JP6103628B2 - Methane reforming method and methane reforming catalyst used therefor - Google Patents

Description

The present invention relates to gasification of solid organic matter such as biomass and coal, and in particular, methane reforming by reacting methane contained in product gas with water vapor that is part of a gasifying agent to reform to H ₂ and CO. The present invention relates to a method and a methane reforming catalyst used therefor.

Biomass and coal gasification is a technology that uses these solid organic substances to produce gas containing H ₂ , CO, CO ₂ , and CH ₄ as main components using a gasifying agent such as water vapor or oxygen in a gasification furnace. is there. The gas generated by gasification can be used as a fuel for a gas engine, and if a catalyst is used, a chemical product such as liquid fuel can be produced from H ₂ , CO, and CO ₂ . Since it can be used as a fuel for transportation vehicles such as automobiles and airplanes, it is in a demonstration stage premised on practical use, and future development is expected.

Gasification methods for solid organic substances such as biomass and coal include fixed bed type gasification, rotary kiln, spouted bed type gasification, and fluidized bed type gasification as those in the practical use stage or demonstration stage.
Fixed bed gasification and rotary kilns were developed early because they are simple in structure and operation and in principle use air as the gasifying agent. However, there are drawbacks such that nitrogen derived from air is contained in the product gas, the amount of tar produced is large, and the composition of the product gas cannot be controlled.
Fluidized bed gasification and spouted bed gasification have been developed relatively recently, and water vapor, oxygen, etc. are often used as gasifying agents, the composition of the product gas can be controlled, nitrogen is not included in the product gas, etc. It has the characteristics of.
These gasification methods differ depending on the use of the solid organic matter to be used and the product gas as follows.

In the case of coal, fixed bed coal gasification may be adopted, but many companies worldwide are adopting spouted bed coal gasification.
Further, in the case of biomass, as reported by Task 33 (Thermal gasification) based on the Bioenergy Agreement of IEA (International Energy Agency), gasification methods are properly used depending on applications.

That is, when the generated gas is burned to obtain heat and power is generated as a fuel for the gas engine, the generated gas only needs to be burned, and there is no need to control the generated gas composition. Therefore, fixed-bed biomass gasification or rotary kiln is mainly used in small-scale plants. In large-scale plants, fluidized bed biomass gasification and spouted bed biomass gasification are used.
On the other hand, when synthesizing liquid fuel from a product gas with a catalyst or when the product gas is used as a chemical raw material, it is necessary to control the product gas composition according to the catalyst performance. Type biomass gasification is used.

  Furthermore, waste biomass such as sewage sludge is free or inexpensive and can be supplied stably, but sewage sludge has a high water content and becomes powdery when dried. It cannot be used as a raw material, and can be used as a raw material for fluidized bed type biomass gasification or spouted bed type biomass gasification.

When solid organic matter such as biomass or coal is gasified using a gasifying agent, in addition to the product gas mainly composed of H ₂ , CO, CO ₂ and CH ₄ , hydrocarbon (tar) which is liquid at normal temperature Solid hydrocarbons and ash (solid residue) are also by-produced. When tar and solid residue are by-produced, the amount of generated gas decreases and the overall efficiency decreases.

In the fixed bed type gasification, rotary kiln and fluidized bed type gasification, the ratio of by-product tar to product gas is usually several g to several tens g / m ³ , but the catalyst is used to react tar with water vapor. Thus, the amount of generated gas is increased by steam reforming to a gas containing H ₂ , CO, CO ₂ , and CH ₄ as main components.

  For example, in Patent Document 1, tungsten salt and cobalt are used for the purpose of a gasification catalyst capable of efficiently steam reforming the tar content even when the temperature in the fluidized bed gasification furnace is gasified at a low temperature of 1000 ° C. or less. A gas in which a composite of one or more of salts and molybdenum salts, one or more selected from nickel sulfate, nickel acetate, and nickel carbonate, and a magnesium raw material and a calcium raw material is supported on the support surface A catalytic catalyst has been proposed, and the tungsten, cobalt, and molybdenum components take in sulfur that is easily adsorbed by nickel, and when the catalyst is put into a gasification furnace, it acts to separate into the gas, so the catalytic activity of nickel Is maintained high, and the sulfur poisoning of the catalyst is surely and effectively suppressed. The catalyst temperature when the catalyst layer is installed in the fluidized bed gasification furnace is 1000 ° C. or less, and the catalyst temperature when the tar decomposition facility is installed at the latter stage of the fluidized bed gasification furnace is 500 to 900 ° C.

