Steam cracking installation in which the steam cracking furnace is supplied with electrically heated oxidising air

Abstract

The invention relates to a steam cracking installation (100) comprising at least: - a steam cracking furnace (10) comprising a radiation zone equipped with burners connected to at least one fuel gas supply line and to at least one oxidising-gas supply line (1), - a cooling unit (12, 14), - a compression unit (13), - a refrigeration / heat pump unit (20) comprising a circuit (200) in which a working fluid circulates, and, mounted in series in the direction of circulation of the working fluid: - a first heat exchanger (Ech_1) transferring heat energy to the at least one oxidising-gas supply line, - an expansion member (202), - at least one second heat exchanger (Ech_2) transferring cold-energy frigories to at least one fluid to be cooled that circulates in the cooling unit (14) and / or the compression unit (13), - a compressor (204).

Description

STEAM CRACKLING INSTALLATION WITH ELECTRICALLY HEATED COMBINATION AIR SUPPLY TO THE STEAM CRACKLING FURNACE Technical field of the invention

[0001] The present invention relates to a hydrocarbon steam cracking installation with electrically heated combustion air supplied to the steam cracking furnace, and the corresponding hydrocarbon steam cracking process. 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.A steam cracking process thus requires inputs of heat (injection of energy to increase the temperature and provide the enthalpy of reaction) and cold (extraction of energy to lower the temperature) to fractionate and significant amounts of energy, a large part of which is currently supplied by fossil energy.

[0003] Increasing environmental concerns, however, require replacing this fossil energy with decarbonized energy (without CO2 emissions) and in particular renewable energy, especially renewable electricity produced by wind turbines and / or solar panels.

[0004] One of the heat inputs required for a steam cracking process is the heating of the combustion air for the burners in a steam cracking furnace. To minimize the amount of fuel needed to provide thermal energy to the material being cracked, the combustion air must enter the burners at a temperature above 200 °C, typically between 300 and 600 °C. Heating this combustion air electrically is possible but expensive, especially when electricity costs are high.

[0005] Therefore, there is a need to heat the combustion gas of a steam cracking furnace while reducing the economic, energy and environmental impact.

[0006] To this end, the invention proposes a steam cracking installation and a steam cracking process implementing one or more heat pump units.

[0007] A first object of the invention relates to a steam cracking installation comprising at least: - a steam cracking furnace, - a cooling unit, - a compression unit, in which the steam cracking furnace comprises a radiation zone equipped with burners connected to at least one fuel gas supply line and to at least one oxidizing gas supply line.

[0008] According to the invention, the installation is further equipped with at least one heat pump unit comprising a circuit in which a working fluid circulates, this circuit comprising, mounted in series in the direction of circulation of the working fluid: - a first heat exchanger, the working fluid circulating in the first heat exchanger transferring calories to the combustion gas circulating in the first heat exchanger supplied by at least one combustion gas supply line, - an expansion member, - at least one second heat exchanger, the working fluid circulating in the second heat exchanger transferring cooling to at least one fluid to be cooled circulating in the second heat exchanger and coming from at least one cooling unit and / or at least one compression unit, - a compression member.

[0009] This arrangement allows for the efficient heating of the combustion gas, usually air, while simultaneously cooling a fluid circulating within the system. This notably reduces the amount of energy required from the cooling and / or compression unit.

[0010] The working fluid used in at least one heat pump can be air, argon, helium, nitrogen (N2), CO2, etc., preferably argon or nitrogen.

[0011] The installation according to the invention may further include a management system for at least one heat pump, in particular configured to operate the at least one heat pump in a mode producing enough heat (calories) to heat the combustion gas to a target temperature and / or enough cold (frigories) to cool the at least one fluid to be cooled, in particular to a target temperature.

[0012] Advantageously, at least one heat pump unit may further include, mounted in the circuit between at least one second heat exchanger and the compressor, at least one third heat exchanger. The working fluid circulating in this third heat exchanger receives heat from a hot fluid. Such a hot fluid may be waste heat from the steam cracking plant, a hot fluid circulating within the steam cracking plant (for example, from a cooling unit of the plant, particularly one located immediately downstream of the steam cracking furnace), a hot fluid from the compressor unit, or a hot fluid from another unit, typically separate from the steam cracking unit. This third heat exchanger increases the temperature of the working fluid entering the compressor and thus the efficiency of the heat pump.One or more third heat exchangers in series or parallel can be considered, each receiving a hot fluid.

[0013] Advantageously, at least one heat pump unit may also include, mounted in the circuit between the first heat exchanger and the expansion valve, a fourth heat exchanger. The working fluid circulating in this fourth heat exchanger receives cooling from a cold fluid. This allows the working fluid of the heat pump to be cooled before entering the expansion valve, further cooling the working fluid, and potentially producing more cooling at the outlet of the expansion valve. This also improves the efficiency of the heat pump.

[0014] Advantageously, at least one cooling unit, typically producing a cooling fluid, can include several cooling stages, and the working fluid of the heat pump circulating in at least one second heat exchanger can transfer cooling to at least one, or even each, cooling stage, thereby relieving one or more of the chillers and reducing their energy consumption. These chillers can, in particular, be cryogenic units. The heat pump can then advantageously include at least two second heat exchangers connected in series or parallel to cascade-cool at least two fluids.

[0015] The at least one compression unit may comprise several compression stages. According to one embodiment of the invention, the working fluid of the heat pump circulating in the at least one second heat exchanger can then transfer cooling to a fluid supplying at least one compression stage, or even each compression stage, thereby relieving one or more of the compression units and reducing their energy consumption. The at least one heat pump may then advantageously comprise at least two second heat exchangers connected in series or parallel to cascade-cool at least two fluids supplying or exiting different stages of the compression unit.When at least one third heat exchanger is present, at least one heat pump may advantageously include at least two third heat exchangers mounted in series or in parallel, each receiving a hot fluid from a stage of the compression unit.

[0016] Advantageously, the installation may also include: - at least one thermal storage system comprising:

[0017] - a secondary combustion gas circulation line connected to at least one combustion gas supply line, on either side of the first heat exchanger of at least one heat pump unit,

[0018] - a thermal storage device connected to the secondary line and capable of receiving or releasing heat to the combustion gas passing through it,

[0019] - optionally an electric heating device mounted on the secondary line upstream of the thermal storage device relative to the direction of combustion gas flow during a charging phase, or integrated into the thermal storage device,

[0020] - a management system for the thermal storage system and at least one heat pump unit, and optionally for the electric heating device, configured, in particular programmed, to:

[0021] (i) in a charging phase in which at least one thermal storage system accumulates heat: circulate through the first heat exchanger of at least one heat pump unit the entire flow of combustion gas circulating in at least one combustion gas supply line, and operate at least one heat pump unit to heat the combustion gas to a target temperature; circulate through at least one thermal storage system a fraction of the flow of combustion gas circulating in at least one combustion gas supply line, this fraction being taken from the outlet of the first heat exchanger of at least one heat pump unit; optionally, control the electric heating device to further heat said taken fraction.

