DE102016208938A1 - Process and plant for producing a hydrocarbon - Google Patents

Abstract

The invention relates to a method and a plant for producing a hydrocarbon (HC). Here are a first production process (11), in which a raw material (RM) in an endothermic reaction to a product (P) and carbon dioxide (CO2) is implemented, and a second production process (12), in which carbon dioxide (CO2) in a exothermic reaction with hydrogen (H2) to give the hydrocarbon (HC) is reacted, both materially and thermally coupled to each other. The material coupling consists in the supply of the CO2 produced in the first production process (11) to the second production process (12). In addition, a thermal coupling is achieved by the heat energy (Q) released in the second production process (12) being supplied to the first production process (11) for at least partially covering its energy requirement.

Description

The invention relates to a method and a system for producing a hydrocarbon, in particular a fuel for vehicles, from carbon dioxide (hereinafter carbon dioxide) CO ₂ by material and thermal coupling of two production processes.

The search for alternative fuels for decarbonization-based sustainable mobility has so far failed to produce workable solutions that provide sufficient mass mobility energy. Decentralized, local / regional niche solutions and biomass-based approaches must be critically evaluated in the long term, as food crops will become a priority in increasing acreage competition and collateral damage such as rainforest destruction is unacceptable.

On the other hand, carbon dioxide is produced and emitted in large quantities as by-product in various industries. The "deacidification" process (calcination) of limestone CaCO ₃ for the production of the economic assets cement and lime generates enormous CO ₂ process emissions (2008 in Germany: a total of 21 million t CO ₂ or approx. 1 million t CO ₂ per site ₎ ). The same applies to the iron / steel industry (2009 in Germany 52.3 million t CO ₂ or per blast furnace on average 5.5 million t CO ₂ ). These two industries are also characterized by relatively high CO ₂ contents in the exhaust gas, namely by a CO ₂ content in the exhaust gas of the cement production 20 to 30 vol .-% and 27 Vol .-% in steel production, compared to only 14% typical CO ₂ concentration in the exhaust gas of a coal power plant. These high levels reduce the cost of CO ₂ separation. It is desirable to absorb these emissions as efficiently as possible for further processing and continue to use them.

In WO 2010/069 622 A1 the use of carbon dioxide CO _{2 is described} as a raw material for the production of a synthetic fuel produced as sustainable as possible. For this purpose, hydrogen is generated electrolytically using a combination of regenerative and conventional power and reacted with CO ₂ to methanol or another hydrocarbon. The CO ₂ is taken from the flue gas of combustion processes or other oxidation processes of carbon by CO ₂ capture a cement factory, etc. The heat energy released in the synthesis reaction is used, for example, for a seawater desalination or heating plant.

DE 10 2013 010 909 B3 describes the use of CO ₂ from the calcination of limestone in a shaft furnace system using carbonaceous energy sources and converting the CO ₂ to methane or methanol with regenerative hydrogen from a separate electrolysis process. The main feature is the increase in the CO ₂ concentration in the excess exhaust gas.

The invention is based on the object of providing a method for producing a hydrocarbon which can be used, for example, as a fuel, which has a further improved energy efficiency. It is also intended to provide a system suitable for carrying out the method.

This object is achieved by a method for producing a hydrocarbon and a corresponding system with the features of the independent claims. Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

• – einen ersten Produktionsprozess, bei dem ein Rohstoff in einer endothermen Reaktion zu einem Produkt und Kohlendioxid umgesetzt wird, und
• – einen zweiten Produktionsprozess, bei dem das im ersten Produktionsprozess erzeugte Kohlendioxid in einer exothermen Reaktion mit Wasserstoff, der vorzugsweise aus erneuerbarer Energie erzeugt wird, unter Erhalt des Kohlenwasserstoffs umgesetzt wird.

Erfindungsgemäß sind der erste und der zweite Produktionsprozess so miteinander gekoppelt, dass eine im zweiten Produktionsprozess freigesetzte Wärmeenergie zumindest teilweise dem ersten Produktionsprozess zur zumindest teilweisen Deckung seines Energiebedarfs zugeführt wird. The method according to the invention comprises:

• A first production process in which a raw material is converted into a product and carbon dioxide in an endothermic reaction, and
• A second production process in which the carbon dioxide generated in the first production process is reacted in an exothermic reaction with hydrogen, which is preferably generated from renewable energy, to obtain the hydrocarbon.

According to the invention, the first and second production processes are coupled to one another such that a heat energy released in the second production process is at least partially supplied to the first production process for at least partially covering its energy requirement.

• – einen ersten Prozessreaktor, der eingerichtet ist, einen Rohstoff in einer endothermen Reaktion zu einem Produkt und Kohlendioxid umzusetzen, und
• – einen zweiten Prozessreaktor, der eingerichtet ist, das im ersten Prozessreaktor erzeugte Kohlendioxid in eine exotherme Reaktion mit Wasserstoff unter Erhalt des Kohlenwasserstoffs umzusetzen.

