EP4048630A1 - Method for producing highly pure hydrogen by coupling pyrolysis of hydrocarbons with electrochemical hydrogen separation - Google Patents

Abstract

The present invention relates to a method for producing hydrogen, which method is characterized in that: in a first stage, hydrocarbons are decomposed into solid carbon and a hydrogen-containing gaseous product mixture; the hydrogen-containing gaseous product mixture, which has a composition, with respect to the main components CH4, N2 and H2, of 20 to 95 vol% H2 and 80 to 5 vol% CH4 and/or N2, is removed from the first stage at a temperature of 50 to 300 °C and is fed, at a temperature that differs from this exit temperature by at most 100 °C, into an electrochemical separation process; and in this second stage, the hydrogen-containing product mixture is separated, in the electrochemical separation process at a temperature of 50 to 200 °C, into hydrogen having a purity of > 99.99 % and a remaining residual gas mixture.

Description

Process for the production of high-purity hydrogen by coupling a pyrolysis of hydrocarbons with an electrochemical hydrogen separation

description

The present invention includes a process for the production of hydrogen, which is characterized in that in a first stage hydrocarbons are decomposed into solid carbon and into a hydrogen-containing, gaseous product mixture, the hydrogen-containing, gaseous product mixture, which has a composition with regard to the main components CH4 , N2 and H2 from 20 to 95% by volume of H2 and 80 to 5% by volume of CH4 and / or N2, is discharged from the first stage at a temperature of 50 to 300 ° C and at a temperature, which differs from this outlet temperature by a maximum of 100 ° C, is fed into an electrochemical separation process and in this second stage the hydrogen-containing product mixture in the electrochemical separation process at a temperature of 50 to 200 ° C in hydrogen with a purity of> 99 , 99 vol .-% and a remaining residual gas mixture is separated.

Hydrogen:

Hydrogen offers the desired prerequisites to become a key factor for the energy supply of the future. The transport sector in particular is facing the great challenge of becoming more climate-friendly. In Germany, traffic is responsible for almost 20 percent of total CO2 emissions, a good half of which is accounted for by private transport.

With the introduction of electromobility, which includes battery-electric and fuel-cell-electric vehicles, the transport sector can reduce its dependence on petroleum-based fuels. In the transport sector, hydrogen is being introduced as a new fuel that does not produce any local pollutants when used with fuel cell technology.

Depending on which raw material and which process the hydrogen is produced from, it has different purity levels. In order to be able to use hydrogen in fuel cell applications, it is produced in a very high quality (99.97%, specified in ISO FDIS 14687-2), since impurities have an impact on catalysts and membranes.

Hydrogen is currently mainly produced locally in comparatively large Steam-Methane Reforming (SMR) production units and the hydrogen is separated from the gas mixtures produced by means of pressure swing adsorption. The pressure swing adsorption technology is limited to hydrogen-rich gases (depending on the accompanying gases, preferably> 50% by volume); Furthermore, only 70 to 85% of the hydrogen is separated off, the remaining hydrogen being required for the desorption of the accompanying components. The separated hydrogen is liquefied or compressed and by means of appropriate Transport vehicles with high pressure tanks (500 bar) brought to the place where it is needed, for example a hydrogen filling station.

As an alternative, hydrogen pipeline networks are being considered, in which the hydrogen is transported at different pressure levels. However, such pipeline networks have very high infrastructure costs and also require complex approval procedures, which is why implementation in the near future appears rather unlikely.

It is also contemplated to produce hydrogen decentrally in smaller production units, for example by means of electrolysis or steam reforming, and in this way to shorten or completely eliminate the transport route.

Like the electrochemical hydrogen separation membrane process (EHS), electrolysis is a membrane process and, because of its low economy-of-scale (cost advantages due to the size of the company), is more suitable for small systems than for large ones. The reason for the limited economy-of-scale is the direct dependence of the capacity on the electrochemically active surface, which in turn translates into a corresponding number of membrane-electrode units and stacks. The electrolytic splitting of water into hydrogen and oxygen requires at least 6 times as much energy as the thermal splitting of hydrocarbons into hydrogen and carbon. In the case of electrolysis, this energy must be made available in the form of electricity. Even with a small carbon footprint of the electricity generated, electrolysis hydrogen is associated with a higher carbon footprint than pyrolysis hydrogen [O. Machhammer, A. Bode, W. Hormuth, “Financial and Ecological Evaluation of Hydrogen Production Processes on Large Scale”, Chem. Ing. Tech. 2015, 87, no. 4, 409]

Another option for decentralized production of hydrogen in a small plant is the miniaturization of the steam reforming process developed for large plants (or: Steam-Methane Reforming (SMR)). Such a small system does not differ in terms of the number of machines and devices from a world-scale system. Only the machines and devices are made smaller. However, the specific consumption of raw materials and energies as well as heat transfer capacity is approximately the same. The heat transfer capacity is interesting for the economic evaluation of a process insofar as the investment costs for chemical plants correlate directly with this heat transfer capacity (see Lange J.-P., Fuels and Chemicals: manufacturing guidelines for understanding and minimizing the production costs, CATECH, Volume 5, no.2, 2001).

If process concepts are created for large systems, this usually leads to high specific investment costs for decentralized small systems. The investment costs for a complete system are many times the sum of all costs for the individual devices. The multiplier that quantifies this multiple is called the system factor. In world-scale systems, the system factor is in the order of three. Will the production capacity be reduced by the If the system concept remains the same and smaller machines and devices are used, the system factor can increase to 10.

State of the art pyrolysis:

Pyrolysis is a thermal process with the help of which hydrogen and high-purity carbon can be produced from hydrocarbons (e.g. from natural gas) with a low carbon footprint. Pyrolysis is a thermal equilibrium process that requires energy. Since the number of moles in the gas phase increases with the conversion, the conversion is higher the higher the temperature and the lower the H2 partial pressure. The pyrolysis of hydrocarbons therefore takes place at high temperatures in the range of 800 and 1600 ° C; in the case of high-temperature plasma processes even more. The carbon (pyrolysis carbon) is obtained in a highly pure form and can be used in high-price segments, e.g. as electrode material or as a preliminary product for the production of graphite for Li-ion batteries.

There are different solutions in the prior art for realizing these high temperatures in pyrolysis processes and in coke production:

In DE 600 16 59 T, US 3,264,210 and CA 2345950 oxidati ven processes are used as a heat source in different ways.

US 2,389,636, US 2,600,07, US 5,486,216 and US 6,670,058 describe the use of the solid bed as a heat carrier.

A gaseous heat transfer medium is proposed in WO2013 / 004398A2. This is preferably an H2 or N2-rich gas that is heated in an external combustion chamber and introduced into the pyrolysis zone.

In US 2,799,640, US 3,259,565 and DE 1 266273 an electrical heat source is used. US2982622 describes a resistance heated fluidized bed process. The electrical conductivity of carbon is used to resistively heat a fluidized bed made of carbon particles. The process is implemented in a moving bed reactor, with the solid particles following gravity from top to bottom and the natural gas to be split being passed through the reactor from bottom to top.

WO2018 / 083002 A1 describes a cyclical mode of operation with a combination of a reactor and a regenerator. Carrier particles are cycled through the reactor. The regenerator is filled with inert material. The reactor and regenerator are connected to one another via a combustion chamber in which part of the pyrolytically generated hydrogen is burned with air or O2 to cover the required energy. With this current conduction, all products leave the apparatus in a cooled state.

DE 2420579 describes a method based on an inductively heated carbon bed.

In DE 69208686 T, WO 2018/165483 and WO 2016/126599 the use of a plasma burner is described.

