Steam cracking facility and method comprising a reactor heat exchanger

Abstract

The invention relates to a steam cracking facility and method using at least one reactor heat exchanger. According to the invention, the heat required for the cracking reaction is provided by a working fluid circulating in at least one closed-loop circuit (130), this circuit being connected to an inlet of the at least one reactor heat exchanger and to the corresponding outlet. This circuit (130) comprises: at least one device (131, 132) for heating the working fluid located upstream of the at least one reactor heat exchanger (112) with respect to the circulation of the working fluid, at least one heat exchanger (134, 135) located downstream of the at least one reactor heat exchanger (112) and upstream of the at least one heating device (131, 132), at least one device (138) for circulating the working fluid.

Description

DESCRIPTION TITLE: STEAM CRACKLING INSTALLATION AND PROCESS WITH A HEAT EXCHANGER-REACTOR Technical field of the invention

[0001] The present invention relates to a process for producing one or more unsaturated hydrocarbons by steam cracking and to a steam cracking plant. In particular, the present invention relates to a steam cracking plant and process incorporating at least one heat exchanger reactor enabling carbon-free operation. Technological background

[0002] The steam cracking process of hydrocarbons allows the production of light olefins, and more specifically ethylene and propylene. It consists of thermally cracking a mixture of hydrocarbons and steam in one or more reactors at high temperatures of around 800 to 850 °C and under low pressures (1 to 3 bar) to break carbon-hydrogen and / or carbon-carbon bonds and produce unsaturated hydrocarbons within the reactor(s). The effluents exiting the reactor(s) are then quenched in one or more heat exchangers, generally designated by the acronyms TLX or TLE (Transfer Line Exchanger), to limit secondary reactions such as the polymerization of olefins, dienes, and acetylenes. The cooled effluents are then fractionated.

[0003] Most steam cracking plants today use the combustion of a fossil fuel, generally a methane-rich gas, to provide the thermal energy required for the process. This generates significant CO2 emissions, representing approximately 0.7 to 1.6 tonnes of CO2 per tonne of high-value-added chemical (HVC). Furthermore, in conventional steam cracking furnaces, the heat from gas combustion is transferred to the tubes carrying the feedstock primarily by radiation, with minimal convection heat transfer. Because the combustion gas temperature is significantly higher than the surface temperature of these tubes, and because radiative heat transfer is not completely uniform, localized temperature spikes can occur. These spikes promote coking within the reaction tubes, necessitating more frequent plant shutdowns.

[0004] Increasing environmental concerns, however, require replacing the fossil fuel traditionally used to provide the heat needed for steam cracking with decarbonized energy (without CO2 emissions) and in particular renewable energy, especially renewable electricity produced by wind turbines and / or solar panels.

[0005] There is therefore a need for a steam cracking installation and process that allows the steam cracking reaction to be carried out at a lower environmental cost. There is also a need for a steam cracking installation and process that limits localized temperature increases.

[0006] Document FR 2 675498 A1 describes a steam cracking process that partially overcomes these drawbacks. To this end, the steam cracking reaction is carried out inside a shell-and-tube heat exchanger reactor. The thermal energy required for the reaction is supplied by the combustion of a gas mixture, which is partially performed within the heat exchanger reactor. The gas mixture to be burned is produced by a gas generator and then enters the heat exchanger reactor, possibly after passing through an afterburner chamber. The resulting production gases are sent to another gas-gas heat exchanger where the feedstock to be cracked is preheated before entering the heat exchanger reactor. To maintain a substantially constant temperature in the reaction tubes, injection tubes are arranged inside the heat exchanger reactor.

[0007] The process described in this document has the drawback of requiring the combustion of CO2-emitting gases. Furthermore, since part of the gas combustion occurs inside the heat exchanger reactor, additional devices must be incorporated within the reactor to achieve a uniform temperature, thus complicating its construction. Moreover, the combustion gases entering the heat exchanger are still very hot (close to the adiabatic combustion temperature), necessitating appropriate materials, as do the combustion gases exiting the heat exchanger reactor. These latter gases must also be recovered by extracting their sensible heat. The combustion gases are also close to atmospheric pressure and therefore require a large heat exchange surface area to achieve sufficient heat transfer within the reactor tubes.

[0008] The invention aims to overcome all or part of the drawbacks of the prior art. In particular, the invention aims to provide a less energy-intensive process and installation for producing one or more unsaturated hydrocarbons by steam cracking, advantageously by indirectly using decarbonized electricity to produce the heat required for the steam cracking. Summary of the invention

[0009] To this end, the invention proposes a steam cracking installation comprising:

[0010] - at least one shell and tube heat exchanger reactor, each heat exchanger reactor comprising means for supplying a suitable gas mixture comprising at least one hydrocarbon, in particular a gas mixture to be steam cracked, connected to an inlet selected from a tube inlet and a shell inlet, and means for discharging a hot gaseous effluent, in particular the cracked gas mixture, connected to a corresponding outlet from the tubes or the shell,

[0011] - a cooling section adapted for quenching, connected to the exhaust systems of each heat exchanger reactor,

[0012] characterized in that it further comprises:

[0013] - at least one closed-loop circuit in which a working fluid circulates, this circuit being connected on one side to the other inlet of at least one heat exchanger reactor chosen from a tube inlet and a shell inlet, and on the other side to the corresponding tube or shell outlet, each circuit comprising:

[0014] at least one working fluid heating device located upstream, in particular immediately upstream, of at least one heat exchanger reactor relative to the working fluid circulation,

[0015] at least one heat exchanger located downstream of at least one heat exchanger reactor and upstream of at least one heating device,

[0016] at least one device for circulating the working fluid.

[0017] Thus, there is no combustion inside the heat exchanger reactor, so its structure can be simplified and the risk of hot spots is limited. In other words, the heat exchanger reactor used in the present invention is not designed to produce heat by combustion: it is only capable of transferring heat between a first fluid circulating in the tubes of said heat exchanger reactor and a second fluid circulating in the shell.

[0018] The gas mixture to be steam cracked typically comprises, or is even made up of, at least one hydrocarbon and dilution steam. The at least one hydrocarbon may advantageously comprise or consist of saturated hydrocarbons, generally having a carbon number of 2 to 20, for example, selected from ethane, naphtha, FCC gasoline, cokers' gasoline, diesel fuel, pyrolysis oils (ex-biomass or ex-plastic), propane, butane, pentane, hexane, paraffins obtained from the deoxygenation of triglycerides or fatty acids, alone or in combination. The dilution steam, also called dilution steam or steam hereafter, may be produced by any conventional means and may be mixed with the at least one hydrocarbon in proportions suitable for steam cracking by any suitable conventional means.

[0019] At least one working fluid heating device may advantageously be located upstream of the inlet connecting said circuit to at least one heat exchanger reactor with respect to the working fluid circulation.

[0020] Advantageously, at least one closed-loop circuit can be connected to the shell of at least one heat exchanger reactor. The gas mixture to be steam cracked then circulates through the tubes of at least one heat exchanger reactor. This can, in particular, facilitate control of the residence time and pressure of the gas mixture inside the reactor.

[0021] Advantageously, at least one closed-loop circuit may include at least two heating devices connected in series and / or parallel. This can facilitate heating the working fluid to the desired temperature.

[0022] Preferably, at least one heating device is a heating device that does not emit CO2, either because there is no combustion, the heating device requiring only an electrical supply, or because combustion does not emit CO2.

[0023] The heating device may be in the form of a boiler, a furnace or a superheater, preferably not emitting CO2.

[0024] Advantageously, at least one heating device can be chosen from among a Joule effect heating device, a microwave heating device, a shock wave heating device, a plasma heating device, an induction heating device, a heat pump, a hydrogen furnace.

[0025] Advantageously, the cooling section may include at least one heat exchanger connected on the one hand to the exhaust means of at least one heat exchanger reactor and on the other hand to the supply means of at least one heat exchanger reactor so as to preheat the gas mixture entering the latter by means of the gaseous effluent exiting the latter.

