DE102009014728A1 - Method of operating a fossil fuel power plant and fossil fuel power plant with reduced carbon dioxide emissions - Google Patents

Abstract

The invention relates to the utilization of carbon dioxide from power plants that work with fossil fuels. Here, for the first time, carbon dioxide is decomposed via the introduction of the power plant exhaust gas into a high-voltage reformer.

Description

The Invention relates to the utilization of carbon dioxide from power plants, who work with fossil fuels.

It was recognized that the unchecked carbon dioxide emissions for the environment leads to significant damage. Therefore is increasingly being invested in carbon dioxide-neutral energy production, However, in the medium term, the complete replacement of the power plants, use the fossil fuels, not foreseeable.

Currently powered fossil fuel-based power plants of all types have no mechanism to avoid carbon dioxide emissions, as the combustion of carbonaceous energy sources inevitably generates carbon dioxide gas as an oxidation product (I). According to the legally prescribed flue gas desulphurisation in Europe, the hot exhaust gas is led into the ambient air after the power generation process. C + O ₂ → CO ₂ (I)

To avoid further accumulation of carbon dioxide in the atmosphere by fossil-fueled power plants, there are basically two methodologies that are currently only the subject of research. In the so-called oxyfuel process fossil fuel is burned with pure oxygen of an upstream air separation with energy gain and the flue gas after flue gas desulfurization by compressor in a liquid-like ("supercritical") form converted and stored. In the so-called IGCC ("Integrated Gasification Combined Cycle") process, fossil fuel is substoichiometrically converted with pure oxygen from a previous air separation step to volatile, combustible synthesis gas and finally reacted with water to form carbon dioxide and hydrogen ("water gas shift") ( Eqs 2-4). 2C + O ₂ → 2CO (II) C + H ₂ O → CO + H ₂ (III) CO + H ₂ O → CO ₂ + H ₂ (IV)

To The separation of carbon dioxide serves as a combustible hydrogen Energy sources, whereas carbon dioxide, as in the case of Oxyfuel process, compressed and for later use can be stored. In summary, the avoidance of Carbon dioxide emissions and thus hoped for climate with simultaneous effective energy production by upstream or downstream Carbon Dioxide Separation Process ("Pre- and Post-Combustion Carbon Capture ").

Disadvantage of all these methods is the high energy consumption for providing pure oxygen from the cryogenic air separation, the carbon dioxide separation and storage by means of compression and, finally, the question of the fate and using the accumulated in this way the carbon dioxide, wherein the medium is allotted special interest of underground or undersea sequestration ^{[ 5]} .

Therefore It is the object of the present invention to provide a method for modification all power plant concepts based on fossil fuels to reduce the generated carbon dioxide gas.

solution The object and subject of the invention is therefore a method to run a power plant that burns out coming and enriched with carbon dioxide gas in a reformer is initiated, in which it is exposed to a high voltage field. In addition, the subject of the invention is a power plant, a combustion furnace, a gas / steam generator and a connected turbine To summarize, characterized in that lines are provided, through which part of the electricity generated in the turbine into one High-voltage transformer is passed and provided additional lines by which are enriched with carbon dioxide and hydrocarbon Exhaust from the power plant process led to a reformer wherein the generated high voltage in the reformer is a high voltage field produced by the carbon dioxide and a hydrocarbon-containing Gas, converted into carbon monoxide and hydrogen.

Fundamental realization of the invention is that while established and future Kraftwerkstech In order to separate carbon dioxide gas or to store it in liquid form or to make it accessible to sequestration, a value-creating conversion of the carbon dioxide formed is advantageous. The conversion is done by means of high voltage field even at atmospheric pressure and at moderate temperatures. The result is chemical substances that contain the fossil carbon after the energy recovery step immobilized in high quality chemicals. Thus, for the purposes of the present invention, the possibility of use by further processing and / or conversion in subsequent chemical processes instead of storage or discharge into the atmosphere.