[0022] (ii) in a discharge phase in which at least one thermal storage system provides calories: circulate through at least one thermal storage system all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line to heat it to the target temperature or to a first temperature, this combustion gas flow being taken upstream of the first heat exchanger of at least one heat pump unit, optionally shut down the electric heating device;and stop at least one heat pump unit, or circulate through the first heat exchanger of at least one heat pump unit the remainder of the combustion gas flow circulating in at least one combustion gas supply line and operate at least one heat pump unit to heat to a second temperature this remaining fraction of combustion gas flow which, in mixing with the fraction of combustion gas flow at the first temperature, reaches the target temperature.;

[0023] The first and second temperatures can be determined based on the flow rates to be heated so that the mixture of the two fractions of combustion gas flow (at the outlet of the heat pump and the storage device) reaches the desired target temperature. The second temperature can, for example, be lower than the target temperature, so that the heat pump operates at partial load and is thus relieved of some of the load. The first temperature can, for example, be higher than or equal to the target temperature.

[0024] Thus, during the charging phase, a portion of the combustion gas, heated by at least one heat pump unit and optionally further heated by an electric heating device, circulates through the storage unit, allowing it to accumulate heat. The charging phase can be sufficiently long to allow for optimal heat accumulation in the storage unit. During the discharging phase, at least a portion of the combustion gas is heated by the thermal storage unit, with the remainder being heated by at least one heat pump unit. This reduces the workload of at least one heat pump unit, particularly because the combustion gas flow rate it must heat is lower than the flow rate it must heat during the charging phase, thereby reducing its electrical consumption.In one embodiment, the entire combustion gas flow can be heated to the target temperature by the thermal storage device, at least one heat pump unit is then stopped.

[0025] Advantageously, the installation can include at least two heat pump units, with the first heat exchangers of the heat pump units mounted in parallel on at least one combustion gas supply line. This arrangement allows the use of lower-capacity heat pump units, and / or provides for the continuous operation of one or two heat pumps, with the remaining units serving as backup, and / or specific control of the heat pumps.

[0026] For example, the installation may then include a management system for at least two heat pump units configured, specifically programmed, to:

[0027] - order at least one heat pump unit to heat to a target temperature at least a fraction of the combustion gas flow circulating in at least one combustion gas supply line, and / or

[0028] - in a charging phase of at least one thermal storage system: circulate through the first heat exchanger of at least one heat pump unit the entire flow of combustion gas circulating in at least one combustion gas supply line, and operate at least one heat pump unit to heat this flow of combustion gas to a target temperature; circulate through at least one thermal storage system a fraction of the flow of combustion gas circulating in at least one combustion gas supply line, and control at least one other heat pump unit, and optionally control the electric heating device,to heat this fraction taken from the outlet of the first heat exchanger of said at least one other heat pump unit; and - in a discharge phase of at least one thermal storage system: circulate through at least one thermal storage system all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line to heat it to the target temperature or to a first temperature, this combustion gas flow being taken upstream of at least one heat pump unit, optionally stop the electric heating device, and stop at least one heat pump unit used in the charging phase to heat the combustion gas entering at least one thermal storage system,stop at least one other heat pump unit used in the charging phase to heat the combustion gas to the target temperature, or command it to heat a fraction of the combustion gas flow to a second temperature, which, when mixed with the fraction of combustion gas flow at the first temperature, reaches the target temperature.

[0029] The invention also relates to a steam cracking process implemented in a steam cracking installation according to the invention, characterized in that it comprises: - a step of cracking a hydrocarbon feedstock in the cracking furnace at a cracking temperature, this cracking temperature being obtained by the combustion in the burners of the steam cracking furnace of a mixture of combustion gas and hot oxidizing gas, in which the heating of the oxidizing gas before its entry into the burners is carried out by at least one heat pump unit and comprises: (a) supplying the first heat exchanger of at least one heat pump unit with oxidizing gas to be heated, (b) supplying the second heat exchanger of at least one heat pump unit with a cold fluid; (c) recovering at the outlet of the first heat exchanger of at least one heat pump unit an oxidizing gas at a target temperature.

[0030] The cold fluid received by the second heat exchanger in step b) is typically a cold fluid to be cooled circulating in the second heat exchanger and coming from at least one cooling unit and / or at least one compression unit.

[0031] Typically, the cold fluid cooled to a target temperature, different from the target temperature of the combustion gas, is recovered from the outlet of the second heat exchanger (Ech_2) of at least one heat pump unit.

[0032] The oxidizing gas to be heated can, before heating, be at an initial temperature ranging from ambient temperature to 150 °C, and be heated to a target temperature higher than this initial temperature, the target temperature being able to range from 200 to 700 °C, preferably from 300 to 600 °C.

[0033] The cold fluid to be cooled can, before cooling, be at an initial temperature ranging from ambient temperature to 95 °C, and be cooled to a target temperature lower than this initial temperature, the target temperature being, for example, ranging from +15 °C to -150 °C.

[0034] Advantageously, when the installation includes at least one thermal storage system, the heating of the combustion gas of the process according to the invention may then further include:

[0035] (i) a charging phase in which at least one thermal storage system accumulates calories, during which: the entire flow of combustion gas circulating in at least one combustion gas supply line is circulated through the first heat exchanger of at least one heat pump unit, and at least one heat pump unit is operated to heat this flow of combustion gas to a target temperature; a fraction of the flow of combustion gas circulating in at least one combustion gas supply line is circulated through at least one thermal storage system, this fraction being taken from the outlet of the first heat exchanger of at least one heat pump unit; optionally, the electric heating device is activated to further heat said taken fraction.

[0036] (ii) a discharge phase in which at least one thermal storage system provides calories, during which: all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line is circulated through at least one thermal storage system to heat it to the target temperature or to a first temperature, this gas flow being taken upstream of the first heat exchanger of at least one heat pump unit, optionally the electric heating device is stopped;and we stop at least one heat pump unit, or we circulate through the first heat exchanger of at least one heat pump unit the remainder of the combustion gas flow circulating in at least one combustion gas supply line and we operate at least one heat pump unit to heat to a second temperature this remaining fraction of combustion gas flow which, in mixing with the fraction of combustion gas flow at the first temperature, reaches the target temperature.;

[0037] When the installation includes at least two heat pump units, at least one heat pump unit can be ordered to heat to a target temperature at least a fraction of the combustion gas flow circulating in at least one gas supply line.

[0038] Alternatively or in combination, when the installation includes at least two heat pump units and at least one thermal storage system, the process may then include:

[0039] - in a charging phase of at least one thermal storage system: the entire flow of combustion gas circulating in at least one combustion gas supply line is circulated through the first heat exchanger of at least one heat pump unit, and at least one heat pump unit is operated to heat this flow of combustion gas to a target temperature; a fraction of the flow of combustion gas circulating in at least one combustion gas supply line is circulated through at least one thermal storage system, and at least one other heat pump unit is activated, and optionally the electric heating device is activated, to heat this fraction taken from the outlet of the first heat exchanger of this at least one other heat pump unit.and- in a discharge phase of at least one thermal storage system: all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line is circulated through at least one thermal storage system to heat it to the target temperature or to a first temperature, this combustion gas flow being taken upstream of at least one heat pump unit; optionally, the electric heating device is stopped, and at least one heat pump unit used in the charging phase to heat the combustion gas entering at least one thermal storage system is stopped, at least another heat pump unit used in the charging phase to heat the combustion gas to the target temperature is stopped, or it is controlled to heat a fraction of the combustion gas flow to a second temperature, whichWhen mixed with the fraction of oxidizing gas flow at the first temperature, the target temperature is reached.

