Methanol production plant and method

Abstract

Methanol production plant comprising: a supply line for a hydrocarbon fuel; a power plant (4), said power plant having combustion chamber (21), boiler chamber (22) with heat exchanger (23) arranged th

Description

The present disclosure relates to a methanol production plant and methods for using and operating a methanol production plant. BACKGROUND Methanol is used for a variety of purposes in industry and power production, and demand for methanol is expected to increase in the future due to among other things a drive to more sustainable fuel chains in the transport sector. Production of methanol is conventionally done via catalytic hydrogenation of CO and CO2. Such processes are energy demanding, and produce byproducts (such as carbonaceous components and / or water containing contaminants) which must be handled in order not to pose environmental hazards. This increases the cost and complexity of methanol production. Publications which may be useful to understand the field of technology include WO 2015 / 173184 A1; DE 10 2012 214 907 B4; DE 10 2009 007 567 A1; and US 2016 / 0153316 A1. There is a need for improved systems and methods for methanol production, in order to address the abovementioned or other challenges. The present disclosure has the objective to provide such improvements, or at least useful alternatives to the state of the art. SUMMARY In an example, there is provided a methanol production plant comprising: a supply line for a hydrocarbon fuel, a power plant having a combustion chamber, a boiler chamber with a heat exchanger arranged therein, and a gas condenser unit, a methanol reactor operatively arranged to synthesise methanol from carbon dioxide and hydrogen, and an electrolyser, wherein the combustion chamber, boiler chamber and exhaust gas condenser unit are fluidly interconnected in a working media flowpath extending between the supply line and the methanol reactor, the electrolyser is operatively arranged to provide oxygen to the combustion chamber and hydrogen to the methanol reactor, and wherein the working media flowpath has no mechanical fluid expander therein. In an example, there is provided a method for producing methanol. The detailed description below and appended claims outline further inventive examples and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS The above and other characteristics will become clear from the following description of illustrative, non-restrictive examples, with reference to the attached drawings, in which: Fig. 1 is a schematic view of a methanol production plant according to an example. Fig. 2 illustrates a power plant for use in a methanol production plant. Fig. 3 is a schematic view of a methanol production plant according to an example. Fig. 4 illustrates a power plant having flue gas recirculation for use in a methanol production plant. DETAILED DESCRIPTION Fig. 1 shows a schematic illustration of a methanol production plant 100 according to an example. The plant 100 comprises a supply line 1 for a hydrocarbon fuel, for example methane (CH4) or a gas mixture comprising methane. The fuel may alternatively be other hydrocarbons in gaseous, liquid and / or solid form, and / or mixtures thereof. In some examples, a gas comprising hydrocarbon gas(es) and a significant CO2 fraction be used, for example sourced from biogas production or gasifiers. (In the figures, the hydrocarbon fuel is indicated as CxHy and optional other content, such as a CO2 fraction, indicated as X.) A pump 2 (which may be a gas compressor if the hydrocarbon fuel is gaseous) can be provided to increase the pressure of the fuel stream provided by the supply line 1 and provide a pressurised fuel stream to a power plant 4 via power plant inlet line 3. The power plant 4 is described in further detail below and in relation to Fig. 2. The pump 2 may not be required if the fuel stream is already at the appropriate pressure. The power plant 4 produces a flue gas stream via a flue gas line 5. The flue gas stream is rich in CO2, e.g. having more than 50%vol CO2, more than 80%vol CO2, more than 90%vol CO2, or it consists substantially of pure CO2. The flue gas stream is provided to a methanol reactor 6, for example a catalytic reactor. The methanol reactor 6 also receives a H2 stream via a hydrogen line 7. The hydrogen line 7 is connected to an electrolyser 8 configured for production of H2 via electrolysis. A compressor 9 can be provided in the hydrogen line 7 in order to bring the produced H2 to a pressure required by the methanol reactor 6 (discussed in further detail below). Optionally, the electrolyser 8 may operate at a pressure which provides produced H2 to the hydrogen line 7 at a pressure which does not require additional pressurisation. The electrolyser 8 operates with electric power, the supply of which is indicated as Pi. A supply of