US2132964A - Method of and apparatus for heating hydrocarbon oils and components thereof - Google Patents

Description

A. E. NASH ET AL Oct. 11, 1938.

METHOD OF AND APPARATUS FOR HEATING HYDROCARBON OILS AND COMPONENTS THEREOF Filed May 16, 1934 3 Sheets-Sheet 1 1 um 2w R aw Mm Rb smu E MN Q6 638% WEED-N GERWQQQQLQ IN ENT R3 ZZM'ATTORNEY.

Oct. 11, 1938. A. E. NASH ET AL METHOD OF AND APPARATUS FOR HEATINGHYDROCARBON OILS AND COMPONENTS THEREOF Filed. May 16, 1934 3 Sheets-Sheet 2 INVENTORS l M w ATTORNEY.

- i i n n n N N i n i A. E. NASH ET'AL 2,132,964

3 Sheets-Sheet 3' 5335 Man Oct. 11, 1938.

METHOD OF AND APPARATUS FOR HEATING HYDROCARBON OILS AND COMPONENTS THEREOF Filed May 16, 1934 1\ =1 .I' y) kuobw do v INVENTORS M 1 63M WMATTORNEY. I

kwk s A V baw W WSRQQQQM Patented Oct. 11, 1938 V UNITED STATES METHOD OF AND APPARATUS FOR HEATING HYDROCARBON OIL THEREOF Arthur E. Nash, Mount Airy,

Jenkintown, Pa., assignors Franklin E. Shelly,

S AND COIVIPONENTS Philadelphia, and

to Alcorn Combustion Company, Philadelphia,

Pa., a corporation of Delaware Application May 16, 1934, Serial No. 725,940

8 Claims.

Our invention relates to methods of and apparatus for heating fluids, and especially oils;

and more particularly for heating petroleum or which the petroleum and/ or components are separable into oils, generally in vapor or vaporous and liquid phases, comprising components of boiling ranges less than the boiling range of the charging stock, and the oils so separated from each other .are then individually heated under conditions differing in one or more of the conditions of temperature, pressure, rates of heating and/or periods of time, to crack them or effect their conversion into lower boiling hydrocarbons to better advantage or with better results than if the hydrocarbon oils or charging stock were as a whole subjected tothe same conditions; and more particularly in accordance with our invention one of the aforesaid separated components may be further separated into further components which are then individually heated, generally under different conditions.

Further in accordance with our invention, the components which have been separated and individually heated under different conditions may thereafter be separately further treated or, and generally, they may be recombined and together passed through the system for one or more further steps of treatment.

7 Further in accordance with our invention, the separated components are individually heated in different zones of a furnace or heating system, generally by radiation and/or radiation and convection, and the heating preliminary to the separation of the oil into its aforesaid components is effected, generally, largely by convection, by a combination of gas streams from the several zones of the furnace or heating system.

More specifically in accordance with our invention, the several steps comprised therein, that is, the preliminary heating, the separation into fractions or components, and the individual heating of the components, are all accomplished under pressure'to which the oil or petroleum is raised either before or after the first heating step. By this arrangement only a single hot oil pump is required for handling both components or fractions of the heated oil, the pressure developed by this single pump being suificient to force the oil through the complete conversion or treating system, and particularly to maintain when desired on the several components pressure or pressures, generally superatmospheric, suitable to the temperatures to which the components are raised while individually or separately heated.

For a better understanding of our invention, together with other and further features thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings, Fig. 1 is a diagrammatic representation of a system for converting or treating hydrocarbon oils, including our improved heating system, and showing in cross-section a furnace particularly suitable for heating hydrocarbon oils in accordance with our invention.

Figs. 2 and 2a are longitudinal and cross-sectional views, respectively, of a separating apparatus suitable for use in connection with our improved system, while Fig. 3 shows a modified form of our invention employing two separators and applied to a modified cracking or conversion process.

