Method for upgrading biogas to methanol

Abstract

To provide a method for upgrading biogas to methanol.SOLUTION: A method for upgrading biogas to methanol, comprises the steps of: providing a reformer feed stream comprising biogas; optionally, purifying the reformer feed stream in a gas purification unit; optionally, prereforming the reformer feed stream together with a steam feedstock in a prereforming unit; carrying out steam methane reforming in a reforming reactor heated by means of an electrical power source, providing the synthesis gas to a methanol synthesis unit to provide a product comprising methanol and an off-gas. Then invention also relates to an apparatus for upgrading biogas to methanol.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Aspects of the present invention generally relate to methods and apparatus for upgrading biomass to methanol.

Background Art

[0002] Biogas is a renewable energy source that can be used for heating, electricity, and many other operations. Biomass can be purified and upgraded to natural gas standard when it becomes biomethane. Biogas is considered a renewable resource because its production and use cycle is continuous and it generates substantially no carbon dioxide. When organic materials grow, they are converted and used. This then regrows in a continuously repeating cycle. From the perspective of the future of carbon, when materials are ultimately converted to energy, the carbon dioxide that is emitted is absorbed from the atmosphere in the growth of primary biological resources. Biogas is a mixture of gases produced by the decomposition of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural waste, manure, general waste, plant material, sewage, green waste, or food waste. Biogas consists mainly of methane (CH4) and carbon dioxide (CO2), and may contain small amounts of hydrogen sulfide (H2S), moisture, siloxanes, and possibly other components. Up to 30% or even up to 40% of biogas can be carbon dioxide. Typically, this carbon dioxide is removed from the biogas and discharged to provide a methane-enriched gas for secondary processing or to supply it to the natural gas network.

[0003] Biogas has been pointed out as an essential platform for realizing a circular industrial economy, in which case it enables the integration of waste streams back into the industry. Such a strategy allows for a departure from the "resource input, production, waste" society established in the 20th century and a transition to a "production, use, return" society, which is necessary to achieve a truly sustainable future. This idea is gaining interest within Europe, and large-scale biogas plants have already been installed. Within Denmark alone, significant production capacity has already been installed, and it is expected to increase to 17 PJ / a by 2020, although the overall potential could be as much as 60 PJ / a in Denmark. Currently, biogas plants are typically connected to the natural gas supply network, as this is the most feasible utilization method. However, the nature of biogas, which contains approximately 40% CO and 60% CH4, requires the removal of CO2 from the gas, so it is not permitted to mix it directly into the natural gas network, which requires a gas separation plant.

[0004] One of the problems of the present invention is to provide a method and apparatus in which the carbon dioxide of biogas is also utilized in the production of products. One of the problems of the present invention is to provide a method and apparatus for converting biogas into methanol. Yet another problem of the present invention is to provide a sustainable method and apparatus for converting biogas into methanol.

Summary of the Invention

[0005] The present invention relates to the sustainable production of methanol from biogas by applying an electrically heated steam methane reformer (eSMR) that enables a realistic zero-emission plant in which carbon is fully or substantially fully utilized.

[0006] Aspects of the present invention generally relate to methods and apparatuses for upgrading biomass to methanol.

[0007] A first aspect of the present invention is a method for upgrading biogas to methanol, comprising the following steps: a) providing a reformer feed stream comprising biogas; b1) optionally, purifying the reformer feed stream in a gas purification plant; b2) optionally, pre-reforming the reformer feed stream in a pre-reforming unit together with a steam feedstock; c) performing steam methane reforming of the reformer feed stream in a reforming reactor comprising a pressure shell containing a structured catalyst arranged to catalyze steam reforming of the reformer feed stream, wherein the structured catalyst comprises a macrostructure of an electrically conductive material, the macrostructure carrying a ceramic coating, and the ceramic coating carrying a catalytically active material; relates to a method comprising.

[0008] The steam methane reforming comprises the following steps: - c1) feeding the reformer feed stream to the reforming reactor; - c2) subjecting the reformer feed stream to a steam reforming reaction on the structured catalyst and discharging the syngas from the reforming reactor; and - c3) supplying power through an electrical conductor connecting a power supply source installed outside the pressure shell to the structured catalyst, passing an electric current through the electrically conductive material of the macrostructure, thereby heating at least a part of the structured catalyst to a temperature of at least 500 °C; d) feeding at least a part of the syngas of step c2) to a methanol synthesis unit to provide a product comprising methanol and offgas. comprises.

[0009] Conventional methanol production involves steam reforming of hydrocarbons followed by a methanol synthesis unit; this results in significant associated CO2 emissions. Step d) of feeding at least a portion of the syngas to the methanol synthesis unit also includes cases where water is removed from the syngas before introducing the syngas, in this case dry or drier syngas, to the methanol synthesis gas unit. The syngas obtained in step c) can be cooled, for example, upstream of the methanol synthesis unit, to a temperature lower than the dew point of the gas and separated into a liquid phase containing water and a gas phase containing dry syngas.

[0010] Furthermore, CO2 is typically removed in a gas separation unit from the biogas, i.e., the reformer feed stream, before feeding the remaining gas, together with steam, to the steam methane reformer. The CO2 by-product is typically either vented to the atmosphere or, if possible, collected and sold as a chemical. Instead of building a separation plant to remove / upgrade the CO2 of the biogas, the native mixture of CO2 and CH4 is a good feedstock for methanol production by sSMR, in which case essentially all carbon atoms can be converted to methanol. Such a plant combined with a biogas plant can be made more attractive simply because a substantially higher price setting of the final product is achieved by producing methanol beyond methane.

