Steam cracking facility and method comprising a reactor heat exchanger using a thermal storage system

Abstract

The invention relates to a facility and method for steam cracking using at least one reactor heat exchanger. The heat required for the steam cracking reaction is provided by a working fluid circulating in at least one closed-loop circuit (130), connected to an inlet of the reactor heat exchanger (112) and to the corresponding outlet, and comprising: at least one heating device (131, 132) upstream of the reactor heat exchanger (112) with respect to the circulation of the working fluid, at least one thermal storage system (170) mounted in parallel with or downstream of the at least one heating device, and upstream of the reactor heat exchanger, at least one heat exchanger (134, 135) located downstream of the reactor heat exchanger (112), and upstream of the at least one heating device (131, 132), at least one circulating device (138).

Description

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

[0001] The present invention relates to a steam cracking installation and process employing at least one heat exchanger reactor and using a thermal storage system. 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, resulting in significant CO2 emissions. Furthermore, in conventional steam cracking furnaces, the heat from gas combustion is transferred to the tubes carrying the cracked material 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, promoting coking of the reaction tubes and 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 The process takes place within 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 carried out inside 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 steam cracking feedstock is preheated before entering the heat exchanger reactor. To maintain a relatively constant temperature in the reaction tubes, injection tubes are located inside the heat exchanger reactor.

[0007] The process described in this document has the drawback of requiring the combustion of gases that emit CO2. Furthermore, since part of the gas combustion occurs inside the heat exchanger reactor, additional devices must be incorporated into the reactor to achieve a uniform temperature, thus complicating its manufacture.

[0008] The invention aims to overcome all or part of the disadvantages of the prior art. 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 thermal storage system coupled to the circuit via a bypass pipe, and mounted in parallel with or downstream of at least one heating device, and upstream of at least one heat exchanger reactor,

[0016] at least one heat exchanger located downstream of at least one heat exchanger reactor and upstream of at least one heating device,

[0017] at least one device for circulating the working fluid,

[0018] a management system for at least one closed-loop heating device and at least one thermal storage device, configured to: (i) during a charging phase of at least one thermal storage system, operate at least one heating device of said circuit to heat the working fluid to a target temperature, and accumulate heat within at least one thermal storage system, (ii) in a discharge phase of at least one thermal storage system: circulate through the at least thermal storage system all, or a fraction, of the working fluid flow circulating in said circuit to heat it to the target temperature, or a first temperature, respectively, and stop at least one heating device of said circuit, or command it to heat to a second temperature the remaining fraction of the working fluid flow which, in mixing with the fraction of working fluid at the first temperature, reaches the target temperature.

[0019] Thus, there is no combustion inside the heat exchanger reactor, allowing for a simplified structure and limiting the risk of hot spots. In other words, the heat exchanger reactor used in the present invention is not designed to produce heat by combustion; it is of the recuperative type, meaning it is 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. Therefore, a cooler fluid, circulating in the shell or tubes, recovers some of the heat from a warmer fluid, circulating in the tubes or the shell respectively, by heat transfer across a separating wall.

[0020] The gas mixture to be steam cracked typically comprises, or is even made up of, at least one hydrocarbon and dilution steam. The dilution steam, also called dilution steam or steam hereafter, can be produced by any conventional means and can be mixed with the at least one hydrocarbon in proportions suitable for steam cracking by any suitable conventional means.

[0021] In addition, the use of one or more thermal storage systems makes it possible to use electricity when it is cheaper and / or produced from renewable sources to accumulate calories within at least one thermal storage system, and thus limit the overall cost and / or the ecological footprint of the heating required for the steam cracking reaction.

[0022] At least one thermal storage system may include, or be composed of, one or more thermal storage devices, each containing a solid or liquid thermal storage medium. This system may optionally include one or more electric heating devices, whether or not integrated into the system. Thermal storage device(s). The management system is then configured to operate this electric heating device during the charging phase for heat accumulation. The electric heating device for the thermal storage system can be chosen from among a Joule effect heater, a microwave heater, a shock wave heater, a plasma heater, an induction heater, or a heat pump.