Die Anlage zeichnet sich dadurch aus, dass der erste und der zweite Produktionsreaktor so miteinander gekoppelt sind, dass eine im zweiten Produktionsreaktor freigesetzte Wärmeenergie dem ersten Produktionsreaktor zur zumindest teilweisen Deckung seines Energiebedarfs zugeführt wird. Another aspect of the present invention relates to a plant for producing a hydrocarbon, comprising:

• A first process reactor adapted to convert a raw material into a product and carbon dioxide in an endothermic reaction, and
• A second process reactor arranged to convert the carbon dioxide generated in the first process reactor into an exothermic reaction with hydrogen to obtain the hydrocarbon.

The plant is characterized in that the first and the second production reactor are coupled to one another so that a heat energy released in the second production reactor is supplied to the first production reactor for at least partially covering its energy requirement.

The two production processes or process reactors are thus on the one hand materially coupled to each other according to the invention, on the one hand, the CO ₂ as by-product occurring in the first production process as raw material (educt) is fed to the second production process. In addition, the two production processes or production reactors are thermally coupled to each other by the waste heat of the exothermic second production process or reactor is used to meet the energy needs of the endothermic first reduction process or reactor. This in-process thermal coupling of the two processes and reactors further reduces the energy requirement to be supplied from the outside, thus increasing the energy efficiency of the process.

The approach presented here is particularly suitable for the large-scale production of a fuel to be designated as regenerative using hydrogen from the electrolysis regeneratively generated stream. The energy carrier, for example in the form of methane, which is suitable for use in mobility, produced according to the invention, can thus be presented competitively over other regenerative fuels because of its large-scale production. The process can also be referred to as power-to-gas (PtG). Instead of methane, a hydrocarbon can be produced in liquid form - this process is also known as power-to-liquid (PtL).

Various embodiments of the first, carbon dioxide by-product producing production process are possible within the scope of the invention. According to a first embodiment, the first production process comprises calcination of limestone, in which limestone (mainly CaCO ₃ ) is converted as raw material in an endothermic reaction to lime (CaO) as product and CO ₂ (see equation 1). Calcination, also known as lime burning, takes place in cement works, in the production of lime for the production of cement and other materials. By using the by-product of the calcination of lime CO ₂ for the second production process thus all products of calcination are used as marketable products or intermediates. CaCO ₃ → CaO + CO ₂ (1)

In an alternative embodiment of the process, the first production process involves the iron smelting of iron ore, in which iron ore, which may contain various iron oxides (FeO _x = Fe ₂ O ₃ , Fe ₃ O ₄ , FeO), as raw material in various endothermic reactions to elemental iron than Product and CO _{2 is} reacted (see equations 2 to 4). Iron ore smelting usually takes place in blast furnaces, where the iron ore is reduced to elemental iron with carbon monoxide, which is obtained from the simultaneous combustion of coal. The pig iron is used in particular in steel production. 3Fe ₂ O ₃ + CO → 2Fe ₃ O ₄ + CO ₂ (2) Fe ₃ O 4 + CO → 3FeO + CO ₂ (3) FeO + CO → 3Fe + CO ₂ (4)

Both production processes, lime burning and iron ore smelting, represent technical processes that take place on an industrial scale worldwide and thus have correspondingly high CO ₂ emissions and immense energy consumption. By utilizing these CO ₂ emissions as a valuable material for hydrocarbon production and by at least partially covering the immense energy demand of these production processes from the exothermic methanation reaction or other hydrocarbon-producing reactions, a significant energy and environmental benefit is achieved.

The approach according to the invention offers, in particular for integrated iron and steel, steel and cement plants, an economic option for reducing CO ₂ emissions and improving the economic conditions of the volatile steel and cement business through the use or marketing of so-called co-products such as the production of industrial oxygen the electrolysis, which can be used directly for steel production.

In the second production process, the CO ₂ obtained from the first production process is converted into a hydrocarbon in an exothermic reaction with hydrogen. The hydrocarbon produced in the second production process is in particular methane CH ₄ , since this can be obtained in a simple manner from CO ₂ by reacting with hydrogen (Equation 5). CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O (5)

Preferably, the second production process is carried out without external supply of a carbonaceous energy source, that is, the total carbon content of the hydrocarbon produced comes from the CO ₂ of the first production process. Furthermore, it is preferable to carry out the second production process without supplying oxygen. Preferably, a catalyst is used for the second production process, wherein one for the Fischer Tropsch synthesis common catalyst can be used. In particular transition metals are used here, especially cobalt, iron, nickel and / or ruthenium.

In a preferred embodiment of the method, the hydrogen used in the second production process is obtained from an electrolysis process, in particular from the electrolysis of water (Equation 6). Such an electrolysis process can be carried out using established methods and can be carried out without environmentally relevant by-products. In addition, the oxygen produced in the electrolysis of water is a valuable product, which can be used externally, but preferably internally in the process. H ₂ O → H ₂ + ½O ₂ (6)

Another positive effect of the electrolysis is the stabilization of the power grid by the extremely high absorption capacity of excess volatile electricity by means of the electrolysis plant and the long-term storage capacity in the form of the hydrogen and oxygen gases produced hereby. This stabilization allows a virtually unlimited expansion of renewable electricity generation.