Further, in Patent Document 2, a Ru / Al ₂ O ₃ catalyst, a nickel-based catalyst, an iron oxide-based catalyst, etc., in which ruthenium is supported on an alumina carrier on a support provided in a fixed bed type gasifier. It has been proposed that by using a steam reforming catalyst, a tar formed as a by-product when a solid fuel is pyrolyzed and gasified by using a steam reforming catalyst by arranging a catalyst layer made of a steam reforming catalyst.

On the other hand, in spouted bed gasification, the amount of tar produced is about 1/100, which is a small amount compared to the amount of tar produced by the fixed bed gasification, rotary kiln and fluidized bed gasification. Steam reforming is not usually performed.
When the generated gas is used for liquid fuel synthesis or chemical raw materials using a catalyst, fluidized bed type biomass gasification or spouted bed type biomass gasification is used as described above. In fluidized bed type biomass gasification, tar reforming is performed. In spouted bed type biomass gasification, it will be used alone without tar reforming.

BTL (Biomass-to-Liquid), which uses a catalyst to synthesize liquid fuel from a product gas containing H ₂ , CO, CO ₂ , and CH ₄ as main components, obtained by gasifying solid fuel such as biomass and coal The CTL (Coal-to-Liquid) process is a process using H ₂ and CO or CO ₂ as raw materials and is called C1 chemistry.
In C1 chemistry, H ₂ and CO or CO ₂ are contained as much as possible, and the molar ratio of H ₂ to CO or CO ₂ ([H ₂ ] / [CO], [H ₂ ] / ([CO] + [ It is desirable to obtain a gas with a high hydrogen ratio of CO ₂ ]) of 1 to 3.5.

The H ₂ , CO, and CO ₂ concentrations in the product gas can be controlled by changing the gasification conditions, but the methane (CH ₄ ) concentration is almost constant regardless of the gasification conditions, and the product gas from biomass It is always about 10%. However, methane does not become a synthesis raw material for BTL or CTL processes, but is included as it is in the off-gas after catalyst synthesis. Depending on the system, a part of CH ₄ may be used as a heat source, but the total process efficiency usually decreases.
Therefore, methane contained in the product gas is reacted with water vapor, which is a part of the unreacted gasifying agent, at a high temperature of 650 ° C. or higher using a methane reforming catalyst and reformed to H ₂ and CO (CH ₄ + H ₂ O → 3H ₂ + CO) If the catalyst synthesis raw material is increased, the total process efficiency can be improved by about 10% or more.

H ₂ has a larger exergy per unit energy than CH ₄ . In turbine power generation used in coal gasification combined power generation (IGCC or IGFC), power generation efficiency is improved by steam reforming CH ₄ into H ₂ and CO.
Further, H ₂ is a fuel for the fuel cell. Since IGFC uses fuel cells in cascade, efficiency is significantly improved when steam reforming CH ₄ to H ₂ and CO.

It is well known that Ni has a methane reforming effect, and Ni-based methane reforming catalysts containing Ni as a main component have already been commercialized.
However, since solid fuels such as biomass and coal contain sulfur (S), the produced gas contains sulfur compounds (H ₂ S, COS, etc. derived from raw materials. Usually, the H ₂ S concentration in the produced gas from biomass is 100 to 1000 ppm, H ₂ S concentration of 1% in the product gas from sewage sludge, H ₂ S concentration is about 0.5% of the product gas from coal) or halogen (Cl, etc.) and nitrogen compounds (NH ₃ ) and phosphorus compounds, and these components S, P, Cl and the like are likely to react with Ni, and Ni reacting with these loses the methane reforming effect (the methane reforming catalyst is deactivated). In particular, a sulfur compound such as H ₂ S and a halogen compound such as Cl have a strong poisoning action even in a very small amount, and need to be purified at a level of 1 ppm or less.
Therefore, conventionally, before the methane reforming by the catalyst, the product gas is purified using a desulfurizing agent or the like, and then the methane reforming by the methane reforming catalyst is performed.

