JP2021138931A - Method for gasifying biomass - Google Patents

Abstract

To provide a method for gasifying biomass that can efficiently gasify the biomass at a relatively low temperature while suppressing generation of tar.SOLUTION: The method for gasifying the biomass comprises: a catalyst-carrying step of impregnating the biomass with an aqueous solution of a catalyst component containing at least one or both of potassium and calcium to obtain a catalyst-carried biomass carrying the catalyst component; a semi-carbonizing step of heating catalyst-carried biomass from 300°C or higher to 350°C or lower in an inert atmosphere that does not substantially contain oxygen to obtain semi-carbonized catalyst-carried biomass; and a gasifying step of contacting the semi-carbonized catalyst-carried biomass with a gasifying agent containing a water vapor under temperature conditions of 600°C or higher to 800°C or lower, wherein a product gas obtained by the gasifying step contains hydrogen, carbon monoxide, carbon dioxide and methane.SELECTED DRAWING: None

Description

The present invention relates to a method for gasifying biomass. More specifically, the present invention relates to a method of efficiently gasifying biomass while suppressing the formation of tar when gasifying biomass using water vapor as a gasifying agent to obtain a gas having a high calorific value at a low temperature.

In recent years, it has been pointed out that carbon dioxide associated with the combustion of fossil fuels is a cause of global warming, and carbon-neutral fuels, which do not lead to a net increase in carbon dioxide in the atmosphere even when used for combustion, are attracting attention. Since biomass absorbs carbon dioxide in the atmosphere during its growth process, it can be regarded as a carbon-neutral fuel that does not lead to a net increase in carbon dioxide in the atmosphere even if it is used for combustion. Among the biomass, especially agricultural residue-based biomass, for example, palm palm empty fruit bunch generated in the process of obtaining palm oil, bagasse which is the residue after sugarcane juice squeezing, etc. are particularly effective because they do not compete with food applications. It is expected to be used.

On the other hand, when using biomass, it is generally solid and difficult to handle compared to liquid or gaseous fossil fuels, it contains a lot of water and has a low energy density per mass, and it has a low bulk density, so it is volumetric. There are problems such as low energy density per hit, susceptibility to decay and alteration, and unsuitability for long-distance transportation and long-term storage.

The technology of gasifying biomass and converting it into flammable gas such as hydrogen and methane can solve the above-mentioned problems in the use of biomass, and is of great significance.

Biomass is similar to coal in terms of carbonaceous solids, and its gasification is basically the same technology as coal gasification, that is, oxygen (air) and water vapor are used as gasifying agents at high temperatures. It is considered that the method of gasification can be applied.

Since the gasification reaction of a carbonaceous solid is generally an endothermic reaction, partial combustion gasification that reacts while adding oxygen as an oxidizing agent and covering the endothermic heat of gasification by the heat generated by the combustion reaction is performed at a relatively high temperature (for example, 1000 ° C.). If it is carried out in the above), gasification will proceed rapidly, which is advantageous.

On the other hand, in order to use oxygen as a gasifying agent, there is a problem that an expensive air separation facility is required. On the other hand, when air is used as the gasifying agent, there is a problem that only a gas having an extremely low calorific value can be obtained because the produced gas contains a large amount of nitrogen.

In gasification using water vapor as a gasifying agent, it is possible to obtain a gasified gas having a high calorific value without using an expensive air separation facility. On the other hand, when water vapor is used as a gasifying agent, the problem is that the reaction rate is slower than that of gasification by oxygen.

Patent Document 1 describes a method of producing a syngas from biomass by low-temperature thermal decomposition and high-temperature gasification, in which superheated steam is used as an oxidizing agent and an energy carrier to thermally decompose and gasify the biomass. It is carried out at different temperatures to finally produce clean syngas. 1) The biomass is crushed and sent to a thermal decomposition furnace while low temperature superheated steam is sprayed onto the thermal decomposition furnace. A step of controlling the thermal decomposition furnace to an operating temperature of 500 to 800 ° C. and bringing the biomass into contact with the low-temperature superheated steam for a thermal decomposition reaction to produce ash containing crude syngas and coke, and 2). The step of cooling the ash and separating the coke from the ash, and 3) transporting the crude syngas and the coke to a gasification furnace, spraying high-temperature superheated steam into the gasification furnace, and gasifying the ash. In order to control the operating temperature of the furnace to 1200 to 1600 ° C. and bring the biomass into contact with the high-temperature superheated steam to generate a primary syngas in order to carry out a gasification reaction, and 4) to obtain a clean syngas. , A method including a step of cooling, dust removing, degasifying, and drying the primary synthetic gas is disclosed.

In this method, the biomass is first decomposed in a pyrolysis furnace at 500 to 800 ° C. to obtain ash containing crude syngas and coke, and the coke that was not gasified at this stage is further gasified in a gasification furnace at 1200 to 1600 ° C. Since it is configured to be gasified with, it is considered that a sufficient reaction rate can be obtained even if water vapor is used as a gasifying agent. On the other hand, the operating temperature of the gasification furnace is an extremely high temperature of 1200 to 1600 ° C., and it is presumed that a large amount of high-temperature steam is required to maintain this temperature, and there is a problem in the energy efficiency of gasification. ..

Gasification using a catalyst is known as a method for gasifying a carbonaceous material at a relatively low temperature using water vapor as a gasifying agent. Patent Document 2 shows the effects of K, Na and Ca on steam gasification of bituminous coal at 704 ° C. (1300 ° F.). Non-Patent Document 1 shows the results of steam gasification of various coals using a calcium hydroxide catalyst at 600 to 700 ° C. Patent Document 3 shows the effect of a catalyst when gasifying brown coal using water vapor as a gasifying agent at 650 ° C to 700 ° C, and when K or Ca + Na is added as a catalyst, gasification is remarkably promoted. It has been shown to be done.

