JP2002527539A - Method for converting hydrogen to alternative natural gas - Google Patents

Abstract

The present invention relates to a method for producing methane-rich product gas (SNG, synthetic natural gas). Biomass and / or fossil fuel is supplied to the hydrogasification reactor along with hydrogen from an external source. The reaction product from the hydrogasification reactor is converted to 40 to 45 MJ / m ³ (stp), preferably 42 to 45 MJ / m ³ (stp) in the methanation reactor. It is converted to SNG having a Wobbe index and having a methane mole percentage of at least 75%, preferably at least 80%. The generated SNG can be delivered to consumers via the existing gas grid without any problems and can be used in existing facilities. The process according to the invention can be handled using a very compact methanation reactor with a small number of parts. In the long term, where hydrogen from electrolysis methods via a sustainable source becomes important, the method according to the invention provides a method for upgrading biomass and organic waste with hydrogen to produce SNG. Form a preferred approach. However, in the short term, hydrogen can be obtained from fossil sources.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for supplying biomass and / or fossil fuel to a first reactor to produce a gaseous reaction product, and transferring the reaction product from the first reactor to a methanation reactor. Supplying a methane-rich product gas (S) in the methanation reactor, comprising converting the supplied gaseous reaction product to a methane-rich product gas.
NG, synthetic natural gas).

[0002] Hydrogen will play an important role in future sustainable energy sources. Transporting and storing hydrogen in its free form (H ₂ ) is much more complicated than transporting and storing hydrogen stored chemically, for example in the form of methane,
And certainly will require much more energy. An additional advantage of using hydrogen indirectly as an energy source would be that (part of) existing large-scale energy infrastructure structures, such as natural gas grids, could still be used. One possible method for storing hydrogen in chemically bound form is the hydrogasification of carbon-containing compounds such as biomass and waste.
drogasification). Thermal decomposition of these compounds in an H ₂ atmosphere is capable of generating raw natural gas.

[0003] EP-A-0696951 discloses that biomass, organic waste or fossil fuels have a high methane content in a hydrogasification reactor with the addition of hydrogen and a gas with small amounts of carbon dioxide. It discloses that it can be converted to a mixture. In a second method step, the gas mixture is converted into synthesis gas in a steam reformer, and the synthesis gas is converted in a third method step into methanol in the presence of a Cu / Zn-based catalyst known per se. Is converted to The hydrogen remaining in the final step is passed to a hydrogasification reactor. This method is only suitable for producing methanol.

From US Pat. No. 3,922,148, a method according to the preamble of claim 1 is known.
Where the oil is converted to synthesis gas with the addition of steam and oxygen.
This syngas is converted to 99 mole% methane and 0
. It is converted to a product gas containing 8 mol% hydrogen. High CO / CO of synthesis gas _Two Due to the concentration, a relatively large number of methanation reactions are required to convert this syngas to methane.
Requires a rectifier. In addition, in order to produce syngas,
The combustion of the oil occurs and supplies heat. Relatively large heat loss in methanation reactor
Due to the loss, the efficiency of this known method is low.

[0005] It is an object of the present invention that hydrogen can be stored efficiently and economically in chemically bonded form, the carbon monoxide present in the synthesis gas produced is relatively low, and the process is simple and easy. It is to provide a process where a relatively small methanation reactor is sufficient. For this purpose, the process according to the invention provides that the first reactor comprises a hydrogasification reactor supplied with hydrogen, wherein the hydrogen is derived from an external source, and that the product gas (SNG) is , Having a Wobbe index of 40 to 45 MJ / m ³ (stp), preferably 42 to 45 MJ / m ³ (stp),
And characterized by having a methane mole percentage of at least 75%, preferably at least 80%.

Here, the “external” source is not formed by the methanation reactor, but is independent of the methane production method according to the invention and is provided independently to the hydrogasification reactor for the electrolysis of hydrogen, for example for water, for the light hydrocarbons. Hydrogen produced by steam reforming, hydrogen produced by partial participation of heavy hydrocarbons such as oil and coal, or chlorine production by membrane or membrane cells, methanol production, industrial processes such as acetone, isopropanol or methyl ethyl ketone Hydrogen or a source that supplies hydrogen from a blast furnace.