JP 2007-283209 A JP 2009-197073 A

Conventional desulfurization methods include wet desulfurization using an amine solution or the like after the product gas is cooled to room temperature, and dry desulfurization using activated carbon or a Zn-based desulfurizing agent.
The gasification temperature of biomass is 900 to 1000 ° C, and the gasification temperature of coal is 1200 to 1500 ° C. The product gas immediately after coming out of the gasification furnace is about 800 ° C. or higher and contains water vapor as an unreacted gasifying agent. So far, no desulfurization agent that functions at high temperature and high steam has been reported. For example, under conditions that do not include steam, activated carbon or the like is used up to about 400 to 500 ° C. (the activated carbon burns at higher temperatures), Under conditions containing water vapor, Zn-based desulfurization agents have been put into practical use, but can only be used up to about 350 ° C. Therefore, the product gas containing 30 to 50% of water vapor at a high temperature of 800 to 1,200 ° C. is once cooled to room temperature to 100 ° C., and after removing the water vapor, desulfurized by wet or dry method to 650 ° C. to 750 ° C. A process of reheating and adding steam to perform methane reforming is usually performed.

  This process requires a cooling & reheating process (high temperature → low temperature → high temperature) and steam addition, which makes the equipment and operation complicated and expensive, has a large heat loss, and reduces efficiency. If possible, it is desirable to perform methane reforming directly without desulfurization → methane reforming or desulfurization process while maintaining the high temperature and high steam state immediately after gasification as much as possible.

Since the H ₂ S concentration can be reduced to about 1 ppm or less by the conventional desulfurization method, the Ni-based methane reforming catalyst reacts with sulfur (S), etc., becomes NiS, and the time until the Ni methane reforming catalyst is deactivated ( Life) can be extended more than 100 times, but the life is finite. Ni metal is expensive, and Ni-based methane reforming catalysts are also expensive. If possible, it is desirable to be able to reform methane semipermanently.

If a Ni-based methane reforming catalyst is used semi-permanently without a desulfurization process, and CH ₄ contained in the product gas can be reformed to H ₂ and CO, liquid fuel synthesis by the catalyst and chemical raw materials and coal gasification combined power generation (IGCC and IGFC) efficiency can be improved and costs can be greatly reduced.
However, Patent Document 1 and Patent Document 2 aim at reforming to gas containing H ₂ , CO, CO ₂ , and CH ₄ as main components by reacting tar generated as a by-product during gasification with water vapor using a catalyst. Is. It is clear that the example in Patent Document 1 also uses a gas not containing methane and is not intended for methane reforming.

  The present invention has been made in view of the current situation, and uses a Ni-based methane reforming catalyst or Ni metal to maintain a high temperature immediately after gasification without removing poisoning components derived from raw material components. Providing a method that can perform methane reforming stably for a long time using steam that is part of an unreacted gasifying agent at 900 ° C. or higher, and can be easily applied to any gasification furnace It is intended to do.

