PROCESS FOR PRE-HEATING REACTOR FEED STREAM

Abstract

A process plant and process for conversion of a hydrocarbonaceous feed, having a feed temperature, to a hydrocarbonaceous effluent, having an effluent temperature, by hydrotreatment, in the presence of a material catalytically active in hydrotreatment and an amount of hydrogen, wherein the conversion is exothermal and wherein an amount of the effluent will solidify at a solidification temperature above the feed temperature and below the effluent temperature, and wherein the feed is preheated by heat exchange, utilizing thermal energy from said effluent, wherein the heat exchange is mediated by a fluid heat exchange medium being physically separated from the feed and the effluent and having a temperature above the solidification temperature, with the associated benefit of such a process being highly energy effective, while avoiding solidification in the process lines, especially when hydrotreating feedstocks including halides.

Claims

1. A process for conversion of a hydrocarbonaceous feed, having a feed temperature, to a hydrocarbonaceous effluent, having an effluent temperature, by hydrotreatment, in presence of a material catalytically active in hydrotreatment and an amount of hydrogen, wherein said conversion is exothermal and wherein an amount of said hydrocarbonaceous effluent will solidify at a solidification temperature above said feed temperature and below said effluent temperature, and wherein said feed is preheated by heat exchange, utilizing thermal energy from said effluent, wherein said heat exchange is mediated by a fluid heat exchange medium being physically separated from said feed and said effluent and having a temperature above said solidification temperature.

2. A process according to claim 1, wherein said fluid heat exchange medium is a vapor generated from a liquid when heated by said effluent in a boiler.

3. A process according to claim 1, wherein said heat exchange medium is a liquid at the temperature of said hydrocarbonaceous effluent.

4. A process according to claim 1, wherein said hydrocarbonaceous feed comprises one or more organically bound halides and organically bound nitrogen and said material catalytically active in hydrotreatment is active in converting organically bound halides and organically bound nitrogen into inorganic halides and ammonia.

5. A process according to claim 4, wherein said effluent is separated into a first vapor phase and a first liquid phase in a separator unit, and inorganic halides are removed from said first vapor phase by contact with an amount of water.

6. A process according to claim 4, wherein the one or more halides comprise chloride.

7. A process according to claim 4, wherein the material catalytically active in converting organically bound halides into inorganic halides is also catalytically active in olefin saturation.

8. A process according to claim 4, wherein the material catalytically active in converting organically bound halides into inorganic halides comprises: (i) a group VIII metal, (ii) a group VIB metal, and (iii) a support, said support comprising one or more of the following: aluminum oxide, silicium oxide, and titanium oxide.

9. A process for hydro-treating a hydrocarbon stream comprising the process of claim 5, followed by the step of: further treating the first liquid phase from said separator unit in order to provide a hydrocarbon product.

10. A process according to claim 9, followed by the step of directing the hydrocarbon product to a steam-cracking process.

11. A system for hydrotreatment of a hydrocarbon stream comprising (a) a hydroprocessing reactor containing a material catalytically active in hydroprocessing, said hydroprocessing reactor comprising an inlet for inletting a hydrogen enriched hydrocarbon stream and an outlet for outletting a first product stream, (b) a feed heat exchanger upstream said hydroprocessing reactor and an effluent heat exchanger downstream said hydroprocessing reactor, being in thermal communication via a heat exchange medium.

12. A system according to claim 11 wherein said effluent heat exchanger is a boiler.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0039] FIG. 1 discloses a system for treating a hydrocarbon stream.

DETAILED DESCRIPTION OF THE FIGURE

[0040] FIG. 1 discloses a system for treating hydrocarbons. Even though some heat exchange units, pumps and compressors are shown in FIG. 1, further pumps, heaters, valves and other process equipment may be part of the system of FIG. 1.

[0041] The system of FIG. 1 comprises a sub-system for removing halides from a hydrocarbon stream before the hydrocarbon stream enters a stripper and/or fractionation section.