[0026] Advantageously, at least one heat exchanger in the cooling section can be connected to at least one heat exchanger in the closed-loop circuit to receive at least one component of the preheated gas mixture. This notably improves the overall energy performance of the installation.

[0027] Advantageously, at least one closed-loop circuit may include a first and a second heat exchanger mounted in series downstream of at least one heat exchanger reactor with respect to the direction of flow of the working fluid. The first heat exchanger is connected to a water supply line, particularly in the form of steam, and adapted to heat the water. The second heat exchanger is connected to a supply line for a component of the gas mixture, particularly hydrocarbons, and adapted to preheat it before it enters the at least one heat exchanger reactor or before it enters a heat exchanger in the cooling section. This also improves the overall energy performance of the installation.

[0028] Advantageously, in another embodiment that improves the overall energy performance of the installation, at least one closed-loop circuit comprises a first and a second heat exchanger mounted in series downstream of at least one heat exchanger reactor with respect to the direction of flow of the working fluid, the first heat exchanger being connected to the circuit, with respect to the direction of flow of the working fluid, on the one hand upstream, in particular immediately upstream, of at least one heating device, and in downstream of the second heat exchanger, and further downstream, specifically immediately downstream, of at least one heat exchanger reactor and upstream of the second heat exchanger, the second heat exchanger being connected to a water supply line, particularly in liquid form, and adapted to preheat water using the working fluid. The closed-circuit loop 130 thus passes twice through the first heat exchanger.

[0029] In a variant of this embodiment, the installation may further include at least two preheating heat exchangers: the first preheating heat exchanger, in particular for dilution steam, being connected on the one hand to a heat exchanger of the cooling section to receive a cooled gaseous effluent, and on the other hand to the second heat exchanger of the closed loop circuit to further heat and vaporize the water exiting the latter, the second preheating heat exchanger being connected on the one hand to the heat exchanger of the cooling section to supply it with at least one component of the gaseous mixture, in particular hydrocarbons, preheated, and on the other hand to the first preheating heat exchanger to receive the further cooled gaseous effluent.

[0030] In another variant of this embodiment, the installation may further comprise at least two preheating heat exchangers for at least one component of the gas mixture, in particular hydrocarbons: the first preheating heat exchanger being connected on the one hand to the second preheating heat exchanger to supply it with at least one component of the preheated gas mixture, and on the other hand to a second heat exchanger of the cooling section to receive the further cooled gaseous effluent, the second preheating heat exchanger advantageously being connected on the one hand to a first heat exchanger of the cooling section to receive a (different) working fluid heated by the gaseous effluent exiting the reactor-heat exchanger, and on the other hand to the second heat exchanger of the cooling section to supply it with at least one component of the preheated gas mixture,The first and second heat exchangers of the cooling section are mounted in series so as to cool the gaseous effluent exiting the reactor-heat exchanger before it passes through the first preheating heat exchanger.

[0031] These preheating heat exchangers thus serve to preheat the constituents of the gas mixture before their introduction into the reactor-heat exchanger, and in particular before their entry into the heat exchanger of the cooling section used to rapidly cool the gaseous effluent and preheat the gas mixture.

[0032] In particular, the cooling section then includes a heat exchanger typically connected on the one hand to the exhaust means of at least one heat exchanger reactor and on the other hand to the supply means of at least one heat exchanger reactor so as to preheat the gas mixture entering the latter by means of the gaseous effluent exiting the latter.

[0033] Advantageously, the cooling section may include a first and a second heat exchanger mounted in series: the first heat exchanger being connected on the one hand to the evacuation means of at least one heat exchanger reactor, and on the other hand to a preheating heat exchanger located upstream of at least one heat exchanger reactor with respect to the circulation of the fluids, so as to preheat a constituent of the gas mixture, the second heat exchanger being connected on the one hand to the first heat exchanger and on the other hand to the preheating heat exchanger and to at least one heat exchanger of the closed loop circuit, to receive at least one constituent of the preheated gas mixture, in particular to receive respectively the preheated hydrocarbons and the dilution water vapor.

[0034] In particular, the preheating heat exchanger can be connected to the first heat exchanger in the cooling section by another closed loop circuit in which another working fluid circulates, typically water in the form of vapor and / or liquid.

[0035] In one variant, the second heat exchanger of the closed-loop circuit can be connected to the preheating heat exchanger in order to supply it with the component of the gas mixture preheated by the working fluid.

[0036] In the various embodiments, the different heat exchangers mentioned are advantageously shell and tube heat exchangers.

[0037] The invention also relates to a steam cracking process of a gaseous mixture of a hydrocarbon feedstock and water vapor, particularly suitable for implementation by a steam cracking plant according to the invention, said process comprising a heating phase in a heating section under suitable conditions, which delivers a hot steam cracking effluent, particularly rich in unsaturated hydrocarbons, particularly in ethylene, and a rapid cooling phase of said effluent in a cooling section under suitable conditions, and the cooled steam cracking effluent is recovered.

[0038] According to the invention: - The gas mixture, preferably preheated, is introduced into at least one pressure shell and tube heat exchanger reactor via an inlet chosen from a tube inlet and a shell inlet, and the gas mixture is circulated inside the tubes or shell of said heat exchanger reactor; the heating phase of the gas mixture is carried out in at least one Reactor-heat exchanger according to the following steps: (a) a working fluid is circulated within a closed-loop circuit, this circuit being connected on one side to the other inlet of at least one heat exchanger reactor selected from a tube inlet and a shell inlet, and on the other side to the corresponding outlet of the tubes or the shell, and said working fluid is heated to a target temperature higher than the temperature to which the gas mixture is to be heated by means of at least one heating device for the closed-loop circuit, in particular located upstream of the inlet of at least one heat exchanger reactor, (b) the working fluid is introduced at the target temperature into the reactor-heat exchanger, the cooled working fluid is recovered and reinjected into the closed-loop circuit upstream of at least one heating device of said circuit, and a hot steam cracking effluent is recovered and sent immediately to the cooling section.

[0039] Advantageously, the gas mixture to be steam cracked can be circulated inside the tubes of at least one heat exchanger reactor.

[0040] Advantageously, the method according to the invention may further comprise at least one of the following features:

[0041] - the working fluid is chosen from water, CO2, helium, nitrogen or argon, alone or in combination, the target temperature of the working fluid is from 900 to 1600 °C, preferably from 1000 to 1400 °C, more preferably from 1100 to 1300 °C, even more preferably from 1150 to 1250 °C, the pressure of the working fluid is from 30 barg to 80 barg.

[0042] Advantageously, the gaseous effluent that has circulated in at least one heat exchanger reactor, namely the cracked effluent, can be recovered and sent to at least one heat exchanger in the cooling section to cool it rapidly and preheat the gaseous mixture to be steam cracked before it enters at least one heat exchanger reactor.

[0043] Advantageously, the working fluid that has circulated in at least one heat exchanger reactor can be recovered and sent to at least one heat exchanger of the closed-loop circuit in which at least one fluid selected from (i) at least one constituent of the gas mixture is preheated before entering at least one heat exchanger reactor or before entering at least one heat exchanger of the cooling section, (ii) water, (iii) steam, and (iv) the working fluid before entering at least one heat exchanger reactor.

[0044] In particular, the following implementation methods can be envisaged:

[0045] - The working fluid, having circulated through at least one heat exchanger reactor, is sent to a first heat exchanger in the closed-loop circuit. to heat water vapor, especially before preheating it in a heat exchanger in the cooling section, typically mixed with the other component of the gas mixture, then the working fluid is sent to a second heat exchanger in said circuit to heat another component of the gas mixture (e.g. hydrocarbons), especially before preheating it (typically mixed with water vapor) in a heat exchanger in the cooling section.