[0007] supplying an external hydrogen hydro gasification reactor, Wobbe index, CH ₄ mole percent and very close Wobbe index to the calorific value of natural gas (e.g., Groningen (Groningen) natural gas), CH ₄ Since it is possible to obtain a product gas having a molar percentage and a calorific value, the generated SNG can be distributed to consumers via existing gas grids without any problems and can be used in existing facilities. Proven that can be done. At the same time, the process according to the invention can be handled using very compact methanation reactors with a small number of parts, while the reduction in the amount of tar formed (as compared to other gasification schemes) is also One of the options.

[0008] In the long term, when hydrogen from an electrolysis process via a sustainable source becomes important, the process according to the invention uses hydrogen to upgrade biomass and organic waste to produce SNG. To form a suitable approach to However, in the short term, hydrogen can be obtained from fossil sources. This practical application is provided by the following example.

According to an advantageous embodiment of the process according to the invention, the hydrogen is, for example, Lynum,
R. Hillum, K .; Hox, J.M. Hugdahl Bulletin of the 12th World Hydrogen Energy Congress, Vol. I, pp. 637-645, 1998, Kvaerner-based Technology for the Production of Green Energy and Hydrogen (Kvaerner
Based Technologies for Environmentally Friendly Energy and Hydrogen Pro
duction, Proceedings of the 12th World Hydrogen Energy Conference, vol.
I, pp. 637-645, 1998) by thermal decomposition in a plasma reactor by the CB & H method. This plasma method produces hydrogen and pure carbon from natural gas.

The present invention will be described in more detail with reference to the accompanying drawings, in which FIG. 1 shows a schematic diagram of a method for producing a methane-rich product gas (SNG) according to the present invention, Shows a schematic diagram of the process according to the invention in which hydrogen for hydrogasification is obtained from a plasma process.

FIG. 1 schematically shows a process flow for producing a substitute natural gas according to the present invention. The biomass is passed through the dryer 2 via the feeder 1. The biomass can include wood chips, plant waste or other organic hydrocarbon sources. Like biomass, it is also possible to supply fossil fuels to the hydrogasifier 3, in which case no drying step is required. The biomass is converted to the hydrogasifier 3 at the operating pressure (for example, 30 bar) present at the site.
For injection into the CO ₂ via the inlet line 4 'is introduced into the biomass supply line 4. Hydrogen is supplied from an external hydrogen source to the hydrogasifier via the supply line 5. The hydrogen source can include hydrogen electrolysis or be derived from an industrial process in which hydrogen is produced as a by-product.

At the outlet 6 of the hydrogasifier 3, gaseous reaction products are withdrawn from the hydrogasifier, the main component of which is CH ₄ , CO, H ₂ , CO ₂ and H ₂ O
Also exists. This gas mixture is supplied to a high-temperature gas purifier 7 via a heat exchanger 9 to remove solid residues and gaseous impurities such as H ₂ S, HCl, HF and NH ₃ from the synthesis gas. Solid residues from the hydrogasifier 3 are removed via a discharge line 8. Via a line 10 and a heat exchanger 11, the purified methane-rich gas mixture is fed to a methanation reactor 12, where the methane-rich gas mixture is converted to alternative natural gas (SNG), which comprises a heat exchanger 14 And through a water separator 15 to a discharge line 16. The alternative natural gas can then be injected into an existing gas grid for delivery to end users.

The heat extracted from the methane-rich gas mixture at the outlet 6 and at the line 10, and the heat extracted from the product gas at the outlet 13, via the heat exchangers 9, 11 and 14 to the steam generator 19. The supplied steam is supplied to a steam turbine 20 which drives the generator 17 to produce electricity.
This condensed steam is recirculated from the steam turbine 20 via the return line 22 to the inlet of the steam generator 19. The portion of the low pressure steam from the steam turbine 20 heats the dryer 2 via the heat exchanger 18. Heat exchanger 18
The low-pressure steam that has passed through is supplied to a steam generator 19.

In the hydrogasifier 3, the following reactions occur, inter alia: C + 2H ₂ ← → CH ₄ (1) CO + 3H ₂ ← → CH ₄ + H ₂ O (2) 2CO ← → C + CO ₂ (3) CO + H ₂ O ← → CO ₂ + H ₂ (4) If no hydrogen is supplied in thermodynamic equilibrium at a constant temperature (T = 800 ° C.), the pressure rise in the reactor is: discharged via the discharge line 6 increase in the concentration of reduced and CH _4, CO ₂ and H ₂ O CO and H ₂ concentration in the synthesis gas, - reduction in the conversion of oxygen from the biomass, and - the reduction of heat required in the reactor 3 Bring.

The above reaction number (4), which is a water gas shift equilibrium, is independent of pressure, while other reactions shift to the right with increasing pressure and are exothermic in that direction.