water (H2O) for the electrolysis is provided via an external water supply line 10 (i.e., from an external source), via a water supply line 11 from the power plant 4, and / or from a water supply line 12 from a distillation unit 13 (described in further detail below). The electrolyser 8 further produces oxygen (O2), which is supplied to the power plant 4 via oxygen supply line 14. The skilled reader will recognise this as a conventional operation of an electrolyser, using electric power to produce hydrogen (H2) and oxygen (O2) from water (H2O). The water from different sources may have different quality and may be collected in a single stream and treated to meet the water quality requirement of electrolysis cell. Now referring to Fig. 2, the power plant 4 comprises a combustion chamber 21 fluidly connected to the plant inlet line 3. The combustion chamber 21 receives the hydrocarbon fuel stream from the plant inlet line 3 and is also fluidly connected to the oxygen supply line 14 to receive oxygen (O2). The combustion chamber 21 can operate with an oxyfuel combustion process, i.e. combustion of the hydrocarbon stream using pure or substantially pure oxygen, and without supply of air. The combustion products from the combustion chamber 21 are led to a boiler chamber 22, in which a heat exchanger 23 is arranged. The boiler chamber 22 may be a separate component (e.g., a housing which is separate from a housing defining the combustion chamber 21) arranged fluidly connected and downstream the combustion chamber 21, or may optionally be integral with the combustion chamber 21 such that the heat exchanger 23 is arranged in the combustion chamber 21 housing but downstream a hydrocarbon-oxygen reaction zone. An exhaust gas condenser unit 24 is arranged downstream the heat exchanger 23. The condenser unit 24 may optionally further cool the combustion products from the combustion chamber 21 such that water is condensed out. The condensed water is led to water supply line 11, and fed to the electrolyser 8 (see Fig. 1) for use in the production of hydrogen (H2) and oxygen (O2). Similarly as for the boiler chamber 22, the condenser unit 24 can be arranged integral with the combustion chamber 21 and / or the boiler chamber 22, e.g. in a common or integral housing, or it can be arranged in a separate housing fluidly connected to the other parts. The remaining exhaust gas (after water has been condensed out) is led from the condenser unit 24 to the flue gas line 5. As described above, this stream is rich in CO2. A closed-cycle heat engine 20, which may be a steam (Rankine) cycle engine, is in this example provided and operatively connected to the heat exchanger 23. The heat engine 20 further comprises a pump 25, a cooler 26 having a cooler heat exchanger 27 arranged therein, and a power turbine 28 arranged to receive heated working fluid from the heat exchanger 23 and operatively connected to a generator 29 via a shaft 30. The generator 30 produces an electric power output P2. The power output P2 can, for example, be supplied to a grid, and / or it can be supplied as input power Pi to the electrolyser 8 (for example directly or via a grid). The power plant 4 can, for example, be arranged similarly as that described in abovementioned WO 2015 / 173184 A1. Alternatively, the heat (or a part thereof, in addition to operating a heat engine 20) extracted via the heat exchanger 23 can be used for process purposes, such as a heat source for reforming processes. As such, the power plant 4 may be a power plant configured for producing industrial heat. The combustion chamber 21, boiler chamber 22 and condenser unit 24 define a permanently open fluid connection between the inlet line 3 and the flue gas line 5. There are no mechanical expanders (e.g., turbines or the like) between the inlet line 3 and flue gas line 5, such that the fluid pressure is substantially maintained (save for flow losses, which in comparison to a mechanical expander are moderate or low) between the inlet line 3 and the flue gas line 5. In this manner, the delivery pressure for the flue gas stream in flue gas line 5 will be substantially the same as or only slightly lower than the pressure at the inlet line 3. With reference to Fig. 1 again, the pump 2 may be omitted if the pressure of the fuel stream provided at the supply line 1 is sufficiently high. If, for example, the supply line 1 is fluidly connected to a producing well, or to a fuel supply system having a sufficiently high pressure, the pump 2 may not be required to provide a desired fluid stream inlet pressure for the plant 100. If the pressure at the supply line 1 is higher than the required or desired pressure for the power plant 4, the pressure can be reduced (e.g., via throttling or expansion) before the hydrocarbon fuel is supplied to the power plant 4. Cooling in the condenser unit 24 and in the cooler 26 