US2247126A - Clean circuit powdered catalyst cracking - Google Patents

Description

June 1941- c. E. HEMMINGELR 23 91 CLEAN CIRCUIT POWDERED CATALYST CRACKING Filed Nov, 13, 1939 -A/4PH7WA ALGA S OUTLET somrnvg fiDEu/W JJRUM CATALYST nEc'z/vsznrmlv SYSTEM 11 HEA TING can.

Patented June 24, 1941 CLEAN omcorr POWDERED CATALYST can l coma n. Roger, Wcstfield, N. a, assor to Standard on mvelopment (Jompany, a corporation of Delaware Application November 13, 1939, Serial No. with) 31 on. (Cl. 196-52) The present invention rel-ates to improvements in the art of converting relatively heavy hydrocarbons into lower boiling hydrocarbons. More particularly, the present invention is concerned with the process of producing a hydrocarbon boiling within the gasoline range from a relatively heavy gas oil or reduced crude by subjecting the -material in liquid phase to heat, recovering a mid-boiling fraction, vaporizing this middle fraction and subjecting it in that form to catalytic cracking in the presence of a powdered catalyst suspended in the vapors thereof, removing a major portion of the powderedcatalyst from the reaction vapors, fractionating the vapors and subjecting the heavy bottoms from the fractionating zone to a viscosity reducing operation or a coking operation in the presence of a minor portion of the powdered catalyst.

A principal object of my present invention is to so operate a catalytic cracking operation in conjunction with a viscosity reducing or cok ing operation as to effect an economy of equip ment, heat and steam or other heating fluid.

A second object of my invention is to employ the powdered catalyst which wouldnormally he lost in a catalytic crack-ingoperation of gas oils in the viscosity reducing or coking of a relatively high viscosity and high boiling oil whereby, first,

' a superior gasoline is obtained, and second, the

presence of the powdered catalyst serves to prevent accumulation of tar or other carbonaceous deposits on the inner walls of the reaction coils or vessels by virtue of the abrasive or scouring action of the catalyst suspended in hydrocarbon vapors passing therethrough. Another object of the present invention is to process a crude feed stock in such a manner as to produce a high yield of gasoline of high anti- 2 which may be of the usual bubble plate construction or some equivalent means. The feed stock which is fed into the tower 2 is partially vaporized and at the same time serves to scrub out the powdered catalyst contained in the vapors entering at another point in the tower, as will appear more fully herein-after. To assist in the removal of relatively lower boiling hydrocarbons from the bottoms leaving tower 2, steam is introduced into said tower through line M. The bottoms from the tower 2 are withdrawn through line i, thence discharged into heating coil d, thence into line 5 and from there into a coking or soaking drum G. The overhead product from drum 6 is discharged into line .i and from there into line 8 leading into the tower 2. 'Meanwhile a gas oil. which is taken off as a side stream from column 2 through line 9 is passed into a mining devi-ceill which may be any known liquid andsolid mixing device and at the-sometime powdered catalyst is fed into the mixing device through line 6!. Steam is introduced into mixing device ld-through line 32 to aid in dispersion tar formation.

Other and further objects of this invention will I appear from the ensuing description.

To the accomplishmentof the foregoing and related ends, I provide a process, the apparatus used to carry it out being illustrated in the accompanying drawing in which, the figure shows, diagrammatically a catalytic cracking unit, a fractlonating tower, a viscosity reducing or coking unit, and such accessory apparatus as are necessary to feed the desired streams of vapors or liquids to the various elements and to separate and recover desired products.

In carrying out my invention fresh feed is introduced into the system through line i and .t-rom there discharged into a fj'ractionating tower 55 from h soaking rum 6. An upper middle out i r solids from gases. or vapors.

oil feed. The mixed catalyst and hydrocarbon oil are withdrawn fromthe mixing device it through line i 2 and discharged into a preheating coil It where vaporization takes place and from there withdrawn through line I 5 and discharged through a reaction cell it. From the reaction coil. it the vapors are withdrawn through line i i and conducted into. a cyclone separator it, or some other suitable device adapted to separate Two or more of these separators. may be employed in series. The

separated catalyst is withdrawn from the bottom of the cyclone separator i8 through line l9 and passed to a conventional catalyst regeneration system 20 in which the tarry or carbonaceous ma. terial maybe removed from the catalyst by oxidation or burning under known conditions of temperature, pressure and oxygen concentration of the oxidizing gas. The catalyst is preferably purged before and after regeneration to remove volatile hydrocarbons and oxygen, respectively. The regenerated catalyst is recycled through line H as previously'indicated. Fresh catalyst may be introduced into the system through line it froma feed hopper or some catalyst reservoir.

Referring nowto the overhead product of v the cyclone separator It, the same is disc into line 8 where as previously stated, it is admixed or commingled with the overhead product is taken from tower 2 through line 4| and this fraction which is a light gas oil may be used as a Diesel fuel. The overhead product taken through line 25 contains gasoline, butane and dry gas and this cut may be sent .to a coil 26 where a gasoline fraction is condensed and then passed through line 21 to a receivingdrum 28 where the uncondensed gases may be withdrawn through line 29 and an unstable gasoline withdrawn through line 30.

