Methanol from biomass gasification

Abstract

A process (100) for the synthesis of methanol (1) comprising the steps of subjecting biomass (2) to a gasification process (6) in the presence of steam (5) and an oxidizing agent (48); subjecting the gasifier stream (7) thus obtained to a water gas shift conversion (10) and purification (14) to produce a synthesis gas (15) having hydrogen, carbon monoxide and CO2; mixing the synthesis gas (15) with a second synthesis gas stream (31) to produce a third synthesis gas stream (16); feeding the third synthesis gas stream (16) to a methanol synthesis loop (19) wherein crude methanol (20) and a tail gas (35) retaining methane are produced; subjecting the tail gas (35) to a reforming step (25) in the presence of an oxidizing agent (49) to generate the second synthesis gas stream (31).

Description

Technical Field

[0001] This invention pertains to the field of methanol production. In particular, it relates to a process and apparatus for synthesizing methanol. Background Technology

[0002] The gasification process involves the partial oxidation of carbonaceous feedstocks in the presence of a substoichiometric amount of an oxidant, such as oxygen or air. The product of gasification is syngas, which contains carbon monoxide, hydrogen, and small amounts of carbon dioxide, water, and methane, in addition to unburned or unoxidized solid residues.

[0003] In this field, there is growing interest in using syngas obtained from biomass gasification to produce biomethanol. Biomass gasification is a complex process that requires consideration of conflicting requirements, such as the need to avoid melting unburned residues and the need to keep the methane and carbon dioxide content in the syngas as low as possible.

[0004] Unburned residues must be prevented from melting to avoid the transfer of impurities (such as sulfur and alkali) into the syngas. These impurities can lead to deactivation of the methanol synthesis catalyst and corrosion problems in the unit. Conversely, methane formation must be limited because this gaseous product does not participate in methanol synthesis.

[0005] Traditional biomass gasification processes are typically carried out in the presence of oxygen and water vapor at relatively low temperatures (e.g., below 1000°C) and under medium to high pressures (typically between 30 and 100 bar).

[0006] Unfortunately, due to the operating conditions employed (i.e., low temperature and high pressure), the syngas obtained in the process retains a relatively high concentration of methane, for example, about 10-12% mol on a dry basis.

[0007] The large amount of methane retained in the syngas is a drawback because it reduces the productivity and efficiency of the plant, since the unconverted methane is not utilized in the process and is usually purged from the synthesis loop as tail gas and burned.

[0008] Another drawback of reducing the cost and energy efficiency of biomethanol processes involves the utilization and purification of the water generated during the process.

[0009] Specifically, methanol is obtained from the synthesis loop as a crude stream containing impurities (i.e., dissolved gases such as methane, higher alcohols, aldehydes, ketones, and water), and must be purified downstream of the synthesis loop to obtain a high-purity product. Purification typically takes place in a distillation section, where a high-purity methanol product is separated from the water stream contaminated with residual methanol and the stream containing the aforementioned impurities.

[0010] The water stream cannot be directly discharged into the environment; instead, it must be treated in a suitable unit (e.g., a scrubber) to reduce its CH3OH content. Clearly, this purification step increases the operating cost of the process and involves a waste of resources, as the resulting water stream is subsequently discharged from the device.

[0011] Therefore, given the above considerations, there is a great need to develop an energy-saving, economically feasible, and resource-efficient process and apparatus for the synthesis of methanol.

[0012] US 2014 / 0145819 discloses a mixing apparatus for producing liquid fuels from a stream containing hydrogen and carbon monoxide, the stream being generated by steam reforming of gasified solid carbonaceous feedstock and light fossil fuels. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art.

[0014] This invention is based on the insight that, in order to obtain a resource-efficient and energy-saving biomethanol process, all resources (i.e., methane and water flow) generated during synthesis are recycled in the process.

[0015] Therefore, one aspect of the present invention is a process for synthesizing methanol.