A further embodiment of the method provides that the first production process oxygen is supplied, which is the first production process either as a direct or indirect reactant or as an oxidant for a supplied fuel, with which the remaining energy needs of the endothermic reaction of the first production process is covered. Preferably, this oxygen supplied to the first production process is also obtained from an electrolysis process, in particular from the same electrolysis process already used for the production of the hydrogen used in the second production process (see above). Thus, both products of the electrolysis process, namely hydrogen and oxygen, can be used within the process of the invention.

A further embodiment of the invention provides that the method further comprises an oxyfuel process in which a fuel is burned by means of enriched or pure oxygen. In this case, a heat energy released in the oxyfuel process can be at least partially supplied to the first production process for at least partially covering its energy requirement and / or the carbon dioxide generated in the oxyfuel process can be supplied to the second production process as educt. Preferably, both the heat and the CO _{2 are used} accordingly in the process. The oxyfuel process is distinguished from conventional combustion processes of fuels in that the oxidant used for combustion is not air, but pure or at least enriched oxygen. Due to the absence or low concentration of nitrogen, argon and other constituents of the air arise in the oxyfuel process almost exclusively the products CO ₂ and water. Thus arise in the oxyfuel process not only the above products in relatively high purity, but also due to the particularly high flame temperatures large amounts of heat released at a high temperature level. Both the chemical products and the thermal products of the process can thus be very well integrated and used in the existing process. The oxyfuel process is preferably dimensioned such that the heat energy generated in this process, together with the heat energy generated in the second production process, is sufficient to meet the heat energy requirement of the first production process.

In a preferred embodiment of the method, the oxygen used in the oxyfuel process is obtained from an electrolysis process, in particular from the water electrolysis described above. After separation of the hydrogen from the oxygen / hydrogen mixture of the electrolysis process, the oxygen is available with high purity and can thus be used very well for the oxyfuel process.

In a preferred embodiment of the invention, the electricity required for the electrolysis process used in the method according to the invention is obtained from regenerative (renewable) energies. Here, for example, electricity generated from wind turbines and / or photovoltaic systems is used. Due to the good storability of the products H ₂ and O ₂ , the electrolysis process can also serve to stabilize the power grid.

In a further embodiment, water which is contained in the exhaust gas of the second production process is at least partially supplied to the electrolysis process. Thus, the external water requirement of the process can be reduced.

Furthermore, it can be provided to supply the exhaust gas of the second production process, which usually contains steam, to a steam turbine in order to thus generate usable mechanical energy with the removal of the steam. The condensed water separated in this case can be advantageously supplied to the electrolysis process.

Preferably, the method further comprises a CO ₂ separation process in which the carbon dioxide obtained from the first production process (and optionally from the oxyfuel process) is separated before its delivery to the second production process of other ingredients. The separation process depends in particular on the nature of the first production process and the associated by-products. In principle, however, carbon monoxide possibly contained in the gas mixture can remain contained in the educt gas fed to the second production process, since this can readily be converted into the hydrocarbon in addition to the CO ₂ in the second production process. Suitable methods of separating CO ₂ include, for example, gas scrubbing processes by absorption (for example, amine scrubbing), thermal swing adsorption, pressure swing adsorption, cryogenic separation processes, membrane separation processes, and others.

In the context of the present invention, it is basically possible to carry out the first and second production processes in a coupled reaction in a single reactor. In this case, the raw material, such as limestone or iron ore, hydrogen and oxygen and optionally further reactants are fed to the reactor, so that they react to produce CO ₂ as an intermediate to the product, in particular calcium or pig iron, and the fuel.

Preferably, however, the first and second production processes are carried out in separate reactors. The advantage here is that the different pressure and temperature levels, which are to be preferred for the respective processes, can be set independently of each other. However, this does not rule out that the two reactors can be housed in a common housing.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a plant for producing a hydrocarbon according to a first embodiment of the invention;

2 a plant for producing a hydrocarbon according to a second embodiment of the invention;

3 a plant according to the invention for producing a hydrocarbon using the example of a coupled with a methanation calcination process, and

4 a plant according to the invention for the production of a hydrocarbon on the example of a coupled with a methanation Eisenschüttenprozesses.

1 shows a plant as a block diagram 100 for producing a hydrocarbon HC according to an embodiment of the present invention.

Core of the plant 100 are two production processes, namely a first production process 11 working in a first process reactor 11 takes place, as well as a second production process 12 working in a second process reactor 12 takes place. Material flows are in 1 and the following figures are shown as double-lined arrows and energy flows as single-line arrows.

The first production process 11 comprises reacting a raw material RM in an endothermic reaction, that is to say using heat Q, to form a product P and carbon dioxide CO ₂ . The raw material RM is made from a raw material storage 13 supplied and the product P is in a product storage 14 stored (between). That in the first production process 11 Carbon dioxide produced is the second production process 12 fed, optionally in a CO ₂ storage 15 can be cached. In the second production process 12 For example, the CO _{2 is} reacted with hydrogen H ₂ to give a hydrocarbon HC and water H ₂ O. This process takes place exothermically, ie with the release of heat Q. That is responsible for the reaction of the second production process 12 required hydrogen becomes from a hydrogen storage 16 fed. The hydrocarbon HC as the main product of the second production process 12 is in a hydrocarbon storage 17 stored (between).