Referring now more particularly to Fig. 1 of the drawings, there is shown a complete oil conversion system embodying our invention, the flow of oil through the system being as indicated by the arrows. Fresh oil stock is supplied to an inlet l and passes therefrom through suitable storage tanks or receivers II from which it is drawn by a pressure booster pump I2 and passed through a heat exchanger, indicated schematically at I3, to be referred to hereinafter. The oil, after preliminary heating in the exchanger !3, is drawn by the hot oil pump I4 and forced under pressure to the main heating apparatus or furnace of the system. This heating furnace may be of any of the several well-known types, although we have illustrated a furnace particularly suitable for use in our invention and comprising side-wall and roof structures l5 of suitable refractory material. Associated with the outer side walls l5 are a pair of independently adjustable or controllable burners. l6 and I1 and cooperating auxiliary combustion chambers l8 and I9, respectively, having walls and/or top plates of highly refractory material, such as silicon carbide. It will be understood that any desired type of fuel, such as oil, gas, or pulverized solid fuel may be supplied to the burners I6 and II. The housing structure of the furnace comprising the walls and roof structure l5 defines a plurality of compartments, fire chambers, or zones A and B separated by upright barriers or bafiles 20 also of refractory material. The baffles 23 may define, also, a third heating compartment or zone C. The currents of hot combustion gases from the chambers I8 and I9, passing outwardly and upwardly through the zones A and B, combine and pass downwardly through the zone C.

In the zone C is disposed a heat-absorption structure, such as a bank of oil-conducting tubes 2I, connected, as illustrated, to the hot oil pump I l. The tubes 2| are washed or swept by the currents of hot combustion gases and are adapted to be heated preponderantly by convection, although, in some instances, a certain amount of radiant heating may be effected, particularly in the upper portion of the zone C, by virtue of the baffles 23 reaching radiant temperatures.

After a mechanical preliminary heating in the bank of tubes 2 I, the oil is conducted to a separating apparatus S which may be of any several well-known types, although I have shown in Figs. 2 and 2:1, by way of example only, one structure suitable for this purpose. As shown in detail in these figures, the separator comprises a substantially cylindrical casing 22 with a top plate 23. The lower portion of the housing 22 converges into a conical chamber 22a connecting with, a liquid outlet 24. Depending from the top plate 23 are aseries of baiile plates 25 arranged in staggered relation, as shown clearly in Fig. 2a, providing a tortuous path for the combined vapors and liquids from the bank of tubes 2| in passing from the inlet 23, through the separator S and to the vapor outlet 21 and liquid outlet 24.

The vapor outlet 21 is connected to a bank of roof tubes 28, a bank of wall tubes 29, and a bank of floor tubes 30, all disposed in the zone A of the heating furnace. The liquid outlet 24 is connected to similarly arranged banks or groups of tubes 3 I, 32 and 33. As stated above, the bank of tubes 2| is disposed in the path of the combined currents of gases from the combustion chambers I8 and I9, to be heated preponderantly or substantially solely by convection. On the other hand, the banks of tubes 28, 29, 3| and 32 disposed adjacent the roof and side walls of the furnace chambers may be partially wholly outside of the paths of the currents of gases through the furnace, and may receive heat preponderantly or substantially solely by radiation, although, in cer= tain instances, it may be desirable to so relate these banks of tubes to the currents of gases that they receive also a component of heat by convection from the gas streams. The banks of floor tubes and 33 are heated preponderantly or substantially solely by radiation from the currents of gases, which pass inwardly and upwardly from the combustion chambers I8 and I9 sweeping or washing the banks of tubes 39 and 33 to an inconsiderable extent.

Ordinarily, it is desirable to conduct the second stage of heating of the liquid component of the oil at a reduced pressure and, for this purpose, a pressure-reducing valve 34 is interposed in the connection to the liquid outlet 24. The vapor and liquid components orfractions, after passing through the second stage of heat-absorption structures just described, are recombined into a common outlet. In order approximately to equalize their pressures before recombining, a

pressure-reducing valve 35 is connected in the outlet from the bank of tubes 30. In addition, it may be desirable to include a pressure-reducing valve 36 in the common outlet of the banks of tubes 39 and 33 before passing the combined vapors and fiuid through the remaining stages of the cracking or refining system.

