US1754136A - Process and apparatus for converting heavy hydrocarbon oils into lighter products - Google Patents

Description

2 Sheets-Sheet 1 F. S. WOlDlCH PROCESS AND APPARATUS FOR CONVERTING HEAVY Filed July 8, 1924 HYDRQCARBON OILS INTO LIGHTER PRODUCTS April 8, 1930.

Aprfl 8, 1930. F. s. WOHDHCH 1,754,136

- PROCESS AND APPARATUS FOR CONVERTING HEAVY HYDHOCARBON OILS INTO LIGHTER PRODUCTS Filed July 8, 1924 2 Sheets-Sheet 2 Patented Apr. 8, 1930 FRANUIS SALES WUIJDICH, 03F SAPULIIPA, OKLAHOMA PROUESS AND APPARATUS FOR CONVERTING HEAVY HYDROCARJBUN UJL'ILS WWO LIGHTER Application filed Jl'uly 8,

The invention relates to a process of and an apparatus for the continuous conversion, distillation, rectification and refining of heavy oil hydrocarbons derived from crude 5 petroleum, or other complex mixtures of heavy hydrocarbon oils derived from the dry distillation of bituminous coal, shale, etc.. into lighter oil hydrocarbons of greater volatility. whereby the lighter constituents thus produced by cracking and synthesis may be obtained immediately in a pure commercial quality without intermediate prodnets and without further application of heat, condensation and redistillation.

The invention further relates to a process of continuous fractional distillation of the lighter volatile constituents inherent in the crude oil or other similar complex mixtures of hydrocarbons, and at the same time carry- 2o ing on the continuous conversion through cracking and synthesis of the residual complex mixtures of heavy or high boiling hydrocarbons into low boiling. highly volatile hydrocarbons, and recoverim the same in the same cycle of continuous dls'tillation and rectification as the volatile constituents inherent in the crude oil. without cooling these heavy hydrocarbons for the said conversion and subsequent fractional distillation and condensation of the lighter constituents.

lhe invention further relates to the apparatus and appurtenances whereby said process may be efficiently carried out.

Other objects of said invention will appear from the description hereinafter and the features of novelty will be pointed out in the appended claims.

lln order to convey the underlying principles of this conversion process and show its basic features of novelty. the applicant may be allowed to dwell for some time on the conversion principles applied in the various cracking processes now in commercial use. which are termed the liquid phase crackinn processes.

lln all these liquid phase conversion processes the conversion of heavy oil hydrocarbons into lighter hydrocarbons is brought about through application of heat under high to pressure in order to force the molecular bonds PRUD'UCTS 1924:. Serial No. 7%,865.

of the complex molecular structures of the heavy oil hydrocarbons asunder, and then to provide the means for molecular readjustment and synthesis of these molecular fragments to constitute and form the desirable lighter oil hydrocarbons of simpler molecular structure.

If we investigate how the molecular agitation up to its final instability and rupture of the bonds through application of heat and pressure is brought about in all of these processes of liquid phase cracking, We find that the heat is applied to the oil in bulk form, either in shell type or tubular stills with an oil content ranging from barrels up to several hundred barrels, and that the heating of the oil for distillation and cracking is done in one stage only, in the most intense and violent form. never reaching the oil uniformly because of the fact that oil is a bad heat conductor, and that only a part of the oil closest to the heating surface is subject to the most violent molecular agitation and final disruption, whereas the inner core of the oil in a heating tube or in a still is not affected at all.

llf we stop to think further that the final rupture of the molecular bonds of any organic chemical individual is accompanied by the evolution of heat, which is termed as exothermic heat, that is, the liberated heat of molecular agitation, then we understand why the final rupture of the molecular structure of the oil so treated happened under a form, which might be termed as a molecular explosion or in the laymans language as overcracking of the oil so treated.

llhe attendant signs of explosive cracking and overcracking of oil are undue precipitation of carbon in form of coke, an undue amount of fixed or permanent gas with great amounts of free hydrogen. the smallest fragments of the disruptured molecular structure. and for this reason a great percentage of unsaturated lighter oil hydrocarbons will result from this mode of cracking. If we reflect further that all unsaturated oil hydrocarbons with unsatisfied open bonds for hydrogen are the best carriers of sulphur and nitrogen contaminations, more tlti Bill

or less present in all oils, then we understand the obnoxious odor of such cracked spirits with its attendant difiiculties of refining with chemicals, high refining losses and high costs of operation to obtain a serviceable, waterwhite and sweet motor gasoline.

If we reflect further that by far the greatest amount of heat has to be transferred to the oil in order to bring about the desired molecular instability of the oil to be cracked, then we understand that the heat of cracking the oil, that is to bring the oil hydrocarbon structure to the point of cleavage, is comparatively very small and from this fact the importance may be inferred of a uniform and gradual approach from the temperature of molecular instability to the temperature of cleavage or partial cracking of the molecular structure of the oil hydrocarbons.

The reason for this gradual approach has its explanation in the evolution of exothermic heat, when the cleavage in the molecular structure of the oil hydrocarbons sets in, because it is this exothermic heat which fictsI like the proverbial straw on the camels It is this released heat, added to the external heat from the furnace, which sets off the rupture of the molecular structure of the oil hydrocarbons in an explosive form with the attendant result of high carbon preci itation, high amount of fixed gases and hig unsaturation of the remnant lighter oil hydrocarbons, which we had set out to produce in a saturated form. The more the complex molecular structure of the heavy hydrocarbon oil has been shattered in fragments through the explosive rupture of the molecule, the higher will be the liberation of exothermic heat and the spontaneity of this heat will of course affect the mode and conduct of conversion beyond the control of the most sensitive recording thermometer in use.

From this reflection we come to the logical conclusion that the conversion of heavy oil hydrocarbons to lighter ones, with minimum amount of carbon and fixed gas generation and maximum amount of yield in saturated oil hydrocarbons of simpler molecular struc ture, can only be effected through the control of the manifestation of the exothermic many gas plants, the exothermic heat with its spontaneity of action, is the best ally to accomplish this end. Wherever selective cracking with ,a certain end and final product inv mind is intended, the control of the exothermic heat is of vital importance, a fact, which up to this day, was lost sight of by the inventors of cracking processes now in commercial use.

All inventors of these processes now in commercial use, have tried to counteract the influence of exothermic heat through the application of high pressure,'up to 500 and even 1000 pounds per square inch, in order to pre vent the destructive or explosive rupture of the molecular structure.

It can not be denied that high pressure ameliorated these conditions to some extent without eliminating them altogether, but in the wake of these high pressures, we find high cost of installation, great wear and tear of the equipment, high operation costs, and disastrous accidents.

That the influence of exothermic heat was not taken into consideration by most of the designers of such processes has its reason in the fact that its manifestation is hardly apparent in the small quantities of oil treated in such processes due to the lack of mass reaction. Nevertheless to the trained observer and experimenter its influence is apparent even in the absence of mass react-ion.

In order to explain fully the principles involved in the applicants process of cracking heavy oil hydrocarbons and to point out the distinguishing points of novelty, the applicant may now be allowed to follow the course of the flow of oil through a cracking coil, as these. coils are most frequently used in the present day commercial cracking processes, and be allowed to point out, what will actually happen when the oil is so treated.

The coils in question are continuous series of tubes through which the heavy oil fraction to be cracked is pumped in a continuous stream and in counter current flow to the hot fire gases. The first part of these coils, which is the largest part of the entire coil, serves the purpose to heat the heavy oil fraction in a continuous flow and counter current to the fire gases, to the temperature of molecular instability, determined through the pressure of the cracking operation under which an excess amount of heat can be transferred to the oil without evaporation or change in the molecular constitution of'the particular fractions or constituents of oil to be cracked. These heating ducts of the oil will always stay clean, that is, no carbon incrustation takes place in this part of the coil, due to the absence of any cracking of the oil or chemicalchange of same.

The second part of these coils, which is the smallest part of the entire coil, serves the purpose to heat the oil in a continuous flow attice and counter current to the hottest gases of the furnace above the point of molecular instability, and therefore to the temperature of cracking or partial dismemberment of the molecular structure of those oil constituents of the heavy oil fraction (complex) to be affected and changed chemically into oil constituents of less complex structure, that is in oil hydrocarbons of higher volatility. 'llhese heating ducts of the oil, performing the Work of cracking through an additional supply of heat to the oil over the limit of molecular instability, show an increasing carbon incrustation in the direction of the flow of oil, and proportional with the intensity and influx of heat.

On account of the low heat conductivity of the carbon scale, no further and adequate. heat transmission to the oil is possible, and

would become exceedingly uneconomical and dangerous if carried beyond a certain point.

At the maximum thickness of the scale of carbon of the operation of the cracking plant has to be interrupted and the coils to be subjected to drill-cleaning for the removal of carbon. This occurs about after three days of operation.

Due to the fact that the carbon so precipitated forms with the iron of the heating ducts a ferro-carbide atthese temperatures which deprives the iron or steel of its tensile strength because of its brittleness, it is apparent that the life of operation of this coil is very limited, and that the cost of operation through upkeep must be very high.

llf cracking of heavy oils is considered in pressure stills of from 100 to 200 barrels capacity and over, the precipitation of carbon in these stills is even more pronounced than in coils, as the oil to be heated is stagnant and highly overheated along the still shell, despite the provision of mechanical scrapers to keep the carbon from burning fast to the bottomplates of the still.