[0023] 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.

[0024] 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. Optionally, one or more thermal storage systems may be coupled to said circuit and connected in parallel or downstream of at least two of these heating devices, and upstream of at least one heat exchanger reactor relative to the direction of flow of the working fluid.

[0025] Preferably, at least one heating device in said circuit 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.

[0026] The heating device for said circuit may be in the form of a boiler, a furnace or a superheater, preferably not emitting CO2.

[0027] Advantageously, at least one heating device for said circuit may be chosen 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, or a hydrogen furnace.

[0028] 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.

[0029] Advantageously, at least one heat exchanger in the cooling section can be connected to at least one heat exchanger in the circuit to receive at least one component of the preheated gas mixture. This notably improves the overall energy performance of the installation.

[0030] 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.

[0031] Advantageously, in another embodiment allowing for improvement of the overall energy performance of the installation, the at least one closed-loop circuit comprises a first and a second heat exchanger mounted in series downstream of the 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 the at least one heating device, and downstream of the second heat exchanger, and on the other hand downstream, in particular immediately downstream, of the at least one heat exchanger reactor and upstream of the second heat exchanger, the second heat exchanger being connected to a water supply line, in particular 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] In one variant, the second heat exchanger of the closed loop circuit 130 can be connected to the preheating heat exchanger in order to supply it with the constituent of the gas mixture preheated by the working fluid.

[0038] 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 ethylene, and a rapid cooling phase of said effluent in a cooling section under suitable conditions, and the cooled steam cracking effluent is recovered.

[0039] According to the invention: - the gas mixture, preferably pre-heated, 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 in at least one heat exchanger reactor is carried out 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 chosen from a tube inlet and a shell inlet, and on the other side to the corresponding outlet of the tubes or shell, and said working fluid is heated to a target temperature higher than the temperature to which the gas mixture must be heated, in particular before entering the at least one heat exchanger reactor, by means of at least one closed-loop circuit heating device and / or by means of at least one thermal storage system of said circuit in the following manner: (i) in a charging phase of at least one thermal storage system, at least one heating device of said circuit is operated to heat the working fluid to the target temperature, and heat is accumulated within at least one thermal storage system, (ii) in a discharge phase of at least one thermal storage system: the entire, or a fraction, of the working fluid flow circulating in said circuit is circulated through the at least thermal storage system to heat it to the target temperature, or to a first temperature, respectively, and at least one heating device of said circuit is stopped, or is controlled to heat to a second temperature the remaining fraction of the working fluid which, in mixing with the fraction of working fluid at the first temperature, reaches the target temperature, (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.

[0040] In particular, it is possible to operate the thermal storage system in load mode when electricity is cheaper and / or comes from decarbonized sources (wind, solar, nuclear power plant, hydroelectric, ...), which makes it possible to decarbonize the electrical consumption of the installation and / or reduce operating costs.

[0041] When at least one storage system includes at least one electric heating device, during the charging phase, it can be operated to accumulate calories, and optionally stopped during the discharging phase.

[0042] Advantageously, the gas mixture can be circulated inside the tubes of at least one heat exchanger reactor.

[0043] Advantageously, the method according to the invention may further comprise at least one of the following features:

[0044] - The working fluid is chosen from water, CO2, helium, nitrogen, or argon; the target temperature of the working fluid is 900 to 1600 °C, preferably At 1000 to 1400 °C, the working fluid pressure is 30 barg to 80 barg.

[0045] Advantageously, the gaseous effluent that has circulated in at least one heat exchanger reactor can be recovered and sent to at least one heat exchanger in the cooling section to rapidly cool and preheat the gas mixture to be steam cracked before it enters at least one heat exchanger reactor.

[0046] 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.