[0016] The process includes feeding the syngas effluent from biomass gasification and tail gas reforming into a methanol synthesis loop. In the methanol synthesis loop, a catalytic conversion of carbon oxides to methanol is performed under methanol synthesis conditions to obtain methanol products and a methane-rich tail gas, wherein the tail gas is partially recycled to a reformer for further conversion into syngas.

[0017] Another aspect of the invention is an apparatus for producing methanol.

[0018] The apparatus includes a front-end for generating a first syngas stream from biomass gasification, a methanol synthesis loop for generating crude methanol and methane-rich tail gas, and a tail gas treatment section including a reforming unit for converting the methane retained in the tail gas into a second syngas stream. The first syngas stream obtained from gasification and the second syngas stream obtained from reforming are mixed to form a third syngas stream fed into the methanol synthesis loop.

[0019] This invention provides an energy-efficient and economically viable alternative for the production of bio-methanol, because the methane synthesized as an unwanted byproduct during gasification can now be converted into a useful stream, namely a second synthesis gas stream, in a reformer. This second synthesis gas stream can then be converted into methanol to improve the plant's productivity.

[0020] Another advantage is that the water generated in the device can be effectively reused without requiring methanol purification. Yet another advantage is that, since the water inlet and outlet are balanced, meaning all water generated in the process is recycled, there is no water loss in the device. Detailed Implementation

[0021] The term biomass in this invention includes, but is not limited to, wood materials (bark, wood chips, scraps and sawdust), pulp and paper industry residues, agricultural residues, organic municipal materials, sewage, manure and food processing byproducts.

[0022] In the process of this invention, the biomass feedstock is fed into a gasification step in the presence of steam and an oxidant to generate a gasifier stream. The gasifier stream is then subjected to a water-gas shift conversion and a purification step to produce a first synthesis gas stream that retains hydrogen and carbon monoxide.

[0023] The obtained first syngas stream is then mixed with the second syngas stream to produce a third syngas stream. The second syngas stream is obtained by reforming the tail gas extracted from the methanol synthesis loop.

[0024] The third synthesis gas stream is then fed into the methanol synthesis loop, where a catalytic reaction occurs to form crude methanol. In the methanol loop, under methanol synthesis conditions, a catalytic conversion of carbon oxides to methanol takes place to produce crude methanol and a tail gas containing methane.

[0025] In the presence of an oxidant, tail gas extracted from the methanol synthesis loop is fed into the reforming step to generate the second synthesis gas stream, which is then mixed with the first synthesis gas stream obtained from the gasification unit.

[0026] According to a preferred embodiment, a series of pretreatments are performed before the biomass feed is introduced into the gasifier to improve gasification efficiency. Pretreatment may include drying, pyrolysis, and / or baking.

[0027] Gasification is carried out in the presence of water vapor to increase the hydrogen content in the syngas, and is conducted in the presence of an oxidant (preferably oxygen). Oxygen can be produced on-site via an air separation unit or a water electrolyzer. Preferably, the oxygen stream has a purity of more than 99% molar or, more preferably, more than 99.5% molar.

[0028] After gasification, the obtained syngas may have the following composition: hydrogen content (H2) of 55 to 65 mol, preferably equal to or about 61.1 mol; nitrogen content (N2) of 0.2 to 0.5 mol, preferably equal to or about 0.4 mol; carbon monoxide (CO) content of 22 to 28 mol, preferably equal to or about 25.6 mol; carbon dioxide (CO2) content of 2 to 4 mol, preferably equal to or about 3.4 mol; methane (CH4) content of 8 to 10 mol, preferably equal to or about 9.5 mol; and Ar content of 0.02 to 0.05 mol, preferably equal to or about 0.04 mol.

[0029] Methanol synthesis catalysts are typically sensitive to tar, particulate matter, sulfur, excess CO2, and other impurities such as sulfur. Therefore, a gas cleaning stage can be provided after the gasification step.

[0030] According to a particularly preferred embodiment, the gasifier stream leaving the gasification section can undergo water-gas conversion to adjust the H2 / CO ratio.

