STEAM CRACKLING INSTALLATION AND PROCESS WITH REACTOR-HEAT EXCHANGER

Abstract

The invention relates to a steam cracking installation and process employing at least one heat exchanger reactor. According to the invention, the heat required for the steam cracking reaction is supplied by a working fluid circulating in at least one closed-loop circuit (130), this circuit being connected on one side to an inlet of at least one heat exchanger reactor and on the other side to the corresponding outlet. This circuit (130) comprises: at least one heating device (131, 132) for the working fluid located upstream of at least one heat exchanger reactor (112) relative to the working fluid circulation; at least one heat exchanger (134, 135) located downstream of at least one heat exchanger reactor (112) and upstream of at least one heating device (131, 132); and at least one working fluid circulation device (138). Figure for the abbreviation: Figure 1

Description

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

[0001] The present invention relates to a steam cracking installation and process employing at least one heat exchanger reactor. Technological background

[0002] The hydrocarbon steam cracking process makes it possible to produce light olefins, and more particularly 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 the carbon-hydrogen and / or carbon-carbon bonds and produce unsaturated hydrocarbons in 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"), in order 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 steam cracking, which generates significant CO2 emissions. Furthermore, in conventional steam cracking furnaces, the heat resulting from gas combustion is transferred to the tubes carrying the feedstock to be cracked 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 radiation heat transfer is not completely homogeneous, localized temperature spikes can occur, promoting coking of the reaction tubes and necessitating more frequent plant shutdowns.

[0004] Increasingly important 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, and 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 cost environmental. There is also a need for a steam cracking installation and process that limits localized temperature increases.

[0006] Document FR 2 675 498 A1 describes a steam cracking process that partially overcomes these drawbacks. To this end, the steam cracking reaction is carried out inside a shell-and-tube heat exchanger reactor. The thermal energy required for the reaction is supplied by the combustion of a gas mixture, which is partially performed inside the heat exchanger reactor. The gas mixture to be burned is produced by a gas generator and then enters the heat exchanger reactor, optionally 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 substantially constant temperature in the reaction tubes, injection tubes are arranged inside the heat exchanger reactor.

[0007] The process described in this document has the disadvantage of requiring the combustion of gases emitting CO2. Furthermore, since part of the gas combustion occurs inside the heat exchanger reactor, additional devices must be provided in the latter to obtain a homogeneous temperature, which complicates the manufacture of this reactor.

[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 plant comprising:

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

[0011] - a cooling section adapted for performing quenching, connected to the means evacuation 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 an inlet of the tubes and an inlet of the shell, and on the other side to the corresponding outlet of the tubes or the shell, each circuit comprising:

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

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

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

[0017] Thus there is no combustion inside the heat exchanger reactor so that the structure of the latter can be simplified and the risk of hot spots is limited.

[0018] 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.

[0019] 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.

[0020] Preferably, at least one heating device is a heating device that does not emit CO2, either because there is no combustion, the heating device requiring only an electrical supply, or because combustion does not emit CO2.

[0021] The heating device may be in the form of a boiler, a furnace or a superheater, preferably not emitting CO2.

[0022] Advantageously, at least one heating device can 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, a hydrogen furnace.

[0023] 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.

[0024] 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.

[0025] Advantageously, the at least one closed-loop circuit may include a first and a second heat exchanger mounted in series downstream of the at least one heat exchanger reactor, the first heat exchanger being connected to a water supply line, in particular in the form of steam, and adapted to heat it, and the second heat exchanger being connected to a supply line of a component of the gas mixture, particularly hydrocarbons, and adapted to preheat it before it enters 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.

[0026] Advantageously, in another embodiment allowing for improved 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 at least one heat exchanger reactor, the first heat exchanger being connected to the circuit, on the one hand, upstream, in particular immediately upstream, of at least one heating device and downstream of the second heat exchanger, and on the other hand, downstream, in particular immediately downstream, of at least one heat exchanger reactor and upstream of the second heat exchanger, the second heat exchanger being connected to a water supply line, in particular in liquid form, and adapted to preheat water using the working fluid. The closed-loop circuit 130 thus passes twice through the first heat exchanger.

