System for generating electrical energy in a chlor-alkali industry process

Abstract

System (100) for exploiting hydrogen (H2) produced as by-product by a chlor-alkali plant (10) comprising a compressor (20), a storage unit (30) and a power generation unit (40). The compressor (20) is fluidly coupled to the chlor-alkali plant (10) and is configured to receive and compress the hydrogen (H2) produced by the chlor-alkali plant (10) so to discharge a compressed hydrogen flow (CH2). The storage unit (30) is fluidly coupled to the compressor (20) and is configured to receive and store the compressed hydrogen flow (CH2) at least for a predetermined time and to discharge a stored hydrogen flow (SH2). The power generation unit (40) is fluidly coupled to the storage unit (30) and is configured to receive a first hydrogen flow (HF1) of the stored hydrogen (SH2) as a fuel and / or one or more external fuels (F), so to perform a combustion and produce electrical power (E1) and / or mechanical power (M1). The power generation unit (40) is further electrically coupled to the chlor-alkali plant (10) and / or mechanically coupled to the compressor (20) so that the electrical power (E1) produced by the power generation unit (40) is supplied to the chlor-alkali plant (10) and / or at least part of the mechanical power (M1) is used to drive the compressor (20).

Description

TITLESystem for generating electrical energy in a chlor-alkali industry processDESCRIPTIONTECHNICAL FIELD

[0001] The subject-matter disclosed herein relates to an innovative system and relative method for exploiting the hydrogen produced in a chlor-alkali plant and producing electrical energy and / or mechanical energy and possibly a compressed hydrogen flow to be advantageously delivered to off-takers, avoiding any release of hydrogen to atmosphere.BACKGROUND ART

[0002] Among different chemical sectors, one of the most energy-intensive is the chlor-alkali industry. The chlor-alkali industry process requires around 2500-3500 kWh per ton of chlorine, which involves an important environmental impact.

[0003] In fact, the chlor-alkali industry produces chlorine, sodium / potassium hydroxide (caustic) and hydrogen through electrolysis of common salt in a brine solution. During electrolysis, two electrodes are immersed in the brine solution. When a source of direct current is attached to the electrodes, typically provided by the electrical grid, sodium ions begin to move toward the negative electrode (cathode) and chlorine ions toward the positive electrode (anode), so that chlorine gas is produced.

[0004] For every mole of chlorine produced, one mole of hydrogen is produced. Typically, the hydrogen produced is released to atmosphere.

[0005] Therefore, it would be desirable to have a chlor-alkali plant with less or no electricity supply from the grid exploiting the hydrogen produced as by¬ product from the process (which could be termed as “ORANGE HYDROGEN”) and advantageously reducing or eliminating CO2 emissions caused by the chlor-alkali industry process.SUMMARY

[0006] According to an aspect, the subject-matter disclosed herein relates to a system for exploiting hydrogen produced as by-product by a chlor-alkali plant, the system comprising:a compressor fluidly coupled to the chlor-alkali plant and configured to receive and compress the hydrogen produced by the chlor-alkali plant so to discharge a compressed hydrogen flow,a storage unit fluidly coupled to the chlor-alkali plant and configured to receive and store the hydrogen produced by the chlor-alkali plant at least for a predetermined time and to discharge a stored hydrogen flow, anda power generation unit fluidly coupled to the storage unit and configured to receive a first hydrogen flow of the stored hydrogen flow from as a fuel and / or one or more external fuels, so to perform a combustion and produce electrical power and / or mechanical power.The power generation unit is further electrically coupled to the chlor-alkali plant and / or mechanically coupled to the compressor so that the electrical power produced by the power generation unit is supplied to the chlor-alkali plant and / or at least part of the mechanical power is used to drive the compressor.