[0011] Furthermore, this conventional methanol production offers few opportunities for energy storage and does not bottleneck the increase and decrease of energy associated with renewable electricity. Since the highly endothermic steam reaction is promoted in a combustion reformer using a large furnace operating at a temperature near 1000 °C, the process economy is significantly supported by economies of scale that enable high process efficiency and integrated waste heat management. Therefore, such plants are economically difficult to downscale due to their integrated design and large upfront capital investment. As a result, typical methanol plants have a production capacity exceeding 2000 MT / d.

[0012] An alternative route for methanol production is the electrolysis of water for hydrogen generation, which is mixed with CO2 for methanol production. This concept has been demonstrated and is already being carried out in Iceland at a production capacity of 11 MT / d by using alkaline electrolysis for hydrogen production. However, such plants are limited to locations where large amounts of electricity are available, the price of electricity is low, and / or high-grade CO2 is easily accessible. In particular, CO2 is a scarce resource and typically not attractive for its utilization from a financial perspective. Overall, the process economics of an electrolysis-operated front-end for a methanol plant remain very high compared to traditional reforming methods, as the separation / purification of CO2 combined with the electrolysis of water and subsequent compression uses very high net energy and, overall, the methanol production price is 4 to 6 times higher than that of equivalent fossil fuels. Using only CO2 and hydrogen as makeup gas to methanol synthesis also requires more catalyst inventory and larger reactors, etc., due to the low reactivity of the gas. The use of co-electrolysis by solid oxide electrolysis cells (SOEC) enables more efficient and small-scale methanol synthesis, but this approach is currently only at the laboratory scale. In addition, generally, electrolysis also currently requires high upfront capital investment, which only poses more challenges to the process economics.

[0013] The term "methanol synthesis unit" means one or more reactors configured to convert synthesis gas to methanol. Such reactors can be, for example, a boiling water reactor, an adiabatic reactor, a condensed methanol reactor or a gas cooled reactor. Further, these reactors can be a number of parallel shells or a continuous reactor shell with heat exchange and / or product condensation arranged in between. The methanol synthesis unit also includes means for recycling and pressurizing the feed to the methanol reactor(s). The term "reformer feed stream" means both the reformer feed stream containing biogas and the purified reformer feed stream, the pre-reformed reformer feed stream, and the reformer feed stream to which hydrocarbon gas has been added and / or steam has been added and / or hydrogen has been added and / or offgas from the methanol synthesis unit has been added. All components of the reformer feed stream are pressurized separately or together upstream of the reforming reactor. Typically, steam is pressurized separately and the other components of the reformer feed stream may be heated together. The pressure(s) of the components of the reformer feed stream are selected such that the pressure in the reforming reactor is between 5 and 100 bar, preferably between 20 bar and 40 bar, or preferably between 70 bar and 90 bar.

[0014] In one aspect, at least a portion of the power supplied is generated by a renewable energy source. The full utilization of methanol as an energy vector cannot be achieved unless more optimal production routes are introduced. For this purpose, the method and plant of the present invention use renewable electricity to increase the energy value of the biogas in the reformer feed stream to methanol. The electrically heated steam methane reformer (eSMR) is a very compact reforming reactor, and as a result, the capital investment is lower than that of conventional steam reforming plants. The feedstock to the eSMR can in principle be from any methane-containing source such as biogas or natural gas, but since the heating is facilitated by electricity, this represents an improvement over existing combustion reformers in terms of reducing direct CO2 emissions. In addition, there is an excellent synergy with the biogas feedstock that enables substantially complete conversion of all the carbon in the biogas to methanol.

[0015] In the context of the present invention, the term "biogas" means a gas having the following composition:

[0016] [Table 1]

[0017] In one aspect, the reformer feed stream has a first H / C ratio, and a second hydrocarbon feed gas having a second H / C ratio is mixed with the reformer feed stream upstream of the reforming reactor, provided that the second H / C ratio is greater than the first H / C ratio. Examples of the second hydrocarbon feed can be natural gas or shale gas. Here, the H / C ratio of the gas is the ratio between the hydrogen atoms and carbon atoms in the gas, both in the hydrocarbon and other gas components.

[0018] In one aspect where an electrolysis unit is used to generate a hydrogen-enriched stream from a water feedstock, this hydrogen-enriched stream is added to the synthesis gas to balance the module M of the synthesis gas to be in the range of 1.5 to 2.5. The module M of the synthesis gas is given by the following formula.

[0019]

Number

[0020] In one embodiment, the electrolysis unit is a solid oxide electrolysis cell unit, and the water feedstock is in the form of steam generated from other processes of the method. The steam is generated, for example, in a methanol synthesis unit, i.e., downstream of the eSMR in an apparatus for upgrading biogas to methanol, or is steam generated in a methanol synthesis gas unit or a waste heat boiler.

[0021] In one embodiment, a membrane unit or a pressure swing adsorption (PSA) unit is included in the methanol synthesis unit to extract at least a portion of hydrogen from the offgas and return this at least a portion of hydrogen to the synthesis gas to balance the module M of the synthesis gas in the range of 1.5 to 2.5. Preferably, the module M of the synthesis gas is balanced to be in the range of 1.95 to 2.1. Also in this case, the module M is defined as follows:

[0022]

Number

[0023] In one embodiment, the pressure of the gas in the reformer is between 20 bar and 100 bar, preferably between 50 bar and 90 bar.

[0024] In one embodiment, the temperature of the gas exiting the reforming reactor is between 900 °C and 1150 °C.

[0025] In one embodiment, the space velocity evaluated as the gas flow rate with respect to the geometric surface area of the structured catalyst is 0.6 Nm 3 / m 2 / h and 60 Nm 3 / m 2 / h, and / or the gas flow rate with respect to the occupied volume of the structured catalyst is between 700 Nm 3 / m 3 / h and 70000 Nm 3 / m 3 / h. Preferably, the gas flow rate with respect to the occupied volume of the structured catalyst is between 7000 Nm 3 / m 3 / h and 10000 Nm 3 / m 3 / h.