[0031] The gas leaving the water-gas shift conversion stage can undergo a cooling step before being conveyed to the CO2 removal stage. CO2 removal can be carried out using known processes and technologies, namely polyethylene glycol dimethyl ether (SELEXOL), low-temperature methanol washing (Rectisol), MEA, or MDEA chemical absorption.

[0032] According to the present invention, the tail gas leaving the methanol synthesis section is subjected to a reforming step, preferably under autothermal reforming conditions or under partial oxidation conditions in the presence of an oxidant. Preferably, the reforming step is carried out at a temperature of 1000 to 1500°C or 1000 to 1300°C.

[0033] Preferably, the concentration of inert gas in the synthesis circuit is less than 40% mol.

[0034] According to a particularly preferred embodiment, the tail gas reforming step includes pretreatment of the tail gas prior to the reforming reaction. Particularly preferably, prior to the reforming process, the tail gas extracted from the methanol synthesis loop is saturated with water to obtain a saturated stream. More preferably, the saturated stream is further contacted with water vapor to obtain a conditioned stream, and the conditioned stream is conveyed to the reforming step. Preferably, the conditioned stream is characterized in that the water vapor to carbon ratio (S / C) is between 1.0 and 2.0.

[0035] According to another particularly preferred embodiment, the crude methanol is subjected to a purification step to produce a methanol product, a first fusel oil stream, a second light hydrocarbon stream, and a recovered water stream.

[0036] Preferably, the recovered water stream is supplied to the saturation step. Advantageously, all contaminated water generated in the apparatus is recycled in this process, and no additional water treatment is required to purify the water. Furthermore, efficient use of resources is achieved.

[0037] Preferably, the conditioned stream obtained after mixing the saturated water stream with water vapor is further processed in a preheating stage to obtain a temperature-conditioned stream with a temperature ranging from 600°C to 750°C, or preferably equal to or about 650°C.

[0038] According to an embodiment of the present invention, another product of the methanol synthesis loop is a gas mixture of flash vapor and tail gas, and the preheating stage is carried out under direct combustion conditions and is performed by the combustion of the first fusel oil stream, the second light hydrocarbon stream and the gas mixture of flash vapor and tail gas.

[0039] The term fusel oil is used below to refer to a mixture of heavier compounds including water, higher alcohols, methanol, and alkanes. Conversely, the term light hydrocarbon is used to refer to gaseous products that are lighter than methanol.

[0040] According to another embodiment of the invention, the preheating stage is carried out in a conventional heat exchanger or an electric heater, and the temperature-regulated stream is mixed with the first fusel oil stream recovered from the purification step before being delivered to the reforming step.

[0041] According to a particularly interesting application of the invention, before being mixed with the first synthesis gas stream, the second synthesis gas stream obtained from the reforming process is sequentially subjected to a cooling step and a separation step to condense condensate with the recovered water stream generated in the purification step.

[0042] Preferably, the condensate is mixed with the recycled water stream from the purification step before exchanging heat with the second synthesis gas stream in the cooling step.

[0043] According to an embodiment, the cooling step includes a steam generation step, wherein a gas mixture of the second light hydrocarbon stream obtained from the purification section and the flash vapor and tail gas obtained from the methanol synthesis loop is combusted in the steam generation step to generate superheated steam. Preferably, the combustion conditions in the steam generation step are established by a combustion heater.

[0044] Alternatively, superheated steam can be generated in the steam generation step by burning a gas mixture of the first fusel oil stream, the second light hydrocarbon stream, and the flash vapor and tail gas.

[0045] Some embodiments of the present invention relate to the use of various purge streams in a methanol synthesis process. Typically, purge gas is extracted from the methanol synthesis loop to prevent the accumulation of inert gases, and this purge gas may be fed to a hydrogen recovery unit (HRU) after being washed with water to recover the hydrogen contained therein, thereby producing a recovered hydrogen stream and tail gas, referred to as HRU tail gas. The HRU tail gas may contain residual hydrogen and methane. Other purge streams from the methanol process may include flash vapor from one or more separators, light fractions from crude methanol distillation, and fusel oil. In some embodiments, at least a portion of the HRU tail gas is recycled as process gas to the reforming section. Other purge streams and optionally the remainder of the HRU tail gas may be recycled as fuel to a combustion heater.