[0027] In a variant of this embodiment, the installation may further comprise at least two preheating heat exchangers: the first preheating heat exchanger being connected on one side to a heat exchanger of the cooling section to receive a cooled gaseous effluent, and on the other side 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 one side to the heat exchanger of the cooling section to supply it with at least one constituent of the gaseous mixture, in particular hydrocarbons, preheated, and on the other side to the first preheating heat exchanger to receive the further cooled gaseous effluent.

[0028] These preheating heat exchangers thus serve to preheat the constituents of the gas mixture before their introduction into the heat exchanger reactor, 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.

[0029] 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.

[0030] Advantageously, the cooling section may comprise a first and a second heat exchanger mounted in series: the first heat exchanger being then 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 fluid circulation, so as to preheat a constituent of the gas mixture, the second heat exchanger being connected on one side to the first heat exchanger and on the other side 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.

[0031] In particular, the preheating heat exchanger can be connected to the first heat exchanger of the cooling section by (another) closed loop circuit in which another working fluid circulates, typically water in the form of vapor and / or liquid.

[0032] 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.

[0033] The invention also relates to a steam cracking process of a gaseous mixture of a hydrocarbon feedstock and water vapor, in particular 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, in particular rich in ethylene, and a rapid cooling phase of said effluent in a cooling section under suitable conditions, and said cooled steam cracking effluent is recovered.

[0034] According to the invention: - the gaseous mixture, preferably pre-heated, is introduced into at least one pressure shell and tube heat exchanger reactor via an inlet of the latter chosen from a tube inlet and a shell inlet, and the gaseous mixture is circulated inside the tubes or the shell of said heat exchanger reactor, - The heating phase of the gas mixture is carried out in at least one heat exchanger reactor according to the following steps: (a) A working fluid is circulated within a closed-loop circuit, this circuit being connected on one side to the other inlet of at least one heat exchanger reactor selected from a tube inlet and a shell inlet, and on the other side to the corresponding tube or shell outlet, and said working fluid is heated to a target temperature higher than the temperature at which the mixture gaseous gas must be heated by means of at least one closed-loop circuit heating device. (b) the working fluid is introduced at the target temperature into the heat exchanger reactor, 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.

[0035] Advantageously, the gas mixture can be circulated inside the tubes of at least one heat exchanger reactor.

[0036] Advantageously, the method according to the invention may further comprise at least one of the following features:

[0037] - 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 1000 to 1400 °C. - the working fluid pressure is from 30 barg to 80 barg.

[0038] 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 cool it rapidly and preheat the gas mixture before it enters at least one heat exchanger reactor.

[0039] 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.

[0040] In particular, the following embodiments may be envisaged:

[0041] - the working fluid having circulated in at least one heat exchanger reactor is sent to a first heat exchanger of the closed loop circuit to heat water vapor, 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 in a heat exchanger of the cooling section.

[0042] - 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 the working fluid upstream of its heating by at least one device The heating system then passes to a second heat exchanger in the same circuit to heat water, specifically before its vaporization in a first preheating heat exchanger that receives 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 mixes with the dilution steam exiting the first preheating heat exchanger. The mixture is then preheated in a heat exchanger in the cooling section.

[0043] - the working fluid having circulated in at least one heat exchanger reactor is sent to a first heat exchanger of the closed loop circuit to heat steam, in particular before preheating it in a heat exchanger of the cooling section, then the working fluid is sent to a second heat exchanger of said circuit to heat another constituent of the gas mixture (in particular hydrocarbons), the hot effluent having circulated in at least one reactor-heat exchanger being sent to a first and a second heat exchanger mounted in series of the cooling section, the second heat exchanger of the cooling section receiving on the one hand the constituent of the gas mixture preheated first by the second heat exchanger of said circuit and then by a preheating heat exchanger, and on the other hand the dilution steam heated by the first heat exchanger of said circuit.The preheating exchanger is advantageously connected to the first exchanger of the cooling section by another closed-loop circuit in which another working fluid circulates, typically water in liquid and / or vapor form.

[0044] 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 carried out on one of the heat exchanger reactors while the others are in operation. 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 Description of the figures

[0045] The invention is now described with reference to the accompanying, non-limiting drawings, in which:

[0046] Figure [1] schematically represents a steam cracking installation according to a first embodiment,

[0047] Figure 2 schematically represents a steam cracking installation according to a second embodiment,

[0048] Fig. 3 schematically represents a steam cracking installation according to a third embodiment.