[0007] According to another aspect, the subject-matter disclosed herein relates to a method for exploiting hydrogen produced as by-product by a chlor-alkali plant, the method comprising the steps ofA. Receiving and compressing the hydrogen produced by the chlor-alkali plant through a compressor;B. Storing in a storage unit at least for a predetermined time the hydrogen compressed at step A and to discharge a stored hydrogen flow;C. Supplying a first hydrogen flow of the stored hydrogen flow and / or one or more external fuels to a power generation unit as a fuel so to perform a combustion and produce electrical power and / or mechanical power, the electrical power being supplied to the chlor-alkali plant and / or at least part of the mechanical power being used to drive the compressor.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. 1 shows a schematic diagram of an embodiment of an innovative system for exploiting the hydrogen produced in a chlor-alkali plant according to the present disclosure, andFig. 2 shows a simplified flow chart of an embodiment of an innovative method for producing electrical energy using hydrogen produced by a chlor¬ alkali plant.DETAILED DESCRIPTION OF EMBODIMENTS

[0009] According to an aspect, the subject-matter disclosed herein relates to a system for exploit hydrogen produced as by-product by a chlor-alkali plant. Typically, a chlor-alkali plant produces chlorine and sodium / potassium hydroxide (caustic) and, for every mole of chlorine produced, one mole ofhydrogen is produced as by-product. The system disclosed herein allows a dynamic use of the hydrogen produced from the chlor-alkali plant by compressing and storing the hydrogen and then supply part or all of the stored hydrogen flow discharged by the hydrogen storage to a gas turbine or a gas engine (i.e. a power generation unit) to be used as a fuel so to produce electrical or mechanical energy. Advantageously, the remaining stored hydrogen flow discharged by the hydrogen storage (if any) may be supplied to a compressor unit so to compress it and deliver it to off-takers. According to the present solution, if it is advantageous (e.g. from an economical point of view) to supply all the stored hydrogen flow discharged by the hydrogen storage to the compressor unit, the amount of the stored hydrogen flow supplied to the power generation unit could be null and one or more external fuels are supplied to the power generation unit. The utilization of the stored hydrogen flow discharged by the hydrogen storage and its splitting between the gas turbine (or gas engine) and the compressor may be performed for example according to hydrogen demand and / or grid electricity local price and / or hydrogen local price and / or time of the day.

[0010] In the innovative system disclosed herein, the hydrogen produced by the chlor-alkali plant is exploited so to efficiently reduce the costs of chlorine / NaOH production (e.g. due to low-cost power generation from the gas turbine) instead of releasing hydrogen to atmosphere. Moreover, the innovative system disclosed herein allows to reduce the dependency of the plant on the electrical grid, therefore advantageously reducing the CO2 emissions related to the chlorine / NaOH production (possibly achieving decarbonization of the chlor-alkali system).

[0011] According to another aspect, the subject-matter disclosed herein relates to a method for exploit hydrogen produced as by-product by a chlor¬ alkali plant which basically consists of receive and compress the hydrogen produced by the chlor-alkali plant, to store the compressed hydrogen and tosupply the stored hydrogen flow discharged by the hydrogen storage as a fuel and / or one or more external fuels to a gas turbine or a gas engine so to produce electrical or mechanical energy. Advantageously, the remaining stored hydrogen flow discharged by the hydrogen storage (if any) is suppled to a compressor so to compress it and deliver it to off-takers.

[0012] Reference now will be made in detail to embodiments of the disclosure, examples of which are illustrated in the drawings. The examples and drawing figures are provided by way of explanation of the disclosure and should not be construed as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. In the following description, similar reference numerals are used for the illustration of figures of the embodiments to indicate elements performing the same or similar functions. Moreover, for clarity of illustration, some references may be not repeated in all the figures.

[0013] Fig 1 shows, for example and without limitations, a schematic diagram of a first embodiment of an innovative system 100 (referred in the following as “system 100”) for exploiting hydrogen H2 produced as by-product by a chlor-alkali plant 10 according to the present disclosure.

[0014] The system comprises a compressor 20 arranged downstream of the chlor-alkali plant 10 and fluidly coupled to the chlor-alkali plant 10. The compressor 20 is configured to receive and compress the hydrogen H2 produced by the chlor-alkali plant 10 so to discharge a compressed hydrogen flow CH2.

[0015] The system further comprises a storage unit 30 fluidly coupled to the compressor 20 and configured to store the compressed hydrogen flow CH2discharged by the compressor 20 at least for a predetermined time. For example, the storage unit 30 may be a hydrogen piping system, a tank or asuitable underground cavern. The storage unit 30 is further configured to discharge a stored hydrogen flow SH2.

