beneath the water level of said water body rial being of such nature as to necessitate exclu in said surge tanke and at'the other end beneath 15 sion of contact thereof with oxygen, means for the water level of said body `>of water in said aux continuously withdrawing said liquid hydrocar iliary tank, said water bodies normally tending bon material from said surge tank, and means to find a common level by gravity ñow through for maintaining an oxygen-excluding vapor said ñow communication means, means for con blanket under pressure above said water level in tinuously introducing to saidsurge tank liquid 20 said auxiliary tank. hydrocarbon material having a density less than 5. The system according to claim 3 wherein that of water, said hydrocarbon material being the oxygen excluding vapor blanket comprises of such nature as to necessitate exclusion of con a normally gaseous hydrocarbon. f tact thereof with oxygen, means for continuous 6. The system according to claim 3 wherein ly withdrawing said liquid hydrocarbon mate 25 the oxygen excluding vapor blanket comprises rial from said surge tank at controlled ñow rates nitrogen. and means for maintaining an oxygen-excluding 7. The system according to claim 3 ¿wherein vapor blanket above said water level in said aux the oxygen excluding vapor blanket comprises iliary tank. 4. In an arrangement for minimizing flow 30 iluctuations in a ñow system, the combination comprising a closed surge tank, a closed auxil fuel gas. MARSHALL R. SPRINKLE. ROBERT S. MACDUFF.