[0049] In the figures, the same elements are designated by the same references.

[0050] Fig. 1 represents a steam cracking installation 100 comprising a heating section 110 including at least one shell and tube heat exchanger reactor 112, here only one, and a cooling section 120.

[0051] The heat exchanger reactor 112 (also referred to as the "heat exchanger reactor" in the following) includes a tube inlet 113, a tube outlet 114, a shell inlet 115 and a shell outlet 116.

[0052] The reactor-exchanger 112 further includes means for supplying a suitable gaseous mixture comprising at least one hydrocarbon. These supply means here include a conduit 117 connected in this example to the inlet 113 of the tubes.

[0053] The reactor-exchanger 112 also includes means for venting a hot gaseous effluent. These venting means include a pipe 118 connected in this example to the outlet 114 of the tubes.

[0054] The invention is not, however, limited to this embodiment, and it could be envisaged that the conduits 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 construction of the reactor. Indeed, given the relatively high steam cracking pressures, implementing the reaction in the calender would require significantly thickening its walls.

[0055] A reactor-exchanger 112 typically has an elongated shape, generally arranged vertically.

[0056] 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.

[0057] 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 via 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 approximately 100 to 300 ms.

[0058] The cooling section 120 adapted to carry out quenching is connected to the evacuation means 118 of the exchange reactor 112.

[0059] In this embodiment, the cooling section includes a heat exchanger 122 receiving the gaseous effluent from the reactor-exchanger 112.

[0060] According to the invention, the installation further comprises a closed loop circuit 130 in which a working fluid circulates, this circuit being connected on the one hand to the inlet 115 of the shell of the reactor-exchanger 112 and on the other hand to the corresponding outlet 116 of the shell.

[0061] This circuit 130 comprises in this embodiment:

[0062] 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,

[0063] two heat exchangers 134, 135, here mounted in series, located downstream of the reactor-exchanger 112 and upstream of the heating devices 131, 132,

[0064] a device for circulating the working fluid 138.

[0065] 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.

[0066] In this embodiment, the first heating device 131 is an electric boiler and the second heating device 132 is an electric superheater.

[0067] The invention is not limited, however, by the number, nature, and arrangement of the heating devices, provided that the device(s) do not emit CO2. Preferred heating devices include electric heating devices that produce heat by Joule heating, microwaves, shock waves, plasma, and / or induction, as well as 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, furnace, or superheater. When several devices are present, they may be connected in series and / or in parallel.

[0068] 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.

[0069] The embodiment of [Fig.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.

[0070] The steam cracking of a hydrocarbon feedstock using the installation shown [Fig.1] is now described.

[0071] This steam cracking includes in particular a heating phase implemented in the heating section 110 under appropriate conditions, which delivers a hot steam cracking effluent, and a rapid cooling phase of said effluent implemented in the cooling section 120 under appropriate conditions.

[0072] Typically, at the inlet of the heating section 110, the temperature of the gas mixture can be from 600 to 680 °C. The temperature of the gas effluent at the outlet of the heating section 110 is typically from 800 to 900 °C. The residence time of the gas mixture in the heating section is short, typically from 100 to 300 ms. In the heating section, the gas mixture is, for example, maintained at a pressure of 1.5 to 3 bar.

[0073] 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.