[0047] In particular, the following implementation methods can be envisaged:

[0048] - the working fluid having circulated in at least one reactor-heat exchanger 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, then the working fluid is sent to a second heat exchanger of said circuit to heat another constituent of the gas mixture (e.g. hydrocarbons), in particular before preheating it (typically mixed with steam) in a heat exchanger of the cooling section.

[0049] - 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.

[0050] - 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 heat steam, specifically before the steam is preheated in a heat exchanger in the cooling section. The working fluid is then sent to a second heat exchanger in the same circuit to heat another The component of the gas mixture (particularly hydrocarbons) is fed into at least one heat exchanger reactor. The hot effluent, having circulated through the reactor, is then sent to a first and a second heat exchanger connected in series in the cooling section. The second heat exchanger in the cooling section typically receives, in a mixture, 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 heat exchanger of the cooling section by another closed-loop circuit in which another working fluid circulates, typically water in liquid and / or vapor form.

[0051] 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

[0052] The invention is now described with reference to the accompanying, non-limiting drawings, in which:

[0053] Figure 1 schematically represents a steam cracking installation according to a first embodiment,

[0054] Figure 2 schematically represents a steam cracking installation according to a second embodiment,

[0055] Figure 3 schematically represents a steam cracking installation according to a third embodiment.

[0056] In the figures, the same elements are designated by the same references.

[0057] Figure 1 represents a steam cracking installation 100 comprising a heating section 110 in which the steam cracking reaction takes place, comprising at least one shell and tube heat exchanger reactor 112, here only one, and a cooling section 120 for the hot gaseous effluent containing the cracked gases exiting the heating section 110.

[0058] 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.

[0059] The reactor-exchanger 112 further includes means for supplying a suitable gaseous mixture comprising at least one hydrocarbon and steam dilution. These supply means include here a conduit 117 connected in this example to the inlet 113 of the tubes.

[0060] The reactor-exchanger 112 also includes means for venting the hot gaseous effluent. These venting means include a pipe 118 connected in this example to the outlet 114 of the tubes.

[0061] 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.

[0062] A reactor-exchanger 112 typically has an elongated shape, usually arranged vertically.

[0063] In general, the reactor-exchanger 112 contains a plurality of reaction tubes, usually of small diameter, for example, 10 to 40 mm. A reactor-exchanger can contain a thousand tubes of approximately 20 mm in diameter, for example, made of Incoloy-type steel with a high nickel content. These tubes are typically substantially parallel to each other and substantially parallel to the axis of the reactor-exchanger. However, the invention is not limited to a specific shape and arrangement of the tubes.

[0064] These tubes for example are adapted to receive, by means of a parallel supply, a mixture preheated to 580-680 °C under 1.5 to 3 bar, of steam and hydrocarbons by the line 117 opening at the lower end of the reactor 112, so that 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.

[0065] The cooling section 120 adapted to carry out quenching is connected to the evacuation means 118 of the exchange reactor 112.

[0066] In this embodiment, the cooling section includes a heat exchanger 122 receiving the gaseous effluent from the reactor-exchanger 112.

[0067] 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 1115 of the shell of the reactor-exchanger 112 and on the other side to the corresponding outlet 116 of the shell.

[0068] This circuit 130 includes in this embodiment:

[0069] 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,

[0070] a thermal storage system 170 coupled to the circuit 130 via a bypass pipe 172 and mounted downstream of the heating devices 131, 132, and upstream of at least one heat exchanger reactor 112,

[0071] two heat exchangers 134, 135, here mounted in series, located downstream of the reactor-exchanger 112 and upstream of the heating devices 131, 132,

[0072] a device for circulating the working fluid 138,

[0073] a management system 180 of the heating devices 131, 132 of the circuit and of the thermal storage device 170.

[0074] This 180 management system is configured, specifically programmed, to: (i) in a charging phase of the thermal storage system 170, operate the heating devices 131, 132 of circuit 130 to heat the working fluid to a target temperature, here 1200 °C, and accumulate heat within the thermal storage system 170, (ii) in a discharge phase of the thermal storage system 170: circulate through the thermal storage system 170 all, or a fraction, of the working fluid flow circulating in the circuit 130 to heat it to the target temperature, or a first temperature, respectively, and stop at least one heating device 131, 132 of the circuit 130, or command it to heat to a second temperature the remaining fraction of the working fluid flow which, in mixing with the fraction of working fluid at the first temperature, reaches the target temperature.

