Abstract:
A method for thermally cracking a feed composed of whole crude oil and/or natural gas condensate using a partitioned vaporizer to gasify the feed before cracking same.

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     This invention relates to the formation of olefins by thermal cracking of liquid whole crude oil and/or condensate derived from natural gas. More particularly, this invention relates to utilizing whole crude oil and/or natural gas condensate as a feedstock for an olefin production plant that employs hydrocarbon thermal cracking in a pyrolysis furnace in combination with a partitioned vaporization unit. 
     2. Description of the Prior Art 
     Thermal (pyrolysis) cracking of hydrocarbons is a non-catalytic petrochemical process that is widely used to produce olefins such as ethylene, propylene, butenes, butadiene, and aromatics such as benzene, toluene, and xylenes. 
     Basically, a hydrocarbon feedstock such as naphtha, gas oil, or other fractions of whole crude oil that are produced by distilling or otherwise fractionating whole crude oil, is mixed with steam which serves as a diluent to keep the hydrocarbon molecules separated. The steam/hydrocarbon mixture is preheated to from about 900 to about 1,000 degrees Fahrenheit (F.), and then enters the reaction zone where it is very quickly heated to a severe hydrocarbon thermal cracking temperature in the range of from about 1,450 to about 1,550 F. Thermal cracking is accomplished without the aid of any catalyst. 
     This process is carried out in a pyrolysis furnace (steam cracker) at pressures in the reaction zone ranging from about 10 to about 30 psig. Pyrolysis furnaces have internally thereof a convection section and a radiant section. Preheating is accomplished in the convection section, while severe cracking occurs in the radiant section. 
     After severe thermal cracking, the effluent from the pyrolysis furnace contains gaseous hydrocarbons of great variety, e.g., from one to thirty-five carbon atoms per molecule. These gaseous hydrocarbons can be saturated, monounsaturated, and polyunsaturated, and can be aliphatic, alicyclics, and/or aromatic. The cracked gas also contains significant amounts of molecular hydrogen (hydrogen). 
     Thus, conventional steam (thermal) cracking, as carried out in a commercial olefin production plant, employs a fraction of whole crude and totally vaporizes that fraction while thermally cracking same. 
     The cracked product is then further processed in the olefin production plant to produce, as products of the plant, various separate individual streams of high purity such as hydrogen, ethylene, propylene, mixed hydrocarbons having four carbon atoms per molecule, fuel oil, and pyrolysis gasoline. Each separate individual stream aforesaid is a valuable commercial product in its own right. Thus, an olefin production plant currently takes a part (fraction) of a whole crude stream and generates therefrom a plurality of separate, valuable products. 
     Natural gas and whole crude oil(s) were formed naturally in a number of subterranean geologic formations (formations) of widely varying porosities. Many of these formations were capped by impervious layers of rock. Natural gas and whole crude oil (crude oil) also accumulated in various stratigraphic traps below the earth&#39;s surface. Vast amounts of both natural gas and/or crude oil were thus collected to form hydrocarbon bearing formations at varying depths below the earth&#39;s surface. Much of this natural gas was in close physical contact with crude oil, and, therefore, absorbed a number of lighter molecules from the crude oil. 
     When a well bore is drilled into the earth and pierces one or more of such hydrocarbon bearing formations, natural gas and/or crude oil can be recovered through that well bore to the earth&#39;s surface. 
     The terms “whole crude oil” and “crude oil” as used herein mean liquid (at normally prevailing conditions of temperature and pressure at the earth&#39;s surface) crude oil as it issues from a wellhead separate from any natural gas that may be present, and excepting any treatment such crude oil may receive to render it acceptable for transport to a crude oil refinery and/or conventional distillation in such a refinery. This treatment would include such steps as desalting. Thus, it is crude oil that is suitable for distillation or other fractionation in a refinery, but which has not undergone any such distillation or fractionation. It could include, but does not necessarily always include, non-boiling entities such as asphaltenes or tar. As such, it is difficult if not impossible to provide a boiling range for whole crude oil. Accordingly, whole crude oil could be one or more crude oils straight from an oil field pipeline and/or conventional crude oil storage facility, as availability dictates, without any prior fractionation thereof. 