[0074] The working fluid follows the following path in circuit 130. Pump 138 sends the working fluid, here water in a liquid state, into the electric boiler 131 in in which steam is produced, for example here at a temperature of 225 °C and a pressure of 25 bar. Then, the working fluid (steam at 225 °C) enters the superheater 132 and exits superheated, for example at 1200 °C. The superheated working fluid then enters the shell of the reactor-exchanger 112 through inlet 115 and circulates within it. The superheated working fluid cools as it passes through the reactor-exchanger 112, transferring its heat to the reactor-exchanger tubes. The working fluid thus exits at a temperature lower than its inlet temperature, here at approximately 700 °C. At the outlet of the reactor-exchanger, the working fluid is sent, in particular directly, into the first exchanger 134. This receives steam from a pipe 1, for example at 180 °C, which it heats, for example to 500 °C.The dilution steam exiting the first heat exchanger 134 is discharged via a line 2 which joins a line 4 through which the hydrocarbon feed circulates. Thus, the first heat exchanger 134 brings steam to a temperature suitable for use as dilution steam to be mixed with the hydrocarbon feed 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 500 °C dilution steam 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, which quenches the gaseous effluent. The gaseous mixture then enters the tubes of the reactor-exchanger 112 through inlet 113. These tubes are heated primarily by convection, at approximately the temperature of the working fluid circulating in the shell. The working fluid can flow in the same direction as the gaseous mixture in the tubes, thus promoting a greater heat input at the very beginning of the reaction.The gas mixture thus undergoes a steam cracking reaction, producing a gaseous effluent exiting the reactor-exchanger 114 through outlet 114 and discharged via 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, fractionation sections, well known to those skilled in the art and which will not be detailed further.

[0075] The invention is of course not limited by the nature of the hydrocarbons that can be steam cracked. The installation and the process according to the invention can thus be implemented for the steam cracking of various hydrocarbon feedstocks of fossil origin such as ethane, liquefied petroleum gases (propane, butane), naphtha, diesel and vacuum distillate, of various hydrocarbon feedstocks of biological origin, such as ethane, propane, butanes, naphtha and distillates produced during the hydrotreating / hydrocracking of fatty acid esters (for example triglycerides), biomass pyrolysis oils and / or biomass hydrothermal liquefaction oils, or even other hydrocarbon feedstocks obtained by pyrolysis, hydrothermal liquefaction and / or hydrocracking of plastic waste.

[0076] The embodiment of [Fig. 2] differs from that of [Fig. 1] primarily in the cooling section 120 and the preheating of the hydrocarbon feed. In this embodiment, the cooling section 120 comprises a first heat exchanger 124 and a second heat exchanger 126 connected in series: the effluent exiting the reactor-exchanger 112 through 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 comprises 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 feed from 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.

[0077] This embodiment differs from the previous one essentially by the cooling of the effluent exiting the heating section 110 and by the preheating of the components of the gas mixture. The working fluid circulates in the circuit 130 as described with reference to [Fig. 1].

[0078] Thus, the effluent exiting the reactor-exchanger 112 via the pipe 118 is first cooled in the first exchanger 124 by the cold working fluid circulating in the loop 142, here liquid water. During its passage through this first heat exchanger 124, the water from the circuit 142 vaporizes into high-pressure steam, for example at 325 °C and 120 bar, and returns to the preheating heat exchanger 140 in which it preheats the hydrocarbon feedstock, here a naphtha, which has been preheated (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 flows. The resulting gas mixture is then sent to the second heat exchanger 126 of the cooling section 120 where it is heated to approximately 600 °C by the partially cooled effluent from the first heat exchanger 124 of the cooling section 120.

[0079] The embodiment of [Fig.3] differs from that of [Fig.1] essentially by the circuit 130 supplying the hot working fluid to the heating section 100 and by the preheating of the hydrocarbon charge.

[0080] In this embodiment, the circuit 130 comprises:

[0081] a heating device 133 for the working fluid, located upstream of the reactor-exchanger 112 with respect to the working fluid circulation,

[0082] two heat exchangers 134', 135', here mounted in series, located downstream of the reactor-exchanger 112 and upstream of the heating device 133,

[0083] a device for circulating the working fluid 139.

[0084] Unlike the embodiment of [Fig. 1], in this embodiment, the first heat exchanger 134' of the circuit serves 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' serves 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 the 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 discharged from the preheating heat exchanger 160 by a line 12, then conveyed to the usual subsequent cooling, compression, fractionation sections to recover the products of interest.

[0085] 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.

[0086] 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 the outlet 116. The preheated working fluid is then further heated in the heating device 133 before entering the reactor-exchanger 12 through the inlet 115, where it transfers heat to the tubes for the implementation of 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'.

