ELECTRICAL INSTALLATION FOR GAS HEATING, PARTICULARLY FOR A STEAM CRACKLING FURNACE

Abstract

The invention relates to an electric gas heating system (1), particularly for heating a combustion gas supplying a steam cracking furnace. The system comprises, in particular, mounted in series on a gas supply line (3): - a first electric heating system (10), - a second electric heating system with thermal storage (20) equipped with at least one thermal storage device (210) containing at least one thermal storage medium selected from a solid medium and a liquid medium, and at least one heating device (220) for the thermal storage medium. A control system (40) is configured to, during a charging phase, heat the thermal storage medium so that it accumulates heat and heat the gas by means of the first electric heating system and, during a discharging phase, transfer the heat accumulated by the thermal storage medium to the gas. Figure for the abstract: 1

Description

Title of the invention: ELECTRICAL INSTALLATION FOR GAS HEATING, PARTICULARLY FOR A STEAM CRACKLING FURNACE Technical field of the invention

[0001] The present invention relates to an electric gas heating system, particularly for heating the combustion gas of a steam cracking furnace fed with combustion gas. The invention also relates to a hydrocarbon steam cracking system and process using the electric heating system according to the invention. 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.A steam cracking process thus requires inputs of heat (energy injection to increase the temperature and provide the enthalpy of reaction) and cold (energy extraction to lower the temperature) to fractionate, and significant amounts of energy, much of which is currently supplied by fossil fuels.

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

[0004] Among the heat inputs required for a steam cracking process is the heating of the combustion air for the burners of a steam cracking furnace. To minimize the amount of fuel needed to provide thermal energy to the charge to be cracked, the combustion air must enter the burners at a temperature above 200 °C, typically from 300 to 600 °C. This air is electrically heated. Using an oxidizer is a possibility but expensive, especially when the cost of electricity is high.

[0005] There is therefore a need to heat a gas, and in particular the combustion gas of a steam cracking furnace, to a high temperature while reducing the economic, energy and environmental impact. Summary of the invention

[0006] To this end, the invention proposes an electrical gas heating installation implementing an electric heating system with thermal storage.

[0007] A first object of the invention relates to an electrical gas heating installation comprising: - at least one gas supply line, - a first electric heating system, mounted on at least one gas supply line, - a second electric heating system with thermal storage mounted on at least one gas supply line, downstream of the first heating system with respect to the gas flow, and comprising: - at least one thermal storage device containing at least one thermal storage medium selected from a solid medium and a liquid medium, - optionally at least one heating device for at least one thermal storage medium, and further including: - according to a first configuration (i) a bypass circuit of at least one gas supply line passing through at least one thermal storage device containing only at least one solid medium, or - according to a second configuration (ii) a heat exchanger in which the liquid medium and the gas supplied by at least one supply line circulate, and a circuit in which the liquid medium circulates, this circuit comprising at least one thermal storage device and the heat exchanger.

[0008] The electric heating installation according to the invention further comprises a management system for the first and second electric heating systems, configured, in particular programmed, to: (a) in a charging phase in which at least one thermal storage medium of the second heating system accumulates calories, operate the first heating system to heat the gas to a first temperature T1, and (a1) operate the heating device to heat at least one thermal storage medium, and / or (a2) use at least a fraction of the gas heated by the first heating system to heat the thermal storage medium, (b) in a discharge phase in which at least one thermal storage medium of the second heating system releases heat, command the shutdown of the optional heating device, operate the first heating system to heat the gas to a second temperature T2, and: in the first configuration (i) circulate the entire gas flow at the second temperature T2 in the bypass circuit through the thermal storage device containing the solid medium to heat the gas from the second temperature T2 to a predetermined temperature Tp, or circulate a fraction of the gas flow at the second temperature T2 in the bypass circuit through the thermal storage device containing the solid medium to heat this gas fraction to a third temperature T3, which, in mixing with the remaining fraction of gas flow reaches the predetermined temperature Tp, or in the second configuration (ii) circulate the liquid medium through at least one thermal storage device and then into the heat exchanger to heat the gas from the second temperature T2 to the predetermined temperature Tp.

[0009] This arrangement makes it possible to implement the charging phase while electricity is cheaper and / or comes from decarbonized sources (wind, solar, nuclear power plant, hydroelectric, ...), which makes it possible to decarbonize the electrical consumption of the installation and / or reduce operating costs.

[0010] The predetermined temperature Tp may be equal to or less than a target temperature Te. The target temperature Te is defined as a temperature to be reached at the outlet of the installation according to the invention. This target temperature Te can be determined according to the use of the installation according to the invention.

[0011] The first temperature Tl can be greater than or equal to the temperature predetermined temperature Tp or the target temperature Tp, or be lower than either. During the charging phase, when case (a2) is in and at least a fraction of the gas heated by the first heating system is used to heat the thermal storage medium, the temperature Tl is advantageously higher than a storage temperature, the latter being advantageously higher than the predetermined temperature Tp or the third temperature T3, and preferably higher than the target temperature Te.

[0012] The second temperature T2 is typically lower than the predetermined temperature Tp. The third temperature T3 is typically higher than the second temperature T2 and lower than the predetermined temperature Tp or the target temperature Te.