     Natural gas, like crude oil, can vary widely in its composition as produced to the earth&#39;s surface, but generally contains a significant amount, most often a major amount, i.e., greater than about 50 weight percent (wt. %), methane. Natural gas often also carries minor amounts (less than about 50 wt. %), often less than about 20 wt. %, of one or more of ethane, propane, butane, nitrogen, carbon dioxide, hydrogen sulfide, and the like. Many, but not all, natural gas streams as produced from the earth can contain minor amounts (less than about 50 wt. %), often less than about 20 wt. %, of hydrocarbons having from 5 to 12, inclusive, carbon atoms per molecule (C5 to C12) that are not normally gaseous at generally prevailing ambient atmospheric conditions of temperature and pressure at the earth&#39;s surface, and that can condense out of the natural gas once it is produced to the earth&#39;s surface. All wt. % are based on the total weight of the natural gas stream in question. 
     When various natural gas streams are produced to the earth&#39;s surface, a hydrocarbon composition often naturally condenses out of the thus produced natural gas stream under the then prevailing conditions of temperature and pressure at the earth&#39;s surface where that stream is collected. There is thus produced a normally liquid hydrocarbonaceous condensate separate from the normally gaseous natural gas under the same prevailing conditions. The normally gaseous natural gas can contain methane, ethane, propane, and butane. The normally liquid hydrocarbon fraction that condenses from the produced natural gas stream is generally referred to as “condensate,” and generally contains molecules heavier than butane (C5 to about C20 or slightly higher). After separation from the produced natural gas, this liquid condensate fraction is processed separately from the remaining gaseous fraction that is normally referred to as natural gas. 
     Thus, condensate recovered from a natural gas stream as first produced to the earth&#39;s surface is not the exact same material, composition wise, as natural gas (primarily methane). Neither is it the same material, composition wise, as crude oil. Condensate occupies a niche between normally gaseous natural gas and normally liquid whole crude oil. Condensate contains hydrocarbons heavier than normally gaseous natural gas, and a range of hydrocarbons that are at the lightest end of whole crude oil. 
     Condensate, unlike crude oil, can be characterized by way of its boiling point range. Condensates normally boil in the range of from about 100 to about 650 F. With this boiling range, condensates contain a wide variety of hydrocarbonaceous materials. These materials can include compounds that make up fractions that are commonly referred to as naphtha, kerosene, diesel fuel(s), and gas oil (fuel oil, furnace oil, heating oil, and the like). Naphtha and associated lighter boiling materials (naphtha) are in the C5 to C10, inclusive, range, and are the lightest boiling range fractions in condensate, boiling in the range of from about 100 to about 400 F. Petroleum middle distillates (kerosene, diesel, atmospheric gas oil) are generally in the C10 to about C20 or slightly higher range, and generally boil, in their majority, in the range of from about 350 to about 650 F. They are, individually and collectively, referred to herein as “distillate” or “distillates.” It should be noted that various distillate compositions can have a boiling point lower than 350 F and/or higher than 650 F, and such distillates are included in the 350-650 F range aforesaid, and in this invention. 
     The starting feedstock for a conventional olefin production plant, as described above, has first been subjected to substantial, expensive processing before it reaches that plant. Normally, condensate and whole crude oil is distilled or otherwise fractionated in a crude oil refinery into a plurality of fractions such as gasoline, naphtha, kerosene, gas oil (vacuum or atmospheric) and the like, including, in the case of crude oil and not natural gas, a high boiling residuum. Thereafter any of these fractions, other than the residuum, are normally passed to an olefin production plant as the starting feedstock for that plant. 
     It would be desirable to be able to forego the capital and operating cost of a refinery distillation unit (whole crude processing unit) that processes condensate and/or crude oil to generate a hydrocarbonaceous fraction that serves as the starting feedstock for conventional olefin producing plants. However, the prior art, until recently, taught away from even hydrocarbon cuts (fractions) that have too broad a boiling range distribution. For example, see U.S. Pat. No. 5,817,226 to Lenglet. 
     Recently, U.S. Pat. No. 6,743,961 (hereafter “USP &#39;961” issued to Donald H. Powers. This patent relates to cracking whole crude oil by employing a vaporization/mild cracking zone (unit) that contains packing. This zone is operated in a manner such that the liquid phase of the whole crude that has not already been vaporized is held in that zone until cracking/vaporization of the more tenacious hydrocarbon liquid components is maximized. This allows only a minimum of solid residue formation which residue remains behind as a deposit on the packing. This residue is later burned off the packing by conventional steam air decoking, ideally during the normal furnace decoking cycle, see column 7, lines 50-58 of that patent. Thus, the second zone 9 of that patent serves as a trap for components, including hydrocarbonaceous materials, of the crude oil feed that cannot be cracked or vaporized under the conditions employed in the process, see column 8, lines 60-64 of that patent. 