The combined vapors and fluid thus subjected to preliminary heating may be further cracked, refined or converted in accordance with any desired method or system. By way of example only, we have shown one such system in which the common outlet for the combined vapors and fluid is connected to the inlet 38 of an evaporating tower 39 to which is connected also a conduit 3'! leading to a supply of cooling oil. The tower is provided with a live steam inlet 4!! connected to a spray 4| disposed in the bottom thereof. In addition, an inlet 42 for reflux oil is provided in the top of the tower 39 and connected to a spray 43. An outlet 44 effective to draw ofi the unconvertible or tarry residues, this outlet being connected to a coil 45 of the heat exchanger I3.

The outlet 46 of the evaporator 39, through which passes the combined vapors and liquids, is connected through a conduit 41 to the inlet 48 of a fractionating column 49. The column 49 has a reflux oil inlet 50 connected to a spray 5| situated in the top of the column. The lower outlet of the column 49, for the unconverted or uncracked liquid or liquid components of the oil, is connected to a cooling coil or condenser 52, the outlet of which is connected to the oil stock inlet III. The cooling coil 52 is connected also through a reflux pump 53 to the reflux inlet 42 of the pre= ceding evaporating tower.

The outlet 54 of the column 49, for the converted or cracked vapors, is connected to a condenser 55 which, in turn. is connected to the inlet 56 of a distillate receiver 51, in which the several components are separated by gravity or otherwise. The receiver 5-! has an outlet 58 for gas, which may be used for illumination, industrial or demestic heating, or the like, an outlet 59 for gasoline, and an outlet 60 in the bottom thereof for drawing off the water condensed from the processing steam. A portion of the gasoline thus produced may be drawn through the conduit ii! by a reflux pump 62 connected to the reflux inlet 50 of the preceding fractionating column 49.

The operation of the above-described apparatus for conducting the preliminary heating of the oil will be well-understood from the foregoing description. In brief, the fresh oil stock, together with any unconverted oil from the fractionating column 52, is passed through the heat exchanger or economizer I3 by the booster pump I2, the exchanger I3 being effective only to conserve heat remaining in the tarry residues flowing from the evaporating tower 39. This preheated oil is then drawn by the hot oil pump I4 and forced through the bank of tubes 2| located in the zone C of the furnace chamber. The oil is heated moderately in this bank of tubes and reaches a'temperature, for example, of 600 or 800 F. During this preliminary heating, certain of the lighter fractions or components of the oil are vaporized.

The combined vapors and liquid flow from the bank of tubes 2| to the inlet 26 of the separator S, the mixture impinging upon the staggered baffles 25, which aid in separating the liquid from the vapors, the liquid draining down the baflies 25, as indicated by the arrows in Fig. 2, and the vapors passing threugh the tortuous path between the baflies and to the outlet 21. As shown, the separator S forms a neutral temperature and reaction zonesinceheat is neither added to nor subtracted from the stock which at this time is not subjected to further treatment. As already indicated, the sole function of the separator S is to separate mechanically the stock into its liquid and vaporous components. From the outlet 21 the vapors are passed through the banks of tubes 28, 29 and 30 where they are raised to their final cracking temperature which, by way of example only, may be in the neighborhood of 1000 F. The liquid component passes through the outlet 24 of the separator S, the pressure-reducing Valve 34, and through the banks of tubes 3|, 32 and 33 in which it is heated to its final cracking or converting temperature, which, by way of example only, may be in the neighborhood of 900 F.

By this means, the original oil stock is converted into two components, each of which is more homogeneous than the entire stock, and each of which may be cracked or refined at a temperature better suited to its particular physi cal and thermal characteristics. Thus, a maximum cracking or converting takes place without over-cracking or coking of the heavier compo nents, which might take place if they were subjected to the higher temperatures to which the lighter components are heated, or without the under-cracking or incomplete conversion of the lighter components, which would result from treating the whole stock at the lower temperature of the liquid component.