[0075] Regardless of the closed-loop circuit's design and the number and arrangement of the heating and storage devices in said circuit, during the charging phase, heat can be accumulated within the thermal storage system in various ways. For example, a portion of the working fluid at the target temperature can be circulated through the thermal storage system. If the latter includes an electric heating device, this can potentially be used to further heat the working fluid. Alternatively, a portion of the working fluid taken from a point in the circuit where it is not at the target temperature, for example, upstream of at least one of the heating devices, can be circulated through the thermal storage system and further heated using the electric heating device of the thermal storage system.Furthermore, when multiple thermal storage systems are present, they will be able to accumulate calories in different ways, independently of each other.

[0076] It is also possible to configure the 180 management system to operate the thermal storage system in load mode when electricity is cheaper and / or sourced from decarbonized sources (wind, solar, nuclear power, hydroelectric, etc.), which allows for the decarbonization of the installation's electricity consumption and / or reduces operating costs. This also applies to all embodiments described in this application.

[0077] The thermal storage system 170 typically comprises, or consists of, one or more thermal storage devices, for example, one or more insulated enclosures, each containing a solid or liquid thermal storage medium. This system may optionally include one or more electric heating devices 176, integrated or not with the thermal storage devices. In this case, the electric heating device may be selected from a Joule heating device, a microwave heating device, a shock wave heating device, a plasma heating device, or an induction heating device.

[0078] The thermal storage medium (liquid or solid) advantageously has suitable thermal storage capacities and / or is capable of achieving suitable heat transfer rates for the intended use.

[0079] Solid thermal storage media can be in the form of powders, particles, or solid blocks with open cavities and / or channels. Suitable heat transfer solids include volcanic rocks or refractory materials such as alumina. A thermal storage device containing volcanic rocks produced by Brenmiller Energy can be used. Alternatively, stacked refractory materials can be used. The storage device could, for example, be similar to a glass furnace regenerator and contain a stack of refractory materials, which could be cruciform, brick, bushel, or pot shapes.Electrically conductive refractory bricks can also be used, which can be heated by the circulation of gas and / or by an electric current passing through the bricks during the charging of the thermal storage (for example, Joule Hive Thermal Battery refractory bricks).

[0080] The liquid storage medium can advantageously be chosen from ionic liquids, salts such as potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), sodium nitrate (NaNO3), sodium nitrite (NaNO2), and lithium nitrate, alone or in mixtures, such as a mixture of sodium nitrate and potassium nitrate or a eutectic mixture of sodium nitrate and potassium nitrate, and salt-water systems in which the salts form hydrates, such as lithium bromide. Preferably, the liquid medium can be chosen from salts such as potassium nitrate, calcium nitrate, sodium nitrate, sodium nitrite, and lithium nitrate, alone or in mixtures. For example, one could use a eutectic mixture containing 60% by mass of sodium nitrate and 40% by mass of potassium nitrate (KNO3), also called "Solar Salt", or a mixture containing 7% by mass of NaNO3, 53% by mass of KNO3 and 40% by mass of NaNCh, or a mixture containing 48% by mass of Ca(NOa)2, 45% of KNO3 and 7% of NaNO2.

[0081] The position of the thermal storage system(s) 170 in the circuit 130 can thus be chosen according to the temperature attainable by the thermal storage medium. For example, in the case of refractory brick storage that can be maintained at 1200 °C, the thermal storage system can be positioned downstream of the heating devices 131, 132, as shown in Figure 1. In the case of molten salt storage that can be maintained at a temperature of approximately 500 °C, the thermal storage system will be positioned further upstream, for example between the two heating devices 131, 132, or in parallel with the heating device(s) 131, 132.

