US1905071A - Method of treating hydrocarbons - Google Patents

Description

pril 25, 1933. E, E" STEWART 1,905,071 I METHOD oF TREATING HYDROCARBONS Original Filed Nov. 6. 1926 2 Sheets-Sheet l l A T'ToRNEY April 25, 1933.

E.; STEWART METHOD OF TREATING HYDROCARBONS Original Filed Nov. 6. 1926 2 Sheets-Sheet 2 INVENTOR BY f afa E. ffm/mf ATTORNEY Patented Apr. 25, 1933 f UNITED STATES'PATENT oFF'IcE EDWARD E. STEWART, oF WICHITA FALLS, TEXAS METHOD oF TREATING HmmocAmsolvs i assure Original application illed November 6, 1926, Serial No. 146,671. 4Divided and this application Viled February 11, 1929.

My invention relates to methods for treating hydrocarbon oils for the purpose of separating and extracting the lighter from the heavier hydrocarbons, and particularly for eil'ecting separation of natural gasolines without injury to their texture and/or for recovering additional gasoline by breaking down or cracking the heavier hydrocarbons,

the principal object of the invention being to treat oils of diiierent gravity and gasoline content according to l(their nature forproducing a maximum yield of gasoline, this application being a division from my copending application, -Serial No. 146,671

which has matured into Patent No. 1,798,338,

March 31, 1931 whereinv apparatus adapted to use the method was illustrated and described. f Y

It is an established fact that light gravity liquids such as kerosene, light distillates and L gasoline contain more hydrogen than the heavier oils. It is also a well known fact that less coke is formed in the cracking chamber when hydrogen is present therein in suilicient amounts; and that 'when hydrogen is deficient and particularly when charging stock that has been cracked is used, an excess amount of coke is deposited. It is'therefore, a particular object of my invention to pro'- vide a method of treatin hydrocarbons whereby the objectionable co ing effects may be obviated and particularly whereby hydrogen may be provided for in the stream of fluid subjected to the treatmentto prevent the formation of an excess amount of coke and a zero cold test fuel oil may be producedv free from suspended coke and bottom settlings. l i

In accomplishing theseand other objects of the invention, I have provided improved methods which will be describedy in selected aspects as used in the operation `of my appa,- ratus substantially that illustrated and described in above mentioned co-pending application and illustrated in the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of an oil refining and treating apparatus whereby my method may be employed, some of the parts being broken away for better illustra-tion.

Serial No. 338,951. l

Fig. 2 is an enlarged, longitudinal, secinitial separation ofvapors is eiiected.

Fig.,3 is an enlargedvvertical section of the primary separator tower.

Referring more in detail tothe drawings:

1 designates anv ordinary storage tank constituting a source of supply of oil to be treated. Leading from the tank 1 is a line 2 whereby oil is drawn from the supply by a pumpvB and delivered under pressure into a charging still 4. The oil is heated in the still 4 to a. temperature of about 500 degrees F and forced through a line 5 and branch 6 into the upper portion of a vaporizer or blendin zone illustrated as a bubble tower 7, where 1t is delivered downwardl as a shower .through a nozzle 8. The 6 carries a valve 9 for a purpose presently described.

When the apparatus is in operation and the vaporizer being supplied from the crackingA still, as presently described, cracked vapors released in the vaporizer rise through the shower of liquid and, absorbing the lighter elements of the oil along with` the water vapors, pass off from the top through a vapor line 1() to the primary separator tower 11, entering near the bottom of the tower. When the apparatus is in operation, cracked vapors enter the bottom and straight run vapors and liquid enter at the top of the vaporizer, forming a counter current of va pors and liquid, the cracked vapors rising through a' liquid shower, a spreading element and bubble plates, electing absorption or commingling ofthe lighter with the lheavier hydrocarbons, so that a-large portion of the non-condensibleyapors which are ordinarily ranch Y Ational view of the bubble tower, wherein the are passing to the condenser as described,

Loil througha cracking'J still 22, wherein the oill is heated to a temperature of approximately 890 degrees F. and wherein a pressure I f of approximately 250 to 300 pounds is maintained. Theforce frm the pump 21 car' -ries the oilthrough the still and out through a transfer line 23 and a depending terminal 24 into the bottom of a primary cracking tower 25, the terminal 24 being provided with a hand valve 27. The tower 25 is provided with a number of petcocks 25 spaced vertically for the of contents o the tower.- Oil entering the first cracking tower as liquid rises through the tower. to an outlet line 28 at or near the top of the tower, through which the liquid is conducted to near the top of a second high pressure cracking tower 29, also provided with pet cocks 29- as and for the purpose specified in connection with the first crackintowe'r.

he oil passesI through the second cracking tower 29 inthe form of vapor to a pressure relief line 30, opening to the tower near its lower end, through which the vapors are conducted to near the bottom of a 'secondary separator tower 31. The line30 carries a.

