US2327490A - Apparatus for treating hydrocarbon oils - Google Patents

Description

Aug; 24, 1943. A. BJBAGSA R I APPARATUS FOR TREATING HYDROCARBON OILS Filed Jan. 2, 1941 .QOQQO o 0 6 9 000000 1 0 Irv/r558.-

Patented Aug. 24, 1943 UNiTED STATES PATENT OFFICE APPARATUS FOR TREATING HYDROCAR- BON OILS Aaron B. Bazsar, Lansdowne, Pa., assiznor to Sun all Company, Philadelphia, Pa., a corporation of New Jersey Application January 2, 1941, Serial No. 372,806

6 Claims.

tube is subjected to, with resultant increase in hardness, and corresponding decrease in ductility, of the metal. This absorption of nitrogen is very pronounced, even after relatively short exthrough a chamber containing a catalyst folposures, at temperatures approaching 10501100 lowed by passing regenerating fluid through the F. Another objection to plain carbon steel is catalytic chamber to effect removal of combushat it b c s em r e by pr l exposure tible materials, it is important to control the temto the salts at temperatures above about 950 F. perature. The desired temperature is usually That various high alloy steels, especially those approximated by pre-heating the hydrocarbon 10 having a high percentage of chromium or of vapors and regenerating gases. In some prochromium and nickel, ofier pronounced resistcedures the net reaction'is endothermic and in ance to certain typ s of Corrosion is w but others exothermic and it is therefore often neces such high alloy steels are open to certain serious sary, and always advantageous, to supply or ab- Objections. Their thermal conductivity is disstract heat from the catalytic chamber to com-' tinctly inferior to that of ordinary steel. Their pensate for the heat lost or gained by the endohigh thermal e p nsion is objecti a in that thermic or exothermic reaction. It is known to if the tubularv ele en s are m d her from i accomplish this by flowing a heat exchange fluid y e necessary t make the entire eq pment through the mass of contact material in direct 0 th Sa e eomlmsitieny are t readily heatrelation, but out of contact, with the cataweldable under field conditions and they require lyst. The most effective heat exchange media some heat treatment after welding. Finally. ch for thus maintaining practically constant the tub a e too expensive to justify their use for the temperature during the said on-stream and oif- P s Of eliminating the defects 0f P a stream cycle are mixtures or solutions of salts, h n S even if it were possible to v r y of difierent composition, which are liquid at the Such high l y steel that would not be op n to temperature at which they enter the catalytic the O je s pecified. I chamber. As examples of efiicient salt. compoere e. t practical co c p iti may it d; which it is the object of my invention to solve, is KNOL 4540,70 NaNOz 55 t produce in alloy steel which will have a high M03 5M6% mamas 15 NEJNOS 35% s s ance corros on by the particular salts that are used-as heat exchange media in proc- KNOs, 50%, NaNOa, 26%, CaiNOaM, 30% esses for can u t ti KNO: NaNOs, 2o%- escrow 45% y m ng hydmarbm w which will have a much less tendency to absorb The most effective way of utilizing such salts is nitrogen from the hot salts,'which. will not beto flow them through a multitude oi. small diam 35 come seriously embrittled by prolonged exposure eter tubeawhich may or may not-be provided to the hot salts, which is substantially as workwith fins, extending preferably vertically through able and weldable as plain carbon steel, and the the bed of contact material, although other arcost of which does not greatly exceed that of rangements are known. Such tubes have usually plain carbon steel. been made of straight low carbon steel contain- 40 For several years, under my supervision, many ing the usual percentage of manganese, but these low al oy steels have been subjected to various are susceptihleto rather rapid corrosion by the and exhaustive tests to determine the possibility salts, which necessitates frequent replacement. f mee ing the particular combination of require- Such corrosion increases with extreme rapidity ments above mentioned. As a result of such tests through a range of temperatures from about 850 I have found it possible to produce 8' Steel 3 F. to G-1100 F. Then, too, carbo steel, abthat meets the above requirements. The total sorbs nitrogen from the hot salts, forming either p r ent of th alloying ingredients, other than a solid solution oi? nitrogen in iron, or iron nitride carbon and the usual percentage of manganese needles, depending on the amount of nitrogen and silicon, need not exceed one per cent., alabsorbed and on the thermal cycle that the steel so though a substantially higher, but um percentage is preferred. The different compositions that I have found to meet said requirements come within the ranges set forth in the column below entitled permissible range, those which meet such requirements most satisfactorily are within the column entitled preferred ranges; and typical compositions are in the columns so entitled. The percentage of iron is not specified, since the balance is substantially all iron.