Other development approaches include either the thermocatalytic decomposition of methane [Smolinka, T .; Günther, M. (Fraunhofer ISE); Garche, J. (FCBAT): NOW study "Stand und Development potential of water electrolysis for the production of hydrogen from renewable energies ", revision of 05.07.2011], the purely thermal decomposition of methane in liquid metals [AM Bazzanella, F. Ausfelder," Low carbon energy and feedstock for the European chemical industry ”, DECH EM A-Technology study, June 20172]

The state of the art for low-temperature plasma technology is provided by [A.I. Pushkarev, et. al. "Methane Conversion in Low-Temperature Plasma, High Energy Chemistry, Vol. 43 No. 3,

2009]

To purify the pyrolytically produced hydrogen, pressure swing adsorption systems (pressure swing adsorption or PSA) and membrane processes, for example ceramic membranes and Pd-based membranes, and a combination of both variants are described (see US Pat. No. 6,653,005) and US 7,157,167). The use of an electrochemical separation to provide high-purity hydrogen is not described in these documents.

State of the art EHS:

The separation of hydrogen from reaction mixtures, especially in reactions with thermodynamically limited conversions, represents an important challenge for higher yields in the required products. The electrochemical hydrogen separation (EHS) is an electrochemical process that relies on the transport of protons (H + ions) through ion-conductive membranes and represents a new application of fuel cell technology (see WO 2016/50500 and WO 2010/115786). The hydrogen-containing mixture enters the anodic chamber, where it is oxidized to protons and electrons. An electrical power supply provides the driving force to transport the protons through the catalyzed membrane, where they combine to form "new" hydrogen at the cathode (also known as "developing the hydrogen" at the electrode) Protons are transported, the other components of the gas mixture remain in the exhaust system. The EHS is therefore able to produce hydrogen with a high degree of purity (> 99.99% H2). This high degree of purity, as is necessary for fuel cells, for example other H2 separation processes, e.g. cryogenic gas separation (cold box), pressure swing adsorption (PSA), temperature swing adsorption (TSA) and conventional membrane separation technology with hydrogen-selective metal membranes (e.g. palladium, palladium alloys), only with very expensive.

In contrast to EHS, in which the hydrogen is separated from the gas flow, with PSA, TSA and Cold Box all gas components are separated and only hydrogen remains in the product gas flow. The separation of the adsorbable components is easier, the higher the gas pressure and the lower the gas temperature. Conventional membrane separation techniques are based on the driving force of partial pressure, which means that only a low throughput can be achieved. In contrast, the electrochemical hydrogen separation is not limited by the hydrogen partial pressure difference, since an electrical potential difference is used as the separating force. Processes for separating hydrogen and nitrogen that are based solely on the difference in boiling temperatures, such as cold boxes, are expensive and do not provide pure hydrogen. According to [Z.Riebel, Hydrogen management in refineries, Petroleum $ Coal, ISSN 1337-7027, 54 (4), pp. 357-368, 2012], purities of a maximum of 98% can be achieved with cryogenic separation processes. When separating with the aid of a PSA or TSA, purities of 99.0 to 99.999 can be achieved. However, at least 10% of the hydrogen is lost in the separation.

Adsorption processes such as PSA or TSA are based, among other things, on the effect that substances can be adsorbed better the easier they condense. Since hydrogen has the lowest tendency to condense of all gases, all gas components are adsorbed in front of it, i.e. separated from the gas flow. This relationship between condensation or temperature and adsorption tendency explains why it is easier to separate C02 or CH4 from H2 than 02 or N2. The sequence of the boiling temperatures at ambient pressure is: C02 (-78 ° C), CH4 (-162 ° C), 02 (-183 ° C), N2 (-196 ° C), H2 (-252 ° C).

For large plant capacities, hydrogen separation technologies that represent volume processes, such as PSA or TSA, are more economical. In the case of small system capacities, however, these volume processes are economically inferior to the EHS.

If the system capacity is large (e.g.> 1000 kg H2 / h), the concentration of the accompanying hydrogen components in the pyrolysis product flow is low (e.g. <approx. 25 mol%) and the accompanying components are easily adsorbed in the product flow (eg CH4), hydrogen can then be obtained economically from this product stream with the help of the two separation technologies PSA or TSA in a purity of up to 99.9%.

If, on the other hand, the system capacity is small (e.g. <100 kg H2 / h) and hydrogen in the highest purity is desired (e.g. H2 filling station for fuel cell cars), then the EHS is the more economical separation method. The EHS process is a surface process, as the membrane area of a single cell is limited to 25 to 3000 cm ² . An increase in capacity can only be achieved by increasing the number of cells. This means that a plant with a large capacity is specifically not significantly cheaper than a plant with a small capacity. In other words: the EHS only has a small economy-of-scale. For the profitability of the EHS, it is also irrelevant how well the accompanying components can be condensed.

Task:

The challenge for the future lies, among other things, in the development of small, flexible and cost-effective systems that can be installed directly on site, e.g. B. installed at the hydrogen filling station, short-term and possibly transient high-purity hydrogen, especially with a low CO2 footprint, can be generated. A process concept is therefore sought that, despite a small production capacity, has a small system factor and thus has a low specific investment. Furthermore, the process concept should accommodate as many process steps as possible in a few apparatuses and have the lowest possible specific heat transfer capacity.

Solution:

Process for the production of hydrogen, characterized in that in a first stage hydrocarbons are decomposed into solid carbon and into a hydrogen-containing, gaseous product mixture, the hydrogen-containing, gaseous product mixture, which has a composition with regard to the main components CH4, N2 and H2 from 20 to 95% by volume of H2 and 80 to 5% by volume of CH4 and / or N2, is discharged from the first stage at a temperature of 50 to 300 ° C and at a temperature that is at most 100 ° C from This exit temperature differs, is fed into an electrochemical separation process and in this second stage the hydrogen-containing product mixture in the electrochemical hydrogen separation membrane process at a temperature of 50 to 200 ° C in hydrogen with a purity of> 99.99% and a remaining residual gas mixture is separated.

In the second stage, the hydrogen-containing product mixture is advantageously fed to the anodic side of a membrane-electrode arrangement, then at least part of the hydrogen contained in the product gas is electrochemically separated by means of the membrane-electrode arrangement, with at least one on the anodic side of the membrane Part of the hydrogen is oxidized to protons on an anode catalyst and the protons are reduced to hydrogen after crossing the membrane on the cathode side on the cathode catalyst.

With regard to the carbon footprint of a hydrogen filling station, the combination of “low-cost” methane pyrolysis with an EHS is more productive than the use of decentralized electrolysis, mini-SMR or central H2 production in world-scale systems in conjunction with transport to the gas station. “Low-cost” pyrolysis is to be understood as a pyrolysis which, due to the combination with an EHS, is subject to lower process-related constraints than a stand-alone pyrolysis.

In this context, "minor procedural constraints" mean the following:

The methane conversion can be lower, preferably 30% to 99.9%, particularly preferably 65% to 99.0%, in particular 85% to 98%. This means that the pyrolysis can be carried out at lower temperatures, preferably from 650 to 1200 °, particularly preferably from 750 to 1100 ° C., preferably from 800 to 1100 ° C., preferably from 900 to 1050 ° C., in particular from 950 to 1050 ° C., higher pressures , preferably at 1 to 30 bar, particularly preferably at 1 to 10 bar, in particular at 1 to 5 bar and / or with shorter residence times of advantageously 1 s-5 min, preferably 1-30 s, in particular 1-5 s become. The reaction temperature is preferably from 1100 to 1200 ° C and the residence time from 1 to 5 s or the reaction temperature from 1000 to 1100 ° C and the residence time from 5 s to 30 s or the reaction temperature from 900 to 1000 ° C and the Residence time at 30 s to 1 minute or the reaction temperature at 750 to 900 ° C and the residence time at 1 to 5 minutes.

- Lower temperatures reduce the equipment required, e.g. material selection, heat integration.

- Higher pressures in the pyrolysis reduce the compression effort if H2 has to be compressed to a few hundred bar afterwards. For example, the compaction of

1 to 10 bar as much energy as from 10 to 100 bar.

- In addition, the fact that the methane content in the product gas of the pyrolysis has no major influence on the economic efficiency makes it easier to promote the cycle for the pyrolysis carbon, which is necessary for the integration of heat. Methane (natural gas) can be used as a medium for the pneumatic conveyance of the circuit. In addition, leaks between the process areas in the pyrolysis apparatus only play a subordinate role.