The second production process 12 Released heat Q becomes the first production process 11 supplied to meet its heat demand at least partially. The transmission of the heat energy Q can, for example, by direct supply of the hot exhaust gas from the second reactor 12 in the first process reactor 11 respectively. Alternatively, the waste heat via a heat exchanger of a cooling circuit of the second process reactor 12 discharged and via another heat exchanger of the first process reactor 11 be delivered there. Also possible is the two process reactors 11 and 12 directly thermally coupled with each other, for example, by immediate neighborhood or a common, the two processes 11 and 12 separating housing wall. Furthermore, an intermediate storage of the heat, for example in a so-called phase change material (phase change material) is possible. This approach is then beneficial if a batchwise, non-continuous process control for the heat-delivering process 12 he follows.

Depending on the nature of the first and second production process 11 . 12 will be in the second process 12 Released thermal energy Q is not sufficient in all cases to meet the energy needs of the first production process 11 cover up. For this purpose can be provided, the first production process 11 Oxygen O ₂ , in an oxygen storage 18 is stored, or to supply air. The oxygen then serves as an oxidant for a fuel, such as coal or the like, to meet the required heat of reaction through this additional combustion process. However, oxygen can also act as an indirect or immediate reactant for the first production process 11 such as the iron ore smelting, where the oxygen is used to burn coal for the intermediate generation of carbon monoxide to react iron oxide (see 4 ).

In the 1 shown attachment 100 further includes an electrolysis process 19 , in particular a water electrolysis process. In this case, water H ₂ O is decomposed while supplying electrical energy EE into its constituents hydrogen H ₂ and oxygen O ₂ . The intermediate storage of these gases takes place in the already mentioned memories 16 and 18 , The electrolysis of water is carried out by known methods in intermittent operation and with a modular design of the electrolysis system. The current EE used is preferably more volatile, regeneratively generated current, for example from wind turbines and / or photovoltaic systems. That for the electrolysis 19 used water can according to the in 1 shown plant at least partially from the second production process 12 be won. For example, the water from the exhaust gas of the reactor 12 be obtained by a water separator or by means of a downstream steam turbine with integrated water separator. Alternatively or additionally, the water can be obtained from the public water supply network.

Depending on the type of the first production process 11 Furthermore, a CO ₂ separation stage can be provided (see following figures).

2 shows a plant for producing a hydrocarbon according to a second embodiment of the invention, wherein the same elements as in 1 are denoted by the same reference numerals. The explanations apply to this 1 corresponding.

The system according to 2 is different from the 1 by incorporating an oxyfuel process, which is in an oxyfuel reactor 21 or an oxyfuel power plant 21 takes place. In the oxyfuel process 21 the combustion of a fuel takes place by means of pure or enriched (compared to the oxygen content of air) oxygen. In the present example, the one from the water electrolysis 19 derived oxygen O ₂ from the oxygen storage 18 the oxyfuel reactor 21 fed and implemented in this. As fuel of the oxyfuel process 21 In principle, any solid, liquid or gaseous fuel can be used. According to one embodiment of the invention, the second production process 12 recovered hydrocarbon 17 partly for the oxyfuel process 21 used.

The main chemical product of the oxyfuel process 21 is CO ₂ . Depending on the fuel used here, other components in the exhaust of the oxyfuel power plant may be present 21 be included, for example, carbon monoxide CO, nitrogen oxides NO _x , sulfur oxides SO _x and others. Also the exhaust gas of the first production process 11 In addition to CO ₂ , it may contain other constituents such as CO, NO _x or SO _x . Both the exhaust of the first production process 11 and the oxyfuel process 21 be in the in 2 shown attachment 100 in a CO ₂ separation stage 22 separated from the CO before this the second production process 12 is supplied.

The oxyfuel process 21 is very exothermic. The heat of reaction Q released in this process becomes the endothermic first production process 11 fed. Thus, the energy requirement of the first production process 11 on the one hand by the waste heat of the second production process 12 as well as the waste heat of the oxyfuel process 21 covered. Furthermore, it can be provided that a part of the waste heat of the oxyfuel process 21 the CO ₂ separation stage 22 is supplied to cover their energy needs in whole or in part.

3 shows an example of a system according to the invention 100 in which a calcination process as the first process stage 11 with a methanation process of CO ₂ as a second process stage 12 are materially and thermally coupled together in the manner described above.

In the first process stage 11 according to 3 Limestone, which consists mainly of calcium carbonate CaCO ₃ , burned (calcined), with calcined as the main product burned lime, which consists mainly of calcium oxide CaO, and CO ₂ as exhaust gas. process reactor 11 Here is usually a rotary kiln of a lime or cement plant. The as raw material 13 Limestone used is preferably one which contains comparatively small amounts of foreign substances, so as possible pure CO ₂ exhaust gas for the downstream methanation process 12 to create. Additionally or alternatively, the addition of aggregates to the limestone 13 possible, which bind foreign substances.

The process 11 added oxygen serves to burn a fuel to at least partially reach the required reaction temperature for the calcination. Thus, the CO _{2 of} the exhaust gas of the reactor comes 11 partly from the in 3 shown chemical reaction of calcination and partly from the combustion of the fuel.