     Still more recently, U.S. Pat. No. 7,019,187 issued to Donald H. Powers. This patent is directed to the process disclosed in USP &#39;961, but employs a mildly acidic cracking catalyst to drive the overall function of the vaporization/mild cracking unit more toward the mild cracking end of the vaporization (without prior mild cracking)—mild cracking (followed by vaporization) spectrum. 
     The disclosures of the foregoing patents, in their entirety, are incorporated herein by reference. 
     One skilled in the art would first subject the feed to be cracked to a conventional distillation column to distill the distillate from the cracking feed. This approach would require a substantial amount of capital to build the column and outfit it with the normal reboiler and overhead condensation equipment that goes with such a column. In this invention, a vaporization unit (splitter or stripper) is employed in a manner such that much greater energy efficiency at lower capital cost is realized over a distillation column. By use of this vaporization unit, reboilers, overhead condensers, and related distillation column equipment are eliminated without eliminating the functions thereof, thus saving considerably in capital costs. Further, this invention exhibits much greater energy efficiency in operation than a distillation column because the extra energy that would be required by a distillation column is not required by this invention since this invention instead utilizes for its splitting function the energy that is already going to be expended in the operation of the cracking furnace (as opposed to energy expended to operate a standalone distillation column upstream of the cracking furnace), and the vapor product of the stripper goes directly to the cracking section of the furnace. 
     This invention employs a unique partitioned vaporization unit (zone) that can produce a side draw stream that is low, if not essentially free, of asphaltenes, tars, and/or solids that can be associated with the feed material that is routinely fed to that unit. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, there is provided a process for utilizing whole crude oil and/or natural gas condensate as the feedstock for an olefin plant, as defined above, in combination with a partitioned vaporization unit. 
    
    
     
       DESCRIPTION OF THE DRAWING 
         FIG. 1  shows a simplified flow sheet for a prior art process for thermally cracking whole crude oil/natural gas condensate using a vaporization unit that is not partitioned in the manner of this invention. 
         FIG. 2  shows a whole crude oil/condensate vaporization unit that has a lower chamber thereof partitioned in the manner of this invention. 
         FIG. 3  shows a cross-section of the partitioned chamber of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The terms “hydrocarbon,” “hydrocarbons,” and “hydrocarbonaceous” as used herein do not mean materials strictly or only containing hydrogen atoms and carbon atoms. Such terms include materials that are hydrocarbonaceous in nature in that they primarily or essentially are composed of hydrogen and carbon atoms, but can contain other elements such as oxygen, sulfur, nitrogen, metals, inorganic salts, and the like, even in significant amounts. 
     An olefin producing plant useful with this invention would include a pyrolysis (thermal cracking) furnace for initially receiving and cracking the feed. Pyrolysis furnaces for steam cracking of hydrocarbons heat by means of convection and radiation, and comprise a series of preheating, circulation, and cracking tubes, usually bundles of such tubes, for preheating, transporting, and cracking the hydrocarbon feed. The high cracking heat is supplied by burners disposed in the radiant section (sometimes called “radiation section”) of the furnace. The waste gas from these burners is circulated through the convection section of the furnace to provide the heat necessary for preheating the incoming hydrocarbon feed. The convection and radiant sections of the furnace are joined at the “cross-over,” and the tubes referred to hereinabove carry the hydrocarbon feed from the interior of one section to the interior of the next. 
     Cracking furnaces are designed for rapid heating in the radiant section starting at the radiant tube (coil) inlet where reaction velocity constants are low because of low temperature. Most of the heat transferred simply raises the hydrocarbons from the inlet temperature to the reaction temperature. In the middle of the coil, the rate of temperature rise is lower but the cracking rates are appreciable. At the coil outlet, the rate of temperature rise increases somewhat but not as rapidly as at the inlet. 
     Steam dilution of the feed hydrocarbon lowers the hydrocarbon partial pressure, enhances olefin formation, and reduces any tendency toward coke formation in the radiant tubes. 
     Radiant coils in the furnace heat the hydrocarbons to from about 1,450° F. to about 1,550° F. and thereby subject the hydrocarbons to severe cracking. 
     Hydrocarbon feed to the furnace is preheated to from about 900° F. to about 1,000° F. in the convection section by convectional heating from the flue gas from the radiant section, steam dilution of the feed in the convection section, or the like. After preheating in a conventional commercial furnace, the feed is ready for entry into the radiant section. 
     The cracked gaseous hydrocarbons leaving the radiant section are rapidly reduced in temperature to prevent destruction of the cracking pattern. Cooling of the cracked gases before further processing of same downstream in the olefin production plant recovers a large amount of energy as high pressure steam for re-use in the furnace and/or olefin plant. This is often accomplished with the use of transfer-line exchangers that are well known in the art. 