[0013] Generally, during the charging phase, at least one thermal storage medium is heated to a storage temperature Ts (temperature reached by at least one thermal storage medium at the end of the charging phase). This The storage temperature Ts can advantageously be higher than the predetermined temperature or the target temperature, or even higher than the third temperature T3 used in the discharge phase in the first configuration (i). During the discharge phase, at least one thermal storage medium that is at temperature Ts can then heat the gas from the second temperature T2 to the predetermined temperature Tp or to the third temperature T3, depending on the configuration, as previously explained.

[0014] Advantageously, the heating device of the second thermal heating system can be an electric heating device, such as a Joule effect, induction, microwave, plasma, shock wave heating device or a combination of these devices, preferably a Joule effect and / or induction heating device.

[0015] Advantageously, the first electric heating system may comprise one or more of the following components mounted in series and / or in parallel on at least one gas supply line: - a heat pump connected on one side to the gas supply line in order to transmit heat to it, and on the other side to a pipe in which a hot fluid circulates in order to receive heat from the latter, - a mechanical vapor recompression system, comprising at least one mechanical steam compression stage, at least one first heat exchanger receiving steam produced by at least one mechanical compression stage and connected to the gas supply line so as to transmit heat to it, a second heat exchanger receiving heat from a hot fluid and producing steam supplying at least one mechanical compression stage, - an electric heating device.

[0016] The electric heating system can be as described above. Advantageously, one or more heat pumps (in series and / or parallel) followed by one or more electric heating devices, or one or more electric heating devices, may be used. Most often, the first electric heating system comprises two or three of these components connected in series, for example, a heat pump followed by at least one electric heating device, most often two or three. The use of a heat pump makes it possible to utilize a hot fluid or waste heat from a unit, for example, a steam cracking unit or any other heat-producing unit. A heat pump also makes it possible to minimize the electrical consumption associated with the heating operation by utilizing a waste heat source, either directly or via a heat transfer fluid.

[0017] In a first embodiment, in the first configuration, the second electric heating system may comprise: - the bypass circuit comprising at least one thermal storage device containing only the solid medium and, - at least one solid medium heating device, optionally mounted on a bypass pipe connected to the bypass circuit in parallel with at least one thermal storage device.

[0018] Preferably, the second electric heating system can then include a single thermal storage device.

[0019] The management system can then be further configured to operate the second heating system in the following manner, and in particular to: - During a charging phase, (a1) circulate gas through at least one thermal storage device and operate the heating device of the second heating system, and / or (a2) operate the first heating system to heat the gas to the first temperature T1 and use at least a fraction of the gas to heat the thermal storage medium, - During a discharge phase, circulate the gas through at least one thermal storage device, with the heating device of the second heating system being off.

[0020] In this first embodiment of the first configuration, the electric heating installation according to the invention may then include a third electric heating system mounted on the gas supply line, in parallel with the second electric heating system. This is particularly advantageous when, during the charging phase, the gas is heated by the first heating system to a first temperature Tl which is lower than the target temperature Te.

[0021] The management system can then be further configured to: - During the charging phase, operate the first and third electric heating systems to heat the gas to the predetermined temperature Tp, - In the discharge phase, operate the first electric heating system to heat the gas to the second temperature T2, in particular lower than the predetermined temperature Tp, then circulate all or a fraction of the gas flow through the thermal storage device to heat all of the gas flow to the predetermined temperature Tp or to heat the fraction of the gas flow to the third temperature T3 which, in mixing with the remaining fraction of gas flow, reaches the predetermined temperature Tp.

[0022] Preferably, this third thermal heating system may comprise one or more electric heating devices, for example, a single one. This electric heating device may be as previously defined.

[0023] In a second embodiment, in the second configuration, the circuit in which a liquid medium circulates may include at least one thermal storage device, the heat exchanger and the liquid medium heating device.

[0024] The management system can then be further configured to operate the second heating system, and in particular to: - In a charging phase, (a1) circulate the liquid medium in this circuit and operate the heating device to heat it before it enters at least one thermal storage device, and optionally (a2) operate the first heating system to heat the gas to the first temperature T1 and use at least a fraction of the gas to heat the thermal storage medium via the heat exchanger, - During a discharge phase, circulate the liquid storage medium in this circuit, and control the shutdown of the heating device.

[0025] In a variant of this second embodiment, the circuit of the second electric heating system may include a single thermal storage device. The liquid medium heating device may then be installed on a bypass line mounted in parallel with the thermal storage device or integrated into it (the bypass line is then omitted). During the charging phase, the liquid medium may then circulate in a loop formed by the bypass line on which the heating device and the thermal storage device are installed, while during the discharging phase, the liquid medium circulates in a loop formed by the circuit containing the thermal storage device and the heat exchanger. It should be noted that the thermal storage device may also contain a solid medium.A thermal storage device containing layers of liquid thermal storage media at different temperatures can be advantageously used, with the temperature of the layers increasing from bottom to top.

[0026] In another variant of the second embodiment, in the second configuration, the circuit may comprise, connected in series in one direction of liquid medium flow, a first thermal storage device, a second thermal storage device, and the heat exchanger, with at least one liquid medium heating device being integrated into each thermal storage device or disposed between the first and second thermal storage devices. During the charging phase, the liquid medium then circulates in a loop comprising the two thermal storage devices and the heating device(s): the liquid medium The liquid from a cooler thermal storage device is then heated by the heating device before being stored in the warmer thermal storage device. During the discharge phase, the liquid circulates through the circuit from the warmer storage device to the heat exchanger, while the heating device is off. The management system can then be configured to operate the second heating system as previously described.