The calcium oxide CaO (quick lime or quicklime) can be taken from the process as a marketable product or used to produce cement by adding appropriate additives. For example, the CaO can be sintered together with corresponding additives in a shortened rotary kiln for the production of cement clinker.

The in the reactor 11 Calcination takes place at a temperature of about 1200 ° C. As already described, this temperature level is at least partially due to the waste heat of the second production process 12 and optionally the waste heat of the oxyfuel process 21 shown. Also possible is the integration of external energy, for example by an arc process or by a H ₂ / O ₂ burner without supply of carbonaceous energy sources.

The second production process 12 which is executed here as a methanation process, sees the implementation of the calcination 11 originating CO ₂ with that from the electrolysis 19 derived hydrogen H ₂ to methane CH ₄ and water vapor. As a reactor 12 Here, for example, a fluidized bed reactor using a Fischer-Tropsch catalyst can be used. Except from the calcination process 11 and optionally oxyfuel process 21 produced CO ₂ is no supply of a carbonaceous energy source for the methanation reaction. The methane CH ₄ obtained in this reaction may optionally be used after purification of pollutants as fuel for heating or as fuel for internal combustion engines. If necessary, work-ups can be carried out here in order to adapt to a required quality with regard to the calorific value, hydrogen content, pollutant content, etc.

4 shows a plant according to the invention 100 using the example of a methanation process 12 coupled ironworks process 11 , In this example thus includes the first production process 11 a blast furnace process in which the iron ore is smelted, in which case FeO _{x stands} for the various iron oxides present in iron ores. In the iron ore smelting, the iron ore FeO _{x is converted} in a known manner in a blast furnace with carbon monoxide, which is usually produced from the combustion of coal with air or here enriched oxygen, to pig iron Fe and carbon dioxide CO ₂ . The pig iron Fe obtained here is used especially for steel production or the like.

The exhaust gas of the blast furnace process contains not only CO ₂ but also unreacted carbon monoxide CO. Both ingredients are in a separation step 22 separated from the remaining components of the exhaust gas and the methanation process 12 supplied as starting materials. The implementation of the methanation process corresponds to that in 3 , Both educts, CO ₂ and CO, are here by reaction with the from the electrolysis 19 derived hydrogen converted to methane CH ₄ .