[0046] In an interesting embodiment of the invention, the HRU exhaust gas provides most of the process feed for the reforming step, or more preferably, all of the process feed for the reforming step. In the latter case, a significant advantage of the invention is that no additional fossil fuel is required for the reforming step. In essence, the reforming step is performed in series with respect to the gasification step.

[0047] For example, according to an embodiment of the invention, since the process feed of the autothermal reformer is entirely provided by the tail gas removed from the methanol synthesis process fed into the gasifier, the autothermal reformer and the gasifier can be considered as operating in series.

[0048] Preferably, the HRU exhaust gas provides at least 80% or at least 90% or even more preferably 100% of the process feed for the reforming step.

[0049] Particularly preferably, the reforming step is carried out in an autothermal reformer, with the process feed entirely provided by methanol tail gas. In an alternative embodiment, the reforming step is carried out in a partial oxidation reactor.

[0050] HRU exhaust gas can be supplied to the reforming step after appropriate treatment. The treatment preferably includes saturation with water and may further include preheating.

[0051] According to another interesting feature of the invention, the reforming step includes preheating the process stream to be reformed in a combustion heater, and the fuel for the combustion heater is at least partially supplied by one or more of the aforementioned purge streams, possibly with a small portion of HRU exhaust gas.

[0052] Particularly preferably, the combustion heater is fueled by the purge stream and a portion of the makeup gas from the methanol synthesis circuit, the makeup gas serving as a conditioning fuel for reliable combustion control. More preferably, for safety reasons, a natural gas stream is used to supply the ignition burner of the combustion heater.

[0053] In a preferred embodiment, the reforming step is carried out in a self-heating reformer, and the process feed at the inlet of the self-heating reformer contains at least 20% molar methane on a dry basis, preferably equal to or about 50% molar methane on a dry basis.

[0054] In embodiments based on autothermal reforming, the reforming stage preferably includes an autothermal reformer as the sole catalytic reactor in the reforming stage.

[0055] According to the present invention, the apparatus includes a front end comprising a gasification section, a water-gas shift converter, and a CO2 removal section. The gasification section is configured to convert biomass feedstock into a gasifier stream in the presence of water vapor and an oxidant to produce a first synthesis gas stream that retains hydrogen, carbon monoxide, and residual CO2.

[0056] The device also includes a methanol synthesis circuit, a tail gas treatment section, and a pipeline equipped with a compression unit, which connects the upstream end of the methanol to the methanol synthesis circuit.

[0057] The methanol synthesis loop includes a methanol synthesis reactor configured to produce crude methanol and tail gas.

[0058] The exhaust gas treatment section connects the methanol synthesis circuit to the pipeline that connects the methanol front end and the methanol synthesis circuit.

[0059] The tail gas treatment section includes a water saturation tower connected to the methanol synthesis loop and configured to generate a saturated water flow; a preheating unit connected to the saturation tower; and a reforming unit fluidly connected to the preheating unit and configured to generate a second synthesis gas flow.

[0060] The device also includes pipelines connecting the reforming unit and the compression unit.

[0061] The apparatus may also include a pipeline configured to supply steam to the saturated water flow prior to the preheating unit, and a purification section connected to the methanol synthesis circuit.

[0062] Preferably, the purification section is a multi-tower distillation section and is configured to generate methanol product, a recovered water stream, a first fusel oil stream, and a second light hydrocarbon stream.

[0063] According to an embodiment, the device further includes a pipeline connecting the preheating unit and the purification section, wherein the preheating unit is a combustion heater and the reforming unit is an autothermal reformer.

[0064] Alternatively, the apparatus may also include a pipeline connecting the purification section to the reforming unit, wherein the reforming unit is a partial oxidation reactor.