[0040] The installation and process according to the invention are particularly well-suited to the steam cracking of ethane but can also be implemented for the steam cracking of other hydrocarbon feedstocks such as liquefied petroleum gases (propane, butane), naphtha, diesel fuel, and vacuum distillates. Other possible hydrocarbon feedstocks include hydrocarbons 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, or biomass hydrothermal liquefaction oils. Other possible hydrocarbon feedstocks include hydrocarbons obtained by pyrolysis, hydrothermal liquefaction, or hydrocracking of plastic waste. Detailed description of the invention Description of the figures

[0041] The invention is now described with reference to the accompanying, non-limiting drawings, in which:

[0042] Lare represents schematically a steam cracking installation comprising at least one heat pump unit according to an embodiment of the invention.

[0043] Lare represents schematically a steam cracking installation comprising at least one heat pump unit according to another embodiment of the invention.

[0044] Lare represents schematically a steam cracking installation comprising three heat pump units and a thermal storage system in different operating modes (a), (b), (c).

[0045] The diagram schematically represents an example of a complete steam cracking installation according to the invention.

[0046] The diagram schematically represents an example of a compression unit in a steam cracking plant.

[0047] The diagram schematically represents an example of a cryogenic cooling unit for a steam cracking plant.

[0048] In the figures, the same elements are designated by the same references.

[0049] The terms "upstream" and "downstream" are used in relation to the flow of fluids, symbolized by arrows in the figures.

[0050] The various units of a steam cracking plant include many components requiring either an electrical power supply, a thermal power supply, or both.

[0051] In particular, the steam cracking furnace, also called a steam cracking reactor, includes supply lines for the fluids entering the steam cracking reactor(s) and sections for heating the fluids and / or producing steam entering the reactor(s).

[0052] The thermal energy required for the steam cracking reaction is supplied by the combustion of a fuel gas with an oxidizing gas (air, etc.). Approximately 40 to 50% of the heat of combustion is absorbed in a radiant zone of the steam cracking furnace, while the remainder passes to a convection zone where the majority of the sensible heat from the combustion gases is exchanged to preheat hydrocarbons and / or water and / or steam via at least one heat exchanger.

[0053] In the present invention, the oxidizing gas, typically air, supplying the burners of the steam cracking furnace is heated to a target temperature by means of one or more heat pumps.

[0054] Figure 1 schematically represents a steam cracking plant comprising a steam cracking furnace 10, two cooling units 12 and 14, and a heat pump unit 20, also called a "heat pump" and denoted as TFP in the rest of the description. The burners of the steam cracking furnace (not shown) are supplied with combustion gas via the supply line 1.

[0055] As represented, the TFP20 comprises a circuit200 in which a working fluid, preferably a gas (argon, helium, N2, CO2, air, etc.), circulates. This circuit200 comprises, mounted in series in the direction of the working fluid's flow: - a first heat exchangerEch_1, the working fluid circulating in this exchanger transferring heat to the combustion gas circulating in the first heat exchanger, which is supplied by the combustion gas supply line1, - an expansion device202, - a second heat exchangerEch_2, the working fluid circulating in the second heat exchanger transferring cooling to at least one fluid to be cooled circulating in the second heat exchanger and coming from one of the cooling units, - a compression device204.

[0056] Typically, the combustion gas flowing in the supply line 1 enters the exchanger Ech_1 at a temperature ranging from ambient temperature to 150 °C and exits at a higher target temperature, usually from 200 to 700 °C, most often from 300 to 600 °C.

[0057] The working fluid circulating in the second heat exchanger Ech_2 can thus transfer cooling to a process fluid to be cooled, which in this case comes from the cooling unit 14 supplied via a pipe 3. This cooling unit 14 can advantageously be a cryogenic cooling unit from the steam cracking plant, typically comprising several cooling units as described below. Alternatively, the fluid to be cooled could come from the compression unit, as described below.

[0058] These components are sufficient to heat the combustion gas to the target temperature. They are also sufficient to cool the process fluid to a target temperature different from the combustion gas's target temperature, typically lower. To this end, the various components of the thermal processing unit (TPU) can be sized to produce the desired thermal energy (heat and cooling).

[0059] The expansion device can be a pressure regulator (electronic regulator, calibrated orifice, etc.) or a turbine. The compression device, referred to as the compressor below, is typically driven by an electric motor. In some cases, it may also be driven, at least partially, by the turbine when one is present.

[0060] The TFP cycle is a classic heat pump cycle: heat is extracted from a hot source to be cooled (the fluid to be cooled circulating in pipe 3 and entering heat exchanger Ech_2). The compressor 204 increases the pressure / temperature of the working fluid at the inlet of heat exchanger Ech_1, thus preheating the combustion gas. The cooled working fluid exiting heat exchanger Ech_1 is then expanded in the expansion chamber to be reheated in heat exchanger Ech_2. To optimize cycle efficiency, the expansion chamber can advantageously be a turbine. The work done by compressor 204 depends on the electrical power supplied to the compressor, typically via an electric motor driving the compressor. The TFP's electrical consumption can therefore vary depending on the target temperature to which the TFP must heat the combustion gas.

[0061] Given the temperatures to be reached (200-700 °C), this is typically a "reverse" Brayton cycle preferably using a working fluid that remains in the gaseous phase.

[0062] To improve the efficiency of the heat pump 20, the circuit 200 may include a third heat exchanger Ech_3, located between the second heat exchanger Ech_2 and the compressor 204. The working fluid circulating in this third heat exchanger receives heat from a hot fluid to be cooled (waste heat) originating from the installation, for example, from a cooling unit 12 or a compression unit. This hot fluid may also come from ambient air or from an installation other than the steam cracking plant. For example, this hot fluid may be water circulating in a pipe 5 and originating from a cooling unit 12. The latter is typically located immediately after the steam cracking furnace 10 and serves to rapidly cool, by quenching, the cracked gases exiting the TLX behind the steam cracking furnace.The water circulating in pipe 5 can thus enter the heat exchanger Ech_3 at a temperature of 75-85 °C and exit at a lower temperature of 65-75 °C. This hot fluid can also come from the compression unit, and for example be taken from the outlet of one of the compressor stages of this unit.

[0063] In the example shown in Figure 1, the TFP (Total Functional Process) includes a fourth heat exchanger, Ech_4, between the first heat exchanger, Ech_1, and the expansion valve 202. This heat exchanger cools the working fluid before it enters the expansion valve 202. The working fluid circulating in the fourth heat exchanger receives cooling from a cold fluid supplied via a pipe 205, as shown. This cold fluid can be water, for example, at a temperature of 10 to 25 °C, or ambient air. This heat exchanger allows, in particular, for subcooling of the fluid circulating in circuit 200 before it enters the expansion valve 202, especially when the combustion gas entering heat exchanger Ech_1 is at a temperature higher than the ambient temperature. This further reduces the negative temperature at the outlet of the expansion valve, thus producing cooling at a lower temperature.