Permissible Preferred Typical ranges ranges compositions Carbon 50% 20% 12% l Manganese .25- 2.0 .30- .75 50 .40 Silicon .10- 2. 5 -1. 50 75 1. Chromium 0- 3. 0 -1. 25 75 50 Nickel .70- 5.0 l. 503.50 3.00 2.00 Molybdenum 3. 0- 25-1. 00 75 .25 Copper .0- 2.0

Total Cr, Ni, Mo and Cu .70-13. 0 2. 255. 75 4. 50 2.75

In the preferred and most efficient compositions, the percentage of Ni substantially exceeds that of any other alloying element, also exceeds the percentage of chromium plus molybdenum and is not substantially less than, and may exceed, the percentage of chromium plus molybdenum plus either manganese or silicon. A small percentage of molybdenum must be included where strength at high temperature and insusceptibility to embrittlement are desired- The percentages of the various ingredients may be varied within the ranges above specified dependent upon the relative importance, in the particular catalytic apparatus and the process practiced therein, of resistance to corrosion by the heat-exchange salts, resistance to nitrogen absorption, resistance to embrittlement, the necessity for ready workability and easy welding, and the factor of expense of the alloy steel.

Therefore it cannot be said that any specific composition vw'thin the distinctly preferred range is superior toany other specific composition within such range.

Any composition with the wider range set forth in the above table has a corrosion rate much less than that of carbon steel. Most of such compositions and (it is believed) all of them within the preferred range have a corrosion rate from one-fifth to one-half that of plain carbon steel when exposed to said salt mixtures at high temperature. Moreover the rate at which corrosion increases with increase of temperature (say from 850 F to 1050-1100 F.) is very much higher with plain carbon steel than with alloy steel of the composition described.

In catalytic processes in which hydrocarbons are treated as hereinbefore explained, a very efficient construction is that illustrated in the accompanying drawing, in which Fig. 1 is a vertical sectional view through the catalytic chamber and Fig. 2 a partial cross-section through the same.

The illustrated apparatus, which is substantially like that disclosed in the Pew Patent No. 2,248,118, issued July 8, 1941, comprises a cylindrical casing a. having an oil vapor inlet 1) and an oil vapor outlet 0. Tube sheets d and e provide top and bottom headers or manifolding chambers f and g, and between them the reaction zone or catalytic treating chamber h, which is substantially filled (except for the space occupied by the tubes hereinafter described) with any suitable siliceous or adsorptive catalyst which may be found effective for the reaction described. A multiplicity of tubes is extend between the tube sheets. Within the tubes is extend vapor inlet tubes 2. The tubes 1' open at the bottom into the space enclosed by the tubes k and open at the top into the upper header 1. The tubes k are closed at the bottom and also at the top except to allow the extension through the tube sheet d of the upper ends of the tubes 2. A multitude of vapor outlet tubes m are carried by and extend through the lower tube sheet e and there communicate with the lower header g. Tubes m extend upward through nearly the entire height of the chamber and are closed at the top. Tubes k and m have perforated walls. Each tube is has spaced from it, at short distances and in symmetrical relation, a number of tubes 11].. Oil vapors flowing from inlet b pass through the upper header f and tubes i into tubes k, thence laterally through the perforations in tubes is, thence through the catalytic material with which the chamber is packed, thence through the perforations in tubes m into such tubes, and thence through such tubes into the lower header g and out through the outlet 0.