[0027] In a third embodiment, in the second configuration, the circuit may include, connected in series in one direction of liquid medium flow, a first thermal storage device, optionally a second thermal storage device, and the heat exchanger. At least one liquid medium heating device is mounted on at least one gas supply line, upstream of the heat exchanger of the second electric heating system. The gas heated by the heating device then heats the liquid medium during the charging phase via the heat exchanger. During the discharging phase, this heating device is switched off. The control system can then be configured to operate the second heating system as previously described.

[0028] When the second electric heating system operates with a liquid thermal storage medium, in the second configuration, the installation according to the invention may advantageously include a third electric heating system mounted on at least one gas circulation line downstream of the heat exchanger of the second electric heating system. This third electric heating system can advantageously be used during the charging phase to maintain the liquid medium circulating in the heat exchanger at an operating temperature, for example, a temperature at which it is liquid. It can also allow the gas to reach the target temperature Te during the charging phase when the initial temperature Tl at the outlet of the first electric heating system is insufficient (i.e., below the target temperature).

[0029] The electrical gas heating system according to the invention can advantageously be integrated into a hydrocarbon steam cracking furnace comprising a radiant heating zone equipped with burners connected to at least one fuel gas supply line and at least one oxidizing gas supply line. The system according to the invention is then mounted on at least one oxidizing gas supply line to heat the oxidizing gas before it enters the furnace.

[0030] The invention also relates to a steam cracking installation comprising a steam cracking furnace, the steam cracking furnace and an electrical heating installation according to the invention, the furnace comprising a radiation zone equipped with burners connected to at least one combustible gas supply line and to the minus a combustion gas supply line and the installation according to the invention being mounted on the latter.

[0031] The invention also relates to a process for steam cracking hydrocarbons characterized in that it comprises: - a cracking step of a hydrocarbon feedstock implemented at a cracking temperature in a steam cracking plant according to the invention, 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 the electrical gas heating plant according to the invention and comprises: - supply the first electric heating system with gas to be heated, optionally, the combustion gas entering the first electric heating system being at a temperature ranging from ambient temperature to 280 °C, and - in a charging phase in which the thermal storage medium of the second heating system accumulates calories, operate the first heating system to heat the gas to a first temperature T1, and (a1) operate the heating device to heat the thermal storage medium, and / or (a2) use at least a fraction of the gas heated by the first heating system to heat the thermal storage medium, - in a discharge phase in which the thermal storage medium of the second heating system releases heat, command the shutdown of the optional heating device, operate the first heating system to heat the combustion gas to a second temperature T2, and, in the first configuration (i) circulate the entire gas flow at the second temperature T2 through the bypass circuit via the thermal storage device containing the solid medium and heat the gas from the second temperature T2 to a predetermined temperature Tp, or, circulate a fraction of the gas flow at the second temperature T2 through the bypass circuit via the thermal storage device containing the solid medium to heat this gas fraction to a third temperature T3, which, when mixed with the remaining fraction of the gas flow, reaches the predetermined temperature Tp, or in the second configuration (ii) circulate the liquid medium through T at least one thermal storage device and then into the heat exchanger to heat the combustion gas from the second temperature T2 to the predetermined temperature Tp.

[0032] The steam cracking furnace, the installation and the steam cracking process according to the invention are particularly suitable for the steam cracking of ethane but can It 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 hydrocarbon feedstocks can be bio-based hydrocarbons, 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 hydrocarbon feedstocks can be hydrocarbons obtained by pyrolysis, hydrothermal liquefaction, or hydrocracking of plastic waste. Detailed description of the invention Description of the figures

[0033] The invention is now described with reference to the accompanying, non-limiting drawings, in which:

[0034] [Fig-1] Fig. 1 schematically represents an electrical installation of heating a gas and a steam cracking furnace according to an embodiment of the invention.

[0035] [Fig.2] Fig.2 schematically represents an electrical installation for heating a gas and a steam cracking furnace according to another embodiment of the invention.

[0036] [Fig.3] Fig.3 schematically represents an electrical installation for heating a gas and a steam cracking furnace according to another embodiment of the invention.

[0037] [Fig.4] Fig.4 schematically represents an electrical installation for heating a gas and a steam cracking furnace according to another embodiment of the invention.

[0038] In the figures, the same elements are designated by the same references.

[0039] The terms "upstream" and "downstream" are used in relation to the flow of fluids, symbolized by arrows on the figures.

[0040] The various units of a steam cracking plant include many components requiring either an electrical power supply, or a thermal power supply, or both.

[0041] 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).

[0042] The thermal energy required for the steam cracking reaction is supplied by combustion of combustible gas with an oxidizer (air, etc.). Approximately 40 to 50% of the combustion heat is absorbed in a radiation zone of the steam cracking furnace, the remainder passes to a convection zone where the majority of the sensible heat of the combustion gases is exchanged to preheat hydrocarbons and / or water and / or steam via at least one heat exchanger.

[0043] In the present invention, the oxidizing gas, typically air, supplying the burners of the steam cracking furnace is heated by means of an electric heating installation according to the invention.

[0044] Fig. 1 schematically represents an electrical heating installation according to an embodiment of the invention, here allowing the heating of a combustion gas supplying a steam cracking furnace, in which a steam cracking step takes place.

[0045] Typically, the steam cracking furnace 110 comprises a lower radiant section 110a and an upper convection section 110b. The heat from the radiant section 110a 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 110 thus comprises one or more fuel supply lines 2 and one or more oxidizer supply lines 3 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 110.