The special property of the electrochemical hydrogen separation membrane process (EHS) is the separation of the hydrogen (H2) from dilute gases with little effort in the highest purity. As a result, the upstream pyrolysis process for generating the hydrogen can be designed very simply and inexpensively.

Description of pyrolysis:

In the first process stage, the (thermal) decomposition of hydrocarbons to solid carbon and hydrogen-containing, gaseous product mixture, all pyrolysis processes known to those skilled in (thermal) decomposition technology can be used. The energy required for the decomposition is preferably made available autothermally, via low-temperature plasma and / or with the aid of electrical resistance heating.

In addition to the price of natural gas, the form of the energy input is responsible for the variable costs of thermal decomposition. The sub-stoichiometric combustion of hydrocarbons with air is more favorable in this context than the sub-stoichiometric combustion with pure oxygen or the use of electric current, since some of the hydrocarbons are reformed to CO and not pyrolyzed to carbon. Furthermore, atmospheric nitrogen (N2) in the gas flow lowers the partial pressure of the hydrogen and thereby increases the equilibrium conversion.

The use of electricity as a source of energy leads to higher variable costs, but in turn enables a lower expenditure on equipment with consequently lower fixed costs. In addition, the electrification in the process itself generates practically no CO2. In addition, low-temperature plasma reactors can be used when using electricity. Since the electrons and not the molecules are excited in the low-temperature plasma, rapid methane conversion can be achieved even at low temperatures of 50 ° C to 500 ° C, which leads to low investment costs.

Process parameters that apply to all concepts: In principle, all hydrocarbons can be introduced into the reaction chamber and decomposed, although light hydrocarbons, for example methane, ethane, propane, butane, are preferred. Natural gas is preferred, in particular with a methane content of 75 and 99.9% of the molar fraction.

The hydrogen-containing, gaseous product mixture formed during the decomposition of hydrocarbons advantageously has the following composition with regard to the two main components CH4, N2 and H2 in% by volume: 10 to 99% by volume of H2 and 90 to 1% by volume are advantageous CH4 and / or N2, preferably 20 to 95% by volume of H2 and 80 to 5% by volume of CH4 and / or N2, preferably 40 to 90% by volume of H2 and 60 to 10% by volume of CH4 and / or N2, preferably 65 to 90% by volume of H2 and 35 to 10% by volume of CH4 and / or N2, preferably 80 to 90% by volume of H2 and 20 to 10% by volume of CH4 and / or N2.

Deposition of pyrolysis carbon

There are basically two different carbon separation mechanisms:

1) If there is already a carrier surface, e.g. carbon surface, and the gas volume is very small in relation to the surface, then the pyrolysis carbon is mainly deposited as a compact layer on the carrier surface. If the carrier surface is hotter than the gas volume, this mechanism is reinforced.

2) If, on the other hand, the gas volume is large in relation to the surface area (e.g. the inner wall of the reactor), predominantly soot is formed, i.e. a large number of very small pyrolysis carbon particles that can block the entire reactor volume in extreme cases. Soot formation is increased by high gas temperatures and pressures. If soot is formed, for reasons of good heat integration it should be separated from the gas stream at the reaction temperature if possible, for example by: cyclones, filters and / or beds.

In this context, debris acts like depth filters. The pyrolysis carbon covers the surfaces of the bulk particles and closes the intermediate volumes over time. If the pressure loss over the bed becomes too great, the bed must be replaced with fresh, unoccupied particles.

Low temperature plasma

A thermal decomposition of hydrocarbons operated with the aid of low-temperature plasma is known to the person skilled in the art of low-temperature plasma technology and, for example, in “Methane Conversion in Low-Temperature Plasma” by Pushkarev et al in High Energy Chemistry, 2009, Vol. 43, No. 3, pages 156-162.

The low-temperature plasma pyrolysis process advantageously includes the following process steps:

1) Submitting a bed of carrier material 2) Applying the C-containing hot pyrolysis gas to the bed with carrier material, so that the bed with carrier material heats up and carbon is deposited in the bed

3) Passing cold feed gas consisting of feed gas and cycle gas over this heated bed, so that this feed gas is heated and the carbon-laden bed cools down

4) Further heating of the feed gas by a plasma torch to produce the hot pyrolysis gas

5) Exchange of the cooled, loaded bed against a cold bed

Thermal pyrolysis:

In contrast to low-temperature plasma, thermal pyrolysis requires high reaction temperatures (> 1000 ° C). The energy required to warm up the gas flow used is in the order of magnitude of the pyrolysis reaction enthalpy. Therefore, the highest possible heat integration is advantageous, so that, for example, the cooling of the hot product streams is used to heat the feed streams.

Since methane already begins to pyrolyze above 450 ° C, recuperative heat exchange is prohibited, as pyrolysis carbon would be deposited on the heat exchanger surfaces above 450 ° C and the heat exchanger would block over time.

A regenerative heat exchange, on the other hand, is advantageous because it opens up the possibility of removing the pyrolysis carbon from the process at the same time as the heat exchange.

In the case of thermal pyrolysis, the temperatures of the pyrolysis process are advantageously between 1000 and 1600.degree. C., in particular between 1100 and 1300.degree.

In the case of thermal pyrolysis in the first stage, the pressure of the pyrolysis process is preferably 1 to 10 bar, in particular 1 to 5 bar.

The thermal conversion is advantageously carried out in the presence of solid support materials, preferably heat transfer materials, on which the carbon formed in the splitting reaction of the hydrocarbons is mainly deposited, in particular greater than 90% of the maximum pyrolysable carbon content. These solid supports can be used for regenerative heat integration.

The thermal decomposition can advantageously be carried out in a fixed bed, fluidized bed or moving bed reactor, the term “fluidized bed” also being understood to mean a production bed if the solid reactor contents in the reaction zone are at least partially fluidized and above and / or below the Reaction zone the solid contents of the reactor are moving, but no longer fluidized.

The carrier is preferably passed through the reaction space as a moving bed, the hydrocarbons to be decomposed being passed in countercurrent to the carrier. The reaction space is advantageously designed as a vertical shaft, possibly as a conical shaft, so that the Movement of the moving bed comes about solely under the action of gravity. The Wan derbett is advantageously homogeneous and evenly flow through.

The support materials of this reaction bed are advantageously temperature-resistant in the range from 1000 to 1800.degree. C., preferably from 1300 to 1800.degree. C., particularly preferably from 1500 to 1800.degree. C., in particular from 1600 to 1800.degree.

Ceramic carrier particles, in particular materials according to DIN EN 60 672-3 such as alkali aluminum silicates, magnesium silicates, titanates, alkaline earth aluminum silicates, aluminum and magnesium silicates, mullite, aluminum oxide, magnesium oxide and / or zirconium oxide are advantageous as temperature-resistant carrier materials . Furthermore, non-standardized ceramic high-performance materials such as quartz glass, silicon carbide, boron carbide and / or nitrides can serve as temperature-resistant carrier materials. These heat transfer materials can have different expansion capacities compared to the carbon deposited on them.

The use of carbonaceous material as granules is also advantageous. In the present invention, a carbon-containing granulate is understood to mean a material which advantageously consists of solid grains. The carbon-containing granules are advantageously spherical. The granulate advantageously has a grain size, ie an equivalent diameter, which can be determined by sieving with a certain mesh size, of 0.05 to 100 mm, preferably 0.1 to 50 mm, more preferably 0.2 to 10 mm, in particular 0, 5 to 5 mm. In the method according to the invention, a large number of different carbon-containing granules can be used. Such granules can consist predominantly of coal, coke, coke breeze and / or mixtures thereof, for example. Furthermore, the carbon-containing granulate can contain 0 to 15% by weight based on the total mass of the granulate, preferably 0 to 5% by weight, of metal, metal oxide and / or ceramic.