[0046] - The working fluid, having circulated in at least one heat exchanger reactor, is sent to a first heat exchanger in the closed-loop circuit to preheat the working fluid before it is heated by at least one heating device, and then to a second heat exchanger in the same circuit to heat water, particularly before its vaporization in a first preheating heat exchanger receiving heat from the effluent exiting a heat exchanger in the cooling section. The recovered effluent can then be sent to yet another preheating heat exchanger to preheat another component of the gas mixture (particularly hydrocarbons) before it is mixed with the dilution steam exiting the first preheating heat exchanger. The mixture is then preheated in a heat exchanger in the cooling section, particularly before entering the heat exchanger reactor.

[0047] - the working fluid having circulated in at least one heat exchanger reactor is sent to a first heat exchanger of the closed-loop circuit to heat steam, in particular before preheating it in a heat exchanger of the cooling section, typically mixed with the other component of the gas mixture, then the working fluid is sent to a second heat exchanger of said circuit to heat another component of the gas mixture (in particular hydrocarbons), the hot effluent having circulated in at least one heat exchanger reactor being sent to a first and a second heat exchanger mounted in series of the cooling section, the second heat exchanger of the cooling section receiving, typically mixed, on the one hand the component of the gas mixture preheated first by the second heat exchanger of said circuit and then by a preheating heat exchanger,and on the other hand, the dilution steam heated by the first heat exchanger of said circuit. The preheating exchanger is advantageously connected to the first exchanger of the cooling section by another closed-loop circuit in which another working fluid circulates, typically water in liquid and / or vapor form.

[0048] - the working fluid having circulated in at least one heat exchanger reactor is sent to a first heat exchanger of the closed-loop circuit to heat the working fluid before it enters the heating device, then the working fluid is sent to a second heat exchanger of said circuit to heat steam before its preheating, typically mixed with the other component of the gas mixture in a heat exchanger of the section of For cooling, the hot effluent, having circulated through at least one heat exchanger reactor, is sent to a first and a second heat exchanger in the cooling section, connected in series. The second heat exchanger in the cooling section typically receives a mixture of, on the one hand, the component of the gas mixture preheated first by a first preheating exchanger receiving the gaseous effluent exiting the cooling section and then by a second preheating heat exchanger, and on the other hand, the dilution steam heated by the second heat exchanger of said circuit. The second preheating exchanger is advantageously connected to the first heat exchanger in the cooling section by another closed-loop circuit in which another working fluid circulates, typically water in liquid and / or vapor form.

[0049] The heating section of the installation and process according to the invention may comprise several heat exchanger reactors mounted in parallel, for example, 2 to 10, preferably 2 to 8. In this case, maintenance can be performed on one of the heat exchanger reactors while the others are operating. Although the invention makes it possible to limit coking, it can nevertheless accumulate over the long term. The maintenance operation can then be a decoking. Detailed description of the invention

[0050] The invention is now described with reference to the accompanying, non-limiting drawings, in which:

[0051] Figure 1 schematically represents a steam cracking installation according to a first embodiment,

[0052] Figure 2 schematically represents a steam cracking installation according to a second embodiment,

[0053] Figure 3 schematically represents a steam cracking installation according to a third embodiment,

[0054] Figure 4 schematically represents a steam cracking installation according to a fourth embodiment,

[0055] Figure 5 schematically represents a steam cracking installation according to a fifth embodiment,

[0056] Figure 6 schematically represents a steam cracking installation according to a sixth embodiment.

[0057] In the figures, the same elements are designated by the same references.

[0058] Figure 1 represents a steam cracking installation 100 comprising a heating section 110 in which the steam cracking reaction takes place including at least one shell and tube heat exchanger reactor 112, here only one and a cracked effluent cooling section 120.

[0059] The heat exchanger reactor 112 (also referred to as the "reactor-exchanger" hereafter) includes a tube inlet 113, a tube outlet 114, a shell inlet 115 and a shell outlet 116.

[0060] The reactor-exchanger 112 further includes means for supplying a suitable gaseous mixture comprising at least one hydrocarbon and dilution steam. These supply means include a conduit 117 connected in this example to the inlet 113 of the tubes. For example, the mass ratio between the dilution steam and the hydrocarbon(s) varies from 0.2 to 1, preferably from 0.3 to 0.5.

[0061] The reactor-exchanger 112 also includes means for venting a hot gaseous effluent. These venting means include a pipe 118 connected in this example to the outlet 114 of the tubes.

[0062] The invention is not, however, limited to this embodiment, and it could be envisaged that the pipes 117 and 118 be connected respectively to the inlet 115 and outlet 116 of the calender, although this is not preferred. Implementing the steam cracking reaction inside the tubes of the reactor-exchanger 112 has the advantage of facilitating control of the residence time and pressure of the gas mixture in the reactor-exchanger 112, and of simplifying the reactor's construction. Indeed, given the relatively high steam cracking pressures, implementing the reaction in the calender would require significantly thickening its walls.

[0063] One or more of the following characteristics advantageously define a heat exchanger reactor usable in the present invention for the steam cracking step of the gas mixture.

[0064] For example, the heat exchanger reactor is a shell-and-tube heat exchanger reactor. The heat exchanger is of the recuperative type, because the cooler fluid recovers some of the heat from the hotter fluid by heat transfer across a separating wall.

[0065] For example, shell-and-tube heat exchanger reactors typically consist of a bundle of round tubes (tube bundle) mounted in large cylindrical shells, with the tube axis parallel to the shell axis. The three most common types of shell-and-tube heat exchangers are (1) fixed-plate-and-tube heat exchangers, (2) U-tube heat exchangers, and (3) floating-head heat exchangers. In all three types, the front head (plenum through which the fluid enters the tubes) is fixed, while the rear head (plenum through which the fluid exits the tubes or is recirculated back to the front head in the case of multipass heat exchangers) can be fixed or floating, depending on the thermal constraints in the shell, tubes, or The tube sheet (a perforated plate holding the tubes) is subject to temperature differences resulting from heat transfer. These exchangers can have straight tubes, attached to tube sheets at both ends, or U-shaped tubes, attached to a tube sheet at only one end. In fixed-tube shell and tube heat exchangers, the shell is welded to the tube sheets. Fixed-tube plate designs are the most vulnerable to differential thermal expansion because they lack any inherent features to absorb thermal stresses. Optionally, expansion bellows can be incorporated into the shell to eliminate excessive stresses caused by expansion.

[0066] U-shaped tubes, which have a first branch and a second branch where the flow direction reverses from the first to the second branch, allow for free expansion of the tube within the shell space, thus reducing mechanical stress on the heat exchanger. The two branches are generally connected by a smooth elbow.

[0067] In the floating-head heat exchanger, which also features a first straight leg and a second straight leg at both ends attached to a tubesheet where the flow direction reverses in an open head space (a plenum common to all tubes), a tubesheet is not welded to the shell at the rear head but can move or float. This is because the tubesheet at the front head is sealed in the same way as in the fixed-tubesheet design. The tubesheet at the rear head of the shell has a slightly smaller diameter than the shell, allowing the assembly to move and expand as needed.

[0068] Spiral or twisted tube heat exchangers consist of coils wound in a spiral or twisted configuration within a casing, either between two fixed tube sheets, on a floating tube sheet, or in a U-shape fixed to a tube sheet. The heat transfer coefficient is higher in a spiral or twisted tube than in a straight tube, and they are well-suited to thermal expansion.

[0069] Shell-and-tube heat exchangers are usually classified according to the number of fluid passes through the shell and tubes. Heat exchangers in which all tubes make a half-turn in the shell, for example, are called one-pass shell-and-two-pass tube heat exchangers. Similarly, a heat exchanger that has two passes in the shell (shell with a longitudinal baffle) and two passes in the tubes is called a two-pass shell-and-two-pass tube heat exchanger.

[0070] Co-current heat exchangers, also known as parallel flow heat exchangers, are heat exchange devices in which fluids move parallel and in the same direction relative to each other.

[0071] Counterflow heat exchangers, also called reverse flow heat exchangers, are designed so that the fluids move antiparallel (i.e., parallel but in opposite directions) to each other inside the heat exchanger.