When water vapor is used as a gasifying agent and gasified at a relatively low temperature of, for example, about 700 ° C., the heat resistance is less restricted because the temperature is relatively low as compared with the case of gasifying at a high temperature of 1000 ° C. or higher. Therefore, there are merits that the equipment cost is low and the efficiency is high because the heat dissipation loss is small. In addition, when gasification is performed at a high temperature of 1000 ° C or higher, a gas containing carbon monoxide as the main component can be obtained, whereas at a low temperature of about 700 ° C, hydrogen is the main component and methane is also contained. Therefore, there is a merit that the efficiency of gasification is increased.

This is due to the following reasons. The carbon gasification reaction (reaction formula 1) is a relatively large endothermic reaction. Since carbon monoxide is highly toxic and cannot normally be used as a fuel in its original form, it is desired from the viewpoint of safety to convert it into hydrogen by a CO shift reaction (reaction formula 2). When used as a raw material for city gas, it is converted to safer methane by a methanation reaction (reaction formula 3).
C + H ₂ O (g) → CO + H ₂ ΔH = + 131.3 kJ / mol (endothermic) (1)
CO + H ₂ O (g) → CO ₂ + H ₂ ΔH = -41.1 kJ / mol (heat generation) (2)
CO + 3H ₂ → CH ₄ + H ₂ O (g) ΔH = -206.2 kJ / mol (heat generation) (3)

Since both the CO shift reaction and the methanation reaction are exothermic reactions, if gasification is performed at a high temperature to obtain a gas containing carbon monoxide as the main component, the CO shift reaction or methanation reaction that proceeds at a lower temperature will occur. The generated heat cannot be used as a heat source for the gasification reaction, which is an endothermic reaction.

When gasifying at a low temperature of about 700 ° C. to obtain a gas containing a large amount of hydrogen and methane, part of the endothermic heat associated with the gasification of carbon is covered by the heat generated by the CO shift reaction and the methaneization reaction. In essence, highly efficient gasification is possible.

Gasification using water vapor as a gasifying agent at a low temperature of about 700 ° C has the above-mentioned merits, but on the other hand, a large amount of tar is generated, which makes it difficult to utilize the generated gas. , It is known that problems such as hindrance to the operation of the gasification plant occur (for example, Non-Patent Document 2).

Pat. In a biomass carbonization / gasification system having a two-stage gasification furnace having a reducer which is a gas reforming unit for reforming decomposition gas, the carbonizer supplies the combustor of the gasification furnace. A biomass carbonization / gasification system is disclosed, which comprises a tar adsorbing means for bringing carbonized matter into contact with a product gas discharged from the reducer.

In this system, the gas obtained by gasification is brought into contact with carbides produced by thermally decomposing biomass fuel, and tar is adsorbed on the carbides to reduce the tar content in the produced gas. However, this document does not describe the details of the operating conditions of the carbonizer and the high temperature gasifier. In addition, since the gasifying agent is a gas containing oxygen, it is presumed to be a technology related to partial combustion gasification.

Patent Document 5 describes a catalyst in which a gasification catalyst component is carried in a porous fluid medium, which promotes the decomposition of tar and the steam reforming reaction that occur in the thermal decomposition process of biomass, and includes hydrogen and carbon monoxide. A catalyst capable of increasing the amount of low molecular weight gas produced is disclosed. It is also disclosed that the gasification catalyst component is preferably an alkali metal such as sodium. This catalyst is expected to be added as a fluidized medium when gasifying biomass in a fluidized bed. Although this method promotes the decomposition of tar that can come into contact with the catalyst in a gaseous state, it is difficult to expect the promotion of gasification of solid biomass. Moreover, since the catalyst is consumed by wear due to flow, it cannot be said to be economically advantageous.

Many proposals have been made for a technique for steam reforming tar by installing a catalyst at the gasification furnace outlet (for example, Patent Document 6), but various gases other than tar are used for gasifying biomass. Since a substance such as a sulfur compound is contained, it is difficult to use the catalyst stably for a long period of time, and the cost for replacing the deteriorated catalyst may become large.

As described above, a biomass gasification process for efficiently gasifying biomass at a relatively low temperature of 600 ° C. or higher and 800 ° C. or lower while suppressing the generation of tar using water vapor as a gasifying agent has not yet been established. The reality is that there is no such thing.

Special Table 2013-531122 Japanese Unexamined Patent Publication No. 54-122304 JP-A-2019-157122 Japanese Unexamined Patent Publication No. 2013-241487 Japanese Unexamined Patent Publication No. 2007-23084 Special Table 2012-527345

Yasuo Ohtsuka and Kenji Asami, Energy and Fuels, Vol. 9, 1995, p. 1038-1042 Hugo de Lasa et al., Chemical Reviews, Vol. 111, 2011, p. 5404-5433.

In view of the above-mentioned prior art, an object of the present invention is to efficiently gasify biomass at a relatively low temperature of 600 ° C. or higher and 800 ° C. or lower while suppressing tar generation in gasification of biomass using water vapor as a gasifying agent. The purpose is to provide a method for gasifying biomass to be gasified.

The characteristic configuration of the method for gasifying biomass according to the present invention is a catalyst-supporting step of impregnating biomass with an aqueous solution of a catalyst component containing at least one or both of potassium and calcium to obtain a catalyst-supporting biomass bearing the catalyst component. A semi-carbonization step of heating the catalyst-supporting biomass to 300 ° C. or higher and 350 ° C. or lower to obtain the semi-carbonized biomass in an inert atmosphere containing substantially no oxygen, and the semi-carbonization treatment. A gasification step of contacting the catalyst-supported biomass with a gasifying agent containing water vapor under a temperature condition of 600 ° C. or higher and 800 ° C. or lower is included, and the produced gas obtained by the gasification step is hydrogen or monoxide. It contains carbon, carbonization, and methane.