In order to give a concrete example illustrat- An East Texas crude was topped to remove 50% by volume of the original and the bottoms were fed through line I into tower 2. This reduced crude had an A. P. I. gravity of about 27 About 15% of this feed stock is withdrawn through line 3, the remainder passing up the column, in part, as vapors. Through line 9 a heavy gas oil fraction boiling in the range of from about 500 F'. to 1000 F. is withdrawn and this fraction is pumped to mixing device l'0 in which about 100% to 400% by weight of powdered catalyst is added, together with steam,

the latter assisting in the dispersion of the catalyst in the oil. The catalyst may be an acid treated clay. The size of the catalyst may vary from 100-400 mesh with 90% less than 300 mesh preferred. The mixture of catalyst and oil is then heated in preheater M to a temperature of about 900-950 F. At this temperature it is withdrawn through line l5 and discharged into reaction coil l6 where a temperature of 900-950 F. and a pressure of 25-30 pounds per square inch gauge is maintained for a time of 5 secends. The reaction vapors are then passed through cyclone separator Hi to remove approximately 99.3% of the catalyst and the vapors are then discharged into column 2. The fresh feed which is fed into the column at l contacts the vapors containing about 0.7% of catalyst, by weight, based on the whole of the original oil and this oil serves to scrub out of the said vapors substantially all of their catalyst content. The

bottoms which boil above 1000 F. are withdrawn through line 3 and heated in preheater 4 to a temperature of about 900 F. and a presdrum 6 will depend on the nature of the ori inal.

feed stock and the treat ng conditions to h ch it is subiected in sa d. drum. O erat n in th manner just now outlined, the octane number of the gasoline is much higher than in the conventional method because the asoline is produced in the presence of a catalyst and the catalvst permits higher operating temperatures in the drum due to the fact it scrubs off tarry deposits from the walls upon which they would normally be deposited.

Referring back to the tower 2, the overhead product withdrawn through line 25 is as previously stated condensed in coil 26 and recovered in receiving drum 28. This gasoline has an octane number of 75-80 and the yield is, baseo on the original feed stock, from 40-60%. The fraction withdrawn through line 4| which may be used as a Diesel fuel boils within' the range of from 400 to 600 F.

In the foregoing description, the use of 400% of catalyst on the gas oil fed to the preheating coil M will give a conversion of about 40-50 volume per cent gasoline. When an acid treated clay is employed as catalyst in the case of East Texas gas oil as described, the coke deposited on the catalyst after cracking amounts to about 3% of the gas oil fed to the reaction coil. However, an alternative set of operating conditions which reduce the quantity of coke deposited on the catalyst is possible because of the recycle flow in line 9. By decreasing the catalyst quantity fed to the oil in mixing device In to about 150 weight per cent, the conversion to gasoline would decrease. to about 30 volume per cent in which case, the coke deposit on the catalyst will amount to only about 1% on the feed. Due to the short, time of contact in reactor Hi, the unconverted heavy gas oil is relatively unaffected and undergoes little or no change. As a result, there is little or no increase in the percentage of coke formed from the cycle gas oil as c0mpared to the fresh feed during a. subsequent cracking of the remaining gas oil in the successive passes through line 9. As a result the total coke deposit on the catalyst will amount to only about 2% for a 50% conversion on the total gas oil due to the recycle operation, in comparison to 3% when conversion of about 45% is taken per pass through coil 14 and reactor l6.

While recycling the relatively low boiling converted stock has been disclosed in the catalytic cracking art previously, it is only with powdered catalyst cracking with a contact time of the order of 10 seconds that conversions per pass of 35% may be employed to make possible an ultimate yield of upward of on the total gas oil in which case the light gas oil stream' material boiling below 1000 F. in original stock.

The catalyst may be any adsorptive siliceous material either natural (such as clays) or synthetic (such as silica gel or certain plural gels).

As to the regeneration of the poisoned catalyst, various processes are known to the prior art for the accomplishment of regeneration of solid cracking catalyst by combustion of the contaminating deposits or poisons and any of these may be employed in regenerating the present catalyst.

The various boiling ranges referred to above are to be considered as calibrated to atmospheric pressure.

Numerous modifications falling within the spirit of the present invention will no doubt occur to those who have read the present specification.

I claim:

1. The process of treating a residual hydrocarbon oil, which comprises distilling and fractionating said oil, withdrawing a gas oil fraction from the fractionating zone, mixing a powdered catalyst with the gas oil, subjecting the gas oil containing catalyst in vapor phase to cracking temperatures, thereafter separating the major portion of the catalyst from the vapors, conducting the vapors containing catalyst to a fractionation zone, removing substantially all of the'catalyst from the vapors in the fractionation zone by scrubbing with hydrocarbon oil, withdrawing the oil containing catalyst to a heating zone where the oil is heated to reaction temperature contact with hot vapors in a fractionation zone whereby the said oil is at least partially vaporized, recovering a gas oil fraction from the fractionation zone, mixing a powdered catalyst with said gas oil, subjecting the gas oil, containing catalyst in vapor phase to cracking temperatures, thereafter separating the major portion of the catalyst from the reaction vapors by centrifugal action, conducting the vapors to a fractionation zone where they contact the original oil fed to the system and are scrubbed to remove substantially all of their catalyst content, recovering a liquid fraction containing said last-mentioned catalyst fromthe bottom of the fractionation zone, heating the liquid fraction to cracking temperatures, discharging the heated liquid containing catalyst into a reaction zone, permitting it to remain in said reaction zone for sufficient period of time to cause a substantial conversion of the said oil into fractions boiling within the gasoline range, recovering a vapor fraction from the last-named reaction zone, discharging the vapor fraction into the said fractionation zone Where it contacts the original oil fed to the system and recovering cracked hydrocarbon vapors boiling within the gasoline range produced from the cracking of the gas oil and the treatment of the liquid fraction recovered from the said fractionation zone.

3. The process set forth in claim 2, in which the vapors in the gas oil cracking zone are maintained at a temperature within the range of from about 900950 F; and in which the liquid fraction recovered from the bottom of the fractionating zone is heated to a temperature of about 900 F, While under a pressure of about 300 lbs./

square inch.

CHARLES E. HEMMINGER.

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