Process for the production of hydrogen from biomass

Abstract

The invention relates to a process for the production of hydrogen from biomass (1). For this purpose, the biomass (1) is fed into a fluidized-bed reactor (2) in which the biomass is converted to a material flow (3). Solids (25) are separated in at least one cyclone (12, 13). Further solids (50) and hydrocarbons (36) are separated in a Venturi washer (14). In the biodiesel wash (15), a material flow (6) is produced which is fed to a water wash (16) and then to a separation in a cooling unit (17). In the gas fine purification (18), a material flow (9) is generated which is fed to a water gas conversion (19) and a CO2 removal. A material flow (11) is generated in the gas separation (20).

Description

[0001] Process for producing hydrogen from biomass

[0002] Description

[0003] The invention relates to a process for producing hydrogen from biomass.

[0004] Hydrogen is an energy-rich gas that can be used, for example, in fuel cells to generate electricity, as a fuel in combustion engines, or as a feedstock in the chemical industry.

[0005] As an energy carrier, hydrogen is not a primary energy source; it must be produced from primary energy sources. So-called "green hydrogen" as an energy source produces no carbon dioxide when produced using renewable energies such as wind or solar energy. "Biohydrogen" also produces no carbon dioxide in its net balance. Currently, however, hydrogen production is largely based on fossil primary energy sources, primarily through natural gas reforming.

[0006] The currently favored method of producing energy through water electrolysis using surplus renewable electricity, known as "power-to-gas," is considered relatively inefficient and economically uncompetitive with natural gas reforming, with practically realized efficiencies barely exceeding 60%, because sufficiently cheap surplus electricity can actually only be used for a few hours a year.

[0007] Biohydrogen is hydrogen produced from biomass or from living biomass. Hydrogen can be obtained from synthesis gas, which is produced by gasifying biomass.

[0008] Synthesis gas is a gas mixture composed primarily of carbon monoxide and hydrogen, which can be used to synthesize other chemical products. The production of synthesis gas from waste materials from the iron and petrochemical industries is generally known. However, there is also a growing need to produce synthesis gas from biological input materials, especially since these contain a sufficiently high proportion of carbonaceous and hydrogen-containing components due to their organic structure.

[0009] The raw materials considered for biomass gasification are primarily lignocellulose-rich agricultural raw materials, as well as forest residues, residual wood from processing, waste wood, but also sewage sludge and green waste such as kitchen and garden waste, lawn clippings, leaves, shrub and tree cuttings, as well as processed household waste or "brown" bins.

[0010] The gasification of biomass preferably takes place in a fluidized-bed reactor. In such a heated fluidized-bed reactor, a gaseous fluid flows through a bed of solids, primarily sand but also other mineral solids such as corundum, forming a fluidized bed in the form of a fluid-solid suspension. The biological material present is continuously introduced into this fluidized bed, releasing primarily synthesis gas. Such a fluidized-bed reactor is disclosed, for example, in EP 2 705 121 B1.

[0011] However, biomass gasification also releases tar-like substances, aromatic hydrocarbons, and unconverted residual carbon (soot), which can severely impair subsequent process steps and plant components used to process hydrogen. Unless these substances are directly removed from the synthesis gas stream, they lead to rapid disruption of downstream plant components.

[0012] For the tarry components and substances, it has proven useful to consider naphthalene as a representative substance and to consider the purification of the synthesis gas stream based on this. DE 10 2014 221 952 A1 discloses a process for treating coke oven gas in which naphthalene is scrubbed from the compressed coke oven gas with a suitable liquid in a scrubber, thereby reducing the residual amount of naphthalene remaining in the coke oven gas. This allows the subsequent treatment steps, in particular the scrubbing steps, to be carried out at lower temperatures without causing naphthalene to condense out. As a result of the lower temperature, the efficiency of the scrubbing steps is significantly improved.

[0013] However, under unfavorable operating conditions, naphthalene rapidly sublimates during the washing step, causing the system component and subsequent components to rapidly become clogged. This leads to a plant shutdown and requires laborious removal of the clogged components and intensive cleaning of the system components.

[0014] An alternative is catalytic oxidation, as described, for example, in DE 10 2007 025 420 B4. The process for the selective removal of tar substances in synthesis gases using transition metal oxides as transition metal oxide catalysts for the selective oxidation of tar substances in synthesis gases discloses a transition metal oxide catalyst containing vanadium oxide.