can be done by exchange with e.g. external air or water, such as seawater if the plant 100 is arranged at a shoreside or offshore. The condenser unit 24 may have an internal heat exchanger (not shown) similar to heat exchanger 27 for this purpose. As described above, the methanol reactor 6 receives a CO2-rich stream via flue gas line 5 and a hydrogen (H2) stream via hydrogen line 7. Via catalytic reaction, methanol (CH3OH) is produced. The output of the methanol reactor 6 is led to a distillation unit 13, for example a distillation column, via line 31. From the distillation unit 13, methanol can be extracted via outlet line 32. In the distillation unit 13, various other substances may be separated out during the process of producing methanol. A certain amount of water may be separated out in the distillation unit 13, and this water can be led back to the electrolyser 8 via water supply line 12. This water can thus be used for production of hydrogen and oxygen in the process. The distillation unit 13 may also produce various byproducts which comprise carbon or hydrocarbons (for example other hydrocarbon gases or alcohols). These byproducts can be led back to the supply line 1 or the inlet line 3 via a byproduct return line, indicated as B in Fig. 1, and from there into the power plant 4. In this manner, such byproducts are fed back into the process and can be combusted in the combustion chamber 21. Optionally, some or all by-products may be vented or discharged from plant 100, for example to a treatment or disposal facility. In some examples, the methanol reactor 6 and / or the distillation unit 13 may require heat energy for their operation. Heat for this purpose can be provided from the power plant 4. This is schematically indicated by dashed lines and denoted Q in Fig. 1. Such heat Q can, for example, be provided via a dedicated heating loop which for example exchanges heat with the working fluid of the heat engine 20 (e.g. in the cooler 26) or with the fluid stream in the boiler chamber 22 and / or the condenser unit 24. There may, for example, be a dedicated heat exchanger similar to heat exchanger 23 for this purpose, or a heat transfer circuit may be operatively connected to heat exchanger 23. In any of the fluid lines, even if not explicitly mentioned here, appropriate flow control components may be arranged, including means to increase or decrease fluid pressure, such as pumps, compressors, expanders or throttles, if necessary. This may, for example, be the case for oxygen supply line 14, water supply line 12, and / or other fluid lines, in order to bring the respective fluid streams to appropriate pressure levels. The plant inlet line 3 (optionally also the pump 2), combustion chamber 21, boiler chamber 22, condenser unit 24 and flue gas line 5 make up a working media flowpath, i.e. a structurally defined fluid passage, which is delimited on its upstream side by the supply line 1 and on its downstream side by the methanol reactor 6. The electrolyser 8 is fluidly connected with the working media flowpath so as to allow injection of oxygen (O2) into the working media flowpath and the condenser unit 24 comprises a water outlet line, which may be connected to (or be identical to) the water supply line 11 to the electrolyser 8 (or the water outlet line may discharge condensed water elsewhere). The working media flowpath does not have a turbine or other type of mechanical gas expander unit arranged therein. In this manner, a substantially constant pressure level can be maintained along the working media flowpath, save for general flow losses. The plant 100 may be configured for operation with a pressure in the working media flowpath of above 20 bara. As such, the combustion in the combustion chamber 21 may take place at such elevated pressure of 20 bara or above. Optionally, the plant may be configured for operation with pressure above 50 bara in the working media flowpath. The pressure in the working media flowpath will provide a substantially corresponding delivery pressure at the flue gas line 5, such that an additional pressurization of the flue gas for supply to the methanol reactor 6 may not be necessary, or the pressurization energy required may be reduced. The pump 2 may be operable to or configured to increase the pressure of the fuel stream to this pressure, if the pressure in the supply line 1 is lower. Alternatively, illustrated in Fig. 3, the flue gas line 5 may comprise a flue gas compressor 5a. This may be beneficial if the pressure in the upstream parts, such as the combustion chamber 21, is lower than a desired supply pressure for flue gas to the methanol reactor 6. For example, if the design operating pressure in the combustion chamber 21 is 20 bara and the operating pressure of the methanol reactor 6 is 50 bara, the flue gas compressor 5a can be used to increase the pressure in the flue gas stream