[0046] The hydrocarbon feedstock and dilution steam are injected into at least one heat exchanger tube bundle (not shown) located in the convection zone 110b. The hydrocarbon feedstock and dilution steam may be preheated separately and then mixed and further preheated in the 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 110a. By means of the burners in the radiation zone, the tube reactors are further heated to initiate thermal cracking. The effluent temperature at the outlet of the tube reactors is typically between 800 and 900°C.

[0047] According to the invention, the combustion gas supply line 3 is equipped with an electric heating installation 1 comprising a first electric heating system 10 and a second electric heating system 20 connected in series in the direction of combustion gas flow. The installation 1 according to the invention thus comprises a portion of the combustion gas supply line 3, which may be connected to it or form part of it.

[0048] The first electric heating system 10 may comprise one or more components selected from a heat pump and an electric heating device connected in series and / or in parallel. In the example shown [Fig. 1], the first electric heating system 10 includes here a PACH heat pump. In this example, the heat pump includes a circuit 100 in which a working fluid circulates, preferably a gas (for example CO2, a hydrocarbon, in particular an alkane such as pentane, water, ammonia, a refrigerant such as a hydrofluoroolefin or HFO, or a hydrochlorofluoroolefin or HCFO, ...) equipped with two heat exchangers Ech_1 and Ech_2. The heat pump also usually includes a compressor and an expansion device (calibrated orifice, electronic expansion valve, turbine, semi-closed valve, ...) not shown.The working fluid circulating in the first heat exchanger Ech_1 transfers heat to the combustion gas circulating in the first heat exchanger Ech_1 and supplied by the combustion gas supply line 3, while the working fluid circulating in the second heat exchanger Ech_2 receives heat from at least one hot fluid circulating in the second heat exchanger and originating, for example, from the steam cracking plant to which the furnace belongs. This hot fluid circulating in a line 4 can, for example, come from the water quenching tower of the steam cracking plant, or from ambient air, a geothermal source, the sea, or a return water from a cooling unit.

[0049] As a replacement for the PACH and / or the electric heating device, or in combination with it and / or with the electric heating device, the first heating system may include a mechanical vapor recompression (MVR) system, comprising one or more mechanical steam compression stages, one or more first heat exchangers receiving steam produced by one or more of the mechanical compression stages, for example downstream of each stage, and connected to the gas supply line so as to transmit heat to it, a second heat exchanger receiving heat from a hot fluid and producing steam (low pressure or vacuum steam) supplying the mechanical compression stage(s).

[0050] The second electric heating system 20 is an electric heating system with thermal storage comprising herein:

[0051] - at least one thermal storage device 210 containing at least one medium of thermal storage, and

[0052] - at least one electric heating device 220 of the thermal storage medium.

[0053] In the embodiment shown [Fig. 1], the thermal storage medium is solid. The second electric heating system 20 then comprises a bypass circuit 200 of the combustion gas supply line 3, this bypass circuit 200 passing through at least one thermal storage device 210, here only one, containing a solid thermal storage medium. Furthermore, the heating device 220, typically an electric heating device, for example with a [missing word - likely "effect"], A Joule heater, or similar, is mounted on a bypass pipe 202 connected to the bypass circuit 200 and connected in parallel with the thermal storage device 210. Valves 204 and 206, mounted on the bypass circuit and the bypass pipe respectively, and a fan 208 ensure flow regulation and fluid circulation. The invention is not limited by the number and position of the valve(s) and / or fan(s). In particular, in an embodiment not shown, at least one electric heating device may be integrated with at least one thermal storage device. The bypass pipe 202 is then omitted.

[0054] In the embodiment shown, the combustion gas supply line 3 includes a third electric heating system 30, preferably an electric heating device, for example Joule effect or other, mounted in parallel with the second electric heating system 20. A valve 5 allows control of the gas flow circulating through the third electric heating system 30.

[0055] A management system 40 is configured to control the various heating systems 10, 20, 30. This management system 40 can in particular regulate the target temperature Te of the combustion gas circulating in the supply line 3 downstream of the heating systems 10, 20, 30 by regulating the electrical power supplied to each heating system and / or the flow rates circulating in the different lines.

[0056] The management system 40 can be configured, in particular, to: (a) in a charging phase in which the thermal storage medium of the second heating system 20 accumulates (stores) calories, operate the first heating system 10 to heat the gas to a first temperature T1, and (a1) operate the heating device 220 of the thermal storage medium to heat the latter, and / or (a2) use at least a fraction of the gas heated by the first heating system to heat the thermal storage medium, (b) in a discharge phase in which the thermal storage medium of the second heating system 20 releases calories, operate the first heating system 10 to heat the combustion gas to a second temperature T2, then circulate the entire combustion gas flow in the bypass circuit 200 through the thermal storage device 210 containing the thermal storage medium to heat the combustion gas from the second temperature T2 to a predetermined temperature Tp, or circulate a fraction of the gas flow at the second temperature T2 in the bypass circuit 200 through the thermal storage device containing the solid medium to heat this gas fraction to a third temperature T3, which, in mixing with the remaining fraction of gas flow, reaches the predetermined temperature Tp.