Two pertinent questions may therefore be asked:

(1) ll hat are the reasons for the precipitation of carbon through cracking of oil in the form of a hard, flinty coke in the cracking ducts? (2) ][s a coil, or a shell still, or a tubular still the proper mechanism to carry out cracking of oils along lines of physical and chemical laws governing the conversion of high boiling oils into motor spirits of low volatility by partial destructive distillation? Following the flow of oil through the pipe coil, We observe that the velocity of the oil in the core or center of the pipe is maximum, and minimum along the pipe walls and that the velocities between the two extremes are following the stream line law which is a straight line connecting the maximum and minimum values of these velocities.

From this it will appear that the oil film moving with minimum velocity along the pipe Walls will be exposed to the influx of heat from the fire gases from two to three times longer than the core of the oil in the center of the pipe cross-section, as the difference in the velocities is approximately two to three on an average, depending of course on the 'size of pipe.

When the oil film'along the pipe walls has already attained the temperature of molecular instability and subsequent cracking, the body of the oil in the center will not have been affected to that extent and all intermediate films between these two extremes will all have been subject to ditl'erent temperature stresses in accordance with the difference of velocities of these films, that is, their time factor of the exposure of the oil film to heat, and their difference of heat conductivity from oil film to oil film.

llt can safely be said that not more than one third of the oilpumped through the coil for conversion purposes was subjected to actual cracking conditions, as can be observed in actual practice, and that out of this third of oil so allected, one third was subjected to conditions of over-cracking, that is, secondary and tertiary cracking, of the products of the first or primary cracking.

Because, from the explanation of the influence of exothermic heat upon the course of cracking heavy oil hydrocarbons, we know that the addition of any outside heat to the heat evolved by molecular dissociation, termed exothermic heat, will cause 0Vercracking through explosive impulses, shattering the molecular structure partly to such small fragments, which will synthetically not constitute light hydrocarbons of the desired quality, because of their instability and unsaturation.

lVe observe further that their molecular synthetic reconstitution of desired products of low boiling hydrocarbons is rendered almost impossible, as these products of primary cracking are carried along with the flow of oil through the pipe coil exposed progressively to higher temperatures, withoutany escape from further pyrogenic dissociations, as these products are mostly in gas form or vapor form, which even under the highest working pressure, accumulate on the top of the pipe cross-section and are so carried through the hottest zones of the cracking coil, until discharged into a comparatively cool reaction chamber, where equilibrium adjustments are supposed to take place between the products of dissociation in vapor and liquid phase, and the carbon is supposed to drop out of suspension from the oil.

It is obvious from this observation that the rendition of the precipitated flaky carbon into hard flinty coke, has its cause in the progressive pyrogenic dissociation of the pri mary products of cracking, and that the deposition of this coke on the heating ducts of the cracking coil has to increase with the increase of heat of the oil passing through ever increasing hotter zones of the furnace, with ever increasing pyrogenic decomposition of the increasing amounts of primary, second ary, etc., products of crackin When the. oil enters the cracking zone 0 the coil, it is on the limit of molecular instability, and as it passes along the coil towards progressively increasing hotter zones, the various constituents of the heavy complex oil fraction of course will be partially broken up, and as there is no escape for the already cracked constituents, they will be subject to further pyrogenic dissociation, beyond control of the operator and the result will be that an undue amount offixed gas Will be produced with a concomitant increased precipitation of carbon, which originally being in a flaky form, like graphite, will bake fast on the superheated heating surface of the coil, and only a part of the carbon will be kept in suspension, which through the action of convection of the flowing oil finds its way to the higher velocity oil in the core of the pipe, and this will be flushed out of the cracking coil into the reaction chamber where then the converted products of cracking are either distilled off for recovery, or are left in the so-called synthetic crude for further treatment.

From the analysis of these facts we come therefore to the logical answers of our previous questions, that :7

(1) The reasons for the increasing precipitation of carbon in form of coke in the cracking ducts of the pipe coil are secondary pyrogenic dissociations of the products already cracked and carried along in these duets without any provision for. escape, etc.

(2) That a pipe coil, or tubular still or shell type still is not a mechanism which can properly carry out the work of converting heavy oil hydrocarbons into lighter or lower volatile oil hydrocarbons, according to the requirements of the physico-chemlcal laws, governing such a conversion. through well ap lied thermal molecular stresses, because oi the fact that neither the liberated exothermic heat, nor the external applied heat to the cracking coil, can be regulated or be controlled by the operator in order to comply with the requirements of the laws involved.

The disadvantages pointed out for the pipe coil as a means ofconversion of heavier hydrocarbon oils into light or low boiling hydrocarbons, pertainvalso to all stills, no matter of what special design to alleviate certain shortcomings, as long as these stills are treating heavy oils in bulk form, without any discrimination to the fact that even the closets cut or fraction of heavy oils, as kerosene, or gasoil, or waxdistillate, or fuel oil, or any other cut derived through fractional distillation of crude petroleum or other comlex mixtures of hydrocarbons, are complex 1n themselves, that is, that they contain a' series of hydrocarbons with entirely different physical and chemical constants, which have to be dealt with individually in anjy successful industrial converter (cracking) in order to obtain:

(1) A proper conversion factor, commensurate with cost of operation in one continuous Working cycle with minimum expediture in fuel, and'wear and tear on the equipment, etc.

(2) Minimum precipitation of carbon through prevention of secondary pyrogenic dissociations, and in such form that it will stay in suspension with the oil without imparing the transmission of heat through the distillation or heating ducts, that is, that the carbon should be precipitated in a graphite like form, or lamp black form, which by its light weight floats in and on the oil under treatment.

(3) Minimum evolution of fixed gases through the avoidance of secondary or tertiary pyrogenic dissociations and scorching of cracked oil vapors and providing of means that these gases may reenter molecular readjustment with the cracked oil hydrocarbon vapors in a stage of interatomic instability for the preservation of the hydrogen content of these gases for the saturation of the cracked oil hydrocarbon vapors.

4a) That the products of conversion may be obtained in a saturated state of such commercial purity that they will not be subject to further chemical treatment and redistillation outside of those carried on in the vapor phase cycle of refining and rectification or ractional distillation.

In order to inform ourselves in regard to 'the influence of the heterogeneity of the oil to be cracked in the course of cracking and the results obtained, we learn from all present day commercial cracking processes, and without exception, that the conversion factor is highest in all cases where the complexity, or heterogeneity of the oil is minimum; that the carbon precipitation and evolution of fixed gases is minimum, and that the saturation of the converted low boiling hydrocarbons is maximum, that the fuel consumption, wear and tear on the equipment and cost of operation is a concomitant minimum; and vice versa, where the oil to be cracked increases in its complexity, that is, when the number of heterogeneous hydrocarbons present in this oil increases.

In other words, the closer the fractional cut of heavy oil within narrow limits of temperatures, the smaller the amount of different oil hydrocarbons will be present whose physical and chemical constants are less divergent, and will therefore find in the present day cracking processes conditions more till mate

favorable for synthetic conversion, as with cuts or fractions which are made within a wide range of temperatures, and comprise therefore a greater variety of oil hydrocarbons with a greater divergence of physical and chemical constants which can not be met by the applied temperature and pressure conditions of the present day cracking processes.

lt appears therefore as evident that only those heavy oil hydrocarbons whose physical and chemical constants fall within the range of the applied thermal stresses, defined through the pressure and temperature range, will be subject to constructive cracking with minimum amount of carbon and fixed gas production, provided that the products of cracking were removed from the cracking ducts as quickly as they are produced, without incurring any additional secondary pyrogenic dissociation; whereas all heavy oil hydrocarbons whose constants are outside of. the range oilthermal stresses will escape any chemical or physical change and will constitute a dead load in the cracking cycle, consuming unnecessary fuel, water, and wear and tear of the equipment without undergoing any change in its molecular constitution.

To illustrate our point of contention, a table is presented with all physical constants tor the limit of parafine hydrocarbons, which are the best known of all the great complexes oil oil hydrocarbons.

In this tabulation is shown. the molecular weight, specific gravity, boiling points at at mospheric pressure, temperatures of molecular instability, pressure in pounds per square inch at temperature of molecular instability, compiled b various authors, as Engler and Hoeter, Beilstein, Redwood, etc.

Temperature of molecular instability is the degree of heat at which the bonds of intermolecular attraction between the relative atomic constituents are stressed to a point of inequilibrium. And this temperature may be called the critical temperature at which the intermolecular bonds yield at the slightest additional influx of heat, and the intermolecular heat is liberated when these bonds are giving away under additional stresses of heat or equivalent mechanical stresses, as impact, shock, etc., with an equivalent generation of heat. 'lhe liberated intermolecular heat is the heat we have termed as exothermic heat, which in its sudden or gradual release forms an important part in the outcome of constructive cracking of heavy oil.