in flue gas line 5. Also illustrated in Fig. 3, in some examples the hydrogen line 7 may be fluidly connected to the flue gas line 5 upstream the flue gas compressor 5a, such as to feed in produced hydrogen into the flue gas line 5. In this manner, the CO2-containing flue gas and the hydrogen can be mixed and compressed together in the flue gas compressor 5a, which may provide more efficient compression and / or reduced plant complexity and cost. A flue gas compressor 5a may, however, also be used in the flue gas line 5 of the arrangement illustrated in Fig. 1, and with a dedicated hydrogen compressor 9. Advantageously, the operating pressure of the methanol reactor 6 is above 50 bara and the pressure in the working media flowpath, hereunder combustion chamber 21, is also above 50 bara. In such an example, there may be no need for additional pressurization of the flue gas stream to the methanol reactor 6. The byproduct return line B can be arranged to receive non-methanol hydrocarbons from the distillation unit 13 arranged downstream the methanol reactor 6 and to lead these into the working media flowpath upstream the combustion chamber 21. The byproduct return line B may comprise a pump 38 (illustrated in Fig. 3) for this purpose, however the pressure levels in the system may in some examples be such that no pump is required to drive the flow in the byproduct return line B. Particularly, in examples where a pump 2 is used, the byproduct return line B may be configured to lead the non-methanol hydrocarbons into the working media flowpath upstream the pump 2, as illustrated in Figs 1 and 3. The hydrogen compressor 9 may be configured to increase a pressure of the hydrogen (H2) supplied to the methanol reactor 6 to above 50 bara. For example, the electrolyser 8 may have an operating pressure of around 30 bara and the methanol reactor 6 may have an operating pressure of above 50 bara, in which case a compressor 9 may be used to pressurize the hydrogen stream in the hydrogen line 7. Advantageously, the electrolyser 8 may have an operating pressure of above 50 bara and the water supply to the electrolyser 8 (via lines 10, 11 and / or 12) may be provided at above 50 bara. The lines 10, 11 and / or 12 may comprise pump(s) for this purpose. The water supply and the internal operating pressure of the electrolyser 8 may be higher than the pressure in the working media flowpath and / or higher than operating pressure in the methanol reactor 6. In such cases, there may be no need for compression in the oxygen supply line 14 and in the hydrogen line 7. Advantageously, in some examples, the plant 100 may be operated with a pressure in the working media flowpath which is higher than operating pressure in the methanol reactor 6. Optionally, both the operating pressures in the working media flowpath and in the electrolyser 8 may be higher than operating pressure in the methanol reactor 6. This may further reduce compression work and compression equipment required in the plant 100. In some examples, illustrated in Fig. 3, the plant 100 may optionally comprise an additional CO2 input line 33. Through line 33, CO2 may for example be received from other sources and utilized for the purpose of synthesizing methanol. The CO2 received from the CO2 input line 33 can, for example, be supplied into the working media flowpath upstream the combustion chamber 21, which can be beneficial for controlling the combustion temperature in the combustion chamber 21. With reference to Fig. 4, the plant 100 may comprise a flue gas recirculation line 39 configured to receive a flue gas from the working media flowpath downstream the gas condenser unit 24 and provide the received flue gas into the working media flowpath upstream the combustion chamber 21. A flue gas recirculation pump 39a can be provided in the flue gas recirculation line 39 for this purpose. Such recirculation of flue gas can be beneficial for controlling the combustion temperature in the combustion chamber 21. In addition to the described components above, other fluid treatment components may be employed, for example filters to remove impurities (such as solids) in one or 5 more of the fluid streams. Advantageously, a methanol production plant 100 according to some examples described herein may be suitable for use of biofuels and / or hydrocarbon fuels having inherently high CO2 content. In some examples, biogas or gasified biomaterial (e.g. wood or biocoals) can be used. 10 In any of the embodiments described here, the term “line” when used in relation to fluid flows should be understood as a conduit capable of transporting the fluid in question. The line may be a pipe, channel, duct, or the like, selected according to which fluid is to be transported and the state thereof. The invention is not limited by the embodiments described above; reference should 15 be had to the appended claims.