[0072] Hybrid flow heat exchangers exhibit a combination of the characteristics of the flow configurations mentioned previously. For example, heat exchangers may incorporate multiple flow paths and arrangements (e.g., counter-current and co-current) within a single exchanger.

[0073] Baffles can be classified into two types: transverse and longitudinal. Longitudinal baffles control the overall direction of fluid flow from the shell to achieve the desired overall configuration of the two fluid flows. Transverse baffles can be classified into plate baffles and grid baffles (rod, strip, and other axial flow types). Plate baffles increase fluid turbulence in the shell, resulting in higher heat transfer coefficients and minimizing temperature differences between the tubes and thermal stresses. Single and double segment baffles are the most frequently used due to their ability to maximize heat transfer (thanks to a high heat transfer coefficient on the shell side) for a given pressure drop in a minimal space.Combined flow provides a slightly higher heat transfer coefficient than purely longitudinal flow and minimizes temperature differences between the tubes. Rod (or bar) baffles, the most common type of grid baffle, are used to support the tubes and increase fluid turbulence within the shell. An alternative to rod-baffle heat exchangers is the use of twisted tubes. A shell and tube heat exchanger with helical baffles offers the following advantages: lower pressure drop on the shell side while maintaining the high heat transfer coefficient of a segmented exchanger, and the elimination of dead zones and recirculation areas.

[0074] In one embodiment, the heat exchanger reactor is a shell-and-tube reactor comprising at least two tubes defining a tubular section and a shell section surrounding the tubular section, in which the tubular section forms a cracking section. Preferably, the heat exchanger reactor is co-current, with the flow direction in the tubular section being in the same direction as the flow direction in the shell section.

[0075] In another embodiment, the heat exchanger reactor is a shell and tube reactor comprising at least two U-shaped tubes defining a tubular section with tube inlets and outlets at the same location and a shell section surrounding the tubular section with the inlet and outlets of the shell section at opposite locations, wherein the tubular section forms a cracking section. Preferably, the flow direction in the first branch of the tubular part is counter-current to the flow direction in the shell part, while the flow direction in the second branch of the tubular part is arranged co-current to the flow in the envelope part.

[0076] In another embodiment, the heat exchanger reactor is a shell-and-tube reactor comprising at least two U-shaped tubes defining a tubular section with tube inlets and outlets at the same location and a shell section surrounding the tubular section, wherein the tubular section forms a cracking section and a deflector is located at the center of the shell section with the inlet and outlet of the shell section at the same location. Preferably, the flow direction in the first and second branches of the tubular section is in the same direction as the flow direction in the shell section.

[0077] A reactor-exchanger 112 typically has an elongated shape, usually arranged vertically.

[0078] In general, the reactor-exchanger 112 contains a plurality of reaction tubes, usually of small internal diameter, for example 10 to 100 mm. A reactor-exchanger can contain a thousand tubes of approximately 20 mm to 80 mm in diameter, for example made of Incoloy-type steel, with a high nickel content. These tubes are typically straight tubes, substantially parallel to each other and substantially parallel to the axis of the reactor-exchanger, or U-shaped tubes as previously described.

[0079] These tubes, for example, are adapted to receive, by means of a parallel supply, a mixture of steam and hydrocarbons preheated to a temperature T2 of 570-650 °C or 580-680 °C, preferably from 580 to 635 °C, more preferably from 590 to 620 °C, typically under 1.5 to 3 bar, by the line 117 opening at the lower end of the reactor 112, so that, in the case of straight tubes, the hydrocarbon gas mixture circulates from bottom to top in the reactor-exchanger under conditions such that its residence time is limited to about 100 to 300 ms.

[0080] The cooling section 120 adapted to perform quenching of the cracked effluent is connected to the evacuation means 118 of the exchange reactor 112.

[0081] In this embodiment, the cooling section includes a heat exchanger 122 receiving the gaseous effluent from the reactor-exchanger 112.

[0082] According to the invention, the installation further comprises a closed loop circuit 130 in which a working fluid circulates, this circuit being connected on one side to the inlet 115 of the shell of the reactor-exchanger 112 and on the other side to the corresponding outlet 116 of the shell.

[0083] This circuit 130 includes in this embodiment:

[0084] two heating devices 131, 132 for the working fluid, here mounted in series and located upstream of the reactor-exchanger 112 with respect to the circulation of the working fluid,

[0085] two heat exchangers 134, 135, here mounted in series, located downstream of the reactor-exchanger 112 and upstream of the heating devices 131, 132,

[0086] a device for circulating the working fluid 138.

[0087] The first heat exchanger 134 is used to heat steam to obtain dilution steam suitable for mixing with the hydrocarbon feedstock to be steam cracked. For this purpose, this first heat exchanger 134 uses the heat from the working fluid circulating in circuit 130 at the outlet 116 of the reactor-exchanger 112. The second heat exchanger 135 uses the residual heat from the working fluid exiting the first heat exchanger 134 to preheat the hydrocarbon feedstock before it is mixed with the dilution steam and this mixture enters the heat exchanger 122 of the cooling section.

[0088] In this embodiment, the first heating device 131 is an electric boiler and the second heating device 132 is an electric superheater.

[0089] The invention is not limited, however, by the number, nature, or arrangement of the heating devices, provided that the device(s) do not emit CO2. Preference will therefore be given to electric heating devices that produce heat by Joule heating, microwaves, shock waves, plasma, and / or induction, and to heat pump-type heating devices. Combustion heating devices using hydrogen (H2), the combustion of which produces only water, may also be used. Each device may be in the form of a boiler, a furnace, or a superheater. When several devices are present, they may be connected in series and / or in parallel.

[0090] In this embodiment, the working fluid circulation device 138 is a pump. However, the invention is not limited to this device, which will be chosen according to the nature of the working fluid. For example, a pump may be used when the fluid is liquid in one part of the circuit, and a compressor or a fan when the fluid is gaseous. More than one circulation device may be provided depending on the dimensions of the circuit 130. The working fluid may, in particular, be chosen from water, CO2, helium, nitrogen, or argon, alone or in mixtures.

[0091] The embodiment of figure 1 is particularly suited to a working fluid which is water, and which will be in a liquid state in one part of the circuit (that where the pump 138 is located) and in a vapor state in the rest of the circuit 130.

[0092] The steam cracking of a hydrocarbon feedstock using the installation shown in Figure 1 is now described.

[0093] This steam cracking process includes, in particular, a heating phase implemented in the heating section 110 under conditions suitable for carrying out steam cracking, which delivers a hot steam cracking effluent, and a rapid cooling phase of said effluent implemented in the cooling section 120 under suitable conditions.

[0094] Typically, at the inlet of heating section 110, the temperature T2 of the gas mixture can be 600 to 680 °C or 570 to 650 °C, preferably 580 to 635 °C, and even more preferably 590 to 620 °C. The temperature T4 of the gas effluent at the outlet of heating section 110 is typically 800 to 900 °C, preferably 800 to 880 °C, even more preferably 810 to 870 °C, and even more preferably 820 to 860 °C. The residence time of the gas mixture in the heating section is short, typically 100 to 300 ms. In the heating section, the gas mixture is, for example, maintained at a pressure of 1.5 to 3 bar.

[0095] This effluent contains unreacted raw materials and reaction products that vary depending on the nature of the feedstock to be cracked. For example, if the hydrocarbon feedstock to be cracked is naphtha, the effluent contains the desired olefins (mainly ethylene and propylene), hydrogen, methane, a mixture of C4 hydrocarbons (mainly isobutylene and butadiene), gasoline (aromatics in the C6 to C8 range), ethane, propane, acetylenes (acetylene, methylacetylene, propadiene), and heavier hydrocarbons with boiling points in the fuel oil temperature range. This effluent containing the cracked gases is rapidly cooled during the cooling phase, typically to 300–510 °C, to stop pyrolysis reactions and minimize secondary polymerization reactions.Depending on the average molecular mass of the feedstock, the relative quantities of the different products vary: for light feedstocks, such as ethane, there are few hydrocarbons with more than 4 carbons. The cooled effluent containing the cracked gases is then fractionated to separate the products of interest.

