US1733799A - Art of cracking hydrocarbons - Google Patents

Description

@da 29y E929.. E. c. HERTHEL. ET A1..

ART OF CRACKING HYDROCARBONS Filed June l1, 1927 @lung Patented Oct. 29, 1929 UNITED 'STATES PATENT .oi-Fica EUGENE C. HERTHEL, OF CHICAGO, ILLINOIS, AND

HARRY L. rnLzEn, or HIGHLAND,

INDIANA, ASSIGNORS-TO SINCLAIR BEFINING COMPANY, OF NEW' YORK, N. Y., A

CORPORATION OF MAINE ART OF ORACKING HYDROCARBONS Application filed June 11,

to form on the heated surfaces ot' the still,`

necessitating the shut down of the still for cleaning between successive runs. ll`he shutting down of a pressure still, the Withdrawal of the charge therefrom, the cleaning of the still, the recharging of the still and the preliminary heating of the still to bring the fresh charge up to cracking conditions, all

i requiretime, and the total amount of time usually required in ordinary commercial operations means a corresponding reduction 1n the proportion of time during which thestill is operating for carrying out the desired cracking operation. llhis invention provides forl greater continuity of operation, less loss of time, and greater production per still per day.

When a pressure still is charged with gas oil or other charging stocks to be cracked, and the charge heated to a cracking tempera.- ture, the cracking takes place in a gradual and progressive manner. The lighter constituents produced by the cracking operatiom which go to make up the pressure distillate',

40 ai'e removed from the still progressively during the cracking operation. Other constituents, such as heavier hydrocarbons formed by the cracking operation, may remain and mix with the charge in the still. There is. also aprogressive formation of asphaltic or pitchlike constituents. For the most part, these constituents remain in solution in the charge during the first part of the run, and they may remain completely in solution in the first part of the run. As the cracking operation convlarly objectionable character, the foi-mation 1927. Serial No. 198,249.

tinues, however, the amount of such asphaltic or pitch-like constituents gradually and progressively increases until, sooner or later, the amount of such constituents exceeds the Vsaturation point.

These asphaltic or pitch-like constituents appearto be of varying properties and charatteristics. With the exception of certain of these constituents which are of particuof coke or carbonaceous deposits upon the heated surfaces of the still is largely avoided so long as these asphaltic or pitch-like constituents are kept in solution in the charge of oil in the pressure still. Certain of these constituents, which appear to be relatively small in amount as coin pared with the total amount of the asphaltic or pitch-like constituents formed, however, are apparently'of a different character and seein to have an increased tendency to deposit on the heated surfaces of the still. Among the heavier constituents produced by the cracking operation which seem to be particularly objectionable are certain sulpliur-containing compounds. With charging stocks which contain sulphur, some of the sulphur compounds appear to undergo cracking to form sulphur-containing constituents, of an asphaltic or pitch-like character, -which are particularly objectionable. Analyses of the deposits 0n the heated surfaces of pressure cracking stills indicate that certain. of these sulphur-containing constituents have a preferential aiinity for the heated surfaces, or'tend to separate out on such surfaces, forining deposits containing bothiron and sulphur in .pro ortions approximating those of iron sulplii e. It is also possible that asphaltic or pitch-like constituents of a colloidal charactei', or even colloidal carbon, formed as a result ofthe crackig operation, tend to separate out on the heating surfacesl of the pressure still in a preferential manner.