[0057] In particular, during the charging phase, in the example shown [Fig. 1], the control system 40 can be configured to circulate the combustion gas in the loop comprising the heating device 220 and the storage device 210. The valve 204 is then closed, the valve 206 is open, and the fan 208 ensures the circulation of the combustion gas through the heating device and then the storage device 210. The thermal storage medium in this device can then accumulate heat. The charging phase can advantageously be implemented for a sufficiently long period to reach a temperature in the thermal storage device preferably higher than the desired target temperature Te of the combustion gas, for example, a temperature of 300 to 1000 °C, for example, 560 to 700 °C.

[0058] This charging phase can advantageously be implemented while electricity is cheaper and / or comes from decarbonized sources (wind, solar, nuclear power plant, hydroelectric, ...), which makes it possible to decarbonize the electrical consumption of the installation and / or reduce operating costs.

[0059] During the charging phase, the first and third electric heating systems operate to heat the combustion gas to the desired target temperature Te, typically from 200 to 700 °C, preferably from 300 to 600 °C.

[0060] Alternatively or in combination, during the charging phase, the management system 40 can be configured to operate the first heating system 10 to heat the gas to the first temperature Tl and circulate a fraction of the gas through the circuit 200 comprising the storage device 210 to heat the thermal storage medium. In this case, depending on the configuration of the first heating device and the first temperature Tl to which it can heat the gas, the heating device 220 could be omitted (for example, when the first temperature Tl is higher than a desired storage temperature Ts).

[0061] During the discharge phase, valve 206 is closed and fan 208 is stopped. Valve 204 is open. Valve 5 can be fully closed and, optionally, the third electric heating system can be switched off. The combustion gas is then heated to the predetermined temperature Tp or target temperature Te desired by the first and second electric heating systems. Valve 5 might not be fully closed, and the electric heating system 30 could operate at a lower power than during the charging phase.

[0062] It is thus understood that, in this discharge phase, the total electrical power required to heat the combustion gas is reduced compared to the charging phase thanks to the calories supplied by the thermal storage device.

[0063] The invention is not limited to the embodiment shown. In particular, the third electric heating system 30 could be eliminated and, if the pump If the PACH heat pump does not have sufficient power to heat the combustion gas to the desired temperature, one or more electric heating devices can be added to the first electric heating system, mounted in series and / or in parallel downstream and / or upstream of the heat pump and upstream of the second electric heating system 20.

[0064] The solid thermal storage medium, generally in the form of powder, particles, or solid blocks having open cavities and / or channels, advantageously exhibits suitable thermal storage capacities and / or is capable of achieving heat transfer rates suitable for the intended use. This solid medium can, for example, be contained within an insulated enclosure. Suitable heat-transfer solids include volcanic rocks or refractory materials, such as alumina, etc. A thermal storage device containing volcanic rocks produced by Brenmiller Energy can thus be used. Stacked refractory materials can also be used; the storage device can, for example, be similar to a glass furnace regenerator and contain a stack of refractory materials, these refractory materials being able to be cruciform, brick, bushel, or pot shapes.Electrically conductive refractory bricks can also be used, which can be heated by the circulation of gas and / or by an electric current passing through the bricks during the charging of the thermal storage (for example, refractory bricks from Joule Hive Thermal Battery).

[0065] In a second embodiment, the thermal storage medium is a liquid. In this case, the second electric heating system may include a circuit in which the liquid medium circulates, the circuit comprising at least one thermal storage device and the heat exchanger.

[0066] A first example of implementing this embodiment is described with reference to [Fig. 2]. In this embodiment, the second electric heating system 22 comprises a circuit 221 including a single thermal storage device 211. In addition, the heating device 220 for the liquid medium is installed on a bypass line 223 mounted in parallel with the thermal storage device 211. Valves 224, 225 are provided for circulating the fluids in the circuit 221 and the bypass line 223. A heat exchanger 226 ensures the transfer of heat from the liquid medium to the combustion gas circulating in the line 3.

[0067] In the embodiment shown, the first electric heating system 10 comprises, connected in series, a heat pump PAC and an electric heating device Res_l. However, the invention is not limited to this embodiment, and one or more heat pumps (in series and / or in parallel) could be provided, followed by one, two, or three electric heating devices, or any other configuration. Another configuration for achieving the desired combustion gas temperature involves a combination of one or more heating devices connected in series and / or parallel. However, the use of a heat pump is preferred.

[0068] In this example, a third electric heating system 30, for example an electric heating device, is provided downstream of the second electric heating system 22. This third heating system could however be omitted.

[0069] During the charging phase, the management system 40 is then configured to accumulate calories in the storage device 211. For this purpose, valve 225 can be closed, and valve 224 opened so that the liquid medium flows from the heating device 220 to the storage device 211. The management system 40 also operates the first heating system 10 and optionally the third heating system 30 when present, to heat the combustion gas from the ambient temperature, for example 25 °C, to a target temperature Te, for example from 200 to 700 °C, preferably from 300 to 600 °C, for example from 500 to 550 °C.

[0070] During the discharge phase, the management system 40 is configured so that the storage device 211 releases the calories it has accumulated to the combustion gas circulating in the supply line 3. For this purpose, for example, the valve 224 is closed and the valve 225 is opened so that the liquid medium flows from the storage device 211 to the heat exchanger 226. The first electric heating system 10, and possibly the third electric heating system 30, can then be unloaded. For this purpose, the management system 40 can operate the first heating system to heat the combustion gas to a second temperature T2, for example lower than the first temperature T1 of the charging phase.In the example, it will be possible, for instance, to maintain the operation of the PACH or reduce the electrical power supplied to the PACH, and to stop the electric heating device Res_l, the missing calories being supplied by the second heating system 20, and optionally by the third heating system 30. .