Claims

20 01 251. A methanol production plant (100) comprising: a supply line (1) for a hydrocarbon fuel, a power plant (4) having a combustion chamber (21), a boiler chamber (22) with a heat exchanger (23) arranged therein, and a gas condenser unit (24),a methanol reactor (6) operatively arranged to synthesise methanol (CH3OH) from carbon dioxide (CO2) and hydrogen (H2), and an electrolyser (8), whereinthe combustion chamber (21), boiler chamber (22) and exhaust gas condenser unit (24) are fluidly interconnected in a working media flowpath extending between the supply line (1) and the methanol reactor (6),the electrolyser (8) is operatively arranged to provide oxygen (O2) to the combustion chamber (21) and hydrogen (H2) to the methanol reactor (6), and whereinthe working media flowpath has no mechanical fluid expander therein.

2. The methanol production plant (100) of any preceding claim, wherein the combustion chamber (21) is fluidly connected to the supply line (1) via a pump (2).

3. The methanol production plant (100) of any preceding claim, wherein the pump (2) is operable to or configured to increase a pressure of hydrocarbon fuel received from the supply line (1) to a pressure above 20 bara, optionally to a pressure above 50 bara.

4. The methanol production plant (100) of any preceding claim configured for operation with a pressure in the working media flowpath of above 20 bara, optionally with a pressure above 50 bara.

5. The methanol production plant (100) of any preceding claim, wherein the methanol reactor (6) is fluidly connected to the gas condenser unit (24) via a20 01 25flue gas line (5), and the flue gas line (5) comprises a flue gas compressor (5a) arranged therein.

6. The methanol production plant (100) of any preceding claim, wherein the flue gas compressor (5a) is configured to increase a pressure in a flue gas stream received from the gas condenser unit (24) to a pressure above 50 bara.

7. The methanol production plant (100) of any preceding claim, wherein the electrolyser (8) is operatively arranged to provide hydrogen (H2) to the methanol reactor (6) via a hydrogen line (7) fluidly connected to the flue gas line (5) upstream the flue gas compressor (5a).

8. The methanol production plant (100) of any preceding claim, comprising a byproduct return line (B) arranged to receive non-methanol hydrocarbons from a distillation unit (13) arranged downstream the methanol reactor (6) and to lead the non-methanol hydrocarbons into the working media flowpath upstream the combustion chamber (21).

9. The methanol production plant (100) of any preceding, wherein the byproduct return line (B) is configured lead the non-methanol hydrocarbons into the working media flowpath upstream the pump (2).

10. The methanol production plant (100) of any preceding claim, wherein the electrolyser (8) is operatively arranged to provide hydrogen (H2) to the methanol reactor (6) via a hydrogen compressor (9).

11. The methanol production plant (100) of any preceding claim, wherein the hydrogen compressor (9) is configured to increase a pressure of the hydrogen (H2) to above 50 bara.

12. The methanol production plant (100) of any preceding claim, comprising at least one water supply line (10,11,12) configured to supply water to the electrolyser (8) at a pressure above 20 bara, or at a pressure above 50 bara.20 01 2513. The methanol production plant (100) of any preceding claim, wherein the electrolyser (8) is configured to receive water (H2O) from the exhaust gas condenser unit (24) and / or from a distillation unit (13) arranged downstream the methanol reactor (6).

14. The methanol production plant (100) of any preceding claim, wherein the hydrocarbon fuel is a gaseous hydrocarbon fuel.

15. The methanol production plant (100) of any preceding claim, wherein the power plant (4) comprises a closed cycle heat engine (20) operatively connected to the heat exchanger (23) and configured to produce an electric power output (P2).

16. The methanol production plant (100) of any preceding claim, further comprising a CO2 input line (33) configured to supply CO2 into the working media flowpath.

17. The methanol production plant (100) of any preceding claim, wherein the CO2 input line (33) is configured to supply CO2 into the working media flowpath upstream the combustion chamber (21).

18. The methanol production plant (100) of any preceding claim, wherein the power plant (4) comprises a flue gas recirculation line (39) configured to receive a flue gas from the working media flowpath downstream the gas condenser unit (24) and provide the received flue gas into the working media flowpath upstream the combustion chamber (21).

19. A method for producing methanol, the method comprising: operating a methanol production plant (100) according to any preceding claim to produce methanol (CH3OH).

20. The method according to claim 19, comprising operating the methanol production plant (100) with a pressure in the working media flowpath above 20 bara, optionally with a pressure in the working media flowpath above 50 bara.20 01 2521. The method according to any preceding method claim, comprising operating the electrolyser (8) with an operating pressure of above 20 bara, optionally above 50 bara.

22. The method according to any preceding method claim, comprising operating the electrolyser (8) with an operating pressure which is higher than a pressure in the working media flowpath.

23. The method according to any preceding method claim, comprising providing water to the electrolyser (8) with a water pressure of above 20 bara, optionally above 50 bara.

24. The method according to any preceding method claim, comprising providing water to the electrolyser (8) with a water pressure which is higher than a pressure in the working media flowpath and / or higher than an operating pressure in the methanol reactor (6).

25. The method according to any preceding method claim, comprising operating the plant (100) with a pressure in the working media flowpath which is higher than an operating pressure in the methanol reactor (6).

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