TREATING A TEMPERATURE-SENSITIVE HYDROCARBONACEAOUS STREAM

Abstract: A temperature-sensitive hydrocarbonaceous stream containing a non-distillable component is treated to produce a hydrogenated distillable hydrocarbonaceous product while minimizing thermal degradation of the hydrocarbonaceous stream by: (a) contacting the hydrocarbonaceous stream with a first hot hydrogen-rich gaseous stream at conditions effective to provide a hydrocarbonaceous vapor stream comprising hydrogen and a heavy stream comprising the non-­ distillable component; (b) contacting the vapor stream with a hydrogenation catalyst in a reaction zone at hydrogenation conditions selected to increase the hydrogen content of the hydrocarbonaceous compounds contained therein; (c) condensing the resulting effluent from the reaction zone to provide a second hydrogen-rich gaseous stream and a liquid stream; (d) reacting at least a portion of the heavy stream from step (a) in a thermal coking zone at thermal coking conditions to provide a thermal coking zone effluent stream; and, (e) recovering the hydrogenated distillable hydrocarbonaceous product stream from the liquid stream from step (c) and from the effluent stream from step (d).

Description: The field of art to which this invention pertains is the production of a hydrogenated distillable hydrocarbonaceous product from a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component. More specifically, the invention relates to a multi-step process for treating a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component to produce a hydrogenated distillable hydrocarbonaceous product while minimizing thermal degradation of the hydrocarbonaceous stream. In US-A-3992285, a process is disclosed for the desulfurization of a hydrocarbonaceous black oil containing sulfur and asphaltic material which comprises preheating the oil by indirect heat exchange to a temperature not in excess of 288°C (550°F), commingling the preheated oil with a steam-containing gas to raise the temperature of the oil to a desulfurization temperature of 316 to 427°C (600 to 800°F) and contacting the thus heated oil at hydrocarbon conversion conditions with a desulfurization catalyst. US-A-3027317 describes a hydrorefining process for treating heavy oils intended to avoid the deposition of coke and other deactivating deposits on the hydrorefining catalyst. The feed oil is first subjected to a combined partial vaporization-deasphalting step in the presence of the hydrogen-containing recycle gas from the hydrorefiner, and at substantially the pressure prevailing in the hydrorefiner. The asphaltic residue from the partial vaporisation step is then subjected to a thermal coking step to produce further quantities of asphalt-free oil in the form of a coker distillate, the asphaltic bodies being decomposed largely to coke. At least the light portion of the coker distillate is then combined with the gaseous mixture derived from the vaporisation step, and the combined product is subjected to hydrorefining. The heavy ends of the coker distillate may be recycled to the partial vaporization step to further reduce deposit-forming bodies in the oil. In US-A-3027317, the initial vaporisation can be carried out in either or both of two ways. All or a part of the feed can be distilled to provide a light asphalt-free fraction, which can be fed directly to a hydrorefiner, and a heavy fraction that can be fed to a coking zone. Alternatively, all or part of the feed can be combined with recycled gas from the hydrorefiner, heated by indirect heat exchange, to a temperature within 55.5°C (100°F) of that in the hydrorefiner, and separated into light and heavy fractions in a centrifugal separator. The light fraction is passed to the hydrorefiner, and the heavy fraction is passed to the coking zone. The present invention provides a process for treating a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component to produce a hydrogenated distillable hydrocarbonaceous product which comprises the steps of: (a) vaporizing at least a portion of said hydrocarbonaceous stream to provide a hydrocarbonaceous vapour stream comprising hydrogen and a heavy stream comprising said non-distillable component; (b) reacting said hydrocarbonaceous vapour stream with hydrogen in the presence of a hydrogenation catalyst in a hydrogenation reaction zone; (c) condensing at least a portion of the resulting effluent from said hydrogenation reaction zone to provide a hydrogen-rich gaseous stream and a liquid stream comprising hydrogenated distillable hydrocarbonaceous compounds; (d) thermally coking at least a portion of said heavy stream in a thermal coking zone to provide a thermal coking zone effluent; and, (e) thereafter recovering a hydrogenated distillable hydrocarbonaceous product stream from said liquid stream from step (d). The distinguishing feature of the invention is that said hydrocarbonaceous stream is vaporised in step (a) by direct contact in a flash zone with said hydrogen-rich gaseous stream having a temperature greater than that of the hydrocarbonaceous stream, the temperature of the hydrocarbonaceous stream being less than 482°F (250°C), and the temperature of the hydrogen-rich gaseous stream being from 200 to 1200°F (93 to 649°C). Important elements of the improved process are the relatively short time that the feed stream is maintained at elevated temperature, the avoidance of heating the feed