[0064] Thus, in one embodiment, the TFP20 comprises only the first and second heat exchangers Ech_1, Ech_2, and in a preferred embodiment, the TFP20 comprises the first, second, and third heat exchangers Ech_1, Ech_2, Ech_3, while in another preferred embodiment, the TFP20 comprises the first, second, third, and fourth heat exchangers Ech_1, Ech_2, Ech_3, Ech_4. In each of these embodiments, heat exchanger Ech_2 can be replaced by two or more Ech_2s connected in series or parallel; each heat exchanger Ech_2 can then be used to cool a specific fluid. Heat exchanger Ech_3 can also be replaced by two or more Ech_3s connected in series or parallel.

[0065] In general, the installation 100 may include a management system 22 to control the TFP. This management system 22 may, in particular, regulate the target temperature of the combustion gas at the outlet of the heat exchanger Ech_1 by regulating the electrical power supplied to the TFP, and in particular to its compressor, and regulate the target temperature of the fluid to be cooled exiting a heat exchanger Ech_2.

[0066] In order to reduce the electrical consumption of the TFP, particularly when the cost of electricity is high, in one schematically represented embodiment, the installation 100 may include a thermal storage system 24. The lane embodiment differs from that represented only by the presence of a thermal storage system 24, the TFP 20 comprising four exchangers Ech_1, Ech_2, Ech_3, Ech_4.

[0067] This thermal storage system24 includes:

[0068] - a secondary air circulation line 240 connected to the combustion gas supply line 1, on either side of the first heat exchanger Ech_1 of the TFP20, - a thermal storage device 242 connected to the secondary line 240 and capable of receiving or releasing heat to the combustion gas that passes through it, - optionally an electric heating device 244 mounted on the secondary line 240 upstream of the thermal storage device 242.

[0069] The electric heating device may be a Joule (resistive), induction, microwave, shock wave, or plasma heating device, or a combination thereof, preferably a Joule and / or induction heating device. It is positioned upstream of the thermal storage device, particularly with respect to the gas flow when the thermal storage system is in a charging phase. Alternatively, this electric heating device may be integrated into the thermal storage device.

[0070] The secondary line 240 can be connected to the supply line 1 by one or more valves and include one or more fans to draw combustion gas flowing in the supply line 1 upstream or downstream of the heat exchanger Ech_1 and circulate it in the secondary line 240 in one direction or the other, depending on the operating mode of the thermal storage system, as described below. In Figure 1, the secondary line 240 is equipped with a valve 245 and a fan 246, and is connected to the supply line 1 by a valve 247. The invention is, of course, not limited by the number of valves and / or fans or by their position.

[0071] Preferably, sensible heat storage devices using a solid thermal storage medium (generally in the form of powders, particles, or solid blocks with open cavities and / or channels) with suitable thermal storage capacities and / or capable of achieving heat transfer rates appropriate for the intended use will be used. This solid medium may, for example, be contained in an insulated tank. Suitable solid media include metals, volcanic rocks, or refractory materials such as alumina, etc. Thermal storage devices containing volcanic rocks produced by Brenmiller Energy may be used.Stacked refractory materials can also 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-shaped, bushel-shaped, or pot-shaped. Electrically conductive refractory bricks can also be used, which can be heated by circulating gas and / or by an electric current passing through the bricks during the charging of the thermal storage (for example, refractory bricks from a Joule Hive Thermal Battery).

[0072] This thermal storage system 24 is controlled by the management system 22, which is configured to operate the thermal storage system 24 cyclically in a charging phase during which it accumulates heat and in a discharging phase during which it releases the accumulated heat. The management system 22 will also control the installation's TFP(s) 20 according to the operating mode of the thermal storage system 24, and one or more valves regulating the flow rates of combustion gas circulating in the pipes 1 and 240.

[0073] Specifically, the management system22 can be configured, including programming, to:

[0074] (i) during a charging phase of the thermal storage system, circulate through the thermal storage device 242 a fraction of the combustion gas flow circulating in the supply line 1, this fraction being taken from the outlet of the first heat exchanger Ech_1 of the TFP, optionally further heated by the electric heating device 244; circulate through the first heat exchanger Ech_1 of the TFP the entire combustion gas flow circulating in at least one combustion gas supply line upstream of the TFP; and operate the TFP 20 to heat the combustion gas to a target temperature, typically at least 200°C, generally from 300 to 600°C,

[0075] (ii) During a discharge phase of the thermal storage system, circulate through the thermal storage device 242 all or a fraction of the combustion gas flow circulating in the combustion gas supply line 1 upstream of the TFP to heat it to the target temperature or to a first temperature, for example close to that of the thermal storage device 242, this fraction being taken upstream of the first heat exchanger Ech_1 of the TFP; and stop the TFP20 or operate the TFP20 to heat a remaining fraction of the combustion gas flow to a second temperature to reach the target temperature at point 243 where the two combustion gas flows are mixed. During this phase, the electric heating device is also stopped.

[0076] When the thermal storage system is operating in discharge mode, it is therefore possible to completely stop the TFP or to reduce its electrical consumption by about 25% compared to its operation in charge mode.

[0077] In particular, it is possible to configure the management system 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, etc.), which makes it possible to decarbonize the electrical consumption of the installation and / or reduce operating costs.

[0078] Preferably, the inlet temperature of the thermal storage device during the charging phase is higher than the target combustion gas temperature to be achieved, for example, at least 20 to 40 °C higher. This temperature can be reached either solely by the heat supplied by the thermal storage device (TSD), or by the heat supplied by the TSD and the auxiliary heating device.244 The latter approach may be preferable to avoid having to oversize the TSD.

[0079] For increased availability or greater system flexibility, the installation may include one or more TFPs connected in parallel. For example, two, three, or four TFPs, or even more, could be connected in parallel, preferably in combination with a thermal storage system.

[0080] This allows, in particular, the use of TFPs of the same power that can operate simultaneously or independently to provide the heat required to warm the combustion gas and the cooling required to cool a fluid. This also allows the use of commercially available TFPs without having to design one specifically sized for the application.

[0081] Diagram 1 schematically represents an installation comprising three TFPs, labeled TFP1, TFP2, and TFP3, connected in parallel. Each TFP can be as described in Figure 2, with or without heat exchangers Ech_3 and / or Ech_4. The first heat exchanger Ech_1 of each TFP is then connected in parallel to the combustion gas supply line 1, on branches 1a, 1b, and 1c, as shown in Figure 1. The combustion gas flow rates circulating in each of the branch lines 1a, 1b, and 1c, and in the circuit 240 of the thermal storage system, can be controlled by one or more valves labeled V, V1a, V1b, V1c, and V240 in Figure 1. For the sake of simplicity, certain elements of the thermal storage system 24 are not shown in Figure 1 when they are not in use.

[0082] In nominal mode, shown (a), two TFPs (TFP1 and TFP2) operate to provide the heat required to heat each a fraction of the combustion gas flow circulating in bypass lines 1a and 1b, respectively, from 25 °C to 540 °C. The third TFP, TFP3, is not operating, nor is the thermal storage system 24. The two TFPs also provide the cooling capacity required to cool either a separate fluid or the same fluid.