' hand valve 32. An emergency connection between the second cracking tower and the secondary separator tower is provided in the line 33, which leaves the tower 29 and enters the tower 31 at elevations'above the line 30,

the emergency line being also provided with a hand valve 34. The vapors entering the secondary separator'tower expand, releasing the pressure in the circuit, the `cracked components passing ofi from the top of the sec ondaryl separator through a vapor line 35 tor tower through a tar line 36 and passed v.through a cooling coil 37 into a storage tank 38. The tar line 36 is valved as at 36 for controlling pressure and iow through said line.

'Should excessive pressure be built up in.

the s stem, initial relief is aii'orded through a sa ety valve 39 in a line 40, leading from purpose of determining levels the top ofthe primary cracking tower 25 to the bottom of the vaporizer, this valve being set for operation at approximately 25 pounds above the normal system pressure.

A secondary relief is afforded through a valve 41 in a line 41', leading from the top of the secondary cracking tower 31 to near the bottom of the va orizer, thisvsecond relief valve being pre erably set at approximately 50 pounds above the normal pressure. Consequently, should the relatively small line 30 leading from the secondary cracking tower to the secondary separator be insuiiicient to carry oithe vcontent of the system with suiiicient rapidity and excessive pressure be built up, the relief means vwhich I have provided will operate and prevent dam- `age to the apparatus or interruption of the treating process.

rlhe primary cracking tower may be relieved at any time through a line 42, leading to the coling coil 37. The line 42 communicates with the tower through a line 43 leading from the bottom of the tower and provided with a hand valve 44; through a line l45 leading from the side of the tower, slightly above the bottom and providedwith ahand valve 46 or through a line 47, leading toa higher elevation in the tower and provided with a hand valve 48.

While treatment of oil with my apparatus reduces accumulation of coke to a minimum, there is, nevertheless, some accumulation in the cracking towers and itis for this reason that I providev for drawing off of the oil from the towers at different elevations, the lower outlets being employed when there is a minimum accumulation in the towers and theA upper outlets according to the depth of the coke. The secondary cracking tower may be drained into the` line42 through a branch 50, provided with a hand valve 51. The expansin tower 13A may be drained through a line 52 and cooling coil 53 into a storage tank 54.

Should it'be desirable to drain the still, as in the event of burning out a tube, the relief may be e'ected through a line 55, connecting the line leading from the pump 21 to the stillv with the line 42 leading to the cooling coil 37. The line -55 is provided with a hand valve 56, which is normally closed but when opened, will permit flow of liquid under the still pressure back through the cooling coil to rapidly relieve the still of the fluid and its pressure, the cooling coil reducing the temperature of the liquid so that by the time the latter reaches the storage tank,

it is below thesiiashing point, thereby obviating the danger incident to release of the oil into atmosphere under the usual still temperature.

The methodl of operation of recovering gasoline from crude oil described in connection with the description of apparati/lecontemplates the collection of the straight run a and cracked gasoline in thesame condenser.

Should it be desirable to separate thestraight run and the cracked gasoline, this may be effected by closing the valve 9 in the line 6 leading from line 5 to the vaporizer and conducting the vapors initially delivered to the system through a line 57 into the top of the separator 11. The straight run gasoline vapors are then carried olf through the line 12 to the condenser asl originally described, the heavier components collecting as liquid in the bottom of the separator and afterwards being drawn oil' through the charging still for cracking.