At a higher operating temperature, at a pressure P = 30 bar, if no hydrogen is supplied and in thermodynamic equilibrium, the four equilibrium reactions shift to the left and are discharged via the discharge line 6. that a decrease in gain and CH _4, CO ₂ and H ₂ O concentration of CO and H ₂ concentration in the synthesis gas, - an increase in the conversion of oxygen from the biomass, and - an increase of the heat required for the reactor 3 Results.

Only at temperatures below 550 ° C. does the process become autothermal.

In the thermodynamic equilibrium, the supply of hydrogen at T = 800 ° C., P = 30 bar has the following effects on the hydrogasification process in the hydrogasifier 3: the increase in the methane concentration and the reaction (1 ) And (2), resulting in a decrease in heat demand, a decrease in CO concentration according to reaction (2), and an increase in carbon conversion according to reaction (1).

If hydrogen is supplied via the supply line 5 to an amount of 75 mol / kg biomass (without moisture), the synthesis gas produced in the hydrogasifier 3 will be 2
It contains 9% by volume of methane and 7% by volume of CO and has a biomass carbon conversion of 78%.
% And the heat demand is 1.2 MW _th / kg biomass (water free).
Whenever reference is made hereinafter to biomass, it refers to biomass that does not contain water. 7
An increase in operating pressure T = 800 ° C. in a hydrogen supply of 5 mol / kg biomass results in an increase in carbon conversion, since reaction (1) then prevails.

In the following, a more detailed description of the process parameters in the hydrogasifier 3, the hot gas purifier 7 and the methane reactor 12 will be given, with these parameters representing the alternative natural gas ( SNG) constitutes the basis for calculating the composition. The calculation was based on biomass in the form of ordinary sawdust having the composition shown in Table 1.

[0021]

[Table 1] In the computational model, the hydrogasifier 3 was operated at a temperature of 800 ° C. and a pressure of 30 bar. In this setting, it is possible to obtain a biomass carbon conversion of 89% with a hydrogen supply of 75 mol / kg biomass, assuming certain variations from the thermodynamic equilibrium, and the process is autothermal. It is. However, the supplied biomass is not water-free, and the hydrogasifier 3 is supplied with additional CO ₂ , so the hydrogen supplied to the model will be used to make the process autothermal. It was increased from 75 to 100 mol / kg biomass. In this setting, the expected conversion of carbon from biomass is 83%.

The gaseous products from the hydrogasifier 3 are passed through exchangers 9 and 11
In two steps, it is cooled from 850 ° C. to 400 ° C. to the inlet temperature of the first methanation reactor. In this temperature range, high temperature gas purifier 7, the solid residue and H ₂
Gaseous contaminants such as S, HCl, HF, NH ₃ can be used to remove from synthesis gas.

The methanation reactor 12 is based on M. V. Based on the ICI high-temperature single-pass process described in Catalyst Handbook, 2nd Edition, ISBN 1874545359, 1996, edited by Twig. This uses a series of reactors operating at a continuously decreasing outlet temperature.

The steam generator 19 generates superheated steam at a pressure of 40 bar. The heat from the cooling of the methane-rich syngas from the methanation reactor 12 and through heat exchangers 9 and 11 is used to generate steam in the model, while the methane-rich gas mixture in lines 6 and 10 The heat released during the cooling of was used to overheat the steam. The resulting steam was expanded to 0.038 bar in two steps (40 to 10 bar in the first step and 10 to 0.038 bar in the second step).

Based on the above method settings, the material and energy balances of the system according to FIG. 1 were calculated using the ASPEN PLUS process simulation program. Table 2 shows the physical properties of Groningen natural gas (NG) and synthetic natural gas (SNG) produced by the hydrogasification method according to FIG. Very importantly, the calorific value and Wobbe index of synthetic natural gas in MJ / kg are substantially identical to those of natural gas. This makes it possible to inject the product gas produced by the hydrogasification process according to FIG. 1 directly into the natural gas grid and burn it using existing equipment.

[0026]

[Table 2] Cubic meters (m ³ [s.m.) at standard temperature and pressure at 0 ° C. and 1 atm.
t. p. The Wobbe index (MJ / m ³ [STP]]) is the ratio of the high calorific value to the square root of the relative density of the gas. This Wobbe index is calculated by the following formula:

(Equation 1)(Where HHV is MJ / m^Three[S. t. p. ] Unit high calorific value, ρ_gAnd ρ _air Is kg / m^ThreeThe density of gas and air in (stp) units
). The Wobbe index is the energy delivered to the burner by injection.
It is a measure of the amount of lug. Two with different compositions but with the same Wobbe index
The gases provide the same amount of energy at the same injection pressure, given a given injection direction.
Offer.