stream via indirect heat exchange to preclude the coke formation that could otherwise occur and the minimization of utility costs due to the integration of the hydrogenation zone. Another embodiment of the invention may be characterized as a process for treating a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component to produce a hydrogenated distillable hydrocarbonaceous product while minimizing thermal degradation of the hydrocarbonaceous stream which process comprises the steps of: (a) contacting the hydrocarbonaceous stream with a first hydrogen-rich gaseous stream having a temperature greater than the hydrocarbonaceous stream in a flash zone at flash conditions thereby increasing the temperature of the hydrocarbonaceous stream and vaporizing at least a portion thereof to provide a hydrocarbonaceous vapor stream comprising hydrogen and a heavy stream comprising the non-distillable component; (b) contacting the hydrocarbonaceous vapor stream comprising hydrogen with a hydrogenation catalyst in a hydrogenation reaction zone at hydrogenation conditions to increase the hydrogen content of the hydrocarbonaceous compounds contained in the hydrocarbonaceous vapor stream; (c) condensing at least a portion of the resulting effluent from the hydrogenation reaction zone to provide a second hydrogen-rich gaseous stream and a liquid stream comprising hydrogenated distillable hydrocarbonaceous compounds; (d) separating the liquid stream comprising hydrogenated distillable hydrocarbonaceous compounds to provide a second hydrocarbonaceous vapor stream comprising normally gaseous hydrocarbons and a normally liquid hydrogenated distillable hydrocarbonaceous product; and (e) reacting at least a portion of the heavy stream comprising the non-distillable component recovered from step (a) in a thermal coking zone at thermal coking conditions to provide a thermal coking zone effluent. Yet another embodiment of the invention may be characterized as a process for treating a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component to produce a hydrogenated distillable hydrocarbonaceous product while minimizing thermal degradation of the hydrocarbonaceous stream which process comprises the steps of: (a) contacting the hydrocarbonaceous stream with a first hydrogen-rich gaseous stream having a temperature greater than the hydrocarbonaceous stream in a flash zone at flash conditions thereby increasing the temperature of the hydrocarbonaceous stream and vaporizing at least a portion thereof to provide a hydrocarbonaceous vapor stream comprising hydrogen and a heavy stream comprising the non-distillable component; (b) contacting the hydrocarbonaceous vapor stream comprising hydrogen with a hydrogenation catalyst in a hydrogenation reaction zone at hydrogenation conditions to simultaneously increase the hydrogen content of the hydrocarbonaceous compounds contained in the hydrocarbonaceous vapor stream and to generate at least one water-soluble inorganic compound produced from the reaction of the hydrocarbonaceous compounds and the hydrogen; (c) contacting the resulting effluent from the hydrogenation zone containing hydrogenated hydrocarbonaceous compounds and at least one water-soluble inorganic compound with an aqueous scrubbing solution; (d) introducing a resulting admixture of the effluent from the hydrogenation zone and the aqueous scrubbing solution into a separation zone to provide a second hydrogen-rich gaseous stream, a liquid stream comprising hydrogenated distillable hydrocarbonaceous compounds and a spent aqueous scrubbing solution containing at least a portion of the water-soluble inorganic compound; (e) separating the liquid stream comprising hydrogenated distillable hydrocarbonaceous compounds to provide a hydrocarbonaceous vapor stream comprising normally gaseous hydrocarbons and a normally liquid hydrogenated distillable hydrocarbonaceous product; and (f) reacting at least a portion of the heavy stream comprising the non-distillable component recovered from step (a) in a thermal coking zone at thermal coking conditions to provide a thermal coking zone effluent. Other embodiments of the present invention encompass further details such as preferred feedstocks, hydrogenation catalysts, aqueous scrubbing solutions and operating conditions, all of which are hereinafter disclosed in the following discussion of each of these facets of the invention. BRIEF DESCRIPTION OF THE DRAWING The drawing is a simplified process flow diagram of a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION There is a steadily increasing demand for technology which is capable of treating a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component to produce a hydrogenated distillable hydrocarbonaceous product and a heavy non-distillable product while minimizing thermal degradation of the hydrocarbonaceous feed stream. Such treatment has always been in demand for the preparation and production of various hydrocarbonaceous products but with the increased environmental emphasis for the treatment and recycle of waste hydrocarbonaceous products there is an increased need for improved processes to separate heavy non-distillable components from a distillable hydrocarbonaceous product which may then be hydrogenated. For example, during the disposal or recycle of potentially environmentally harmful hydrocarbonaceous waste streams, an important step in the total solution to the