The casing 11 should be insulated from the surrounding atmosphere by any suitable means such as a jacket n for hot gases or insulating material.

The tubes hereinbefore described whereby the mixtures or solutions of salts flow in heat exchange relation with the catalyst are marked 0 in the drawing. These tubes, which are of course imperforate, are preferably more numerous than the oil inlet and outlet tubes and extend vertically entirely through the catalytic chamber and through both tube sheets into the headers f and g. The tubes 0 communicate at opposite ends with tubes 12 and r for supplying the salt mixture to and removing it from the tubes o. The tubes 0 are symmetrically arranged relatively to each other and to the tubes k and 111.

As before stated, the hot oil vapors in the on-stream part of the cycle, and the regenerating medium in the off-stream part of the cycle, pass through the contact bed from one set of tubes k to the other set 171., while the salt mixtures continuously flow through the tubes 0. The temperature of the salts flowing through tubes 0 is such as to supply or abstract heat from the catalytlc chamber to compensate forthe heat lost or gained by the endothermic or exothermic reaction and their distribution is such as not only to maintain the catalytic mass at a predetermined, usually constant temperature, but also so to maintain such temperature substantially uniform throughout the entire catalytic mass.

- While the salt mixtures are not in direct con tact with any tubes except those through which they how, the other tubes are indirectly affected by any corrosion or embrittlement of, or nitrogenabsorption by, the salt tubes, and it is therefore highly desirable to make these fluid inlet and outlet tubes of the same material as the salt carrying tubes. The inlet and outlet tubes for inflow and outflow of oil vapors and regenerating media are also, in such catalytic apparatus, provided with fins, which are welded thereto, ready weldability of the alloy steel being hence of great importance.

It is also of advantage, for other reasons, to make the said oil inlet and outlet tubes of the described composition, since such tubes of such composition are well adapted to resist corrosion due to the hydrogen sulfide, produced by conversion thereto of the sulfur in the hydrocarbon oil,whichattacks and corrodes plain carbon steel. It is known that resistance to such corrosion may bematerially increased by making the tubes of a low carbon steel containing, in addition to a percentage of manganese within the usual range in carbon steel, a percentage of chromium not less than four per cent to which is usually added about one half of one per cent. of molybdenum. I have discovered that the efilciency of tubes of the described composition to resist corrosion is materially lessened when, as is usually or fre quently the case, an appreciable percentage of salt is present in the oil, since chromium steels are more liable than carbon steels to corrosion by chlorides. While the composition herein described is more particularly intended and adapted for use in the manufacture of the heatexchange salt solution tubes, it has been found that, probably due mainly to their nickel content and their low chromium content, they have the effect of imparting to the inlet and outlet tubes a substantially greater resistance to corrosion by salt than the high chromium tubes with no diminution in their resistance to corrosion by hydrogen sulfide.

In an application filed by me August 28, 1940, Serial No. 354,584 and also in an application, Serial No. 453,713, filed August 5, 1942, as a continuation in part of Serial No. 354,584, I have described catalytic oil conversion apparatus made of alloy steels within the ranges herein described, comprising oil inlet and outlet tubes but not necessarily also comprising heat-exchanging salt-carrying tubes. Where protection from corrosion of the oil inlet and outlet tubes (receiving oil containing sulfur and salt'impurities) is the primary consideration, it is highly desirable in the presence of a catalyst, said apparatus comto' 1.5%, manganese .3

that compositions within the ranges herein specified shall have a silicon content substantially in excess of the chromium content and not less than half the nickel content, as in one of the two typical compositions herein set forth. Since the last named specific composition is not of pronounced advantage over other compositions within the ranges claimed herein for use in the manufacture of heat-exchanging salt-carrying tubes, I have not herein claimed oil inlet and outlet tubes of such specific composition but have made them the subject-matter of the claims in said application Serial No. 453,713.