     Downstream processing of the cracked hydrocarbons issuing from the furnace varies considerably, and particularly based on whether the initial hydrocarbon feed was a gas or a liquid. Since this invention uses whole crude oil and/or liquid natural gas condensate as a feed, downstream processing herein will be described for a liquid fed olefin plant. Downstream processing of cracked gaseous hydrocarbons from liquid feedstock, naphtha through gas oil for the prior art, and crude oil and/or condensate for this invention, is more complex than for gaseous feedstock because of the heavier hydrocarbon components present in the liquid feedstocks. 
     With a liquid hydrocarbon feedstock downstream processing, although it can vary from plant to plant, typically employs termination of the cracking function by a transfer-line exchanger followed by oil and water quenches of the furnace effluent. Thereafter, the cracked hydrocarbon stream is subjected to fractionation to remove heavy liquids, followed by compression of uncondensed hydrocarbons, and acid gas and water removal therefrom. Various desired products are then individually separated, e.g., ethylene, propylene, a mixture of hydrocarbons having four carbon atoms per molecule, fuel oil, pyrolysis gasoline, and a high purity hydrogen stream. 
     In accordance with this invention, a process is provided which utilizes crude oil and/or condensate liquid that has not been subjected to fractionation, distillation, and the like, as the primary (initial) feedstock for the olefin plant pyrolysis furnace in whole or in substantial part. By so doing, this invention eliminates the need for costly distillation of the condensate into various fractions, e.g., from naphtha, kerosene, gas oil, and the like, to serve as the primary feedstock for a pyrolysis furnace as is done by the prior art as first described hereinabove. 
     This invention can be carried out using, for example, the apparatus disclosed in USP &#39;961 when modified in accordance with the teachings of this invention. Thus, this invention is carried out using a self-contained vaporization facility that operates separately from and independently of the convection and radiant sections of the furnace. When employed outside the furnace, crude oil and/or condensate primary feed is preheated in the convection section of the furnace, passed out of the convection section and the furnace to a standalone vaporization facility. The vaporous hydrocarbon product of this standalone facility is then passed back into the furnace to enter the radiant section thereof. Preheating can be carried out other than in the convection section of the furnace if desired or in any combination inside and/or outside the furnace and still be within the scope of this invention. 
     The vaporization unit of this invention receives the condensate feed that may or may not have been preheated, for example, from about ambient to about 350 F, preferably from about 200 to about 350 F. This is a lower temperature range than what is required for complete vaporization of the feed. Any preheating preferably, though not necessarily, takes place in the convection section of the same furnace for which such condensate is the primary feed. 
     Thus, a first chamber in the vaporization operation step of this invention (zone 4 in USP &#39;961) employs vapor/liquid separation wherein vaporous hydrocarbons and other gases, if any, in the preheated feed stream are separated from those distillate components that remain liquid after preheating. Gases can also be formed in this chamber. The aforesaid gases are removed from the vapor/liquid separation section and passed on to the radiant section of the furnace. 
     Vapor/liquid separation in this first, e.g., upper, chamber knocks out distillate liquid in any conventional manner, numerous ways and means of which are well known and obvious in the art. 
     Liquid thus separated from the aforesaid vapors moves into a second, e.g., lower, chamber (zone 9 in USP &#39;961). This can be accomplished by external piping. Alternatively this can be accomplished internally of the vaporization unit. The liquid entering and traveling along the length of this second chamber meets oncoming, e.g., rising, steam. This liquid, absent the gases removed by way of the first chamber, receives the full impact of the oncoming steam&#39;s thermal energy and diluting effect. 
     This second chamber can carry at least one liquid distribution device such as a perforated plate(s), trough distributor, dual flow tray(s), chimney tray(s), spray nozzle(s), and the like. 
     This second chamber can also carry in a portion thereof one or more conventional tower packing materials and/or trays for promoting intimate mixing of liquid and vapor in the second zone. 
     As the remaining liquid hydrocarbon travels (falls) through this second chamber, lighter materials such as gasoline or naphtha that may be present can be vaporized in substantial part by the high energy steam with which it comes into contact. This enables the hydrocarbon components that are more difficult to vaporize to continue to fall and be subjected to higher and higher steam to liquid hydrocarbon ratios and temperatures to enable them to be vaporized by both the energy of the steam and the decreased liquid hydrocarbon partial pressure with increased steam partial pressure. 
       FIG. 1  shows one embodiment of the process just described in diagrammatic form for sake of simplicity and brevity. 