[0083] In a charging mode of the thermal storage system 24 shown (b), two of the TFPs (TFP1 and TFP2) operate to provide the heat necessary to heat each a fraction of the combustion gas flow circulating in the bypass lines 1a and 1b, respectively, from 25 °C to 540 °C, while the third TFPTFP3 operates to "charge" the thermal storage system 24: a fraction of the combustion gas flow heated by the third TFPTFP3, possibly further heated by the auxiliary electric heating device 244, passes through the thermal heating device 242, allowing it to accumulate heat. When the accumulation is sufficient, and particularly when the cost of electricity is high, the thermal storage system 24 can then switch to discharge mode, as shown (c), or to nominal mode, as shown in (a).In discharge mode, the third TFP3 is then shut down, as is the auxiliary electric heating device 244, while only one of the other two TFPs (here, TFP1) is operating. The heat produced by the single operating TFP and the thermal heating system 24 then allows the combustion gas to be heated from 25 °C to 540 °C. The gas flow rate in the supply line 1 is thus divided between the secondary line 240 and the bypass line 1a. With only one of the TFPs operating, the overall electrical consumption is reduced compared to the other two operating modes (a) and (b). The gas flow rate in the bypass line 1a can also be chosen to be lower than the flow rate in the secondary line 240a in order to further reduce the electrical power required by TFP1.

[0084] In the event of a malfunction of one of the three TFPs, the thermal storage system24 can be deactivated so as to use the other two TFPs in nominal mode to heat the combustion gas.

[0085] The invention is not limited to this use of the three TFPs: in particular, in nominal mode or in charging phase, the three TFPs can operate simultaneously, with at least one of the TFPs being stopped or operating at reduced load in discharging phase.

[0086] Of course, the present invention is not limited by the number of TFPs, which can be chosen according to the power of the available TFPs. Two or four TFPs, or more, could be used, operating alternately or together in different configurations, preferably in combination with a thermal storage system to reduce the electrical consumption of the TFPs.

[0087] We could also consider two, three or four TFPs, or more, mounted in parallel, but without a thermal storage system, although this is not preferred.

[0088] When multiple TFPs are mounted in parallel, it can be advantageous to use identical TFPs.

[0089] In general, regardless of the embodiment, the management system is advantageously configured to operate at least one heat pump in a mode that produces sufficient heat to heat the combustion gas to a target temperature and sufficient cooling capacity to cool at least one fluid to be cooled to another target temperature. Preferably, during the discharge phase of a thermal storage system, where such a system is present, at least one heat pump operates to heat a fraction of the combustion gas flow to the target temperature or to the second temperature mentioned above, and to cool to another target temperature a cold fluid circulating in the second heat exchanger of the at least one operating heat pump.

[0090] The management system 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 thermal heating element(s) used in the present invention, as well as the electric heating device of the thermal storage system when present, and the thermal storage system itself when present. It can thus be connected to these components, and in particular to the components of each thermal heating element used, 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.

[0091] The management system22 can also receive various pieces of information from one or more appropriately arranged sensors relating to:

[0092] - to the power supply (electrical and / or thermal) of each TFP (quantity of current received and consumed, temperature and / or flow rate of fluids whose temperature is controlled),

[0093] - the charging and discharging state of each thermal storage system (temperature of the thermal storage devices),

[0094] - to the phase in which each thermal storage system is located (charging, discharging),

[0095] - to the amount of electrical and / or thermal energy received / produced by each TFP and / or electric heating device (quantity of current, flow rate and / or temperature of fluids).

[0096] The management system typically includes output or input / output interfaces. These may 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 communication channels, optionally bidirectional, between the management system and the components of the TFP(s), the energy storage system, and / or the heating elements.

[0097] The management system22 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.

[0098] The process and installation of steam cracking are described in more detail with reference to the diagram which schematically represents a complete steam cracking installation100, including a steam cracking furnace10, cooling units, a compression unit and fractionation units.

[0099] The hydrocarbon feedstock cracking step is carried out in the steam cracking furnace 10 at a cracking temperature. This cracking temperature is achieved by burning a mixture of combustion gases and hot oxidizing gases in the steam cracking furnace burners. For this purpose, the hydrocarbon feedstock to be treated is introduced into heat exchangers located in the convection zone of the steam cracking furnace 10 via a pipe 102, typically at a temperature of 60°C, possibly using a pump 103 when the feedstock is liquid. Dilution steam is introduced into heat exchangers located in the convection zone of the steam cracking furnace via the pipe 104.

[0100] Typically, the steam cracking furnace 10 comprises a lower radiant section 10a and an upper convection section 10b. The heat from the radiant section 10a is supplied by the combustion of a fuel (generally combustible gas, such as methane or H2) in the presence of an oxidizer (air, etc.) in at least one burner. The steam cracking furnace 10 thus comprises one or more fuel supply lines 105 and one or more oxidizer supply lines 1 to one or more burners. Combustion takes place in one or more burners located in the base, the ceiling, and / or the side walls of the lower part of the furnace enclosure 10. The TFP20 used according to the invention is thus located on the line 1

[0101] The hydrocarbon feedstock and dilution steam are injected into at least one heat exchanger tube bundle (not shown) located in the convection zone 10b. The two streams may be preheated separately and then mixed and further preheated in at least one heat exchanger tube bundle, typically to a temperature between 600 and 680°C. This mixture is then distributed into one or more tube reactors (not shown) located in the radiation zone 10a. Burners in the radiation zone further heat the tube reactors to initiate thermal cracking. The effluent temperature at the outlet of the tube reactors is typically between 800 and 900°C.

[0102] The effluent exiting the steam cracking furnace is then rapidly cooled (quenched) in one or more cooling units11,12,17, then purified and separated in compression13 and fractionation15 units.

[0103] 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. These cracked gases are rapidly cooled, typically to 338–510°C, to stop pyrolysis reactions and minimize secondary polymerization reactions.Depending on the average molecular mass of the filler, the relative quantities of the different products vary: for light fillers, such as ethane, there are few hydrocarbons with more than 4 carbons.

[0104] Typically, at the outlet of the steam cracking furnace reactor(s)10, the cracked gases are evacuated via a pipe107 into a rapid cooling unit11 comprising one or more heat exchangers (often designated by the acronyms TLE or TLX for "Transfer Line Exchanger"), in which the cracked gases are cooled, typically from 820-850°C to 300-510°C.

[0105] In some installations, such as the example described here, at the outlet of the rapid cooling unit11, the cracked gases are brought via a pipe108 to an optional fractionation column17 (also called primary fractionation) to condense and separate the fuel oil fraction from the cracking gas.

[0106] At the outlet of the fractionation column 17, the fractionated overhead gases are conveyed via a pipe 112 to a second cooling unit 12, in this case a water-quench tower, which condenses most of the dilution vapor and heavy fuels present in the gases. The gases are cooled by means of water circulating in the pipe 113. In this example, this water is extracted from the lower part of the quench tower 12 and returned by means of a pump 114 to the top of the quench tower after being cooled in a heat exchanger 115 and 116 before being reintroduced into the quench tower 12. This water, or part of it, can be circulated in the pipe 5 of the third heat exchanger Ech_3 of a TFP as a heat source.

[0107] The heaviest hydrocarbons recovered at the bottom of the quenching tower 12 can be returned via a pump 117 and a pipe 118 to the fractionation column 17 and / or via a pump 119 and a pipe 120 to a stripper 121.

