US2872383A - Desulfurization of high sulfur fluid coke particles - Google Patents

Description

United States Patent bEsULFURIzATIoN OF HIGH SULFUR FLUID COKE PARTICLES John J. Owen, Baton Rouge, La., and John Fedirko,

Elizabeth, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware N0 Drawing. Application July 7, 1954 Serial No. 441,951

2 Claims. (Cl. 202-31) 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 a dense turbulent fluidized bed of hot inert solid particles, preferably coke particles. Uniform temperature exists in the coking bed. Uniform mixing in the bed resultsin virtually isothermal conditions and effects almost instantaneous distribution of the feed stock. In the reaction zone the feed stock is partially vaporized and partially cracked. Productvapors are removed from the coking vessel and sent to a fractionator for the recovery of gas and light distillates therefrom. 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.

i The heat for carrying out the endothermic coking reaction is generated in the'burner vessel. A stream of coke is transferred from the reactor to the burner vessel employing'a standpipe'and riser system; air being supplied to the riser for conveying the solids to the burner.

Suflicient coke or 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. About 5% of coke, based on the feed, is burned for this purpose. This amounts to approximately 15% to of the coke made in the process. The unburned portion of the coke represents thenet coke formed in the process and is withdrawn.

Heavy hydrocarbon oil feeds suitable for the coking process are heavy or reduced crudes, vacuum bottoms,

pitch, asphalt, other heavy hydrocarbon residua or mixtures thereof. Typically, such feeds can have an initial boiling point of about 700 R, an A. P. I. gravity of about 0 to 20, e. g., 1.9, and a'Conradson carbon residue content of about 5 to 40 Weight percent. (As to Conradson carbon residue see ASTM Test D180-52.)

It is preferred to operate with solids having an average particle size ranging between 100 and 1000 microns in diameter with a preferredaverage particle size range be:

tween 150 and 400 microns. Product coke has an average Preferably not more than 5%v size of 250-450 microns. has a particle size below about microns, since small particles tend to agglomerate or areswept out of the system with the gases. P

The method of fluid solids circulation described above is well known in the prior art. Solids handling technique is described broadly in Packie Patent 2,589,124, issued March 11, 1952.

Fluid coking has its greatest utility in upgrading the quality of low grade petroleum vacuum residua and pitches from highly asphaltic and sour crudes. 'Such residua frequently contain high concentrations of sulfur, e. g., 3 wt. percent or more, and the coke product produced from these high sulfur feeds are also high in sulfur content. In general the sulfur content of the coke product from the fluid coking process is about 2 times the sulfur content of the residuum feed from which it is produced. The sulfur content of coke from sour residue may range from 5% to 8% sulfur or more. The high sulfur content of the coke product poses a major problem in its eflicient utilization. For most non-fuel or premium fuel uses a low sulfur content coke, below about 3 wt. percent sulfur is required. For example, low sulfur content coke is desired for the manufacture of phosphorus, for the production of calcium carbide, for lime burning in the manufacture of soda ash or other alkalis, for various metallurgical application, for the production of electrode carbon for various electrochemical applications such as the manufacture of aluminum and the like.

The conventional methods of removing sulfur from cok from ordinary sources with gaseous reagents have in general not been too satisfactory. The results are even poorer when these procedures are applied to fluid coke. Delayed coke is more porous than fluid coke and the interstices are more connected and larger than in fluid coke. A treating gas consequently has relatively -easy access to the sulfur. Fluid coke, on the other hand, is laminar in structure and may comprise some 30 to superposed layers of coke. Thus it is diflicult for a reagent to penetrate more than a few outer layers. These difficulties in desulfurizing fluid coke are further aggravated by the higher than normal sulfur content of this coke derived from high sulfur petroleum feeds.

The invention provides an improved process for desulfurizing and activating high sulfur containing fluid coke particles-with a gaseous reagent. The process comprises treating the product coke particles with a hydrogen-containing gas at controlled, elevated temperatures and pressures whereby the sulfur content is reduced to below 3 wt. percent.

The conditions, as will be elaborated below, have been found to be important, as those outside the ranges stated give vastly inferior results.

Thus the temperature utilized is in the range of from 1100 F. to 1800 F., preferably 1300" F. to 1500 F.

The pressure utilized is in the range of 30 to 300 p. s. i. g. and preferably 50 to 250 p. s. i. g.

The time interval utilized depends on the temperature and pressure but is in the rangeof 20 minutes to 5 hours and preferably 30 to 90 minutes.

The partial pressure of hydrogen utilized is in the range of 25 to 250 p. s. i. g. and preferably 50 to p. s. i. g. with 1500 to 6000 v./v./hr., preferably in the range of 2500 to 5000 v./v./hr. The hydrogen containing gas can be obtained from the gas produced in the poker after removal ofmost of the hydrocarbons formed in the coking operation. Other sources of hydrogen include the pure gas or the tail gas from a hydroformer. Steam can be employed as a diluent. The hydrogen containing gas is preferably treated in the conventional manner to remove hydrogen sulfide and other sulfur containing compounds before use. The high partial pressure and concentration of hydrogen results in the stripping of hydrogen sulfide as formed.

The treatment of this invention can be carried out in a-fluidized or batch manner.

It is to be understood that where the term high percentage of sulfur is utilized herein it connotes more than about 4 and in cases of high. sulfur crudes more than about 7 weight percent total sulfur.

This invention will be better understood by reference tothe following example of its use assummarized in the following table:

EXAMPLE I Desulfuriz tian of petroleum fluid Cake with yd and other gases at 75 p. s. i. g.