[0096] The working fluid follows the following path in circuit 130 via lines 130a-130f. Pump 138 sends the working fluid, here liquid water, via line 130a to the electric boiler 131 where steam is produced, for example, here at a temperature of 225 °C and a pressure of 25 bar. Then, the working fluid (steam at 225 °C) enters via line 130b into the superheater 132, from which it emerges superheated to a temperature T3, for example, 1200 °C. The superheated working fluid then enters via line 130c into the shell of the reactor-heat exchanger 112 through inlet 115 and circulates within it. The superheated working fluid cools as it passes through the reactor-exchanger 112, transferring its heat to the reactor-exchanger tubes. The working fluid thus exits at a temperature T5 lower than its inlet temperature T3, here approximately 700 °C.At the outlet of the reactor-exchanger, the working fluid is sent, notably directly, via a 130d pipe into the first. Heat exchanger 134. This receives steam at a temperature T6, for example 180 °C, from a line 1, which it heats to a temperature T7, for example 500 °C. The dilution steam exiting the first heat exchanger 134 is discharged through a line 2 which joins a line 4 in which the hydrocarbon feed circulates. Thus, the first heat exchanger 134 allows water vapor to be brought to a temperature T7 allowing it to be used as dilution water vapor intended to be mixed with the hydrocarbon feed to be steam cracked before its entry into the heat exchanger 122 via a line 6. The working fluid, cooled by its passage through the first exchanger 134, from a temperature T5 to a temperature T8 of about 200 °C, is then sent via a line 130e to the second heat exchanger 135 in which it performs a first preheating to a temperature T10 of the hydrocarbon feed brought by a line 3 at a temperature T9.At the outlet of this second heat exchanger 135, the working fluid, in this case water, is again in a liquid state at a temperature T11 (lower than temperature T8) and reaches the pump 138 via a line 130f. It is then returned by the pump 138 to the first heating device 131 via the line 130a. The second heat exchanger 135 can, for example, heat naphtha from 60 °C to 120 °C (naphtha in its gaseous state), which is then mixed with the 500 °C dilution steam exiting the first heat exchanger 304 of circuit 130. The resulting mixture can reach a temperature T1 of approximately 300 °C and is then preheated to a temperature T2 of approximately 600 °C as it passes through the heat exchanger 122, which is used to quench the gaseous effluent. The gas mixture then enters the tubes of the reactor-exchanger 112 through the inlet 113.These tubes are heated primarily by convection, approximately to the temperature T3 of the working fluid circulating in the calender. The working fluid can flow in the same direction as the gas mixture in the tubes, thus promoting a greater heat input at the very beginning of the reaction. The gas mixture thus undergoes a steam cracking reaction, producing a gaseous effluent exiting the reactor-exchanger 114 through outlet 114 and discharged via line 118 to the heat exchanger 122, where it is cooled by the gas mixture. From the outlet of the heat exchanger 122, a line 5 carries the cooled steam cracking effluent to the sections typically found in a steam cracking plant (not shown), allowing for the recovery of the products of interest. These sections include cooling, compression, and fractionation sections, which are well known to those skilled in the art and will not be described in further detail.

[0097] Generally, the temperature T1 can range from 100 to 330 °C, preferably from 120 to 320 °C, and even more preferably from 130 to 310 °C. T2 is higher than T1 and can be within the aforementioned ranges. T4 is generally higher than T2 and can be within the aforementioned ranges. T3 is typically higher than T4, T2, and T1. T3 can range from 1000 to 1600 °C, preferably from 1150 to 1250 °C.

[0098] The temperature T5 of the working fluid at the outlet of the heat exchanger reactor 112, lower than T3, can be from 670 to 730 °C, preferably from 680 to 720 °C, preferably from 690 to 710 °C. The temperature T8 of the working fluid at the outlet of the first exchanger 134, lower than T5, can be from 170 to 285 °C, preferably from 180 to 265 °C, preferably from 190 to 250 °C.

[0099] The T6 temperature of the dilution vapor can be from 15 to 210 °C, preferably from 20 to 200 °C, and more preferably from 30 to 190 °C. The T7 temperature of the dilution vapor, which is higher than the T6 temperature, can be from 150 to 530 °C, preferably from 180 to 520 °C, and more preferably from 190 to 510 °C.

[0100] The temperature T9 of at least one hydrocarbon may be from 20 to 90 °C, preferably from 30 to 80 °C, and more preferably from 40 to 70 °C. The temperature T10 of at least one hydrocarbon, particularly a saturated one, above the temperature T10, may be from 95 to 145 °C, preferably from 100 to 140 °C, and more preferably from 110 to 130 °C.

[0101] The working fluid temperature T11 can be from 200 to 285 °C, preferably from 220 to 260 °C, and even more preferably from 230 to 250 °C. If the working fluid is water in vapor form, the temperatures may depend on the pressure in the circuit 130. In this example, the pressure in the loop is 35 bar.

[0102] The invention is of course not limited by the nature of the hydrocarbons that can be steam cracked. The installation and the process according to the invention can thus be implemented for the steam cracking of various hydrocarbon feedstocks of fossil origin such as ethane, liquefied petroleum gases (propane, butane), naphtha, diesel and vacuum distillate, of various hydrocarbon feedstocks of biological origin, such as ethane, propane, butanes, naphtha and distillates produced during the hydrotreating / hydrocracking of fatty acid esters (for example triglycerides), biomass pyrolysis oils and / or biomass hydrothermal liquefaction oils, or even other hydrocarbon feedstocks obtained by pyrolysis, hydrothermal liquefaction and / or hydrocracking of plastic waste.

[0103] The embodiment shown in Figure 2 differs from that of Figure 1 primarily in the cooling section 120 and the preheating of the hydrocarbon feed. In this embodiment, the cooling section 120 comprises a first heat exchanger 124 and a second heat exchanger 126 connected in series via a pipe 119. The effluent exiting the reactor-exchanger 112 through outlet 114 and pipe 118 first passes through the first heat exchanger 124 and then the second heat exchanger 126 before being sent via pipe 5 to the fractionation section (not shown). The installation 100 further includes a preheating heat exchanger 140 connected by another closed-loop circuit 142 to the first heat exchanger 124 of the cooling section. The working fluid circulating in this circuit 142 is water here but could be one of the working fluids mentioned for circuit 130.This preheating heat exchanger 140 receives via a pipe 7 the preheated hydrocarbon charge coming out of the second heat exchanger 135 of the circuit. 130, for example at a temperature T10 of 120 °C, and heats it further to a temperature T13 before sending it through pipe 4 into the second heat exchanger 126 of the cooling section.

[0104] This embodiment differs from the previous one primarily in that the effluent exiting the heating section 110 is cooled and the components of the gas mixture are preheated. The working fluid circulates in circuit 130 as described with reference to Figure 1. The temperature ranges mentioned with reference to Figure 1 are applicable.

[0105] Thus, the effluent exiting at a temperature T4 from the reactor-exchanger 112 through the pipe 118 is first cooled to a temperature T15 in the first exchanger 124 by the cold working fluid circulating in the loop 142, here water in the liquid state. During its passage through this first heat exchanger 124, the water from circuit 142 vaporizes into water vapor at a temperature T12 and at high pressure, for example at 325 °C and 120 bar, and returns to the preheating heat exchanger 140 in which it preheats to a temperature T13 the hydrocarbon charge, here a naphtha, which has been previously heated (vaporized) from the temperature T9 of about 60 °C to the temperature T10 of about 120 °C in the second heat exchanger 135 of circuit 130. The water from circuit 142 then exits the preheating heat exchanger 140 at a temperature T14 and is vaporized in the first exchanger 124 by the effluent.The hydrocarbon feed preheated to temperature T13 exiting the preheating heat exchanger 140 via line 4 then joins line 2 in which the dilution steam from the first heat exchanger 134 of circuit 130 circulates. The gaseous mixture thus obtained is then sent via line 6 to the second heat exchanger 126 of the cooling section 120 in which it is heated to temperature T2 of approximately 600 °C by the partially cooled effluent from the first heat exchanger 124 of the cooling section 120.