[0015] The described processes lead to a significant reduction of naphthalene and tar-like substances in the material stream. However, complete removal cannot be achieved, which can lead to gradual clogging of the plant components. Economical operation with recurring shutdowns for cleaning processes is difficult to achieve.

[0016] In addition, tar-like substances, aromatic hydrocarbons, and soot deactivate the catalyst in water-gas conversion, which is useful for increasing hydrogen yield, at an unfavorable rate, even at very low concentrations. The yield of gas separation reacts extremely sensitively to these substances. Even the smallest amounts of these substances entering the gas separation process make the separation of hydrogen from the synthesis gas uneconomical. Thus, both water-gas conversion and gas separation require an extremely pure and clean gas stream.

[0017] The object of the present invention is to provide a process for producing hydrogen from biomass that ensures the removal of soot, aromatic hydrocarbons, and tar-like substances from the material stream. The described problems caused by tar-like substances, aromatic hydrocarbons, and soot should be reliably avoided by the process. Furthermore, the required purity and cleanliness of the material stream for water-gas conversion and gas separation should be reliably achieved. Furthermore, the process should exhibit a high hydrogen yield and be suitable for continuous operation.

[0018] This object is achieved according to the invention by a process for producing hydrogen from biomass, as well as a device and a use according to the independent main claims. Preferred variants can be found in the dependent claims, the description, and the drawings themselves.

[0019] Accordingly, the process for producing hydrogen from biomass is intended to include the following steps:

[0020] According to the invention, biomass is fed into a fluidized bed reactor.

[0021] In a particularly advantageous variant of the process, input materials such as grasses, residual wood, landscaping material, and even sewage sludge can be directly processed and introduced into the fluidized bed reactor as additional biomass to produce synthesis gas.

[0022] In a particularly advantageous variant of the process, the plant network also includes a reception point and a storage area for biomass, such as grasses, residual wood and landscape maintenance material.

[0023] A prerequisite for incorporation into the fluidized bed reactor is the processing of fermentation residues, green waste, garden and agricultural waste, and sewage sludge. For this purpose, the biomass is preferably dried and / or pressed to achieve a water content of less than 20%.

[0024] Preferably, the biomass prepared by drying and pressing is packaged in the form of compacted pellets.

[0025] Ideally, the pellets can be introduced into the fluidized bed reactor using a screw conveyor.

[0026] In an advantageous variant of the invention, fermentation residues from biogas plants can also be pressed for this purpose. This can preferably be done using a belt filter press, a frame filter press, a chamber filter press, or a screw press.

[0027] According to the invention, the biomass is converted into a material stream in the fluidized bed reactor, in particular thermally converted.

[0028] According to a further development of the method, at least one heating device is provided for heating and continuously maintaining the thermal conversion at the selected process parameters of the fluidized bed reactor, which heating device has a burner for generating heat.

[0029] Advantageously, the burner can be operated with a fuel gas that at least partially contains biogas produced in the biogas plant as a component. Such biogas typically has a high methane content, ranging between 50 and 60 vol. Other components can include water vapor, oxygen, nitrogen, ammonia, hydrogen, and hydrogen sulfide. Due to the high methane content, biogas can also be used as a fuel gas, which has a beneficial effect on the carbon dioxide balance of the hydrogen production process.

[0030] In principle, the fuel gas can also contain other components. These additional components can be, for example, natural gas or a portion of the synthesis gas produced in the fluidized-bed reactor. The fuel gas is then combusted through oxidation, and the resulting heat is used to heat the fluidized-bed reactor. At least one heating device is designed to achieve an operating temperature of the reactor between 600 and 1000 °C.

[0031] Furthermore, it is also possible to provide at least two heating devices on the fluidized bed reactor. These can then create different temperature zones on the fluidized bed reactor in different housing sections. Based on such a configuration, at least a first gasification zone can be operated at a gasification temperature between 600 and 770 °C, preferably between 700 and 770 °C. A second gasification zone with a second gasification temperature preferably has a temperature between 770 and 1000 °C, preferably between 770 and 900 °C. In a particularly preferred variant of the process, additional fluidized bed material can be used to support the thermochemical conversion reactions. This fluidized bed material can preferably be in the form of a specific mineral sand (e.g., dolomite, etc.).