[0026] In one embodiment, the plot area of the reforming reactor is between 0.4 m 2 and 4 m 2 . Preferably, the plot area is between 0.5 m 2 and 1 m 2 . Here, the term "plot area" is synonymous with "land area", i.e., the area of the land occupied when the reforming reactor is installed.

[0027] In one embodiment, the production of methanol is adjusted according to the availability of renewable energy.

[0028] In one embodiment, the method further includes the step of upgrading crude methanol to fuel-grade methanol.

[0029] In one embodiment, the methanol is upgraded to chemical-grade methanol.

[0030] In one embodiment, the method further includes using at least a portion of the methanol from step d) in an apparatus for the production of a transportation fuel. In particular, the methanol is used as a feedstock in an apparatus for the synthesis of gasoline from methanol.

[0031] In one embodiment, between 80% and 100% of the carbon in the biogas of the reformer feed stream is converted to MeOH.

[0032] In one embodiment, the amount of biogas in the reformer feed stream is 500 Nm 3 / h to 8000 Nm 3 / h.

[0033] In one embodiment, a separation unit is used to remove a portion of the CO2 of the biogas in the reformer feed stream after step a) and before step d). If a pre-reformer unit is present, the removal of CO2 is preferably carried out upstream of the pre-reformer unit, i.e., before step b2). If a purification unit is present, the removal of CO2 is preferably carried out upstream of the purification unit, i.e., before step b1). The separation unit is, for example, a membrane unit.

[0034] Advantageously, the apparatus for the upgrading of biogas to methanol includes both a membrane unit for removing a portion of the CO2 in the biogas of the reformer feed stream upstream of the reformer reactor and a SOEC. Therefore, the apparatus can switch between using the membrane unit during periods when electricity is scarce and using the SOEC during periods when electricity is relatively abundant. In this way, the module degradation due to reducing the amount of CO2 added to the process is regulated, and on the other hand, during periods when electricity is abundant, the membrane can be bypassed and excess hydrogen can be produced by the SOEC to balance the module.

[0035] When a reformer feed stream containing more than 25% CO2 is used as a feedstock for the process of the present invention, due to the overall reaction scheme of methanol production below, it is advantageous to remove some of the CO2 in order to reach a reformer feed stream containing about 25% CO2 and about 75% CH4; 0.75CH4 + 0.25CO2 + 0.5H2O → CO + 2H2 → CH3OH

[0036] In one aspect of the present invention, a portion of the off-gas produced in step d) is recycled to a biogas production facility for producing biogas to be upgraded by the process of the present invention. Since the off-gas typically contains a high content of hydrogen, this hydrogen can be used in the biogas production facility, i.e., the fermentation plant, where it can react with carbon oxides to produce methane. In fact, in a process design where a certain amount of hydrogen-rich off-gas is recycled to the biogas production facility, the biogas produced will have a higher CH4 / CO2 compared to the biogas produced in a biogas production facility that does not recycle the hydrogen-rich off-gas.

[0037] Another aspect of the present invention is an apparatus for upgrading biogas to methanol, - Optionally, a gas purification unit, - Optionally, a pre-reforming unit, - A reforming reactor comprising a pressure shell containing a structured catalyst arranged to catalytically steam reform a hydrocarbon-containing feed gas, provided that the structured catalyst comprises a macrostructure of an electrically conductive material that supports a ceramic coating, where the ceramic coating supports a catalytically active material; and the reforming reactor further comprises a power supply arranged outside the pressure shell and an electrical conductor connecting the power supply to the structured catalyst to pass an electric current through the electrically conductive material of the macrostructure, thereby heating at least a portion of the structured catalyst to a temperature of at least 500 °C; - A methanol synthesis unit that receives synthesis gas from a reformer and is arranged to produce a product containing methanol and off-gas, relates to an apparatus comprising.

[0038] The structured catalyst of the reformer of the apparatus is configured for steam reforming. This reaction occurs according to the following reactions: CH4 + H2O ⇔ CO + 3H2 CH4 + 2H2O ⇔ CO2 + 4H2 CH4 + CO2 ⇔ 2CO + 2H2

[0039] The structured catalyst is composed of a metal structure, a ceramic phase, and an active phase. The metal structure may be an FeCr alloy, alnico, or a similar alloy. The ceramic phase may be Al2O3, MgAl2O3, CaAl2O3, ZrO2, or a combination thereof. The catalytic active material may be Ni, Ru, Rh, Ir, or a combination thereof.

[0040] In one aspect, catalyst pellets are loaded on, around, inside, or below the upper surface of the structured catalyst of the reformer. The catalyst material for the reaction may be Ni / Al2O3, Ni / MgAl2O3, Ni / CaAl2O3, Ru / MgAl2O3, or Rh / MgAl2O3. The catalytic active material may be Ni, Ru, Rh, Ir, or a combination thereof. This can improve the overall gas conversion in the reformer.

[0041] In one aspect, the macrostructure(s) has a plurality of parallel flow channels, a plurality of non-parallel flow channels, and / or a plurality of maze-like flow channels. These flow channels have walls that define each flow channel. A plurality of different planar and three-dimensional shapes of the macrostructure can be used if the surface area of the structured catalyst exposed to the gas is to be maximized. In one preferred aspect, the macrostructure has parallel flow channels, since such parallel flow channels provide a structured catalyst with a very small pressure drop. In one preferred aspect, parallel longitudinal flow channels are formed obliquely in the longitudinal direction of the macrostructure. In this way, most of the gas molecules flowing through the macrostructure tend to collide with the walls inside the flow channels, rather than flowing straight through the flow channels without necessarily contacting the walls. The dimensions of these flow channels should be appropriate to provide a macrostructure with sufficient resistance. For example, these flow channels can be square (when viewed as a cross-section perpendicular to the flow channel) and can have a side length of the square between 1 mm and 3 mm, but flow channels with a maximum dimension of up to about 4 cm in cross-section can also be considered. Further, the wall thickness should be thin enough to provide a relatively large electrical resistance and thick enough to provide sufficient mechanical strength. The wall can have a thickness, for example, between 0.2 mm and 2 mm, for example, a thickness of about 0.5 mm, and the ceramic coating supported by the wall can have a thickness between 10 μm and 500 μm, for example, between 50 μm and 200 μm, for example, a thickness of 100 μm. In another aspect, the macrostructure of the structured catalyst is cross-corrugated. Generally, when the macrostructure has parallel flow channels, the pressure drop from the inlet to the outlet of the reformer device can be significantly reduced compared to a reactor such as a standard SMR where the catalyst material is in the form of pellets.