[0108] At the outlet of the second cooling unit12, the cracked gases enter via a pipe122 into a compression unit13, then via a pipe123 into a third cooling unit14 and are finally brought via a pipe124 to a fractionation unit15, the products of the steam cracking plant being recovered via at least one pipe125.

[0109] The compression unit typically comprises a series of compression stages, usually three to six, each stage including a compressor, a cooling system (e.g., a heat exchanger), and a liquid-gas separation device. The compressors in the various stages are generally powered by a steam turbine or an electric motor (or a combination of these). This compression unit also includes a purification section to remove acidic gases (CO2, H2S, SO2) and a drying section to remove residual water. Between the compression stages, condensed water and light gasoline are removed.

[0110] An example of such a compression unit, well known to those skilled in the art, is schematically represented in Figure 1, in which four compression stages are provided. The compressors are designated by reference numbers 1301, 1302, 1303, and 1304; the cooling means, for example, heat exchangers, are designated by reference numbers 1311, 1312, 1313, and 1314; and the separation devices are designated by reference numbers 1321, 1322, 1323, and 1324. At the inlet of the first stage, the cracked gases are conveyed via a pipe to a separation device 1325 in order to separate the condensed hydrocarbons. At each stage, the gases are compressed in the compressor and then cooled by the cooling means before entering the separation devices. The gases exiting the separation device are sent to the inlet of the compressor of the next stage.At the outlet of the penultimate stage, the gases are sent to a purification section 1340 to remove acidic gases, typically by scrubbing with a caustic solution or an amine solution, or both. At the outlet of the final compression stage, the gases are finally sent to a drying section 1350 to remove residual water. The mechanical energy required to rotate the compressors of the various stages is supplied by a steam turbine or an electric motor 1300.

[0111] At the outlet of the compression unit13, the gases are then sent to the third cooling unit14 in which they are cooled to cryogenic temperatures before being sent to the fractionation unit15.

[0112] The third cooling unit, a cryogenic type, requires a cooling supply provided by circuits comprising numerous components such as a compressor, heat exchanger, and pressure-reducing valve. This cooling is generally provided by cryogenic fluids such as liquid ethylene and propylene. Liquid ethylene and propylene are produced through successive compression stages followed by cooling to condense the majority of the ethylene or propylene.

[0113] The third cooling unit14 includes, for example, refrigeration cycles that typically use some of the propylene and ethylene produced as refrigerants to perform the fractionation. The gases undergo several refrigeration cycles during which the refrigerants are produced by liquefaction through a compressor, then cooled in a heat exchanger, and then further cooled by expansion. Typically, in this refrigeration cycle, the temperature of the ethylene is in the range of -100 to -40 °C, and the temperature of the propylene is in the range of -40 to 15 °C. Other refrigeration cycles are, however, possible.

[0114] The diagram schematically represents an example of a refrigeration cycle 30 comprising an ethylene refrigeration cycle 31 and a propylene refrigeration cycle 32 for process fluids to be cooled circulating in pipes 33 and 34. In the ethylene refrigeration cycle 31, ethylene is compressed in a compressor 310, then sent to a heat exchanger 311 in which it is cooled by the propylene circulating in the propylene refrigeration cycle 32 and becomes liquid. The high-pressure liquid ethylene is then collected in a vessel 312, then depressurized by passing through a pressure-reducing valve 313, introduced into a gas-liquid separator 314 in which the liquid ethylene is sent to a heat exchanger 315 to cool a process fluid circulating in pipe 33. At the outlet of this exchanger 315, the gaseous ethylene is returned to the separator 314 and then to the compressor 310.In the propylene refrigeration cycle 32, propylene is compressed in a compressor 320, then sent to a heat exchanger 321 where it is cooled by water or air and becomes liquid. The liquid propylene is then collected in a tank 322, then depressurized by passing through a pressure-reducing valve 323, and introduced into a gas-liquid separator 324. In this separator, the liquid propylene is sent to the heat exchanger 311 to condense ethylene and / or to a heat exchanger 325 to cool a process fluid circulating in the line 34. At the outlet of this exchanger 311, the gaseous propylene is returned to the separator 324 and then to the compressor 320.

[0115] The third cooling unit14 thus allows the cracked gases entering the fractionation unit15 and more particularly the cold fractionation section (often referred to as the cold box) of the latter (de-methanizer) to be cooled, typically in several stages using ethylene, propylene and methane / hydrogen as refrigerant: (1) cooling of the cracked gases to about -70 to -100°C using propylene and / or ethylene in several stages, followed each time by a separation of the condensed hydrocarbons which are injected into the de-methanizer, (2) cooling of the remaining gases to about -125°C using methane / hydrogen, followed by a separation of the condensed hydrocarbons and (3) cooling of the remaining gases to about -165°C using methane / hydrogen, followed by a separation of the condensed methane and producing a hydrogen stream of more than 90 vol% purity.This type of configuration corresponds to a "de-methanizer first" fractionation unit sequence. However, the invention is not limited to this configuration and can be adapted to other fractionation unit configurations, particularly "de-ethanizer first" or "de-propanizer first" configurations.

[0116] The fractionation unit typically comprises a cold fractionation section operating at low temperature to separate C1 / C2 hydrocarbons, followed by a hot fractionation section operating at higher temperature to separate C3 / C4 hydrocarbons. The fractionation unit may, for example, include a digester, a propane converter, and / or an ethane converter. The sequence of these fractionation units—digester, ethane converter, and propane converter—can vary depending on the thermal integration required and influences the design of the cryogenic cooling unit. The fractionation unit typically includes fractionation columns, heat exchangers, and pumps and valves to ensure fluid circulation.

[0117] In this fractionation unit15, the cracked, cooled gases can thus be distilled in a de-methanizer where methane and dihydrogen are extracted, then in a de-ethanizer to recover acetylene, ethane and ethylene, then in a de-propanizer in which propylene, propadiene, methylacetylene and propane are recovered, and finally in a de-butanizer to recover butanes, butadiene and butenes.

[0118] The hot fractionation section of the fractionation unit15 includes reboilers and heat exchangers.

[0119] The various units of a steam cracking plant include many components such as pump, motor, compressor, heat exchanger, condenser, valves, etc., which require an input of electrical or thermal energy to operate.

[0120] The cold thermal energy from the second heat exchanger Ech_2 of a TFP20 can be supplied upstream of the compressors 1301-1304, typically upstream of the tanks 1321-1325, and downstream of the heat exchangers 1311-1314, to further cool the fluid to a temperature not lower than 15 °C, and reduce their energy consumption. For this purpose, the fluid to be cooled circulates in the line 3 of the second heat exchanger Ech_2 of a TFP.

[0121] Alternatively, or in combination, the hot fluid exiting the compressors 1301-1304 or the heat exchangers 1311-1314 of the compression unit shown can also be used as the hot fluid inlet to a third heat exchanger Ech_3 of the TFP20. This hot fluid then circulates in the pipe 5 of the third heat exchanger Ech_3. For example, the fluids exiting the heat exchangers 1311-1314, typically at a temperature of 80-95°C, can be used as the hot fluid supplying a third heat exchanger Ech_3 before entering a third heat exchanger Ech_2 as a cold fluid for further cooling, without lowering them below 15°C to avoid the formation of hydrates.