[0032] In addition, at least one heating device preferably heats the fluidized bed reactor in an allothermal manner. This means that the process engineering processes in the fluidized bed are initiated solely by the external influence of heat, but without causing chemical changes. For this purpose, the heat generated in the burner must be supplied to the fluidized bed reactor without the hot exhaust gases from the burner entering the fluidized bed reactor in a material sense. This can be achieved, for example, by having the hot exhaust gases act on the fluidized bed in the form of a heat exchanger. In addition, baffles can also be provided, via which the surface acting on the fluidized bed is increased.

[0033] Biomass is used as a reactant for syngas production. Heating to the first gasification temperature and heating to the second gasification temperature both involve active heating, i.e., heating is independent of any reaction heat generated during the production process. Alternatively or additionally, the first fluidized bed zone and / or the second fluidized bed zone can be heated by supplying an oxygen-containing gas, by supplying a syngas, and / or by supplying steam. The fluidized bed itself is divided into two temperature zones, i.e., two fluidized bed zones. The first, lower fluidized bed zone is heated to the first gasification temperature, and the second, higher fluidized bed zone is heated to the higher second gasification temperature.Both the pyrolysis step and the conversion of the remaining, lighter particles and the homogeneous gas phase reactions for the conversion of the initially generated pyrolysis gases can then take place within the fluidized bed.

[0034] Ideally, pure oxygen is also supplied to the fluidized-bed reactor in addition to steam. This advantageously results in an allothermal energy input during the gasification of biomass, in addition to the allothermal core device. This also increases hydrogen production and simultaneously reduces tar formation.

[0035] The advantageous design of biomass gasification in a fluidized-bed reactor results in a carbon conversion of approximately 95%. The remaining, unreacted residues, such as soot, aromatic hydrocarbons, and tar-like substances, leave the fluidized-bed reactor with the synthesis gas and must be separated from the synthesis gas using the complex purification process according to the invention.

[0036] According to the invention, solids are separated in at least one cyclone following the fluidized bed reactor.

[0037] Ideally, the separation of solids from the synthesis gas stream takes place in two cyclones.

[0038] In a preferred variant of the invention, the solids are separated from the synthesis gas stream in a first cyclone and a second cyclone above the tar dew point.

[0039] Preferably, the first cyclone is operated at 800 °C and the second cyclone at 400 °C.

[0040] The first cyclone is preferably used to separate coarse solids from the synthesis gas stream. The second cyclone is preferably operated at 350 to 400 °C and is used to separate the remaining, somewhat finer solids that could not be completely separated in the first cyclone due to the higher temperature.

[0041] Ideally, a steam generator can be operated between the cyclones to utilize the waste heat from the process to cool the material flow.

[0042] Preferably, a steam generator is operated between the first cyclone and the second cyclone to generate a saturated steam flow with a steam pressure of greater than 25 bar, preferably greater than 30 bar.

[0043] In a particularly advantageous variant of the process, the waste heat from the fluidized bed reactor is captured between the cyclones in the form of a steam stream and used to dry the biomass. This can be done, for example, in a belt dryer.

[0044] Ideally, the steam can be superheated in a downstream steam superheater, in which the separated solids and washed-out hydrocarbons as well as tail gas are burned, before it is introduced into the fluidized bed reactor with the addition of oxygen.

[0045] According to the invention, the remaining solids are further removed in a Venturi scrubber. For this purpose, in the process for producing hydrogen from biomass, a Venturi scrubber is arranged downstream of at least one cyclone, which scrubs the solids remaining after the cyclone from the gas stream. In an alternative variant of the invention, two Venturi scrubbers are arranged in series. This significantly increases the removal of solids such as soot, but also tar-like substances.

[0046] In a favorable embodiment of the process according to the invention, the Venturi scrubber is operated as an adiabatic saturator. Thus, the scrubbing process takes place without external cooling or heating. The material stream is loaded with water vapor up to the saturation point.

[0047] Ideally, the venturi scrubber is operated at a temperature of more than 75 °C, preferably more than 79 °C, in particular more than 82 °C and / or at a temperature of less than 100 °C, preferably less than 95 °C, in particular less than 90 °C.

[0048] The Venturi scrubber is preferably operated above the sublimation conditions of naphthalene, a proxy substance for aromatic hydrocarbons. This ensures trouble-free operation of the scrubber without the risk of clogging.