problem is the pretreatment or conditioning of a hydrocarbonaceous stream which facilitates the ultimate resolution to provide product streams which may subsequently be handled in an environmentally acceptable manner. Therefore, those skilled in the art have sought to find feasible techniques to remove heavy non-distillable components from a temperature-sensitive hydrocarbonaceous stream to provide a distillable hydrocarbonaceous product which may then be hydrogenated. Previous techniques which have been employed include filtration, vacuum wiped film evaporation, centrifugation, and vacuum distillation. The present invention provides an improved integrated process for the removal of heavy non-distillable components from a temperature-sensitive hydrocarbonaceous stream and the subsequent hydrogenation of the distillable hydrocarbonaceous stream. A wide variety of temperature-sensitive hydrocarbonaceous streams are to be candidates for feed streams in accordance with the process of the present invention. Examples of hydrocarbonaceous streams which are suitable for treatment by the process of the present invention are dielectric fluids, hydraulic fluids, heat transfer fluids, used lubricating oil, used cutting oils, used solvents, still bottoms from solvent recycle operations, coal tars, atmospheric residuum, oils contaminated with polychlorinated biphenyls (PCB), halogenated wastes, petrochemical by-products and other hydrocarbonaceous industrial waste. Many of these hydrocarbonaceous streams may contain non-distillable components which include, for example, organometallic compounds, inorganic metallic compounds, finely divided particulate matter and non-distillable hydrocarbonaceous compounds. The present invention is particularly advantageous when the non-distillable components comprise sub-micron particulate matter and the conventional techniques of filtration or centrifugation tend to be highly ineffective. The presence of a non-distillable component including finely divided particulate matter in a hydrocarbonaceous feed to a hydrogenation zone greatly increases the difficulty of the hydrogenation. A non-distillable component tends 1) to foul the hot heat exchange surfaces which are used to heat the feed to hydrogenation conditions, 2) to form coke or in some other manner deactivate the hydrogenation catalyst thereby shortening its active life and 3) to otherwise hinder a smooth and facile hydrogenation operation. Particulate matter in a feed stream tends to deposit within the hydrogenation zone and to plug a fixed hydrogenation catalyst bed thereby abbreviating the time on stream. Once the temperature-sensitive hydrocarbonaceous feed stream is separated into a distillable hydrocarbonaceous stream and a heavy non-distillable product, the resulting distillable hydrocarbonaceous stream is introduced into a hydrogenation zone. If the feed stream contains metallic compounds which contain metals such as zinc, copper, iron, barium, phosphorus, magnesium, aluminum, lead, mercury, cadmium, cobalt, arsenic, vanadium, chromium, and nickel, these compounds will be isolated in the relatively small volume of the recovered non-distillable stream which is recovered from the hot hydrogen flash separator and which is then introduced into a thermal coking zone. In the event that the original temperature-sensitive feed stream contains distillable hydrocarbonaceous compounds which include sulfur, oxygen, nitrogen, metal or halogen components, the resulting recovered distillable hydrocarbonaceous stream is hydrogenated to remove or convert such components as desired. In a preferred embodiment of the present invention, the hydrogenation of the resulting distillable hydrocarbonaceous stream is preferably conducted immediately without intermediate separation or condensation. The advantages of the integrated process of the present invention will be readily apparent to those skilled in the art and include the economy of greatly reduced utility costs. In another preferred embodiment of the present invention, the coking of the heavy stream comprising a non-distillable component is also preferably conducted without intermediate separation or complete cooling in the interest of economy and ultimate conversion to distillable hydrocarbonaceous compounds. The coking reaction in one aspect serves to encase non-volatile particulate matter and potentially leachable hazardous metals in the resulting carbon-rich solid coke thus providing a stable residue for disposal. The quantity of coke is generally significantly less voluminous than the original temperature-sensitive hydrocarbonaceous feedstock or the feed to the coking reaction zone which is advantageous for ultimate disposal. In accordance with the subject invention, a temperature-sensitive hydrocarbonaceous stream containing a non-distillable component is contacted with a hot hydrogen-rich gaseous stream having a temperature greater than the hydrocarbonaceous stream in a flash zone at flash conditions thereby increasing the temperature of the hydrocarbonaceous stream and vaporizing at least a portion thereof to provide a hydrocarbonaceous vapor stream comprising hydrogen and a heavy non-distillable stream. The hot hydrogen-rich gaseous stream preferably comprises more than about 70 mole % hydrogen and more preferably more than about 90 mole % hydrogen. The hot hydrogen-rich gaseous stream is multifunctional and serves as 1) a heat source