The carbon monoxide gas formed in value-added processing takes place via established and new procedures / techniques and allows at the same time a saving or avoidance of 50-100% of the carbon dioxide formed during the combustion process. The chemicals formed in the value-creating process On the one hand, they can be used for power generation or other purposes chemical and / or physical work steps are used. The necessary energy input for the transformation of carbon dioxide consumed in the desired products in this measure for a value-creating one Process instead of in the case of the above storage or sequestration for a deficient use of the fossil Combustion products.

The carbon dioxide gas (I) formed during the combustion of fossil carbon-based energy carriers is converted according to the present invention in a so-called reforming process ("reforming") with natural gas, most advantageously with methane CH ₄ , with the introduction of energy to synthesis gas (V). CO ₂ + CH ₄ → 2CO + 2H ₂ (V)

So far, high temperatures and high process pressures to achieve sufficient conversion are proposed for this transformation. According to an advantageous embodiment of the invention, however, with the aid of pulsed electrochemical methods in the flow reactor even at low temperatures, for example from 5 ° C to 300 ° C, in particular from 15 ° C to 200 ° C and particularly preferably from 25 ° C to 150 ° C, for example, even under normal pressure, a material conversion of 85% or more in the main components with a simultaneous energy efficiency of over 80%, based on the introduced electrical power detectable. There are examples in the literature such as S. Kado; K. Urasaki, Y. Sekine, K.Fujimoto: Low temperature reforming of methane to synthesis gas with direct current pulse discharge method, Chem. Commun. 415-416 (2001) ; Y. Sekine, K. Urasaki, S. Kado, M. Matsukata, E. Kikuchi: Nonequilibrium Pulsed Discharge: A Novel Method for Steam Reforming of Hydrocarbons or Alcohols, Energy Fuels, 18 (2), 455-459, (2004) ; and Y. Sekine, K. Urasaki, S. Kado, M. Matsukata, E. Kikuchi: High-Efficiency Dry Reforming of Biomethane Directly Using Pulsed Electric Discharge at Ambient Condition, Energy & Fuels, 22, 693-694 (2008) described.

The necessary electricity is at the power plant site without transmission losses available for implementation according to V.

According to an advantageous embodiment of the invention, the composition of the exhaust gas for the reaction in the reformer is optimized by the addition of further gases. For example, the residual oxygen concentration of the exhaust gas from fossil combustion (Equation I) is further increased by further supplying and burning fuel gas, e.g. As methane CH ₄ , or the proportion of fuels in advance adjusted accordingly that the value-creative conversion of carbon dioxide to V is followed, is improved in yield and speed.

Also can be a separation of the atmospheric nitrogen for higher Turnover be advantageous.

To In one embodiment, any desulfurization is eliminated or drying the combustion gas before the value-creating Transformation process according to V.

The synthesis gas formed, which can be varied in its stoichiometry by varying the Eduktkonzentrationen and water content, allows the conversion in subsequent value-creative reaction steps according to established technical processes to useful chemicals (Eq VI and VII). CO + 2H ₂ → CH ₃ OH (VI) 2CO + 4H ₂ → CH ₃ OCH ₃ + H ₂ O (VII)

According to the pulsed-electrochemical process according to V, a separation and recycling of hydrogen formed to produce energy is conceivable (VIII). 2H ₂ + O ₂ → 2H ₂ O (VIII)

Formed carbon monoxide to V can also technically easily separated and other chemical processes, eg. B. Fischer-Tropsch reactions or the plastic-producing industry. In this way, the energy content of supplied hydrocarbons, such as. B. CH ₄ , a reali sible at very low temperatures and atmospheric pressure, electrochemical conversion of carbon dioxide into industrial precursor substances according to V, which are available for further value-creating reaction steps. According to VI and VII, it is still possible to prepare high-energy energy carriers or industrial chemicals which, in contrast to conventional accumulation in the so-called "pre- or post-combustion carbon capture" process and subsequent sequestration, have added value or as chemical building blocks for To be available. In this way, it is still possible to operate low-carbon (50% avoidance) or carbon dioxide-free (100% avoidance) energy production.