In carrying out the present invention, both the nature and the amount of the as haltic orl pitch-like constituents formed in t e charge of oil inthe pressure still as the cracking operation continues are regulated and controlled; certain of these constituents are selectively removed from the still charge by 100 maintaining within and directly exposed to the still charge a body of fullers earth or similar absorbent material and the amount of asphaltic and pitch-like constituents remaining in the still charge by the discharge of pitchladen oil from and the supply of raw oil to the still charge during the cracking operation. The body of fullers earth maintained within and directly exposed to the still charge, is arranged to permit free circulation of the oil in the still. This body of fullers earth does not remove from the still charge all of the asphaltic or pitch-like constituents; but it seems to have a selective action upon certain of these constituents, and apparently removes those constituents which are particularly objectionable from the standpoint ofcausing or promoting the formation of coky or carbonaceous deposits on the heated surfaces of the still. This action of the fullers earth seems to be due in part at least to a selective desulphurizing action of the fullers earth upon the pressure still charge whereby certain of the more `objectionable sulphur-containing constituents of the charge are selectively removed. 'lhe invention thus provides for the removal of more objectionable pitch-like or asphaltic constituentsfrom the pressure still charge by the action of the fullers earth or similar absorbent material and at the same time for regulation of the content of less objectionable ashaltic or pitch-like constituents remaining 1n the still charge by the supply of raw oil and the discharge of itch-laden oil. The

supply of raw oil and t ie discharge of pitchto maintain the concentration of asphaltic or itch-like constituents in the still charge beow saturation.

The invention'will be further described in .connection with the accompanying drawings,

which illustrate, in a solnewhat conventional and diagrammatic manner, one form of pressure still adapted for the practice of the process of the invention; but it is intended and will be understood that the invention is not limited to operations carried, out in the specific construction used for the purpose of illustration. In the accompanying draw- 111 S2 ig. 1 represents, in elevation and partly in section and with parts broken away, a

pressure still adapted for carrying out the process of the invention, Fig. 2 is a sectional lview of the bulk supply drum of the still illustrated in Fig. 1, and Figs. 3 and 4 are enlarged fragmentary sectional views of forms of screenssuitable for retainingr the fullers earthor other absorbent material.

The pressure still illustrated comprises a bulk supply drum 1 and a battery of heating tubes 2 arranged in a heating furnace and circulating connections 3, 4 and 5 including' a circulating pump 6 to provide for circulation of oil from the bulk supply drum upwardly through the heating tubes and back to the bulk supply drum. The heating furnace comprises a tirebox 7 in which fuel is burned for supplying heat to the cracking operation connected to the upper end of a heating flue in which the heating tubes 2 are arranged. The lower end of this heating flue is connected to a stack flue 8. A return flue 9, provided with suitable forcing means, is arranged for recirculating part of the heating gases escaping from the lower end of the heating flue again through the heating flue in admixture with fresh hot products of combustion from the irebox for tempering, in an advantageous manner, the heating gases passing over the heating tubes. A retlux tower 10 is arranged above the bulk`supply drum 1 and connected thereto by a vapor line 1l and a return line 12. This return line 12 is arranged to discharge into the upper end of the circulating connection 3. Vapors from the reflux tower pass through the vapor line 13 to the condenser 14 arranged to discharge into the receiver 15. Connection 16 is provided for discharging the distillate product and connection 17 for discharging uncondensed vapors and gases from the receiver 15. The pressure in the system may be maintained and regulated by means of valve 18, or by suitable valves arranged beyond the condenser. Connection 19 is provided for discharge of tar or pitchladen oil from the pressure still during operation. Connection 20 is provided for pumping out the still at the end of a run and for initially charging the still at the beginning of a run. Feed line 21is provided for supplying raw oil during operation. Cool raw oil may also be supplied through connection 22 in amount just sullicient to cool and lubricate the bearings of the circulating pump 6, or an amount of raw oil considerably in excess of this amount may be sur `ilied through connection 22 during operation.