used to directly heat the hydrocarbonaceous feed stream to preclude the coke formation that could otherwise occur when using an indirect heating apparatus such as a heater or heat-exchanger, 2) a diluent to reduce the partial pressure of the hydrocarbonaceous compounds during vaporization in the flash zone, 3) a possible reactant to minimize the formation of hydrocarbonaceous polymers at elevated temperatures, 4) a stripping medium and 5) at least a portion of the hydrogen required in the hydrogenation reaction zone. In accordance with the subject invention, the temperature-sensitive hydrocarbonaceous feed stream is maintained at a temperature less than about 482°F (250°C) before being introduced into the flash zone in order to prevent or minimize the thermal degradation of the feed stream. Depending upon the characteristics and composition of the hydrocarbonaceous feed stream, the hot hydrogen-rich gaseous stream is introduced into the flash zone at a temperature greater than the hydrocarbonaceous feed stream and at a temperature from about 200°F (93°C) to about 1200°F (649°C). During the contacting, the flash zone is preferably maintained at flash conditions which include a temperature from about 150°F (65°C) to about 860°F (460°C), a pressure from about atmospheric to about 2000 psig (13788 kPa gauge), a hydrogen circulation rate of about 1000 SCFB (168 normal m³/m³) to about 30,000 SCFB (5056 normal m³/m³) based on the temperature-sensitive hydrocarbonaceous feed stream and an average residence time of the hydrogen-containing, hydrocarbonaceous vapor stream in the flash zone from about 0.1 seconds to about 50 seconds. A more preferred average residence time of the hydrogen-containing, hydrocarbonaceous vapor stream in the flash zone is from about 1 second to about 10 seconds. The resulting heavy non-distillable portion of the feed stream is removed from the bottom of the flash zone as required to yield a heavy non-distillable stream. The heavy non-distillable stream may contain a relatively small amount of distillable components but since essentially all of non-distillable components contained in the hydrocarbonaceous feed stream are recovered in this stream, the term "heavy non-distillable stream" is nevertheless used for the convenient description of this stream. The heavy non-distillable stream preferably contains a distillable component of less than about 10 weight percent and more preferably less than about 5 weight percent. Under certain circumstances with a feed stream not having an appreciable amount of liquid non-distillable components, it is contemplated that an additional liquid may be utilized to flush the heavy non-distillables from the flash zone. An example of this situation is when the hydrocarbonaceous feed stream comprises a very high percentage of distillable hydrocarbonaceous compounds and relatively small quantities of finely divided particulate matter (solid) and essentially no liquid non-distillable component for use as a carrier for the solids. Such a flush liquid may, for example, be a high boiling range vacuum gas oil having a boiling range from about 700°F (371°C) to about 1000°F (538°C) or a vacuum tower bottoms stream boiling at a temperature greater than about 1000°F (538°C). The selection of a flush liquid depends upon the composition of the hydrocarbonaceous feed stream and the prevailing flash conditions in the flash separator, and the volume of the flush liquid is preferably limited to that required for removal of the heavy non-distillable component. The resulting hydrogen-containing, hydrocarbonaceous vapor stream is removed from the flash zone and is introduced into a catalytic hydrogenation zone containing hydrogenation catalyst and maintained at hydrogenation conditions. The catalytic hydrogenation zone may contain a fixed, ebullated or fluidized catalyst bed. This reaction zone is preferably maintained under an imposed pressure from about atmospheric (0 kPa gauge) to about 2000 psig (13790 kPa gauge) and more preferably under a pressure from about 100 psig (689.5 kPa gauge) to about 1800 psig (12411 kPa gauge). Suitably, such reaction is conducted with a maximum catalyst bed temperature in the range of about 122°F (50°C) to about 850°F (454°C) selected to perform the desired hydrogenation conversion to reduce or eliminate the undesirable characteristics or components of the hydrocarbonaceous vapor stream. In accordance with the present invention, it is contemplated that the desired hydrogenation conversion includes, for example, dehalogenation, desulfurization, denitrification, olefin saturation, oxygenate conversion and hydrocracking. Further preferred operating conditions include liquid hourly space velocities in the range from about 0.05 hr⁻¹ to about 20 hr⁻¹ and hydrogen circulation rates from about 200 standard cubic feet per barrel (SCFB) (33.71 normal m³/m³) to about 50,000 SCFB (8427 normal m³/m³), preferably from about 300 SCFB (50.6 normal m³/m³) to about 20,000 SCFB (3371 normal m³/m³). In the event that the temperature of the hydrogen-containing, hydrocarbonaceous stream which is removed from the flash zone is not deemed to be exactly the temperature selected to operate the catalytic hydrogenation zone, we contemplate that the temperature of the hydrogen-containing, hydrocarbonaceous stream may be adjusted either upward or downward in order to achieve the desired temperature in the catalytic hydrogenation