[0071] The liquid medium can advantageously be chosen from ionic liquids, salts, for example potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), sodium nitrate (NaNO3), sodium nitrite (NaNO2), lithium nitrate, alone or in mixtures, for example a mixture of sodium nitrate and potassium nitrate or a eutectic mixture of sodium nitrate and potassium nitrate, salt-water systems in which the salts form hydrates, such as lithium bromide. Preferably, the liquid medium can be chosen from salts, such as potassium nitrate, calcium nitrate, sodium nitrate, sodium nitrite, lithium nitrate, alone or in mixtures. For example, a eutectic mixture containing 60% by mass of sodium nitrate and 40% by mass of potassium nitrate may be used. (KNO3), also called "Solar Sait", or a mixture containing 7% by mass of NaNO3, 53% by mass of KNO3 and 40% by mass of NaNO2, or a mixture containing 48% by mass of Ca(NO3)2, 45% of KNO3 and 7% of NaNO2.

[0072] The storage device 211 may further include a solid thermal storage medium, for example volcanic rock, refractory bricks, or other, or may not. The enclosure of the storage device receiving the liquid thermal storage medium, and optionally a solid thermal storage medium, may contain layers of thermal storage medium at different temperatures, the temperature of the layers increasing from bottom to top. When a solid thermal storage medium is present, it may be arranged in the lower part of the enclosure and form a bed. This type of storage device can reduce the amount of liquid thermal storage medium to be used. During charging, the liquid medium is drawn from the bottom of the enclosure and reinjected hot at the top of the enclosure. During discharging, the liquid medium exiting the top of the enclosure is sent directly to the heat exchanger.When a solid medium is present, it can be as previously described.

[0073] In the embodiment of [Fig. 3], the second electric heating system 22 comprises a first thermal storage device 211 and a second thermal storage device 212 mounted on the circuit 221. The thermal heating device 220 is disposed between the two thermal storage devices 211 and 212 on the opposite side from the heat exchanger 226, as shown. A valve 227 allows control of the circulation of the liquid medium.

[0074] Thus, during the charging phase, the management system 40 can be configured to circulate the liquid medium from one thermal storage device to another, generally from the coldest to the hottest, passing through the heating device 220, for example by closing the valve 227, thereby allowing the heat to be accumulated in the second storage device 212 and heated to the storage temperature Ts. During the discharging phase, the management system 40 can then be configured to circulate the liquid medium from the second storage device 212 at the storage temperature Ts to the heat exchanger 226 before returning it to the first storage device 211, for example by opening the valve 227. The first and third heating systems 10 and 30 can be controlled by the management system 40 as previously described with reference to [Fig. 2].

[0075] The embodiment shown in [Fig. 4] differs from that shown in [Fig. 3] by the position of the heating device 220 of the second electric heating device 24, which is installed not on the circuit 221 but on the combustion gas supply line 3. With such an arrangement, it is the combustion gas circulating in the supply line 3 that provides, via the heat exchanger 226 heats the liquid medium circulating between the two thermal storage devices 211, 212 in charging mode. Thus, the control system 40 can be configured to operate the heating device 220 only during the charging phase, with this heating device 220 being off in discharging mode. When the temperature of the gases exiting the heat exchanger is higher than the target temperature Te, it may be advantageous to provide a bypass line that draws a fraction of the gas flow upstream of the heating device 220 and reinjects it into the line 3 downstream of the heat exchanger 226. The first and third heating systems 10 and 30 can be controlled by the control system 40 as previously described with reference to [Fig. 2].

[0076] Alternatively, only one of the two storage devices 211, 212 could be provided. Alternatively or in combination, the heating device 220 and the heating device Res_l could form a single heating device.

[0077] In the embodiments shown in Figures 2 to 4, the presence of the third electric heating system 30 downstream of the heat exchanger 226 of the second electric heating system 22, 24 is particularly advantageous when the liquid medium circulating in or present in the heat exchanger 226 must be maintained at a minimum temperature to prevent it from solidifying during a charging phase. This third electric heating system 30 will then preferably be located as close as possible to the heat exchanger 226, downstream of it. Similarly, the heat exchanger 226 may preferably be located immediately downstream of a component of the first electric heating system 10, particularly in the embodiments of Figures 2 and 3, or immediately downstream of the heating device 220, in order to maintain the liquid medium circulating in or present in the heat exchanger 226 at a minimum temperature.

[0078] In the embodiments shown in Figures 3 and 4, the thermal storage devices and the liquid medium can be as described with reference to [Fig.2],

[0079] The circuit 221 and the bypass pipe 223 may be equipped with one or more valve(s) and / or pump(s) to ensure the circulation of the liquid medium during the charging and discharging phases of the second electric heating system 22 or 24

[0080] Regardless of the embodiment, the management system 40 can also receive various pieces of information from one or more appropriately arranged sensors relating to:

[0081] - to the power supply (electrical and / or thermal) of the heat pump (amount of current received and consumed, temperature and / or flow rate of fluids whose temperature is controlled),

[0082] - in the charging and discharging state of each thermal storage system (temperature of thermal storage devices),

[0083] - to the phase in which each thermal storage system is located (charge, dump),

[0084] - to the amount of electrical and / or thermal energy received / produced by each electric heating system (quantity of current, flow rate and / or temperature of fluids).

[0085] The management system 40 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 may form means of communication, optionally bidirectional, between the management system and the components of the electric heating systems used in the present invention.

