US 2929765 A
Description (OCR text may contain errors)
Mamh 1950 R. J. HENGSTEBECK 2,929,765
coxmc APPARATUS Filed April 22, 1957 Hal Liquid Reduced Crude Steam Product Reduced Crude F y 1 INVENTOR.
' fiaberf J. Hengsfebeck Arron/v5) United States Patent COKING APPARATUS Robert J. Hengstebeck, Valparaiso, Ind., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application April 22, 1957, Serial No. 654,243
1 Claim. (Cl. 196128) This invention relates to a liquid phase coking process and an apparatus particularly useful for carrying out the process.
In most prior art coking processes, a heated hydrocarbon oil is introduced into a coking vessel wherein it is completely converted to coke and vapors of the cracked oil. It has recently been found that contrary to this type of operation, it is often desirable to minimize the amount of coking and cracking of the hydrocarbon oil. The prior art techniques and apparatus are not particularly suited to this type of operation. It has been found that the liquid phase coking of hydrocarbon oils provide an easily controlled method for adjusting and minimizing the amount of coke and cracked hydrocarbon vapors formed.
An object of the present invention is to provide a process for the liquid phase coking of heavy hydrocarbon oils, and an apparatus useful for carrying out such a process. Another object is to provide a liquid phase coking process in which the effective throughput of the coking vessel is increased as coke is deposited on the interior walls thereof. A further object is to provide a mild coking process and apparatus therefor which are particularly useful for demetallating a metals-containing reduced crude. An additional object is to provide a liquid phase coking apparatus of simplified design which is useful for extended periods of time without decoking.
In accordance with the invention a hot liquid heavy hydrocarbon oil, such as reduced crude, is introduced while at coking temperatures onto the interior upstanding walls of an enclosed coking vessel. The hot liquid ing vessel. Cooling means are provided in the bottom portion of the coking vessel which may consist of indirect heat exchange means or direct heat exchange with cooled product liquid oil or the like. In operation the charge heavy oil is introduced at coking temperatures onto the feeder disc, which may suitably be of conical shape, and sprayed against the upstanding walls of the coking vessel. The steam jets directed against the feeder disc minimize coke formation and assist in displacing the hot heavy oil from the feeder disc. Liquid heavy oil flows in a film down the upstanding walls and is partially converted to hydrocarbon vapors, which are withdrawn overhead through the vapor outlet line, and coke which is deposited on the side walls. The deposition of coke takes place on the side walls in an irregular fashion, thereby increasing the efiective surface area down which the liquid must flow and also enabling higher effective throughputs per coking unit. When the liquid heavy oil approaches the bottom of the coking vessel it is quenched and a pool of quenched liquid is contained in the bottom portion of the coking vessel. Product liquid oil is withdrawn from a point near the top of the pool of quenched oil. A more thorough understanding of the liquid phase coking process and the apparatus suitable for carrying out the process will be apparent from the attached drawings and the detailed description thereof which follows.
Figure 1 represents a side view in cross-section of the coking vessel and its associated components. Figure 2 is a plan view taken along lines 22 of Figure 1.
Referring to Figure 1, coking vessel 11 is an upright enclosed cylindrical vessel having upstanding walls 12 and an inverted conical section 13 at the bottom of the coking vessel. As illustrated herein a deposit of coke 14 has been deposited on the side walls 12. A conical shaped feeder disc 16 is located in the upper portion of coking vessel 11. The feeder disc has a circular base of smaller diameter than the diameter of cylindrical coking vessel 11. A driving shaft 17 is attached to the apex of the conically shaped feeder disc and extends therefrom through the bushing means 18 to a point outside coking oil flows down the walls and a portion is converted to hydrocarbon vapors and coke, the latter being deposited on the walls. As the hot oil approaches the bottom of the coking vessel, it is quenched to prevent further cracking. Product liquid oil is withdrawn from the bottom portion of the coking vessel and hydrocarbon vapors are withdrawn from the upper portion of the coking vessel. In such a mild liquid phase coking operation, a metalscontaining reduced crude can be substantially demetallated by converting it to coke in an amount approximately equivalent to the Ramsbottom carbon content of the reduced crude charged.