[0106] Thus, the effluent at temperature T4 is abruptly cooled by the first heat exchanger 124, which provides superheated steam under pressure at a temperature T12. This superheated steam heats the vaporized hydrocarbons from a temperature T10 to T13 in the preheating heat exchanger 140.

[0107] For example, the temperature T12 can be from 300 to 450 °C, preferably from 310 to 380 °C, and even more preferably from 315 to 335 °C. The pressure of the superheated steam can then be from 10 MPa to 15 MPa, preferably from 11 to 14 MPa.

[0108] The temperature T13 can be from 220 to 300 °C, preferably from 230 to 270 °C, and even more preferably from 240 to 260 °C. T13 is higher than T10.

[0109] The superheated steam under pressure leaves the preheating heat exchanger 140 in condensed form at a temperature T14, less than or equal to T12, for example from 200 to 260 °C, preferably from 210 to 250 °C, more preferably from 220 to 240 °C.

[0110] The gaseous effluent exiting the first heat exchanger 124 of the cooling section is at a temperature T15, for example from 430 to 530, preferably from 440 to 520 °C, more preferably from 450 to 510 °C.

[0111] The embodiment shown in Figure 3 differs from that of Figure 1 primarily in the circuit 130, which supplies the hot working fluid to the heating section 100, and in the preheating of the hydrocarbon feed. The temperature ranges mentioned with reference to Figure 1 are applicable.

[0112] In this embodiment, circuit 130 comprises:

[0113] a heating device 133 for the working fluid, located upstream of the reactor-exchanger 112 relative to the working fluid circulation,

[0114] two heat exchangers 134', 135', here mounted in series, located downstream of the reactor-exchanger 112 and upstream of the heating device 133,

[0115] a device for circulating the working fluid 139.

[0116] Unlike the embodiment shown in Figure 1, in this embodiment, the first heat exchanger 134' of the circuit is used to preheat the working fluid of the circuit 130 before it enters the heating device 133, using the hot working fluid exiting, in particular, directly from the reactor-exchanger 112. Furthermore, the second heat exchanger 135' is used to preheat water supplied by a pipe 10 to a temperature T6. This water is then supplied by a pipe 11 to a preheating heat exchanger 150 of the installation, where it is vaporized under suitable conditions to form dilution steam at a temperature T7. This preheating heat exchanger 150 uses for this purpose a portion of the residual heat from the effluent exiting the heat exchanger 122 of the cooling section 120 via pipe 5.The preheating to temperature T10 of the hydrocarbon feed brought by line 3 to a temperature T9 is finally carried out by means of a second preheating heat exchanger 160 using for this purpose the residual heat of the cooled effluent exiting the first preheating heat exchanger 150 via a line 9. The cooled effluent is evacuated from the preheating heat exchanger 160 by a line 12, then brought to the usual subsequent sections of cooling, compression, fractionation to recover the products of interest.

[0117] In this embodiment, the working fluid circulation device 139 is a compressor or fan, this embodiment being more particularly suited to a gaseous working fluid, here CO2.

[0118] Thus, in this embodiment, the working fluid follows the following path in the circuit 130 comprising the lines 130'a-130'f. The compressor 139 sends the working fluid via the line 130'a to the heat exchanger 134' where it is preheated by the hot working fluid exiting the reactor-exchanger 112 through outlet 116. The preheated working fluid is then conveyed via the line 130'b to the heating device 133 where it is further heated, and then circulates in line 130'c before entering reactor-exchanger 112 through inlet 115, where it transfers heat to the tubes for the steam cracking reaction. Upon exiting reactor-exchanger 112, the working fluid at temperature T5 flows through line 130'd and then passes first through the first heat exchanger 134' before being conveyed via line 130'e to the second heat exchanger 135', where it is used to heat water. It is then conveyed to compressor 139 via line 130'f and returned by compressor 139 to the first heat exchanger 134' via line 130a.

[0119] The hydrocarbon feedstock is first preheated from temperature T9 to temperature T10 by the second preheating heat exchanger 160, using residual heat from the effluent exiting the first preheating heat exchanger 150. At the outlet of the second preheating heat exchanger 160, the hydrocarbon feedstock is mixed with dilution steam produced by the first preheating heat exchanger 150, which uses residual heat from the effluent exiting the heat exchanger 122 of the cooling section. The resulting gaseous mixture, at a temperature T1, is then further heated to a temperature T2 in this heat exchanger 122 before entering the reactor-exchanger tubes 112 through inlet 113, where the steam cracking reaction takes place.At the outlet of the reactor-exchanger 112, the hot effluent at a temperature T4 is rapidly cooled in the heat exchanger 122, then further cooled in the preheating heat exchangers 150 and 160, which heat respectively dilution steam and the hydrocarbon feed.

[0120] In this third embodiment, one or more heating devices 133 connected in series and / or parallel may be provided to heat the working fluid. Preferably, this heating device does not emit CO2 and may be as described previously. If water is used as the working fluid, the heating devices described with reference to Figure 1 may be used.

[0121] Figure 4 represents an embodiment similar to that described with reference to Figure 1, differing only in the presence of a liquid / vapor separation device 170 circulating in the conduit 130f of the circuit 130. The temperature ranges mentioned with reference to Figure 1 are applicable.

[0122] The liquid / vapor separation device 170 allows the vaporized part of the working fluid to be sent via a line 171a to a vapor recompressor 139 and the condensed part of the working fluid to be sent via a line 171b to a pump 138 and then to an electric heating device (e.g. boiler) 174. The recompressed / heated fluids are then brought by lines 172a and 172b respectively and combined before entering the heating device 132 via line 130b.

[0123] Of course, this embodiment providing for the liquid / vapor separation of the working fluid can also be implemented in each of the other embodiments of realization described when the working fluid is in the form of a liquid-vapor mixture before entering the heating device 132 or 133.

[0124] Figure 5 represents an embodiment which is a variant of the embodiment shown with reference to Figure 3. The temperature ranges mentioned with reference to Figure 1 are applicable.

[0125] In this embodiment, the working fluid follows the following path in the circuit 130. The liquid and vapor phases of the working fluid circulating in a line 130g are separated in a liquid-vapor separation device 170 into a vaporized portion and a liquid portion. The vaporized portion of the working fluid is sent via a line 171a to a compressor 139, the compressed fluid being conveyed to a line 130a via a line 172a. The condensed part of the working fluid is brought via a line 171b to a pump 138 and then via a line 172b to an electric heating device (e.g. a boiler) 174. The recompressed / heated fluids are then combined and conveyed via the line 130a to the first heat exchanger 134' of the circuit in which they are preheated by the hot working fluid exiting the reactor-exchanger 112 through the outlet 116 and the line 130d.The preheated working fluid is then conveyed to the heating device 132 via pipe 130b, where it is further heated to temperature T3. It then flows through pipe 130c and enters the reactor-exchanger 112 through inlet 115, where it transfers heat to the tubes to initiate the steam cracking reaction. Upon exiting the reactor-exchanger 112, the working fluid, at temperature T5, flows through pipe 130d and then passes first through the first heat exchanger 134' before being conveyed via pipe 130e to the second heat exchanger 135', where it is used to heat water or steam from temperature T6 to temperature T7. The working fluid is then brought via line 130f to a preheating heat exchanger 160 of the hydrocarbon feed before being returned via a line 130g to the separation device 170.

[0126] Figure 6 shows an embodiment that is a variant of the embodiment shown with reference to Figure 2. The cooling section 120 thus comprises two heat exchangers 124 and 126, while the hydrocarbon feed is preheated successively by a first preheating heat exchanger 160, which is not part of the closed-loop circuit 130, and then by a second preheating heat exchanger 140. The second preheating heat exchanger 140 is connected by another closed-loop circuit 142 to the first heat exchanger 124 of the cooling section. The temperature ranges mentioned with reference to Figures 1 and 2 are applicable.