[0086] The management system 40 may also include storage means, which may be random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), flash memory, external memory, or other. These storage means may, among other things, store received data, measured values, calculated values, and one or more computer programs.

[0087] The steam cracking furnace 110 according to the invention is typically installed in a steam cracking installation 100.

[0088] Thus, the effluent exiting the steam cracking furnace 110 is then rapidly cooled (quenched) in one or more cooling units, then purified and separated in compression and fractionation units. These different units of a steam cracking plant are well known to those skilled in the art and will be briefly described below.

[0089] Typically, at the outlet of the steam cracking furnace reactor(s) 110, the cracked gases are vented to a rapid cooling unit 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, for example from 820-850°C to 300-510°C. These cooled cracked gases can optionally be fed to a fractionation column (also called primary fractionation) to condense and separate the fuel oil fraction from the cracking gas.

[0090] The fractionated overhead gases are brought to a second cooling unit, generally a water-quench tower, which allows most of the dilution vapor and heavy fuels present in the gases to condense.

[0091] At the outlet of the second cooling unit, the cracked gases enter a compression unit typically comprising a series of compression stages, generally 3 to 6, each stage including a compressor, a cooling means (for example, a heat exchanger), and a liquid-gas separation device. The compressors of the various stages are generally powered by a steam turbine or an electric motor (or several of these). This compression unit further 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.

[0092] The gases exiting the compression unit enter the third cooling unit where they are cooled to cryogenic temperatures. The cooling is generally provided by cryogenic fluids such as liquid ethylene and propylene.

[0093] The third cooling unit thus comprises refrigeration cycles using 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 by passing through a compressor, then cooled in a heat exchanger, and then further cooled by expansion.The third cooling unit thus makes it possible to cool the cracked gases entering the fractionation unit and more particularly the cold fractionation section (often referred to as the cold box) of it (de-methanizer), 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.

[0094] The fractionation unit typically comprises a cold fractionation section operating at low temperature for separating hydrocarbons into C1 / C2, followed by a hot fractionation section operating at more high temperature and capable of separating C3 / C4 hydrocarbons. The fractionation unit may, for example, include a methanizer, a propane converter, and / or an ethane converter. The sequence of these units—methanizer, 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.

[0095] In this fractionation unit, 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. Example

[0096] Power calculations were performed for a combustion air supply line equipped with an electric heating system according to the invention, comprising a first electric heating system including a heat pump and two Joule-effect heating devices connected in series, a second system including two thermal storage devices as described with reference to [Fig. 3], and a third electric heating system including a Joule-effect heating device. The heat pump receives a hot fluid at 80 °C, and its first heat exchanger provides a thermal power of 11 MWth, while its second heat exchanger provides a thermal power of 7 MWth. The heat pump operates continuously under the same conditions to heat the combustion gas from 110 to 200 °C. In load mode, the temperature of the storage device of the second electric heating system reaches 560 °C.The storage system comprises 2500 m3 of Solar Sait, namely a eutectic mixture of 60% by mass of sodium nitrate and 40% by mass of potassium nitrate.

[0097] Table 1 shows the calculated power outputs of each element in nominal mode (second electric heating system off), in charging mode of the second electric heating system, and in discharging mode of the second electric heating system. In discharging mode, the second electric heating system provides the same thermal power output as a Joule-effect heating device, but without electrical consumption, so the overall electrical power consumption is lower.

[0098] [Table 1] Table 1 Nominal mode Load mode Discharge mode Air temperature at heat pump inlet 110 °C 110 °C 110 °C Air temperature at heat pump outlet 200 °C 200 °C 200 °C Electrical power supplied to the heat pump 4 MWe 4MWe 4MWe Thermal power supplied by the first Joule effect device of the first electric heating system 10 MWth 10 MWth 10 MWth Air temperature at the outlet of the first Joule effect device 280 °C 280 °C 280 °C Thermal power supplied by the second Joule effect device of the first electric heating system 22 MWth 22 MWth 0 Air temperature at the outlet of the second Joule effect device 464 °C 464 °C 280 °C Thermal power supplied by the second Electric heating system 0 0 22 MWth Air temperature at the outlet of the heat exchanger of the second electric heating system 464 °C 464 °C 464 °C Thermal power supplied by the Joule effect device of the third electric heating system8 MWth 8 MWth 8 MWth Air temperature at the outlet of the third electric heating system 534 °C 534 °C 534 °C

Claims

1. Demands Gas-fired electrical heating installation (1), in particular for a steam cracking furnace (110), characterized in that it comprises: - at least one gas supply line (3), and: - a first electric heating system (10), mounted on at least one gas supply line, - a second electric heating system with thermal storage (20, 22, 24) mounted on at least one gas supply line downstream of the first heating system (10) with respect to the gas flow, and comprising: - at least one thermal storage device (210, 211, 212) containing at least one thermal storage medium selected from a solid medium and a liquid medium, - optionally at least one heating device (220) of at least one thermal storage medium, and - according to a first configuration (i) a bypass circuit (200) of at least one gas supply line (3) passing through at least one thermal storage device (210) containing only at least one solid medium, -or according to a second configuration (ii) a heat exchanger (226) in which the liquid medium and the gas supplied by at least one supply line circulate, and a circuit (221) in which the liquid medium circulates, this circuit comprising at least one thermal storage device (211, 212) and the heat exchanger (226), The installation also includes a management system for the first and second electric heating systems, configured to: (a) in a charging phase in which at least one thermal storage medium of the second heating system (20) accumulates calories, operate the first heating system to heat the gas to a first temperature T1, and (a1) operate the heating device (220) to heat at least one thermal storage medium, and / or (a2) use at least a fraction of the gas heated by the first heating system to heat the thermal storage medium,