It the thermal stress is brought about too suddenly, there will be a sudden concomitant release of intermolecular or exothen mic heat, and a violent explosive crumbling oi the molecular structure occurs with resultant products of over-cracking (fixed gas and carbon) etc. With the thermal stresses brought about uniformly and gradually, the release of intermolecular heat will be gradual at the yielding point of the bonds, and the resultant products of cracking will conform with laws of conservation oil hydrogen and carbon, that is, minimum evolution of fixed gas, minimum precipitation of carbon with maximum yield in saturated hydrocarbons by subsequent molecular readjustments.

Creative? Temp. 0! pressure Boiling temp. of i l. Name of hydrocarbon and hue. out Chemical symbol giggly gg s g; points, fl g molec. or. F. de instability,

, lbs. per

sq. m.

1' oh drocarhous: light-ll one" 72 0.6355 96.8 765 5820 001114-- 86 0. 6494 157 732 3180 Heptane C7Fl'm 100 0. 6619 209 715 1765 ()r'tm'm 03H" 114 0. 6740 258 695 1065 Nnna'na C Hm 1% 0. 6838 302 080 590 Decane 1-- Cmfiw 142 0.6943 342 662 320 Unrlmann C E-n 153 0. 6939 381 643 216 Kerosene hydrocarbons:

Bed 9 C H 170 0.7025 418 0% m0 Tsw clluil 1 4 12g 23% a2 Tetradecane Oilfie- 1 B Pentadecane C15H 212 0.7252 518 545 Hexadecane C H 226 0.7319 549 515 G 111 drocarbons: v

jgl nptlir one 240 0.7369 573 he Outsider-sane CmHm 2375 d e i can, gigging?! O-mFLw 282 0. 7507 662 437 M l 0 B 295 0.7534 088 E19 h drocarbons: ldlihoshne CnHM 310 0. 7553 714 404 Tl OzaHux 3% 0. 7571 739" 391 Tetr C'MHM 338 0.7583 763 383 Pentacosane 0251151 352 0.7597- 788 375 Harem-sane 020B 366 0. 7687 814* 368 Heptficosanfi 8 232 g; 0 sane Ni clin 40a 0. 7797 880' are 1 t Determined under vacuum and calculated to atmospheric pressure.

limit In the above table, the hydrocarbons of the parafiin or limit series, were tabulated under the ent day refineries, disregarding further subclassifications of these products for the sake of simplicity as to the question of rational cracking under discussion.

The hydrocarbons tabulated under classification of fractional cut gasoline are those of reatest commercial value and are desired as nal products from the processes of cracking heavy or complex oil hydrocarbons, as are tabulated under the commercial cuts of erosene, gasoil and fuel oil or its subdivisions. v

. The purpose of commercial cracking processes is to convert all heavy oilfractions, as kerosene. gasoil, fuel oil, etc., into oil hydro- .carbons belonging to the gasoline series, in

case no ready market should be obtained for these products.

From the table we see that each hydrocarbon compound occurrent in petroleum has its own distinctive and characteristic constants, which pertain not only to differentiations in specific gravities, boiling points, hydrogen content and molecular weights, but also to the temperatures required to bring about the instability of the molecular struc tures and the pressure required'to raise the temperatures of the oil hydrocarbons in liqufi hase to the temperature of molecular insta ility.

In present day cracking processes, through application of heat and pressure usually far in excessof the requirements, molecular instability is throughout carried to the point of molecular dismemberment by which the bonds of the atomic constituents are forced asunder, which procedure is by no means necessary to effective cracking for the following reason:

When through application of heat the interatomic agitation of the molecule is carried to the point of instability, the oil hydrocarbons thus conditioned and prepared enter readily, either in vapor or liquid phase, into combination for molecular readjustment with other elements, as free hydrogen gas or hydrogen carrying radicals, such as CH C l-I etc., which were either produced through cracking of the more unstable oil hydrocarbons at temperatures far below their atmospheric boiling points or were introduced in the cracking ducts from an outside source.

Through the incorporation of free hydrogen gas or hydrogen carrying radicals into oil hydrocarbons in the state of molecular instability, the nature of this oil hydrocarbon may be changed without undergoing dismemberment of its constituents, as hydrogen incorporation in a free state or in a radical form will increase the hydrogen content of the hydrocarbon, reduce its specific gravity and lower its boiling point to that degree, falling within the limits of the oil hydrocarbons of tlge gasoline series as shown in the table a ove.

technical parlance of todays cracking processes is, that pronounced molecular dismemberment is in progress in a heated oilmass with the following concomitant products of the cracking process:

(1) Rare or fixed gas, containing free hydrogen as methane, ethane, propane, etc., and olefines as ethylene, propylene, butylene, etc., with traces of carbon dioxide and monoxide, 'etc.

(2) Precipitated carbon in form of coke, granulated hard, or in amorphous flaky and powder form. v

(3) Lighter lower boiling hydrocarbons of the gasoline series.

(4) -Lower specific gravity residuum oil, carrying part ofthe precipitated flaky carbon.

Cracking with the .above mentioned resulting products is carried out under uncontrolled thermal stresses with concomitant over rarification or over-cracking, where the conservation of hydrogen for purposes of molecular readjustments can not be effected, therefore losses will result in this mode of cracking in an undue production of fixed gases and precipitation of carbon, affecting not only the volume of yield in desired light hydrocarbons, but also its quality in regard to color, stability, odor and saturation.

When cracking is carried out as in this case, non-equilibrium conditions are existent and progress during the whole course of cracking, with resultant over-rarification, so that at the end of the cracking operations, when the treated hot oil mass is discharged into a relatively cooler chamber for equilibrium reaction and adjustment between the products of cracking under non-equilibrium conditions, these products will be unable to enter efiectively into readjustive equilibrium conditions, due first to over-rarification of the cracked products, and second due to lack and intimacy of contact. Due to these conditions, undue amounts of fixed gas will leave the system, unable to reenter into combination with the other products of cracking. Undue amounts of carbon will be precipitated, due to the over-rarification of the hydrogen carrying gases and undue unsaturation of the cracked lighter hydrocarbon vapors will result because of the migration of free hydrogen and hydrogen containing gases, I which reached under non-equilibrium conditions such a state of rarification that it could not recombine with the unsaturates of the cracked gasoline hydrocarbons.

The process submitted and later on explained contemplates the change of heavy hy- The meaning of the word cracking in the I mares drocarbon oils into light hydrocarbon oils of the gasoline series through a combination of cracking of these heavy oils of least thermal pressure stability andconstructive synthesis through hydrogenization of those heavy hydrocarbon oils of highest thermal pressure stability by bringing these oil hydrocarbons to such a degree of interatomic thermal agitation that the assimilation of free hydrogen or hydrogen carrying gases, as natural gas,

casing head gas, etc., can be effected, lowering thus through the incorporation of hydrogen the boiling points of these heavy oils and changing their molecular constitution at the point of molecular instability as described in the Letters Patent No. 1,490,055. as reaction taking place in the reaction tower.

This is the reason of intersecting in the path of gases and vapors, produced through cracking, fields of molecular instability in vapor phase and liquid phase to ett'ect absorption of gases and molecular readjust-merits.

The meaning of the word cracking is, in the sense of this submitted process, that pronounced molecular dismembermentwill be carried out only in a part of the heated oil mass of those heavy oil hydrocarbons of the most unstable form, whereas the more stable heavy hydrocarbons will be changed. into lower boilers by bringing them to the point of molecular instability only, and incorporate in this state free hydrogen or hydrogen carrying gases produced through cracking of the first named series of heavy oil hydrocarbons or introduced from outside sources, or both, with the results, that:

(1) Only limited amounts of rare or fixed gases will remain, leaving the cracking system and be reintroduced in cycle for further assimilation. thus preserving the given hydrogen supply for the manufacture of saturated gasoline hydrocarbons produced by cracking. and use of this fixed gas as a means to agitate and crack the residual oil with lIllparted snperheat.

(2) The precipitation of carbon will be reduced to a minimum, and through its resultant flaky form be carried in suspension by the residue oil and thus carriedoutside the cracking ducts.

(3) The synthetic gasoline hydrocarbons produced will be stable, saturated and sweet.

Cracking as carried out with this process is proceeding under continuous equilibrium conditions between liquid and vapor phase products, due to the principle of fractional classification and concomitant selective fractional cracking, where balanced conditions are at any time existing between the vapor and liquid phase products of fractional distillation and fractional cracking, as well as between the liquid phase and vapor phase products of the concomitant products of molecular readjustment or synthesis. Oven rarification to any considerable extent is impossible, therefore optimum conditions prevail for subsequent readjustment and synthesis far below pressures and temperatures used in the present practice of cracking.

Having outlined the general comparative principles of cracking of the new process, the

equipment shall now be described with which the indicated principles of the process will be carried outin practice.

Fig. 1 is a sectional elevation of the converter O in which the cracking of heavy oils into light oils is carried out. F Fig. 2 is a cross-section on plane AA of Fig. 3 is a sectional elevation of a modified form of converter.

Fig. 4c is a sectional elevation of still another modified form ofconverter.

Fig. 5 is a diagram showing the entire plant.

Fig. 6 is a diagram of a homothermic regulating device.

Fig. 7 shows a detail, on a larger scale, of the heating element of the converter C.

Fig. 8 shows a detail, on a larger scale, of the heating element of the converter shown in Fig. 3.

Fig. 9 is a section on plane B--B' of Fig. 11.

Fig. 10 is a section on plane O-O' of Fig. 11.