       FIG. 1  shows a conventional cracking furnace  1  wherein a crude oil and/or condensate primary feed  2  is passed in to the preheat section  3  of the convection section of furnace  1 . Steam  6  is also superheated in this section of the furnace for use in the process of this invention. 
     The pre-heated cracking feed is then passed by way of pipe (line)  10  to the aforesaid vaporization unit  11 , which unit is separated into an upper vaporization chamber  12  and a lower chamber  13 . This unit  11  achieves primarily (predominately) vaporization with or without mild cracking of at least a significant portion of the naphtha and gasoline boiling range and lighter materials that remain in the liquid state after the pre-heating step. Gaseous materials that are associated with the preheated feed as received by unit  11 , and additional gaseous materials formed in zone  12 , are removed from  12  by way of line  14 . Thus, line  14  carries away essentially all the lighter hydrocarbon vapors, e.g., naphtha and gasoline boiling range and lighter, that are present and/or formed in chamber  12 . Liquid distillate present in  12 , with or without some liquid gasoline and/or naphtha, is removed there from via line  15  and passed into the upper interior of lower chamber  13 . Chambers  12  and  13 , in this embodiment, are separated from fluid communication with one another by an impermeable wall  16 , which can be a solid tray. Line  15  represents external fluid down flow communication between chambers  12  and  13 . In lieu thereof, or in addition thereto, chambers  12  and  13  can have internal fluid communication there between by modifying wall  16  to be at least in part liquid permeable by use of one or more trays designed to allow liquid to pass down into the interior of  13  and vapor up into the interior of  12 . For example, instead of an impermeable wall  16 , a chimney tray could be used in which case vapor carried by line  17  would pass internally within unit  11  down into section  13  instead of externally of unit  11  via line  15 . In this internal down flow case, distributor  18  becomes optional. 
     By whatever way liquid is removed from  12  to  13 , that liquid moves downwardly into the interior of  13 , and thus can encounter at least one liquid distribution device  18 . Device  18  evenly distributes liquid across the transverse cross section of unit  11  so that the liquid will flow uniformly across the width of the tower into contact with packing  19 . 
     Dilution steam  6  passes through superheat zone  20 , and then, via line  21  into a lower portion  22  of chamber  13  below packing  19 . In packing  19  liquid and steam from line  21  intimately mix with one another thus vaporizing some of liquid  15 . This newly formed vapor, along with dilution steam  21 , is removed from  13  via line  17  and added to the vapor in line  14  to form a combined hydrocarbon vapor product in line  25 . Stream  25  can contain essentially hydrocarbon vapor from feed  2 , e.g., gasoline and naphtha, and steam. 
     Stream  17  thus represents a part of feed stream  2  plus dilution steam  21  less liquid distillate(s) and heavier from feed  2  that are present in bottoms stream  44 . Stream  25  is passed through a mixed feed preheat zone  27  in a hotter (lower) section of the convection zone of furnace  1  to further increase the temperature of all materials present, and then via cross over line  28  into the radiant coils (tubes)  29  in the radiant firebox of furnace  1 . Line  28  can be internal or external of furnace cross over conduit  30 . Line  44  removes from stripper  11  the residuum, if any, from feed  2 . 
     Steam  6  can be employed entirely in chamber  13 , or a part thereof can be employed in either line  14  and/or line  25  to aid in the prevention of the formation of liquid in lines  14  or  25 . 
     In the radiant firebox section  22  of furnace  1 , feed from line  28  which contains numerous varying hydrocarbon components is subjected to severe thermal cracking conditions in coils  29  as aforesaid. 
     The cracked product leaves the radiant fire box section of furnace  1  by way of line  31  for further processing in the remainder of the olefin plant downstream of furnace  1  as shown in USP &#39;961. 
     In a conventional olefin production plant, the preheated feed  10  would be mixed with dilution steam  21 , and this mixture would then be passed directly from preheat zone  3  into the radiant section  22  of furnace  1 , and subjected to severe thermal cracking conditions. In contrast, this invention instead passes the preheated feed at, for example, a temperature of from about 200 to about 350 F, into standalone portioned unit  11  (see  FIG. 2 ) which is physically located outside of furnace  1 . 