[0042] FIG. 1 shows a hydrocarbon stream 2 containing chlorine. This stream is optionally preheated, before being combined with a hydrogen rich gas stream 6 to a hydrogen enriched hydrocarbon stream 10 in order to ensure the provision of the required hydrogen for the hydrogenation of di-olefins. The hydrogen enriched hydrocarbon stream 10 is heated by heat exchange with a heat exchange medium 36 in heat exchanger 12, and optionally by further heating such as a fired heater to form a heated hydrogen enriched hydrocarbon stream 14. The first reactor 16 is optional, but may have operating conditions at a pressure of about 30 Barg and a temperature of about 180° C., suitable for hydrogenation of di-olefins. The first reactor 16 contains a material catalytically active in olefin saturation and hydro-dehalogenation. Within the first reactor 16, the heated hydrogen enriched hydrocarbon stream 14 reacts at the presence of the catalytically active material, rendering a first hydrogenated product stream 18.

[0043] The first hydrogenated product stream 18 is heated, e.g. in a fired heater 20, and transferred as a heated first hydrogenated product stream 22 to a second reactor 24 where it reacts at the presence of a second catalytically active material. Often quench gas 26 is provided to the second reactor to control the temperature. The first and second catalytically active material may be identical or different from each other and will typically comprise a combination of sulfided base metals such as molybdenum or tungsten promoted by nickel or cobalt supported on a refractory support such as alumina or silica. Typically, the reaction over the first catalytically active material is dominated by saturation of di-olefins, whereas the reaction over the second catalytically active material is dominated by saturation of mono-olefins and hydro-dehalogenation of halide-hydrocarbons, but also hydrodesulfurization, hydrodenitrogenation and hydrodeoxygenation may take place in the second reactor 24 (depending on the composition of the feedstock). Therefore, the hot product stream 28 may comprise hydrocarbons, H.sub.2O, H.sub.2S, NH.sub.3 and HCl, which may be withdrawn by washing and separation. However, NH.sub.3 and HCl may react to form NH.sub.4Cl, which under some conditions may condense at high temperatures, e.g. around 270° C. To provide an energy efficient process the hot product stream 28 is cooled to form a cooled product stream 30, by heat exchange with the hydrogen enriched hydrocarbon stream 10 via a heat exchange circuit comprising in a boiler 32, which receives boiler feed water 34 and produces steam 36, which is directed to heat the hydrogen enriched hydrocarbon stream 10 in heat exchanger 12. By providing a separate steam circuit for the heat exchange, it may be ensured that e.g. a 90° C. hydrogen enriched hydrocarbon stream 10 does not provoke cold spots in the heat exchange with the hot product stream 28. As the heat exchange is made in a boiler 32, the thermal stability is further ensured, since the temperature of a boiler is highly stable, as an amount of hot liquid water and steam are in equilibrium at the temperature defined by the boiler pressure. Therefore, the risk of having cold spots on the hot side of the thermal circuit is minimal, and thus precipitation of NH.sub.4Cl is avoided. The cooled product stream 30 is directed to a hot stripper 40 where separation is aided by a stripping medium 42, in which the cooled product stream 30 is split in a gas product fraction 44 and a liquid product fraction 46. The gas product fraction 44 is combined with a stream of water 50, providing a mixed stream 52 and cooled in cooler 54, providing a three phase stream 56, which is separated in three-way separator 58, into a light hydrocarbon stream 60, a contaminated water stream 62 and a hydrogen rich recycle gas stream 66. The hydrogen rich recycle gas stream 66 is directed to a recycle compressor 68, and directed as quench gas 26 for the second reactor 24 and as stripping medium 42 for the hot stripper 40, as well as recycle gas 8 to be combined with makeup hydrogen gas 4, forming hydrogen rich gas stream 6.

[0044] The light hydrocarbon stream 60 exiting the three-way separator 58 enters a second stripper 48 to further separate liquid and gaseous components, with the aid of a stripping medium 72. The light ends output 78 from the second stripper 48 is cooled in cooler 80 and directed as a cooled light ends fraction 82 to a further three-phase separator 84 arranged to separate an off-gas fraction 86 from a water fraction 88 and a hydrocarbon liquid fraction 92. The hydrocarbon liquid fraction 92 from the further three-phase separator 84 is recycled to the second stripper 48, the water fraction 88 can be combined with the contaminated water stream 62 and removed as sour water 90 and the gaseous fraction is removed as off-gas fraction 86. A light hydrocarbon stream 94 may be withdrawn. Liquid hydrocarbon product 74 is withdrawn from the stripper.

[0045] In an alternative embodiment the boiler based heat exchange circuit may be replaced with a circuit employing another type of heat exchange medium such as a heat transfer oil.