In order to solve these problems, in the present invention, by devising a method of using a Ni-based methane reforming catalyst and Ni metal, steam that is part of an unreacted gasifying agent is used, and CH ₄ The present invention provides the following invention, which makes it possible to stably perform methane reforming of gaseous hydrocarbons at a normal temperature for a long time.
[1] A method of reforming methane in a gas produced by gasifying solid organic matter such as biomass or coal with a gasifying agent by reacting with steam in the presence of a methane reforming catalyst,
A gas permeable sheet-like or plate-like Ni-based methane reforming catalyst is placed in the methane reforming facility in the gasification furnace or in the latter stage of the gasification furnace, and is heated to 900 ° C. or more. Quality method.
[2] The methane reforming method according to [1], wherein the methane reforming catalyst is a net-like Ni metal in which one sheet or two or more sheets are stacked.
[3] The methane reforming method according to [1] or [2], wherein the net-like Ni metal is processed into a roll shape.
[4] A methane reforming catalyst that is disposed in a gasification furnace that gasifies solid organic matter such as biomass and coal with a gasifying agent and reforms methane in the product gas by reacting with water vapor, and gas permeation A methane reforming catalyst characterized by having a sheet-like or plate-like shape.
[5] A methane reforming catalyst that is disposed in a methane reforming facility at the latter stage of a gasification furnace that gasifies solid organic matter such as biomass or coal with a gasifying agent, and reforms by reacting methane in the generated gas with steam. A methane reforming catalyst having a gas permeable sheet shape or plate shape.
[6] The methane reforming catalyst according to [4] or [5], which is made of a reticulated Ni metal.
[7] The methane reforming catalyst according to any one of [4] to [6], which is processed into a roll shape.
[8] A gasification furnace for gasifying solid organic matter such as biomass and coal with a gasifying agent, wherein the Ni-based methane reforming catalyst according to any one of claims 4 to 7 is installed in the gasification furnace Gasification furnace characterized by being made.
[9] The gasification furnace according to [8], which is a spouted bed type gasification furnace.

According to the present invention, the Ni-based methane reforming catalyst or Ni metal is installed as a gas-permeable sheet-like or plate-like member in the gasification furnace or in the latter stage of the gasification furnace, so that the temperature is 900 ° C. or higher. Thus, hydrocarbons such as methane can be steam reformed stably for a long time, and even if H ₂ S is contained in the gas produced in the gasifier, NiS and Ni are in an equilibrium state at 900 ° C. or higher. It has the effect of steam reforming gaseous hydrocarbons such as methane at room temperature stably for a long time. In addition, Ni metal can be used as the methane reforming catalyst. In particular, by using a Ni wire mesh, Ni and gas are in good contact with each other, and the steam reforming effect is improved. When a planar Ni wire mesh is stacked, the number of times the gas contacts with Ni is the same as the number of Ni wire meshes. However, when a rolled Ni wire mesh is placed vertically with respect to the gas flow, the gas contacts with Ni. The number of times is the same as the number of Ni wires used in the Ni wire mesh, which is considered to increase significantly. Furthermore, by processing into a roll shape, the solid residue produced as a by-product during gasification flows smoothly without clogging the Ni wire mesh, and can be stably gasified for a long time.

The gasification temperature of biomass is usually 900 to 1000 ° C, and the gas temperature immediately after leaving the gasification furnace is about 800 ° C or more. In order to maintain the temperature of the methane reforming catalyst at 900 ° C. or more and perform methane reforming, it is desirable to install the Ni-based methane reforming catalyst in the gasification furnace, but the Ni-based methane reforming having a heating device By installing the equipment at the latter stage of the gasification furnace, the temperature of the Ni-based methane reforming catalyst can be maintained at 900 ° C. or higher, and even when H ₂ S is contained, methane can be steam reformed stably for a long time.

Photo of the state before inserting into a gasification furnace with 8 sheets of planar Ni wire mesh Photograph showing Ni wire mesh processed into a roll Photo of the state before inserting into a gasification furnace, bundled multiple Ni wire meshes processed into a roll

  The present invention is a method for reforming methane in a gas generated by gasifying a solid organic substance such as biomass or coal with a gasifying agent by reacting with steam in the presence of a methane reforming catalyst, A gas-permeable sheet-like or plate-like Ni-based methane reforming catalyst is disposed in the gasification furnace or in the methane reforming facility at the latter stage of the gasification furnace, and is heated to 900 ° C. or more. is there.

In the present invention, the Ni-based methane reforming catalyst is installed as a gas-permeable sheet-like or plate-like member in the gasification furnace or in the methane reforming equipment at the latter stage of the gasification furnace, so that the temperature is 900 ° C or higher. Therefore, methane can be steam reformed stably for a long time, and even if H ₂ S is contained in the gas generated in the gasifier, NiS and Ni are in an equilibrium state at 900 ° C. or higher. The effect of steam reforming is maintained without the quality catalyst being deactivated.