     In the embodiment of  FIG. 1 , cracked furnace product  31  is passed to at least one transfer line exchanger (TLE)  32  wherein it is cooled sufficiently to terminate the thermal cracking function. The cracked gas product is removed by way of line  33  and can be further cooled by injection of recycled quench oil  34  immediately downstream of TLE  32 . The quench oil in streams  34  and  45  is a complex mixture of C12 and heavier hydrocarbons boiling in the range of from about 380 to about 700 F, and is often referred to as pyrolysis fuel oil or pyrolysis gas oil. Normally, pyrolysis fuel (gas) oil that is not recycled by way of line  34  is separated from the process by way of line  45 , and used and/or sold as fuel oil, but can also be used in this invention as described here in after. The quench oil/cracked gas mixture passes via line  33  to oil quench tower  35 . In tower  35  this mixture is contacted with a lighter boiling hydrocarbonaceous liquid quench material such as pyrolysis gasoline which contains primarily C5 to C12 hydrocarbons and boils in the range of from about 100 to about 420 F. Pyrolysis gasoline is provided by way of line  36  to further cool the cracked gas furnace product as well as condense and recover additional fuel oil product by way of lines  34  and  45 . Cracked gas product is removed from tower  35  via line  37  and passed to water quench tower  38  wherein it is contacted with recycled and cooled water  39  that is recovered from a lower portion of tower  38 . Water  39  condenses liquid pyrolysis gasoline in tower  38  which is, in part, employed as liquid quench material  36 , and, in part, removed via line  40  for other processing elsewhere. 
     A lighter side draw stream  53  can be taken from unit  35  intermediate overhead  37  and bottoms streams  34 / 45  which stream  53  is composed essentially of pyrolysis gas oil boiling in the range of from about 380 to about 700 F. Stream  53  is also useful in this invention as described hereinafter. 
     The thus processed cracked gas product is removed from tower  38  via line  41  and passed to compression and fractionation facility  42  wherein individual product streams aforesaid are recovered as products of the cracking plant, such individual product streams being collectively represented by way of line  43 . 
     Feed  2  can enter furnace  1  at a temperature of from about ambient up to about 300 F at a pressure from slightly above atmospheric up to about 100 psig (hereafter “atmospheric to 100 psig”). Feed  2  can enter zone  12  via line  10  at a temperature of from about ambient to about 500 F at a pressure of from atmospheric to 100 psig. 
     Stream  14  can be essentially all hydrocarbon vapor formed from feed  2  and is at a temperature of from about 500 to about 750 F at a pressure of from atmospheric to 100 psig. 
     Stream  15  can be essentially all the remaining liquid from feed  2  less that which was vaporized in pre-heater  3  and is at a temperature of from about 500 to about 750 F at a pressure of from atmospheric to 100 psig. 
     The combination of streams  14  and  17 , as represented by stream  25 , can be at a temperature of from about 650 to about 800 F at a pressure of from atmospheric to 100 psig, and contain, for example, an overall steam/hydrocarbon ratio of from about 0.1 to about 2. 
     Stream  28  can be at a temperature of from about 900 to about 1,100 F at a pressure of from atmospheric to 100 psig. 
     In chamber  13 , dilution ratios (hot gas/liquid droplets) will vary widely because the composition of condensate varies widely. Generally, the hot gas  21 , e.g., steam, to hydrocarbon ratio at the top of  13  can be from about 0.1/1 to about 5/1, preferably from about 0.1/1 to about 1.2/1, more preferably from about 0.1/1 to about 1/1. 
     Steam is an example of a suitable hot gas introduced by way of line  21 . Other materials can be present in the steam employed. Stream  6  can be composed of that type of steam normally used in a conventional cracking plant. Such gases are preferably at a temperature sufficient to volatilize a substantial fraction of the liquid hydrocarbon  15  that enters chamber  13 . Generally, the gas entering  13  from conduit  21  will be at least about 350 F, preferably from about 650 to about 1,000 F at from atmospheric to 100 psig. Stream  17  can be a mixture of steam and hydrocarbon vapor that has a boiling point lower than about 350 F. It should be noted that there may be situations where the operator desires to allow some distillate to enter stream  17 , and such situations are within the scope of this invention. Stream  17  can be at a temperature of from about 600 to about 800 F at a pressure of from atmospheric to 100 psig. 
     It can be seen that steam from line  21  does not serve just as a diluent for partial pressure purposes as does diluent steam that may be introduced, for example, into conduit  2  (not shown). Rather, steam from line  21  provides not only a diluting function, but also additional vaporizing energy for the hydrocarbons that remain in the liquid state. This is accomplished with just sufficient energy to achieve vaporization of heavier hydrocarbon components and by controlling the energy input. For example, by using steam in line  21 , substantial vaporization of feed  2  liquid is achieved. The very high steam dilution ratio and the highest temperature steam are thereby provided where they are needed most as liquid hydrocarbon droplets move progressively lower in  13 . 