My invention does not depend for its novelty upon the novelty of the composition per se, my discovery being the adaptability of the composition to the manufacture of the tubular elements, particularly but not exclusively to the salt-carrying heat exchange tubes, in apparatus for the catalytic treatment of hydrocarbon oil, for the purpose and with the result of accomplishing the objects hereinbefore explained.

In claiming iron as constituting substantially all the balance of the composition, I do not exclude the addition, in very small proportions, of other elements whose addition would not unfavorably afl'ect the function of the combination of elements particularly recited. Among such elements one or possibly more of which may be added in very small proportion, are aluminum (which may in part replace the silicon) and elements like columbium, tantalum, titanium and vanadium which are commonly added to chromium steel and chromium-nickel steel but whose addition, in my composition, is unnecessary (even though sometimes advisable) due to the smallchromium content.

What I claim and desire to protect by Letters Patent is:

1. An apparatus for use in processes for conversion of hydrocarbon oils at high temperature prising tubes extending through the catalyst and adapted to carry salts to extract heat from or supp y heat to the catalytic material and being composed of an alloy steel resistive to corrosion, embrittlement and absorption of nitrogen, said alloy containing carbon less than .5%, manganese .25 to 2.5%, silicon .10 to 2.5%, chromium not to exceed 3%, nickel, .70 to 5%, and molybdenum .25 to 3%, the balance being substantially all iron.

2. An apparatus for use in processes for treating hydrocarbon oils at high temperature in the presence of a catalyst, said apparatus comprising inlet and outlet tubes through which oil and regenerating fluid are supplied to and removed from the catalyst and heat exchange tubes extending through the catalyst and adapted to carry salts for extraction of heat from or supply of heat to the catalytic material, said tubes being composed of the alloy defined in claim 1.

3. An apparatus for use in processes for conversion of hydrocarbon oils at high temperature in the presence of a catalyst, said apparatu comprising tubes extending through the catalyst and adapted to carry salts to extract heat from or supply heat to the catalytic material and being composed of an alloy steel resistive to corrosion, embrittlement and absorption of nitrogen, said alloy containing carbon less than .2 silicon .15 to 375%, chromium .5 to 1.25%, nickel 1.5'to 3.5%, and molybdenum .25 to 1.0%, the percentage of nickel exceeding that of any of the other alloying elements, the balance being substantially iron.

4. An apparatus for use in processes for treating hydrocarbon oils at high temperature in the presence of a catalyst, said apparatus comprising inlet and outlet tubes through which oil and regenerating fluid are supplied to and removed from the catalyst and heat exchange tubes extending through the catalyst and adapted to carry salts for extraction of heat from or supply of heat to the catalytic material, said tubes being composed of the alloy defined in claim 3.

5. An apparatus for use in processes for conversion of hydrocarbon oils at high temperature in the presence of a catalyst, said apparatus comprising tubes extending through the catalyst and adapted to carry salts to extract heat from or supply heat to the catalytic material and being composed of an alloy embrittlement and absorption of nitrogen, said alloy containing carbon less than 2%, silicon .15 to 1.5%, manganese .3 to .75%, chromium .5 to 1.25%, nickel 1.5 to 3.5%. and molybdenum over .25 but less than 3%, the total percentageof nickel, chromium and molybdenum not exceeding 6% and the percentage of nickel exceeding that of any of the other specified alloying elements.

6. An apparatus for use in processes for treating hydrocarbon oils at high temperature in the presence of a catalyst, said apparatus compris ing inlet and outlet tubes through which 011 and regenerating fluid are supplied to and removed from the catalyst and heat exchange tubes extending through the catalyst and adapted to carry salts for extraction of heat from or supply of heat to the catalytic material, said tubes being composed of the alloydefined in claim 5.

AARON B. BAGSAR.

steel resistive to corrosion,

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