Fig. 11 is a detail View of an impact separator.

Fig. 12 is a vertical section of top of the converter; and

Fig. 13 is a horizontal section of Fig. 12 on plane EFl.

Describing the converter in Fig. 1 and Fig. 2, 1 represents a conical or cylindrical the "It" at the steel shell. bolted or riveted on top to cover 2 with vapor outlet 9 and drip or film-apron 10 for the distribution of the oil over the filming trays, 1 1 to 1 of heater element 12. On the bottom the shell 1 is joined to a cast steel pan 3 as residuum oil receiver. 5 is a manhole access to the residuum pan. Connection 1 is for the extraction of the residuum oil from the pan to the carbon separator CS, Fig. 5. 4 is a pipe connection for superheated steam, superheated residuum, fixed gas, etc.. to beneath the distributor 6. cast to the shell of the residuum pan 3. which gases and steam will set the residuum oil in distributor 6 in a rotary motion, on account of pipe connection 4 being set on a tangent With distributor 6, and Said oil and steam and gas will escape distributor 6 through circular slot 7 in a rotary motion and subject also the residuum oil outside of distributor 6 to a rotary motion before entering vapor space of converter O and then follow upwards,

.the conical or cylindrical heating element 12 of the converter C being a casting of a noncorrosive and heat resisting metal.

To the conical shell of 12 are cast circular ribs or flanges 13. Fig. 7, at certain distances along the full height of the shell. To the flanges 13 are bolted the conical trays 16, preferably of the same metal as the heating element 12, or of copper, which as a good heat conductor will contribute greatly to the quick heat conductance from the directly heated shell 12 to the metal baths 17 in each tray, and to the oil films following flow arrows 1' 1, Fig. land Fig. 7.

The top parts of the conical trays 16 are cylindrical and are intended to form seals of oil (18) when same is flowing downward over these trays in the course of operation. That part of the trays lying between the tray Walls 16 and the wall of heating shell 12 is filled with low temperature fusing metals 17, which can be lead and alloys of lead, tin, zinc, ctc., according to the requirements. It is also understood that these annular spaces 17 tical ribs 15 (Fig. 8).

intended for metal baths of low fusing points, may be filled with the oil under treatment for conversion, or that these trays may be operated partly with metal bath and partly with oil under operation. Oils to be converted with high carbon content will require heating elements provided with metal bath throughout, whereas oils of low carbon content may only require metal bath in the lower cracking trays of the heating element, or none at all.

The heating element 12 is provided on the fire exposed side with horizontal circular ribs 14 and 14 which may be reinforced by ver- Th'ese ribs serve a double purpose, first to increase the heating surface of the heating element, and to establish uniform distribution of the heat in conformity with the time factor, second to have maximum resistance with the minimum amount of metal to withstand the compression or crushing stresses to which this heating element will be subjected when the converter'is subject to internal pressure.

The advantage of having the heating element of the converter 0 under the influence of compressional stresses is obvious, as the resistance of any'metal under compressional stresses and under the influence of high temperature surpasses the resistance-of the metal under tensional stresses and high temperature from two to three times.

\Vhich means that the walls of this heating element under crushing pressure and high temperature will at least be half as thick as if these walls would be subject to bursting stresses and high temperature.

As furthermore the transference of heat through a metal wall is proportional to the will have a higher operating capacity than one with a thick wall; that the intensity of the heat in the first instance can be lower in order to transfer the same amount of heat,

that therefore the wear and tear on the heating element and the setting of the converter will be in proportion less than when the heating elements are under tensional stresses and high temperature, which require thick walls to safely withstand the pressure The advantages in the design of this cracking converter under external pressure, instead of under internal pressure, are therefore vital under the point of view of cost of installment, cost of operation, safety of operation and economy, if compared with the 1 equipment used in present day cracking pro- 'cesses, carried out under high pressure and high temperatures, where the stresses are tensional, as the pressure acts internally.

The setting of this converter for the efficient application of heatis exceedingly simple. The annular concrete wall 19 serves as support of the converter C and as outside wall for the furnace proper. 20 are the outside walls of a Dutch oven which is installed at a tangent to the center line of the annular space between cylindrical bafHe 23 and refractory fire lining 22, Fig. 2, or eccentric to the center line of the converter C to the amount of a: as indicated in Fig. 2.

31 is a combined fuel oil and gas burner, 30 a refractory checkerwork to assure perfect combustion of the fuel in the Dutch oven. 22 is a refractory firebrick lining, protecting the outside concrete wall 19 and the inside of residuum oil pan 3, as this pan is not to be exposed to any heat. Between refractory lining 22 and concrete wall 19 an annular air space 24 is provided which is in communicaalong the annular space 24 where it will be heated through the contact with the hot refractory lining 22 of the setting and enter the combustion chamber through slots 25 in a preheated condition and so contribute to a complete combustion of the fuel with a high combustion temperature and prevent heat losses of the setting through radiation, as this heat will be carried away by the combustion air. This cooling effect of the air on the refractory lining 22 has also the advantage of increasing the life of this refractory lining,

Ill

which otherwise might attain the temperature of fusion, if no cooling were effected.

In the center of the converter setting is the waste gasidowntake flue 23 of a monolithic design and of refractory material,

with annular slots 26 and 27 for the circulation of cool combustion air, which is drawnv through these slots down through a channel leading to the side wall of flue 29 following arrow 1', leading then to slot 26 of the downtake flue 23, rising up in that slot, Fig. 2, where an annular connection with the slot 27 is established, where the air is led downward and back to the channeled side wall of flue 29, Fig.2, following arrow 7 and .finally leading up from the slotted side wall to the annular air space 24 to join the air from air intake 21 to the combustion chamber of the Dutch oven. Through this cooling of the lower part of downtakeflue 23, its wear and tear through the high temperature in the setting will be minimum, and a highly preheated air for the combustion thus procured.

For a prolonged and intimate contact between the fire gases of combustion and the heating element of the converter, use is made of the kinetic force of the'fuel oil and gas burner, subjecting the products of combustion to a rotary motion in the'direction of arrow 1", by arranging the Dutch oven on a tangent with the converter setting, so that an annular space is created through the arrangement of the circular bafile flue 23 in the center of the converter'setting, along which annular space the rotary motion can take place. Under the influence of the stack draft in a vertical direction the horizontal rotary motion of the fire gases willbe changed to a spiral rotary motion in the direction of arrows r", sweeping in the annular space between the setting and downtake flue 23 upwards, and being always in intimate and prolonged contact with the heating element 12, as the fire gases rise further into the interior of the converter thus establishing along the passage of the gases along the heating element, conditions of continuous and uniform heat transfer to the heating element under finely graduated conditions, establishing from tray to tray upwards fine differentia tions of temperature, which are essential for the operation of the converter to bring about gradually increasing thermal stresses on the oil to be converted.

When the gases have reached their topmost position and have considerably cooled off through transfer of. heat, they will now follow downward in the direction of arrows '1 inside downtake flue 23 and will finally leave the setting of the converter through flue 29,

leading to the preheater of pipe still P. St., Fig. 5, where the residual inherent heat of the gases will be transferred to the oil preheatin coil 33, and then leave through stack t. the pipe still setting.

From the principle of application of heat to the converter it is apparent that no heat losses through radiation can occur because the heat is applied in the interior of heating element 12 and the heat carried by the gases of combustion is bound to be transferred to the heatin element and to the oil to be treated. The e ciency of the setting and concomitant fuel economy must therefore be high.

The lea-fie flue 23 installed in the center of the furnace and extending into the interior of the converter will act as a heat storing device, which radiates heat centrally and uniformly to the heating element of the converter and will so equalize any fluctuation in the generation of heat in the furnace.

The relatively cooler gases passing out of the setting through the interior of downtheir cooling effect on the flue walls and the hot surrounding combustion gases, will exert a stabilizing and equalizing efl'ect, similar to the eflect of a flywheel on an'engine where the flow and generation of power is intermittent. v

This feature is important for the performance of work of the converter. The heat imparted to the waste gases from flue 23 of course will be utilized, as already shown, inthe oil preheater of pipe still P. St. before these gases escape through stack St.

Converter shell 1 and cover 2 are protected against heat radiation by means of insulation 11, which establishes uniform heat conditions in the interior of converter 0.

The operation of this converter is carried out as follows:

The converter is prepared for operation by applying fire to the settin and to bring the metal baths in the series of trays on the heating element close to the fusing point, injecting during this period steam through 4' in the converter, which will be subjected to a 1'0- tary'motion asalready mentioned, and displace all air from the converter in order to prevent oxidation of the metal bath when brought to their fusing points.

Those heavy oil fractions which it is decided upon to be converted into gasoline hydrocarbons are refluxed from the various units of fractional extraction in a hot state to the reaction towers R T and RoTo from whence these fractions find their way through line 62 and 9", Fig. 5, as will be explained later on, to the distributing head T D, Fig. 12, where they will flow into an annular seal 9, Fig. 12, from where they will overflow around cylindrical edge 10 in film form downwards through vapor neck 9 and be distributed through circular drip apron 10 in the top pan or tray 1, Fig. 1. Here the oil will spread out over the metal bath, form a seal and finally will overflow the rim of the pan and spread out in film form over the whole circumference of the pan as indicated by arrow 1' Fig. 7 and Fig. 8. The oil film will then reach the annular surface of the metal bath of the direction of arrow 1", form again a seal on this pan and overflow again over the rim of the second pan in still finer film form, due to the rogressive increase of the circumference o the following trays, always subjected to increasing temperatures as the oil gravitates downward. The down flowing oil film will be subjected to expansion and contraction as it flows outward from the heating element toward the rim of the pans, or back to the shell of the heating element 12 along the outside surface of the conical pan, thus causing through this expansion and contraction a continuous variation in the thickness of the oil film which is essential for the ap- 'plication of progressive thermal stresses to the oil film in an almost molecular form.

