US1968093A - Corrosion prevention - Google Patents

Description

July 31, 1934. A. H. J. OTT El AL CORROSION PREVENTION Filed Nov. 28, 1952 FIG. 2

INVENTORS ALBARTUS HENDRIK JAN OTTO JOHAN FREDERIK VAN HOLST /TOR Y Patented July 31, 1934 PATENT F Q GORRO SION PREVENTiON Albartus H dr kjJan D ta and Johan F ede ik .van flolstlm asta Cu ac mDut h W st indi s, assignors to n versa QilT mducts Company, Chicago, 7111., a corporation of Delaware - npplicati niNovemlie z ,1-932, Serial No, 644,554

6 C a ms. v(Ci. 196-133) This invention relates to improvements cor rosion prevention and more particularlyrelates to an improved method and means for preventing H x corrosion in refining equipment such'as fraction- 5 ators for cracked vapors. r

We have found that vapors resulting from the.

pyrolytic conversion of hydrocarbon oils contain.- ing appreciable sulphur comDOunds, acidic or other corrosive materials give trouble f-romcorrosion in fractionating equipment principally in the lower portion" of the fractionator where the temperatures-are highest and that corrosionjh the upper portion of the fractionator where the temperature of the vapors has been considerably decreased, is often negligible or non-existent.

' It has become common practice to supply the raw oil charging stock for crackingtothe system by feeding all or a portion of it into the fractionator, where it comes into direct contact with theheated vaporous conversion products, serv+ ing to cool them and assist their-fractionation and being thereby pro-heated. In such processes :the reflux condensate resulting from fractionation of the vapors and 'the preheated ;raw oil charging stock collect in the lower portion of the fractionator and are supplied therefrom to the heating elementof'the system for conversion. 7

The present invention, in its most specific p nbodiment, utilizes 0114101136 cracked-as a means of cooling the heated vaporous conversion products in" the upper portion of the 'iractionator of the system to below a temperature at which they are corrosive and the oil thus utilized alsoser v'es as a means or" preventing corrosion of -the-walls of thefractionator 'in its lower portion, e. that portion of the -fractionator where the vapors -reniain at a corrosive -tern-perature. {This *isaccgm pl-ished by providing a'liner -or,--more strictly, a false shell, in the lower-portion-ofthefractionator,

spaced away from the walls of the fractionator.

The space thus provided, is kept substantially filled with oil which enters preferably-at a low pointand overflows over the upper end of the false shell or liner intolthe upperportion of the ffractionator proper. The oil thus fed through the space provided between the outer walls-of the 'fractionator and the false shell or liner not only serves to keep the walls or both-cooL'but also serves *asa protective body preventing 'con-t'act'of not corrosive'vapors and liquid ,-with the outer shell.

"In its broader =oonceptsthe iea-tures-otthe invention are applicable -to:.use wi-th any-equipment which is subject to corrosion, particularly i rom ina heated state andstill-moreparticularly fromfluids which are less corrosive at low temperatures. The features of the invention may, for example, be utilized to advantage in a wide variety of oil refining equipment such as frac tionators of all'kinds, heat exchangers, scrub bers and absorbers, reactionchambers', etc, as well as f-or equipment utilized in the paper-making and chemical industries in general. Any non corrosive cooling medium may be utilized and preferably it is a fluid which will remain sub.- stantially :in :fluid form under the conditions to which :it is subjected in the space betweenthe liner and the shell of the vessel which it protects. It may-or may not be desirable to introduce the cooling .fiuid into direct contact with-thematerials undergoing treatment in the vessel after it has passed through the space provided between the wal lsof the vessel and the false shell or liner. in

the latter case it may @be simply .withdrawn'afrom the space between the walls of the vessel and the false shell and utilized in any'desi-red manner, or it-may benooled and-recirculated back to the inlet to said space. i