According to the above configuration, the biomass is impregnated and supported with a catalytic component containing at least one or both of potassium and calcium. Due to the action of the catalyst component, gasification proceeds at a sufficient rate using water vapor as a gasifying agent even under temperature conditions of 600 ° C. or higher and 800 ° C. or lower.

Further, according to the above configuration, prior to contacting the biomass with the gas containing water vapor to gasify it, the catalyst-supported biomass carrying the catalyst component is heated to 300 ° C. or higher and 350 ° C. or lower to perform semi-carbonization treatment. , Semi-carbonized catalyst-supported biomass. By performing this semi-carbonization treatment, at least a part of the volatile matter in the biomass is volatilized, and the remaining volatile matter is also changed to a component which is difficult to generate tar at the time of gasification. At this time, tar is generated, but since the temperature of the generated region is lower than that of the gasifier, the treatment is easy and the operation of the gasifier is not hindered.

Further, according to the above configuration, the semi-carbonized catalyst-supported biomass is brought into contact with a gasifying agent containing water vapor under a temperature condition of 600 ° C. or higher and 800 ° C. or lower. As a result, the semi-carbonized catalyst-supported biomass is gasified to obtain a produced gas containing hydrogen, carbon monoxide, carbon dioxide, and methane.

Therefore, according to the above configuration, in the gasification of biomass using water vapor as a gasifying agent, the biomass is efficiently gasified at a relatively low temperature of 600 ° C. or higher and 800 ° C. or lower while suppressing the generation of tar. Biomass can be gasified economically with high efficiency.

Hereinafter, preferred embodiments of the present invention will be described. However, the scope of the present invention is not limited by the preferred embodiments described below.

A further characteristic configuration of the method for gasifying biomass according to the present invention is that potassium having a mass ratio of 1% or more and 5% or less with respect to the biomass and calcium having a mass ratio of 1% or more and 5% or less with respect to the biomass in the catalyst supporting step. Or, it carries potassium and calcium having a total mass ratio of 2% or more and 10% or less with respect to the biomass.

According to this configuration, the effect of promoting gasification can be easily obtained, and the cost effectiveness is high.

A further characteristic configuration of the biomass gasification method according to the present invention is that the biomass used in the catalyst-supporting step has a constant humidity moisture content of 20% or less according to an industrial analysis method.

According to this configuration, the energy consumed for drying the biomass in the semi-carbonization step is reduced, so that the efficiency of gasification tends to increase.

A further characteristic configuration of the biomass gasification method according to the present invention is that the biomass used in the catalyst-supporting step has an ash content of 10% by mass or less according to an industrial analysis method.

According to this configuration, the accumulation of ash in the gasifier can be suppressed, so that the energy efficiency of the gasifier is unlikely to decrease.

A further characteristic configuration of the biomass gasification method according to the present invention is that the biomass used in the catalyst-supporting step contains 10% or more and 30% or less of fixed carbon according to an industrial analysis method.

According to this configuration, it is easy to suppress the generation of tar and the gasification rate is likely to be high.

A further characteristic configuration of the method for gasifying biomass according to the present invention is that it further includes a drying step of drying the catalyst-supported biomass until the water content becomes 15% or less, prior to the semi-carbonization step.

According to this configuration, the energy consumption for drying the biomass can be suppressed in the semi-carbonization step.

A further characteristic configuration of the biomass gasification method according to the present invention is that the gasification step is carried out at a pressure of 0.5 MPa or more.

According to this configuration, the equilibrium of the methanation reaction is advantageous for the generating system, so that methane can be easily obtained.

A further characteristic configuration of the biomass gasification method according to the present invention is that in the gasification step, the S / C ratio, which is the molar ratio of the water vapor S to the substance amount C of carbon atoms in the catalyst-supported biomass, is 1 or more. The point is that it is 10 or less.

According to this configuration, the gasification reaction can easily proceed at a sufficient speed, and the amount of energy required to generate water vapor can be easily suppressed. Moreover, since the steam reforming reaction of methane can be suppressed, methane can be easily obtained.

Further features and advantages of the present invention will be further clarified by the following illustration of exemplary and non-limiting embodiments.

Hereinafter, embodiments of the present invention will be described in detail. The method for gasifying biomass according to the present embodiment includes a catalyst-supporting step of supporting a catalyst component containing at least one or both of potassium and calcium in the biomass, and a catalyst-supporting biomass in which the catalyst-supporting biomass is heated and semi-carbonized. The semi-carbonized step of obtaining and the gasification step of gasifying the semi-carbonized catalyst-supported biomass are included.

〔biomass〕
There is no particular limitation on the target biomass of the biomass gasification method of the present embodiment, but it is preferable that the constant moisture content according to the industrial analysis method is 20% or less. When the constant humidity moisture is within the above range, the energy consumed for drying the biomass in the semi-carbonization step becomes small, so that the efficiency of gasification tends to increase.

Further, the biomass targeted by the biomass gasification method of the present embodiment preferably has an ash content of 10% by mass or less according to an industrial analysis method. When the ash content is within the above range, the accumulation of ash content in the gasification furnace can be suppressed, so that the energy efficiency of the gasification furnace is unlikely to decrease.

In addition, it is desirable that the biomass targeted by the biomass gasification method of the present embodiment contains 10% or more and 30% or less of fixed carbon according to the industrial analysis method. When the fixed carbon content is 10% or more, it is easy to suppress the generation of tar. Further, when the fixed carbon content is 30% or less, the gasification rate tends to be high.