[0065] Preferably, when the reforming unit is a partial oxidation reactor, the preheating unit is a conventional heat exchanger or an electric heater; conversely, when the reforming unit is an autothermal reformer, the preheating unit is an electric heater or a combustion heater.

[0066] According to different embodiments, when the preheating unit is a combustion heater, the latter can be combusted using the first fusel oil stream, the second light hydrocarbon stream, and the gas mixture of the flash vapor and the tail gas.

[0067] The apparatus preferably includes a cooling section, which includes a steam generation section, the steam generation section having a combustion heater disposed downstream of the reforming unit and in fluid communication with the methanol synthesis loop and the purification section.

[0068] The methanol synthesis loop preferably includes a methanol reactor equipped with a fixed bed that operates in a pressure range of 50 to 120 bar and a temperature range of 200 to 300°C. Attached Figure Description

[0069] Figure 1 A schematic process layout of a methanol plant according to a preferred embodiment of the present invention is shown.

[0070] Figure 2 This diagram illustrates the schematic process layout of a methanol plant according to an alternative embodiment of the present invention.

[0071] Figure 3 This diagram illustrates the process layout of a methanol plant according to another embodiment of the present invention.

[0072] Detailed Description of Preferred Embodiments

[0073] Figure 1 A methanol apparatus 100 for synthesizing methanol 1 is shown, which includes a front end 101, a methanol synthesis loop 19, a purification section 21, and a tail gas treatment section 102.

[0074] The methanol front end 101 includes a pretreatment section 3, a gasifier 6, a gas cleaning unit 8, a water-gas shift reactor 10, and a carbon dioxide (CO2) removal unit 14.

[0075] The tail gas treatment section 102 includes a water-saturated tower 36, a preheating unit, and a reforming unit connected to the methanol synthesis loop 19. Figure 1 In this embodiment, the preheating unit includes a combustion heater 23, and the reforming unit includes a self-heating reformer 25. The gas processing section 102 also includes a cooling section 50 and a condenser 30.

[0076] Air separation unit 47 provides oxygen-containing streams 48 and 49 to vaporizer 6 and self-heating reformer 25.

[0077] The methanol synthesis circuit 19 and the purification section 21 are respectively equipped with a methanol synthesis reactor and a distillation unit (not shown). The methanol synthesis circuit 19 and the purification section 21 are interconnected by a pipeline 51 that transports crude methanol stream 20.

[0078] Now refer to Figure 1 The methanol synthesis process is described below. Biomass feedstock 2 is fed into pretreatment section 3, where the moisture content of feedstock 2 is reduced to a suitable level to produce dry biomass 4.

[0079] In the presence of water vapor 5 and oxygen 48, dried biomass 4 is fed into gasifier 6 to produce gasifier stream 7. Gasifier stream 7 is then conveyed to gas cleaning unit 8, where impurities (e.g., sulfur and alkali) are removed to generate purified gas 9; purified gas 9 is then fed into water-gas shift reactor 10, where the S / C ratio of purified gas 9 is adjusted to a value suitable for methanol synthesis to produce regulated makeup gas 13.

[0080] The regulated make-up gas 13 is then processed in CO2 removal unit 14. The product of CO2 removal unit 14 is a first syngas stream 15, which is mixed with a second syngas stream 31 extracted from condenser 30 to produce a third syngas stream 16. The third syngas stream 16 is suitable for conversion in the methanol synthesis loop to form the methanol make-up gas.

[0081] Methanol make-up gas 16 is fed to the suction section of compressor 17 to generate compressed make-up gas 18, which is then fed into methanol synthesis loop 19.

[0082] In methanol synthesis loop 19, crude methanol 20 is synthesized under methanol synthesis conditions. Other effluents of methanol synthesis loop 19 are tail gas 35 and a gas mixture 34 of flash vapor and tail gas. Both tail gas 35 and gas mixture 34 are methane-containing gas streams. Tail gas 34 and 35 in the pipeline can be taken from a hydrogen recovery unit, which processes the purge gas removed from the methanol synthesis loop.

