US2340930A - Reaction chamber - Google Patents

Description

1944- D. L. CAMPBELL ET AL 2,340,930

REACTION CHAMBER Filed Jan. 20. 1940 2 Sheets-Sheet l -Q Q E Q k a Q k 8 '3- 3 n *4 Q Pi Q a 5 V) N MN *Q 14 EM I Feb. 8, 1944.

D. L. CAMPBELL ET AL 2,340,930

REACTION CHAMBER Filed Jan. 20,' 1940 2 Sheets Sheet 2 Patented Feb. 8, 1944 REACTION CHAMBER Donald L. Campbell, Roselle Park, and George B. Cook, Summit, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application January 20, 1940, Serial No. 314,766

2 Claims. (01.196-133) The present invention relates to the conversion of mineral oils into relatively higher and into relatively lower boiling constituents. The invention is particularly directed to an improved reaction chamber in which petroleum hydrocarbons may be held for the desired time period under temperature and pressure conditions adapted to secure cracking. The reaction chamber of the present invention comprises an outer'vessel and a concentrically disposed inner vessel comprising a irangible section whereby the direction of flow of the fluid in said reaction chamber is reversed between said vessels.

It is well known in the art to convert petroleum oils into more desirable products by subjecting feed oils to elevated temperatures and pressures for various time periods, which periods are usually measured in terms of yield per unit throughput, generally termed conversion per pass. The

various variable operation factors are adjusted to secure the desired yield and depend, in general, upon the particular feed material being treated and upon the yield and quality of products desired. In these operations it is essential that the feed oil be maintained at desired temperature and pressure conditions for a suiiicient length of time. Thus, the common practice is to utilize a reaction chamber or so-called soaking drum designed to hold the oil being treated at the desired temperature and pressure for the optimum time period. However, many reactions result in the formation of a hard carbonaceous coke product and it is necessary that this formation be removed periodically from the reaction chamber or soaking drum. Furthermore, in order to secure better results with respect to the overall cracking operation, it is desirable that the flow of oil be reversed, preferably be passed first downwardly and then upwardly in the reaction chamber. For example, at temperatures in the range from 850 F. to 950 F. and pressures in the range from 100 pounds to 750 pounds per square inch gauge, which are the optimum conditions for carrying out in a reaction chamber the thermal cracking of reduced crude with or without cycle as oil, the material present at any point in the reactor exists in two phases, the liquid and the vapor phase. It has been found by experience that in order to obtain the highest possible octane number on the gasoline made in the thermal cracking operation and to obtain the greatest possible yield of this gasoline, it is desirable to crack under the most severe conditions that are practicable. The limitation with regard to the reaction yessel condition is the formation of deleterious coke in this vessel. It has further been found by experiment that within the practical limits mentioned, it is best to crack the components in the vapor phase for a short time at high temperature, and the components in the liquid phase for a relatively longer time period at a lower temperature. This is most readily accomplished by causing the mixture to flow downwardly through one reaction zone and then upwardly through a second reaction zone within the reaction chamber. The liquid phase drops very rapidly through the first zone and rises much more slowly through the second zone. The vapors flow rapidly through the first zone and bubble even more rapidly upwardly through the second zone. Since the reaction absorbs heat, the temperature is lower in the second zone than in the first zone. Thus, the vapors are cracked in the first zone for a relatively short time at a relatively high temperature and pass through the second zone without much further cracking, while the liquid is cracked principally in the second zone for a relatively long time period.

Therefore, suggestions have been made that the reaction chamber comprise an outer vessel having concentrically disposed therein an inner vessel so arranged that the flow of oil through the reaction chamber is reversed between the respective vessels.

Heretofore this type of reaction chamber could not be economically employed commercially due to the fact that a carbonaceous product formed between the outer and inner vessel at the bottom of the reaction zone, making cleaning of the reaction chamber extremely diflicult. Our reaction chamber comprising an outer metallic vessel and a concentrically disposed inner frangible vessel completely solves this difficulty and renders the use of this type of equipment entirely feasible.

When employing our invention the frangible section may be broken and the carbonaceous product readily removed in an efficient and economical manner.