[0042] In one aspect, the macrostructure(s) is / are an extruded and sintered structure. Alternatively, the macrostructure(s) is / are a 3D printed structure(s). The 3D printed structure can be provided with or without subsequent sintering. Extrusion or 3D printing of the macrostructure, optionally followed by sintering thereof, results in a uniformly and integrally shaped macrostructure, which can then be coated with a ceramic coating.

[0043] Preferably, the macrostructure is manufactured by 3D printing or extruding a mixture of powdered metal particles and a binder to form an extruded structure, and then sintering this extruded structure to provide a material having a high geometric surface area per unit volume. Preferably, the 3D printed extruded structure is sintered in a reducing atmosphere to provide the macrostructure. Alternatively, the macrostructure is 3D printed by a metal additive manufacturing melting process, i.e., a 3D printing process that does not require subsequent sintering, such as powder bed fusion bonding or directed energy deposition. Examples of such powder bed fusion or directed energy deposition methods are laser beam, electron beam, or plasma 3D printing methods. As another alternative, the macrostructure can be manufactured as a 3D metal structure by a binder-based metal additive manufacturing process and then sintered in a non-oxidizing atmosphere at a first temperature T1 > 1000 °C to form the macrostructure.

[0044] A ceramic coating that may contain a catalytically active material is applied onto the macrostructure before the second sintering in an oxidizing atmosphere. This is to form a chemical bond between the ceramic coating and the macrostructure. Alternatively, the catalytically active material may be impregnated onto the ceramic coating after the second sintering. When a chemical bond is formed between the ceramic coating and the macrostructure, particularly high heat conduction between the electrically heated macrostructure and the catalytically active material supported on the ceramic coating becomes possible, providing a near direct contact between the heat source and the catalytically active material of the structured catalyst. Since the heat source and the catalytically active material are in close proximity, heat transfer is effective, and as a result, the structured catalyst can be heated very efficiently. Therefore, a reforming reactor device can be made small in terms of gas processing per unit volume of the reforming reactor device, and thus, the reforming reactor device housing the structured catalyst can be made small. The reforming reactor device of the present invention does not require a furnace, which significantly reduces the overall reactor size. Furthermore, it is advantageous that the amount of syngas produced within a single pressure shell is considerably increased compared to known tubular steam reformers. In a standard tubular steam reformer, the amount of syngas produced in one tube of the tubular steam reformer is at most 500 Nm 3 / h. In contrast, the reactor system of the present invention is arranged for production up to or exceeding 2000 Nm 3 / h, for example even up to or exceeding 10000 Nm 3 / h within one pressure shell. This can be done in the absence of O2 in the feed gas and with a methane content of less than 10% in the produced syngas. When one pressure shell houses a catalyst for producing up to 10000 Nm 3 / h of syngas, there is no longer a need to provide multiple pressure shells or means for distributing the feed gas to multiple such separate pressure shells.

[0045] As used herein, the recitation of "3D printing" is intended to refer to metal additive manufacturing processes. Such metal additive manufacturing processes include 3D printing methods in which materials are joined to a structure under computer control, where the structure should be solidified, for example, by sintering, to provide the macrostructure. Further, such metal additive manufacturing processes include 3D printing methods that do not require subsequent sintering, such as powder bed fusion methods or directed energy deposition methods. Examples of such powder bed fusion methods or directed energy deposition methods are laser beam, electron beam, or plasma 3D printing methods.

[0046] Preferably, the catalytically active material is particles having a size of 5 nm to 250 nm. The ceramic coating may be, for example, an oxide containing Al, Zr, Mg, Ce, and / or Ca. Exemplary coatings are calcium aluminate or magnesium aluminum spinel. Such ceramic coatings may further contain another element, such as La, Y, Ti, K, or combinations thereof. Preferably, the conductor is made of a material different from the macrostructure. The conductor can be made of, for example, iron, nickel, aluminum, copper, silver, or alloys thereof. The ceramic coating is an electrically insulating material and typically has a thickness in the range of about 100 μm, for example, in the range of 10 - 500 μm.

[0047] The macrostructure is advantageously a cohesive or consistently internally connected material in order to achieve electrical conductivity throughout the macrostructure, thereby achieving thermal conductivity throughout the structured catalyst, and in particular to provide heating of the catalytically active material supported by the macrostructure. A cohesive or consistently internally connected material can ensure a uniform distribution of current within the macrostructure and thus a uniform distribution of heat within the structured catalyst. Throughout this specification, the term "cohesive" is intended to refer to a material that is consistently internally connected or internally bonded. The effect of a structured catalyst that is a cohesive or consistently internally connected material lies in the fact that control over the connectivity within the material of the structured catalyst and thus the conductivity of the macrostructure is obtained. Even if further modifications of the macrostructure are made, such as providing slits into a part of the macrostructure or providing insulating material into the macrostructure, it should be noted that the macrostructure is still referred to as a cohesive or consistently internally connected material.