By a modification of the method I separate the straight run and crackedvapors by directing the cracked vapors 'into a separate condenser 58 connected with the line 10 through a branch 59 having a hand lvalve 60. For the operation of separately collecting the straight run and cracked gasoline, the valve 9 in line 6 and a valve 61 inline 10 are closed, and the-valve 62 in line `57 and valve 60 in line 59 are opened. When all of the gasoline is to be collected together, the valve/ 62 in line 57 and the valve 60 in line 59 are closed, and valves 9 and 61 are opened to properly direct the How.

It is desirable to maintain a proper volume of circulating fluid in the system at all times during operation of the apparatus. Should I the accumulation in the separator 11 fall below a desirable level, fresh crude oil may be supplied from a tank 63 connected with the pump `19 through a pipe 2O leading to pump 21 through a branch 64. The branch 64 is normally closed by the ordinary tank valve (not shown). v o

As a modification of the mode of operation heretofore described, I provide additional elimination of coke by passing the crude oil through the charging still at a higher temperature and ressure, such as 800 degrees F. and 100 poun s pressure, thereby eliminating all heavy fuel oils, cokes and tars, passing only gas oils and wax distillates vto the extreme cracking zone. l Under this mode of operation the hot liquid under high pressure is passed initially to the secondary separator towerY 31 through a line 65, provided with an automatic control valve 66 set to hold the desired pressure in the still, the valves 9 and 62 in the line 5 and branch 57 being closed when the system is so operated. The liquid passing to the secondary separator tower separates into vapor land heavy liquid, the vapors constituting approximately 85% of thewhole and passing out through pipe 35 into the vaporizer, lthe fuel ,oil from initial charging stock being drawn off from the secondary separator and fuel oil from the crackin zone being drawn 0E through the bottom o the secondary separator and cooling coil into the tank 38. The' vapors passing into the vaporizer are ypartially condensed, the lighter components passing on to the separator 11 where further condensation takes place, the gasoline vapors eventually reaching the condenser, and liquid condensed in the separator 11 and in the vaporizer accumulating in the bottom. of the separator and being pumped through the i closed and liquid from the charging tower delivered throughthe shower into the vaporizer, the vapors passing off to condensation 1 and the heavier components back trappingin the bottom of the separator tower 11 and being drawn of through a backtrap line 68 controlled by a valve 68 and through a cooling coil 69 into'ra 'storage tank 70. "l In a preferred form' of apparatus for using the method, a spreader bed 71 is provided in the vaporizer below the shower nozzle" 8, which may be supplied and emptied through a manhole 72, and a series of bubble plates 73 are positioned above the nozzle, each comprising upwardly directed necks 7'4 and heads 75 seated on the plates about the necks and having toothed lowenedges 76 through which the vapors pass to relief at the top of the tower. i

One advantage gained with my method is that the non-condensable gases passing through the shower of charging stock are adbsorbed in the latter and recovered along with the'condens'able vapors, thereby ysaving la great proportion of this useful component which would be lost if allowed to'pass freely from the tower.

Particular attention is `called to the steps `l i whereby straight run'vapors and vaporous products of cracking are blended, -liquid levels in expansion zones are avoided and reflux condensates and charging stock yare blended and passed through a liquid seal to conserve the hydrogen and reduce the percentage ofvcarbon in spent oils, lfor circulation through the cracking still. l

Unvaporized portions of the charging stock are blended with vaporous products of cracking in the vaporizer 7 and pass to the bottom of the separator 11 to forma pool or 1i uid seal, pressure in the separator 11 being su stantially at atmosphere. The composite cracking stock is withdrawnfrom the pool in a manner tomaintain the level of the pool so that the cracking stock will move fromthe vaporizer 7 to the cracking still substantiallywithout expansion or lossof vapors.

The level of the pool may be controlled by the speed of the pumps and also by delivering additional supplies of oil from the supply tank 63.

The components of the pool act as an absorbing unit to materially lessen the losses of p uncondensable vapors. The spent oils that have passed one or more times through the systemare blended with the incoming chargin stock so that they are reconditioned and bui t up. The percentage of hydrogen in recirculated cracking stock is materially increased and the percentage of vcarbon is materially decreased.

Cracking stock heated to approximately 890 F. under 250'to 300 lbs. of pressure-is delivered downwardly into the lower end of the cracking tower 25, the tower being maintained full of lliquid under pressure, whereby all the oil must move over substantially the length of the tower tothe outlet'at the top thereof and the temperature of the liquid is loweredk to 100 F.