     Note that chamber  13  of prior art  FIG. 1  contains transversely extending packing bed  19  and unitary distributor  18 , so that the flow of liquid remainder  15  at the inlet (upper) end of  13  above distributor  18  is deliberately spread uniformly across the full transverse cross-section of  13  from the top to the bottom of that chamber. In this regard chamber  13  is not partitioned as to fluid flow transversely across its interior volume. That is to say, chamber  13  is not partitioned or otherwise channeled in regards to the transverse cross-sectional flow of fluid across the interior of chamber  13 , and this is so from its upper inlet at  15  to its lower outlet at  44 . 
       FIG. 2  shows vaporization unit  11  without individual distributor  18  of  FIG. 1  and modified pursuant to this invention so that lower chamber  13  that receives remaining liquid  15  from upper chamber  12  is physically vertically partitioned (divided) by an upstanding, fluid impervious wall  60  that is disposed within the inner volume of chamber  13  to form first and second volumes (sides)  51  and  52  that are each filled with packing like packing  19  of  FIG. 1 . Note that the combination of the packing filling volumes  51  and  52  together with partition  60  forms a structure that extends fully across the entire transverse cross-section of chamber  13 , and leaves no large vertical passages or unobstructed conduit paths through this structure. Thus, liquid flowing downwardly from top to bottom in chamber  13  must pass through either packing  51  or packing  52 , and at no transverse location across chamber  13  allowed to flow freely from the top to bottom without having to pass through a packing bed. 
     Partition  60  extends above the top of the packing at  54  to keep incoming remaining liquid  56  from line  15  on side  51  and out of side  52 . Accordingly, sides  51  and  52  at their upper inlet ends are, by way of wall  60 , physically separated as far as transverse liquid flow is concerned, but yet these inlet ends are in fluid communication as far as vapor movement is concerned so that gas from both sides can rise and be recovered by way of line  17  for transport to furnace  1  ( FIG. 1 ). Similarly, the lower outlet ends of sides  51  and  52  that are nearer bottom  67  of unit  11  are physically separated as to liquid flow there between while still open at these outlet ends for the transfer of vapor there between as shown by arrow  62 . Each of sides  51  and  52  can, if desired, carry an individual distributor (not shown) like unitary distributor  18 . The individual distributors in each of sides  51  and  52  will be carried in an upper portion of those sides, and on opposite sides of partition  60 . 
     Side  51  has no floor thereto, while side  52  has a vapor pervious floor  61  which can be, for example, a valved tray, and the like, which is well known in the art. Floor  61  thus catches liquid and directs it into sump  63  from which it is withdrawn by way of line  64 , while still allowing any vapor  62  to pass upwardly through both floor  61  (as shown by arrow  70 ) and side  52  towards outlet line  17 . Note that floor  61  can be located above the lower outlet level of side  51  for better liquid separation without impeding vapor transfer between sides  51  and  52 . 
     Pursuant to this invention, the process within chamber  13  is broken down into two distinct steps. The first step is the passage of remaining liquid  15  downwardly through side  51  while keeping such liquid out of side  52 . The second step is the introduction by way of line  50  into the upper inlet end of side  52  of a pyrolysis fuel oil type stream, and keeping this liquid out of side  51 . Note that these two steps are carried out while the upper inlet ends (receiving streams  56  and  59 ) and the lower outlet ends of sides  51  and  52  are in open vapor communication with one another, for example at  62 , while the separation of liquid streams  56  and  59  is maintained. 
     The quench oil bottoms stream  45  from prior art unit  35  of  FIG. 1  can be passed, in whole or in part, into quench oil stream  65  in unit  11  of  FIG. 2  of this invention. Lighter side draw pyrolysis gas oil stream  53  from prior art unit  35  of  FIG. 1  can be passed, in whole or in part, into stream  50  in unit  11  of  FIG. 2  of this invention. 
     Thus, in the primary mode of operation for this invention remaining liquid  15  will be processed essentially exclusively in side  51 , while liquid pyrolysis fuel (gas) oil will be processed at the same time essentially exclusively in side  52 , vapors at both the inlet and outlet ends of sides  51  and  52  being free to intermingle with one another. This separate two step operation within the same chamber  13  of unit  11  not only provides two streams  14  and  17  that are well suited for cracking in furnace  1  of  FIG. 1 , but, in addition, provides the flexibility of recovering a third stream  64  from sump  63 . 