[0049] The Venturi scrubber preferably flows into a settling tank, where the various phases separate. The synthesis gas stream is fed to the biodiesel scrubber. The scrub water collects in a settling tank, which contains a dividing wall or weir. The phases separate with increasing residence time in the settling tank. The higher hydrocarbons and tars float on top of the water and flow over the dividing wall into a second section of the settling tank.

[0050] The higher hydrocarbons and tars can be drained off for further energy recovery depending on the fill level. In an advantageous variant, the settling tank is made of glass for interface visualization.

[0051] The water in the first part of the settling tank is recirculated through at least one filter and then returned to the Venturi scrubber, creating a closed water cycle.

[0052] According to the invention, a biodiesel scrubber is operated to generate a material stream.

[0053] Preferably, the material stream from the Venturi scrubber is fed into a scrubbing column. The scrubbing column is preferably operated countercurrently with a scrubbing oil. This scrubbing oil is ideally a biodiesel and / or tar-based scrubbing oil.

[0054] In a particularly preferred variant of the invention, the wash oil is a biodiesel whose main component is fatty acid methyl ester (FAME). Such a biodiesel can be obtained by transesterification of vegetable oils. Compared to fossil wash oils, biodiesel contains virtually no sulfur and, in addition, a negligible amount of other pollutants.

[0055] Biodiesel is obtained from vegetable oils. Typical starting materials, depending on local conditions, include rapeseed, palm, sunflower, and soybean oil, from which the corresponding methyl esters are formed. For the purposes of the invention, rapeseed oil methyl ester (RME) is particularly suitable, as it can be produced in large quantities in regions with a temperate climate and is commercially available.

[0056] Biodiesel is characterized by its excellent absorption capacity, particularly for scrubbing to remove aromatic hydrocarbons, tar-like substances, and naphthalene as a substitute substance. The synthesis gas, as a material stream, leaving the Venturi scrubber is brought into contact with the biodiesel in a gas scrubber, where the aromatic hydrocarbons, tar-like substances, and naphthalene are absorbed into the biodiesel. The biodiesel is conveniently added at the top of the scrubber and flows through the scrubber in countercurrent to the synthesis gas. The biodiesel, enriched with the aromatic hydrocarbons, tar-like substances, and naphthalene, is withdrawn from a lower section of the scrubber and fed to a settling tank.

[0057] A favorable design for biodiesel scrubbing results in the absorption of at least 50%, preferably at least 65%, and especially 80%, of the naphthalene or aromatic and higher hydrocarbons in the biodiesel. This effectively prevents clogging of downstream plant components due to sublimation of naphthalene and similar substances.

[0058] Ideally, the biodiesel scrubbing is carried out at a temperature of more than 75 °C, preferably more than 79 °C, in particular more than 82 °C, and / or at a temperature of less than 100 °C, preferably less than 95 °C, in particular less than 90 °C. Advantageously, the scrubbing takes place above the sublimation conditions of naphthalene, whereby a settling of the scrubbing can be advantageously avoided and the process can be carried out in continuous operation.

[0059] In an advantageous variant of the invention, the biodiesel scrubber is operated at a pressure of more than 1 bar, preferably more than 3 bar, in particular more than 5 bar, and / or at a pressure of less than 11 bar, preferably less than 9 bar, in particular less than 7 bar. The loaded biodiesel is preferably fed into a settling tank. Aromatic hydrocarbons and tar-like substances may settle. The biodiesel flowing over a partition is fed back to the biodiesel scrubber via a filter.

[0060] Surprisingly, it was discovered that biodiesel can be easily regenerated by stripping with superheated steam after absorbing aromatic hydrocarbons and tar-like substances at high temperatures, especially above 150 °C. Unlike fossil diesel oils, this process does not result in the precipitation of sticky, rubbery substances. Furthermore, the biodiesel is largely biodegradable and has an improved carbon dioxide (CO2) balance.

[0061] The composition and chemical and physical properties of biodiesel are described, for example, in the standards DIN EN 14214 and ASTM D 6751-07A. These standards refer to the use of biodiesel as a fuel. Therefore, in addition to the standardized types of biodiesel, variants of biodiesel can be used as a scrubbing fluid for the absorption of aromatic hydrocarbons, which may deviate to some extent from the aforementioned standards.

[0062] According to the invention, a water wash is operated to generate a material flow.