Examples of such biomass include, but are not limited to, palm palm empty fruit bunches, bagasse, corn cobs, thinned wood, and wood chips generated during sawing.

The shape and size of the biomass are not restricted as long as they can be delivered to the catalyst-supporting equipment and the semi-carbonized equipment. Generally, a large amount of energy is required to crush biomass, but since it becomes brittle after semi-carbonization and the energy required for crushing is also small, crushing treatment before semi-carbonization treatment is usually unnecessary.

[Catalyst support step]
In the method for gasifying biomass of the present embodiment, first, a catalyst supporting step is carried out. In the catalyst loading step, the catalyst is supported on the biomass. The catalytic component contains at least one or both of potassium (K) and calcium (Ca).

Here, the supported amount of the catalyst component is preferably such that the supported amount of potassium and calcium for at least one metal is 1% or more and 5% or less in terms of the mass ratio of the metal to the biomass (dry mass). For at least one metal of potassium and calcium, when the amount of the metal supported on the biomass is 1% or more, the effect of promoting gasification is likely to be obtained. Further, for at least one metal of potassium and calcium, it is cost-effective when the metal is 5% or less of the biomass. The amount of the metal supported on the biomass is more preferably 1% or more and 4% or less, and further preferably 1% or more and 3% or less for at least one metal of potassium and calcium.

When the catalyst component contains both potassium and calcium, the above-mentioned suitable loading amount is applied to both potassium and calcium. That is, in this case, the amount of the catalyst component supported is preferably 1% or more and 5% or less in terms of the mass ratio of potassium to biomass and 1% or more and 5% or less in terms of the mass ratio of calcium. Further, it is preferable that the total amount of potassium and calcium supported is 2% or more and 10% or less in terms of mass ratio with respect to biomass.

Further, in the present embodiment, the catalyst supported on the biomass may contain iron (Fe), sodium (Na) and the like in addition to at least one of potassium and calcium. When supporting components other than potassium and calcium, the mass of each component other than potassium and calcium with respect to the biomass (dry mass) is preferably 1% or more and 5% or less, respectively, and 1% or more and 4% or less. Is more preferable, and 1.5% or more and 3% or less is particularly preferable.

The support can be carried out by an impregnation method. An aqueous solution prepared by dissolving a water-soluble salt of a catalyst component (for example, potassium nitrate, calcium nitrate, iron (III) nitrate, etc.) is prepared, and biomass is dipped in the aqueous solution and dried to support the catalyst. As long as the catalyst component can be uniformly supported, the biomass may be supported by a method of spraying or sprinkling the above-mentioned aqueous solution. The catalyst-supported biomass is preferably subjected to a semi-carbonization step following a drying step in which the catalyst is dried in air or in an inert gas until the water content is 15% or less. The drying conditions in the drying step can be, for example, 60 ° C. or higher and 150 ° C. or lower, and 1 hour or more and less than 12 hours. The water content after drying is more preferably 10% or less. The drying temperature is more preferably 100 ° C. or higher and 120 ° C. or lower, and the drying time is more preferably 1 hour or longer and less than 3 hours.

[Semi-carbonization process]
In the biomass gasification method of the present embodiment, the catalyst-supported biomass obtained in the catalyst-supporting step is then heated to 300 ° C. or higher and 350 ° C. or lower to be semi-carbonized in an inert atmosphere that does not substantially contain oxygen. A semi-carbonization step is carried out to obtain the treated catalyst-supported biomass.

Here, the “inert atmosphere substantially free of oxygen” may be, for example, a nitrogen gas atmosphere, but even in an atmosphere of a gas containing a trace amount of oxygen such as combustion exhaust gas, the biomass is a semi-carbonized step. It can be used as long as it is not burned and lost.

The semi-carbonization equipment used in the semi-carbonization step is not particularly limited, but may be a rotary furnace such as a rotary kiln. The semi-carbonization step may be carried out in a batch manner or in a continuous manner.

In the semi-carbonization process, tar is released from the biomass, so by extracting gas from the furnace at a constant flow rate, mixing it with air, burning it, and returning it to the furnace again, the generated tar is effectively used as a heat source for semi-carbonization. It can be utilized. At this time, if the oxygen concentration is low and gas phase combustion is difficult, catalyst combustion may be used, and a catalyst may be provided in the furnace if necessary.

[Gasification process]
In the biomass gasification method of the present embodiment, a gasification step is then carried out. In the gasification step, the semi-carbonized catalyst-supported biomass obtained in the semi-carbonization step is brought into contact with a gasifying agent containing water vapor under a temperature condition of 600 ° C. or higher and 800 ° C. or lower to cause hydrogen and monoxide. Obtain a produced gas containing carbon, carbon dioxide, and methane. When the gasification temperature is lower than 600 ° C., it becomes difficult to gasify at a practical rate even if a highly active catalyst is used. On the other hand, when the gasification temperature is higher than 800 ° C., the equipment cost increases and the produced gas contains a large amount of carbon monoxide, which lowers the gasification efficiency.

As a method of maintaining the internal temperature of the gasification furnace at the above temperature, a method of raising the temperature of the steam sent into the gasification furnace to a sufficiently high temperature (for example, 1000 ° C.) and a method of heating from the outside of the gasification furnace (for example). There is a method of using an external heat gasification furnace). In the method for gasifying biomass of the present invention, gasification is performed at a temperature lower than that of the conventional technique, so that it is easy to use an external heat type gasification furnace.

Gasification can be carried out, for example, by using a fluidized bed gasification furnace, in which semi-carbonized catalyst-supported biomass and steam are continuously charged and the produced gas is continuously extracted.