• – Basis ist ein Zementwerk mittlerer Größe mit CO₂-Emissionen von 1 Mio. Jahrestonnen (t/a). Von 1 Mio. t CO₂-Gesamtemissionen stammen konservativ angenommen 50 % aus den Prozessemissionen der Kalzination des Kalksteins CaCO₃. Diese 0,5 Mio. t/a CO₂ führen zu 0,636 Mio. t/a CaO für das Zementwerk und ermöglichen auf Basis der Kohlenstoffbilanz und der Stöchiometrie die Herstellung von 0,18 Mio. t/a Methan CH₄. Diese Methanmenge hat einen Gesamt-Heizwert von 2,54 TWh/a basierend auf dem spezifischen Heizwert von 14 MWh/t CH₄.
• – Nach der Elektrolyse-Reaktionsgleichung 2H₂O → 2H₂ + O₂ entstehen 2 mol H₂ mit einer Bildungsenthalpie von 0,079 kWh/(2 mol H₂) beziehungsweise 39,5 MWh/(t H₂). Die Methanisierung benötigt nach der Reaktionsgleichung CO₂ + 4H₂ → CH₄ + 2H₂O jedoch 4 mol H₂, um 1 mol CH₄ herzustellen. Daraus ergibt sich ein theoretischer Mindestbedarf von 2 × 0,045 = 0,09 Mio. t/a H₂ mit einem Heizwert von 3,2 TWh/a. Der reale elektrische Energiebedarf für eine entsprechend leistungsfähige Elektrolyseanlage erreicht auf Basis eines Stromverbrauchs von 53,6 MWh/t H₂ beziehungsweise einem Elektrolyseur-Wirkungsgrad von 74 % 4,3 TWh/a. Bei Wirkungsgraden der Elektrolyse unter 70 % ergibt sich ein elektrischer Energiebedarf von über 4,6 TWh/a.
• – Bei ausschließlich elektrischer Bereitstellung des Energiebedarfs zur Zementherstellung von 830–908 kWh/t Zement ergibt sich ein Kostenblock auf Basis eines Outputs von 0,7 Mio. t Zement und eines mittleren Lieferpreises von 50 EUR/MWh von etwa 30 Mio. EUR. Der Erlös für den Zement beläuft sich bei einem Zementpreis zwischen 127 und 139 EUR/t auf ca. 100 Mio. EUR.
• – Die Kosten für den elektrischen Energiebedarf in einem weiterentwickelten Elektrolyseur 53,6 MWh/t H₂ ergeben für 0,09 Mio. t H₂ und dem resultierenden Energiebedarf von 4,3 TWh/a den dominierenden Kostenblock von 215 Mio. EUR.
• – Die Kosten des Prozesswassers für die Elektrolyse (0,8 Mio. t) werden auf Basis von 2 EUR/t H₂O mit 1,6 Mio. EUR geschätzt (ohne Wasserrückgewinnung aus dem Prozess).
• – Der als Industriegas vermarktbare Sauerstoff fällt in Höhe von 0,7 Mio. t an und stellt bei Sauerstoffpreisen von 100 EUR/t O₂ ein Erlöspotenzial von 70 Mio. EUR, bei 140 EUR/t von ca. 100 Mio. EUR dar. Hauptverbraucher für Industrie-Sauerstoff ist die Stahlindustrie. Die derzeit häufigste Produktionsmethode für die wichtigsten Industriegase aus der Luft ist die kryotechnische Luftzerlegung, die auch wertvolle Edel- und Spurengase liefert. Insofern kann der Elektrolyse-Sauerstoff die Stahlindustrie im Hinblick auf ihre CO₂-Verpflichtungen bei Nutzung des Elektrolyse-EE-Sauerstoffs aber auch wesentlich entlasten.
• – Die Methanisierung weist ein Output von 0,18 Mio. t CH₄ auf und führt zu einem Methan-Erlöspotenzial von 65,5 Mio. EUR bei einem angenommenen Erdgaspreis von 26 EUR/MWh (0,36 EUR/kg) oder zu einem Potenzial von 151 Mio. EUR bei einem angenommenen Gaspreis von 60 EUR/MWh (0,84 EUR/kg). Das Methan kann Tankstellen für mobile Anwendungen zugeführt werden.
• – Die derzeit bestehende Gesamtspeicherkapazität der deutschen Erdgasinfrastruktur von ca. 200 TWh sollte für die Nutzung als Speicher für die volatilen Überschuss-Strommengen in Form von EE-PtG-H₂ (PtG = Power-to-Gas) und EE-PtG-Methan ausreichend sein.
• – Aufgrund des modulartigen Aufbaus von Elektrolyseanlagen und der systembedingten Entkoppelung von Elektrolyse und der Methanisierung steht die gegenüber Anlagen für komplexe verfahrenstechnische Prozesse relativ leicht zu erweiternde und unter anderem durch Zuschaltung von Modulen instationär arbeitsfähige Elektrolyseanlage als Überschussstromsenke zur Verfügung. Der erzeugte Wasserstoff kann sowohl in das Erdgasnetz eingespeist werden als auch für die weitere Methanisierung eingesetzt werden. Die Kapazität der Methanisierung wird vom CO₂-Angebot der Zementherstellung bestimmt.
• – Zu dem hier ermittelten Bedarf von 4,3 TWh für die Elektrolyse und beispielsweise einer Übertragung mittels einer Doppelsystem-380 kV-Drehstromleitung mit 3,5 GW Übertragungskapazität ergibt sich eine minimale Einspeisezeit von ca. 1200 h bei entsprechender Aufnahmefähigkeit der Elektrolyse-Anlage von mindestens 3,5 GW. Bei Einhaltung der Überbrückungszeit während der Überschussphasen des EE-Stroms von 14 Tagen oder 336 h ergeben sich etwa vierfache Leitungskapazität und vierfache Aufnahmefähigkeit des Elektrolyseurs mit jeweils notwendigen 15 GW. Bei einem geschätzten Gesamtspeicherbedarf von 15 TWh und 14 Tagen Überbrückungszeit würden 3 bis 4 derartige Anlagen in Deutschland mit einer Gesamtkapazität von 45 GW benötigt. Eine ausreichend dimensionierte Elektrolyseanlage kann in der verbrauchernahen Koppelung mit dem Erdgasnetz anfallende Überschussmengen kurzfristig aufnehmen.
• – Die (zwangsläufig mit Unsicherheiten behaftete) Gesamtbilanz lässt die Wirtschaftlichkeit des Verfahrens aussichtsreich erscheinen.
• – Als ein präferierter Nutzungspfad wird das erzeugte EE-PtG-Methan (PtG = Power-to-Gas) gegebenenfalls unter Anreicherung mit Wasserstoff (derzeit für Verbrennungsmotoren auf 2 Vol. % begrenzt) unter Einhaltung der Erdgasnetzspezifikationen dazu genutzt, um bei einem angenommenen spezifischen Gasverbrauch/Fahrzeug von 3 kg Methan/Wasserstoff-Gemisch/100 km mit einem Heizwert von mehr als 15 kWh/kg Mischgas ca. 400.000 Gasfahrzeuge bei einer Jahresfahrleistung von 15.000 km zu versorgen. Damit kann zum Beispiel der PKW-Bestand der Stadt und der Region Hannover nachhaltig betrieben werden.