ATP

An autothermally operated thermal decomposition (pyrolysis), ATP, of hydrocarbons is known to those skilled in thermal decomposition technology and, for example, in Manfred Voll, Peter Kleinschmit, “Carbon, 6. Carbon Black”, Ullmanns Ecyclopedia of Industrial Chemistry, Wiley, 2012 described.

The ATP is advantageously carried out at temperatures between 500.degree. C. and 1500.degree. C., preferably between 600.degree. C. and 1300.degree. C., particularly preferably between 700.degree. C. and 1200.degree.

The pressures are advantageously between 1 and 10 bar, preferably between 1 and 5 bar and particularly preferably between 1 and 3 bar.

In connection with an EHS, the temperature can advantageously be lower and thus the turnover can be lower and air can advantageously be used instead of expensive pure oxygen, because neither a high methane content nor a high N2 content in the pyrolysis product gas reduces the profitability of the EHS in contrast to PSA. For example, the temperature is from 650 to 1200 °, preferably from 750 to 1100 ° C, in particular from 800 to 1000 ° C. For example, the pressure is from 1 to 30 bar, particularly preferably from 1 to 10 bar, in particular from 1 to 5 bar.

Suitable carrier materials are e.g. ceramic carrier particles, in particular materials according to DIN EN 60 672-3 such as alkali aluminum silicates, magnesium silicates, titanates, alkaline earth aluminum silicates, aluminum and magnesium silicates, mullite, aluminum oxide, magnesium oxide and / or zirconium oxide. Furthermore, non-standardized high-performance ceramic materials such as quartz glass, silicon carbide, boron carbide and / or nitrides can serve as temperature-resistant carrier materials. These heat transfer materials can have different expansion capacities compared to the carbon deposited on them. The use of carbonaceous material as granules is particularly preferred. In the present invention, a carbon-containing granulate is to be understood as a material which advantageously consists of solid grains. The carbon-containing granules are advantageously spherical. The granulate advantageously has a grain size, ie an equivalent diameter, which can be determined by sieving with a certain mesh size, of 0.05 to 100 mm, preferably 0.1 to 50 mm, more preferably 0.2 to 10 mm, in particular 0, 5 to 5 mm. In the method according to the invention, a large number of different carbon-containing granules can be used. Such granules can consist predominantly of coal, coke, coke breeze and / or mixtures thereof, for example. Furthermore, the carbon-containing granulate can contain 0 to 15% by weight based on the total mass of the granulate, preferably 0 to 5% by weight, of metal, metal oxide and / or ceramic.

The ATP advantageously includes the following process steps:

1) Submission of a bed with unloaded carrier material.

2) Combustion of educt or product gas with air to form a hot fuel gas to provide the enthalpy of reaction

3) Mixing this hot fuel gas with the feed gas (preferably natural gas), so that the feed gas pyrolyses to H2 and carbon.

4) loading the bed with unloaded carrier material with the C-containing hot pyrolysis gas, so that the bed with unloaded carrier material heats up and carbon is deposited in the bed.

5) When the bed is heated up and can no longer absorb carbon, the cold reactant gas is passed over this bed. The feed gas is heated up and the carbon-laden bed cools down.

6) The cooled, laden bed is exchanged for a cold bed.

The ATP offers the best prerequisites for low-cost pyrolysis in combination with the EHS: The energy input takes place advantageously through combustion of the educt or product gases with air. This means that neither expensive electricity nor expensive pure oxygen is required for the input of energy needed. The usually existing disadvantage when using combustion air - that the hydrogen-containing product gas mixture contains large amounts of nitrogen - does not play a negative role when using an EHS as a hydrogen separation process.

According to the invention, a reactor concept is proposed that is based on a revolver principle (FIG. 2). A vertically standing drum (1), which continues to rotate in sections in cycles, is divided into 4 segments (2a-d), for example, by dividing walls that are arranged in a star shape and have good heat-insulating properties. The segments are advantageously open at the bottom and closed at the top by a plate (3) which contains one hole per segment (3a-d). A stationary plate 4 with only 3 holes (4a-c) in the same shape and position as (3a-c) is advantageously located above plate 3. Segment (2d) is advantageously closed at the top because a hole (4d) is missing in this cycle.

The holes (4c) and (4b) are advantageously connected via a tube (5, shown dotted), in which the device for the energy input (6c, shown as a lightning bolt) can advantageously be located.

The energy input can alternatively also take place in that a hot gas is generated outside the tube in, for example, a burner (6a) or in a plasma generator (6b), which gas is then advantageously introduced into the tube 5.

A tube (7, also shown dotted) advantageously opens into hole (4a) which is above hole (3a). Particles (P1), also called carrier material, are advantageously fed to segment (2a) through pipe (7), which act as depth filters for separating the pyrolysis carbon and / or as regenerators for heat integration.

The segments (2a-c), which are advantageously open at the bottom and rotate in sections, are advantageously closed at the bottom by a fixed plate (8) to such an extent that advantageously no particles can get into the space (9) below. Plate (8) advantageously only has a corresponding opening (8d) for segment (2d). The particles (P2) can advantageously pass from segment (2d) into the space (9) below.

Plate (8) advantageously has pipe feeds (10b and 10c, shown dotted) under the two segments (2b) and (2a). These pipe feeds are advantageously designed in such a way that, although gases can flow into the segments, no particles can get into the pipes from the segments. This can be achieved, for example, with a close-meshed screen mesh. From pipe (10b) cold pyrolysis product gas (G4) is advantageously withdrawn from segment (2b) and cold feed gas (G1) advantageously flows through pipe (10c) into segment (2c).

In FIG. 3, the individual segments (2a-d) are drawn in a linear row in order to illustrate what is happening in the individual segments at any point in time. A dark background means that the segment or the particles in it are cold. A light background means that the segment or the particles in it are hot. The transitions from dark to light or light to dark represent moving temperature fronts. The arrows (Tb) and (Tc) indicate the direction of migration of the temperature fronts.

A cycle is described below:

• Segment (2a) is located under the pipe (7) and is filled with fresh particles (P1). • In segment (2b) the hot reaction gas (G3) is passed from the pipe (5), which heats the fresh and still cold particles to the reaction temperature.

• Cold feed gas (G1) flows into segment (2c) and cools the hot particle fill as it rises. In return, the supplied natural gas is heated up by the hot particles and reaches the pipe (5) as hot feed gas (G2).

If the energy input takes place by burning a mixture of fuel gas and air (G5) in a burner (6a) or by an electrically generated high-temperature plasma (6b) then these two devices (6a) or (6b) generate a very hot gas that is in the tube ( 5) is mixed with the preheated feed gas (G2) to form the hot reaction gas (G3).

The hot reaction gas (G3) can contain pyrolysis soot formed as soon as it enters segment (2c). According to the invention, the greater part of the pyrolysis reaction takes place in segment (2b).

• Segment (2d) is located above the opening (8d) so that the cooled particles (P2) loaded with pyrolysis C can fall into the chamber (9) below in order to be discharged from there.

The drum remains in one position as long as the particle bed in segment (2c) needs to be cooled down. Then one cycle is over and the drum rotates one segment further. The segment that was in the previous cycle (2a) becomes segment (2b) etc. in the new cycle. It is assumed that the time for filling segment (2a) and emptying segment (2d) is shorter than cooling the particle bed in the segment (2c).

As can be seen, four process engineering operations are combined in a single apparatus according to the invention, which otherwise take place in up to four apparatuses: reaction, heat input to cover the heat of reaction, separation of the pyrolysis carbon and heat recovery (heating of the natural gas and cooling of the pyrolysis carbon) .

Alternatively, the drum can be divided into segments with the segment number Ns _egment = 2 + 2 ^* n, with n =

1, 2, 3, etc.

The possibility of working up and recycling the bed of particles from segment (d) is known to those skilled in solids management technology.

Resistance heating:

A thermal decomposition of hydrocarbons operated with the aid of resistance heating is known to those skilled in the art of thermal decomposition technology and, for example, in CH 409890, US 2982622, the international patent application No.