[0063] Ideally, after the biodiesel scrub, the synthesis gas stream is fed to a water scrubber in a scrubbing column. The synthesis gas flows countercurrently to the scrubbing water, with the scrubbing water preferably being sprayed via a distributor device at the top of the column. In an advantageous variant of the invention, the water scrubber is operated as a direct cooling system and cools the stream to more than 40°C, preferably to more than 45°C, in particular to more than 50°C, and / or to less than 70°C, preferably to less than 65°C, in particular to less than 60°C.

[0064] Preferably, the water for operating the scrubbing column is circulated in a water circuit. For this purpose, the loaded scrubbing water is fed into a settling tank for phase separation. After phase separation, the water is returned to the scrubbing column via a filter and cooler. The cooler allows the scrubbing water to be precisely controlled to cool the synthesis gas stream without falling below the sublimation temperature of naphthalene and other aromatic or higher hydrocarbons.

[0065] In a particularly advantageous variant of the invention, the naphthalene content in the synthesis gas stream can be determined. This can be done, for example, using a gas chromatograph. In this way, the wash water temperature can be safely set above the sublimation conditions of naphthalene, while simultaneously achieving maximum cooling of the synthesis gas stream without risking the disruption of downstream plant components.

[0066] At the same time, the steam added to the synthesis gas stream through the Venturi scrubber is condensed in the scrubbing column. This advantageously supports the removal of tar-like substances and naphthalene as a substitute substance. After settling in the settling tank and a filtering process, the water is returned to the Venturi scrubber.

[0067] The described scrubbing of the synthesis gas stream is always carried out above sublimation conditions, depending on the naphthalene loading. This effectively counteracts sublimation and thus clogging of the plant components, while simultaneously producing the purest possible gas stream for hydrogen recovery in the gas separation. The more efficiently the biodiesel scrubbing reduces the naphthalene loading of the synthesis gas stream, the cooler the subsequent water scrubbing can be operated.

[0068] Advantageously, the water wash is carried out above the sublimation conditions of naphthalene. The sublimation of naphthalene depends on the temperature, pressure, and partial pressure of the naphthalene.

[0069] The loaded wash water from the water scrubber is preferably directed into a settling tank equipped with a weir. The quiescent state in the settling tank promotes phase separation. The higher hydrocarbons and naphthalene float to the top of the water and are separated by the weir.

[0070] In a particularly advantageous variant, the wash water is circulated between the Venturi scrubber and the water scrubber. The washed-out soot, aromatic hydrocarbons, and tarry substances are removed in the settling tanks via a dividing wall. The finely dissolved substances are removed from the wash water via filters located downstream of the settling tanks. This closed water circuit advantageously supports the sustainability of the process.

[0071] According to the invention, the precipitable residues remaining in the material flow are separated in a cooling unit to generate a material flow.

[0072] Advantageously, aromatic hydrocarbons, tarry substances, and naphthalene are separated in the cooling unit at a temperature of less than 15 °C, preferably less than 10 °C, in particular less than 5 °C. The separated substances are collected in a separation tank and fed for further energy recovery.

[0073] In a favorable variant of the invention, the settling tanks can be sludged. The soot, tar-like substances, and aromatic hydrocarbons, along with the cyclone deposits, are then sent for energy recovery, such as combustion. This can preferably be done in the heating device of the fluidized-bed reactor and / or in a steam generator. This ensures that all carbonaceous components introduced into the plant are fully utilized for energy recovery.

[0074] Comprehensive and holistic purification using three washes and cool precipitation ensures the safe operation of the process and plant network for producing hydrogen from biomass. Ideally, this also removes a large portion of substances and compounds that can act as catalyst poisons in gas separation, such as sulfur, chlorine, HCN, etc.

[0075] The purified synthesis gas is compressed to the pressure required for gas separation in several compressor stages. For example, radial compressors and / or screw or piston compressors can be used.

[0076] In a favorable variant of the invention, three compressors are connected in series, wherein the synthesis gas is compressed to a pressure of more than 12 bar, preferably more than 15 bar, in particular more than 18 bar.

[0077] According to the invention, the compressed synthesis gas stream is fed to a fine gas purification process. Ideally, in a first step of the fine gas purification process, the remaining sulfur components are adsorbed in a zinc oxide bed.

[0078] In an advantageous variant, the gas fine purification comprises several beds with different packings for the adsorption of trace substances, which can be unfavorable for gas separation.

[0079] According to the invention, the water-gas conversion is operated to generate a material stream. In this process, the CO in the synthesis gas stream is converted into CO2 and H2 with the addition of steam.