Below are some quantitative considerations of the overall process of the invention using the example of the coupling methanation and calcination:

• - Based on a medium-sized cement plant with CO ₂ emissions of 1 million tonnes per year (t / a). Conservatively speaking, 50% of 1 million tonnes of CO ₂ total emissions come from the process emissions of calcination of the limestone CaCO ₃ . These 0.5 million t / a CO ₂ lead to 0.636 million t / a CaO for the cement works and enable the production of 0.18 million t / a methane CH ₄ based on the carbon balance and the stoichiometry. This amount of methane has a total calorific value of 2.54 TWh / a based on the specific calorific value of 14 MWh / t CH ₄ .
• - According to the electrolysis reaction equation 2H ₂ O → 2H ₂ + O ₂ 2 moles of H _{2 are formed} with an enthalpy of formation of 0.079 kWh / (2 mol H ₂ ) or 39.5 MWh / (t H ₂ ). However, according to the reaction equation CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O, methanation requires 4 mol of H ₂ to produce 1 mol of CH ₄ . This results in a theoretical minimum requirement of 2 × 0.045 = 0.09 million t / a H ₂ with a calorific value of 3.2 TWh / a. Based on a power consumption of 53.6 MWh / t H ₂ and an electrolyzer efficiency of 74%, the real electrical energy requirement for a correspondingly efficient electrolysis plant reaches 4.3 TWh / a. With efficiencies of the electrolysis below 70% results in an electrical energy requirement of over 4.6 TWh / a.
• - Providing electrical energy alone for cement production of 830-908 kWh / t of cement results in a cost block based on an output of 0.7 million t of cement and a mean delivery price of 50 EUR / MWh of around EUR 30 million. With a cement price of between 127 and 139 EUR / t, the proceeds from the cement amount to approximately 100 million EUR.
• - The costs for the electrical energy demand in an advanced electrolyzer 53.6 MWh / t H ₂ result in 0.09 million t H ₂ and the resulting energy demand of 4.3 TWh / a the dominating cost block of 215 million EUR.
• - The cost of process water for electrolysis (0.8 million tonnes) is estimated at EUR 2 / t H ₂ O at EUR 1.6 million (excluding water recovery from the process).
• - The marketable as industrial gas oxygen comes to the amount of 0.7 million t and represents a revenue potential of 70 million EUR at oxygen prices of 100 EUR / t O ₂ , at 140 EUR / t of about 100 million EUR. The main consumer of industrial oxygen is the steel industry. Currently the most common production method for the most important industrial gases from the air is the cryogenic air separation, which also supplies valuable noble and trace gases. In this respect, the electrolysis oxygen can also significantly relieve the steel industry in terms of its CO ₂ obligations when using the electrolysis EE oxygen.
• - Methanation has an output of 0.18 million tonnes of CH ₄ , resulting in a methane revenue potential of € 65.5 million assuming a natural gas price of € 26 / MWh (€ 0.36 / kg) or at one Potential of EUR 151 million assuming a gas price of EUR 60 / MWh (EUR 0,84 / kg). The methane can be fed to gas stations for mobile applications.
• - The current total storage capacity of the German natural gas infrastructure of approximately 200 TWh should be sufficient for use as storage for the volatile excess electricity volumes in the form of EE-PtG-H ₂ (PtG = power-to-gas) and EE-PtG methane be.
• - Due to the modular structure of electrolysis systems and the systemic decoupling of electrolysis and methanation is compared to systems for complex process engineering processes relatively easy to expand and, inter alia, by switching modules unsteady working electrolysis system as surplus current sink available. The generated hydrogen can be fed into the natural gas grid as well as used for further methanation. The capacity of methanation is determined by the CO ₂ supply of cement production.
• - For the here determined need of 4.3 TWh for the electrolysis and, for example, a transmission by means of a double system 380 kV three-phase line with 3.5 GW transmission capacity results in a minimum feed time of about 1200 h with a corresponding absorption capacity of the electrolysis plant at least 3.5 GW. By maintaining the bridging time during the surplus phases of the renewable energy supply of 14 days or 336 h, this results in approximately four times the line capacity and four times the absorption capacity of the electrolyzer, each with a necessary 15 GW. With an estimated total storage requirement of 15 TWh and 14 days bridging time, 3 to 4 such installations would be required in Germany with a total capacity of 45 GW. An adequately dimensioned electrolysis plant can absorb surplus quantities occurring in the near-consumer coupling with the natural gas grid in the short term.
• - The overall balance (inevitably subject to uncertainty) makes the economic viability of the procedure look promising.
• As a preferred utilization path, the generated EE-PtG methane (PtG = power-to-gas), possibly enriched with hydrogen (currently limited to 2% by volume for internal combustion engines) in compliance with the natural gas network specifications, will be used at an assumed specific Gas consumption / vehicle of 3 kg of methane / hydrogen mixture / 100 km with a calorific value of more than 15 kWh / kg mixed gas to supply approx. 400,000 gas vehicles with an annual mileage of 15,000 km. Thus, for example, the car population of the city and the Hanover region can be operated sustainably.