The pressure of the gasification reaction is not particularly limited, but the higher the pressure, the more advantageous the methane production in equilibrium. Therefore, when the purpose is to generate methane, it is preferably 0.5 MPa or more, more preferably 1 MPa or more.

In the present embodiment, the molar ratio (S / C ratio) of water vapor (water) S to the amount of substance C of carbon atoms in the semi-carbonized catalyst-supported biomass is preferably 1 or more and 10 or less. When the S / C ratio is 1 or more, the gasification reaction tends to proceed at a sufficient speed. Further, when the S / C ratio is 10 or less, it is easy to suppress the amount of energy required to generate water vapor. When the purpose is to produce methane, the S / C ratio is preferably 10 or less from the viewpoint of suppressing the steam reforming reaction of methane (reaction formula 4 and reaction formula 5). This is because in a reaction system in which a large amount of water vapor is present, the equilibrium of the steam reforming reaction of methane is advantageous for the generating system. The S / C ratio is more preferably 1 or more and 5 or less, and further preferably 1.5 or more and 4 or less.
CH ₄ + 2H ₂ O (g) → 4H ₂ + CO ₂ ΔH = + 165.0 kJ / mol (endothermic) (4)
CH ₄ + H ₂ O (g) → 3H ₂ + CO ΔH = + 206.2 kJ / mol (endothermic) (5)

[Product]
According to the method for gasifying biomass according to the present embodiment, a produced gas containing hydrogen, carbon monoxide, carbon dioxide, and methane can be obtained.

The configurations disclosed in the above embodiments can be applied in combination with the configurations disclosed in other embodiments as long as there is no contradiction, and the embodiments disclosed in the present specification are By way of example, the embodiment of the present invention is not limited to this, and can be appropriately modified without departing from the object of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

〔biomass〕
As the biomass to be used for the test, Malaysian palm palm empty fruit bunch (EFB) was used. The results of this industrial analysis of EFB are: moisture 9.4% (constant humidity standard, mass ratio), volatile content 78.1%, fixed carbon 19.8%, ash content 2.1% (all dry EFB standard, mass ratio). )Met. The main components of the ash content were K: 0.72%, Si: 0.25%, Ca: 0.06%, and Mg: 0.06% (metal equivalent). The elemental composition based on anhydrous ashlessness was C: 43.5%, H: 6.3%, N: 0.21%, and S: 0.03%.

[Test equipment and test method]
The gasification test of each sample described later was carried out using a fluidized bed reactor. The fluidized bed reactor is made of stainless steel, and the inner diameter of the fluidized bed is 23.2 mm, the height is 60 mm, and the volume is 25 mL. In total, up to a portion having a height of 210 mm is heated to a predetermined temperature. A mixed gas of water vapor and nitrogen is introduced as a gasifying agent through a stainless steel filter at the bottom of the reactor. On the other hand, a screw feeder is provided on the upper part of the reactor, and the sample is continuously introduced. In order to prevent dew condensation on the screw feeder portion, a small amount of nitrogen gas is also introduced into the screw feeder portion. The gas produced by gasification is introduced into a flow meter and a gas chromatograph through a trap of ice water (2nd stage) and dry ice (1st stage) and analyzed. Here, nitrogen is introduced for experimental reasons in order to perform accurate analysis of the produced gas, and is not necessary for the actual operation of the gasification plant.

[Sample preparation and evaluation of gasification rate]
Samples A to I were prepared as shown below, and the gasification rate was evaluated. Samples A, C, D, and FI are examples of the present invention. Further, the other samples B and E described above are comparative examples of the present invention.

<< Sample A >>
The above EFB was cut into several cm in length, further pulverized with a mixer, and classified into 53 to 1000 μm. This was dried overnight at 107 ° C. in the air, mixed with an aqueous potassium nitrate solution containing potassium corresponding to 2% by mass ratio to the dried EFB, mixed well, dried under reduced pressure at 80 ° C., and further dried at 107 ° C. Drying under reduced pressure gave potassium-supported EFB.

This potassium-supported EFB was held at 300 ° C. for 2 hours under nitrogen flow and subjected to semi-carbonization treatment to obtain Sample A. The semi-carbonized yield (meaning the ratio of the obtained sample to the charged amount of potassium-supported EFB. The same shall apply hereinafter) was 31%. The elemental composition of Sample A was C: 62.2%, H: 3.53%, N: 1.04%, S: 0.06% (constant humidity base with a water content of 7.9%). After acid decomposition of sample A, the amount supported was quantified by ICP analysis. The potassium content of sample A was 8.1% (meaning the mass ratio of potassium contained in the sample to the entire sample. The same shall apply hereinafter).

A gasification test on a fluidized bed was performed using sample A. The temperature inside the reaction tube was controlled to 700 ° C., and Sample A was continuously charged into the fluidized bed reactor at a charging rate of 20.5 mg / min (1.070 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 40.0 mg / min by mixing with 40 mL / min of nitrogen. In addition, 50 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gases are hydrogen 262 mmol, carbon monoxide (CO) 58.7 mmol, carbon dioxide (CO ₂ ) 71.1 mmol, methane 3.7 mmol, C2 (ethane and ethylene) 0.2 mmol, C3. It contained 0.1 mmol (propane and propylene). The carbon-based gasification rate was 83.6%. The S / C ratio in this test ([water vapor in the sample and water vapor supplied as a gasifying agent] / [carbon in the sample] molar ratio. The same shall apply hereinafter) was 2.99. rice field. In addition, 0.05 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 2.4%.