• Methan flüssig: ~2300 EURO/t
• Wasserstoff flüssig: ~13000 EURO/t (Hinweis: 1 t Wasserstoff entspricht 11891 m³)
• CO gasförmig: ~6000 EURO/t (Hinweis: Versorgung mittels CO-Trailer im Wechsel)
• CO₂ fest (Trockeneis): 700 EURO/t

In addition, there are economic benefits in the conversion of carbon dioxide, as shown by the following price estimates of selected educts and products:

• Methane liquid: ~ 2300 EURO / t
• Hydrogen liquid: ~ 13000 EURO / t (Note: 1 t hydrogen corresponds to 11891 m ³ )
• CO gaseous: ~ 6000 EURO / t (Note: supply via CO trailer in alternation)
• CO ₂ solid (dry ice): 700 EURO / t

in principle is any combustion process of fossil fuels by the method for carbon dioxide prevention according to V.

in the The invention will become more apparent from the following figures explains:

1 schematically represents the process to be developed.

2 shows a schematic representation of an exemplary high voltage reformer according to the invention

3 shows possible reactions of the reactant

1 shows a reformer formed as a gas flow reactor in which the combustion gas from the turbine and the reforming gas are supplied. At the same time, the mixing takes place to the reformable gas mixture, which then undergoes the conversion according to II in the high voltage field under standard pressure and moderate temperature to carbon monoxide and hydrogen.

2 shows the conversion according to V in a high-voltage pulsed electric field.

3 shows the options Route A and Route B, how the product from the reformer can be used.

After the electrochemical reforming according to V, the reactant mixture can be used in further steps (routes A, B; 3 ) are treated in a value-creating manner. Route A describes the synthesis of methanol ("MeOH") or dimethyl ether ("DME") on suitable catalysts. For the methanol synthesis, main group metal oxides, transition metal oxides or mixtures thereof are expediently used, whereas, inter alia, transition metal-doped, acidic zeolite variants are used for the dimethyl ether synthesis.

As a basis for the energy yield consideration, the standard reaction enthalpies of the reactions according to Eqs. 1-8 (Table 1). Tab. 1: Standard reaction enthalpies

For determining the energy balance of the resulting conversion to V, the enthalpy of combustion AH ° R the reforming reactants used, for. Methane CH ₄ , critical IX. Taking into account the efficiency of the pulsed, electrochemical conversion to V (η = 85%), the energy required for the reforming is 1.15 · 247 kJmol ^-1 = 284 kJmol ^-1 (X)

Example 1: Calculation of an energy balance according to the method of a coal power plant operation according to the invention: Route A methanol, dimethyl ether synthesis:

Coal-fired power plants are still widespread in Germany. For carbon dioxide avoidance with subsequent fixation in Nutzchemikalien according to an embodiment of the invention, the separate supply of natural gas ("lean of the power plant exhaust gas") is advantageous. The energy balance results after combination of Gln. I, V, VI and VII, respectively: C + O ₂ → CO ₂ -393.8 kJ CO ₂ + CH ₄ → 2CO + 2H ₂ +284.0 kJ CO + 2H ₂ → CH ₃ OH -128.2 kJ 2CO + 4H ₂ → CH ₃ OCH ₃ + H 2 _O -207.4 kJ Energy yield (methanol) -238.0 kJ Energy yield (dimethyl ether) -317.2 kJ

Based to the theoretically maximum exploitable reaction enthalpy I and IX result in energy efficiency of 19% (MeOH) and 25% respectively (DME), as well as the possibility of separated carbon monoxide for further processing.

Example 2: Route B

From the reformer exhaust gas, ie the gas formed in the reformation process, hydrogen formed after carbon monoxide separation can be recycled and utilized as an energy source. For the energy balance results after combination of Gln. I, IV and VIII: C + O ₂ → CO ₂ -393.8 kJ CO ₂ + CH ₄ → 2CO + 2H ₂ +284.0 kJ H ₂ + ½O ₂ → H ₂ O -286.0 kJ energy output -681.8 kJ

Based on the theoretically maximum exploitable reaction enthalpy according to Eq. I and IX results in an energy efficiency of 53% with 100% CO ₂ savings, and again the possibility of separated coals to provide monoxide for further processing.