[0016] The system 100 further comprises a power generation unit 40 fluidly coupled to the storage unit 30 and configured to receive a first hydrogen flow HF1 of the stored hydrogen SH2 from the storage unit 30 as a fuel and / or one or more external fuels F (for example hydrogen from an external source, natural gas, industrial / refinery off-gas...) so to perform a combustion. For example, the power generation unit 40 may be a gas turbine or a gas engine operating in simple cycle or combined cycle or co-generation mode.

[0017] The power generation unit 40 is configured to use the first hydrogen flow HF1 and / or one or more external fuels F as a fuel, so to produce electrical power El and / or mechanical power Ml (in particular, if the power generation unit 40 is a gas turbine, electrical power is produced and if the power generation unit 40 is a gas engine, mechanical power is produced). The power generation unit 40 is electrically coupled to the chlor-alkali plant 10 so that the electrical power El produced by the power generation unit 40 is supplied to the chlor-alkali plant 10. Alternatively or additionally, the power generation unit 40 is mechanically coupled to the compressor 20 so that at least part of the mechanical power Ml produced by the power generation unit 40 is used to drive the compressor 20.

[0018] Advantageously, the system 100 may further comprise a compression unit 50 fluidly coupled to the storage unit 30 and configured to receive a second hydrogen flow HF2 of the stored hydrogen SH2 and to compress it so to discharge a compressed second hydrogen flow CHF2. Advantageously, the compressed second hydrogen flow is supplied to hydrogen off-takers, in particular based on hydrogen demand and / or hydrogen local price and / or time of day.

[0019] Advantageously, the system 100 may further comprise a mixing unit45 arranged upstream of the power generation unit 40 and fluidly coupled to the storage unit 30. In particular, the mixing unit 45 is configured to receive the first hydrogen flow HF1 from the storage unit and the one or more external fuels F so to blend them before being supplied to the power generation unit 40.

[0020] It is known that a gas turbine or a gas engine produces exhaust gas flow as a result of combustion and expansion of the working fluid. Typically, exhaust gases are wet and with heat content which may be advantageously exploited. The power generation unit 40 is therefore further configured to discharge a wet exhaust gas flow WEG, in particular at an outlet of the power generation unit 40.

[0021] Advantageously, the system 100 further comprises a condenser 60 fluidly coupled to the power generation unit 40 and configured to condense the wet exhaust gas flow WEG discharged by the power generation unit 40 so to produce a heat flow HT and a water flow W and to discharge a dry exhaust gas flow DEG. In particular, the heat flow is carried by a heat transfer fluid which flows through the condenser 60, removes heat from the wet exhaust gas flow WEG (i.e. condensing the wet exhaust gas flow) and conveys it out of the condenser 60.

[0022] Advantageously, the system 100 further comprises a heat exchanger 70 thermally coupled to the condenser 60. In particular, the heat exchanger 70 is configured to receive an inlet water flow IW and the heat flow HT produced by the condenser 60, so to transfer heat to the inlet water flow IW and produce a steam flow S.

[0023] Advantageously, at least part of the steam flow is supplied to the chlor¬ alkali plant 10 (steam is typically needed in the chlor-alkali production e.g. for salt preparation and concentration of the caustic soda).

[0024] Advantageously, the system 100 further comprises a steam turbine 90fluidly coupled to the heat exchanger 70. In particular, the steam turbine 90 is configured to receive at least part of the steam flow S produced by the heat exchanger 70 and to expand it so to produce electrical power E2 and / or mechanical power M2.

[0025] In other words, the steam flow S produced by the heat exchanger 70 may be supplied to the chlor-alkali plant 10 or to the steam turbine 90 or partially to the chlor-alkali plant 10 and partially to the steam turbine 90.

[0026] According to a possibility, the steam turbine 90 may be electrically and / or mechanically coupled to the compressor 20 so that electrical power E2 may be used to drive the compressor 20 through an electric motor and / or mechanical power M2 may be used to drive the compressor 20. According to another possibility, the steam turbine 90 may be electrically coupled to the electrical grid so that the electrical power E2 is supplied to the electrical grid. According to still another possibility, the steam turbine 90 may be electrically coupled to the chlor-alkali plant 10 so that the electrical power E2 is supplied to the chlor-alkali plant 10.

[0027] Advantageously, the steam turbine 90 may be electrically and / or mechanically coupled to the compression unit 50 so that electrical power E2 may be used to drive compression unit 50 through an electric motor and / or mechanical power M2 may be used to drive compression unit 50. It is to be noted that the above-described possibilities may be combined with each other.