[0127] In this embodiment, circuit 130 comprises:

[0128] a heating device 132 for the working fluid, located upstream of the reactor-exchanger 112 with respect to the working fluid circulation,

[0129] two heat exchangers 134', 135', here mounted in series, located downstream of the reactor-exchanger 112 and upstream of the heating device 132,

[0130] a device for circulating the working fluid 139.

[0131] In this embodiment, the working fluid is sent by the circulation device 139 via the line 130a to the first heat exchanger 134' where it is preheated by the working fluid to a temperature T5 exiting the heat exchanger reactor 112. It is then conveyed via the line 130b to the heating device 132 where it is heated to temperature T3. It is then brought to the inlet 115 of the heat exchanger reactor 112 via the line 130c where it supplies the gas mixture to be steam cracked with the heat necessary for the steam cracking reaction. It exits at a temperature T5 and is conveyed via the line 130d to the first heat exchanger 134' of the circuit and then via the line 130 eto the second heat exchanger 135' of circuit 130 in which it heats dilution steam from temperature T6 to temperature T7. The working fluid then returns via the line 130f to the circulation device 139.

[0132] Furthermore, the effluent exiting the reactor-exchanger 112 at a temperature T4 via the pipe 118 is first cooled to a temperature T15 in the first heat exchanger 124 of the cooling section by the cold working fluid circulating in the loop 142, here liquid water. During its passage through this first heat exchanger 124, the water from circuit 142 vaporizes into water vapor at a temperature T12 and at high pressure, for example at 325 °C and 120 bar, and returns to the second preheating heat exchanger 140 where it preheats the hydrocarbon feed, here naphtha, to a temperature T13. This feed has been previously heated (vaporized) from a temperature T9 of approximately 60 °C to a temperature T10 of approximately 120 °C in the first heat exchanger 160.The preheated hydrocarbon feed exiting the second preheating heat exchanger 140 via line 4 then joins line 2 in which the dilution steam at a temperature T7 flows from the second heat exchanger 135' of circuit 130. The gaseous mixture thus obtained is then sent via line 6 to the second heat exchanger 126 of the cooling section 120 in which it is heated to a temperature T2 of approximately 600 °C by the partially cooled effluent from the first heat exchanger 124 of the cooling section 120.

[0133] In the various embodiments, alternative arrangements of one or more heating devices may be provided, provided that they enable the working fluid to be heated to a sufficiently high target temperature so that the gas mixture circulating within at least one heat exchanger-reactor reaches the desired reaction temperature. Those skilled in the art can determine this target temperature through testing and / or modeling, based on the feedstock to be steam cracked and the characteristics of the heat exchanger-reactor.

[0134] It should also be noted that the preheating of the hydrocarbon charge as described with reference to Figure 2 can also be implemented in the embodiment of Figure 3. In this case, the preheating heat exchanger 140 described with reference to Figure 2 is arranged immediately downstream of the second preheating heat exchanger 160.

[0135] In the embodiments described above, the circuit 130 comprises two heat exchangers. However, the invention is not limited to this preferred embodiment, and a single heat exchanger or more than two heat exchangers may be provided. Advantageously, all the heat exchangers used in the present invention are shell-and-tube heat exchangers, for example, of the type described above.

[0136] The present invention thus consists of using the working fluid as a heat transfer fluid (such as CO2, steam, argon, helium, etc.) which is heated by a CO2-free heating device to a target temperature, typically above 900 °C, generally under increased pressure (>20 bar), and sent to a heat exchanger reactor, preferably to its shell, where it exchanges heat, preferably with the tubes in which the steam cracking reaction takes place. Subsequently, the heat transfer fluid, having lost temperature, is used to vaporize and / or preheat the feedstock, the dilution steam, or both, and is finally recovered at a reduced temperature and pressure (due to the pressure drop across the heat exchanger equipment).This heat transfer fluid at reduced temperature and pressure is repressurized by compression or pumping (in case of fluid condensation), heated using the heating device to the target temperature to close the cycle.

[0137] The invention thus offers the following advantages:

[0138] Decarbonizing the steam cracking of hydrocarbons to manufacture basic chemicals using one or more heating devices that do not emit CO2, and preferably using renewable electricity, without emitting greenhouse gases,

[0139] Improved control of tube skin temperature in the heat exchanger reactor, allowing for limited coking,

[0140] a compact installation, a heat exchanger reactor being much more compact than the combustion furnaces usually used, because the heat exchange occurs mainly by high-pressure convection, which requires much less volume, especially on the calender side.

[0141] Examples

[0142] Example 1: Steam as a heat transfer fluid

[0143] A heat and mass balance is modeled using the Aspen Technology software package according to the configuration shown in Figure 5. The installation includes a hydrocarbon charge vaporizer / heater 160, a heat exchanger charge-effluent 122, a reactor - heat exchanger for cracking the charge 112, an electric heater 132 of the steam used as working fluid (heat transfer fluid), a first steam economizer heat exchanger 134', a second dilution steam superheater heat exchanger 135', a steam-condensate separator 170, a steam recompressor 139, a condensate pump 138 and an electric condensate boiler 174.

[0144] Steam, as a heat transfer fluid, operates at a pressure of approximately 33 to 35 barg and the pressure drop in the installation is compensated by the recompressor 139 and the condensate pump 138. The temperatures, pressures, flow rates, enthalpy fluxes and loads for a production capacity of 1000 kg / h are shown in Table 1.

[0145] Table 1

[0146] Example 2: CO2 as a heat transfer fluid

[0147] A heat and mass balance is modeled using the Aspen Technology software package according to the configuration shown in Figure 3. The installation includes (160) a hydrocarbon feed vaporizer / heater, (122) a feed-effluent heat exchanger, (112) a feed cracking heat exchanger reactor, (133) an electric heater for CO2 as a heat transfer fluid, (134') an economizer heat exchanger, (135') a dilution steam superheater heat exchanger, (150) a dilution steam heating heat exchanger and (139) a CO2 booster.

[0148] The CO2, used as the heat transfer fluid, operates at a pressure of approximately 74 to 78 barg, and the pressure drop is compensated by the CO2 booster (139) (which can be a suitable pump or compressor type booster). Temperatures, pressures, flow rates, enthalpy fluxes, and loads for a production capacity of 1000 kg / h are shown in Table 2.

[0149] Table 2 Tl

[0150] Example 3: Argon as a heat transfer fluid.

[0151] A heat and mass balance is modeled using the Aspen Technology software package according to the configuration shown in Figure 3. The installation includes (160) a hydrocarbon feed vaporizer / heater, (122) a feed-effluent heat exchanger, (112) a feed cracking heat exchanger reactor, (133) an electric argon heater (for the heat transfer fluid), (134') an economizer heat exchanger, (135') a dilution steam superheater heat exchanger, (150) a dilution steam heating heat exchanger, and (139) an argon blower.

[0152] Argon, used as the heat transfer fluid, operates at a pressure of approximately 74 to 78 barg, and the pressure drop in the system is compensated by the compressor (32 bar). Temperatures, pressures, flow rates, enthalpy fluxes, and loads for a production capacity of 1,000 kg / h are shown in Table 3.

[0153] Table 3

[0154] These examples demonstrate that the required thermal power (approximately 2166 kW for a production capacity of 1000 kg / h of ethylene from naphtha in the reactor - heat exchanger) can be supplied by a circulating heat transfer fluid, which can be heated to the appropriate temperature using electric heaters.

[0155] A person versed in the art will understand that several configurations (including others than those described in Figures 1 to 6) of thermal integration between the heat transfer working fluid on the one hand and the heating system for the dilution steam and hydrocarbon feed on the other hand are conceivable in the present invention.