As the expanding and contracting oil film glides down over the ever increasing annular and conical outside surfaces of the trays 1, the film is spread out over ever increasing surfaces, as it penetrates deeper and deeper in the converter with ever increasing temperatures, because the oil film is flowing counter current to the fire gases from the furnace. The time of exposure to the thermal stresses is therefore progressively increasing from pan to pan with a concomitant ever increasing fineness of the oil film. This is a vital element in the operation of the process, viz, that the time factor for the conversion should progiressively increase from cracking level to crac ing level, that is from pan to pan, and that the oilfilm under conversion treatment should be progressively thinned out in ever increasing finer films, as it is gliding down over the cracking pans in order to insure almost molecular treatment in the progressive increase of the thermal stresses and because of the increase of cracking resistance of the oil film when subjected to previous partial cracking, needing therefore increase of time factor and intimacy of contact through thinning out the oil film.

The oil gliding over the heating element will of course be subject to fractional distillation and therefore fractional classification, so that eachseal in the pans will contain specific hydrocarbons from the hetero-- supplied with any cooling media, until the whole system has built up that required pressure which the heavy oil under treatment needs in order to apply the necessary thermal stresses to the oil in the liquid phase and conjointly also in vapor phase.

The pressure required to be built up by evaporation can easily be determined by a previous boil-over test in the laboratory, which will determine those heavy hydrocarbons demanding the highest pressure under which the temperature of molecular instability can be brought about.

Should the boiling point of the initial fraction of this heavy oil under cracking treatment lie between 400 and 460 F., it would mean that dodecanes and tridecanes or their homologues would be the lightest hydrocarbons under treatment. From the table we see that the temperatures of molecular instability for these two hydrocarbons are: 628 and 591 F., with requisite pressures to bring these temperatures about in liquid phase of 120 and 52 lbs. per square inch.

If therefore cracking of these hydrocarbons would be carried out only in liquid phase, aflpressure would have to be exerted of about 125 lbs. in order to raise the temperatures of the hydrocarbons to the points of severance of their molecular bonds.

Nb such. pressure however will be required to bring about this end in the light of my previous discussion on this subject; because my process to be described, converts those hydrocarbons into lower boiling li hter hydrocarbons first by molecular rea justment at the point of molecularinstability through incorporation of hydrogen by migration and second through cracking of same in liquid and vapor phase..

Cracking in vapor phase can be brought about almost independently of pressure, and as my process is working in liquid and vapor phase, only moderate pressures will be required to obtain the desired end.

The principle involved to bring about cracking of hydrocarbons in the vapor phase conjointly with cracking in liquid phase, is the well known principle or phenomenon of Leydenfrost. According to this phenomenon of Leydenfrost a fluid dropped on a heat ed surface is prevented from evaporating, no matter how hot this surface may be, pro- VidLd the generated vapor sphere, separating the liquid from the heating surface, is kept intact, after being established. If a drop of water is placed on a red hot iron plate, the water drop will stay indefinitely as water on the plate, if the steam envelope surrounding the water drop, is kept intact through elimi-r nation of any draft which might blow away said vapor sphere. This vapor envelope acts as a heat insulator between thevsource of heat and the water drop, absorbing all heat from the hot plate until that vapor is highly superheated, even-to the point of molecular disassociation, despite the fact that this sphere of water vapor is in contact with liquid water.

This sphere of vapor exerts a considerable adhesive force to the water drop proper and a can only be removed by" blowing against it quite hard;

., viscosities than water.

evaporation of the oil As soon as this insulating sphere of water vapor is removed and the heat of the plate can penetrate the water drop, spontaneous evaporation of the water will take place.

This henomenon applies even to a more remarka le degree to liquids with higher The adhesive force of the vapor sphere ofviscous liquids,.like heavy oils, etc., is even more pronounced than by water, so that considerable elfort has to be made to blow such vapor spheres away from the liquids they envelop or enwrap.

It is this principle which'is made use of to accomplish my above mentioned end to crack andconvert heavy hydrocarbon oils,

which would require high temperature-pressure stresses in orderto crack the same in the liquid phase, to perform this cracking at low pressures or no pressure at all.

When the oil film passes the surface of'the pan in the direction of arrow 0, Figs. 7 and 8, that is in a horizontal direction, the oil film will be separated from the superheated surface of the metal bath, by a layer of oil vapors, on which layer or cushion of vapor the oil film will float.

This cushion of vapors will absorb all heat transferred by. the heated surface of the metal bath, acting like an insulator between oil film and the heating surface, and be subjected to superheatin and no important 111 will take place beyond that of creating the vapor cushion on which the oil film floats, though no pressure commensurate with this superheat is exerted on the oil. Thus the vapor oil cushion is subjected to superheat as in a pure vapor phase cracking process, where no oil in liquid phase can be present in order to accompllsh dissociation of the oil hydrocarbons in vapor phase.

When the oil film, however, reaches the rim of the cracking pan, overboards the pan and films downwards over the conical surface of the pan, the upward rush of the gases and vapors andsteam in the direction of arrow 9, coming from the cracking pans below and the distributor 6, will exert a blowing eifect on the edge of the pan, disturbing slightly the oil film in the action of overboarding the rim of the pan and thus give the encompassed vapor cushion a chance for escape into the vapor space of the converter and also permits escape of the fixed gases produced by severance of the bonds of that particular oil hydrocarbon, subject to cracking in that particular selective cracking pan.

The oil film gliding down over the conical outside surface of the pan in the direction of arrowr Fig. 7 and heated by that surface by conductance of heat through the pan walls, will now be subject to thermal stresses in the liquid phase, because no separating vapor cushion could establish itself on that inclined heating surface of the conical pan. The stresses of heat brought about on the oil film during this passage over the outside surface of the pan will be in a mild form, as the heating isdone indirectly through conductance of heat through the pan walls.

l-Ve see therefore from the preceding description that'the oil film gliding downwards over the series of cracking pans of heater element 12 of the converter G will be subject to the following influences:

p 1. Fractional distillation and concomitant classification of the oil hydrocarbons in liquid phase, that is after balanced conditions of operation of converter are established; each cracking pan seal will contain certain closely related hydrocarbons, requiring certain and specific pressure-temperature conditions under which cracking will satisfactorily proceed.

2. Fractional cracking with concomitant fractional distillation and rearran ement and reclassification of the remains o hydrocarbon oils in liquid phase for new pressure and temperature conditions.

3. Fractional cracking in vapor phase of selective character while the oil films pass horizontally over metal bath seals 18.

4. Fractional cracking in liquid phase while oil 'film'isfpassing over the outside sur-' face of theconical cracking pans.

5. Intermediate states of molecular instability of oil hydrocarbons prior to approach of stages of cracking in which stages maximum susceptibility is obtained in changing the nature of an oil hydrocarbon through hydrogen incorporation, without resorting to cracking, and only fractional distillation taking place. These stages ofmolecular instability occurring in vapor phase during fractional distillation, and in liquid phase, while the oil films are gliding over the outside surfaces of the cracking pans. Molecular adjustments too take place in vapor phase of vapor space of converter while vapors and gases are passing towards vapor outlet 9, and

vapors and gases to establish equilibrium conditions.

between liquid and vapor phase oil hydrocarbons, increase of surface of vaporization and increase of heating surface, which is equivalent to a continuous increase of the time factor as the reactions of conversion slow down due to the approach of stabler molecular structures in the course of cracking these oil films with their rearrangements in the liquid phase. The stabler the oil hydrocarbons become under pressure-temperature stresses, the thinner becomes the oil film under treatment on its downward travel with a continuous increase of the reacting time factor.

From the above enumerated steps of operation can be seen that each oil hydrocarbon will be enabled to find and choose its own cracking level under conditions of uniformity and fineness of gradual approach through the amut of intermediate stages in which readmstments and rearrangements take place between the liquid and vapor phase products of cracking.

No over-cracking or-over-rarification can take place because of the immediate diffusion of the products of cracking or of molecular insta ility readjustments, into a relatively cooler vapor space, where the evolution of the exothermic heat will serve a constructive, instead of a destructive end.

It is further evident that no hydrocarbon of a complex heavy oil can escape itsconversion into light gasoline hydrocarbons by passing the converter, because of the great variety of means and their combinations, to bring about that end, provided'that the converter is provided with the necessary number of selective cracking levels (pans) commensurate with the complexity of the oil to be converted, that is, that the necessary graduations of temperatures are established, out of which each hydrocarbon may select the one most suited for its conversion, either in vapor phase or liquid phase or by readjustment in a suitable state of molecular instability, etc.