In the present invention, since NiS and Ni are in equilibrium at 900 ° C. or higher, the Ni-based methane reforming catalyst is not essentially deactivated regardless of the H ₂ S concentration, and is expensive. Even if a Ni-based catalyst is used, the running cost can be reduced. Also, no additional work such as removal or regeneration is required, and operation is simplified.

In the present invention, the gas-permeable sheet-shaped or plate-shaped member is not particularly limited, but according to the present invention, Ni metal can be used as the Ni-based methane reforming catalyst. From this point, it is preferable to use a mesh.
In particular, by using a reticulated Ni wire mesh, Ni and gas are in good contact, and the methane reforming effect is improved.

  In addition, when the planar Ni wire mesh is stacked, the number of times the gas contacts with Ni is the same as the number of Ni wire meshes. Further, when a roll-shaped Ni wire mesh is placed vertically with respect to the gas flow, the gas becomes Ni and The number of times of contact is the same as the number of Ni wires used in the Ni wire mesh, which is considered to increase significantly. Furthermore, by processing into a roll shape, the solid residue produced as a by-product during gasification flows smoothly without clogging the Ni wire mesh, and can be stably gasified for a long time.

In the present invention, solid organic substances such as biomass, garbage, sewage sludge, and coal are supplied to the gasification furnace, a gasifying agent is introduced from the lower part of the gasification furnace, and the solids supplied into the gasification furnace Thermally decompose organic matter. As the gasifying agent, water vapor, oxygen, air, or the like is used.
The gasification gas generated in the gasification furnace is taken out from the upper part of the gasification furnace. The extracted gasified gas is a combustible gas, and is used for power generation by a fuel cell or a gas engine, a raw material for liquid fuel, a raw material for chemical products, or the like.

The gasification furnace used in the present invention may be any of a fixed bed type gasification furnace, a rotary kiln, a fluidized bed type gasification furnace, or a spouted bed type gas furnace, but the gasifying agent is introduced into the furnace from the bottom of the gasification furnace. It is preferable to use a spouted bed type gasification furnace having a large space for floating and swirling the solid organic matter by flowing upward, and the gas-permeable sheet-like or plate-like Ni-based methane modified according to the present invention is used. A quality catalyst can be placed in the gasifier.
In the case of other gasification furnaces, since there is no large space in the furnace, the gas-permeable sheet-like or plate-like Ni-based methane reformer of the present invention is installed in the methane reforming equipment at the latter stage of the gasification furnace. A quality catalyst is arranged. However, also in other gasification furnaces, by providing a space for installing the methane reforming catalyst by a partition wall or the like, the gas-permeable sheet-like or plate-like Ni-based methane reforming catalyst of the present invention, It can be placed in a gasifier.

  Hereinafter, although this invention is demonstrated based on an experiment example, this invention is not limited to this experiment example.

1. Effect of H ₂ S on commercially available methane reforming catalyst A commercially available methane reforming catalyst (FCR-4-02 manufactured by Clariant Catalyst Co., Ltd.) was installed in a spouted bed gasifier and CH ₄ + H ₂ + H ₂ O + H Table 1 shows the gas composition (steady state value after about 4 hours) when a ₂ S mixed gas (H ₂ S concentration: 170 ppm) (dry, N ₂ free) is flowed.

A steam reforming reaction of methane (the following formula (1)) and a steam shift reaction (the following formula (2)) occurred.
CH ₄ + H ₂ O → CO + 3H ₂ (1)
CO + H ₂ O → CO ₂ + H ₂ (2)
Since the CO concentration was always higher than the CO ₂ concentration, the steam reforming reaction of methane was the main. However, when H ₂ S is not included, the CH ₄ concentration is 0.1% or less, so it is considered that the methane reforming effect is lowered by H ₂ S.