<< Sample B >>
The above EFB was held at 300 ° C. for 2 hours under nitrogen flow and subjected to semi-carbonization treatment to obtain Sample B. The semi-carbonized yield was 41%. The elemental composition of Sample B was C: 70.4%, H: 4.82%, N: 0.79%, S: 0.05% (constant humidity base with a water content of 2.3%). The potassium content of sample B was 2.4%.

Using sample B, a gasification test was performed on a fluidized bed in the same procedure as for sample A. The temperature inside the reaction tube was controlled to 700 ° C., and Sample B was continuously charged into the fluidized bed reactor at a charging rate of 43.5 mg / min (2.560 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 95.0 mg / min by mixing with 40 mL / min of nitrogen. In addition, 50 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gases are 326 mmol of hydrogen, 48.0 mmol of carbon monoxide (CO), 144 mmol of carbon dioxide (CO ₂ ), 17.1 mmol of methane, 4.0 mmol of C2 (ethane and ethylene), and C3 (propane). And propylene) 1.0 mmol. The carbon-based gasification rate was 57.4%. The S / C ratio in this test was 2.91. In addition, 0.15 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 2.9%.

<< Sample C >>
Sample C was obtained in the same manner as in Sample A except that the semi-carbonization temperature was set to 350 ° C. The semi-carbonized yield was 31%. The elemental composition of Sample C was C: 63.4%, H: 3.36%, N: 0.99%, S: 0.02% (constant humidity base with a water content of 10.6%). After acid decomposition of Sample C, the amount supported was quantified by ICP analysis. The potassium content of sample C was 7.9% (mass ratio of potassium contained in the sample to the whole sample; the same applies hereinafter).

Using sample C, a gasification test was performed on a fluidized bed in the same procedure as for sample A. The temperature inside the reaction tube was controlled to 700 ° C., and Sample C was continuously charged into the fluidized bed reactor at a charging rate of 28.5 mg / min (1.556 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 59.0 mg / min by mixing with 40 mL / min of nitrogen. In addition, 67 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gases are hydrogen 343 mmol, carbon monoxide (CO) 80.8 mmol, carbon dioxide (CO ₂ ) 129 mmol, methane 3.9 mmol, C2 (ethane and ethylene) 0.2 mmol, and C3 (propane). And propylene) contained 0.04 mmol (denoted as "C-1" in Table 1). The carbon-based gasification rate was 91.9%. The S / C ratio in this test was 3.03. In addition, 0.02 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.8%.

In addition, using sample C, the effect of the S / C ratio in gasification on the composition of the produced gas was examined. The input rate of sample C was 27.2 mg / min (1.461 mmol / min as the carbon supply rate), and the input rate of water as a gasifying agent was 33.0 mg / min. The S / C ratio in this test was 1.85. As shown in Table 1, the produced gases are hydrogen 249 mmol, carbon monoxide (CO) 82.1 mmol, carbon dioxide (CO ₂ ) 82.2 mmol, methane 3.9 mmol, C2 (ethane and ethylene) 0.2 mmol, C3. It contained 0.1 mmol (propane and propylene) (denoted as "C-2" in Table 1). The carbon-based gasification rate was 77.0%. In addition, 0.02 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.7%.

<< Sample D >>
Sample D was obtained in the same manner as in Sample A, except that the amount of potassium supported was 5% in terms of mass ratio to dry EFB. The semi-carbonized yield was 32%. The elemental composition of Sample D was C: 57.6%, H: 2.65%, N: 1.36%, S: 0.01% (constant humidity base with a water content of 10.8%). The potassium content of sample D was 13.0%.

Using Sample D, a gasification test was performed on a fluidized bed in the same procedure as for Sample A. The temperature inside the reaction tube was controlled to 700 ° C., and Sample D was continuously charged into the fluidized bed reactor at a charging rate of 18.9 mg / min (0.896 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 28.0 mg / min by mixing with 40 mL / min of nitrogen. In addition, 50 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gases are 180 mmol of hydrogen, 51.7 mmol of carbon monoxide (CO), 61.6 mmol of carbon dioxide (CO ₂ ), 0.7 mmol of methane, 0.02 mmol of C2 (ethane and ethylene), and C3. It contained 0.1 mmol (propane and propylene). The carbon-based gasification rate was 85.0%. The S / C ratio in this test was 2.57. In addition, 0.03 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 1.7%.

<< Sample E >>
Sample E was obtained in the same manner as Sample A except that the semi-carbonization temperature was set to 250 ° C. The semi-carbonized yield was 71%. The elemental composition of Sample E was C: 50.3%, H: 5.54%, N: 1.21%, S: 0.04% (constant humidity base with a water content of 3.1%). The potassium content of sample E was 3.8%.

Using sample E, a gasification test was performed on a fluidized bed in the same procedure as for sample A. The temperature inside the reaction tube was controlled to 700 ° C., and Sample E was continuously charged into the fluidized bed reactor at a charging rate of 49.3 mg / min (2.068 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 77.0 mg / min mixed with nitrogen at 40 mL / min. In addition, 67 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gases are hydrogen 270 mmol, carbon monoxide (CO) 67.7 _{mmol, carbon dioxide (CO 2} ) 123 mmol, methane 17.1 mmol, C2 (ethane and ethylene) 7.0 mmol, and C3 (propane). And propylene) 1.7 mmol. The carbon-based gasification rate was 73.3%. The S / C ratio in this test was 2.93. In addition, 0.29 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 7.2%.

<< Sample F >>
Sample F was obtained in the same manner as in Sample A, except that a calcium nitrate aqueous solution containing calcium corresponding to 2% by mass ratio to dry EFB was used instead of the potassium nitrate aqueous solution. The semi-carbonized yield was 36%. The elemental composition of Sample F was C: 65.4%, H: 3.60%, N: 1.45%, S: 0.02% (constant humidity base with a water content of 5.1%). The calcium content of sample F was 4.8% and the potassium content was 1.9%.