[0082] A valve 174 can be positioned to connect the bypass line 172 to the circuit 130 to facilitate the management of the working fluid flow rate circulating in this bypass line during the charging and discharging phases. This valve 174 is ideally controlled by the management system 180.

[0083] The control system 180 used in the present invention typically comprises one or more processors, for example, a microprocessor, a microcontroller, or the like. It can be configured (in particular, programmed) to control the heating and thermal storage devices of circuit 130, as well as the electric heating device(s) of the thermal storage system, if present. It can thus be connected to these components, and optionally to one or more valves, fans, pumps, or other elements used for fluid circulation and flow regulation, and / or to the power supply of the components and / or to the control of these components.

[0084] The 180 management system can also receive various types of information from one or more appropriately positioned sensors:

[0085] - to the energy supply (electrical and / or thermal) of each heating device in circuit 130, and possibly of the thermal storage system (quantity of current received and consumed, temperature and / or flow rate of fluids whose temperature is controlled),

[0086] - the charging and discharging state of each thermal storage system (temperature of the thermal storage devices),

[0087] - to the phase in which each thermal storage system is located (charging, discharging),

[0088] - to the amount of electrical and / or thermal energy received / produced by each electric heating device / thermal storage system (quantity of current, flow rate and / or temperature of fluids).

[0089] The 180 management system typically includes output or input / output interfaces. These can be wireless communication interfaces (Bluetooth, Wi-Fi, or other) or connectors (network port, USB port, serial port, FireWire® port, SCSI port). or other). These input and / or output interfaces can form means of communication, optionally bidirectional, between the management system and the circuit heating device(s) and the thermal storage system(s).

[0090] The 180 management system may also include storage means such as random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), flash memory, external memory, or other storage devices. These storage means can, among other things, store received data, measured values, calculated values, and one or more computer programs.

[0091] In the embodiment shown in Figure 1, the first heat exchanger 134 is used to heat steam to obtain a 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 the 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.

[0092] In this embodiment, the first heating device 131 is an electric boiler and the second heating device 132 is an electric superheater.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] The steam cracking of a hydrocarbon feedstock using the installation shown in Figure 1 is now described.

[0097] 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.

[0098] Typically, at the inlet of heating section 110, the temperature of the gas mixture can be 600 to 680 °C. The temperature of the gas effluent at the outlet of heating section 110 is typically 800 to 900 °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 maintained, for example, at a pressure of 1.5 to 3 bar.

[0099] 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.

[0100] The working fluid follows the following path in circuit 130. Pump 138 sends the working fluid, here liquid water, 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), during a charging phase of the thermal storage system 170, enters the superheater 132 and exits superheated, for example, at 1200 °C. A fraction of the flow of this superheated working fluid is then sent to the bypass line 172 via valve 174 to pass through the storage system 170. During a discharging phase of the thermal storage system, the superheater 132 can be operated at reduced capacity or shut down, and the working fluid can be circulated through the storage system 170 to superheat it.The superheated working fluid then enters the reactor-exchanger shell 112 through inlet 115 and circulates inside it. The superheated working fluid cools during its... The working fluid passes through the reactor-exchanger 112 as it transfers its heat to the reactor-exchanger tubes. The working fluid thus exits at a temperature lower than its inlet temperature, here approximately 700 °C. At the outlet of the reactor-exchanger, the working fluid is sent, notably directly, to the first heat exchanger 134. This exchanger receives steam, for example at 180 °C, from a line 1, which it heats, for example, to 500 °C. The dilution steam exiting the first heat exchanger 134 is discharged through a line 2 that joins a line 4 through which the hydrocarbon feedstock circulates. Thus, the first heat exchanger 134 brings steam to a temperature suitable for use as dilution steam, to be mixed with the hydrocarbon feedstock to be steam cracked before it enters the heat exchanger 122.The working fluid, cooled by its passage through the first heat exchanger 134, here at a temperature of approximately 200 °C, is then sent to the second heat exchanger 135 where it performs an initial preheating of the hydrocarbon feed supplied via a line 3. At the outlet of this second heat exchanger 135, the working fluid, here water, is again in a liquid state and returned by the pump 138 to the first heating device 131. The second heat exchanger 135 can, for example, heat naphtha from 60 °C to 120 °C (naphtha in vapor form), which is then mixed with the dilution steam at 500 °C exiting the first heat exchanger 304 of circuit 30. The resulting mixture can reach a temperature of approximately 300 °C and is then preheated to approximately 600 °C as it passes through the heat exchanger. 122 used to perform a quenching of the gaseous effluent.The gas mixture then enters the tubes of the reactor-exchanger 112 through inlet 113. These tubes are heated primarily by convection, to approximately the temperature of the working fluid circulating in the calender. The working fluid can flow in the same direction as the gas mixture in the tubes, which promotes 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 pipe 118 to the heat exchanger 122, where it is cooled by the gas mixture. From the outlet of the heat exchanger 122, a pipe 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 detailed further.