A basket 23 is arranged within the bulk supply drum of the pressure still and below the normal liquid level therein. This basket is of construction adapted to permit free passage of oil therethrough yet to retain within the basket a body of finely divided fullers earth or similar absorbent material. For example, it may be made up of one or more7 screens of graduated fineness adapted to retain the fullers earth or similar absorbent material arranged between perforated supporting plates, as illustrated in Figs. 3 and 4. This basket is supported in the bulk supply drum free from the sides of the drum so as to permit free circulation of oil through the bulk supply drum from the heating tubes and back to the heating tubes and to provide open liquid paths through the bulk supply drum between the return connections from to the heating tubes. In operation, a body of ullers earth or the like 24 is maintained in this basket. In a pressure still in which the operating charge amounts to something in the neighborhood of 10,000 gallons, this body of ullers earth may amount to four or five tons. It is advantageous to use relatively coarse fullers earth, say from l5 to 30 mesh. In place of fullers earth, other absorbent clays and the like, particularly those which have desulphurizing capacity, are also useful in carrying out the invention. One or more screens may also be arranged on top of the body of fullers earth or the like in the basket 23 to reduce any tendency of the oil circulating through the bulk supply drum to disturb the body of fullers earth or the like.

In carrying out the present invention inthe apparatus illustrated, the pressure still is charged with fresh charging stock in the usual Way. The charging stock may be, for example, gas oil or other suitable charging stock which is to be cracked for the production of gasoline or a gasoline-containing pressure distillate. Due to the selective or pret'- erential action ofthe body of fullers earth or the like, it is possible to treat charging stocks containing constituents which otherwise would tend to cause 'excessive deposition of coky or carbonaceous material. The still charge is brought to the required cracking temperature and pressure in the usual manner. For the production of .gas-

l oline or a gasoline-containing pressure distillate from gas oil, for example, pressures up to 125 pounds per square inch or higher pressures may be used. After the cracking temperature is reached, cracking begins and takes place in a gradual and progressive manner, the lighter vapors forming the pressure distillate escaping to the condenser while heavier vapors are reiuxed and returned to the still from the retiux tower. The character of the distillate product may be controlled by regulating the rate at which raw oil is supplied to the reflux tower. The more objectionable constituents formed in the cracking operation are selectively removed by the body ot' fullers earth or the like, and, before the amount of asphaltic and pitch-like constituents accumulating in the still charge reach the saturation point, the discharge of tar or pitch-laden oil is be un, and the rate at which raw oil is supphed and the rate at which tar is discharged are conjointly regulated to maintain the concentration of asphaltic or pitch-like constituents in the circulating charge below objectionable values, advantageously below the saturation point.

The circulating charge is thus ke t of a regulated pitch content while it is a so subjected to the selective action of the fullers earth or similar absorbent material. While the body of fuller-s earth is completely submerged or immersed in the charge of oil in the still so that it is directly exposed thereto and so that a maximum area of the earth is exposed to a maximum proportion of the still charge, the body of earth is arranged, in carrying out this invention, to permit free circulation through the bulk supply drum in which the body of earth is arranged of the still charge recirculating through the heating tubes. Due to the selective action of the body of fullers earth or similar absorbent material in removing the more objectionable constituents formed by the cracking operation,

a larger proportion of the raw oil. supplied to the operation can be taken ofi as distillate and asmaller proportion discharged as pitchladen oil than in an otherwise similar operation in which the body of fullers earth or the like is not used. This makes possible an increase in still capacity as Well as a saving in fuel.

Fullers earth is a particularly advantageous material for use in the process of the invention. It appears to combine in itselil valuable absorbent desulphurizing and other properties which favorably affect and benefit the pressure still operation.

We claim:

l. An improved method of cracking hythrough heating tubes and back to the bulk supply drum and heating it to a cracking temperature in the heating tubes, taking otf vapors including vapors of the cracked product from the bulk supplyy drum under pressure, maintaining within the charge of oil in the bulk supply drum belovi1 the normal liquid level therein and directly exposed to the oil therein a body of fuller-s earth, said body of fullers earth being arranged to permit free circulationy of oil and to provide open liquid paths through the bulk supply drum from and to the heating tubes, circulating oil supplied from the heating tubes to the bulk supply drum in part directly through said body of fullers earth and back to the heating tubes and in part through said open liquid paths and back ,f to the heating tubes. and sup lying` raw oil to and discharging pitch-la en oil from the char e of oil in the pressure still during the disti ation.