[0083] The crude methanol 20 is then fed to the purification / distillation section 21 to produce pure methanol product 1, recovered water stream 33, first fusel oil stream 40, and second light hydrocarbon stream 41.

[0084] The exhaust gas 35 is supplied to a saturation tower 36, where it is saturated with hot water 43 to produce a saturated flow 37.

[0085] The saturated stream 37 is then contacted with steam 38 to generate a conditioned stream 39, which is preheated in a combustion heater 23 and then fed into the self-heating reformer 25. The stream 39 represents the total feed to the self-heating reformer 25.

[0086] The combustion heater 23 is combusted with the gas mixture 34 of flash vapor and exhaust gas, the first fusel oil stream 40, and the second light hydrocarbon stream 41. The effluent of the combustion heater 23 is a temperature-controlled stream 24, which is then conveyed to the self-heating reformer 25.

[0087] The product of the self-heating reformer 25 is reformed gas 26, which is fed sequentially into the cooling section 50 and the condenser 30 to produce condensate 32 and the second synthesis gas stream 31.

[0088] As described above, the second synthesis gas stream 31 is then mixed with the first synthesis gas stream 15 from the CO2 removal unit 14.

[0089] Cooling section 50 includes steam generation section 27 and one or more heat exchangers 28. Recycled water stream 33 from purification section 21 is supplied to heat exchanger 28 to exchange heat with cooling gas effluent 53 from steam generation section 27. Heat exchanger 28 generates hot water stream 43 which is delivered to saturation tower 36; cooling gas stream 29 effluent from heat exchanger 28 is fed to condensation section 30.

[0090] As can be clearly seen from the above embodiments, all resources generated in this process, namely the tail gas 35 and the recovered water stream 33, are recycled within the process. To avoid the accumulation of impurities present in the distilled water, a purge stream can be discharged from the bottom of the saturation tower.

[0091] Advantageously, due to the above configuration, the applicant has found that methanol production can be increased by about 30% compared to conventional biomethanol processes, wherein the tail gas 35 and the recovered water stream 33 are no longer recycled in conventional biomethanol processes.

[0092] Furthermore, the carbon efficiency, calculated as the number of moles of pure CH3OH in crude CH3OH divided by the number of moles of (CO + CO2 + CH4) in the supplementary gas, increased from 72% to 93%.

[0093] Figure 2 A methanol apparatus 100 according to an alternative embodiment of the present invention is shown. This embodiment is similar to... Figure 1 The difference is that it uses a partial oxidation reactor (POX reactor) 125.

[0094] The first synthesis gas stream 15 is synthesized according to the aforementioned steps. Here, the first synthesis gas stream 15 is mixed with the second synthesis gas stream 31 and compressed in the compressor 17 to produce compressed gas 18, which is then fed into the methanol synthesis loop 19.

[0095] The effluents of the methanol synthesis loop are a gas mixture 34 of flash vapor and tail gas, crude methanol stream 20, and tail gas 35. Crude methanol stream 20 is fed into purification section 21 to produce methanol product 1, recovered water stream 33, first fusel oil stream 40, and second light hydrocarbon stream 41.

[0096] As in the embodiments described above, exhaust gas is supplied to saturation tower 36 to produce saturated gas 37, which is then mixed with water vapor 38 to produce conditioned stream 39.

[0097] The conditioned stream 39 is then fed to a preheating unit 23, which in this embodiment is represented by a conventional heat exchanger or electric heater, to ultimately produce a temperature-conditioned stream 24.

[0098] The temperature-controlled stream 24 is then mixed with the first fusel oil stream 40 to produce a gaseous product 55, which is then sequentially fed to the partial oxidation reactor 125.

[0099] The product of partial oxidation is reformed gas 26, which is then processed in a cooling step 50. The cooling step includes a steam generation section 27 and a heat exchanger 28. The steam generation section includes a combustion heater (not shown) that is combusted with fuel gas 44, which is obtained by mixing the second light hydrocarbon stream 41 with a gas mixture 34 of the flash vapor and tail gas.