[0048] In one aspect, the structured catalyst has an electrically insulating portion arranged to lengthen the current path between conductors to a length longer than the longest dimension of the structured catalyst. Providing a current path between conductors longer than the maximum dimension of the structured catalyst may be by providing an electrically insulating portion located between the conductors that impedes the flow of current through a part of the structured catalyst. Such an electrically insulating portion is arranged to lengthen the current path and thus increase the resistance of the structured catalyst. In one aspect, at least one electrically insulating portion has a length defined to ensure that the minimum current path between conductors is longer than the maximum dimension of the macrostructure.

[0049] Non-limiting examples of such insulating portions are cuts, slits or holes in the structure. Optionally, a solid insulating material such as ceramic in a cut or slit in the structure can be used. When the solid insulating material is a porous ceramic material, the catalytically active material can be advantageously included in the pores, for example by impregnation. The solid insulating material within the cut or slit helps to keep the portions of the structured catalyst on each side of the cut or slit separated from each other. As used herein, the description "maximum dimension of the structured catalyst" means the largest inner dimension of the geometric shape taken by the structured catalyst. If the structured catalyst is box-shaped, the maximum dimension will be the diagonal (also referred to as the body diagonal) from one corner to the corner furthest away.

[0050] The current flowing through the structured catalyst may be arranged to twist or meander its path through the structured catalyst by means of an electrically insulating portion arranged to lengthen the current path, but it should be noted that the gas passing through the reformer reactor device is introduced at one end of the reformer reactor device and passes through the structured catalyst once before being discharged from the reformer reactor device. Advantageously, an inert material is present in the relevant voids between the structured catalyst and the rest of the reformer reactor device to ensure that the gas within the reformer reactor device passes through the structured catalyst and the catalytically active material supported thereby.

[0051] In one aspect, the gas flow path in the structured catalyst is shorter than the length of the current path from one conductor, through the structured catalyst, to the next conductor. The ratio of the length of the gas flow path to the length of the current path may be less than 0.6, less than 0.3 or less than 0.1, or even up to 0.002.

[0052] In one aspect, the structured catalyst has an electrically insulating portion arranged to make the current path in the structured catalyst a zigzag path. Here, the descriptions "zigzag path" and "zigzag route" mean a path having corners at various angles that trace a path from one conductor to another. A zigzag path is, for example, a path that rises, turns, and then descends. Although one turning portion is sufficient to make the path a zigzag path, the zigzag path may have many turning portions and may rise and then descend many times through the structured catalyst.

[0053] The following is a detailed description of the aspects of the present invention shown in the accompanying drawings. These aspects are examples and are described in detail to clearly convey the present invention. However, the degree of detail of the description is not intended to limit the expected variations of the aspects. On the contrary, it is intended to include all modifications, equivalents, and alternatives that fall within the spirit and scope of the present invention as defined by the appended claims.

Brief Description of the Drawings

[0054]

Figure 1

Figure 2

Figure 3

Figure 4

[0055] [Detailed Description of the Drawings] FIG. 1 is a schematic diagram of an apparatus 100 for biogas upgrading to methanol production. This apparatus is a methanol plant equipped with an electrically heated steam methane reformer (eSMR) 10.

[0056] The apparatus 100 for biogas upgrading to methanol includes a reforming section 10 and a methanol section 60. The reforming section 10 includes a preheating section 20, a purification unit 30, such as a desulfurization unit, a pre-reformer 40, and an eSMR 50. The methanol section includes a first separator 85, a compression unit 70, a methanol synthesis unit 80, a second separator 90, and a heat exchanger. The first and second separators 65 and 90 may be, for example, flash separators.

[0057] The reformer feed stream 1 containing biogas is preheated in the preheating section 20 to become the preheated reformer feed stream 2, which is sent to the purification unit 30. The purified preheated reformer feed stream 3 is sent from the purification unit 30 to the preheating section 20 for further heating. Further, steam 4 is added to the purified preheated reformer feed stream, resulting in the feed gas 5, which is sent to the pre-reformer 40. The pre-reformed gas 6 exits the pre-reformer 40 and is heated in the preheating section 20 to become gas 7. In the embodiment of FIG. 1, hydrogen 14 is added to gas 7 to become the feed gas 8, which is sent to the eSMR 50. The feed gas 8 is steam methane reformed in the eSMR 50 to become the reformed gas 9, which is sent from the eSMR 50 and from the reforming section 10 to the methanol section 60.

[0058] In the methanol section 60, the reformed gas 9 heats water 12 in a heat exchanger to convert it into steam 13. In the first separator 85, water is separated from the synthesis gas 9 to provide dry synthesis gas 11, which is sent to a compressor 70 arranged to compress the dry synthesis gas before being mixed with the recycle gas from the second separator 90 and entering the methanol synthesis unit 80. Most of the methanol produced from the methanol synthesis unit 80 is condensed and separated in the second separator 90 and exits the methanol section as methanol 25. The gaseous components from the second separator 90 are divided into a first portion recycled to the methanol synthesis unit 80 and an off-gas 17 used as fuel 18 to the preheating section 20 of the reforming section 10 and / or recycled as a feed 16 to the eSMR 50 and / or a second portion recycled as a feed 16 to the eSMR 50. Typically, an additional compressor is used to recycle the first portion of the gaseous components from the second separator 95 to the methanol synthesis unit 80. The water 12 is heated to steam within the heat exchanger of the apparatus 100 and, in the described embodiment, within the cooling side of the methanol synthesis unit 80.

[0059] To achieve complete carbon utilization, a synergy can be obtained when using an SOEC-based water electrolysis unit 110. The SOEC unit 110 can utilize a portion of the steam production available from waste heat management in the reforming and methanol sections, such as stream 13, and convert this steam, among other things, into H2. This H2 can be used as a hydrogen source in the feed gas to the reforming reactor. Note that a relatively small SOEC unit is required to achieve this. Alternatively, any other suitable hydrogen source may be utilized.