2. An improved method of cracking hydrocarbon oils by distillation under pressure, which comprises circulating a charge of oil in a pressure still from a bulk suppl drum through heating tubes and bac-k to tie bulk supply drum and heating it to a crackinff' temperature in the heatin tubes, taking o vapors including vapors o the cracked product from the bulk supply drum under pressure, maintaining within the charge of oil in the bulk supply drum below the normal liquid level therein and directly exposed to lll) the oil therein a body of desulphurizing mal terial, said body of desulphurizing material being arranged to permit free circulation of oil and to provide open liquid paths through the bulk supply drum from and to the heating tubes, circulating oil supplied from the heating tubes to the bulk supply drum in part directly through said body of desulphurizing material and back to the heating tubes and in part through said open liquid paths and back to the heating. tubes, and sup lying raw oil to and discharging pitch-ladlen oil from the charge of oil in the pressure still dui-iner the distillation.

3. n improved method of cracking hydrocarbon oils by distillation under pressure, which comprises circulating a charge of oil in a pressure still from a bulk supply drum through heating tubes and back to the bulk supply drum and heating it to a cracking temperature in the heating tubes, taking off vapors including vapors of the cracked product from the bulk supply drum under pressure, maintaining-Within the charge of oil in the bulk lsupply drum below the normal liquid level therein and directly exposed to the oil therein a body of fullers earth, said body of fullers earth being arranged to permit free circulationof oil and to provide open liquid paths through the bulk supply drum from and to the heating tubes, circulating oil supplied from the heating tubes to the bulk supply drum in part directly through said body ot fullers earth and back to the heating tubes and in part through saidv open liquid paths and back to the heating tubes, supplying raw oil to and discharging pitch-laden oil from the charge of oil in the pressure still during the distillation, and conjointly regulating the supply of raw oil and discharge ot' pitch-laden oil to maintain the pitch concentration in the charge of oil below saturation.

4. An improved method of cracking hydrocarbon oils by distillation under pressure, which comprises circulating a charge of oil in a pressure still from a bulk supply drum through heating tubes and back to the bulk supplydrum and heating it to a cracking `temperature in the heatinrr tubes, taking oit' vapors including vapors of the cracked product from the bulk supply drum under pressure, maintaining Within the charge of oil in the bulk supply drum below the normal liquid level therein and directly exposed to the oil therein a body of desulphurizing material, said body of desulphurizing material being arranged to permit free circulation ot oil and to provide open liquid paths through the bulk supply drum from and to the heatin(ir tubes, circulating oil supplied from the lieating tubes to the bulk su )ply drum in part direct- 1y through said body of desulphurizing ma- 'terial and back to the heating tubes and in part through said open liquid paths and back to the heating tubes, supplying raw oil to and discharging pitch-laden oil from the charge' of oil in the pressure still during the distillation, and conjointly regulating the supply of raw oil and discharge of pitch-laden oil to maintain the pitch concentration in the charge of oil below saturation.

-An improved method of cracking hydrocarbon oils by distillation under pressure, which comprises circulating a charge of oil in a pressure still from a bulk supply drum through heating tubes and back to the bulk supply drum and heating it to a crackin temperature in the heatin tubes, taking o vapors including vapors ot the cracked product from the bulk supply drum under pressure, maintaining within the charge of oil in the bulk supply drum below the normal liquid level therein and directly exposed to the oil therein a body of solid absorbent material, said body of solid absorbent material being arranged to permit free circulation of oil and to provide open liquid paths through the bulk supply drum from and to the heating tubes, circulating oil supplied from the heating tubes to the bulk supply drum in part directly through said solid absorbent material and back to the heating tubes and in part through said open liquid paths and back to the heating tubes, and supplying raw oil to and discharging pitch-laden oil from the charge of oil in the pressure still during tl'iedistillation.

EUGENE C. HERTHEL. HARRY L. PELZER.

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