It will be understood that the particular connections and arrangements of. the several banks or groups of oil-conducting tubes in the zones of the furnace chamber are purely illustrative, and that any other arrangements or combinations of banks of tubes may be utilized for the several heating stages; that is, the initial heating of the whole oil stock and the final heating of the two components. It will be understood, also, that .the disposition of the several banks of tubes within the furnace may be such as to transfer heat thereto in the several zones by radiation, convection, or combined radiation and convection, in accordance with the requirements of the particular furnace and the particular oil stock which is being treated. Further, the several stages of heating may be effected by any other suitable apparatus, that illustrated in Fig. 1 being merely one apparatus which, by virtue of the separate control of the two currents of hot combustion gases by the burners I6 and I1, is particularly adapted to the practicing of our invention.

The vapor and liquid components, after passing through the heating stages just described, are recombined and, since the pressure of the liquid component has been reduced by the valve 34, it may be advisable to include a pressurereducing valve 35 in the path of the vapor com- ,ponent before recombining the two fractions. Also, a pressure-reducing valve 36 may be desirable for reducing the pressure of the recombined components before subjecting them to the remaining stages in the cracking, refining, or converting process.

The subsequent stages of the process for completing the conversion of the oil stock forms no part of our invention but, by way of example only, the operation of the particular system described above will be briefly explained. The recombined vapor and liquid components passing from the heating furnace are conducted to the inlet 38 of a fractionating tower where they are combined with a component of cooling oil, which may be fresh oil stock or any uncracked or unconverted fraction from an intermediate stage in the converting process. In the tower 39 they are subjected to live steam from the spray 4|, together with a reflux spray from the nozzle 43, which sprays are effective to aid in the separation of the vapor and liquid components. The unconvertible or tarry residue passes off through the outlet 44 in the bottom of the tower, preheating the fresh oil stock in the heat exchanger i3, and passing on to any suitable storage chamber.-

The converted components in a vapor state pass through the upper outlet 46 of the tower 39 and into the inlet 48 of a fractionating column where they are subjected to a reflux spray from the nozzle 5|, which is effective to condense incompletely converted components or fractions. These unconverted fractions pass out through an outlet in the bottom of the column 49 and through a suitable cooling coil 52 to be added to the fresh oil stock. A portion of this unconverted oil may form the re-cycling or reflux fluid for the preceding evaporating tower. The converted or cracked fractions in a vapor state pass through the upper outlet 54 of the fractionating column 49 and through a condenser 55 where they are liquefied, the liquid condensate or dis- 'tillate passing into the receiver 51. In this receiver the condensed liquids are separated by gravity, or otherwise, from entrained vapors which are supplied to a suitable gas conduit 58. The gasoline is drawn off from the outlet 59 while water, condensed from the treating steam, is drawn off through the outlet 60. A portion of the converted gasoline may be used for the reflux spray 5| of the preceding fractionating column,

as illustrated.

In Fig. 3 is shown a modification of the heating system of Fig. 1, employing two seriesconnected separators. The oil from the heating system is shown, also, as applied to a slightly different cracking or refining process. As in the arrangement of Fig. 1, the oil stock supplied to the inlet I is raised to an elevated pressure by the hot oil pump l4, which forces it through bank of tubes 2| for a stage of preliminary heating. In this instance, the bank of tubes 2| is connected to a bank of roof tubes 63 which, in some instances, may be desirable to raise the oil to a satisfactory temperature before it is conducted to the inlet 64 of the separator S|. The vapor component from the separator SI passes from the outlet 65 through the banks of tubes 66 and 61, arranged similarly to the banks of tubes 28 and 30, respectively, of the apparatus of Fig. 1. The liquid component passes from the lower outlet of the separator Sl, through a bank of roof tubes 68 in the chamber B, thence to the inlet of a second separator S2. The vapor component outlet 10 of the separator S2 is connected to a bank of floor tubes H, while the liquid component outlet 12 is connected to a second bank of floor tubes 13. The outlets l4, l and 16 of the vapor components from the separators SI and S2 and the liquid component of the separator S2, respectively, are connected to a common conduit or outlet 11. As in the system of Fig. 1, pressurereducing valves 18 and 19 are connected in the liquid component outlets of the separators SI and S2, respectively, while the pressure-reducing valves 80 and 8| are connected in the outlets 14 and 15 of the vapor components from the separators SI and S2, respectively, before recombining the several components in the common outlet 11. The operation of the heating apparatus just described is substantially similar to that of Fig 1 with the exception that, in this instance, an additional separating and heating stage is added, thus separating the oil stock into three fractions or components, each of which is substantially more homogeneous as regards its physical and thermal characteristics than the fresh oil stock. For example, the vapor component from the separator SI, heated in the banks of tubes 69 and 61, may comprise a mixture of only the lightest fractions, which may be cracked or refined at a relatively high temperature. The liquid component from the separator Si, passing through the bank of tubes 68, is raised to a somewhat higher temperature, vaporizing slightly heavier or intermediate fractions which are separated in the separator S2 from the heaviest fractions, these intermediate fractions, in a vaporized state, being finally heated in the bank of tubes H at an intermediate temperature. The heaviest fractions, passing from the liquid outlet 12 of the separator S2, may be heated more moderately to avoid overcracking or coking thereof. The several components are then recombined in the com mon outlet T! from which they pass to the remainder of the cracking or refining process.