The process described can be carried out with a high conversion factor under atmospheric pressure, particularly where the conversion of the high boiling or heavy fractions of crude oil is intended, but the exertion of certain amount of pressure will always be beneficial as a regulating and counteracting agency against too violent reactions.

As the chemical and physical constants of oils change with the conditions of their occurrence and origin, changing even from well to well of the very same pool, being of paraffin base or asphalt base, or paraflin-asphalt base make-up, it is apparent that no cracking process can aflord to limit itself to certain can be used for this purpose.

preconceived and predetermined temperature and pressure conditions, which are supposed to hold true under all circumstances, no matter what the actual physical and chemical requirements of these oils might be.

If the cracking process is carried out under automatic selective principles, with the provision that each specific hydrocarbon of the oil can select its own conditions under which it might beconverted into a hydrocarbon of simpler structure of the gasoline series, either through dissociation of the molecular bonds, by thermal stresses exerted under vapor phase, or liquid phase, or both combined, or by molecular readjustments in the state of molecular instability, through incor-. poration of hydrogen or hydrogen carrying gases, both free, or in the way of hydrogen migration, it is apparent therefore that this cracking process can not over-crack hydrocarbons, nor can it fail to crack, provided the converter has established in its design all the finely graduated temperature pressure conditions, out of which each hydrocarbon present can choose its own specific requirements, when subject to fractional classification, progressing as fractional cracking, and distillation takes place in a uniform and molecular form.

The carbon precipitated through cracking in the cracking pans of the converter will be minimum and in molecular form, kept in suspension by the oil film under treatment, which will be flushed in the residuum pan 3, where it will be kept in suspension by the rotary motion of the reintroduced, superheated fixed gases and superheated steam, introduced through 4, Fig. 5, into distributor 6 of the residuum pan 3. The saturation of the residuum oil with precipitated carbon can of course be only carried to the point of a certain concentration, beyound which the carbon will drop out of suspension, no matter how intensely the agitation of the oil may be effected, therefore a certain amount of oil has to be allowed to pass the converter as a vehicle to carry out of the system the carbon,

to avoid deposition on the cracking ducts.

This oil however will reenter the cracking cycle after the removal of the carbon in a carbon separator CS Fig. 5.

The superheated gases, causing rotary agitation of the residual oil in pan 3, will at the same time cause cracking of this oil due to its superheat, and prevent carbon deposition in pan 3, due to agitation.

A flushoil from the cracking or refining system may also be used to flush continuously the residuum pan 3 and keep the carbon in suspension so that the cracking of the oil may be carried further than the carbon concentration of the oil would otherwise allow.

In Fig. 5, the fuel oil in tower base RoTo By closin valve 67 on fuel oil extraction line e0 an pan 3 and continuously flush out the precipitated carbon of the pan 3 into the carbon separator US, where it will be separated in a perforated cylinder S0, to be blown out from time to time through valve 76 into a carbon receptacle (not shown) whereas the carbon freed oil will pass the screen So and leave throughvalve 7 0 the separator CS, pass valve 69 to the heat exchanger HE, where its heat will be utilized in heating the incoming fresh oil under treatment, be cooled in cooler RC below the flashing temperature, and be released through trap t into the residuum oil tank RT, Fig. 5.

Loop 1 through which the residuum oil passes when valve is closed, serves the purpose to provide in the residuum pan 3 a seal, high enough so that all parts of the heating element exposedto the fire gases might be cooled by oil. In Fig. 5 this seal reaches up to the last pan l During the operation of the converter, this seal may be increased to such an extent that particularly the cracking pans with maximum precipitation of carbon might occasionally be flooded by this oil seal by closing valve 72 on the pan and then releasing this oil down to the normal level and so effecting a thorough flushing of the cracking pans, which operation might be repeated i necessary, for the purpose of cleanin these pans.

The flushing of all of the crac ing pans of the converter may also be accomplished by opening of valve 86 and closing of valves 67 and 67, so that the oil in the bottom of tower lEtoTo may be directed through line f0 to the top pan 1,, from where it will pour down over the pans and carry away any eventual deposits of carbon on these pans, down into the residuum pan 3..

Provision will also be made that water can be directed in this same line for the same purpose, if an occasion of necessity should arise as through the application of water over these pans, a thorough cleaning can be eflected, without any shutdown or resortin to any cleaning by hand, etc. I

The cooling eflect of water on the hot pans will pry loose any deposits of carbon through the action ofcontraction and vaporization of the water and the flushing may be kept up until the issuing water from the converter through valve 7 6 on carbon sepa rator CS is perfectly clean and free of care hon.

This cleaning operation, if necessary at all, will not take more than an hours time, so thatthe continuous operation of the equip ment is not interrupted. This of course means increased average capacity, at reduced wear and tear on converter and setting, be- .cause the shutdown and starting up of operation of a cracking equipment with its attendant sudden contractions through cooling, and expansions through reheating, contri ute mostly to the high cost of upkeep and operation and attendant depreciation of the equipment. Present day cracking processes are from three to four days in continuous operation, have then to be shut down for cleaning of carbon from the cracking ducts, etc., which requires about twelve hours time.

This means that 20% of the operating time will be taken up through shutdowns for cleaning, or that the operatingcapacity will be reduced by 25% in the most favorable cases. During the shutdown the. settin cools out and has to be reheated for 6 hours store the setting is brought back to balanced op erating conditions. This alternate cooling and reheating under forced conditions has the most destructive and disintegrating influence on the settin and equipment, with attendant high cost of repair and upkeep and operation. i

No shutdowns for cleaning of carbon are necessary in the process now described, with savings in fuel, labor, material and low upkeep as well as higher yields and higher average operating capacity.

The refractory flue bafie 23 acts as a heat accumulator, radiating the heat centrall to the surrounding heating element 12 wliich transfers this heat and the'heat of direct contact with the hot fire gases, to the metal bath of the cracking pans, which heat is then stored up to an even higher degree in these metal baths, and is graduall released by contact with the gliding oil filins, and through the metal walls of the cracking pans.

As the fusing points of these metal baths are increasing from the top pan 1 to the bot-. tom pan 1 according to the percentage mixtures of the metals already mentioned, it is apparent that fine graduations of temperature are obtained on each cracking level, and that uniform heat conditions will be established in these pans. Itwill further be seen that the amount of heat stored up in these pans is increasing from pan to pan downward in direct proportion with" the metal content of the increasin pans,

Due to the inertia of absorbmg heat from the hot firegases and due to the inertia in releasing this heat to the oil film, great uniformity in the supply of heat will be established and uniform cracking conditions insured. Any oversupply of heat through the hot fire gases will not be felt in the cracking pans, as this oversupply of heat will be stored up in the metal bath, and this store of heat can be drawn upon, when the oil supply over the converter should increase, insuring thus the same temperature stresses exerted upon the oil film. Should the supply of heat cease for any reason through burner trouble or any other cause, the balanced conditions I of heat in the converter would not be disinal heavy oil under treatment, or secondary or tertiary oil hydrocarbons, obtained in the course of cracking, which might have escaped conversion into desired light hydrocarbons of the gasoline series, will of course pass in vapor form from the converter, but will eventually be returned to the same through the dephlegmating actionexerted in tubular condenser D provided they were not converted through molecular readjustment in reaction tower RoTo and R T into desirable gasoline hydrocarbons. Or these escaped hydrocarbons will eventually be returned in the gas oil tower GT or kerosene tower KT if the boiling points of these hydrocarbons should be within the limits of these cuts, determined by the extraction temperatures T and T of these extracting units. If no extraction is eflected for their recovery in liquid coolers G and K and accumulators A and A through openin of extraction valves e and 6 then these hydrocarbons will be recycled in hot condition through lines g0 a ITd is into line and through 59 into top of tower R T and through 57 and 62 back to the distributing T D and vapor neck 9 back to the top pan of converter G, where it will start to undergo new treatment until the conditions for proper conversion are met. The amount of oil to be recycled will be a minimum, due to the great variety of means and fine graduations in temperature, to which the oil in fine film form will be subjected.

In present day high pressure stills the amount of recycled oil in relation to the unit of recovered converted lighter oil ranges from 6 to 1 up to 12 to 1, which means that for every unit of converted oil 6 units, and u to 12 units, have to be recycled, as a dea and very expensive load.

The reason for this small conversion in one cycle lies in the primitive means employed, and treatment of oil in bulk form without any classification of the oil complex under conversion and without means of control of that is, for every unit of recovered commercial gasoline, two units of oil will have to be returned for retreatment, provided the converter is not overloaded.

The converter of my process has therefore an efliciency of conversion from 300 to 600% greater than those of the present pressure still type. The attendant economy in fuel is evident in a marked degree and also evident I are the savings in capital of investment, due to the smaller equipment needed, etc.

Before closing the description of the cracking still or converter proper, it may be mentioned, that the heating of the oil to be converted, close to the limit of molecular instability, is not done in the converter proper, but in a separate tubular still PSt.

The heating of the oil close to cracking temperature is carried out as an operation of its own, and se arately under conditions most suitable for this purpose. The heating of the oil in tubular still PSt will be carried out above'the critical velocity of liquid flow, and under such pressure as to prevent any crack ing of the oil in the'pipe coil.

The oil to be converted enters therefore the converter at a temperature below the temperature of molecular instability of the high est boiling point hydrocarbons, and therefore of the most unstable hydrocarbons in the oil mass.