A suitable apparatus for carrying out the process comprises an upright enclosed coking vessel having upstanding walls. Located near the top of the coking vessel is a centrally located (with respect to the distances to the upstanding walls) feeder disc. The feeder disc is rotatable within a given horizontal plane. A liquid inlet for charge heavy oil is provided, which inlet is directed at the upper surface of the feeder disc. Steam jets are located above and directed at the upper surface of the feeder disc. A vapor outlet is located in the upper portion of the coking vessel above the feeder disc. A liquid outlet is located in the bottom portion of the coking vessel and may consist of an outlet conduit which has its point of withdrawal above the bottom of the cokvessel 11. Motor 19 is located outside coking vessel 11 and is attached to driving shaft 17 causing it and feeder disc 16 to rotate. An inlet conduit 21 for the hot liquid heavy hydrocarbon oil charge is located in the upper portion of coking vessel 11. The inlet terminates above feeder disc 16 and is directed down toward the upper surface of the feeder disc. A manifolding conduit 22 for high pressure steam is located in the upper portion of coking vessel 11. Steam jets 23 connect with steam manifolding line 22 and are directed down onto the upper surface of feeder disc 16.
In the inverted conical shaped bottom portion of 'cokingvessel 11 is located indirect heat exchange means 2.4 through which a coolant material flows. Upstanding conduit 26 is positioned in the bottom portion of coking vessel 11 for the removal of liquid product therefrom. Conduit 26 has its withdrawal opening positioned above the bottom of coking vessel 11 at approximately the juncture of the side walls 12 with the inverted conically shaped bottom portion 13. A vapor outlet conduit 27 is provided in the upper portion of coking vessel 11. Hydraulic decoking jets 28 are positioned about the circumference of side walls 12 and protrude therethrough. They are positioned at dilferent heights along the side walls.
Referring to Figure 2 which is a plan view taken along lines 2-2 of Figure 1, the side walls of coking vessel 11 are indicated by 12. The coke deposited thereon is indicated by 14. Feeder disc 16 having centrally located driving shaft 17 is positioned within the axial center of cylindrical coking vessel 11. 4 Hot liquid heavy oil inlet 21 and steam manifolding line v.22 are shown as entering above feeder disc 16 from opposite directions. Hy-
draulic' decokin'g jet nozzles 28 are positioned about zthe" i circumference of side wall -1 2 and :protrudeitherethrough:
In an embodiment of :this invent-ion; hot-liquid reduced crude (heatedit'o cokingtemperatures which areherem- 2- after discussed) is introduced into "coking vessel: 11- by way'of inlet conduit Zl'J The hot liquid is sprayed upon the .upperfisurface of feedendisc 16. The rotating ac-' tion of feeder .disc -'16-p'roduces a spray of hot oil which is thrownagainst side wall 12 of the coking-vessel. High pressure "steam is introduced:through-steam manifolding 'line 22..and thenthroughrsteam jets 23and is directed against. theupper surface .of'the' rotating feeder disc 16. The jets ofsteam'minimize'-:theformation of coke upon feeder disc 16 and also *assistin .displacingtheshot liquid oil from the'upper surface of the feeder disc; The liquid 1 oil.which' is sprayed against sidewall 12. slowly flows down the surface of the. sidewall and is partially converted to hydrocarbon vapors and coke.
In a mild coking operation, the'temperature of the reduced crude as it flows down the walls is frorn750 .to.
925 F., preferably 775 to 825 FQ'To obtain more severe coking, higher temperatures may be employed.
If the charge reduced crude is insufiiciently'heated, aux-' iliary heating means maybe provided about side walls 12 v The residence time of the reducedcrude in its passage down the. side walls may be from 0.1 to minutes based upon to maintain the desired'coking temperatures.
the amount of reduced crude .charged, or even longer if more severe coking. is'desired;- In the'imild coking op-m eration described inthis' embodiment, a 50 percent re-. duced crude which has been heated to .a temperature of about 850 Fjis sprayed onto sidewalllZ. A liquid film of oil ilows down the side wall. The residence time,
based upon oil chargedand effective surface area, is.