' novelty and featuresof the invention may bemore fully understood by reference to the -at= tached diagrammatic drawing, Figs. land 2, and thejfoilowing .descriptionflthereof. The following description of the-drawing includes a description of the practice of the invention as it maybe accomplished :the particular type of apparatus shown. Referring :to the drawing, Figure *1 is a cross sectional elevationof one specific dorm of #fractionator for handling hydrocarbon oils, to the principles of the invention have been appl-ied, and"Figure-2 is a plan view of the same .atractionator taken along a horizontal plane in- .dicated by the line 2 2 of Figure 1. The main iractionator and is spaced away f rom the inner surface of shell 1in such a manner that a ciroum ferential space 9 is provided therebetween'. This space-also-exists betweenthe bottom; head of the L=falseshell and the bottom head of thef-ractionator which are-integral with thewalls 8 and A ialse shell-ordiner 8 is -provided within-the 1 respectively. Suitable sleeves 10 and 11, preferably of non-corrosive metal, may be provided within nozzles 4 and 5 respectively, as indicated in the drawing. The liner or false shell 8 may be constructed of ordinary low carbon steel, or of any suitable non-corrosive metal such. as chromesteel, or chrome-nickel steel. The use of noncorrosive alloys for the construction of this liner is not essential and is ordinarily unnecessary ex-. cept in extreme cases as the cool oil c'rculated be tween the liner and the shell of the fractionator;

will ordinarily keep the liner sufficiently cool to prevent its substantial corrosion and, in order to assist in keeping the liner cool, as well as for economy, the liner is preferably constructed of relatively thin sheet metal, as compared with thickness of the outer walls of the fractionator.

The oil utilized as the cooling medium is supplied through line 12 and valve 13 to the space 9 between walls 1 and 8 preferably entering this space at a relatively low point in the fractionator, as illustrated in the drawing. The oil-flows continuously upward through space 9 and overflows over the upper end of false shell 8 into the central portion of the fractionator where it comes into direct contact with the vapors arising therethrough. When desired, a perforated plate 14 or other suitable means may be provided at the upper end of shell 8 to effect distribution of the cooling oil across the entire cross sectional area of the central portion of the fractionator so that substantially uniform contact between the vapors and the cooling oil is obtained.

Preferably the quantity of the cooling oilsupplied, as described, through space 9 into the central portion of thefractionator is suificient to maintain the vapors and that portion ofthe fractionator above the liner or false shell 8-below a corrosive temperature or, when desired, -addi-- tional cooling oil of the same or difierent character than that supplied through line 12 and valve 13 may be introduced intothe fractionator by means of line 15, valve 16 and spray coil 17, of any suitable form, to somewhatcool the vapors prior to their contact with the oil overflowing from space 9 to insure a sufficiently low vapor temperature immediately above shell 8. A spray coil 18 of any suitable form supplied, preferably, with a relatively light cooling oil, such as a portionof the final light distillate product of the system, through line 19 and valve 20, may be provided in the upper portion of the fractionator to assist fractionation and to regulate the. vapor outlet temperature, 'thus controlling the end boiling point of the final distillate product.

The space 9 between liner 8 and shell 1 is preferably made sufficiently small in cross sectional area to maintain the velocity of the oil supplied thereto through line 12 and valve 13 sufiicient to prevent its reaching the vaporization point of any substantial quantity of this oil so that .a solid body of relatively cool oil is maintained between liner 8 and shell 1.v This also servesto keep both the walls of shell 8 and 1 at a minimum temperature. 7 It will be understood that the embodiment of the invention illustrated and described is not limited to the use of raw oil charging stock for cracking as the cooling mediumcirculated be tween the false shell and the outer walls of the fractionator. V For example a lighter oil such asa portion of the final light distillate product of the system maybe utilized and circulated in sufiicient quantities and ata sufficiently highvelocity to remain substantially'unvaporized until after its introduction into the central portion of the fractionator or, when desired, a portion of the reflux condensate or a portion of the combined feed for the system may be cooled and circulated around the liner as a cooling medium or, in fact, any final or intermediate product of thesystem which will not contaminate the materials in the fractionator may be utilized. The exact nature of the oil is not a limiting feature of the invention although an oil is preferably used which is substantially non-corrosive at the temperature attained prior to its introduction into the central portion of'the fractionator and which, preferably, remains substantially in the liquid-phase prior to its introduction into the central portion of the fractionator.