zone. Such a temperature adjustment may be accomplished, for example, by the addition of either cold or hot hydrogen. The preferred catalytic composite disposed within the hereinabove described hydrogenation zone can be characterized as containing a metallic component having hydrogenation activity, which component is combined with a suitable refractory inorganic oxide carrier material of either synthetic or natural origin. The precise composition and method of manufacturing the carrier material is not considered essential to the present invention. Preferred carrier materials are alumina, silica and mixtures thereof. Suitable metallic components having hydrogenation activity are those selected from the group comprising the metals of Groups VI-B and VIII of the Periodic Table, as set forth in the Periodic Table of the Elements , E.H. Sargent and Company, 1964. Thus, the catalytic composites may comprise one or more metallic components from the group of molybdenum, tungsten, chromium, iron, cobalt, nickel, platinum, palladium, iridium, osmium, rhodium, ruthenium, and mixtures thereof. The concentration of the catalytically active metallic component, or components, is primarily dependent upon a particular metal as well as the physical and/or chemical characteristics of the particular hydrocarbon feedstock. For example, the metallic components of Group VI-B are generally present in an amount within the range of from about 1 to about 20 weight percent, the iron-group metals in an amount within the range of about 0.2 to about 10 weight percent, whereas the noble metals of Group VIII are preferably present in an amount within the range of from about 0.1 to about 5 weight percent, all of which are calculated as if these components existed within the catalytic composite in the elemental state. In addition, any catalyst employed commercially for hydrogenating middle distillate hydrocarbonaceous compounds to remove nitrogen and sulfur may function effectively in the hydrogenation zone of the present invention. It is further contemplated that hydrogenation catalytic composites may comprise one or more of the following components: cesium, francium, lithium, potassium, rubidium, sodium, copper, gold, silver, cadmium, mercury and zinc. The hydrocarbonaceous effluent from the hydrogenation zone is preferably contacted with an aqueous scrubbing solution and the admixture is admitted to a separation zone in order to separate a spent aqueous stream, a hydrogenated hydrocarbonaceous liquid phase and a hydrogen-rich gaseous phase. The contact of the hydrocarbonaceous effluent from the hydrogenation zone with the aqueous scrubbing solution may be performed in any convenient manner and is preferably conducted by co-current, in-line mixing which may be promoted by inherent turbulence, mixing orifices or any other suitable mixing means. The aqueous scrubbing solution is preferably introduced in an amount from about 1 to about 100 volume percent based on the hydrocarbonaceous effluent from the hydrogenation zone. The aqueous scrubbing solution is selected depending on the characteristics of the hydrocarbonaceous vapor stream introduced into the hydrogenation zone. For example, if the hydrocarbonaceous vapor stream to the hydrogenation zone comprises halogenated compounds, the aqueous scrubbing solution preferably contains a basic compound such as calcium hydroxide, potassium hydroxide or sodium hydroxide in order to neutralize the acid such as hydrogen chloride, hydrogen bromide and hydrogen fluoride, for example, which is formed during the hydrogenation of the halogen compounds. In the event that the hydrocarbonaceous vapor stream contains only sulfur and nitrogen compounds, water may be a suitable aqueous scrubbing solution to dissolve the resulting hydrogen sulfide and ammonia. The resulting hydrogenated hydrocarbonaceous liquid phase is recovered and the hydrogen-rich gaseous phase may be recycled to the hydrogenation zone if desired. The resulting hydrogenated hydrocarbonaceous liquid phase is preferably recovered from the hydrogen-rich gaseous phase in a separation zone which is maintained at essentially the same pressure as the hydrogenation reaction zone and as a consequence contains dissolved hydrogen and low molecular weight normally gaseous hydrocarbons if present. In accordance with the present invention, it is preferred that the hydrogenated hydrocarbonaceous liquid phase comprising the hereinabove mentioned gases be stabilized in a convenient manner, such as, for example, by stripping or flashing to remove the normally gaseous components to provide a stable hydrogenated distillable hydrocarbonaceous product. In accordance with the present invention, the heavy stream comprising a non-distillable component recovered from the hot hydrogen flash separator is reacted in a thermal coking zone operated at thermal coking conditions to provide a thermal coking zone effluent. The thermal coking zone serves to convert the heavy stream comprising a non-distillable component and to provide coke and a gaseous thermal coking zone effluent which comprises distillable hydrocarbonaceous compounds. In the event that the feed to the thermal coking zone contains particulate matter or particulate matter is formed in the coking zone, the particulate matter becomes associated with the coke that is formed in the thermal coking zone. The resulting segregation, encapsulation and stabilization