[0060] When a second hydrocarbon feed gas is added to or mixed with the reformer feed stream upstream of the reformer reactor, this second hydrocarbon feed gas is typically added to the reformer feed stream upstream of the pre-reformer unit and the purification unit. In FIG. 1, this would correspond to the addition of the second hydrocarbon feed gas to the preheated reformer feed stream 2. This second hydrocarbon feed gas may be a natural gas stream having an H / C ratio higher than the H / C ratio of the reformer feed stream of stream 1.

[0061] When a separation unit is used to remove a portion of the CO2 in the biogas upstream of the reformer unit, this separation unit is preferably upstream of the preheating unit 20. When the main portion of the reformer feed stream is biogas, by removing a portion of the CO2 in the reformer feed stream, a reformer feed stream containing about 25% CO2 can be achieved, which is preferable for downstream methanol production.

[0062] The apparatus 100 according to the present invention including an electrically heated steam methane reformer and a methanol synthesis unit is also abbreviated as eSMR-MeOH. Such an eSMR-MeOH apparatus is mostly similar to the plants used in conventional industrial processes (SMR-MeOH), but differs in several essential aspects. First, the use of eSMR10 eliminates the requirements for strong combustion in the combustion type steam reformer of the conventional SMR-MeOH apparatus, thereby leaving only a small amount of CO2 emissions from the eSMR-MeOH layout involving the handling of purge gas. Second, the use of biogas instead of natural gas as the reformer feed stream or as the main portion thereof eliminates the requirement for oxygen addition to the synthesis gas because the natural high CO2 content of the biogas inherently enables module regulation as described below.

[0063] (From the overall plant stoichiometry when methane (as natural gas) is used as the feedstock, the reaction scheme can be expressed as follows: CH4+0.5O2→CO+2H2→CH3OH

[0064] Alternatively, if a CO2 feedstock is available, this can be used as an oxygen source, giving the following overall plant stoichiometry: 0.75CH4 + 0.25CO2 + 0.5H2O → CO + 2H2 → CH3OH

[0065] Compared with combustion reformers, eSMR can reach higher temperatures, which gives a higher methane conversion rate in this layout; ultimately, this reduces the handling of off-gas. Since the CO2 content in biogas can vary, the addition of hydrogen to the syngas can be advantageous for enhancing the carbon utilization of the process. To achieve complete carbon utilization, excellent synergistic effects can be obtained by using an SOEC-based water electrolysis unit 110. This water electrolysis unit 110 can utilize a portion of the steam production available from waste heat management in the reforming section 10 and the methanol section 60. This is shown as a parallel hydrogen source 14 in Figure 1. It should be noted that a relatively small SOEC unit 110 is required to achieve this, and that this process can operate without it. The same methanol synthesis technology as the conventional approach can be used, and the methanol reactor has a CO / CO2 ratio corresponding to that of a typical methanol plant in this layout, and thus has similar activity and stability. To some extent, at least a portion of the off-gas from the methanol synthesis unit can be recycled as feedstock to the reforming section for improving carbon efficiency and recovering unreacted methane. In the same way, at least a portion of the off-gas from potential methanol distillation can be recovered and compressed to the operating pressure, and then it can be returned as feedstock. At least to some extent, preheating can be carried out with excess steam because it is high-temperature preheating. Electrically heated reforming can use, for example, a monolithic catalyst directly heated by Joule heating to supply heat for the reaction. In short, eSMR 10 can be considered as a pressure shell with a centrally located catalyst monolith, and the catalyst monolith is connected to an external power source by a conductor passing through a dielectric component within the shell. The shell of the eSMR is a heat-resistant material lined to confine the high-temperature region to the center of the eSMR.

[0066] From the perspective of the reforming reactor, the eSMR has several advantages over conventional combustion reformers. One of the most obvious is that the reforming reactor is no longer limited to devices with a large external heat transfer area, so a much more compact reactor design can be made when using electrothermal technology. A two-digit size reduction is conceivable. This leads to a much lower capital investment in this technology. The integrated preheating and reforming section (including power supply) configuration of the eSMR was estimated to have a much lower capital investment. Since the syngas preparation section of a methanol plant accounts for more than 60% of the capital investment of a conventional combustion reformer-based methanol plant, a dramatic saving on reformer equipment leads to a significant reduction in the cost of an eSMR-based methanol plant.

[0067] Figures 2a - 2c show comparative examples of various methanol plants based on a combustion reformer (Figure 2a), an electrolytic reformer (Figure 2b), and an alkaline electrolysis (Figure 2c). The main advantage of the eSMR in Figure 2b is that it does not require burning hydrocarbons to supply heat for the reaction, and as a result, the direct CO2 emissions of this technology are significantly reduced. This is illustrated in Figures 2a - 2c, which show how the consumer goods and CO2 emissions can change significantly when using the eSMR - MeOH technology compared to both the combustion reformer method and the electrolysis method. The consumption in the combustion reformer layout (Figure 2a) and the eSMR - MeOH layout (Figure 2b) are both based on the flowsheet of Haldor Topsoe's development for chemical - grade methanol production (i.e., including product distillation). On the other hand, the electrolysis layout (Figure 2c) is a best - case overall stoichiometric analysis combined with the published consumption for alkaline electrolysis (AEL) based on H2 production and CO2 purification. From a chemical perspective, it should be noted that the consumer goods are substantially split into pure CH4 and CO2 so as not to disadvantage the SMR - MeOH layout by requiring combustion with biogas, which would increase the CO2 emissions from the SMR - MeOH plant. In a given case, the eSMR - MeOH achieves a 30% reduction in methane consumption and an 80% reduction in CO2 emissions compared to the combustion reformer (SMR - MeOH). It is emphasized that process improvements can be considered for all presented cases and should not, therefore, be considered limited. When units are not stated, the numbers given represent the relative molar flow rates of the components in Figures 2a - 2c.

