US2905615A - Preoxidizing feed to fuels coker - Google Patents

Description

United States Patent 2,905,515 PREOXIDIZING FEED To FUELS CGKER No Drawing. Application May 2, 1257 Serial No. 656,508

3 Claims. (Cl. 208-7) The present invention relates to an improved method of increasing the yields of valuableproducts'including high grade coke in the fluid coking for fuels; More particularly it relates to a method of accomplishing the latter by subjecting the charge stock to a preliminary controlled oxidation treatment. i

There has recently been developed an improved process known as the fluid coking process for the production of fluid coke and the thermal conversion of heavy hydrocarbon oils to lighter fractions, e.g.,'see U.S. Patents 2,735,349 and 2,735,806.

The fluid coking process itself is no part of this invention but will be described for completeness. The fluid coking process unit consists basically of a reaction vessel or coker and a heater or burner vessel. In a typical operation the heavy oil to be processed is injected into the reaction vessel containing fluidized particles, e.g., a dense, turbulent, fluidized bed or a transfer line. A staged reactor can be employed' Uniform temperature exists in the coking bed. Uniform mixing in the bed results in virtually isothermal conditions and effects instantaneous distribution of the feed stock. In the reaction zone the feed stock is partially vaporized and partially cracked. Efiluent vapors are removed from the coking vessel and sent to a fractionator for the recovery of gas and light distillates thereform. Any heavy bottoms is usually returned to the coking vessel. The coke produced in the process remains in the bed coated on the solid particles. Stripping steam is injected into the stripper to remove oil from the coke particles prior to the passage of the coke to the burner.

The heat for carrying out the endothermic coking reaction is generated in the burner or heater vessel, usually separate. A stream of all or a portion of the coke is thus transferred from the reactor to the burner vessel, e.g., a fluid bed or transfer line burner, employing a standpipe and riser system; air being supplied to the riser for conveying the solids to the burner. Suflicient coke or added carbonaceous matter is burned in the burning vessel to bring the solids therein up to a temperature suflicient to maintain the system in heat balance. The burner solids are maintained at a higher temperature than the solids in the reactor. Coke, equivalent to about based on the feed, is burned for this purpose. This may amount to approximately 15% to 30% of the coke made in the process. The net coke production, which represents the coke make less the coke burned, is withdrawn and the remaining portion recycled to the reactor to supply heat thereto.

Heavy hydrocarbon oil feeds suitable for the coking process include heavy crudes, atmospheric and vacuum bottoms from crude, pitch, asphalt, other heavy hydrocarbon petroleum residua or mixtures thereof. Typically such feeds can have an initial boiling point of about 700 F., or higher, an A.P.I. gravity of about 0 to 20, and a Conradson' carbon'residuecontent of about 2 to 40 wt. percent. (As to Conradson carbon residue see A.S.T.M. Test D189'41.)

It is preferred to operate with solids having a particle size ranging between and 1090' microns in diameter with a preferred particle size range between and 400 microns. Preferably not more than 5% has a particle size below about 75 microns, since small particles tend to aggolmerate or are swept out of the system with the gases. While coke is the preferred particulate solid, other inert particulate solids such asv spent catalyst, pumice, sand, kieselguhr, Carborundum, and alumina can be employed.

The attractiveness of a fluid coking for fuels process is effected by extraneous economic considerations, e.g., the price of heavy oils and fuel oils and gasoline inventories. It is therefore desirable to be able to 'vary the yields from the process so as to get increased produc-, tion of valuable products such as olefins, oxygenated compounds such as alcohols and phenols and particularly fluid coke. The latter is a high grade product which has high potential utility for premium outlets for petroleurn coke, e.g., foundry sand and electrodes used in aluminum production. l

This'invention provides an improved specific method of increasing the yields of the more valuable products. The method comprises contacting a heavy hydrocarbon oil with an oxygen containing gas at a temperature below one at which the oil cracks, i.e., one in the range o-flOO to 700 F. in an extraneous oxidation zone. The oil is thus oxidized to a minimum combined oxygen content of 2.5 wt. percent. The oxidized oil free of extraneous oxygen containing gas is then fed to a fluid coker for fuels which is operated in the conventional manner. The products, including oxygenated ones, are" taken overhead from the coker and worked up according to standard procedures. The additional fluid coke product is withdrawn from the process also in the conventional manner, eg from the burner. Further details on this operation are supplied below.

The oil is treated as stated previously with an oxygen containing gas. Because of cost considerations air is preferred. Pressure and oxygen concentration can be varied also to produce a smooth operation.

The oxidation treatment is carried out while the oil is in the liquid phase, preferably in a packed tower, in a reactor extraneous to the coking reactor after the oil has been preheated in order to obtain the desired temperature. Excess gas is vented before the oxidized oil is sent further downstream. The use of the extraneous reactor with the venting of the oxygen containing gas results in the sending of the oxidized oil to the fluid coker free of extraneous oxygen containing gas. In this manner product degradation and dilution are avoided. Coking in the pretreating oxidizing. step is avoided by staying below cracking temperatures.

The following example demonstrates the results that can be obtained by the process of this invention.