PCT / EP2019 / 051466.

In a preferred embodiment, two electrodes are installed in the beds, between which the beds act as an electrical resistor and heat up when the current is passed through due to the electrical transmission losses. The flow of current can take place both transversely to the directions of flow of the beds as well as along them. Since all conversion processes require energy, it can be advantageous to design the pyrolysis stage of the process according to the invention as a hybrid process so that it can also be operated with excess electricity obtained from renewable sources (see WO 2014/090914, European patent application with the number 19178437.0).

EHS:

The technology of electrochemical hydrogen separation is based on ion transport membranes that selectively conduct protons (H +). These membranes are known from other applications such as electrodialysis, fuel cells and water electrolysis. The structure for hydrogen separation is largely identical to a fuel cell structure. The core of the EHS system is the membrane electrode assembly (MEA). On the anodic side, hydrogen molecules are oxidized to protons on a catalyst. These protons pass through the proton-selective membrane to the cathode side, while electrons travel to the cathode through an external circuit. As long as electricity is applied, the EHS system separates the hydrogen from gas mixtures. The technology of electrochemical hydrogen separation is described, for example, in WO 2016/50500 and WO 2010/115786.

The usual compounds and elements known to the person skilled in the art can be used as the catalytically active material, which can catalyze the dissociation of molecular hydrogen in atomic hydrogen, the oxidation of hydrogen to protons and the reduction of protons to hydrogen. For example, Pd, Pt, Cu, Ni, Ru, Fe, Co, Cr, Mn, V, W, tungsten carbide, Mo, molybdenum carbide, Zr, Rh, Ru, Ag, Ir, Au, Re, Y, Nb and alloys are suitable and mixtures thereof, Pt is preferred according to the invention. The catalytically active materials can also be in a supported form; carbon is preferably used as the support. In a further development of the membrane-electrode arrangement, the amount of the catalytically active material of the cathode catalyst is 0.1 mg / cm2 to 2.00 mg / cm2, preferably 0.1 mg / cm2 to 1 mg / cm2, based on the total area of the anode and cathode.

The membrane used according to the invention selectively conducts protons, that is to say in particular that it is not electron-conducting. According to the invention, all materials known to the person skilled in the art can be used for the membranes, from which proton-conducting membranes can be formed. Also selectively proton-conducting membranes, as they are known from fuel cell technology, can be used according to the invention.

Materials that are particularly suitable for the production of gas-tight and selectively proton-conducting membranes are polymer membranes. Suitable polymers are sulfonated polyether ketones (S-PEEK), sulfonated polybenzoimidazoles (S-PBI) and sulfonated fluorocarbon polymers (e.g. NAFION®). Furthermore, perforated polysulfonic acids, styrene-based polymers, poly (arylene ethers), polyimides and polyphosphazenes can be used. Membranes made from polybenzamidazoles are very particularly preferably used, in particular MEAs based on polybenzimidazole and phosphoric acid, such as those marketed, for example, under the name Celtec-P® by BASF SE.

The operating conditions of the EHS system depend heavily on the MEA selected. When using Celtec ^® technology, it is advantageous to use a voltage of 0.1 to 0.4V and a current of 0.2 to 1 A / cm ² . The separation of the H2 is not based on differential pressure, but on electrochemistry. The EHS can therefore advantageously be operated without pressure. As long as there is no differential pressure between anode and cathode, a higher pressure is advantageous, which leads to a higher separation rate.

The hydrogen content in the hydrogen-containing product gas from stage 1, the pyrolysis stage, is advantageously in the range from 1% by volume to 99% by volume, preferably 5% to 95% by volume, preferably 10 to 95% by volume , preferably 20 to 95% by volume, preferably 40 to 90% by volume, in particular 65 to 90% by volume, hydrogen. The hydrogen separation rate is typically between 60% and 99%, preferably 70 to 95%, in particular 80% to 90%, the higher the separation rate, the higher the electrical energy requirement of an EHS.

The water content in the hydrogen-containing feed gas is advantageously in the range from 0.5 to 50%, preferably 0.5 to 5%, in particular 0.5 to 1%.

The current density is advantageously 0.1 to 1 A / cm ² , preferably 0.2 to 0.7 A / cm ² , in particular 0.2 to 0.5 A / cm ² . The voltage is advantageously 1 to 1000 mV, preferably 100 to 800 mV, in particular 150 to 350 mV.

These electrochemical hydrogen separation systems are operated at temperatures advantageously from 50 to 200.degree. C., preferably from 120 to 200.degree. C., preferably from 150 to 180.degree. C., in particular from 160 to 175.degree. The pressure is advantageously from 0.5 to 40 bar, preferably from 1 to 10 bar, in particular from 1 to 5 bar. The pressure difference between the anodic and the cathodic side is advantageously less than 1 bar, preferably less than 0.5 bar.

This mode of operation enables a high tolerance to gas contamination, e.g. CO (3%) and H2S (15 ppm) to be achieved.

This comparatively low temperature enables relatively quick and material-friendly switching on and off, an advantage especially for non-continuous operation in decentralized systems with fluctuating hydrogen sales, e.g. B. in gas stations.

The active area of the membrane electrode unit is advantageously in the range from 5 cm ² to 20,000 cm ² , preferably 25 to 10,000 cm ² , in particular 150 to 1000 cm ² The thickness of the membrane-electrode unit is advantageously in the range from 250 to 1500 μm, preferably 600 to 1000 μm.

A hydrogen separation stack consisting of end plates, bipolar plates, seals and membrane-electrode units separates with a volume of 1 m ³ advantageously separates 100 to 200 Nm ³ / h hydrogen and is therefore significantly smaller than systems with physical hydrogen separation.

The energy consumption is typically between 3 and 7 kWh / kg H2 - depending on the gas composition and the selected separation rate.

Since the electrochemical separation is based on gas-tight, highly selective proton-conducting membranes, the purity of the hydrogen generated can be very high, typically greater than 99.9%, preferably greater than 99.95%, in particular greater than 99.99%.

The following membrane-electrode unit specifications are particularly preferred:

PBI = polybenzimidazole I.V. = inherent viscosity

Details on the combination of the two systems:

The decomposition of the hydrocarbons and the electrochemical separation are advantageously carried out at the same pressure level. Both stages, thermal decomposition and electrochemical separation, are advantageously carried out at an absolute pressure of 1 bar to 30 bar. The pressure difference between the two stages is advantageously in the range from 0.001 bar to 5 bar.

The hydrogen-containing product mixture is advantageously introduced into the process stage of electrochemical separation at the same temperature level that it has after the process stage of decomposition. The hydrogen-containing product mixture advantageously has a temperature of from 20 to 400 ° C., preferably from 50 to 300 ° C., preferably from 80 to 250 ° C., preferably from 100 to 200 ° C., in particular from 120 to 180 ° C., after the decomposition process stage ° C and is advantageously discharged from the first stage at this temperature (exit temperature).

The cooling of the hot product-containing gas from the reaction temperature to these exit temperatures can take place, for example, in a fixed bed. The hydrogen-containing product mixture is fed into the electrochemical separation process at a temperature which advantageously differs by a maximum of 100 ° C., preferably a maximum of 50 ° C., in particular a maximum of 25 ° C., from this outlet temperature.

The residual gas mixture remaining after the electrochemical separation process is advantageously at least partially recirculated into the first stage, the pyrolysis reaction. Advantageously, 99.99 to 90%, preferably 99.95 to 95%, preferably 99.9 to 98%, in particular 99.8 to 99% of the remaining residual gas amount is recirculated into the first stage. The residual gas that is not recirculated is advantageously discharged as purge gas. Advantageously, 0.01 to 10%, preferably 0.05 to 5%, particularly preferably 0.1 to 2%, in particular 0.2 to 1% of the remaining amount of gas are discharged as purge gas.