[0100] As in the previously described embodiment, the recovered water stream 33 effluent from the purification section 21 is supplied to the heat exchanger 28 to indirectly exchange heat with the gas effluent 53 from the steam generation section 27.

[0101] The effluents of heat exchanger 28 are hot water stream 43 and cooling stream 29. Hot water stream 43 is fed to saturation tower 36, while cooling stream 29 is fed to syngas cleaning and condensation section 30.

[0102] The effluent from the condensation section 30 is condensate 32 and the second synthesis gas stream 31. The condensate 32 is mixed with the recovered water stream 33 and then passed through a heat exchanger 28 to generate hot water 43, which is then supplied to the saturation tower 36.

[0103] Figure 3An embodiment in which the steam generation section 27 includes a combustion heater that uses a gas mixture 34 of flash steam and tail gas, as well as a first fusel oil stream 40 and a second light hydrocarbon stream 41 for combustion.

[0104] In a further embodiment of the invention, the preheating unit 23, which supplies regulated flow 39, may be an electric heater.

Claims

1. A process (100) for synthesizing methanol (1), comprising the following steps: a) The biomass feedstock (2) is gasified in the presence of steam (5) and oxidant (48) to generate gasifier stream (7); b) The gasifier stream (7) is subjected to a water-gas shift conversion and purification step to produce a first syngas stream (15) that retains hydrogen, carbon monoxide and CO2. c) The first synthesis gas stream (15) is mixed with the second synthesis gas stream (31) to produce a third synthesis gas stream (16). d) The third synthesis gas stream (16) is fed into the methanol synthesis loop (19), wherein the catalytic conversion of carbon oxides to methanol is carried out under methanol synthesis conditions to obtain crude methanol (20) and tail gas (35) with methane retained. e) The tail gas (35) is reformed in the presence of an oxidant (49) to generate the second syngas flow (31) of step c). The tail gas (35) obtained in step d) is saturated with water (43) to obtain a saturated stream (37), and the crude methanol (20) obtained in step d) is further purified to produce methanol (1) product, a first fusel oil stream (40), a second light hydrocarbon stream (41) and a recovered water stream (33), wherein the recovered water stream (33) is supplied to the saturation step.

2. The process according to claim 1, wherein the reforming step in step e) is carried out under autothermal reforming conditions or under partial oxidation conditions.

3. The process according to claim 1, wherein at least one of the oxidant (48) in step a) and the oxidant (49) in step e) is an oxygen stream with a purity higher than 99% molar.

4. The process according to claim 1, wherein at least one of the oxidant (48) in step a) and the oxidant (49) in step e) is an oxygen stream with a purity higher than 99.5% molar.

5. The process according to claim 1, wherein step e) comprises saturating the tail gas (35) obtained in step d) with water (43) to obtain a saturated stream (37), further contacting the saturated stream (37) with water vapor (38) to obtain a conditioned stream (39), and subjecting the conditioned stream (39) to the reforming step.

6. The process according to claim 5, wherein the regulated stream (39) has a water vapor to carbon ratio S / C between 1.0 and 2.

0.

7. The process according to claim 5, wherein the conditioned stream (39) is preheated in a preheating stage before being fed to the reforming step to obtain a temperature-conditioned stream (24) with a temperature in the range of 600 to 750°C.

8. The process according to claim 5, wherein the conditioned stream (39) is preheated in a preheating stage before being fed to the reforming step to obtain a temperature-conditioned stream (24) at a temperature of 650°C.

9. The process according to claim 7, wherein another product of the methanol synthesis loop (19) is a gas mixture (34) of flash vapor and tail gas, and the preheating stage is carried out under direct combustion conditions and is combusted by the first fusel oil stream (40), the second light hydrocarbon stream (41) and the gas mixture (34) of flash vapor and tail gas.

10. The process according to claim 7, wherein the temperature-controlled stream (24) is mixed with the first fusel oil stream (40) recovered from the purification step before being delivered to the reforming step.