FIG. 2 illustrates an embodiment of a method according to the present invention, wherein hydrogen is converted to R.C. A. Wijbr
and J. Ans. M. van Zutphen, D.M. H. Recter, "Using Carbon Black and Hydrogen Process to Add New Hydrogen to Existing Gas Infrastructure in the Netherlands, Proceedings of the 12th World Hydrogen Energy Conference", Volume II, 96
3-968, 1998 ("Adding New Hydrogen to the Existing Gas Infra
structure in the Netherlands, Using the Carbon & Hydrogen Process, Proce
edings of the 12th World Hydrogen Energy Conference ", vol. II, pp. 963-9
68, 1998) according to the CB & H method. Here, natural gas is supplied via a supply line 23 to a plasma reactor 24, where the plasma is generated by the supplied electrical energy, producing hydrogen and carbon. Heat exchanger 2
5 and the separator 26, the carbon in the known CB & H process is discharged and pelletized, packaged, and hydrogen is injected into the natural gas grid after passing through a compression and injection unit 27. According to the invention, the hydrogen is passed to the hydrogasification process via the supply line 5 instead of the compression and injection device 27.
Generating hydrogen from natural gas using a high temperature plasma method in combination with hydrogasification means that the CB & H method purifies pure carbon and reduces the calorific value as a result of the conversion of natural gas to hydrogen. 100% by the reverse reaction of hydrogen to produce SNG
Has the advantage of being compensated for over This therefore ensures that fossil carbon disappears from the chain, while persistent carbon is supplied from biomass with a total gain in energy by introducing biomass to an amount of approximately 60%. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a method for producing a methane-rich product gas (SNG) according to the present invention.

FIG. 2 is a schematic view of a method according to the invention in which hydrogen for hydrogasification is obtained from a plasma method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Feeder 2 ... Dryer 3 ... Hydrogasifier 4,5 ... Supply line 4 '... Injection line 6 ... Outlet of hydrogasifier 7 ... High-temperature gas purification device 9,11,14,18,25 ... Heat exchanger DESCRIPTION OF SYMBOLS 12 ... Methanation reactor 15 ... Water separator 19 ... Steam generator 20 ... Steam turbine 23 ... Supply line 24 ... Plasma reactor 26 ... Separator 27 ... Compression and injection equipment

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] November 10, 2000 (2001.10.10)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

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Claims (9)

[Claims] Claims 1. A biomass and / or fossil fuel is supplied to a first reactor to produce a gaseous reaction product, and the reaction product is supplied from the first reactor to a methanation reactor. A method for producing a methane-rich product gas (SNG, synthetic natural gas) comprising converting the supplied gaseous reaction product into a methane-rich product gas in the methanation reactor. Wherein the first reactor comprises a hydrogasification reactor supplied with hydrogen, wherein the hydrogen is derived from an external source and the product gas (SNG) is 40-45 MJ / m ³ ( S.T.P.), preferably has a Wobbe index of 42~45MJ / m ³ (s.t.p.), and at least 75%, preferably a wherein a Metanmoru percentage of at least 80% Said method. 2. The method of claim 1, wherein the product gas (SNG) has a heating value that is compatible with the heating value of natural gas. 3. The method according to claim 1, wherein the product gas is injected into a natural gas pipeline system and delivered to a consumer. 4. The hydrogasification reactor is operated at a temperature of 500 ° C. to 1500 ° C., preferably 750 ° C. to 850 ° C., at a pressure of 15 bar to 200 bar, preferably 20 bar to 40 bar. The method according to claim 1, 2 or 3, wherein 5. The process according to claim ₄ , wherein CO ₂ is introduced as a carrier gas into the biomass or fossil fuel and injected into the hydrogasification reactor. 6. The amount of hydrogen supplied to the hydrogasification reactor is controlled such that the hydrogasification in the hydrogasification reactor proceeds at least essentially autothermally. The method according to any one of claims 1 to 5. 7. The process according to claim 6, wherein 50 to 125 moles of hydrogen per kg of water-free biomass are fed to the hydrogasification reactor. 8. The method according to claim 1, wherein the heat generated in the methanation reactor is supplied to a steam generator. 9. The method according to claim 1, wherein the hydrogen is produced from natural gas by pyrolysis in a plasma reactor.