[0101] The invention is, of course, not limited by the nature of the hydrocarbons that can be steam cracked. The installation and 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 fuel, and vacuum distillates; and of various hydrocarbon feedstocks of biological origin, such as ethane, propane, butanes, naphtha, and distillates produced during the hydrotreating / hydrocracking of fatty acid esters (e.g., triglycerides), biomass pyrolysis oils and / or biomass hydrothermal liquefaction oils, or other hydrocarbon fillers obtained by pyrolysis, hydrothermal liquefaction and / or hydrocracking of plastic waste.

[0102] The embodiment shown in Figure 2 differs from that of Figure 1 primarily in the cooling section 120, the preheating of the hydrocarbon feedstock, and the number of thermal storage systems. In this embodiment, the cooling section 120 comprises a first heat exchanger 124 and a second heat exchanger 126 connected in series: the effluent exiting the reactor-exchanger 112 via outlet 114 and line 118 first passes through the first heat exchanger 124 and then the second heat exchanger 126 before being sent via line 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 the preheated hydrocarbon charge coming out of the second heat exchanger 135 of circuit 130, for example at a temperature of 120 °C, and heats it further before sending it through line 4 into the second heat exchanger 126 of the cooling section.

[0103] 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.

[0104] In this embodiment, two thermal storage systems 170, 170' are provided. A first thermal storage system 170 is arranged as in the embodiment of Figure 1. The second thermal storage system 170' is mounted in parallel with the second heating device 132. For this purpose, its bypass line 172' is connected, on the one hand via a valve 174', to the portion of circuit 130 linking the two heating devices 131, 132, and on the other hand to the portion of circuit 130 located between the second heating device 132 and the first thermal storage system 170. The second thermal storage system 170' may also include an electric heating device 176', integrated or not. In this case, during the charging phase, a fraction of the working fluid flow rate will be circulated through each storage system 170, 170' to accumulate heat.During the discharge phase, each of the thermal heating devices 131, 132 can then be operated at reduced speed, or stopped, while part or all of the working fluid flow circulating in the circuit 130 passes through the two thermal storage systems 170, 170'.

[0105] In this embodiment, the effluent exiting the reactor-exchanger 112 via the pipe 118 is first cooled in the first exchanger 124 by the working fluid Cold water circulates in loop 142, here liquid water. As it passes through this first heat exchanger 124, the water in circuit 142 vaporizes into high-pressure steam, for example at 325 °C and 120 bar, and returns to the preheating heat exchanger 140 where it preheats the hydrocarbon feed, here naphtha, which has been previously heated (vaporized) from approximately 60 °C to approximately 120 °C in the second heat exchanger 135 of circuit 130. The preheated hydrocarbon feed 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 to the second heat exchanger 126 of the cooling section 120 in which it is heated to about 600 °C by the partially cooled effluent from the first heat exchanger 124 of the cooling section 120.