Using sample F, a gasification test was performed on a fluidized bed in the same procedure as for sample A. The temperature inside the reaction tube was controlled to 700 ° C., and the sample E was continuously charged into the fluidized bed reactor at a charging rate of 41.3 mg / min (2.373 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 90.8 mg / min by mixing with 40 mL / min of nitrogen. In addition, 50 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gas contained 528 mmol of hydrogen, 103 mmol of carbon monoxide (CO), 201 mmol of carbon dioxide (CO ₂ ), 10.5 mmol of methane, and 1.2 mmol of C2 (ethane and ethylene). The carbon-based gasification rate was 89.0%. The S / C ratio in this test was 3.01. In addition, 0.013 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.3%.

<< Sample G >>
Sample G was obtained in the same manner as in Sample A, except that a mixed aqueous solution of potassium nitrate and calcium nitrate containing 2% each of potassium and calcium in terms of mass ratio to dry EFB was used instead of the aqueous potassium nitrate solution. The semi-carbonized yield was 33%. The elemental composition of Sample G was C: 59.1%, H: 2.66%, N: 1.50%, S: 0.02% (constant humidity base with a water content of 6.3%). The potassium content of sample G was 7.4% and the calcium content was 4.8%.

Using sample G, a gasification test was performed on a fluidized bed in the same procedure as for sample A. The temperature inside the reaction tube was controlled to 700 ° C., and the sample G was continuously charged into the fluidized bed reactor at a charging rate of 48.8 mg / min (2.567 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 98.3 mg / min by mixing with 40 mL / min of nitrogen. In addition, 50 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gas contained 586 mmol of hydrogen, 142 mmol of carbon monoxide (CO), 209 mmol of carbon dioxide (CO ₂ ), 5.5 mmol of methane, and 0.2 mmol of C2 (ethane and ethylene). The carbon-based gasification rate was 92.8%. The S / C ratio in this test was 3.04. In addition, 0.003 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.1%.

Moreover, using the sample G, the influence of the gasification temperature on the gasification rate and the composition of the produced gas was examined. The internal temperature of the reaction tube is controlled to 650 ° C., the charging rate of sample G is 44.9 mg / min (carbon supply rate: 2.360 mmol / min), and the charging rate of water as a gasifying agent is 88.2 mg / min. The flow rate was set to. The S / C ratio in this test was 2.98. As shown in Table 1, the produced gas contained 460 mmol of hydrogen, 69.2 mmol of carbon monoxide (CO), 190 _{mmol of carbon dioxide (CO 2} ), 5.1 mmol of methane, and 0.2 mmol of C2 (ethane and ethylene). (In Table 1, it is described as "G-2"). The carbon-based gasification rate was 74.7%. In addition, 0.009 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.2%.

Further, the internal temperature of the reaction tube was controlled to 750 ° C., the charging rate of sample G was 46.7 mg / min (2.454 mmol / min as the carbon supply rate), and the charging rate of water as a gasifying agent was 97.3 mg. The flow rate was / minute. The S / C ratio in this test was 3.14. As shown in Table 1, the produced gas contained 557 mmol of hydrogen, 160 mmol of carbon monoxide (CO), 190 mmol of carbon dioxide (CO ₂ ), 3.6 mmol of methane, and 0.2 mmol of C2 (ethane and ethylene) (Table). In 1, it was described as "G-3"). The carbon-based gasification rate was 96.0%. In addition, 0.003 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.1%.

<< Sample H >>
Sample H was obtained in the same manner as in Sample G except that the semi-carbonization temperature was set to 350 ° C. The semi-carbonized yield was 32%. The elemental composition of the sample was C: 58.3%, H: 2.68%, N: 1.39%, S: 0.01% (constant humidity base with a water content of 6.9%). The potassium content of sample H was 7.0% and the calcium content was 4.9%.

Using sample H, a gasification test was performed on a fluidized bed in the same procedure as for sample A. The temperature inside the reaction tube was controlled to 700 ° C., and the sample H was continuously charged into the fluidized bed reactor at a charging rate of 67.4 mg / min (3.520 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 122.0 mg / min by mixing with 40 mL / min of nitrogen. In addition, 50 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gas contained 780 mmol of hydrogen, 183 mmol of carbon monoxide (CO), 285 mmol of carbon dioxide (CO ₂ ), 7.4 mmol of methane, and 0.2 mmol of C2 (ethane and ethylene). The carbon-based gasification rate was 90.2%. The S / C ratio in this test was 2.77. In addition, 0.001 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.02%.

<< Sample I >>
Sample I was obtained in the same manner as in Sample A, except that a mixed aqueous solution of potassium nitrate and iron (III) nitrate containing 2% each of potassium and iron in terms of mass ratio to dry EFB was used instead of the aqueous potassium nitrate solution. The semi-carbonized yield was 38%. The elemental composition of Sample I was C: 62.2%, H: 3.74%, N: 1.35%, S: 0.01% (constant humidity base with a water content of 3.1%). The potassium content of Sample I was 6.7% and the iron content was 3.8%.