The ratio of feed (hydrocarbons) to cycle gas (residual gas mixture) in the first stage in kg / kg is advantageously 0.01: 1 to 1: 5, preferably 0.03: 1 to 1: 2, in particular 0.05: 1 to 1 :1.

Optional intermediate steps:

One or more of the following process steps can optionally precede the EHS: heat integration, reforming of NH3 to N2 and H2, hydrogenation of multiple bonds, water gas shift (WGS). If several of the intermediate steps mentioned are installed, the hydrogen-containing, gaseous product mixture from the thermal decomposition is advantageously first reformed before the hydrogenation and / or the water-gas shift takes place.

Reforming NH3 to N2 and H2:

In the event that the EHS membrane contains acidic components, basic accompanying components in the pyrolysis product stream would be absorbed by these and thus negatively change the properties of the membrane over time. In this case, a process stage is advantageously installed upstream of the EHS, in which the basic components are removed from the product gas stream. For example, NH3 can be reformed using catalysts known to those skilled in the art. This selective ammonia reforming (SAR) can be designed very easily in terms of equipment (see e.g. NOx reduction in car exhaust with AdBlue).

The removal of ammonia is recommended for values of typically above 1 ppm, preferably above 10 ppm and in particular above 25 ppm.

Hydrogenation of multiple bonds:

CH compounds with multiple bonds (eg olefins or acetylenes) are adsorbed by the EHS catalyst and thereby reduce its activity. In the event that the pyrolysis product gas contains more than 10 mol ppm CH compounds with multiple bonds, a hydrogenation process is preferred in which the multiple bonds with part of the water hydrogen contained in the product gas is hydrogenated to single bonds with catalysts known to those skilled in hydrogenation technology, which are no longer a catalyst poison for the EHS.

The removal of CH multiple bonds is recommended for values of typically over 1000 ppm, preferably over 5000 ppm and in particular over 10000 ppm.

Water Gas Shift (WGS):

Carbon monoxide is also adsorbed by the EHS catalyst, thereby reducing its activity. So if carbon monoxide is formed during the energy input for the pyrolysis and the pyrolysis product gas contains more than 3% CO, then this carbon monoxide, which is harmful to the EHS catalyst, is advantageous before entering the EHS at low temperatures (<400 ° C) with the help of the also im Combustion water present in the product gas stream - or if required - can be converted to further hydrogen and carbon dioxide with the aid of externally supplied water vapor and a WGS catalyst known to those skilled in the water gas shift technology. In contrast to carbon monoxide, carbon dioxide is not a catalyst poison for the EHS.

The removal of CO is recommended when the proportion in the gas stream is typically more than 0.5% by volume and particularly preferably more than 1% by volume, in particular more than 3% by volume.

Refueling hydrogen cars:

The hydrogen present after the electrochemical separation can be fed to a hydrogen car in accordance with the current state of the art.

Examples:

The process examples were calculated using the ASPEN ⁺ -analog in-house thermodynamic simulator CHEMASIM. The reactor design was carried out in EXCEL on the basis of the thermodynamic simulation.

As an example, the process was calculated for an H2 capacity of 1000 kg / d or 42 kg / h. The value is based on the currently discussed the largest H2 filling stations.

The following process parameters are used as a comparison measure:

• As a measure of the variable costs:

- the demand for natural gas or methane

- the power consumption

- the accumulation of pyrolysis-C as a possible credit

• As a measure of the investment costs:

- the investment-relevant heat transfer capacity or the investment-relevant transferred and specific heat related to the product quantity.

- In addition, the specific investments available today from the literature are still used.

• As a measure of the ecology, which is the main driver for the development of H2 filling stations:

- the carbon footprint of the process including the carbon footprint of the electricity required.

For the operation of an H2 filling station, mains electricity is practically the only option, because operation must be available around the clock, regardless of the weather and the position of the sun.

For grid electricity, the future-oriented electricity mix forecast for 2030 for the EU27 was used with 19% nuclear, 33% fossil and 48% renewable energy. The data are taken from [7] and represent a European average. This results in a carbon footprint of 190 kg C02 / MWh _ei. for the electricity mix in EU 27 in 2030.

It is also assumed that the filling station is connected to a 25 bar natural gas network.

For the process comparison, all processes produce 20 bar H2.

All examples are calculated loss-free.

State of the art:

Electrolysis:

For the comparison of the method according to the invention with the prior art, performance data for the electrolysis are used as they were published for the alkaline electrolysis in [8].

According to this, the efficiency of the overall system, which works at atmospheric pressure and 80 ° C, is 68%. This corresponds to a specific electrical energy consumption of 48.4 kWh / kg H2. If the H2 is compressed from 1 bar to 20 bar, there is another 1.6 kWh / kg H2.

The specific electrical energy requirement is therefore a total of 50.0 kWIWkg H2.

The specific carbon footprint is then 9.50 kg C02 / kg H2.

32% (= 100% - 68%) of the electrical energy is converted into heat and must be dissipated to the environment via heat exchanger surfaces. The specific heat transfer energy is therefore 22.8 kWh / kg H2.

According to [4], the specific investment is € 3070 a / 1 H2.

For the intermediate cooling of the H2 compression from 1 to 20 bar, 1.7 kWh / kg H2 are required.

Specifically, a total of 22.8 + 1.7 = 24.5 kWh of heat is transferred per kg of H2.

The electrolysis therefore requires per kg H2:

50.0 kWh electricity 24.5 kWh heat exchanger and causes per kg H2:

- 9.50 kg of CO2

Mini SMR:

In [9] detailed data are given for a mini-SMR system for 90 kg / h H2. This corresponds to only twice the capacity of a capacity of 42 kg H2 / h on which an H2 filling station is based and is therefore very suitable for comparing the prior art with the variants according to the invention. An update of the cost data based on the process data and the list of machines and equipment from [9] can be found in [10].

Afterwards H23,1 kg of natural gas and 2.1 kWh _ei power required per kg. The natural gas has the following composition in% by weight: 88.7% CH4, 4.7% C2H6, 3.9% C3H8, 1.3% N2 and 1.3% C02. The specified electricity requirement not only covers the actual requirement of the process, but also the natural gas compression from 7 to 22 bar before the process and the H2 compression after the process from 21 bar to 207 bar. For the actual process, the data given results in an electricity requirement of 0.2 kWh _ei / kg H2.

The use of mains electricity results in 0.04 kg C02 / kg H2 and production results in 8.42 kg C02 / kg H2. In total, the production of 1 kg of H2 according to the state of the art mini-SMR technology causes 8.46 kg of C02. An installed specific heat transfer capacity of 18.5 kW per kg H2 / h is calculated from the values specified for the heat exchangers. The cost-relevant heat transfer performance of the reformer is not included. No information was given about this.

According to [9], the specific investment of a mini-SMR is 12,100 € a / 1 H2. In order to better compare the state of knowledge with the variants according to the invention, the SMR process published in [9] with the company's own thermodynamic process simulator CH EM ASIM recalculated, with which the variants according to the invention were also calculated. The numbers given in [9] were used; Operating parameters and heat transfer rates are specified and the unknown heat transfer rate for the reformer is thus determined. It is then 8.9 kW per kg H2 / h. The total specific heat transfer capacity is 18.5 + 8.9 = 27.4 kW per kg H2 / h.

If 100% CH4 is used in the calculation instead of a natural gas with the composition specified above, the usage figures and specific heat transfer capacities change only marginally. For the sake of simplicity, the following results are therefore based on simulations with 100% CH4 as the feed gas.

The Mini-SMR therefore needs per kg H2:

- 3.10 kg CH4 0.2 kWh electricity

27.4 kWh heat exchanger and causes per kg H2:

- 8.46 kg of CO2

Tube trailer H2:

In [11] detailed data are given for a world-scale SMR system for 9058 kg / h H2. According to the "Major Equipment" list, as in the case of the Mini-SMR, 847.4 MMBTU / hr of heat are transferred, which corresponds to the equivalent of 27.4 kWh / kg H2. In the case of the world-scale plant, however, more natural gas is required than in the case of the mini-SMR. According to this, the world-scale plant requires 3.32 kg natural gas / kg H2 instead of 3.10 kg natural gas / kg H2 in the case of the mini-SMR. In return, in addition to H2, the world-scale plant also produces 4.4 kg of water vapor / kg of H2. Since the assessment of water vapor depends very much on the local conditions, it was assumed here, for the sake of simplicity, that the world-scale system has the same number of uses as the mini-SMR. The cost advantage of a world-scale system compared to a mini-SMR lies in the economy of scale.