of particulate matter in the coke which is significantly less voluminous than the original temperature-sensitive hydrocarbonaceous feedstock is considered to be advantageous. The resulting gaseous thermal coking zone effluent which comprises distillable hydrocarbonaceous compounds is preferable cooled and separated to yield a fuel gas product stream which comprises normally gaseous hydrocarbons such as methane, ethane, propane, butane and their olefinic homologs, for example, and a normally liquid distillable hydrocarbonaceous stream. In a preferred embodiment of the present invention, at least a portion of the normally liquid distillable hydrocarbonaceous stream recovered from the gaseous effluent of the thermal coking zone is recycled to the hot-hydrogen flash separator and subsequently recovered as a portion of the hydrogenated distillable hydrocarbonaceous product. The thermal coking zone utilized in the present invention is preferably operated at thermal coking conditions which include an elevated temperature in the range of about 750°F (399°C) to about 950°F (510°C), a pressure from about 10 psig (69 kPa gauge) to about 150 psig (1034 kPa gauge) and a combined feed ratio from about 1 to about 2. In the drawing, the process of the present invention is illustrated by means of a simplified flow diagram in which such details as pumps, instrumentation, heat-exchange and heat-recovery circuits, compressors and similar hardware have been deleted as being non-essential to an understanding of the techniques involved. The use of such miscellaneous appurtenances are well within the purview of one skilled in the art. With reference now to the drawing, a liquid hydrocarbonaceous feed stream having a non-distillable component is introduced into the process via conduit 1 and is contacted with a hot gaseous hydrogen-rich recycle stream which is provided via conduit 10 and hereinafter described. The liquid hydrocarbonaceous feed stream and the hydrogen-rich recycle stream are intimately contacted in hot hydrogen flash separator 2. A hydrocarbonaceous vapor stream comprising hydrogen is removed from hot hydrogen flash separator 2 via conduit 3 and introduced into hydrogenation reaction zone 5 without intermediate separation thereof. A heavy non-distillable stream is removed from the bottom of hot hydrogen flash separator 2 via conduit 4 and recovered as hereinafter described. The resulting hydrogenated hydrocarbonaceous stream is removed from hydrogenation reaction zone 5 via conduit 6 and is contacted with an aqueous scrubbing solution which is introduced via conduit 7. The resulting admixture of the hydrogenated hydrocarbonaceous effluent and the aqueous scrubbing solution is passed via conduit 6 and cooled in heat-exchanger 8. The resulting cooled effluent from heat-exchanger 8 is passed via conduit 6 into high pressure vapor/liquid separator 9. A hydrogen-rich gaseous stream is removed from high pressure vapor/liquid separator 9 via conduit 10, heated to a suitable temperature in heat-exchanger 12 and utilized to contact the waste oil feed stream as hereinabove described. Since hydrogen is lost in the process by means of a portion of the hydrogen being dissolved in the exiting liquid hydrocarbon and hydrogen being consumed during the hydrogenation reaction, it is necessary to supplant the hydrogen-rich gaseous stream with make-up hydrogen from some suitable external source, for example, a catalytic reforming unit or a hydrogen plant. Make-up hydrogen may be introduced into the system at any convenient and suitable point, and is introduced in the drawing via conduit 11. A liquid hydrogenated hydrocarbonaceous stream comprising hydrogen in solution is removed from high pressure vapor/liquid separator 9 via conduit 14 and is introduced into low pressure vapor/liquid separator 15. A spent aqueous scrubbing solution is removed from high pressure vapor/liquid separator 9 via conduit 13 and recovered. A gaseous stream comprising hydrogen and any normally gaseous hydrocarbons present is removed from low pressure vapor/liquid separator 15 via conduit 17 and recovered. A normally liquid distillable hydrogenated hydrocarbonaceous product is removed from low pressure vapor/liquid separator 15 via conduit 16 and recovered. In the event that the feed stream contains water, this water is recovered from high pressure vapor/liquid separator 9 via conduit 13 together with the spent aqueous scrubbing solution as hereinabove described. The heavy non-distillable stream is removed from the bottom of hot hydrogen flash separator 2 via conduit 4 as hereinabove described is introduced into coking zone 18 which is operated at suitable coking operating conditions to produce coke which is recovered via conduit 19 and to provide a gaseous thermal coking zone effluent comprising distillable hydrocarbonaceous compounds. The resulting gaseous thermal coking zone effluent is removed from coking zone 18 via conduit 20 and introduced into fractionation zone 21. A gaseous stream comprising normally gaseous hydrocarbons is removed from fractionation zone 21 via conduit 22 and recovered. A normally liquid distillable hydrocarbonaceous stream is removed from fractionation zone 21 via conduits 23 and 24, and recovered. In a preferred embodiment of the present invention at least a portion of the normally liquid distillable hydrocarbonaceous stream removed from fractionation zone 21 is recycled to