[0122] In particular, cold thermal energy can be supplied to heat exchangers 316, 326, upstream or downstream of them, to subcool the fluids circulating in cycles 31 and 32. These heat exchangers 316, 326 are located respectively between the tank 312 and the valve 313, and between the tank 322 and the valve 323. This reduces the compression work required by the compressors 310 and 320 to generate the same amount of cooling in the heat exchangers 315 and 325. The fluids can also be cooled upstream of the compressors 310, 320. For example, fluids 33 and 34 can be cooled. In general, cold thermal energy can be supplied at the compressor discharge 320 (around +15 °C) to reduce the discharge pressure (and the power required), on the exchanger 326, to a fraction of the flow 34 (temperatures +15 °C to -40 °C), on the exchanger 316, to a fraction of the flow 33 (temperatures from -40 °C to -100 °C).

[0123] For this purpose, the fluid to be cooled circulates in the pipe 3 of the second heat exchanger Ech_2 of a TFP. When several fluids are to be cooled, each fluid to be cooled can circulate in a pipe 3 of a dedicated heat exchanger Ech_2, which is part of several heat exchangers Ech_2 of the same TFP connected in series.

[0124] When multiple heat transfer fluids (HTFs) are used, each HTF can include a second heat exchanger (Ech_2), or several Ech_2s connected in series or parallel. The heat exchanger(s) (Ech_2) of one HTF are used, for example, to cool a fluid or fluids in different stages of the compression unit. The heat exchanger(s) (Ech_2) of the other HTF are used to cool a fluid or fluids in different stages of the cryogenic cooling unit.

[0125] The invention is not limited by the number of stages of the cryogenic cooling unit and the compression unit: the number of stages of these units may be different from the number of stages of the units shown in Figures 5 and 6. Example

[0126] In the case of a thermal heat transfer fluid (THF) with four heat exchangers as shown and a thermal storage system as described in the reference (without auxiliary heating), Table 1 summarizes the calculated power outputs of each element in nominal mode (storage system at rest), in thermal storage system charging mode, and in thermal system discharging mode. The storage device used comprises 550 m³ 3bricks as a heat transfer material. It can be seen that, even in nominal mode, the present invention makes it possible to reduce the overall electrical consumption of the installation by reducing the electrical power normally required by the cooling unit (here a cryogenic cooling unit).

[0127] [Table 1] Table 1 Nominal Mode Load Mode Discharge Mode Combustion Air Temperature at TFP Inlet 25 °C 25 °C 25 °C Combustion Air Temperature at TFP Outlet 5 34 °C 5 34 °C 5 34 °C Temperature of Fluid Circulating in Line 3 Incoming to Ech_280 °C 80 °C 80 °C Temperature of Fluid Circulating in Line 3 Exiting Ech_275 °C 70 °C 78 °C Thermal Power Produced by Ech_151 MWth 80 MWth 22 MWth Thermal Power Produced by Ech_216 MWth 25 MWth 7.1 MWth Thermal Power Produced by Ech_37.7 MWth 12 MWth 3.3 MWth Thermal Power Produced by Ech_410.9 MWth 17 MWth 4.7 MWth Thermal Power Received / supplied by the thermal storage system 29 MWth 29 MWth Electrical power consumed by the compressor 38.2 MWe 60 MWe 16.3 MWe Electrical power not consumed by the cooling unit (*) -11.2 *MWe -16.6 MWe -5 MWe

[0128] (*) compared to operation without TFP and without thermal storage.