For the transport, it is assumed that the H2 is brought in 500 bar containers on trailers across the street to the petrol stations and these containers are emptied at the petrol station to 21 bar before they are transported back to the world-scale facility. For transport, the H2 must be compressed from 20 to 500 bar at the world-scale system [5]. 1.6 kWh / kg H2 must be used for this. However, this high pressure in the container has an advantageous effect when compressing at the gas station to the final pressure of, for example, 950 bar the refueling of the cars. However, since the pressure at the gas station decreases from 500 to 20 bar when the containers are emptied, a mean pre-pressure in the container of (500 + 20) / 2 = 260 bar is assumed for comparison with the other variants. This reduces the effort for further compression from 260 bar to 950 bar, for example, compared to 20 bar to 950 bar by 1.3 kWh / kg. Ultimately, in the case of H2 transport, 1, 6 - 1, 3 = 0.3 kWh / kg H2 more electricity must be used than in the case of the mini-SMR.

According to [5], the specific investment for compression is 430 € a / 1 H2.

With 500 bar tanks, at the moment A 401 tanker truck can transport a maximum of 1344 kg H2 [5] which are emptied at the filling station up to a pressure of 21 bar. 54 kg of H2 then remain in the container and are then returned to the world-scale plant.

According to [5], the specific investment for the additional storage costs at the filling station is 4740 € a / 1 H2. Overall, the specific investment is then 430 + 4740 = 5170 € a / 1 H2.

It is further assumed that such a tanker truck requires 35 liters of diesel per 100 km. In terms of energy content, this corresponds to 31 kg of natural gas per 100 km and is currently represents a top value.

For 42 kg / h H2, 0.78 trips are necessary per day (= 42 ^* 24 / (1344 - 54)). If you calculate the energy consumption and the associated C02 emissions for the different distances - e.g. for 100 km and for 500 km - between the central world-scale system and the decentralized filling station, you get the following results:

The tube trailer variant requires per kg H2:

3.10 kg CH4 for generation in the central world-scale system + 0.08 kg CH4 equivalents in the form of diesel for a distance of 100 km + 0.30 kg CH4 equivalents in the form of diesel for 500 km distance 0, 6 kWh electricity 27.4 kWh heat exchanger and causes per kg H2:

8.75 kg C02 for a distance of 100 km and 9.18 kg C02 for a distance of 500 km and

Process variants according to the invention:

ATP & EHS: (Figure 4)

A combination of an autothermally operated pyrolysis (ATP) and an EHS was calculated as an example. The advantage of this combination is a low consumption of electricity and natural gas as well as a low heat transfer rate.

42 kg / h of high-purity H2 are generated.

Natural gas is pre-cleaned. This can be done, for example, as described in [9], by catalytic desulphurisation.

147 kg / h of purified natural gas at a pressure level of 25 bar are fed into the process at ambient temperature (25 ° C). 25 kg / h are deducted from this in order to be burned ver in a burner with air to hot burner gas to cover the energy requirement. 430 kg / h of burner air is compressed from the ambient pressure and temperature to 1.5. This requires 5 kW of electrical power.

The rest of the natural gas is mixed with 227 kg / h of cycle gas in a jet pump. The pre-pressure of the natural gas is used in the jet pump to compress the cycle gas from 1.0 to 1.5 bar.

The feed gas enters the bed of segment (2c) at 28 ° C and is heated to 1000 ° C therein. The bulk cools down in the process. A temperature front is created that moves from bottom to top. 199 kW are transferred thermally.

During this heating process, part of the natural gas already pyrolyzes.

After exiting segment (2c), the gas is mixed with the hot fuel gas and further reactions start.

Although there is no catalyst present, it must be assumed that part of the natural gas is reformed to CO and H2 with the water produced during combustion. For example, it is assumed here that 10% of the combustion water reacts. It is also assumed that the CO 2 from the combustion abrea with the pyrolysis C formed in accordance with the Boudouard equilibrium to CO in the bed in segment (2b).

The hot reaction gas heats the bed in segment (2b) and cools down in the process. 199 kW are also thermally transferred there.

The product gas (757 kg / h), cooled to 160 ° C., contains 15 mol% CO. This CO is converted to CO2 and H2 in a WGS reaction with water vapor up to a residual concentration of 0.2%. This creates 69 kW of excess heat that has to be dissipated. This is done by generating 5 bar steam, which is required as additional steam (93 kg / h) for the WGS reaction.

In the EHS 99% of the H2 formed are separated s electrochemically from the product gas of the WGS (850 kg / h) ^'. This requires an electrical output of 177 kW.

The remaining anode off-gas (808 kg / h) is divided into the cycle gas, which is fed back into the process, and the exhaust gas, which is burned in the flare, producing 232 kg of CO 2 / h.

42 kg / h H2 leave the EHS at a pressure of 1 bar. An electrical output of 68 kW _{ei is} required for compression to 20 bar. From the intermediate cooling, 65 kW must be drawn off as heat flows.

In order to be able to provide a regenerative heat exchanger output of 199 kW in segments (2b) and (2c), 1034 kg / h of fresh pyrolysis C must be filled in segment (2a). 1080 kg / h of pyrolysis C are withdrawn from segment (2d). The difference, 46 kg / h, is a pyrolysis C product.

The ATP & EHS process thus produces 1.1 kg of high-purity pyrolysis C per kg of H2 and requires:

- 3.5 kg of CH4

6.0 kWh of electricity 10.0 kWh heat exchanger and causes per kg H2:

- 6.7 kg of CO2

NT plasma & EHS: (Figure 5)

A combination of pyrolysis operated with a low temperature plasma (NT plasma) and an EHS was calculated as an example. The task of the plasma here is to increase the reaction speed. The advantage of this combination lies in the relatively low process temperatures and the absence of CO, which has a positive effect on the energy requirements of the EHS.

42 kg / h of high-purity H2 is generated.

Natural gas is pre-cleaned. This can be done, for example, as described in [9], by catalytic desulphurisation.

168 kg / h of purified natural gas at a pressure level of 25 bar are fed to the process at ambient temperature (25 ° C) and mixed with 205 kg / h of cycle gas in a jet pump. The pre-pressure of the natural gas is used in the jet pump to compress the cycle gas from 1.0 to 1.5 bar.

The feed gas (373 kg / h) enters the bed of segment (2c) at 28 ° C and is heated to 700 ° C therein. The bulk cools down in the process. This creates a temperature front that moves from bottom to top. Thereby 244 kW are thermally transferred.

After exiting segment (2c), the gas molecules are excited e.g. by pulsed microwaves in a low-temperature plasma device and then passed into segment (2b).

The hot reaction gas heats the bed in segment (2b) and cools down to 160 ° C. in the process. Thereby, 244 kW are also transferred thermally.

The cooled product gas to 160 ° C (248 kg / h) is passed into a EHS, s are separated from the product gas electrochemically in the 91% of the ge formed H2 ^'. This requires an electrical output of 102 kW.

From the remaining anode off-gas (206 kg / h), 1 kg / h is withdrawn as a purge flow in order to prevent the build-up of inert components.

42 kg / h H2 leave the EHS at a pressure of 1 bar. An electrical output of 68 kW _{ei is} required for compression to 20 bar. From the intermediate cooling, 65 kW must be drawn off as heat flows.

In order to be able to provide a regenerative heat exchanger output of 244 kW in segments (2b) and (2c), 1828 kg / h of fresh pyrolysis C must be filled in segment (2a). 1953 kg / h of pyrolysis C are withdrawn from segment (2d). The difference, 125 kg / h, is a pyrolysis C product.