2. (b) in a discharge phase in which at least one thermal storage medium of the second heating system (20) releases heat, command the shutdown of the optional heating device, operate the first heating system (10) to heat the gas to a second temperature T2, and: in the first configuration (i) circulate the entire gas flow at the second temperature T2 in the bypass circuit (200) through the thermal storage device (210) containing the solid medium to heat the gas from the second temperature T2 to a predetermined temperature Tp, or circulate a fraction of the gas flow at the second temperature T2 in the bypass circuit through the thermal storage device containing the solid medium to heat this gas fraction to a third temperature T3, which, when mixed with the remaining fraction of the gas flow, reaches the predetermined temperature Tp, or in the second configuration (ii) circulate the liquid medium through at least one thermal storage device and then into the heat exchanger (226) to heat the gas from the second temperature T2 to the predetermined temperature Tp. Installation (1) according to claim 1, characterized in that the first electric heating system (10) comprises one or more of the following components mounted in series and / or in parallel on at least one gas supply line (3): - a heat pump (HP) connected on one side to the gas supply line (3) so as to transmit heat to it and on the other side to a line (4) in which a hot fluid circulates so as to receive heat from the latter, - a mechanical vapor recompression system, comprising at least one mechanical steam compression stage, at least one first heat exchanger receiving steam produced by at least one mechanical compression stage and connected to the gas supply line so as to transmit heat to it, a second heat exchanger receiving heat from a hot fluid and producing steam supplying at least one mechanical compression stage, - an electric heating device (Res_l).

3. Installation (1) according to claim 1 or 2, characterized in that, in the first configuration, the second electric heating system (20) comprises: - the bypass circuit (200) comprising at least one thermal storage device (210) containing only the solid medium and, - at least one heating device (220) for the solid medium, optionally mounted on a bypass line (202) connected to the bypass circuit in parallel with at least one thermal storage device (210).

4. Installation (1) according to claim 3, characterized in that it comprises a third electric heating system (30) mounted on at least one gas supply line (3) in parallel with the second electric heating system (20).

5. Installation (1) according to claim 1 or 2, characterized in that, in the second configuration of the second electric heating system (20), the circuit (221) comprises a single thermal storage device (211) and a liquid medium heating device (220), optionally mounted on a bypass line (223) mounted in parallel with the thermal storage device (211).

6. Installation (1) according to claim 1 or 2, characterized in that, in the second configuration of the second electric heating system (20), the circuit (221) comprises, mounted in series in a direction of circulation of the liquid medium, a first thermal storage device (211), a second thermal storage device (212) and the heat exchanger (226), at least one heating device (220) of the liquid medium being integrated into each thermal storage device or disposed between the first and second thermal storage devices.

7. Installation (1) according to claim 1 or 2, characterized in that, in the second configuration of the second electric heating system (20), the circuit (221) comprises, mounted in series in one direction of circulation of the liquid medium, a first thermal storage device (211), optionally a second thermal storage device (212), and the heat exchanger (220), and in that at least one heating device (220) of the liquid medium is mounted on at least one gas supply line (3), upstream of the heat exchanger (226) of the second heating system (20).

8. Installation (1) according to any one of claims 5 to 7, characterized in that it comprises a third electric heating system (30) mounted on at least one gas circulation line downstream of the heat exchanger (226) of the second electric heating system (20).

9. Steam cracking installation comprising a steam cracking furnace and an electrical gas heating installation (1) according to any one of the preceding claims, the steam cracking furnace comprising a radiation zone equipped with burners connected to at least one fuel gas supply line and to at least one oxidizing gas supply line (3) and the electrical gas heating installation (1) being mounted on at least one oxidizing gas supply line (3).

10. Hydrocarbon steam cracking process characterized in that it comprises: - a cracking step of a hydrocarbon feedstock carried out at a cracking temperature in a steam cracking plant according to claim 9, 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 the electric heating plant (1) and comprises: - supplying the first electric heating system (10) with oxidizing gas to be heated, and - in a charging phase in which the thermal storage medium of the second electric heating system (20) accumulates heat, operating the first heating system to heat the gas to a first temperature T1,and (a) operate the heating device (220) to heat the thermal storage medium and / or (a2) use at least a fraction of the gas heated by the first heating system to heat the thermal storage medium, - in a discharge phase in which the thermal storage medium of the second heating system releases heat, command the shutdown of the optional heating device, do, operate the first heating system (10) to heat the combustion gas to a second temperature T2, and in the first configuration (i) circulate the entire combustion gas flow in the bypass circuit (200) through the thermal storage device (210) containing the solid medium and heat the gas from the second temperature T2 to a predetermined temperature Tp, or circulate a fraction of the gas flow at the second temperature T2 in the bypass circuit through the thermal storage device containing the solid medium to heat this gas fraction to a third temperature T3, which, when mixed with the remaining fraction of the gas flow, reaches the predetermined temperature Tp, or in the second configuration (ii) circulate the liquid medium through at least one thermal storage device and then into the heat exchanger (226) to heat the combustion gas from the second temperature T2 to the predetermined temperature Tp.

Images