[0068] The overview of the consumer goods in Figures 2a - 2c shows significantly lower electricity usage for methanol production when using eSMR - MeOH compared to electrolysis. By using SOEC instead of AEL in the electrolysis layout, the electricity usage can potentially be 11 - 13 kWh / Nm (depending on the availability of steam). 3It can be reduced to MeOH, which is an improvement of this technology but still significantly higher than eSMR-MeOH. Although concept development can still be carried out for electrolysis to improve the performance of this technology, this is still entirely at the research stage. Only the only established technology such as AEL combined with the conventional methanol synthesis technology can be considered ready for industrial applications at present, and this is also the reason for being the focus of comparison.

[0069] The energy consumption of methanol production by AEL (“AEL-MeOH”) is calculated as follows. E total =E AEL +E CO2 +E compress -E steam

[0070] Here, E AEL is the energy consumption of alkaline electrolysis at an energy efficiency of 71%. E CO2 is the energy consumption of CO2 purification, which is estimated to be 2.6 MJ / Nm 3 CO2 when flue gas is used as the feedstock. E compress is the compression power calculated as 0.7 kWh / Nm 3 methanol at an efficiency of 75% without including the energy for cooling water. E steam is the potential energy recovery from steam production calculated as 0.7 kWh / Nm 3 methanol with a 75% recovery rate of the exothermic energy removed in methanol synthesis. The above calculations do not include considerations regarding the formation of by-products in the methanol synthesis unit or their incorporation in the plant layout.

[0071] Figure 3 shows the CO2-equivalent emissions associated with methanol production for SMR, eSMR, and AEM respectively (CO2 e) is shown. For each of these production technologies, the black boxes represent the overall equivalent emissions (CO2e) when methanol is produced using renewable energy, and the white boxes represent the overall equivalent emissions (CO2e) when methanol is produced using electricity from the Danish power grid in 2019. When calculating the overall CO2 emissions from a chemical plant, it is necessary to also evaluate the electricity consumption, as this can also potentially result in a large CO2 emission footprint. The exact emissions depend on the electricity source. Note the associated equivalent CO2 emissions (CO2e) when the electricity is provided either by a completely sustainable resource or, as an example, by the Danish energy supply network in 2019, where more than 60% of the annual electricity usage is covered by sustainable resources such as solar cells, wind, and biomass. The actual CO2e for methanol production by the eSMR-MeOH technology is calculated as shown in Figure 3 based on this, and is evaluated relative to conventional combustion-based technologies and AEL-MeOH. Regardless of the electricity source, eSMR-MeOH significantly improves the CO2 footprint of the methanol product compared to the conventional method, i.e., SMR-MeOH. On the other hand, when based on the Danish energy supply network in 2019, the electrolysis method has no favorable effect on CO2e. Only when the electricity is completely renewable does the electrolysis method have a CO2e comparable to the eSMR-MeOH route, but AEL-MeOH is still 35% higher.

[0072] Figure 4 is an overview of the technologies with the minimum operating cost as a function of natural gas price and electricity price.

[0073] To make sustainable technologies attractive, they need to be cost-competitive compared to established manufacturing routes. Figure 4 shows an overview of which technologies give the minimum operating costs as a function of gas and electricity prices. Note that this overview shows only the operating costs. If the costs up to the depreciation of the plant are included in the production costs, the size of the area indicated as "eSMR-MeOH" increases significantly up to the areas indicated as "AEL-MeOH" and "SMR-MeOH", because the eSMR-MeOH technology requires considerably less capital investment compared to the two other technologies mentioned above. From this overview, it can be seen that the combustion technology (SMR-MeOH) was the cheapest manufacturing route in the previous century due to the low cost of gas. However, the decreasing electricity prices provide an incentive towards electrically operated technologies. The eSMR-operated front end is proposed as the next step towards a cost-competitive route for methanol production. To illustrate this opportunity, a competitive case can be found when compared to natural gas prices of approximately $6 - $8 / MMBTU in Europe. The operating costs of the eSMR-MeOH technology are even more favorable in the case where there is a CO2 tax. The CO2 tax significantly increases the operating costs of the combustion reformer method. This is shown by the dashed line in Figure 4, which represents the current typical CO2 tax in Northern Europe. Since the development within the eSMR-MeOH layout is still in a relatively early stage, it is emphasized that Figure 4 is for reference only. The development within eSMR-MeOH will further improve the consumption and thus the operating costs.

[0074] Having illustrated the invention in various embodiments and described these embodiments in considerable detail, it is not the intention of the inventor to reduce or in any way limit the scope of the appended claims to such detailed description. Additional advantages and modifications will be readily apparent to those skilled in the art. Therefore, the invention in its broadest aspect is not limited to the specific detailed description, representative methods, and examples described. Therefore, developments from such detailed description are possible without departing from the spirit or scope of the general inventive concept of the inventor.

Examples

[0075] Example 1 Example 1 relates to one aspect of the invention in which biogas is converted to methanol. Refer to Figure 1. The feed gas (1) is mixed with recycle gas from the methanol loop to provide hydrogen for the following desulfurization step (30) and pre-reforming step (40). This gas is converted to syngas with steam (4) using an electrically heated reformer (50). This is cooled and separated into condensate and dry syngas (11), where the dry syngas is compressed and fed to the methanol loop using a boiling water type methanol reactor (80). This compressed make-up syngas is mixed with recycle gas (95) in the loop and sent to the methanol reactor (80) to produce methanol. By cooling and condensing this methanol, the final product (25) is separated and produced. Most of the off-gas from this separation is recycled directly (95) to the methanol reactor, another fraction (16) is recycled to the feed, while the last fraction is exported as fuel-enriched off-gas.