It will be understood that the arrangements and connections of the particular banks or groups of tubes utilized'in the several heating stages just described above are subject to wide variations to suit the requirements of the particular heating furnace and the particular oil stock being treated. It will be clear, also, that while the banks of tubes 63, 96 and 88 are arranged similarly to the banks of tubes 28 and 3| of Fig. 1, and receive heat preponderantly by radiation, while the tubes 61 and 13 are disposed similarly to the banks of tubes 30 and 33 of Fig. 1 and receive heat substantially solely by radiation, the disposition ofthese several banks or groups of tubes may be varied to vary the mode of heat transfer, as by radiation, convection or combined radiation and convection, in accordance with the requirements of the particular system.

It will be clear, also, that, while we have illustrated the use of two separators for breaking down the fresh oil stock into three components or fractions for separate heating to cracking or converting temperatures, the system may be extended to employ any desired number of separators to separate the oil stock into a corresponding number of fractions, each having a homogeneity within any desired limits.

' By way of further example, there is disclosed a modified system for completing the conversion of the oil. In this system, the oil, heated as just described, is passed from the common outlet 11 to a reaction or digesting chamber 82 where the vapor and liquid mixture reaches a state of equilibrium and the cracking process proceeds without the addition of further heat. The combined liquid and vapors pass from outlet of the reaction chamber 82 into the inlet 83 of a flash chamber 84, a supply of cooling oil from the conduit 85 also being connected to the inlet 83. The cooling oil may be supplied from the fresh oil stock or from any other intermediate stage of the conversion process.

In theflash chamber, the vapor and liquid mixture under high pressure expands rapidly, vaporizing all of the components except the heavy,

tarry residues, which are drawn off from the lower outlet of the chamber 84. The converted and vaporized fractions pass upwardly through the outlet 86 and combine with fresh cooling oil from the inlet 81 connected with the inlet 88 of a fractionating column 89. A reflux inlet 90 is connected to a spray 9| disposed in the top of the column 89, while a liquid outlet 92 receives the unconverted or heavier fractions, which are recombined with the fresh oil stock. The lighter converted or cracked fractions 'pass upwardly through the outlet 93 to a condenser 94, and the condensed liquids therefrom flow through an inlet 95 of a condensate or distillate receiver 96, where theyare separated into gas, gasoline and water, as in the system of Fig. 1.

While we have described what we at present consider the preferred embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention and we, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention,

What we claim is:

1. An oil-heating system comprising a heating chamber, means for passing therethrough a plurality of independently controllable currents of hot combustion gases, said chamber comprising a zone traversed by the combined currents of gases, oil-conducting heat-absorption structure disposed in said zone to be heated substantially by convection, means connected with said absorption structure for separating the oil therefrom into liquid and vapor components, oil-conducting heat-absorption structure connecting the liquid component outlet of said separating means and disposed below and without one of said currents of gases and absorbing heat substantially solely by radiation from said one of said currents of gases, other oil-conducting heat-absorption structure connected to the vapor component outlet of said separating means and disposed below and Without the other of said current of gases and absorbing heat substantially solely by radiation from said other of said currents of gases, said last-named heat-absorption structures being directly connected to a common outlet for immediate mixture of said vapor and liquid components after their passage through said structures, pressure-producing means individual to the system connected to said first-named structure for producing flow under pressure of charge-oil and its said components through said oil-conducting structures.