[0028] Advantageously, the system 100 further comprises a water purifier 80 fluidly coupled to the condenser 60. In particular, the water purifier 80 is configured to receive the water flow produced by the condenser 60 and to purify it so to discharge a purified water flow PW. Advantageously, the purified water flow PW is supplied to the chlor-alkali plant 10.

[0029] Advantageously, the system 100 further comprises a control systemunit 35 fluidly and electrically coupled to the storage unit 30. It is to be noted that the control system unit 35 may be arranged downstream or upstream of the storage unit 30, preferably downstream. In particular, the control system unit 35 is configured to regulate the amount of flow of the first hydrogen flow HF1 to be supplied to the power generation unit 40 and / or of the second hydrogen flow HF2 to be supplied to the compression unit 50. More in particular, the control system unit 35 is configured to regulate one or more control valves (e.g. 2-way valves or ball valves or butterfly valves) so to regulate the amount of flow of the first hydrogen flow HF 1 and / or of the second hydrogen flow HF2.

[0030] Advantageously, the control system unit 35 is further configured to receive hydrogen demand / supply data and to regulate the amount of flow of the first hydrogen flow HF1 and / or of the second hydrogen flow HF2 based on said hydrogen demand / supply data. It is to be noted that the hydrogen demand / supply data may be received from the hydrogen market or may be user-defined.

[0031] Even more advantageously, the system 100 further comprises a flow measuring device 36 arranged upstream of the control system unit 35 and electrically coupled to the control system unit 35. In particular, the flow measuring device 36 is further fluidly coupled to the storage unit 30 and is configured to measure the amount of stored hydrogen flow SH2 discharged by the storage unit 30 and to provide the measuring data to the control system unit 35.

[0032] Advantageously, the control system unit 35 is further configured to regulate the amount of flow of the first hydrogen flow HF 1 and / or of the second hydrogen flow HF2 based on said measuring data.

[0033] According to another aspect, the subj ect-matter disclosed herein refers to a method 200 for exploiting hydrogen H2 produced as by-product by a chlor-alkali plant 10.

[0034] The method 200 comprises a step A of receiving and compressing 210 the hydrogen H2 produced by the chlor-alkali plant 10 through a compressor 20.

[0035] The method 200 further comprises a step B of storing 220 in a storage unit 30 at least for a predetermined time the hydrogen H2 compressed at step A and to discharge a stored hydrogen flow SH2.

[0036] The method 200 further comprises a step C supplying 240 a first hydrogen flow HF1 of the stored hydrogen flow SH2 and / or one or more external fuels F to a power generation unit 40 as a fuel so to perform a combustion and produce electrical power El which is supplied to the chlor¬ alkali plant 10 and / or mechanical power Ml is used to drive the compressor 20. Typically, the power generation unit 40, which may be for example a gas turbine or a gas engine, produces exhaust gas flow as a result of combustion and expansion of the working fluid, in particular a wet exhaust gas flow WEG.

[0037] Advantageously, the method 200 further comprises a step D of supplying 250 a second hydrogen flow HF2 of the stored hydrogen flow SH2 to a compression unit 50 so to compress it and discharge a compressed second hydrogen flow CHF2. Advantageously, the compressed second hydrogen flow CHF2 is supplied to to hydrogen off-takers.

[0038] In other words, the stored hydrogen flow SH2 discharged by the storage unit 30 may be divided and supplied to the power generation unit 40 and / or to the compression unit 50. For example, the first hydrogen flow HF1 is in a range of 15-100% of the stored hydrogen flow SH2 and the second hydrogen flow HF2 is in a range of 0-85% of the stored hydrogen flow SH2 (of course, the sum of the first hydrogen flow HF1 and the second hydrogen flow HF2 is the 100% of the stored hydrogen flow SH2 discharged by thestorage unit 30).

[0039] According but not limited to a possibility, during daytime, when grid electricity price is typically low and hydrogen price is typically high, the first hydrogen flow HF1 may be 100% of the stored hydrogen flow SH2 and the second hydrogen flow HF2 may be 0% of the stored hydrogen flow SH2 (it is to ben noted that in this case the power generation unit uses the one or more external fuels F to operate). According but not limited to another possibility, during nighttime, when grid electricity price is typically high, the first hydrogen flow HF1 may be 15% of the stored hydrogen flow SH2 and the second hydrogen flow HF2 may be 85% of the stored hydrogen flow SH2. Advantageously, in order to run the power generation unit 40 with high efficiency, the first hydrogen flow HF1 may be mixed with additional fuel F before being supplied to the power generation unit 40.