11. The process according to claim 9, wherein the second synthesis gas stream (31) in step c) is subjected to a cooling step and a separation step to condense condensate (32) by sequentially cooling the recovered water stream (33) generated in the purification step before being mixed with the first synthesis gas stream (15).

12. The process according to claim 11, wherein the condensate (32) is mixed with the recovered water stream (33) from the purification step before exchanging heat with the second synthesis gas stream (31) in the cooling step.

13. The process according to claim 11, wherein the cooling step includes a steam generation step, wherein the gas mixture (34) of the flash vapor and the tail gas, and the second light hydrocarbon stream (41) are burned in the steam generation step to generate superheated steam.

14. The process according to claim 11, wherein the cooling step includes a steam generation step, wherein the gas mixture (34) of the flash vapor and tail gas, the second light hydrocarbon stream (41) and the first fusel oil stream (40) are combusted in the steam generation step to generate superheated steam.

15. The process according to claim 1, wherein the exhaust gas (35) provides most or all of the process feed for the reforming step.

16. The process of claim 1, wherein the reforming step comprises preheating the process stream to be reformed in a combustion heater, and the fuel of the combustion heater comprises one or more purge streams obtained from crude methanol synthesis and / or purge streams obtained from the purification of crude methanol.

17. The process according to claim 16, wherein the fuel for the combustion heater comprises one or more of the following: a portion of the exhaust gas (35); a portion of the third synthesis gas stream (16) of step d); and a natural gas stream.

18. The process of claim 1, wherein the reforming step is carried out in an autothermal reformer, and the process feed at the inlet of the autothermal reformer comprises at least 20% molar methane on a dry basis.

19. The process of claim 1, wherein the reforming step is carried out in an autothermal reformer, and the process feed at the inlet of the autothermal reformer comprises 50% molar methane on a dry basis.

20. An apparatus for producing methanol (1), comprising: a) Front end (101), which includes a gasification section (6), a water-gas conversion converter (10) and a CO2 removal section (14), wherein the gasification section (6) is configured to convert biomass feedstock (2) into a gasifier stream (7) in the presence of steam (5) and an oxidant (48) to produce a first syngas stream (15) that retains hydrogen, carbon monoxide and CO2. b) A methanol synthesis loop (19) comprising a methanol synthesis reactor configured to produce crude methanol (20) and tail gas (35). c) A pipeline with a compression unit (17) connected to the front end (101) of the methanol and the methanol synthesis circuit (19). d) A tail gas treatment section (102) connecting the methanol synthesis circuit (19) to the pipeline connecting the methanol front end (101) and the methanol synthesis circuit (19), wherein the tail gas treatment section (102) includes: • A water-saturated tower (36) is arranged downstream of the methanol synthesis loop (19) and configured to generate a saturated stream (37). • A preheating unit (23) connected to the saturation tower (36); • A reforming unit (25) is connected to the preheating unit (23) and configured to generate a second synthesis gas flow (31); • Piping connecting the reforming unit (25) and the compression unit (17), The apparatus further includes a purification section (21) connected to the methanol synthesis circuit (19), the purification section (21) being a multi-tower distillation section and configured to generate methanol (1) product, a recovered water stream (33), a first fusel oil stream (40), and a second light hydrocarbon stream (41).

21. The apparatus of claim 20, further comprising: A pipeline configured to supply steam (38) to the saturated flow (37) before the preheating unit (23).

22. The apparatus of claim 21, further comprising: The pipeline connects the preheating unit (23) and the purification section (21), and the preheating unit (23) is a combustion heater, and the reforming unit (25) is a self-heating reformer. or The pipeline connects the purification section (21) to the reforming unit (25), and the reforming unit is a partial oxidation reactor.

23. The apparatus according to claim 21, further comprising a cooling section (50) including a steam generation section (27) having a combustion heater disposed downstream of the reforming unit (25) and in fluid communication with the methanol synthesis circuit (19) and the purification section (21).

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