[0106] The embodiment shown in Figure 3 differs from that of Figure 1 primarily in the circuit 130 supplying the hot working fluid to the heating section 100 and in the preheating of the hydrocarbon feed. Furthermore, in this embodiment, a single temperature storage system 170 is mounted in parallel with the heating device 133 of circuit 130.

[0107] In this embodiment, circuit 130 comprises:

[0108] a heating device 133 for the working fluid, located upstream of the reactor-exchanger 112 relative to the working fluid circulation,

[0109] two heat exchangers 134', 135', here mounted in series, located downstream of the reactor-exchanger 112 and upstream of the heating device 133,

[0110] a device for circulating the working fluid 139.

[0111] 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, which 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. 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 of the hydrocarbon feed supplied by line 3 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. 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.

[0112] 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.

[0113] Thus, in this embodiment, the working fluid follows the following path in the circuit 130. The compressor 139 sends the working fluid 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 further heated in the heating device 133 and / or in the thermal storage system 170 before entering the reactor-exchanger 12 through inlet 115, where it transfers heat to the tubes to carry out the steam cracking reaction. Upon exiting the reactor-exchanger 112, the working fluid first passes through the first heat exchanger 134' before being directed to the second heat exchanger 135' where it is used to heat water. It is then returned by the compressor 139 to the first heat exchanger 134'.

[0114] In the embodiment shown here, during the charging phase of the thermal storage system, a fraction of the working fluid flow circulating in circuit 130 can be sent through the thermal storage system 170 so that it accumulates heat. Depending on the temperature of this fraction, the electric heating device of the thermal storage system can be activated to reach a desired thermal storage temperature.During the discharge phase, depending on this thermal storage temperature, it will be possible either to circulate the entire working fluid flow through the thermal storage system 170 to heat it to the desired target temperature, with the heating device 133 of the circuit being off, or to circulate a fraction of the working fluid flow through the thermal storage system 170 to heat it to a first temperature, and operate the heating device 133 of the circuit to heat the remaining fraction of the working fluid flow to a second temperature, which, by mixing with the fraction of working fluid at the first temperature, reaches the target temperature.

[0115] The hydrocarbon feedstock is first preheated 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 gas mixture is then further heated in this heat exchanger 122 before entering the reactor-exchanger tubes 112 through the inlet 113, where the steam cracking reaction takes place.At the outlet of the reactor-exchanger 112, the hot effluent is rapidly cooled in the heat exchanger 122, then further cooled in the preheating heat exchangers 150 and 160, which respectively heat dilution steam and the hydrocarbon feed.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] The various embodiments of the heating and thermal storage devices for the circuit described above can be combined according to the desired objective. Specifically, during the discharge phase, when a fraction of the working fluid is heated to a first temperature and the remaining fraction to a second temperature, those skilled in the art can determine each temperature as a function of the flow rates so that all of the working fluid entering at least one heat exchanger reactor reaches the desired target temperature. Generally, thermal storage systems will be chosen that enable the working fluid to reach the desired target temperature at the inlet of at least one heat exchanger reactor 112, whether or not this is combined with the circuit heating device(s).It is therefore understood that it is possible to consider many different arrangements of these devices and systems (parallel and / or series connections), and / or continuous operation with periods of reduced operation and / or temporary shutdown of the heating device(s).

[0121] 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 heating device that does not emit CO2 to a target temperature, typically above 900 °C, generally under increased pressure (>20 bar), and sent into a heat exchanger reactor, preferably into its shell, where it Heat is exchanged, 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 reduced-temperature, reduced-pressure heat transfer fluid is repressurized by compression or pumping (in the case of fluid condensation), and reheated using the heating device to the target temperature to close the cycle.

[0122] The invention thus offers the following advantages:

[0123] 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,

[0124] Improved control of tube skin temperature in the heat exchanger reactor, allowing for limited coking,

[0125] 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,

[0126] optimized management of energy consumption required for heating the working fluid through the use of thermal storage system(s).