[0040] Advantageously, the method 200 further comprises a step Bl of receiving 230 hydrogen demand / supply data and / or measuring the amount of stored hydrogen flow SH2 discharged by the storage unit 30 and providing said demand / supply and / or measuring data to a control system unit 35 so to regulate the amount of flow of the first hydrogen flow HF1 and / or of the second hydrogen flow HF2 based on said data.

[0041] Advantageously, the method 200 further comprises the following steps:E. Condensing 260 wet exhaust gas flow WEG produced by the power generation unit 40 so to so to produce a heat flow HT and a water flow W;F. Purifying 270 the water flow W produced at step E and supplying the purified water flow PW to the chlor-alkali plant 10;G. Supplying 280 the heat flow HT produced at step E to an inlet water flow IW so to produce a steam flow S and supplying at least part of the steam flow S to the chlor-alkali plant 10.

[0042] Advantageously, the method 200 further comprises a step H of supplying 290 at least part of the steam flow S to the chlor-alkali plant 10 and / or to a steam turbine 90 configured to expand the steam flow S so to produce electrical power E2 and / or mechanical power M2 used to drive the compressor 20 and / or the compression unit 50.

Claims

CLAIMS1. System (100) for exploiting hydrogen (H2) produced as by-product by a chlor-alkali plant (10), the system comprising:a compressor (20) fluidly coupled to the chlor-alkali plant (10) and configured to receive and compress the hydrogen (H2) produced by the chlor-alkali plant (10) so to discharge a compressed hydrogen flow (CH2),a storage unit (30) fluidly coupled to the compressor (20) and configured to receive and store the compressed hydrogen flow (CH2) at least for a predetermined time and to discharge a stored hydrogen flow (SH2), anda power generation unit (40) fluidly coupled to the storage unit (30) and configured to receive a first hydrogen flow (HF1) of the stored hydrogen (SH2) as a fuel and / or one or more external fuels (F), so to perform a combustion and produce electrical power (El) and / or mechanical power (Ml),wherein the power generation unit (40) is further electrically coupled to the chlor-alkali plant (10) and / or mechanically coupled to the compressor (20) so that the electrical power (El) produced by the power generation unit (40) is supplied to the chlor-alkali plant (10) and / or at least part of the mechanical power (Ml) is used to drive the compressor (20).

2. System (100) of claim 1, further comprising a compression unit (50) fluidly coupled to the storage unit (30) and configured to receive a second hydrogen flow (HF2) of the stored hydrogen (SH2) from the storage unit (30) and to compress it so to discharge a compressed second hydrogen flow (CHF2).

3. System (100) of claim 1 or 2, further comprising a control system unit (35) fluidly and electrically coupled to the storage unit (30),the control system unit (35) being configured to regulate the amount of flow of the first hydrogen flow (HF1) and / or of the second hydrogen flow (HF2).

4. System (100) of claim 3, wherein the control system unit (35) is further configured to receive hydrogen demand / supply data and to regulate the amount of flow of the first hydrogen flow (HF1) and / or of the second hydrogen flow (HF2) based on said hydrogen demand / supply data.

5. System (100) of claim 3, further comprising a flow measuring device (36) arranged upstream of the control system unit (35) and being electrically coupled to the control system unit (35) and fluidly coupled to the storage unit (30),wherein the flow measuring device (36) is configured to measure the amount of stored hydrogen flow (SH2) discharged by the storage unit (30) and to provide said measuring data to the control system unit (35).

6. System (100) of claim 5, wherein the control system unit (35) is further configured to regulate the amount of flow of the first hydrogen flow (HF1) and / or of the second hydrogen flow (HF2) based on said measuring data.

7. System (100) of claim 2, wherein at least part of the mechanical power (Ml) produced by the power generation unit (40) is used to drive the compression unit (50).