Only that amount of heat necessary to raise the temperature of the oil mass progressively from below the temperature of molecular instability to that of conversive cracking will be conducted to the heatingelement of the converter. This being the reason to control better the heat supply and the concomitant thermal stresses, increasing the running capacity of the converter and avoiding forced operating conditions with concomitant increase of wear and tear, as well as avoid fluctuations, which are unavoidable under forced operating conditions. I

The conditions of use as a cracking still will be referred to later.

Having now described the operation of the converter proper and pointed out its features of distinction and principles involved, I now proceed to describe the operation of the whole process as shown in the flow sheet drawing Fig. 5, with the function of all additional equipment involved.

With this process three distinct modes of operation are feasible which contribute greatly to its universal use, as being able to adapt itself to the most variable operating conditions, as they arise in the course of the operation of an oil refinery, supplying the needs of a variable market of refined oil products.

The three modes of operation are: 7

I. The process is operated as a stralght run crude oil refinery,vhaving as its object the fractional separation of the natural constituents of the crude oil in form of commercial cuts, as gasoline, naphtha, kerosene, gas oil, etc., with residual fuel oil.

II. The process is operated as a straight run crude oil refinery separating the natural constituents of crude oil as under paragraph I, but convert concomitantly certain fractions of the crude oil, for which no ready market exists, by cracking in the same cycle, into light gasoline hydrocarbons, and separating and refining same jointly with the natural constituents of crude oil.

III. The process is operated as'a cracking plant proper, converting into motor gasolines, either certain heavy'fractions of crude oil as kerosene, gas oil, wax distillate, or fuel oil; or cracking low gravity crude oils containing naturally no lighter constituents, di-

rectly into light motor gasolines, and to obtain these products 1n one cycle as a finished commercial product. When the process is operated asunder paragraph I, the converter C 1s used conjointly with tubular still'PSt,

increasing the operating capacity of the process as a straight refining process of crude oil as described under Letters Patent No.

1,490,055, to which is referred.

I therefore describe now the mode of operation as under paragraph H where the process performs conjointly in one cycle, the operation of fractional distillation and refining and cracking or converting heavy uridesirable fractions into motor gasolines, etc.

In Fig. 5, OT is the storage tank for crude oil to be refined and cracked. Through line 34 the oil is pumped through pump OP to line 35, where it can be metered by oil meter M on bypass of line 35. When bypass valve 38 is closed and valve 36 opened the oil passes through line 36 to the oil preheater HE, passes here in counter current with the hot residual oil from the system andv extracting the inherent heat of the same, leaving through line 37 the heat-exchanger and returning to line through opened valve 37 The oil thus preheated through the residual oil proceeds through line 39 to branch T 44. where it enters the tubular preheating coil 33 of the pipe still setting PSt, passing in counter current to the hot waste fire gases of the still P825 and converter C, supplied through flue 29. Leaving this preheater 33 through 45, the oil now enters the heating coil 32 proper of the tubular still PSt, rising in counter current to the hot fire gases upward and finally leaves heater coil 32 to enter line 32 is a combined gas and fuel oil burner supplying the fuel to a combustion chamber,

from where the hot fire gases pass in the direction of arrow 7 to enter the heating chamber with heating coil 32.

P and T are a pressure gauge and a thermometer registering the pressure of the oil in the coil and the temperature to which the same was raised. 7

Enough pressure in the heating coil of the crude oil Will be carried to allow some degree of overheat without causing any cracking or molecular dissociation in the heating ducts of 32.

/ impact and shock and cracking tendencies in their presence, as

pointed out in Letters Patent No. 1,490,055.,

The amount of pressure decided upon can be regulated through valve RV, which is constructed on the principle of an expansion relief valve.

A certain drop of pressure is allowed between valve RV and impact separator JS, midways between reaction towers RoTo and R T. This pressure drop or release of potential energy will document itself as dynamic or kinetic energy, imparting a high velocity to the heated oil mass and therefore a high kinetic momentum. When this kinetic momentum is so to speak absorbed by impact and shock in the impact separator J S three distinct ends are obtained:

1. Separation of the oil vapors from the heated liquid oil mass by breaking up the vapor oil emulsion.

2. Raising of the temperature of the heated oil mass due to transformation of the kinetic momentum imparted to the oil mass into heat which will be imparted to the oil mass and vapors.

3. Creating of a field of molecular instability of the most unstable heavy oil hydrocarbons of the oil mass by subjecting them'to an increase of temperature by mechanical partially breaking up their molecular bonds.

The heated oil mass passing reducing valve RV and pipe 46 at a high velocity, is divided into two streams entering through two tapered nozzles 47 and 48 on the impact separator IS, Figs. 9 and 10, which represent cross-sections through impact separator IS,

Fig. 11, through lines BB and 00. The impact separator IS consists .of outer shell 53 and inner shell 54, forming an annular space within which in the path of both oil streams entering through 47 and 48, are provided a series of deflecting baflies 49, 50 and 49 and 50, Fig. 9 and Fig. 10 which subject the oil jets to impacts and deflections in a rotary motion within this annular space.

Jet 47 turns the oil clockwise, whereas jet 48 at a lower level turns the oil anticlockwise, continuously deflected by the bafiles from the inner shell to the outer shell and vice versa, thereby breaking up the vapor oil emulsion through these deflections and impacts, separating thereby the vapors from the residual liquid oil mass. The released oil vapors will pass out of the path of the liquid oil mass through slots 51 and 52, Figs. 9 and 10.

These slots 51 and 52 are located on the inner shell 54 of separator IS behind the baffles 49 and 49', so to speak on the leeside 0f the direction of the'jets, so that no liquid oil can pass through them.

The oil vapors separated from the heated oil mass by impact and shock enter through slots 51 and 52 the interior of shell 54:, where they will establish with the vapors released from the superheated oil by impact, a field of molecular instability, in which field, the vapors and gases coming from converter C through tower RoTo will establish conditions of molecular readjustment, utilizing free hydrogen or hydrogen carrying gases to full advantage for synthetic absorption, saturation and constructive incorporation. The light oil hydrocarbons, inherent to the crude oil and. released in the impact separator IS, will be here also subjected to saturation if so required, and pass eventually into tower R T through the oil seal S, Figs. 11 and 5,

v where they will be subject to contact on the various seals S with different and graduated oil hydrocarbons in liquid state, through the action of fractional condensation continuouslygoing on in the tubular dephlegmator D 11 hydrocarbons heavier than those belonging to the gas oil out, will be condensed in dephlegmator D and be refluxed in liquid state to the seals S in tower R T flowing downward from seal to seal in counter current flow to therising oil vapors, released through impact separator. IS, and coming from converter through 9",and reaction tower RoTo as will be explained later. In addition to fractional distillation and fractional condensation, there will go on in these seals S, chemical reactions contributing to the proper molecular readjustment of the oil hydrocarbons recovered through straight distillation of the crude oil and cracking of its heavier fractions.

The residual li uid oil separated in the impact separator I being partially in a state of high molecular agitation, will proceed under the impulse of rotary motion, to pass the impact and bafile plates and enter finally the annular space freefrom bafile plates Fig. 9 and Fig. 10, where the two oil jets subjected to clock and anti-clockwise rotary motion, will meet each other in opposite direction, and interpenetrate each other, and thereby arrest its motion, releasing thereby the last traces of vapors and converting the residual kinetic mechanical energy into heat.

The interpenetrating oil jets, having arrestedits motion, will finally fall downward in the annular space between shells 54 and 53 and be stored in the seal 55' between shell 53 and the extension of the shell of tower RoTo. A pipe 56 afi'ords access to this seal when necessary. 7

On the downward fall of the hot oil mass therest of. the vapors encompassed in the oil will emerge and escape through circular space 55 into the interior of the separator shell 54 and tower R T The splashing effect of the oil into seal 55' will further contribute to the separation of vapors from the oil.

Finally the oil will overflow the seal 55 and gravitate down over tower RoTo, whose tower filling material, such as Raschig rings, will spread out the oil in a fine film form ofi'ering maximum, contact surface to the hot oil vapors and gas emerging from converter C on its upward course. It is in this vtower RoTo where the hot oil from the impact separator IS, partially at a high state of molecular agitation (the heaviest constituents) enters in contact with the cracked oil vapors of converter C and establishes in intimate contact with same those readjusting, saturating, and equilibrating chemical reactions, as an integral part to the operation of cracking of the heavy oils in the converter proper.

The residual fuel oil having passed the reaction tower RoTo, accumulates in the bottom of that tower from where it can be either extracted through line 60, by opening of valves 67 and 71, to give access to carbon separator CS, and through valves 7 0 and 69 pass the residual oil through heat exchanger HE, where it will be cooled by the incoming fresh crude oil on its way.to the pipe still PSt.

By opening valve 67 and closing valve 67 on line co, the oil may be used as a flushing medium of the carbon pan 3 of converter C, as outlined already under operation of converter C.

If it is decided upon to crack this residual oil in converter C, both valves 67 and 67 may be closed, so that the residual oil passes from the tower bottom through vapor neck 9" to distributing T D, Fig. 12, where it will pass over seal 9 in film form through pipe 9 in counter current to the rising vapors from converter C to the top pan 1 of heating element 12 of converter C, starting here its course over the cracking pans as already described.