As a specific example of the operation of the process of the present invention, vapors resulting from cracking of a heavy California crude oil containing substantial quantities of sulphur compounds are supplied to the fractionator at a temperature of approximately 825 F. A vapor outlet temperature of approximately 500 F. is maintained at the top of the fractionator. A light gauge liner of ordinary low carbon steel is utilized in the lower portion of the fractionator and the raw oil charging stock for the system is introduced into the space between the liner and the fractionator shell at atmospheric temperature. A sufficient quantity of this cooling oil is utilized to maintain'a vapor temperature immediately above the false shell or liner at approximately 650 F. As a result of this method of operation, no portion of the outer shell of the fractionator shows .anysigns of corrosion upon inspection after approximately a years operation. A portion ofithe inner surface of the false shell or liner directly opposite the vapor inlet showed a small amount of corrosion but the liner was otherwise intact. These results are better appreciated by comparsion with corrosion which resulted in the loss of about inch of metal a year in the walls of an unlined fractionator operating in conjunction with the same type of cracking process utilizing the same type of charging stock.

It is to be understood, of course, that the sleeves 10 and 11 are removably associated with the liner 8.

We claim as our invention:

1. In combination with an enlarged vertical chamber provided with walls susceptible to corrosion, of a partial liner therefor spaced from the lower and bottom portions of the inner wall of the chamber to provide a circumferential space therebetween, an inlet to said liner, an outlet from said-liner, an inlet to the chamber for charging the circumferential space with liquid, and an outlet for discharging the liquid from said space. 2. In combination with an enlarged vertical chamber provided with walls susceptible to corrosion, of a relatively thin partial liner therefor spaced from the lower and bottom portions of the inner wall of the chamber to provide a circum ferential space therebetween, an inlet to said liner, an outlet from said liner, an inlet to the chamber for charging the circumferential space with liquid, and an outlet for discharging the liq- .uid from said space.

v 3. In, combination withan enlarged vertical chamber provided with walls susceptible to'corrosion, of a relatively thin partial liner therefor res its

of non-corrosive material spaced from the lowerand bottom portions of the inner wall of the from said liner, an inlet to the chamber for charging the circumferential space with liquid, and an outlet for discharging the liquid from said space.

4. In combination with an enlarged vertical chamber provided with walls susceptible to corrosion, of a relatively thin liner therefor of noncorrosive material spaced from the inner side and bottom walls of the chamber to provide a circumferential space therebetween and disposed in the lower portion of said chamber, the upper end of said liner terminating a substantial distance below the upper end of the chamber, an inlet to said liner, an outlet from said liner, an inlet to the chamber for charging the circumferential space with liquid, and means for passing liquid from said space to the interior of said liner.

5. In combination with a vessel adapted to retain liquids and vapors for treatment under relatively high temperatures, an inlet and outlet for said vessel, a non-corrosive liner mounted within the lower portion of said vessel and spacedly disposed from the inner walls thereof, means for passing a cooling liquid into the space thus formed, and means for dispersing said cooling liquid through said vessel after its passage through said space.

6. In combination with a vessel adapted to retain liquids and vapors for treatment under relatively high temperatures and superatmospheric pressures, an inlet and outlet for said vessel, a non-corrosive metallic liner mounted within the lower portion of said vessel and spacedly disposed from the inner walls thereof, means for introducing a cooling liquidinto the space thus formed and passing the same upwardly therethrough, and means associated with said liner for dispersing the cooling liquid through said vessel after its passage through said space.

JOHAN FREDERIK VAN HOLST. ALBARTUS HENDRIK JAN O'ITO.

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