8. System (100) of claim 1, further comprising a mixing unit (45) arranged upstream of the power generation unit (40) and fluidly coupled to the storage unit (30) and to the power generation unit (40), the mixing unit (45) being configured to receive the first hydrogen flow (HF1) from the storage unit (30) and / or the one or more external fuels (F) so to blend them before being supplied to the power generation unit (40).

9. System (100) of claim 1, further comprising a condenser (60) fluidly coupled to the power generation unit (40),wherein the power generation unit (40) is further configured to discharge a wet exhaust gas flow (WEG),wherein the condenser (60) is configured to condense the wet exhaust gas flow (WEG) discharged by the power generation unit (40) so to produce a heat flow (HT) and a water flow (W) and to discharge a dry exhaust gas flow (DEG).

10. System (100) of claim 9, further comprising a heat exchanger (70) thermally coupled to the condenser (60), wherein the heat exchanger (70) is configured to receive an inlet water flow (IW) and the heat flow (EIT) produced by the condenser (60) so to transfer heat to the inlet water flow (IW) and produce a steam flow (S).

11. System (100) of claim 10, wherein at least part of the steam flow (S) is supplied to the chlor-alkali plant (10).

12. System (100) of claim 10, further comprising a steam turbine (90) fluidly coupled to the heat exchanger (70),wherein the steam turbine (90) is configured to receive at least part of the steam flow (S) produced by the heat exchanger (70) and to expand it so to produce electrical power (E2) and / or mechanical power (M2).

13. System (100) of claim 12, wherein the steam turbine (90) is further mechanically coupled to the compressor (20) and / or to the compression unit (50) so that the mechanical power (M2) is used to drive the compressor (20) and / or the compression unit (50).

14. System (100) of claim 9, further comprising a water purifier (80) fluidly coupled to the condenser (60), wherein the water purifier (80) is configured to receive the water flow (W) produced by the condenser (60) and to purify it so to discharge a purified water flow (PW).

15. System (100) of claim 14, wherein the purified water flow (PW) is supplied to the chlor-alkali plant (10).

16. Method (200) for exploiting hydrogen (EI2) produced as by-product by a chlor-alkali plant (10), the method comprising the steps ofA. Receiving and compressing (210) the hydrogen (H2) produced by the chlor-alkali plant (10) through a compressor (20);B. Storing (220) in a storage unit (30) at least for a predetermined time the hydrogen (H2) compressed at step A and to discharge a stored hydrogen flow (SH2);C. Supplying (240) a first hydrogen flow (HF1) of the stored hydrogen flow (SH2) and / or one or more external fuels (F) to a power generation unit (40) as a fuel so to perform a combustion and produce electrical power (El) and / or mechanical power (Ml); wherein the electrical power (El) is supplied to the chlor-alkali plant (10) and / or at least part of the mechanical power (Ml) is used to drive the compressor (20).

17. The method (200) of claim 16, further comprising the step of:D. Supplying (250) a second hydrogen flow (HF2) of the stored hydrogen flow (SH2) to a compression unit (50) so to compress it and discharge a compressed second hydrogen flow (CHF2).

18. The method (200) of claim 17, wherein the compressed second hydrogen flow (CHF2) is supplied to hydrogen off-takers.

19. The method (200) of claim 17, comprising further the step of:Bl. Receiving (230) hydrogen demand / supply data and / or measuring the amount of stored hydrogen flow (SH2) discharged by the storage unit (30) and providing said demand / supply and / or measuring data to a control system unit (35) so to regulate the amount of flow of the first hydrogen flow (HF1) and / or of the second hydrogen flow (HF2) based on said data.

20. The method (200) of claim 16, further comprising the steps of:E. Condensing (260) wet exhaust gas flow (WEG) produced by the power generation unit (40) so to produce a heat flow (HT) and a water flow (W);F. Purifying (270) the water flow (W) produced at step E and supplying the purified water flow (PW) to the chlor-alkali plant (10);G. Supplying (280) the heat flow (HT) produced at step E to an inlet water flow (IW) so to produce a steam flow (S).

21. The method (200) of claim 17 and 20, further comprising the step of:H. Supplying (290) at least part of the steam flow (S) to the chlor¬ alkali plant (10) and / or to a steam turbine (90) configured to expand the steam flow (S) so to produce electrical power (E2) and / or mechanical power (M2) used to drive the compressor (20) and / or the compression unit (50).

Images