The *secondaryA cracking tower is maintained full of vapors and at a temperature above the final boiling point ofthe charging stock. The low pressure expansion zone is proportioned to the stream of vapors, and pressure approximately 5 lbs. is maintained therein so that 2 to 4%.of the stream will be condensed, and thus only the heavier hydrocarbons will be converted to liquid Jform.

VThe liquid is withdrawn under restrictedv iow to limit the level in the separator lvand to comprise fuel oil -of zero cold test 4and low gravity, for example, gravity 6 to 8.

I have not attempted to describe every detail of structure embodied in the apparatus, such as gauges and the like, as this is ordinary equipment, and the method'may be used with other apparatus.

It is apparent, therefore, that I have prov vided amethod whereby various treatments including heating a stream of oil under presf sure to cracking temperature, passing the i substantial accumulation of liquid oil thereof oils for. the recovery of gasoline may be effected,l the selection of modes of operation being optional,'and lwith which the treatments described may be eected withv a lmaterial saving in labor and fuel.

What I claim and desire t'o secure by Letters Patent is: I l

1.Y The method vof treating hydrocarbon oil heated stream of oil through a confined column of the hotl oil at cracking temperature in a primary cracking zone, maintaining pressure on saidcolumn of hot oil to retain the column in liquid state, passing oil from said primarycracking zone to a secondary cracking zone, drawing oil' liquid from lthe secondary cracking zone at a rate to prevent in, passing vapors from said secondary cracking zoneto a vapor reaction zone, controlling fiow of vapors to the vapor reaction zone to maintain relatively high pressure in the secoil from said separating zone, withdrawing vapors from the primary separator zone, drawing liquid rimary separating zone for supply of cracking stock, and delivering preheated initial charging stock to the blending zone for comminglmg of vapors and condensate of said initial stock with vapors and condensate of the cracked oil.

2. The method of treating hydrocarbon oil including heating a stream of oil to cracking temperature, passing vsaid heated stream through a body of hot oil' supplied by said stream in a primary cracking zone, maintaining the body of hot oil under relatively high pressure to maintain the same in liquid form, passing oil in liquid form from the primary cracking zone to a secondary cracking zone,

withdrawing liquid oil from the lsecondary cracking zone at a rate to prevent substantial accumulation of liquid oil therein, passing vapors from the secondary crackin'g zone to a vapor reaction zone, restricting flow of vapors from the secondary cracking zone to maintain relatively high pressure in said zone,- passing vapors from the vapor reaction zone to a blending zone, controlling iow of vapors from the vapor reaction zone to maintain approximately atmospheric pressure therein, condensing heavier vapors of the cracked stock in the blending zone, drawing off vapors from the blending zone, de-

livering condensate from the blending zone Vto a primary separating zone, delivering heated initial charging stock to. the system to maintain supply of liquid cracking stock in the primary Vseparatin zone, and delivering liquid oil from the bo y thereof 1n the prlmary separating zone for supply of crackmg stock.

3. The method of treating hydrocarbon oil including heating a stream of oil to approximately 500 F., discharging said stream of oil into a blending zone, collecting unvaporized portions of said stockl in `said zone, passing said unvaporized portions of said stock into a body of liquid oil in a primar separating zone, withdrawing liquid oil rom the separating zone'for suppy of cracking stock at a rate to maintain a bo y of liquid in said zone, heating the cracking stock, delivering the heated cracking stock to. a primary cracking zone, maintaining pressure in said `zone to retain the cracking zone full of liquid oil, passing liquid oil from the primary cracking zone to a secondary separating zone, taking oli vapors and passing them through a vapor reaction zone, removing unvaporized'oil at a rate to prevent substantial accumulation of liquid oil in the secondary separating zone, passing vapors from the vapor reaction zone upwardly through ,unvaporized portions of incoming initial Vcharging stock in the blending zone, restricting outflow of vapors from the 'vapor reaction zone to maintain a pressure of approximately five pounds per square inch in said vapor reaction zone, drawing olf condensate formed from the vapor reaction zone, passing vapors from the blending zone to the primary separating zone tol mingle withvapors rising from the body of oil therein, and condensing and collecting the c ombined vapors from said primary separating zone.

In testimony whereof I affix my signature.

EDWARD E. STEWART.

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