hot hydrogen flash separator 2 via conduits 23 and 1. The following example is presented for the purpose of further illustrating the process of the present invention, and to indicate the benefits afforded by the utilization thereof in producing a distillable hydrogenated hydrocarbonaceous product while minimizing thermal degradation of the temperature-sensitive hydrocarbonaceous feed stream containing a non-distillable component. EXAMPLE A waste lube oil having the characteristics presented in Table 1 and contaminated with 1020 ppm by weight of polychlorinated biphenyl (PCB) was charged at a rate of 100 mass units per hour to a hot hydrogen flash separation zone. The hot hydrogen was introduced into the hot hydrogen flash separation zone at a rate of 31 mass units per hour. The waste lube oil was preheated to a temperature of <482°F (<250°C) before introduction into the hot hydrogen flash separation zone which temperature precluded any significant detectable thermal degradation. The waste lube oil was intimately contacted in the hot flash separation zone with a hot hydrogen-rich gaseous stream having a temperature upon introduction into the hot hydrogen flash separation zone of >748°F (>398°C). In addition, the hot hydrogen flash separation zone was operated at conditions which included a temperature of 748°F (398°C), a pressure of 500 psig (3447 kPa gauge), a hydrogen circulation rate of 18000 SCFB (3034 normal m³/m³) and an average residence time of the vapor stream of 5 seconds. A hydrocarbonaceous vapor stream comprising hydrogen was recovered from the hot flash separation zone, cooled to 77°F (25°C) and introduced into a high pressure separator. An overhead gas stream in an amount of 31 mass units per hour and having the characteristics presented in Table 2 was recovered from the high pressure separator and a hereinafter described low pressure separator. ANALYSIS OF OVERHEAD GAS STREAM Hydrogen, volume percent 100 A liquid stream was removed from the high pressure separator and introduced into a low pressure separator to provide a portion of the overhead gas stream described hereinabove and a liquid bottoms stream in the amount of 88 mass units per hour having the characteristics presented in Table 3. A non-distillable liquid stream was recovered from the bottom of the flash separation zone in an amount of 12 mass units per hour and having the characteristics presented in Table 4. ANALYSIS OF NON-DISTILLABLE STREAM Specific Gravity @60°F (15°C) >0.9 Polychlorinated Biphenyl Concentration, wppm 110 In summary, this example demonstrated that a waste lube oil having a non-distillable component and containing 1020 wppm of polychlorinated biphenyl and 1306 wppm heavy metals, i.e., lead, zinc, cadmium, copper and chromium, was separated into a distillable hydrocarbonaceous stream containing 98.6 weight percent of the polychlorinated biphenyl contained in the waste lube oil and a heavy stream comprising essentially all of the non-distillable component of the waste lube oil including 99.5 weight percent of the heavy metals. The analysis of the overhead gas stream showed that the temperature-sensitive waste lube oil did not experience undesirable thermal cracking with the accompanying formation of normally gaseous hydrocarbonaceous compounds. The process of the present invention is further demonstrated by the following illustrative embodiment. This illustrative embodiment is however not presented to unduly limit the process of this invention, but to further illustrate the advantages of the hereinabove described embodiments. The following data were not completely obtained by the actual performance of the present invention, but are considered prospective and reasonably illustrative of the expected performance of the invention. ILLUSTRATIVE EMBODIMENT A waste lube oil having the characteristics presented in Table 1 hereinabove and contaminated with 1020 ppm by weight of polychlorinated biphenyl (PCB) was charged at a rate of 100 mass units per hour to a hot hydrogen flash separation zone. The hot hydrogen was introduced into the hot hydrogen flash separation zone at a rate of 31 mass units per hour. The waste lube oil was preheated to a temperature of <482°F (<250°C) before introduction into the hot hydrogen flash separation zone which temperature precluded any significant detectable thermal degradation. The waste lube oil was intimately contacted in the hot flash separation zone with a hot hydrogen-rich gaseous stream having a temperature upon introduction into the hot hydrogen flash separation zone of >748°F (>398°C). In addition, the hot hydrogen flash separation zone was operated at conditions which included a temperature of 748°F (398°C), a pressure of 500 psig (3447 kPa gauge), a hydrogen circulation rate of 18000 SCFB (3034 normal m³/m³) and an average residence time of the vapor stream of 5 seconds. A hydrocarbonaceous vapor stream comprising hydrogen was recovered from the hot hydrogen flash separation zone, and directly introduced without separation into a hydrogenation reaction zone containing a hydrogenation catalyst comprising alumina, cobalt and molybdenum. The hydrogenation reaction is conducted with a catalyst peak temperature of 700°F (371°C), a pressure of 500 psig (3447 kPa gauge), a liquid hourly space velocity of 0.5 based on hydrocarbon feed to the hydrogenation reaction zone and a hydrogen circulation rate of 18,000 SCFB (3034 normal m³/m³). The