Claims

Steam cracking installation (100) comprising at least: - a steam cracking furnace (10), - a cooling unit (12, 14), - a compression unit (13), in which the steam cracking furnace includes a radiant zone equipped with burners connected to at least one fuel gas supply line and at least one oxidizing gas supply line (1), characterized in that the installation is further equipped with at least one heat pump unit (20, TFP1, TFP2, TPF3) comprising a circuit (200) in which a working fluid circulates, this circuit (200) comprising, mounted in series in the direction of working fluid flow: - a first heat exchanger (Ech_1), the working fluid circulating in the first heat exchanger transferring heat to the oxidizing gas circulating in the first heat exchanger supplied by at least one oxidizing gas supply line, - an expansion device (202),- at least one second heat exchanger (Ech_2), the working fluid circulating in the second heat exchanger transferring cooling to at least one fluid to be cooled circulating in the second heat exchanger and originating from at least one cooling unit (14) and / or at least one compression unit (13), - a compression unit (204), the installation further comprising a management system (22) for at least one heat pump configured to operate the at least one heat pump in a mode producing sufficient heat to heat the combustion gas to a target temperature and sufficient cooling to cool the at least one fluid to be cooled to another target temperature. Steam cracking installation (100) according to claim 1, characterized in that at least one heat pump unit (20, TFP1, TFP2, TPF3) further comprises, mounted on the circuit (200) between at least one second heat exchanger (Ech_2) and the compression unit (204), at least one third heat exchanger (Ech_3), the working fluid circulating in the third heat exchanger receiving heat from a hot fluid. Steam cracking installation according to claim 1 or 2, characterized in that at least one heat pump unit (20, TFP1, TFP2, TPF3) further comprises, mounted on the circuit (200) between the first heat exchanger (Ech_1) and the expansion member (202), a fourth heat exchanger (Ech_4), the working fluid circulating in the fourth heat exchanger receiving cooling from a cold fluid. Steam cracking installation (100) according to any one of claims 1 to 3, characterized in that at least one cooling unit (14) comprises several cold production stages and in that the working fluid of the heat pump circulating in at least one second heat exchanger (Ech_2) transmits cooling to at least one cold production stage. Steam cracking installation (100) according to any one of claims 1 to 4, characterized in that the compression unit (13) comprises several compression stages and the working fluid of the heat pump circulating in at least one second heat exchanger (Ech_2) transmits cooling to a fluid supplying at least one compression stage. Steam cracking plant (100) according to any one of claims 1 to 5, characterized in that it further comprises: - at least one thermal storage system (24) comprising: - a secondary combustion gas circulation line (240) connected to at least one combustion gas supply line (1), on either side of the first heat exchanger (Ech_1) of at least one heat pump unit (20, TFP1, TFP2, TPF3), - a thermal storage device (242) connected to the secondary line (240) and capable of receiving or releasing heat to the combustion gas passing through it, - optionally an electric heating device (244) mounted on the secondary line upstream of the thermal storage device (242) with respect to a direction of combustion gas flow during a charging phase, or integrated into the thermal storage device (242), - a management system (22) for the thermal storage system (24) and at least one heat pump unit,and optionally of the electric heating device, configured to: (i) in a charging phase in which at least one thermal storage system accumulates heat: circulate through the first heat exchanger (Ech_1) of at least one heat pump unit the entire flow of combustion gas circulating in at least one combustion gas supply line (1), and operate at least one heat pump unit to heat this flow of combustion gas to a target temperature; circulate through at least one thermal storage system (24) a fraction of the flow of combustion gas circulating in at least one combustion gas supply line (1), this fraction being taken from the outlet of the first heat exchanger (Ech_1) of at least one heat pump unit; optionally control the electric heating device (244) to further heat said taken fraction,(ii) in a discharge phase in which at least one thermal storage system (24) provides calories: circulate through at least one thermal storage system (24) all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line (1) to heat it to the target temperature or to a first temperature, this gas flow being taken upstream of the first heat exchanger (Ech_1) of at least one heat pump unit (20, TFP1, TFP2, TPF3), optionally stop the electric heating device (244); and stop at least one heat pump unit (20, TFP1, TFP2, TPF3) or circulate through the first heat exchanger (Ech_1) of at least one heat pump unit (20, TFP1, TFP2, TPF3) the remaining flow of combustion gas circulating in at least one combustion gas supply line (1) and operate at least one heat pump unit (20,TFP1, TFP2, TPF3) to heat to a second temperature this remaining fraction of the combustion gas flow which, when mixed with the fraction of combustion gas flow at the first temperature, reaches the target temperature. Steam cracking installation (100) according to any one of claims 1 to 6, characterized in that it comprises at least two heat pump units (TFP1, TFP2, TPF3), the first heat exchangers (Ech_1) of the heat pump units being mounted in parallel on at least one oxidizing gas supply line (1). Steam cracking installation (100) according to claim 7, characterized in that it comprises a management system (22) for the heat pump units (TFP1, TFP2, TPF3) configured to: - control at least one heat pump unit (TFP1, TFP2, TPF3) to heat at least a fraction of the combustion gas flow rate circulating in at least one combustion gas supply line (1) to a target temperature, and / or - in a charging phase of at least one thermal storage system (24): circulate through the first heat exchanger (Ech_1) of at least one heat pump unit (TFP1, TFP2) the entire combustion gas flow rate circulating in at least one combustion gas supply line, and operate at least one heat pump unit (TFP1, TFP2) to heat this combustion gas flow rate to a target temperature,circulate through at least one thermal storage system a fraction of the combustion gas flow circulating in at least one combustion gas supply line, and control at least one other heat pump unit (TFP3), and optionally control said electric heating device (244), to heat this fraction taken from the outlet of the first heat exchanger (Ech_1) of said at least one other heat pump unit (TFP3); and - in a discharge phase of the at least one thermal storage system (24): circulate through at least one thermal storage system (24) all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line (1) to heat it to the target temperature or to a first temperature, this combustion gas flow being taken upstream of at least one heat pump unit (TFP1, TFP2, TFP3),optionally stop the electric heating device (244), and stop at least one heat pump unit (TFP3) used in the charging phase to heat the combustion gas entering at least one thermal storage system (24), stop at least one other heat pump unit (TFP1, TFP2) used in the charging phase to heat the combustion gas to the target temperature or command it to heat to a second temperature a fraction of the combustion gas flow which, mixed with the fraction of combustion gas flow at the first temperature, reaches the target temperature. A process for steam cracking hydrocarbons implemented in a steam cracking installation (100) according to any one of the preceding claims, characterized in that it comprises: - a step of cracking a hydrocarbon feedstock in the cracking furnace at a cracking temperature, this cracking temperature being obtained by the combustion in the burners of the steam cracking furnace of a mixture of combustion gas and hot oxidizing gas, in which the heating of the oxidizing gas before its entry into the burners is carried out by at least one heat pump unit and comprises: (a) supplying the first heat exchanger (Ech_1) of at least one heat pump unit with oxidizing gas to be heated,(b) supply the second heat exchanger (Ech_2) of at least one heat pump unit with a cold fluid to be cooled circulating in the second heat exchanger and originating from at least one cooling unit and / or at least one compression unit; (c) recover from the outlet of the first heat exchanger (Ech_1) of at least one heat pump unit a combustion gas at a target temperature, and recover from the outlet of the second heat exchanger (Ech_2) of at least one heat pump unit the cold fluid cooled to another target temperature. A process for steam cracking hydrocarbons according to claim 9, wherein, when the installation (100) comprises at least one thermal storage system (24), the heating of the combustion gas further comprises: (i) a charging phase in which at least one storage system (24) accumulates heat, during which: the entire flow of combustion gas circulating in at least one combustion gas supply line (1) is circulated through the first heat exchanger (Ech_1) of at least one heat pump unit (20, TFP1, TFP2, TFP3), and at least one heat pump unit (20, TFP1, TFP2, TFP3) is operated to heat this flow of combustion gas to a target temperature; a fraction of the flow of combustion gas circulating in at least one combustion gas supply line (1) is circulated through at least one thermal storage system (24). oxidizer,this fraction being taken from the outlet of the first heat exchanger (Ech_1) of at least one heat pump unit (20, TFP1, TFP2, TFP3), optionally the electric heating device (244) is activated to further heat said taken fraction, (ii) a discharge phase in which at least one thermal storage system (24) supplies heat, during which: all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line (1) is circulated through at least one thermal storage system (24) to heat it to the target temperature or to a first temperature, this gas flow being taken upstream of the first heat exchanger (Ech_1) of at least one heat pump unit, optionally the electric heating device (244) is stopped, and at least one heat pump unit (20, TFP1, TFP2, TFP3),or the remainder of the combustion gas flow circulating in at least one combustion gas supply line (1) is circulated through the first heat exchanger (Ech_1) of at least one heat pump unit, and at least one heat pump unit (20, TFP1, TFP2, TFP3) is operated to heat this remaining fraction of combustion gas flow to a second temperature, which, when mixed with the fraction of combustion gas flow at the first temperature, reaches the target temperature. Hydrocarbon steam cracking process according to claim 9 or 10, wherein, when the installation includes at least two heat pump units (TFP1, TFP2, TFP3), at least one heat pump unit is controlled to heat to a target temperature at least a fraction of the flow of combustion gas circulating in at least one gas supply line. A process for steam cracking hydrocarbons according to any one of claims 9 to 11, wherein, when the installation comprises at least two heat pump units (TFP1, TFP2, TFP3) and at least one thermal storage system (24): - during a charging phase of at least one thermal storage system (24): the entire flow rate of combustion gas circulating in at least one combustion gas supply line is circulated through the first heat exchanger (Ech_1) of at least one heat pump unit (TFP1, TFP2), and at least one heat pump unit (TFP1, TFP2) is operated to heat this flow rate of combustion gas to a target temperature; a fraction of the flow rate of combustion gas circulating in at least one combustion gas supply line (1) is circulated through at least one thermal storage system (24), and at least one other heat pump unit (TFP3),and optionally the electric heating device (244) is activated to heat this fraction taken from the outlet of the first heat exchanger (Ech_1) of this at least one other heat pump unit (TFP3), and - in a discharge phase of at least one thermal storage system (24): all or a fraction of the combustion gas flow circulating in at least one combustion gas supply line (1) is circulated through at least one thermal storage system (24) to heat it to the target temperature or to a first temperature, this combustion gas flow being taken upstream of at least one heat pump unit (TFP1, TFP2, TFP3), optionally the electric heating device (244) is stopped, and at least one heat pump unit (TFP3) used in the charging phase to heat the combustion gas entering at least one thermal storage system (24) is stopped.At least one other heat pump unit (TFP1, TFP2) used in the charging phase to heat the combustion gas to the target temperature is stopped, or it is activated to heat a fraction of the combustion gas flow to a second temperature, which, when mixed with the fraction of combustion gas flow at the first temperature, reaches the target temperature.

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