approximately 1 to 3 minutes.;: The amount of charge reduced crude convertedto coke. is approximately equivalent to the Rarnsbottom carbon content of the reduced crude charge, which is usually from 1 to 5 percent by weight. crude is cracked to lower boiling. hydrocarbon vapors such as naphtha, etc. Theicoke which is deposited upon the side walls contains substantially all of the metals present in the'reduced crude charged. A highly irregu lar coke surface is formed havinga much greater sur-. The
face areathan that afforded: by thezvessel wall. greater surface areaetfectively increases the capacity of the vessel for coking.
Hydrocarbon vapors which are flashed off when the ApproximatelyZ to.6 percent of the reduced reduced crude is initially introduced into the coking vessel are removed therefrom together with cracked hydrocarbons formed during the coking operation by Way.
of vapor outlet line 27. Depending upon the extent of reduction of the reduced crude and the amount of heavy materials therefrom, anywhere from 5 to 80 percent of is circulated in indirect heat exchangerneans 24 to effect the quenching; If desired, direct heat exchange-to efiect quenching may'bespracticed: by introducing cold gas oil into this bottom section of the coking vessel 11. Product liquid. reduced-crude is withdrawn from near the top of I the pool of quenched oil through the opening in conduit 26.- In thistway, any "heavy'coke particles which may have become dislodged and rest in the very bottom of.
the coking vessel 11 are not removed with the product reduced crude. This product oil is then passed by way of conduit 26 to a catalytic cracking operation. The vapors withdrawn by way of vapor outlet 27 may be partially condensed to produce a higher boiling oil condensate and a vapor stream of steam and hydrocarbons boiling through the'naphtha boiling range. The higher boiling oiLcondensate may also be charged to catalytic cracking operation. Becauseonly a very small portion of the reduced crude is converted to coke and low boiling hydrocarbons (boiling in and below the naphtha range), very-high yields of excellent catalytic cracking charge stock are producedbythe embodiment described herein.
After the coking operation has been carried out for a length of time sufiicient to form a undesirably thick layer of coke 14 on side wall ll, the flow of 'charge'reduced crude is discontinued; Quenched oil remaining in the bottom of coking vessel 11 is withdrawn through bottom outlet 29 and passed'to storage means not shown. The coke which has formed within the coking vessel is removed by any suitable technique. shown herein, hydraulic decoking means are employed. High pressure steam is introduced through steam jets 28 to cause a breaking up and removal of the coke from the side walls; Incomplete removal of the coke is effected the scope of the invention is not limited thereto but includes other charging stocks, coking conditions of temperature, residence time, etc. as well as other types of apparatus such as would be apparent'to those skilled in the art.
What I claim is:
An apparatus'for the liquid p'hasecoking of heavy hydrocarbon oils which comprisesan upright enclosed coking. vessel having upstanding walls, a feeder disc cen trally located within and near'the' top of the coking vessel; means for'rotating said feeder disc in'a horizontal plane, a liquid inlet for charged oil which inlet is directed at the upper surface of said'feeder disc, steam jets directed at theupper surface of said feeder disc, a vapor outlet located in the upper portion of said coking vessel above said feeder disc, cooling means located in the bottom portion of said coking vessel and a liquid outlet located in .the bottom portion of the coking vessel having its withdrawal opening above the bottom of said coking vessel.
References Cited in the file of this patent UNITEDSTATES PATENTS 1,293,366 Murray et al. Feb. 11, 1919 1,470,359 Greenstreet Oct. 9, 1923 1,654,201 Wilson et al. Dec. 27, 1927 1,934,873 Nelson Nov. 14, 1933 1,974,797 Rachat Sept. 25, 1934 1,978,593 Nelson Oct. 30, 1934 2,128,502 Snow Aug. 30, 1938 2,255,060 Houdry Sept. 9, 1941 2,326,525 Diwoky Aug. 10, 1943 2,626,892 McCulley et al. a Jan. 27, 1953 2,717,855 Nicholson Sept. 13, 1955 In the embodiment