Line f0 branching off of line 60 can also be used as supply line for the residual oil from the bottom of tower RoTo to the top pan of converter C by opening of valve 86. This line is also used for flushing purposes of cracking pans of converter as already mentioned under operation of converter C.

The hot residual oil, either extracted from tower RoTo or carbon pan 3 through valve 7 2 or from both, after passing heat exchanger HE, will now proceed over loop 1 to the aerial cooler RC where it will be cooled by means of a water spray to such a temperature that it may be stored in residuum tank RT without danger of flashing. Trap 23'' will release the oil under pressure in the system to the storage tank RT.

Dephlegmator D acting as a partial condenser in refluxing all heavier undesired oil constituents, which are not to pass tower R T as shown on the flow sheet Fig. 5, to be cooled by fresh cold crude, circulating outside of the cooling tubes, entering through line 42 at the bottom of D and leavingin a heated condition at the top through line 43.

tarmac This cold crude oil is taken from the pump P, metered through meter M which is bypassed to line 40, and the amount of which is regulated according to needs by valve 41, and passing through line 41 enters at 42 into dephlegmator D The amount of crude oil needed in D will be determined by thermometer T at the top of D Temperature of extraction measured by T is determined by the character of the deepest oil fraction desired, for example gas oil, in case that this product is to be extracted as a commercial product in gas oil tower GT and subcooler G and extraction line 90, extraction valve 6, and accumulator A This temperature is to be kcpt'uniform for a certain grade of crude for maximum desired extraction of this grade of gas oil.

The crude thus preheated in dephlegmator D joins the crude from the heat exchanger HE through line 43 at junction point at to resume with this crude the heating cycle through pipe still coils 33 and 32.

While this mode of operation of deplegmator D may give adequate results, its regulation is left to the attendance of the operator and therefore to the unreliableness ot' the human factor. The inventor therefore preters automatic homothermic regulation which is independent of the human factor after being once regulated.

This mode of regulation is shown in Fig. 6 and may also be used, and is used, for the regulation of the extraction temperatures of all subsequent dephlegmators D D D etc., for the various extracting tractionating towers GT, KT, NT, etc.

The operation of the homothermic regulation of these dephlegmators may be described as follows:

Each dephlegmator is provided with a certain cooling bath, consisting or any desired liquid with a certain boiling point. They may be certain close fractions of oil hydrocarbons with an averageboiling point, etc. This cooling medium will be stored either in the outer shell of the tubular dephlegmator or be stored in the receiver R, which is vented by pipe 80 and to which the cooling medium can be pumped through line 82. The bottom of receiver R is connected through line 81, having valve 85, with the bottom of dephlegmator D The top of the outer tubular shell of D is connected with a vapor line 7 9 leading to a coil condenser WC which condenser coil is located in a section of central water storage and distributing tank at the top of the tower building, housing the whole equipment. The bottom of this coil is connected to top of receiver lit. When the homothermic bath is supplied from lit to D accumulating around the heating or cooling tubes of D and the operation of the process is under way, then the bath fluid at its boiling point will be subject to boiling, absorbing the heat from the vapors passing through the dephlegmating tubes.

The vapors from the bath fluid will leave the dephlegmator through pipe 7 9 and enter the water cooled-condenser coil WC where condensation and cooling of these vapors will take place, and the condensate return to receiver 181, from. which the homothermic fluid will resume its cooling cycle through D The higher the heat absorption by the bath, the higher will be the rate of vaporization of same, and the higher will be the velocity of the fluid in the cooling cycle. Thermometer T will thereforealways indicate the same temperature, which is the temperature of the boiling point of the homothermic fluid.

In order to allow fine graduations in this temperature of extract-ion according to the operating requirements of difl'erent grades of oils, a direct acting thermostatic regulating device is provided in TE at the dephlegmator D connected with tubing 83 with a regulating slidDe valve 84, in bath supply line 81 from R to Tn regulating bulb TB. in the vapor space of D and connecting tubing 83, mercury may be provided (or any other medium) which expands and contracts with the increase or decrease of heat of the vapors in D passing the same. The pressure exerted by the expansion. of this mercury in bulb and tubing, may be used to act on a diaphragm of motor valve 84, opening the valve when the pressure increases, and closing the valve when the pressure is receding, etc. In this way a perfect automatic direct acting regulation of temperature is established by either storing up the cooling fluid in receiver R or releasing the same to D when needed by rising temperature, with the line variations lying in between these two extremes. If the temperature at T should decrease, then the pressure of mercury on diaphragm of motor valve will decrease, and according to the contraction the valve will be partially and proportionately closed. causing thereby the storing up of a part of the cooling fluid in receiver R, therefore reducing the cooling eflect in D until that temperature is reestablished at which the thermostat is set.

The advantages of this homothermic dephlegmation are manifold. The wear and tear on the cooling fines of D will be minimum because a perfectly neutral and harmless liquid 'may be selected. There will be no soiling of the dues through formation of incrustations, as by the use of cooling water, therefore no cleaning will be necessary. There will be the equalizing efl'ect of a flywheel in the operation of the cycle cooling, straightening out all fluctuations both ways.

The cleaning of the cooling water coil WC can be effected without stopping operation, as the cleaning can be done from the outside through scraping and flushing with water, etc. The condenser coils of all dephlegma- GT through line tors placed in a part of the water supply densers and subcoolers GC, G, K, N, etc.)

The vapors released in the impact separator IS from the heated crude oil and being subjected tofractional condensation and distillation in R T and being partially subjected to condensation in D in accordance with the requirements of extraction temperature T are now passed through vapor line 63 to the fractional extraction tower GT, where the complex mixture of oil vapors consisting of gasoline, naphtha, kerosene, and

oil, will be subjected to the first step of fractional separation and rectification, as outlined in Letters Patent No. 1,490,055. By

holding a certain extraction temperature of the vapors leaving dephlegmator D at T and causing fractional condensation and rectification in D and GT, gas oil can be extracted in liquid form at the bottom of tower 0, extraction valve e, through subcooler (3, and flowing to accumulator A provided with gauge glass d and extraction trap t which discharges the gas oil cut throu h line go to the run down tank (not shown S is a test cock in order to take a sample of gas oil for testing from the stream. Accumulator A is vented through f and F over relief valve SV to the open air, by opening of valve AV.

Air vent valve AV will be open only. at

the start of operation to purge-the system of air, and will be closed when the process is under normal operation and if any fixed ases should go off from the accumulators i A, A, A through f, f, f, ff, in which case these gases will be conducted through line F to gas-holder GH, where these gases may be stored for further use, as will be pointed out later.

In the kerosene tower extraction of kerosene will be carried out, as described for gas oil. Through fractional condensation in D and fractional distillation and rectification in KT, kerosene can be extracted at the bottom of KT through valve 6', subcooler K, line In and accumulator A ,'where trap t will discharge the kerosene to run down tank through line k s is a sample cock, (1 a gauge glass, etc.

The next product to be extracted will be a benzine or naphtha, effected in tower NT in the same manner, by establishing a proper extraction temperature at T in the vapor exit of D, causm therefore a certaln partial condensation in fractional distillation, condensation and rectification in NT, etc., extracting the naphthathrough 'n, N, n into A, it through n into run down tank.

The last product will be gasolme, commercially pure, the vapors of which will be condensed and cooled ,in condenser GC, sepastrai ht refining) which are extracted from GS t rough pipe f and supplied tangential- 2' to annular space between accumulator shell and adsorption tower shell Ad.

The gases, freed of any gasoline, leave through f to F andF to gas-holder GH where they await further use.

Gasoline is discharged from A through trap t, through g into run down tank.

The description of the rocess so far pertains to straight crude Oll refining, obtaining the conventional commercial cuts, as enumerated. If now any of the commercial cuts of heavy oils, as gas oil or kerosene, should be difficult to be marketed, and therefore found necessary to be converted into motor gasoline, the only thing to do for the operator isto close extraction valves e and e for gas oil and kerosene and prevent any exit of these products in the above mentioned way.

Not finding exit, gas oil and kerosene will rise in pipes g0 and until they reach overflow pipes go and k where they will flow to siphon 60, which leads to the service floor. By opening of valve 60' both products rise in 59 and enter at the top of reaction tower R T where they will fall from seal to seal, fulfilling the action of a phlegma, and being thereby reheated until they reach the last seal S and leave reaction tower R T throu h 57 and by opening of valve 62 with closed valve 59', will proceed through 62 to distributing head D of converter G. From here these two products will be filmed downward over 10', Fig. 12, and 9 and 10 to the top pan of the converter C.

Filming from pan to pan downward both products will be subject to the thermal stresses of cracking, after they have been classified by fractional distillation etc.. as described under operation of converter C.

The cracked vapors and gases rising upward, leave through 9 and 9", converter C in counter current with the fresh oil films supplied through 62. The vapors then pass the interior of impact separator IS, which represents a field of molecular instability of the heaviest oil hydrocarbons in which field molecular readjustments of the vapors and gases coming from the converter will find an optimum of reaction in vapor phase entering in equilibrium reaction with the vapors separated from the hot oil mass in impact separator IS, which are partially in a high (1 on top of accumulator A, and filled

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