Our invention may be readily understood by reference to the attached drawings illustrating one modification of the same. Figure 1 shows a diagrammatical flow plan of a normal cracking operation. Figure 2 is a sketch illustrating in detail a suitable construction of a reaction chamher in accordance with the present invention. Referring specifically to the drawings, Figure l is a diagrammatical flow plan of a typical cracking operation. For purposes of description it is assumed that the fresh feed is a fraction boiling in the range above about 700 F. In this operation the fresh feed is introduced by means of feed line I into the bottom of primary bubble tower 2 which is provided with suitable fractionating and cooling means. The feed, together with cycle oil, is withdrawn from the bottom of primary bubble tower 2 and introduced into furnace 4 by means of line 3. Furnace 4 is designed so as to secure optimum heat transfer as the feed stock flows through tubes in the radiant and convection sections and to raise the temperature of the oil to cracking temperatures. The total feed is passed from furnace 4 by means of line 5 into soaking drum or reaction chamber 6 which permits additional time under cracking conditions. Reaction chamber or soaking drum 6 comprises an outer vessel having concentrically disposed therein a frangible vessel 56. The feed oil under cracking conditions is introduced into the top of the soaking drum. The oil flows downwardly in the area between vessel 6 and vessel 50 and upwardly within vessel 50. The oil is withdrawn from reaction chamber 6 by means of line I and passed through pressure reducing valve 8. The cracked products pass into evaporator 9 from the bottom of which tar or fuel oil of the desired gravity is removed by means of line 5l, cooled in cooler 52, and withdrawn from the system. The vapors pass overhead from evaporator 9 through line I!) into primary bubble tower 2. Cycle stock accumulates in the bottom of primary bubble tower 2 and vapors pass overhead by means of line I l and are introduced into secondary bubble tower [2 which is provided with suitable fractionating and cooling means. The temperature at the top of tower I2 is controlled so as to produce an overhead distillate of the desired end point which is removed by means of line l3 and condensed in cooler M. The gas is separated from the distillate in distillate drum I 5 and removed by means of line I! while the distillate is removed by means of line l6. Heating oil may be withdrawn from the bottom of tower l2 by means of line 18.

Figure 2 illustrates in detail reaction chamber 6. Reaction chamber 6 comprises an outer shell 20 and an inner concentrically disposed section 2|. Feed material is introduced by means of line 5. The feed oil flows downwardly in the zone between the outer shell and the concentrically disposed vessel and then upwardly within said concentrically disposed vessel. The oil is then withdrawn by means of line I. In a preferred modification of the invention, the inner concentrically disposed vessel comprises at least one lower section frangible in nature. This lower section '22 is of sufiicient length so that under the conditions of operation the coke level will never build up above said frangible section. This section may be attached to a permanent section 23 by any suitable means, as for example, by means of a flange or by threads or by means of wires, rods or removable beads positioned beneath the opened end of the inner vessel. Although substantially the entire area of the inner vessel may comprise frangible material, a preferred modification is an inner vessel, the upper twothirds of which comprises non-frangible materials, as for example, steel, and the lower third of which comprises frangible material. The frangible material may comprise any suitable composition having heat resisting properties. A

preferred composition comprises 30% asbestos fiber and 70% Portland cement. However, other compositions of asbestos fiber and heat resisting binders are satisfactory, as well as tile and concrete using temperature resisting cements and sand or gravel or petroleum coke or coke from bituminous coal as the aggregate.

The process of the present invention is not to be limited by any theory or mode of operation, but only in and by the following claims in which it is desired to claim all novelty in so far as the prior art permits.

We claim:

1. Apparatus for causing rapid downfiow of heated oil and its vapors followed by slower upward flow of the oil and more rapid upward flow of the gases comprising an outer metal cylindrical drum having concentrically disposed therein an inner cylindrical vessel having an upper edge connected to an upper part of the inner surface of said outer drum and lower end not attached to the bottom of said drum, said inner cylindrical vessel having at least the lower part thereof formed of a temperature-resisting material selected from the class consisting of asbestos fibre mixed with binders, tile and concrete, major part of inner surface of said drum and entire outer surface of said inner vessel making an annular chamber of relatively large capacity, said drum having an inlet connected to a mineral oil supply for introducing feed into the top of said annular chamber, said drum having an outlet for withdrawing oil and vapors from top 0f "said inner cylindrical vessel whereby thus the feed flows downwardly through said annular chamber then around the lower edge of said inner cylindrical vessel and upwardly through said inner cylindrical vessel, and said drum also having -a third opening of smaller cross section than that of the drum for removing 'coke 'as required.

2. Apparatus for causing rapid downfiow of heated oil and its vapors followed by slower upward flow of the 'oil and more rapid upward flow of the vapors comprising an outer metallic cylindric'al drum having concentrically disposed therein an inner cylindrical vessel having the upper edge connected to an upper'part of the inner surface of said outer drum and lower end not connected to the bottom of said drum, said inner cylindrical vessel having a frangible part extending from the bottom of said inner cylindri cal vessel about one-third the length thereof and the remainder of said inner cylindrical vessel being composed of an unfrangible metallic material, major part of inner surface of said drum and entire outer surface of said inner vessel making an annular chamber of relatively'large capacity, said drum having an inlet connected 'to a mineral oil supply for introducing feed into the top of said annular chamber, said drum having an outlet for withdrawing .oil and vapors from'top of said inner "cylindrical vessel whereby thus the feed flows downwardly through said annular chamber then around the lower edge of said inner cylindrical vessel and upwardly through said inner cylindrical vessel, and said drum also having a third opening of smaller cross section than that of the drum 'for removing 'c'oke as required.

DONALD L. CAMPBELL. GEORGE 'B'. 'COOK.

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