[0087] The hydrocarbon feedstock is first preheated by the second preheating heat exchanger 160 using the 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 using the residual heat from the effluent exiting the heat exchanger 122 of the cooling section. The resulting gaseous 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 reactor-exchanger 112, the hot effluent is rapidly cooled in heat exchanger 122, then further cooled in preheating heat exchangers 150 and 160, which respectively heat dilution steam and the hydrocarbon feedstock.

[0088] 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 above. If water is used as the working fluid, the heating devices described with reference to [Fig. 1] may be used.

[0089] In the various embodiments, other arrangements of one or more heating devices may nevertheless be provided, provided that they enable the working fluid to be heated to a target temperature sufficiently high so that the gas mixture circulating inside at least one heat exchanger-reactor reaches the desired reaction temperature. Those skilled in the art can determine this target temperature through tests and / or modeling, based on the feedstock to be steam cracked and the characteristics of the heat exchanger-reactor.

[0090] It should also be noted that the preheating of the hydrocarbon feed as described with reference to [Fig. 2] can also be implemented in the embodiment of [Fig. 3]. In this case, the preheating heat exchanger 140 described in reference to [Fig.2] is located immediately downstream of the second preheating heat exchanger 160.

[0091] 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.

[0092] The present invention thus consists of using the working fluid as a heat transfer fluid (such as CO2, steam, argon, helium, etc.) which is heated by a CO2-free heating device to a target temperature, typically above 900 °C, generally under increased pressure (>20 bar), and sent to a heat exchanger reactor, preferably to its shell, where it exchanges heat, preferably with the tubes in which the steam cracking reaction takes place. Subsequently, the heat transfer fluid, having lost temperature, is used to vaporize and / or preheat the feedstock, the dilution steam, or both, and is finally recovered at a reduced temperature and pressure (due to the pressure drop on the heat exchanger equipment).This heat transfer fluid at reduced temperature and pressure is repressurized by compression or pumping (in case of fluid condensation), and reheated using the heating device to the target temperature to close the cycle.

[0093] The invention thus offers the following advantages:

[0094] A decarbonization of 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,

[0095] improved control of the skin temperature of the tubes in the heat exchanger reactor, making it possible to limit coking,

[0096] 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.

Claims

Demands

1. A steam cracking plant (100) comprising: - at least one shell and tube heat exchanger (112), each heat exchanger comprising means for supplying (117) a suitable gaseous mixture comprising at least one hydrocarbon, 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, 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 the at least one heat exchanger selected from a tube inlet (113) and a grille inlet (115),and on the other hand at the corresponding outlet (114, 116) of the tubes or the shell, each circuit (130) comprising: at least one heating device (131, 132; 133) for the working fluid located upstream of at least one heat exchanger reactor (112) with respect to the working fluid circulation, at least one heat exchanger (134, 135; 134', 135') located downstream of at least one heat exchanger reactor (112) and upstream of at least one heating device (131, 132; 133), at least one working fluid circulation device (138, 139).

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

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

4. A steam cracking plant according to any one of the preceding claims, characterized in that at least one heating device is 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, a hydrogen furnace.

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

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

7. 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, the first heat exchanger (134') being connected to the circuit (130) on the one hand upstream of at least one heating device (138, 139) 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 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 the latter,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 connected in series: the first heat exchanger (124) being connected on the one hand to the exhaust means (118) of at least one heat exchanger reactor (112) and on the other hand to a preheating heat exchanger (140) located upstream of the at least one heat exchanger reactor (112) with respect to the fluid circulation, so as to preheat a component of the gas mixture, the second heat exchanger (126) being connected on the one hand to the first heat exchanger (124) and on the other hand to the preheating heat exchanger (140) and to at least one heat exchanger of

10. heat (135) from the closed loop circuit (130), to receive at least one component of the preheated mixture. A steam cracking process for a gaseous mixture of a hydrocarbon feedstock and water vapor, 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 preheated, 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), (b) the working fluid at the target temperature is introduced into the heat exchanger reactor (112), the cooled working fluid is recovered and reinjected into the closed-loop circuit (130) upstream of at least one heating device (131, 132; 133) of said circuit, and a hot steam cracking effluent is recovered and immediately sent to the cooling section (120).

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

12. A process according to claim 10 or 11, characterized in that it comprises at least one of the following features: - the 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 having 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 before its entry into at least one heat exchanger reactor (112).

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