The NT plasma & EHS process produces 3.0 kg of high-purity pyrolysis C per kg of H2 and requires:

- 4.0 kg of CH4

- 10.4 kWh of electricity 9.4 kWh heat exchanger and causes per kg H2:

- 2.0 kg of C02

WH pyrolysis & EHS: (Figure 6)

A combination of electrically heated pyrolysis, in which the pyrolysis C bed acts as resistance heating (WH pyrolysis) and an EHS was calculated as an example. The principle of WH pyrolysis is described in US2982622, for example. The advantage of this combi nation lies in the simplicity of the reactor and the design-related possible higher operating pressures, which leads to smaller reactor dimensions and a subsequent lower compression effort for H2. In addition, the absence of CO has a positive effect on the energy requirements of the EHS. By combining WH pyrolysis with EHS, a gas circuit with a high proportion of H2 can be built up. The higher H2 level reduces soot formation and also lowers the energy requirement in the EHS. In addition, the circulation of gas opens up new possibilities for conveying the pyrolysis C circuit (e.g. pneumatic conveyance) and enables better heat integration.

42 kg / h of high-purity H2 is generated.

Natural gas is pre-cleaned. This can be done, for example, as described in [9], by catalytic desulphurisation.

167 kg / h of purified natural gas at a pressure level of 25 bar are fed to the process at ambient temperature (25 ° C) and mixed with 68 kg / h of cycle gas in a jet pump. The pre-pressure of the natural gas is used in the jet pump to compress the cycle gas from 5.0 to 5.2 bar.

The feed gas (235 kg / h) enters the bed at the bottom of the fluidized bed reactor at 28 ° C and is heated to 1000 ° C therein. In return, the pyrolysis C bed that slides down cools down. With this counterflow heat exchange, 367 kW are thermally transferred. 888 kg / h of particles are drawn off at 28 ° C. from the bottom of the reactor via locks. 763 kg / h are recirculated for the heat integration (367 kW + 315 kW) and fed back to the reactor at the top via locks. 125 kg / h of pyrolysis-C are drawn off as a highly pure product.

In the reactor, electricity is passed through the bed in the reaction zone to cover the reaction heat (262 kW _ei ). The heat of reaction of 262 kW introduced in this way does not affect the required amount of pyrolysis C-cycle and is therefore not significant for the amount of the investment. The C produced during methane splitting leads to the pyrolysis C particles growing.

The methane fission product gas flows upwards and warms up the recirculated particles that slide downwards. In return, the product gas cools down. The degree of heat integration can be controlled by the amount of cycle gas. With this countercurrent heat exchange, 315 kW are thermally transferred

The cooled product gas to 160 ° C (110 kg / h) is passed into a EHS, s are separated from the product gas electrochemically in the 50% of the ge formed H2 ^'. For this, a specific electrical power of 63 kW is _ei necessary. The remaining anode off-gas (68 kg / h) is recirculated. In order to prevent a build-up of inert components, 0.1 kg / h are withdrawn from the cycle gas.

42 kg / h H2 leave the EHS at a pressure of 5 bar. An electrical output of 29 kW _{ei is} required for compression to 20 bar. 38 kW must be drawn off as heat flows from the intercooling.

The WH pyrolysis & EHS process produces 3.0 kg of high-purity pyrolysis C per kg of H2 and therefore requires:

- 4.0 kg of CH4

- 8.4 kWh of electricity

19.2 kWh heat exchanger and causes per kg H2:

- 1.6 kg of C02

Comparison:

The results of the sample calculations are summarized in Table 1. The results clearly show that the process concepts according to the invention can produce H2 with a lower carbon footprint than according to the current state of the art. The lower carbon footprint is the main driver for H2 mobility.

In addition, with the process concepts according to the invention, the investment-relevant heat transfer capacities are lower than in the case of the current state of the art,

The increased consumption of natural gas in the process concepts according to the invention is offset by the additional extraction of high-purity carbon. This increases the raw material yield and thus added value.

According to the state of the art, an SMR can process only about 32% (= 1kg H2 / 3.1 kg CH4) of the methane used in a value-adding manner. However, the process concepts according to the invention can utilize up to 100% of the methane used (= (1 kg H2 + 3 kg C) / 4 kg CH4).

The process concepts according to the invention also have only 1/5-el to 1/9-el of the power requirement of a water electrolysis. However, a small amount of electricity is particularly important with regard to the expansion of renewable energies that will be necessary in the future, as mobility here is in competition with other energy consumers.

Table 1: Comparison of the results from the example calculations.

Literature:

Error! Reference source not found.

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Claims

Patent claims:

1 . Process for the production of hydrogen, characterized in that in a first stage hydrocarbons are decomposed into solid carbon and a hydrogen-containing product mixture, the hydrogen-containing, gaseous product mixture, which has a composition with regard to the main components CH4, N2 and H2 of 20 to 95 vol .-% H2 and 80 to 5 vol .-% CH4 and / or N2, is discharged from the first stage at a temperature of 50 to 300 ° C and at a temperature that is no more than 100 ° C from this outlet Temperature differs, is fed into an electrochemical separation process and in this second stage the hydrogen-containing product mixture is separated in the electrochemical separation process at a temperature of 50 to 200 ° C in hydrogen with a purity of> 99.99% and a remaining residual gas mixture .

2. The method according to claim 1, characterized in that a membrane-electrode unit is used in the electrochemical separation process of the second stage and the membrane is a polymer membrane selected from the group consisting of sulfonated polyethers, sulfonated polybenzoimidazoles, sulfonated fluorocarbon polymers, perforated polysulfonic acids, Styrene-based polymers, poly (arylene ethers), polyimides, and polyphosphazenes.

3. The method according to claim 2, characterized in that the polymer membranes used are polybenzamidazoles based on polybenzimidazole and phosphoric acid.

4. The method according to at least one of claims 1 to 3, characterized in that the decomposition in the first stage is carried out at a temperature of 900 ° C to 1200 ° C and with a residence time of 1 min to 1 s.

5. The method according to at least one of claims 1 to 4, characterized in that 99.99 to 90% of the remaining amount of gas from the electrochemical separation process is recirculated into the first stage.

6. The method according to at least one of claims 1 to 5, characterized in that both stages are carried out at an absolute pressure of 1 bar to 30 bar and the pressure difference between the two stages is in the range from 0.001 bar to 5 bar.

7. The method according to at least one of claims 1 to 6, characterized in that the energy required for the decomposition reaction of the first stage is made available autothermally or via low-temperature plasma.

8. The method according to at least one of claims 1 to 7, characterized in that the autothermal pyrolysis process comprises the following steps:

1) Submission of a bed made of carrier material

2) Combustion of reactant or product gas with air to form a hot fuel gas to provide the enthalpy of reaction

3) Mixing this hot fuel gas with the feed gas, so that the feed gas pyrolyses to H2 and carbon

4) Applying the C-containing hot pyrolysis gas to the bed with carrier material, so that the bed with carrier material heats up and carbon is deposited in the bed

5) Passing cold reactant gas over this heated bed, so that the reactant gas heats up and the carbon-laden bed cools

6) Exchange of the cooled, loaded bed against a cold bed

9. The method according to at least one of claims 1 to 7, characterized in that the low-temperature plasma pyrolysis process comprises the following steps:

1) Submission of a bed made of carrier material

2) Applying the C-containing hot pyrolysis gas to the bed with carrier material, so that the bed with carrier material heats up and carbon is deposited in the bed

3) Passing cold feed gas consisting of feed gas and circulating gas over this heated bed, so that this feed gas is heated and the bed loaded with carbon cools

4) Further heating of the feed gas by a plasma torch to produce the hot pyrolysis gas

5) Exchange of the cooled, loaded bed against a cold bed

10. The method according to at least one of claims 1 to 9, characterized in that the hydrogen present after the electrochemical separation process is fed to a hydrogen car.