If a mixed gas containing H ₂ S (concentration 170 ppm) is flowed through the catalyst at a normal use temperature of 650 to 700 ° C., the steam reforming effect is lost (deactivated) in about 1 hour. However, the methane reforming effect was exhibited even after a total of about 12 hours or more.
The concentration of H ₂ S contained in the gas after methane steam reforming was about 120 ppm. Although the H ₂ S concentration in the supplied gas is 170 ppm, the total gas amount is increased by steam reforming of CH ₄ (see the above formula (1)), so the concentration is relatively lowered. Considering the increase in gas amount, almost the entire amount of H ₂ S was contained in the treated gas. By installing the catalyst in a gasification furnace and heating it to 900 ° C or higher, the reaction between Ni and S reaches equilibrium (the following formula (3)), and the methane reforming effect can be maintained stably for a long time. It is thought.

2. Effect of methane reforming of planar Ni wire mesh As shown in Fig. 1, 8 planar Ni wire meshes are installed in a stacking furnace, and a simulated gas not containing H ₂ S (CO + CO ₂ + CH ₄ + H ₂ + H ₂ O mixed gas) ) (dry, N ₂ free), the methane reforming effect was slightly shown at 900 ° C. (Table 2).
Since it was necessary to reduce the gas amount and the gas flow rate, it was found that the gas and the Ni wire mesh must be in effective contact for steam reforming of methane with Ni metal.

3. Methane reforming effect of rolled Ni wire mesh In order to improve the contact between gas and Ni, the Ni wire mesh is processed into a roll shape as shown in FIG. 2, and the 42 rolled Ni wire meshes as shown in FIG. Bundled.
The bundled rolled Ni wire mesh is installed so as to be vertical to the gas flow, and a simulated gas not containing H ₂ S (CO + CO ₂ + CH ₄ + H ₂ + H ₂ O mixed gas) (dry, N ₂ free) flows. Table 3 shows the gas composition in this case.
The steam reforming effect of methane was remarkable at 900 ° C. The gas flow rate is 6 cm / s.

4). Effect of H ₂ S on Rolled Ni Wire Mesh Gas composition when CH ₄ + H ₂ + H ₂ O + H ₂ S mixed gas (H ₂ S concentration 170 ppm) is passed through rolled Ni wire mesh (after about 3-4 hours) Table 4 shows steady state values).
A steam reforming reaction of methane (the following formula (1)) and a steam shift reaction (the following formula (2)) occurred.
CH ₄ + H ₂ O → CO + 3H ₂ (1)
CO + H ₂ O → CO ₂ + H ₂ (2)
Since the CO concentration was always higher than the CO ₂ concentration, the steam reforming reaction of methane was the main.
As the temperature increased, the steam reforming reaction of methane was promoted more. This is considered to be because NiS is further decomposed when the temperature rises.

5. When Biomass Production Gas is Flowed through Rolled Ni Wire Mesh Table 5 shows the composition of the produced gas when gas produced by gasifying the cedar wood part at 900 ° C. is passed through the rolled Ni wire mesh.
Methane was steam reformed. By processing into a roll, clogging with solid residue did not occur, and gasification could be stably performed for a long time.

Claims (4)

A method of reforming methane in a gas produced by gasifying solid organic matter such as biomass or coal with a gasifying agent by reacting with steam in the presence of a methane reforming catalyst,
A Ni-based methane reforming catalyst made of reticulated nickel metal processed into a roll is disposed in the methane reforming facility in the gasification furnace or in the latter stage of the gasification furnace, and heated to 900 ° C. or more. Methane reforming method. The solid organic matter such as biomass or coal comprising methane in the product gas and disposed in the gasification furnace to gasify reacted with steam in Ni-based methane reforming catalyst reforming gasification agent, in the form of a roll A Ni-based methane reforming catalyst comprising a processed reticulated nickel metal . A Ni-based methane reforming catalyst that is placed in a methane reforming facility at the latter stage of a gasification furnace that gasifies solid organic matter such as biomass and coal with a gasifying agent and reforms by reacting methane in the product gas with steam. A Ni-based methane reforming catalyst comprising a reticulated nickel metal processed into a roll . The solid organic materials such as biomass or coal a entrained flow gasification furnace for gasifying the gasifying agent, the Ni-based methane reforming catalyst according to claim 2 in the gasification furnace is installed A gasifier characterized by

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