2. In an oil-heating system,'the method of cracking oil which comprises burning fuel at separate points to generate heat, passing the currents of hot combustion gases through a plurality of zones, certain of which are individual to said currents and one of which is common I to all of said currents of gases, elevating chargeoil to an initial pressure suflicient to produce flow thereof through the system, passing oil through heat absorption structure located in said common zone, transferring by convection a portion of the generated heat to said structure in said common zone to convert the oil into liquid and vaporous components, separating the heated oil into liquid and vapor components, utilizing said pressure separately to pass all of said components through heat absorption structures located in other of said zones, individually transferring heat substantially solely by radiation from said gases to said structures located in said other zones to elevate the components to their respective conversion temperatures, and while at their said conversion temperatures recombining all of said components for further treatment.

3. In an oil-heating system, the method of cracking oil which comprises burning fuel at separate points and different rates to produce in oil-conversion zones independently controlled temperatures, passing the currents of hot combustion gases through a plurality of said zones certain of which are individual to said currents and, one of which is common to all of said currents of gases, the temperature of one of said currents of gases being higher than the temperature of the other, passing oil under substantial initial pressure through heat absorption structure located in said common zone, transferring by convection a portion of the generated heat to the structure in said common zone to convert the oil into liquid and vapor components, under pressure mechanically separating the heated oil into said liquid and vapor components, utilizing said pressure to pass said vapor component through heat absorption structure exposed to and substantially out of the path of the higher temperature combustion gases, utilizing only a part of said pressure to pass said liquid component through heat absorption structure exposed to and substantially out of the path of the lower temperature combustion gases, individually transferring heat substantially solely by radiation from said gases of differing temperature to said liquid and vapor containing structures individually to elevate them to their conversion temperatures, and under pressure recombining said components while at their said conversion temperatures for further treatment.

4. An oil heating system comprising a single heating compartment, baffle structure forming within said compartment separate fire chambers, and a convection chamber, adjustable fuel-burners for producing currents of hot gases individual to said fire chambers, the combined currents of hot gases passing through said convection chamber, oil-conducting heat-absorption structure disposed within one of said chambers and absorbing a part of the generated heat to convert the oil into vaporous and liquid components of substantially different boiling ranges, means for subjecting charge-oil to substantial initial pressure, a mechanical separator connected to said heat absorption structure for separating said components from each other, oil-conducting heat absorption structures disposed within said fire chambers and without the currents of gases individual thereto, and individual means connected to said separator for conducting selected vaporous and liquid components of the oil to said last-named heat absorption structures, the components of the oil by said initial pressure flowing through said structures, each of said last-named structures absorbing substantially solely by radiation generated heat in amounts sufiicient further to convert the respective components into additional components of still other boiling ranges without overcracking thereof, the amounts of heat generated in each fire chamber being dependent upon the setting of the adjustable burners individual thereto, to provide a wide range of temperature control of said oil-conducting heat absorption structures disposed in said fire and convection chambers and a common outlet, directly connected to said structures, within which said selected vaporous and liquid components commingle while at their conversion temperatures.

5. A system of heating oil and components thereof to conversion temperatures comprising a single heating compartment, bafile structure forming within said compartment separate fire chambers and a convection chamber between said fire chambers, adjustable fuel-burners for producing currents of hot gases individual to said fire chambers, the combined currents of gases passing through said convection chamber, oilconducting heat-absorption structure within said convection chamber, means producing a substantial initial pressure upon charge-oil to force its passage through said structure, said structure absorbing heat from said gases-to convert the oil into vaporous and liquid components of substantially different boiling ranges, a separator for dividing said vaporous and liquid components, means connecting said structure to said separator for passage of the oil thereto, oil-conducting heat-absorption structure in each of said fire chambers disposed along the floor thereof and without the current of hot gases individual thereto, means connecting an absorption structure in one fire chamber to said separator for passage of a liquid component therethrough, and for connecting an absorption structure in the other fire chamber for the passage of a vaporous component therethrough, said initial pressure producing means alone producing passage of said oil and its components through said structures and said separator, the burners individual to each fire chamber being adjusted to control the temperature rise of said components further to convert the respective vaporous and liquid components without over-cracking thereof, and means, forming a common outlet to said structures, within which said liquid and vaporous components commingle While at their respective conversion temperatures.