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 a working fluid circulates,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) of the working fluid located upstream of at least one heat exchanger reactor (112) with respect to the circulation of the working fluid, at least one thermal storage system (170, 170') coupled to the circuit (130) in a closed loop via a bypass pipe (172, 172'), and mounted in parallel with at least one heating device (131, 132; 133) or downstream of the latter, and upstream of at least one heat exchanger reactor (112), 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 working fluid circulation device (138, 139), a management system (180) for at least one heating device (131, 132; 133) for the closed-loop circuit (130) and at least one thermal storage device (170, 170'), configured for:, (i) in a charging phase of at least one thermal storage system (170, 170'), operate at least one heating device (131, 132; 133) of said circuit to heat the working fluid to a target temperature, and accumulate heat within at least one thermal storage system, (ii) in a discharge phase of at least one thermal storage system (170, 170'): circulate through the at least one thermal storage system (170, 170') all, or respectively a fraction, of the working fluid flow rate circulating in said circuit to heat it to the target temperature, respectively to a first temperature, and stop at least one heating device of said circuit, or command it to heat to a second temperature the remaining flow fraction of the working fluid which, in mixing with the working fluid fraction at the first temperature, reaches the target temperature.

2. Steam cracking plant (100) according to claim 1, characterized in that at least one thermal storage system (170, 170') comprises one or more thermal storage devices each containing a solid or liquid thermal storage medium, and optionally one or more electrical heating devices (176, 176').

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 for said circuit (130) 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 of said circuit (130) 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 said circuit (130) to receive at least one constituent of the preheated mixture.

6. Steam cracking plant according to any one of claims 1 to 5, 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 (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 constituent of the gas mixture and adapted to preheat it before its entry into 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 (112) 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 preheating heat exchangers (150, 160): the first preheating heat exchanger (150) being connected on the one hand to the heat exchanger (122) of the cooling section to receive the cooled gaseous effluent and on the other hand to the second heat exchanger (135') of the closed-loop circuit (130) to further heat and vaporize the water exiting this last,the second preheating heat exchanger (160) being connected on the one hand to the heat exchanger (122) of the cooling section to supply it with a component of the heated gas mixture and on the other hand to the first preheating heat exchanger (150) to receive the further cooled gaseous effluent.

9. 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 mounted 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 at least one heat exchanger reactor (112) with respect to the fluid circulation, so as to preheat a constituent of the gas mixture, the second heat exchanger (126) being connected on one side to the first heat exchanger (124) and on the other side 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 constituent 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 is circulated within a closed-loop circuit (130), this circuit being connected on one side to the other inlet of at least one heat exchanger reactor selected 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, 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) and / or by means of at least one thermal storage system (170, 170') of said circuit (130) in the following manner: (i) in a charging phase of at least one thermal storage system (170, 170'), at least one heating device (131, 132; 133) of said circuit (130) is operated to heat the working fluid to the target temperature, and heat is accumulated within at least one thermal storage system, (ii) in a discharge phase of at least one thermal storage system (170, 170'): the entire, or a fraction, of the working fluid flow circulating in said circuit is circulated through the at least thermal storage system to heat it to the target temperature, or to a first temperature, respectively, and at least one heating device (131, 132; 133) of said circuit (130) is stopped, or is controlled to heat to a second temperature the remaining fraction of the working fluid which, in mixing with the fraction of working fluid at the first temperature, reaches the target temperature, (b) the working fluid is introduced at the target temperature inside the reactor-heat exchanger, the cooled working fluid is recovered and reinjected into the closed loop circuit (130) 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.

11. Method according to claim 10, characterized in that, at least one storage system (170, 170') comprising at least one electric heating device, during the charging phase, it can be operated to accumulate calories, and optionally stopped during the discharging phase.

12. A process according to claim 10 or 11, characterized in that it comprises at least one of the following features: the working fluid is selected from water, CO2, helium, nitrogen or argon, the target temperature of the working fluid is from 900 to 1600 °C, preferably from 1000 to 1400 °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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