[0080] The water gas conversion reaction is an exothermic equilibrium reaction and can be optimized, for example, by targeted temperature control in a microreactor.

[0081] In the presence of steam, the CO reacts exothermically to form CO2 and H2. The reaction proceeds preferentially over a catalyst (e.g., iron, Cu / Zn, Co / Mo) at approximately 250–450 °C. At higher temperatures, the kinetics are rapid but the chemical equilibrium is unfavorable. At lower temperatures, the equilibrium is more favored by the product, but the kinetics decrease. In a favorable variant, the water-gas conversion can be carried out in two stages, one high-temperature and one low-temperature. The CO content can thus be reduced to 0.6–1.5 vol.%, depending on the reactor operation.

[0082] According to the invention, CO2 removal from the synthesis gas stream is carried out to generate a material stream for gas separation.

[0083] CO2 removal can be achieved either by adsorptive means on a bed of packed material or selectively on a membrane. According to the invention, gas separation is performed to produce a pure hydrogen stream.

[0084] Ideally, gas separation can be carried out as a pressure swing adsorption and / or as a membrane process.

[0085] Advantageously, the process for producing hydrogen from biomass is CO2-neutral. Only the CO2 from the biomass is emitted. In a favorable variant of the invention, the CO2 from the biomass is separated. Thus, the CO2 from the CO2 removal can be fed either into a carbon storage facility or into another material, for example, in the form of carbonic acid. As a result, the process according to the invention has a significantly negative CO2 balance. This means that the process for producing hydrogen from biomass is designed as a CO2 sink.

[0086] The residual gas from the gas separation can preferably be fed to the reactor's heating device or steam generation unit in the form of tail gas. The prior CO2 removal leads to a higher calorific value of the tail gas.

[0087] Advantageously, the plant network also includes a storage capacity for hydrogen, if necessary a connection to a hydrogen network, and a hydrogen filling station for motor traffic.

[0088] The described plant system or plant is used to carry out a process for producing hydrogen from biomass. Further advantages and features of the invention will become apparent from the description, an exemplary embodiment based on drawings, and the drawings themselves.

[0089] This shows

[0090] Fig. 1 is a schematic representation of biomass gasification,

[0091] Fig. 2 is a schematic representation of the gas scrubbers,

[0092] Fig. 3 is a schematic representation of the gas separation.

[0093] Fig. 1 shows a schematic representation of biomass gasification. Biomass 1 is stored in a storage container 31 and is fed into the fluidized-bed reactor 2 in granulated form via a screw conveyor.

[0094] In this design variant, the reactor housing of fluidized bed reactor 2 is functionally divided into three housing sections. The first, deep fluidized bed housing section serves to accommodate the first, deep fluidized bed region of a fluidized bed of fluidized bed reactor 2. Sand can be used as the fluidized bed material.

[0095] An upper phase boundary of the fluidized bed lies approximately at the level of an upper boundary of the second reactor housing section 33. Above the second reactor housing section with a second fluidized bed region, the fluidized bed reactor 2 has the degassing housing section 34 with an enlarged cross-section.

[0096] The first heating device 35, in the form of a shell-and-tube heat exchanger completely covered by the fluidized bed, heats the lower fluidized bed region to a first gasification temperature in the range between 600 °C and 770 °C. The heating device 35 has a heating unit designed as a heat exchanger in the form of a burner and a further heating unit in the form of a supply unit for oxygen-containing and / or vapor-containing gas.

[0097] In the embodiment shown in Fig. 1, a material stream 23 consisting of superheated saturated steam and / or air and / or oxygen is fed to the lower fluidized bed region via the feed unit 36. The material stream 23 is fed through a plurality of nozzles in the area of ​​the bottom of the reactor housing.

[0098] A second heating device heats the upper fluidized bed region, above the second reactor housing section 33, to a second gasification temperature that is higher than the first gasification temperature. The second gasification temperature is in the range between 770 °C and 1000 °C, and in particular in the range between 770 °C and 900 °C or in the range between 770 °C and 810 °C.

[0099] Since the first gasification temperature is lower than the ash softening or biomass softening temperature, agglomeration of ash or biomass is reduced or even completely prevented during the first gasification step. Pyrolysis takes place in the first fluidized bed zone, with approximately 50% to 80% of the biomass being gasified. During pyrolysis in the upper gasification zone, lighter biomass particles that have not yet been fully converted are gasified at a sufficient conversion rate due to the higher second gasification temperature and the additional oxygen input.