6. On oil heating system comprising a single heating compartment, baflie structure forming within said compartment separate fire chambers and a convection chamber between said fire chambers, adjustable fuel-burners for producing currents of hot gases individual to said fire chambers, the combined currents of gases passing through said convection chamber means for producing a substantial initial pressure upon the charge-oil, oil-conducting heat-absorption structure connected to said pressure producing means and disposed within said convection chamber for absorbing heat from said gases to convert the oil into vaporous and liquid components of substantially different boiling ranges, separating means connected to said structure for dividing said converted oil into at least one liquid component and at least two vaporous components, heat absorption structures in each of said fire chambers, individual means connecting said lastnamed structures for passage of the vaporous component having the lowest boiling range to heat absorption structure disposed along the floor of, and without the path of gases in, one fire chamber, and for passage of other of the vaporous components and said liquid component to said other structures disposed without the current of hot gases within said other fire chamber, said pressure producing means alone being effective to produce under pressure, flow of said charge-oil and its said components through the system, and said fuel-burners being adjusted for production of a substantially higher temperature in one fire chamber than in the other for further conversion of said components without overcracking thereof, and means forming a common outlet to at least said structures through which pass said, vaporous components for mixture of at least said vaporous components while at their conversion temperatures? '7. In an oil heating system, the method of heating chargeeil to cracking temperature which ccmprises initially raising the charge-oil to a pressure sufficient to produce flow of the oil from 'inlet to outlet of the systemfi'n one some of the system transferring heat toffthe oil to produce conversion thereof into liquid and vapor components, in a neutral temperature and reaction zone mechanically separating the heated oil in a plurality of successive stages into liquid and vapor components of respectively differing conversion temperature, in different zones of the system transferring heat to said respective vapor components individually to elevate them to their respective conversion temperatures, reducing the pressure of the liquid component of each stage and thereafter transferring heat to eachsaid liquid component before enteringthe next succes sive stage, and in a neutral temperature and reaction zone recombining the vapor components of the several stages with the liquid component of the final stage for further treatment.

8. Ai system of heating oil and components thereof to conversion temperatures comprising currents of gases passing through said convection chamber, tubular oil-conducting heat-absorption structure within said convection chamber, tubular oil-conducting heat-absorption structures lo cated adjacent the roof and floor of eafch of said fire chambers, means for passing elharge-oil through said first-named structure to convert the oil into components of substantially diiferent boiling ranges, means for simultaneously passing one of said components in series through the structures adjacent the roof and floor of one of said fire chambers, and the other of said components in series through the tubular structures adjacent the roof and floor of the other fire chamber, thereby to procure by adjustment'of said fuel burners independent pontrol of the temperature rise of said components during their passage through said' separate fire chambers, and means forming a common outlet to said structures within said fire chambers for immediate mixture therein of said components after passage through said last-named structures. Y 'ARTHUR E. NASH. i

' FRANKLIN EFSHELLY.

. v CERTIFICATE OF CORRECTION. Patent No 2,1 2,961 october 14, 19 8.

' ARTHUR NASH, Er n.

It is hereby dert ified th gt 'eri'or appear; in the rinted specification of the abve numbered patent requiring oi-retipn as follows: Page 2,'firt columh, line 25 strik out the word. "mechaziiali" insert the 'sanie after the article j'a", line 21;; page 5,-second co1mnn, 11ne h2, c laim 6 for "Oh" r'ead An; line 14.9, same claim, after chaYnbeh" inseht acomma; and that the said. Lettehs Patent Shouidbe read with thi', corr ectio n thre'in that the same" may 'conformto the re cor'cl f the ca'e in 15115 Patent Office.

Signed and. sealed th i ,s" 6th day of Decen xb er, A. D.- ;L958. v 1

Henry Van Arsdale (Seal); I Acting Cpmmissionef of'Patentm

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