EXAMPLE The 4 vol. percent bottoms from the vacuum distillation of a South Louisiana residuum Was segregated into two fractions. One a control was fed to the fluid coker. The second was preoxidized for 6 hours with air at 600 F. to a combined oxygen content of 4.5 wt. percent. The preoxidized sample was fed to the fluid coker oper- 3 ating at the same conditions as the control. The results follow:

South Louisiana residuum Fem Control Preoxidized Coking conditions:

Temperature, F 955 955 Pressure, p.s.l.g-. 10 10 Feed Rate, w./hr.lw 0.3 0.3

Wt. percent steam di1uent.... 11 11 Products:

03 Gas, wt. percent on feed-.- 6. 8. 0 Ethylene, wt. percent on feed"--- 0. 8 0.9

Propylene, wt. percent on feed--- 1.1 1. 4 .Butanes, wt. percent on feed"... 0. 4 0. 5 Butenes, wt. percent on feed. 0. 6 0.9

0 0 R, wt. percent on feed 11. 8 11.7 05-430 F., vol; percent on feed 15. 5 15. 9 AH gravity-..- 55. 1 55.1

' Aniline point. 82 75 480 F..1,015.F., pe cen feed. 46.2 38.5 430 F.-1,015 F., vol. percent on feed---. 49. 5 42. 4 API gravity- 22. 4 21. 6

. 1,015 F.+bottom, wt. percent on feed-... 21. 4 9. 5 1,015 F.+bottom, v01. percent on feed 21. 3 9. 5 API gravity- 10. 7 8. 2

- Con. carbon,.wt. percent 15.5 17.8 Vol. percent conversion to 1,015 78. 9 90. 5 Coke, wt. percent on feed 13. 7 30. 9 Suliur content, wt. percent on coke- 1. 9 0.9 Nickel, wt. percent on coke 014 O07 -Vanadium, wt. percent on coke 0016 0008 These results demonstrate that coke formation was increased by more than 100%. The coke product prepared according to this process had the undesirable contaminants sulfur, nickel and vanadium decreased at least 50%. These adversely affect the quality of coke used in making electrodes. Great yield per pass of olefins were also obtained.

Some of the advantages of this invention had been adverted to previously. Other advantages. include simplicity of operation and greater flexibility in the fluid coking operation.

The conditions usually encountered in a fluid cokcr for fuels are also listed below for completeness.

Conditions in fluid coker reactor It is to be understood that this invention is not limited to the specific examples which have been ofiered merely as illustrations and that modifications may be made Without departing from the spirit of the invention.

What is claimed is:

1. In a process for'coking a heavy hydrocarbon oil charge stock by contacting the charge stock at a coking temperature with fluidized coke particles in a coking zone at a temperature in the range of 850 to 1200 F. wherein the oil is converted to product vapors and carbonaceous solids are continuously deposited on the coke particles; removing product vapors from the coking zone and sending a portion of the coke particles from the coking zone to a heating zone to increase the temperature of the coke particles and returning a portion of the heated coke particles from the heating zone to the coking zone, the improvement which comprises contacting the charge stock in the liquid phase with an oxygen containing gas at a temperature below its cracking temperature and one in the range of to 700 F. in an extraneous oxidation zone to oxidize the charge stock to a minimum combined oxygen content of 2.5 wt. percent and then feeding the oxidized charge stock free of extraneous oxygen containing gas to the coking zone whereby increased yields of valuable products are produced.

2. The process of claim 1 in which the oxygen containing gas is air.

3. A process according to claim 1 wherein the oil charge stock is contacted with air for about 6 hours at a temperature of about 600 F. to preoxidize the oil charge to a combined oxygen content of about 4.5 weight percent before the oil is passed to said coking zone substantially free of added air.

References Cited in the file of this patent UNITED STATES PATENTS 2,178,329 Story Oct. 31, 1939 2,336,057 Bell Dec. 7, 1943 2,587,703 Deanesly Mar. 4, 1952 2,781,299 De Rosset Feb. 12, 1957 2,789,082 Barr et a1 Apr. 16, 1957

Claims (1)

1. IN A PROCESS FOR COKING A HEAVY HYDROCARBON OIL CHARGE STOCK BY CONTACTING THE CHARGE STOCK AT A COKING TEMPERTURE WITH FLUIDIZED COKE PARTICULES IN A COKING ZONE AT A TEMPERATURE IN A RANGE OF 850* TO 1200* F. WHEREIN THE OIL IS CONVERTED TO PRODUCT VAPORS AND CARBONACEOUSA SOLIDS ARE CONTINUOUSLY DEPOSIT ON THE COKE PARTICLES; REMOVING PRODUCT VAPORS FROM THE COKING ZONE AND SENDING A PORTION OF THE COKE PARTICLES FROM THE COKING ZONE TO A HEATING ZONE TO INCREASE THE TEMPERATURE OF THE COKE PARTICLES AND RETURNING A PORTION OF THE HEATED COKE PARTICLES FROM THE HEATING ZONE TO THE COKING ZONE, THE IMPROVEMENT WHICH COMPRISES CONTACTING THE CHARGE STOCK IN THE LIQUID PHASE WITH AN OXYGEN CONTAINING GAS AT A TEMPERATURE BELOW ITS CRACKING TEMPERATURE AND ONE IN THE RANGE OF 100* TO 700* F. IN AN EXTRANCEOUS OXIDATION ZONE TO OXIDIZE THE CHARGE STOCK TO A MINIMUM COMBINED OXYGEN CONTENT OF 2.5 WT PERCENT AND THEN FEEDING THE OXIDIZED CHARGE STOCK FREE OF EXTRANEOUS OXYGEN CONTAINING GAS TO THE COKING ZONE WHEREBY INCREASED YIELDS OF VALUABLE PRODUCTS ARE PRODUCED.