[0100] The biomass 1 converted in the fluidized bed reactor 2 is converted into a material stream 3. Material stream 3 essentially comprises a high proportion of synthesis gas, but also contains portions of soot, tarry substances, aromatic hydrocarbons, and naphthalene. Material stream 3 is fed to cyclone 12 to separate coarse solids 25, such as soot and incompletely converted biomass fragments. In this exemplary embodiment, cyclone 12 is operated at approximately 800°C. Material stream 3 is fed to a steam generator 21, wherein material stream 3 is cooled to approximately 400°C using energy recovery, and a saturated steam stream 51 is generated at approximately 25-30 bar. Steam generator 21 can additionally have a steam drum containing a supply of deionized water, so that steam generator 21 can be operated in natural circulation.

[0101] The saturated steam stream 51 is fed to a steam superheater 52, which is operated with the solids 25 and 50, the liquid hydrocarbons 26 and 44, and a tail gas and / or a natural gas stream 53. In the steam superheater 52, the saturated steam stream 51 is converted to a superheated saturated steam stream 23, which can have a temperature of up to 450-500 °C. Additionally, a superheated steam stream 28 with a temperature in the range of 250 °C is generated, which is fed to the water-gas conversion 19 and the CC>2 removal 29.

[0102] In this embodiment, an oxygen stream 37 is fed to the superheated saturated steam stream 23 and introduced into the fluidized bed reactor 2 via the feed unit 36.

[0103] The 400 °C hot material stream 3 is fed to the cyclone 13, where further, finer solids 25 are separated and a material stream 4 is formed. The solids 25 are collected and fed to an energy recovery facility, for example, a burner of the steam superheater 52.

[0104] In Fig. 2, the material stream 4 is brought into intensive contact with a water stream 38 in a Venturi scrubber 14 to generate a material stream 5 and to settle a material stream 26 consisting of hydrocarbons, for example tarry components and naphthalene, as well as to settle solids 50. For this purpose, in this exemplary embodiment, the Venturi scrubber is designed as an adiabatic saturator and is spatially directly connected to the settling tank 39, in which the water stream 38 is separated from the material stream 26 and from the solids 50. In the settling tank 39, coarse solids 50 sink to the bottom, while liquid hydrocarbons float to the top and are collected via a baffle in the form of a weir in a second chamber of the settling tank 39. The solids 50 can be withdrawn discontinuously. The material stream 5 is completely loaded with water in the Venturi scrubber 14. Due to the operation of the Venturi scrubber, the material flow has a temperature of 80 to 85 °C.The material stream 26 consisting of liquid hydrocarbons and the solids 50 are fed for energy recovery, for example, in the steam superheater 51. The water stream 38 is fed from the settling tank 39 via alternately operated filters 40 back to the Venturi scrubber for further removal of solids.

[0105] To generate a material stream 6, material stream 5 is separated from a material stream 30 in the biodiesel scrubber 15. Material stream 30 consists essentially of naphthalene and aromatic hydrocarbons. Biodiesel has a favorable dissolving power for naphthalene and aromatic hydrocarbons and can separate up to 80% of their content from material stream 5. In this version, the biodiesel scrubber 15 is operated at 85 °C and 1.3 bar, whereby naphthalene can be dissolved in biodiesel before it sublimes and can lead to clogging of other plant components.

[0106] The biodiesel stream 42 is circulated from the biodiesel scrubber 15 via a settling tank 41 and a filter 43 back to the biodiesel scrubber 15. Settling matter can settle and be eluted in the settling tank 41. The material stream 6 is fed to the scrubbing column 16 to generate a material stream 7. The scrubbing column 16 is designed as a direct cooling system. The scrubbing water 24 is circulated via the settling tank 47, the filter 45, and the cooler 46 to the scrubbing column 16. In the cooler 46, the cooling water temperature is adjusted so that the sublimation conditions for naphthalene in the scrubbing column 16 are not undercut. The remaining naphthalene in the material stream 6 is absorbed into the scrubbing water 24 at approximately 40 to 55 °C. In the settling tank 47, a material stream 44, which essentially consists of naphthalene and aromatic hydrocarbons, is separated from the wash water 24 and fed to an energy recovery process.