Treated Product Time of Temp. of

Gas Treat, Treat,F. Wt. Wt.

min. Percent Percent Yield Sulfur of Coke in Coke These data demonstrate the marked superiority of hydrogen over other gaseous reagents for the purpose of this invention in terms of sulfur reduction and yield. The improvement in sulfur removal for 1300" F. as compared to 1000 F. is also significant.

EXAMPLE II The following data for treating petroleum fluid coke with hydrogen at atmospheric pressure indicate the necessity for treating at superatmospheric pressures.

Time of Wt. Per- Gas Treat, Temp. of cent Sulfur min. Treat, F. in Treated Ooke These data show that there is practically no improvement in sulfur content in the absence of superatmospheric pressures even at more elevated temperatures.

EXAMPLE III The following data show the results of treating at 75 The lowering of the sulfur content to below 1.7 wt. percent should be particularly noted.

The tests were conducted in the following manner. The coke to be treated was supported in a stainless steel reactor on a ZOO-mesh stainless steel screen. A similar screen was placed in the top of the reactor to prevent entrainment. After purging the system with nitrogen, heating was started while the treating gas was passed through the system at the desired pressure. The time of treatment given in the examples is the time of treatment after the reactor contents reached the desired treating temperature. Treating gas rates, measured by the wet test meter, were in the range of 1.5 liters/min. (STP) for about 20 grams of coke. After treating for the desired time the reactor was cooled, and the coke was removed for inspection and analysis.

In order to express this information more fully the following conditions of operation of the various fluid coking components by which the fluid coke is prepared are set forth below.

Conditions in fluid coker The hydrogen treatment can be advantageously conducted while the coke particles are in a fixed bed or a moving fixed bed. However, a fluid bed type operation may also be employed for the hydrogen treatment. The choice of the method of contacting the coke with hydrogen will often depend upon the type of equipment available for this operation.

The advantages of the process of this invention will be apparent to the skilled in the art. The sulfur content is reduced to acceptable levels by an easily controlled economical process and satisfactory yields are maintained.

It is to be understood that this invention is not limited to the specific examples which have been offered merely as illustrations and that modifications may be made without departing from the spirit of the invention.

What is claimed is:

1. A process for desulfurizing coke particles containing a high percentage of sulfur, said particles having been produced by contacting a heavy petroleum oil coking charge stock at a coking temperature with a body of coke particles maintained in the form of a dense turbulent fluidized bed in a coking zone, wherein the oil is converted to product vapors and carbonaceous material iscontinuously deposited on the coke particles, removing product vapors from the coking zone, burning a portion of coke particles removed from the coking zone in a separate heating zone to increase the temperature of said coke particles, returning a portion of the heated coke particles from the heating zone to the coking zone and withdrawing product coke particles, which comprises contacting the product coke particles for a time interval of from about 30 minutes to ,5 hours with hydrogen-containing gas in a treating zone maintained at a temperature in the range of about 1300" to 1500 F. and under a pressure in the range of about 50 to 25.0 p. s. i. g., the partial pressure of the hydrogen being in the range of about 25 to 250 p. s. i. g., and the amount of hydrogen introduced into said treating zone being in the range of about 1500 to 6000 v./v./hr., whereby the sulfur content of the product coke particles is reduced to below about 3 weight percent.

2. The process according to claim 1 in which the product coke particles to be treated have a sulfur content in the range between about 4 and 8 weight percent.

References Cited in the file of this patent UNITED STATES PATENTS Odell et al. May 6, 1952 Smith et al. Nov. 9, 1954 Mattox Jan. 25, 1955 Gorin Sept. 13, 1955 McKinley Dec. 6, 1955 Mason Oct. 18, 1955

Claims (1)

1. A PROCESS FOR DESULFURIZING COKE PARTICLES CONTAINING A HIGH PERCENTAGE OF SULFUR, SAID PARTICLES HAVING BEEN PRODUCED BY CONTACTING A HEAVY PETROLEUM OIL COKING CHARGE STOCK AT A COKING TEMPERATURE WITH A BODY OF COKE PARTICLES MAINTAINED IN THE FORM OF A DENSE TURBULENT FLUIDIZED BED IN A COKING ZONE, WHEREIN THE OIL IS CONVERTED TO PRODUCT VAPORS AND CARBONACEOUS MATERIAL IS CONTINUOUSLY DEPOSITED ON THE COKE PARTICLES, REMOVING PRODUCT VAPORS FROM THE COKING ZONE, BURNING A PORTION OF COKE PARTICLES REMOVED FROM THE COKING ZONE IN A SEPARATE HEATING ZONE TO INCREASE THE TEMPERATURE OF SAID COKE PARTICLES, RETURNING A PORTION OF THE HEATED COKE PARTICLES FROM THE HEATING ZONE TO THE COKING ZONE AND WITHDRAWING PRODUCT COKE PARTICLES, WHICH COMPRISES CONTACTING THE PRODUCT COKE PARTICLES FOR A TIME INTERVAL OF FROM ABOUT 30 MINUTES TO 5 HOURS WITH HYDROGEN-CONTAINING GAS IN A TREATING ZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF ABOUT 1300* TO1500* F. AND UNDER A PRESSURE IN THE RANGE OF ABOUT 50 T/ 25/ P. S.I. G., THE PARTIAL PRESSURE OF THE HYDROGEN BEING IN THE RANGE OF ABOUT 25 TO 250 P . S. I. G., AND THE AMOUNT OF HYDROGEN INTRODUCED INTO SAID TREATING ZONE BEING IN THE RANGE OF ABOUT 15// TO6000 V./V./HR., WHEREBY THE SULFUR CONTENT OF THE PRODUCT COKE PARTICLES IS REDUCED TO BE LOW ABOUT 3 WEIGHT PERCENT.