Advantages of the invention:

• - The present concept of the generation of EE-PtG methane by EE electricity and the use of the stored in the limestone CO ₂ emissions, which are released in the cement production and used for RE methane, combine the best of the three worlds electricity , Gas and mobility as well as hydrogen find their place in this system, without having to develop and build up an additional and complex hydrogen infrastructure to the natural gas network. The associated with disadvantages storage of CO ₂ (carbon capture and storage, CCS) is hereby obsolete
• - Sustainable mobility, which used to be limited to niche approaches, now has a mass and system compatible renewable energy base that has been tried and tested in the vehicle.
• - The expansion, including the repowering of the renewable energies wind and photovoltaics, can be further promoted with regard to the sensible use of the collected energy using the storage possibilities shown here.
• - Economic factors for the concept are not only the short-term storage of surplus electricity in the natural gas network in the form of EE-H ₂ or EE methane and the marketing this of the fuels (especially EE-PtG methane with increased H ₂ content). By the potential of the fuel market is a useful option for the fuel supplier or the vehicle manufacturer to use the EE PtG methane amounts and proportions of EE PtG H ₂ amounts under CO ₂ -Minderungsstrategie as Dekarbonisierungsmaßnahme.
• - The available quantities of CO ₂ are present due to the existing capacities of the basic industries, in particular cement production and the steel industry, especially in Germany.
• For example, all cement plants in Germany, based on 10 million tonnes of CO ₂ as process emissions, could sustain the sustainable operation of 8 million gas vehicles and the integrated iron and steel plants based on an assumed 25 million tonnes of CO ₂ as unavoidable process emissions 20 million gas vehicles on an annual basis.

LIST OF REFERENCE NUMBERS

100

Plant for the production of a hydrocarbon

11

first production process / first process reactor / calcination / iron smelting

12

second production process / second process reactor / methanation

13

raw material storage

14

product memory

15

CO ₂ storage

16

Hydrogen storage

17

Hydrocarbon storage / methane storage

18

oxygen storage

19

electrolysis process

20

water-tank

21

Oxy-fuel process / oxy-fuel reactor

22

CO ₂ separation stage or CO / CO ₂ separation stage

EE

Electric power from regenerable / renewable energy

Q

warmth

RM

Raw material / raw material

P

product

CH ₄

methane

CO ₂

carbon dioxide

HC

Hydrocarbon

H ₂

hydrogen

O ₂

oxygen

H ₂ O

water

CaCO ₃

 Calcium carbonate / limestone

CaO

Calcium oxide / burnt lime

Fe

Iron (pig iron)

FeO _X

Iron oxides (iron ore)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010/069622 A1 [0004]
• DE 102013010909 B3 [0005]

Claims (10)

Process for producing a hydrocarbon (HC), comprising: - a first production process ( 11 ), in which a raw material (RM) is converted in an endothermic reaction to a product (P) and carbon dioxide (CO ₂ ), and - a second production process ( 12 ), in which in the first production process ( 11 ) converted carbon dioxide (CO ₂ ) in an exothermic reaction with hydrogen (H ₂ ) to obtain the hydrocarbon (HC), characterized in that the first and the second production process ( 11 . 12 ) are coupled to one another in the second production process ( 12 ) released thermal energy (Q) the first production process ( 11 ) is supplied to at least partially cover its energy needs. Method according to claim 1, characterized in that in the second production process ( 12 ) used hydrogen (H ₂ ) from an electrolysis process ( 19 ) is won. Method according to claim 1 or 2, characterized in that the first production process ( 11 ) Oxygen (O ₂ ) is supplied as a reactant or as an oxidant for a fuel and the oxygen (O ₂ ) from an electrolysis process ( 19 ) is won. Method according to one of the claims, further comprising an oxyfuel process ( 21 ), in which a fuel is burned by means of enriched or pure oxygen (O ₂ ), wherein one in the oxyfuel process ( 21 ) released thermal energy (Q) at least partially the first production process ( 11 ) is supplied for at least partially covering its energy needs and / or wherein in the oxyfuel process ( 14 ) generated carbon dioxide (CO ₂ ) the second production process ( 12 ) is supplied. A method according to claim 4, characterized in that the oxyfuel process ( 21 ) used oxygen (O ₂ ) from an electrolysis process ( 19 ) is won. Method according to one of claims 2, 3 or 5, characterized in that the electrolysis process ( 19 ) comprises the electrolysis of water (H ₂ O), in particular using electricity from regenerative energies. Method according to one of the preceding claims, further comprising a CO ₂ separation process ( 22 ), in which the carbon dioxide (CO ₂ ) before being fed to the second production process ( 12 ) is separated from other components. Method according to one of the preceding claims, characterized in that in an exhaust gas of the second production process ( 12 ) contained water at least partially the electrolysis process ( 19 ) is supplied. Method according to one of the preceding claims, characterized in that the first production process ( 11 ) - calcination of limestone, in which limestone (CaCO ₃ ) as raw material (RM) is converted in an endothermic reaction to lime (CaO) as product (P) and carbon dioxide (CO ₂ ), or - comprises smelting of iron ore , in which iron ore is converted as raw material (RM) in an endothermic reaction to pig iron as product (P) and carbon dioxide (CO ₂ ). Investment ( 100 ) for producing a hydrocarbon (HC), comprising: - a first process reactor ( 11 ), which is set up to convert a raw material (RM) into a product (P) and carbon dioxide (CO ₂ ) in an endothermic reaction, and - a second process reactor ( 12 ), which is set up in the first production process ( 11 ) converted carbon dioxide (CO ₂ ) in an exothermic reaction with hydrogen (H ₂ ) to obtain the hydrocarbon (HC), characterized in that the first and the second process reactor ( 11 . 12 ) are coupled to one another in the second process reactor ( 12 ) released thermal energy (Q) the first process reactor ( 11 ) is supplied to at least partially cover its energy needs.

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