hydrogenated effluent from the hydrogenation reaction zone including hydrogen chloride is contacted with an aqueous scrubbing solution containing sodium hydroxide, cooled to about 100°F (38°C), and sent to a vapor-liquid high pressure separator wherein a gaseous hydrogen-rich stream is separated from the normally liquid hydrocarbonaceous products and spent aqueous scrubbing solution containing sodium and chloride ions. The resulting gaseous hydrogen-rich stream is heated and then recycled to the hot hydrogen flash separation zone together with a fresh supply of hydrogen in an amount sufficient to maintain the hydrogenation reaction zone pressure. A hydrogenated hydrocarbonaceous stream comprising dissolved hydrogen is removed from the vapor-liquid high pressure separator and introduced into a product stabilizer which is maintained at a pressure of 10 psia (68.9 kPa absolute) and a temperature of 100°F (38°C). An overhead gaseous stream in an amount of <1 mass unit per hour and having the characteristics presented in Table 5 is recovered from the hereinabove mentioned product stabilizer. ANALYSIS OF PRODUCT STABILIZER OVERHEAD GAS STREAM Component Mole Percent Hydrogen 53.3 C₁ 15.4 C₂ 9.0 C₃ 7.9 C₄ 6.4 C₅ 3.8 C₆⁺ 4.2 A hydrogenated hydrocarbonaceous liquid stream in an amount of 87.1 mass units per hour having the characteristics presented in Table 6 is removed from the product stabilizer. A non-distillable liquid stream is recovered from the bottom of the flash separation zone in an amount of 12 mass units per hour and having the characteristics presented in Table 7. ANALYSIS OF NON-DISTILLABLE STREAM Specific Gravity @ 60°F (15°C) >0.9 Polychlorinated Biphenyl Concentration, wppm 110 The recovered non-distillable liquid stream in the amount of 12 mass units is introduced into a thermal coking zone which is maintained at thermal coking conditions which include a pressure of about 30 psig (207 kPa gauge) and a temperature of about 800°F (427°C) to produce 1.2 mass units of coke and 10.8 mass units of a stream containing distillable hydrocarbonaceous compounds and having the characteristics presented in Table 8. ANALYSIS OF COKING ZONE HYDROCARBONACEOUS STREAM Normally gaseous hydrocarbons, mass units 0.7 Naphtha, mass units 1.2 Gas Oil, mass units 8.9 The coke recovered from the thermal coking zone is found to contain no detectable amounts of polychlorinated biphenyl compounds. A stream containing distillable normally liquid hydrocarbonaceous compounds is recycled to the hot hydrogen flash separator to be subsequently hydrogenated and recovered.

Claims: A process for treating a temperature-sensitive hydrocarbonaceous stream [1] containing a non-distillable component to produce a hydrogenated distillable hydrocarbonaceous product [24,16] comprising the steps of: (a) vaporizing at least a portion of said hydrocarbonaceous stream to provide a hydrocarbonaceous vapour stream [3] comprising hydrogen and a heavy stream [4] comprising said non-distillable component; (b) reacting said hydrocarbonaceous vapour stream [3] with hydrogen in the presence of a hydrogenation catalyst in a hydrogenation reaction zone [5]; (c) condensing at least a portion of the resulting effluent [6] from said hydrogenation reaction zone [2] to provide a hydrogen-rich gaseous stream [10] and a liquid stream [14] comprising hydrogenated distillable hydrocarbonaceous compounds; (d) thermally coking at least a portion of said heavy stream [4] in a thermal coking zone [18] to provide a thermal coking zone effluent [20]; and, (e) thereafter recovering a hydrogenated distillable hydrocarbonaceous product stream [24,16] from said liquid stream [20] from step (d), characterised in that said hydrocarbonaceous stream [1] is vaporised in step (a) by direct contact in a flash zone [2] with said hydrogen-rich gaseous stream [10] having a temperature greater than that of the hydrocarbonaceous stream [1], the temperature of the hydrocarbonaceous stream being less than 482°F (250°C), and the temperature of the hydrogen-rich gaseous stream [10] being from 200 to 1200°F (93 to 649°C). The process of Claim 1 wherein said flash conditions include a temperature from 150°F (65°C) to 860°F (460°C), a pressure from atmospheric to 2000 psig (13788 kPa gauge), a hydrogen circulation rate of 1000 SCFB (168 normal m³/m³) to 30,000 SCFB (5056 normal m³/m³) based on said temperature-sensitive hydrocarbonaceous stream, and an average residence time of said hydrocarbonaceous vapor stream comprising hydrogen in said flash zone from 0.1 seconds to 50 seconds. The process of Claim 1 wherein said hydrogenation reaction zone [5] is operated at conditions which include a pressure from atmospheric (0 kPa gauge) to 2000 psig (13790 kPa gauge), a maximum catalyst temperature from 122°F (50°C) to 850°F (454°C) and a hydrogen circulation rate from 200 SCFB (33.7 normal m³/m³) to 50,000 SCFB (8427 normal std m³/m³). The process of Claim 1 wherein said thermal coking conditions include a temperature from 750°F (399°C) to 950°F (510°C), a pressure from 10 psig (69 kPa gauge) to 150 psig (1034 kPa gauge) and a combined feed ratio from 1.0 to 2.0. The process of Claim 1 wherein at least a portion of said thermal coking zone effluent [20] is recycled to step (a).

Inventors: JAMES, ROBERT B. JR., KALNES, TOM N., STAGGS, DARRELL W.
Applicants: UOP
Application year: 1989
Main classification: C10G69
IPC codes: A62D101, C10G69, A62D3