Claims

DEMANDS

1. Steam cracking plant (100) comprising: at least one shell and tube heat exchanger reactor (112), each heat exchanger reactor comprising means for supplying (117) a suitable gaseous mixture comprising at least one hydrocarbon and dilution steam, connected to an inlet selected from a tube inlet (113) and a shell inlet (115), and means for discharging (118) a hot gaseous effluent connected to a corresponding outlet (114, 116) of the tubes or the shell, a cooling section (120) adapted for quenching, connected to the discharge means of each heat exchanger reactor, characterized in that it further comprises: at least one closed-loop circuit (130) through which circulates a working fluid selected from water, CO2, helium, nitrogen or argon,This circuit being connected on one side to the other inlet of at least one heat exchanger reactor chosen from an inlet (113) of the tubes and an inlet (115) of the shell, and on the other side to the corresponding outlet (114, 116) of the tubes or the shell, each circuit (130) comprising: at least one heating device (131, 132; 133) for the working fluid located upstream of the inlet connecting said circuit to at least one heat exchanger reactor (112) with respect to the working fluid circulation, at least one heat exchanger (134, 135; 134', 135') located downstream of at least one heat exchanger reactor (112) and upstream of at least one heating device (131, 132; 133), at least one fluid circulation device (138, 139) work.

2. Steam cracking installation (100) according to claim 1, characterized in that at least one closed-loop circuit (130) is connected to the shell of at least one heat exchanger reactor.

3. Steam cracking installation (100) according to claim 1 or 2, characterized in that at least one closed loop circuit (130) comprises at least two heating devices mounted in series and / or in parallel.

4. Steam cracking installation according to any one of the preceding claims, characterized in that at least one heating device is selected from a Joule effect heating device, a microwave heating device, a shock wave heating device, a plasma heating device, an induction heating device, a heat pump, a hydrogen furnace.

5. Steam cracking installation according to any one of claims 1 to 4, characterized in that the cooling section (120) comprises a heat exchanger (122) connected on the one hand to the exhaust means (118) of at least one heat exchanger reactor (112) and on the other hand to the supply means (117) of at least one heat exchanger reactor so as to preheat the gas mixture entering the latter by means of the gas effluent exiting the latter, and in that this heat exchanger (122) is connected to at least one heat exchanger (134, 135) of the closed-loop circuit (130) to receive at least one component of the preheated mixture.

6. Steam cracking installation according to any one of claims 1 to 5, characterized in that the at least one closed-loop circuit (130) comprises a first (134) and a second (135) heat exchangers mounted in series downstream of the at least one heat exchanger reactor (112) with respect to the direction of flow of the working fluid, the first heat exchanger (134) being connected to a water supply line (1) and adapted to heat it, and the second heat exchanger (135) being connected to a supply line (3) of a component of the gas mixture and adapted to preheat it before its entry into the at least one heat exchanger reactor (112) or before its entry into a heat exchanger (122) of the cooling section.

7. A steam cracking plant (100) according to any one of claims 1 to 4, characterized in that at least one closed-loop circuit (130) comprises a first (134') and a second (135') heat exchangers mounted in series downstream of at least one heat exchanger-reactor with respect to the direction of flow of the working fluid, the first heat exchanger (134') being connected to the circuit (130), with respect to the direction of flow of the working fluid, on the one hand upstream of at least one heating device (133) and downstream of the second heat exchanger (135'), and on the other hand downstream of at least one heat exchanger-reactor (112) and upstream of the second heat exchanger (135'), the second heat exchanger (135') being connected to a water supply line (10) and adapted to preheat this water by means of of the working fluid.

8. Steam cracking plant (100) according to claim 7, characterized in that: the cooling section (120) comprises a heat exchanger (122) connected on the one hand to the exhaust means (118) of at least one heat exchanger reactor and on the other hand to the feed means (117) of at least one heat exchanger reactor so as to preheat the gas mixture entering the latter by means of the gaseous effluent exiting the latter, and the plant further comprises at least two heat exchangers preheating (150, 160): the first preheating heat exchanger (150) being connected on one side to the heat exchanger (122) of the cooling section to receive the cooled gaseous effluent and on the other side to the second heat exchanger (135') of the closed loop circuit (130) to further heat and vaporize the water exiting the latter, the second preheating heat exchanger (160) being connected on one side to the heat exchanger (122) of the cooling section to supply it with a component of the heated gaseous mixture and on the other side to the first preheating heat exchanger (150) to receive the further cooled gaseous effluent.

9. A steam cracking plant (100) according to any one of claims 1 to 5, characterized in that the cooling section comprises a first and a second heat exchanger connected in series: the first heat exchanger (124) being connected on the one hand to the exhaust means (118) of at least one heat exchanger reactor (112) and on the other hand to a preheating heat exchanger (140) located upstream of the at least one heat exchanger reactor (112) with respect to the fluid circulation, so as to preheat a component of the gas mixture, the second heat exchanger (126) being connected on the one hand to the first heat exchanger (124) and on the other hand to the preheating heat exchanger (140) and to at least one heat exchanger (134) of the closed-loop circuit (130), to receive at least one component thereof of the preheated mixture.

10. A steam cracking process for a gaseous mixture of a hydrocarbon feedstock and steam, suitable for implementation by a steam cracking plant according to any one of the preceding claims, said process comprising a heating phase in a heating section under suitable conditions, which delivers a hot steam cracking effluent, and a rapid cooling phase of said effluent in a cooling section (120) under suitable conditions, and the cooled steam cracking effluent is recovered, characterized in that: - the gas mixture, preferably pre-heated, is introduced into at least one pressure shell and tube heat exchanger reactor (112) via an inlet of the latter chosen from an inlet (113) of the tubes and an inlet (115) of the shell, and the gas mixture is circulated inside the tubes or the shell of said heat exchanger reactor (112), the heating phase of the gas mixture in the at least one heat exchanger reactor (112) is carried out according to the following steps: (a) A working fluid selected from water, CO2, helium, nitrogen or argon is circulated within a closed-loop circuit (130), this circuit being connected at one end to the other inlet of at least one selected heat exchanger reactor between an inlet (113) of the tubes and an inlet (115) of the shell, and on the other hand to the corresponding outlet (114, 116) of the tubes or of the shell, and said working fluid is heated to a target temperature higher than the temperature to which the gas mixture is to be heated by means of at least one heating device (131, 132; 133) of said circuit (130), (b) the working fluid at the target temperature is introduced into the heat exchanger reactor (112) via the inlet (115) which connects it to said circuit (130), the cooled working fluid is recovered at the outlet (116) of the heat exchanger reactor (112) and reinjected into the closed loop circuit (130) upstream of at least one heating device (131, 132; 133) of said circuit, and a hot steam cracking effluent is recovered and sent immediately to the cooling section (120).

11. Method according to claim 10, characterized in that the gas mixture is circulated inside the tubes of at least one heat exchanger reactor (112).

12. A process according to claim 10 or 11, characterized in that it comprises at least one of the following features: the target temperature of the working fluid is from 900 to 1600 °C, preferably from 1000 to 1400 °C, more preferably from 1100 to 1300 °C, even more preferably from 1150 to 1250 °C, the pressure of the working fluid is from 30 barg to 80 barg.

13. A method according to any one of claims 10 to 12, characterized in that the gaseous effluent having circulated in at least one heat exchanger reactor (112) is recovered and sent to at least one heat exchanger (122; 124, 126) of the cooling section (120) to cool it rapidly and preheat the gaseous mixture before it enters at least one heat exchanger reactor (112).

14. A method according to any one of claims 10 to 12, characterized in that the working fluid that has circulated in at least one heat exchanger reactor (112) is recovered and sent to at least one heat exchanger of the closed-loop circuit (130) in which at least one fluid selected from (i) at least one constituent of the gas mixture is preheated before its entry into at least one heat exchanger reactor or before its entry into at least one heat exchanger of the cooling section (120), (ii) water, (iii) steam, and (iv) the working fluid is preheated before its entry into at least one heat exchanger reactor (112).

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