Example 3: Route A in combination with Water gas shift (IV)

Furthermore, it is conceivable to subject the carbon monoxide separated in route A to the water gas shift according to IV and thus additionally exploit the exothermic nature of this reaction. C + O ₂ → CO ₂ -393.8 kJ CO ₂ + CH ₄ → 2CO + 2H ₂ +284.0 kJ CO + 2H ₂ → CH ₃ OH -128.2 kJ or 2CO + 4H ₂ → CH ₃ OCH ₃ + H ₂ O -207.4 kJ CO + H ₂ O → CO ₂ + H ₂ -41.2 kJ H ₂ + ½O ₂ → H ₂ O -286.0 kJ Energy yield (methanol) -565.2 kJ Energy yield (dimethyl ether) -644.4 kJ

Relative to the theoretical maximum. exploitable reaction enthalpy according to Eq. I and IX results in an energy efficiency of 44% (methanol) -50% (dimethyl ether). Contrary to the provision of carbon monoxide, the water gas shift according to Eq. IV carbon dioxide. The reforming step serves in this case the value creation of methanol or dimethyl ether, but not the net saving of CO ₂ based on I.

Example 4 Calculation using the example of a Gas turbine power plant

(Natural) gas-powered Power plants represent the most advantageous variant for the Implementation is because z. B. Methane on site for the Reformation process according to Eq. 5 is available.

Route A

For the energy balance results after combination of Gln. IX to VII and IX: CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O -890.5 kJ CO ₂ + CH ₄ → 2CO + 2H ₂ +284.0 kJ CO + 2H ₂ → CH ₃ OH -128.2 kJ or 2CO + 4H ₂ → CH ₃ OCH ₃ + H ₂ O -207.4 kJ Energy yield (methanol) -734.7 kJ Energy yield (dimethyl ether) -813.9 kJ

Based to the theoretically maximum exploitable reaction enthalpy IX results in energy efficiency of 41% (methanol) - 46% (Dimethyl ether). In addition, there are valuable industrial chemicals ((methanol / dimethyl ether / CO) available, the other value-creating Processes are available.

Calculation according to route B

It can be recycled after the reformation process after carbon monoxide separation hydrogen formed and used as an energy source. For the energy balance results after combination of Gln. V, VIII and IX: CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O -890.5 kJ CO ₂ + CH ₄ → 2CO + 2H ₂ +284.0 kJ H ₂ + ½O ₂ → H ₂ O -28.0 kJ energy output -1178.5 kJ

Based on the theoretically maximum exploitable reaction enthalpy according to IX results in an energy efficiency of 66%.

additionally stands carbon monoxide as useful chemicals for processing Processes available.

2.3 Route A in combination with water gas shift (IV) It is also conceivable to subject the carbon monoxide separated in route A to the water gas shift according to IV and thus additionally exploit the exothermic nature of this reaction. CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O -890.5 kJ CO ₂ + CH ₄ → 2CO + 2H ₂ +284.0 kJ CO + 2H ₂ → CH ₃ OH -128.2 kJ or 2CO + 4H ₂ → CH ₃ OCH ₃ + H ₂ O -207.4 kJ CO + H ₂ O → CO ₂ + H ₂ -41.2 kJ H ₂ + ½O ₂ → H ₂ O -286.0 kJ Energy yield (methanol) -1061.9 kJ Energy yield (dimethyl ether) -1141.1 kJ

Based on the theoretically maximum exploitable reaction enthalpy according to IX, the energy efficiency is 60% (methanol) - 64% (dimethyl ether). Contrary to the provision of carbon monoxide, the water gas Skift IV produces carbon dioxide. The reforming step serves in this case the value-creating preparation of methanol or dimethyl ether, but not the net saving of CO ₂ based on IX.