Using Sample I, a gasification test was performed on a fluidized bed in the same procedure as for Sample A. The temperature inside the reaction tube was controlled to 700 ° C., and Sample I was continuously charged into the fluidized bed reactor at a charging rate of 34.3 mg / min (1.834 mmol / min as the carbon supply rate) for 150 minutes. As a gasifying agent, water was introduced at a flow rate of 73.0 mg / min by mixing with 40 mL / min of nitrogen. In addition, 50 mL / min of nitrogen was introduced from the screw feeder section. Water was continuously added for 60 minutes after the completion of the addition of the sample. In addition, nitrogen was circulated even after the addition of water until the replacement of the gas in the reaction tube was completed, and all the gasified gas was recovered. As shown in Table 1, the produced gases are hydrogen 393 mmol, carbon monoxide (CO) 88.8 mmol, carbon dioxide (CO ₂ ) 153 mmol, methane 5.9 mmol, C2 (ethane and ethylene) 1.2 mmol, and C3 (propane). And propylene) 0.1 mmol. The carbon-based gasification rate was 90.9%. The S / C ratio in this test was 3.13. In addition, 0.012 g of tar was recovered from the trap. When the tar composition was assumed to be C1H1 and converted to carbon, the tar yield based on carbon was 0.3%.

注：ガス化温度は、試料Ｇ−２およびＧ−３以外について７００℃、試料Ｇ−２について６５０℃、試料Ｇ−３について７５０℃とした。

Note: The gasification temperature was 700 ° C. for samples other than G-2 and G-3, 650 ° C. for sample G-2, and 750 ° C. for sample G-3.

〔result〕
According to the method of the present invention, when at least one or both of potassium and calcium are supported on the biomass as a catalyst, semi-carbonized at 300 ° C. or higher and 350 ° C. or lower, and then gasified at 700 ° C. using steam, 77. A high gasification rate of .0 to 91.9% was obtained, and the tar yield could be suppressed as low as about 0.3 to 2.4% (Samples A, C, D, and F). Further, when both potassium and calcium are supported on the biomass as a catalyst, semi-carbonized at 300 ° C. or higher and 350 ° C. or lower, and then gasified at 700 ° C. using steam, the gasification rate increases and tar is added. The yield was reduced to 0.1% or less (Samples G and H). Even if iron was supported on the biomass as a catalyst in addition to potassium, the gasification rate was improved and the tar yield was decreased as compared with the case of potassium alone (Sample I).

On the other hand, in sample E having a low semi-carbonization temperature of 250 ° C., the gasification rate was slightly low at 73.3%, and the tar yield was 7.2%, which was more than three times that of the examples.

Further, in the sample B which was semi-carbonized at 300 ° C. but did not support either potassium or calcium, the gasification rate was 57.4%, which was significantly lower than that in the case where the catalyst was supported. Above, the tar yield was 2.9%, which was higher than that of the examples.

Further, as the gasification temperature was raised to 650 ° C. (G-2), 700 ° C. (G-1), and 750 ° C. (G-3), the gasification rate was improved. On the other hand, the molar ratio of (hydrogen) / (carbon monoxide) contained in the produced gas decreased to 6.6, 4.1, and 3.5 at 650 ° C, 700 ° C, and 750 ° C. If the generated gas contains a large amount of carbon monoxide, the energy efficiency will decrease by the amount of heat generated by the CO shift reaction when the generated gas is finally converted to hydrogen or methane. From the viewpoint of efficiently gasifying biomass while suppressing the generation of methane, it can be said that the gasification temperature is preferably around 700 ° C.

From the above results, according to the method of the present invention, when at least one or both of potassium and calcium are supported on the biomass as a catalyst, semi-carbonized at 300 ° C. or higher and 350 ° C. or lower, and then gasified with water vapor, water vapor is generated. In the gasification of biomass using the above as a gasifying agent, it is clear that the biomass can be efficiently gasified at a relatively low temperature of 600 ° C. or higher and 800 ° C. or lower while suppressing the generation of tar.

Claims (8)

A catalyst-supporting step of impregnating biomass with an aqueous solution of a catalyst component containing at least one or both of potassium and calcium to obtain a catalyst-supporting biomass supporting the catalyst component.
A semi-carbonization step of heating the catalyst-supported biomass to 300 ° C. or higher and 350 ° C. or lower in an inert atmosphere containing substantially no oxygen to obtain the semi-carbonized biomass.
The semi-carbonized step of gasifying the catalyst-supported biomass with a gasifying agent containing water vapor under a temperature condition of 600 ° C. or higher and 800 ° C. or lower is included.
A method for gasifying biomass in which the produced gas obtained by the gasification step contains hydrogen, carbon monoxide, carbon dioxide, and methane. In the catalyst supporting step,
Potassium having a mass ratio of 1% or more and 5% or less to the biomass,
Calcium having a mass ratio of 1% or more and 5% or less to the biomass, or
The method for gasifying biomass according to claim 1, wherein potassium and calcium having a total mass ratio of 2% or more and 10% or less with respect to the biomass are supported. The method for gasifying biomass according to claim 1 or 2, wherein the biomass used in the catalyst-supporting step has a constant moisture content of 20% or less according to an industrial analysis method. The method for gasifying biomass according to any one of claims 1 to 3, wherein the biomass to be used in the catalyst-supporting step has an ash content of 10% by mass or less according to an industrial analysis method. The method for gasifying biomass according to any one of claims 1 to 4, wherein the biomass to be used in the catalyst-supporting step has a fixed carbon content of 10% or more and 30% or less according to an industrial analysis method. The method for gasifying biomass according to any one of claims 1 to 5, further comprising a drying step of drying the catalyst-supported biomass until the water content becomes 15% or less prior to the semi-carbonization step. The method for gasifying biomass according to any one of claims 1 to 6, wherein the gasification step is carried out at a pressure of 0.5 MPa or more. The gasification step according to any one of claims 1 to 7, wherein the S / C ratio, which is the molar ratio of the water vapor S to the substance amount C of carbon atoms in the catalyst-supported biomass, is 1 or more and 10 or less. The method for gasifying biomass according to the description.