     Side draw stream  64  is a hydrocarbonaceous stream that is essentially free of asphaltenes, coke, and other solids that can be present in feed  10 , and, therefore, is suitable for processes other than thermal cracking which cannot tolerate the presence of such solids, e.g., hydrocracking catalyst. For example, stream  64  not only is suitable for thermal cracking if desired, but, due to its lack of asphaltenes, coke, and other solids, can also be used as feed for conversion processes, refinery hydrocracking operations for upgrading to olefins plant feed or to a low sulfur gasoline blending component, hydrotreating, and the like. This is not the case for solids containing residual liquid removed from unit  11  by way of bottoms outlet  71 . 
     Accordingly, stream  64  can vary widely in its hydrocarbon composition, but will generally primarily contain C5 to C20 hydrocarbons having a boiling range of from about 100 to about 700 F. 
     The process of this invention, by using a divided chamber in vaporization unit  11  is quite flexible. For example, if the operator desires, for any one of a number of reasons, he can pass a small but effective amount of remaining liquid  15  to the upper inlet end of side  52  as shown by arrow  57 , and/or pass a small but effective amount of pyrolysis fuel (gas) oil to the upper inlet end of side  51  as shown by arrow  58 . For example, stream  50  can be upgraded by way of processing in side  52  with its light ends going to furnace  1  by way of line  17 , and its heavy aromatic end being fed to a hydrocracker by way of line  64 . Such steps are optional, but, nevertheless available if the operator deems either or both of them to be worthwhile from an operational point of view. 
     Another option available to the operator is to recycle some of the high value, solids clean product  64  back to the inlet end of side  51  and/or side  52  as shown by arrows  66 ,  58 , and  59 . Loop line  66  can be provided with cooling capacity (not shown) if desired. Using solids clean product  64  in recycle loop  66  can improve vapor and liquid contacting inside chamber  13 . 
     Yet another option is the introduction in a lower portion of chamber  13  below the outlets of sides  51  and  52  of a quench oil stream  65 . This stream can be quench oil from line  45  of  FIG. 1 . 
       FIG. 3  shows a transverse cross-section through chamber  13  (see  FIG. 1 ). The packing beds are not shown for sake of clarity in viewing bottom  67  and floor  61 .  FIG. 3  shows partition  60  to extend fully across the transverse cross-section of the interior of chamber  13 , thereby forming a vertical liquid barrier between sides  51  and  52 . 
     Example 
     A natural gas condensate stream  5  characterized as Oso condensate from Nigeria is removed from a storage tank and fed directly into the convection section of a pyrolysis furnace  1  at ambient conditions of temperature and pressure. In this convection section, this condensate initial feed is preheated to about 350 F at about 60 psig, and then passed into a vaporization unit  11  wherein a mixture of gasoline and naphtha gases at about 350 F and 60 psig are separated from distillate liquids in chamber  12  of that unit. The separated gases are removed from chamber  12  for transfer to the radiant section of the same furnace for severe cracking in a temperature range of 1,450° F. to 1,550° F. at the outlet of radiant coil  29 . 
     The hydrocarbon liquid remaining from feed  2 , after separation from accompanying hydrocarbon gases aforesaid, is transferred to lower chamber  13  and allowed to fall downwardly in that section toward the bottom thereof on side  51  of wall  60 . At the same time pyrolysis fuel (gas) oil from oil quench tower  35  is introduced into chamber  13  by way of line  50  at a temperature of about 450 F and about 10 psig. 
     Preheated steam  21  at about 1,000 F is introduced near the bottom of chamber  13  to give a steam to hydrocarbon ratio in section  22  of about 0.5. The falling liquid droplets are in counter current flow with the steam that is rising from the bottom of chamber  13  toward the top thereof through both sides  51  and  52 . With respect to the liquid falling downwardly in sides  51  and  52 , the steam to liquid hydrocarbon ratio increases from the top to bottom of those sides. 
     A mixture of steam and naphtha vapor  17  at about 340 F is withdrawn from near the top of chamber  13  and mixed with the gases earlier removed from chamber  12  via line  14  to form a composite steam/hydrocarbon vapor stream  25  containing about 0.5 pounds of steam per pound of hydrocarbon present. This composite stream is preheated in zone  27  to about 1,000 F at less than about 50 psig, and introduced into the radiant firebox section of furnace  1 . 
     A pyrolysis hydrocarbon side draw is recovered in line  64  at a temperature of about 400 F. This stream is essentially free of asphaltenes, coke, and other solids. 
     Bottoms product  71  of unit  11  is removed at a temperature of about 460 F, and pressure of about 60 psig. This stream contains essentially all of the asphaltense, coke, and other solids originally present in feed stream  10 .