The present invention provides a process for reforming carbon dioxide and off-gas from a power plant by means of a high voltage field. The energetically highly efficient, electrochemically-driven and preferably high-voltage pulsed reforming of CO ₂ , there is the possi bility for the first time to operate at room temperature and atmospheric pressure, the conversion of CO ₂ in energetically raised precursor chemicals (carbon monoxide CO and hydrogen H ₂ ). These substances can themselves be converted into valuable energy sources such as liquid methanol or gaseous dimethyl ether. At the same time carbon monoxide accumulates, which can be offered after a separation of about the chemical industry for plastic synthesis, Fischer-Tropsch conversions or other processes. Since power plants, in particular natural gas-fired combined cycle plants, naturally generate large amounts of carbon dioxide by burning fossil fuels, the combination with the planned reforming offers itself in order to prepare useful chemical carbon dioxide under moderate net energy losses. Furthermore, there is the possibility of complete CO ₂ avoidance and thus offers the possibility of carbon dioxide-neutral energy production. In contrast to concepts of "Pre- and Post-Combustion Carbon Capture" with subsequent sequestration allows the planned. Implementation of the ecological and economic use of the resulting carbon dioxide. This therefore also contributes to avoiding the greenhouse gas effect.

The Invention relates to the utilization of carbon dioxide from power plants, who work with fossil fuels. This is the first time over the introduction of the power plant exhaust into a high voltage reformer Degraded carbon dioxide.

1

Coal, Gas, petroleum

2

combustion

3

Gas / vapor-generating

4

power generation in turbine / generator

5

reformer

6

natural gas

7

HV transformer

8th

power supply

9

MeOH / DME synthesis

10

CO scrubber

11

CO storage

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - S. Kado; K. Urasaki, Y. Sekine, K.Fujimoto: Low temperature reforming of methane to synthesis gas with direct current pulse discharge method, Chem. Commun. 415-416 (2001) [0012]
• - Y. Sekine, K. Urasaki, S. Kado, M. Matsukata, E. Kikuchi: Nonequilibrium Pulsed Discharge: A Novel Method for Steam Reforming of Hydrocarbons or Alcohols, Energy Fuels, 18 (2), 455-459, (2004 [0012]
• - Y. Sekine, K. Urasaki, S. Kado, M. Matsukata, E. Kikuchi: High-Efficiency Dry Reforming of Biomethane Directly Using Pulsed Electric Discharge at Ambient Condition, Energy & Fuels, 22, 693-694 (2008) [ 0012]

Claims (7)

Method of operating a power plant with fossil fuels, where the coming from the combustion and with carbon dioxide and hydrocarbon-enriched exhaust is initiated in a reformer in which by applying a high voltage field the gases of the exhaust gas at least partially in carbon monoxide and hydrogen being transformed. The method of claim 1, wherein the high voltage field in the reformer is operated pulsed. Method according to one of claims 1 or 2, in which the reformer is operated under normal pressure. Method according to one of the preceding claims, in which the reformer with temperatures in the range of 15 ° C. operated up to 200 ° C. Method according to one of the preceding claims, in which the composition of the exhaust gas by adding more gases is optimized for implementation in the reformer. Power plant, a combustion furnace, a gas / steam generator and comprising a turbine connected thereto, characterized that lines are provided through which part of the turbine generated current is passed into a high voltage transformer and further lines are provided, through which the carbon dioxide and hydrocarbon enriched exhaust gas from the power plant process in a reformer is performed, the generated high voltage in the reformer generates a high voltage field, by the carbon dioxide and a hydrocarbon-containing gas, in carbon monoxide and Hydrogen is converted. Power plant according to claim 6, in which further lines are provided, the at least a portion of the reformer exhaust gas Process for methanol / dimethyl ether synthesis feeds (A) and / or a portion of the reformer offgas a carbon monoxide scrubber (B) feeds.