[0076] Overall, this aspect of the method enables the conversion of 95.4% of the carbon feedstock (CO2+CH4) to methanol.

[0077]

Table 2

Claims

1. A method for upgrading biogas to methanol, comprising the following steps: a) providing a reformer feed stream comprising said biogas; b1) - optionally, purifying said reformer feed stream in a gas purification unit; b2) - optionally, pre-reforming said reformer feed stream in a pre-reformer unit together with a steam feedstock; c) performing steam methane reforming of said reformer feed stream in a reformer reactor comprising a pressure shell containing a structured catalyst arranged to catalyze steam reforming of said reformer feed stream, wherein said structured catalyst comprises a macrostructure of an electrically conductive material, said macrostructure carrying a ceramic coating, and said ceramic coating carrying a catalytically active material; provided that said steam methane reforming comprises the following steps: - c1) feeding said reformer feed stream to the reformer reactor; - c2) reacting the reformer feed stream in a steam reforming reaction on the structured catalyst and discharging the syngas from the reformer reactor; and - c3) supplying power through an electrical conductor connecting a power supply source installed outside said pressure shell to said structured catalyst, passing an electric current through the electrically conductive material of said macrostructure, thereby heating at least a part of the structured catalyst to a temperature of at least 500 °C; including; and d) feeding at least a part of the syngas of step c2) to a methanol synthesis unit to provide a product comprising methanol and offgas; said method comprising.

2. The method according to claim 1, wherein the power supplied is generated using a renewable energy resource.

3. The method according to claim 1 or 2, wherein said reformer feed stream has a first H / C ratio and a second hydrocarbon feed gas having a second H / C ratio is mixed with the reformer feed stream upstream of the reformer reactor, provided that the second H / C ratio is greater than the first H / C ratio.

4. An electrolysis unit is used to generate a hydrogen-enriched stream from a water feedstock, and said hydrogen-enriched stream is added to the syngas to balance the module of said syngas in the range of 1.5 to 2.5, the method according to any one of claims 1 to 3.

5. The method according to claim 4, wherein the electrolysis unit is a solid oxide electrolysis cell unit and the water supply raw material is in the form of steam generated from other processes of the method.

6. The method according to any one of claims 1 to 5, wherein a membrane unit or a PSA unit is included in the methanol synthesis unit to extract at least a part of hydrogen from the off-gas and return at least a part of the hydrogen from the off-gas to the syngas to balance the module of the syngas in the range of 1.5 to 2.

5.

7. The method according to any one of claims 1 to 6, wherein the combination of superheating of steam and generation of steam is integrated into the waste heat recovery of the syngas from the reformer, and the superheated steam is used as a steam supply raw material in step c) of the method for upgrading biogas to methanol.

8. The method according to any one of claims 1 to 7, wherein the pressure of the gas in the reformer is between 20 bar and 100 bar, preferably between 50 bar and 90 bar.

9. The method according to any one of claims 1 to 8, wherein the temperature of the gas exiting the reformer is between 900 °C and 1150 °C.

10. The space velocity evaluated as the flow rate of the gas with respect to the geometric surface area of the structured catalyst is between 0.6 Nm ３ / m ２ / h and 60 Nm ３ / m ２ / h, and / or the flow rate of the gas with respect to the occupied volume of the structured catalyst is between 700 Nm ３ / m ３ / h and 70000 Nm ３ / m ３ / h, the method according to any one of claims 1 to 9.

11. The plot area of the reforming reactor is between 0.4 m ２ and 4 m ２ The method according to any one of claims 1 to 10.

12. The method according to any one of claims 1 to 11, wherein the production of methanol is adjusted according to the availability of renewable energy.

13. The method according to any one of claims 1 to 12, further comprising the step of upgrading methanol to fuel-grade methanol.

14. The method according to any one of claims 1 to 12, further comprising the step of upgrading methanol to chemical-grade methanol.

15. The method according to any one of claims 1 to 14, further comprising the step of using at least a part of the methanol in step d) in an apparatus for the production of transport fuel.

16. The method according to any one of claims 1 to 13, wherein at least a part of the off-gas is recycled upstream of the reformer.

17. The method according to any one of claims 1 to 16, wherein 80% to 100% of the carbon of the biogas in the reformer feed stream is converted to methanol.

18. The amount of biogas in the reformer feed stream is 500 Nm ３ / h to 8000 Nm ３ / h, and the method according to any one of claims 1 to 17.

19. After step a) and before step c), a separation unit is used to remove a part of the CO in the reformer feed stream, the method according to any one of claims 1 to 18. ２ ​

20. The method according to any one of claims 1 to 19, wherein a part of the off-gas generated in step d) is recycled to a biogas production facility for generating biogas to be upgraded.

21. An apparatus for upgrading biogas to methanol, comprising: - Optionally, a gas purification unit; - Optionally, a pre-reforming unit; - A reforming reactor comprising a pressure shell containing a structured catalyst arranged to catalyze steam reforming of biogas, provided that the structured catalyst comprises a macrostructure of an electrically conductive material, the macrostructure carrying a ceramic coating, wherein the ceramic coating carries a catalytically active material; and the reforming reactor further comprises a power supply arranged outside the pressure shell and an electrical conductor connecting the power supply to the structured catalyst to pass an electric current through the electrically conductive material of the macrostructure, thereby heating at least a part of the structured catalyst to a temperature of at least 500 °C; - A methanol synthesis unit arranged to receive the synthesis gas from the reforming reactor and produce a product comprising methanol and off-gas. The apparatus as described above.

22. The apparatus according to claim 21, wherein the catalyst pellets are loaded on, around, inside or under the upper surface of the structured catalyst of the reforming reactor.

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