[0107] Material stream 7 is separated from the hydrocarbons 27 remaining after scrubbing in the cooling unit 17. For this purpose, the material stream is cooled to below 10 °C and fed into the separator tank 48, where the hydrocarbons 27 are separated from material stream 8. The hydrocarbons 27 are then used for energy recovery.

[0108] The material stream 8 in Fig. 3 is compressed to approximately 18 bar in a compressor arrangement 22 and fed to the fine gas purification unit 18. In this embodiment, sulfur and sulfur-containing compounds are adsorbed on a ZnO bed, and further trace substances are removed in an activated carbon bed, so that the material stream 9 leaves the fine gas purification unit.

[0109] The purified and compressed stream 9 is introduced into the water gas conversion unit 19 with a superheated steam stream 28. The CO from stream 9 reacts exothermically to form CO2 and H2. In this embodiment, the reaction takes place over a catalyst (e.g., iron, Cu / Zn, Co / Mo) at approximately 250–450 °C.

[0110] After water gas conversion, the resulting stream 10 is passed through several coolers for CO2 removal 29. In this exemplary embodiment, a mixed matrix membrane based on metal-organic frameworks is used to separate the CO2 from stream 10. In this embodiment, the separated CO2 is processed as carbonic acid. Stream 10 is then separated in a gas separation 20 into a hydrogen stream 11 and a tail gas stream 49. For this purpose, gas separation 20 is designed as a pressure swing adsorption with five separate adsorption beds. Tail gas stream 49 is fed to the heating device 35. Stream 11 of pure hydrogen is fed to a hydrogen storage unit and expelled from there.

Claims

Patent claims Process for producing hydrogen from biomass (1 ) comprising the following steps: - Feeding biomass (1) into a fluidized bed reactor (2), - Conversion of biomass (1) into a material flow (3), - Separation of solids (25) in at least one cyclone (12, 13) to generate a mass flow (4), - Separation of hydrocarbons (26) and solids (50) in a Venturi scrubber (14) to generate a mass flow (5), - Biodiesel washing (15) to generate a material flow (6), - Water washing (16) to generate a material flow (7), - Separation in a cooling unit (17) to generate a material flow (8), - Gas purification (18) to generate a material flow (9), - Water gas conversion (19) to generate a material stream (10), - CC>2 removal from the material stream (10), - Gas separation (20) for generating a material stream (11). Method according to claim 1, characterized in that the separation of solids (25) takes place in a first cyclone (12) and a second cyclone (13) above the tar dew point. A method according to claim 1 or 2, characterized in that the Venturi scrubber (14) is operated as an adiabatic saturator. A method according to any one of claims 1 to 3, characterized in that the biodiesel scrubber (15) is operated at a temperature of more than 75 °C, preferably more than 79 °C, in particular more than 82 °C, and / or at a temperature of less than 100 °C, preferably less than 95 °C, in particular less than 90 °C. A method according to any one of claims 1 to 4, characterized in that the biodiesel scrubber (15) is operated at a pressure of more than 1 bar, preferably more than 3 bar, in particular more than 5 bar, and / or at a pressure of less than 11 bar, preferably less than 9 bar, in particular less than 7 bar.Method according to one of claims 1 to 5, characterized in that the water washing (16) is operated as direct cooling and cools the material stream (7) to more than 40 °C, preferably to more than 45 °C, in particular to more than 50 °C and / or to less than 70 °C, preferably to less than 65 °C, in particular to less than 60 °C.

7. Method according to one of claims 1 to 6, characterized in that the water washing (16) is carried out above the sublimation conditions of naphthalene.

8. Method according to one of claims 1 to 7, characterized in that hydrocarbons (27) are separated in the cooling unit (17) at a temperature of less than 15 °C, preferably less than 10 °C, in particular less than 5 °C.

9. Method according to one of claims 1 to 8, characterized in that the wash water (24) is circulated between the Venturi scrubber (14) and the water wash (16).

10. Method according to one of claims 1 to 9, characterized in that a steam generator (21) is operated between the first cyclone (12) and the second cyclone (13) with the material stream (3) to generate a saturated steam stream (51).

11. Method according to one of claims 1 to 10, characterized in that the separated CO2 of the CC>2 removal (29) is supplied to a carbon storage. Apparatus for carrying out a method according to one of claims 1 to 11. Use of the apparatus according to claim 12 for carrying out a method according to any one of claims 1 to 11.

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