JP2003268388A - Biomass pyrolysis method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that a large grinding installation is necessary for grinding biomass to a minute size sufficient for gasification since an excessively large quantity of energy is required for grinding it because of its properties, and that a huge reactor is necessary for effecting the reaction by using large particles of a biomass, both of which are unrealistic from an economical viewpoint. <P>SOLUTION: The reaction of decomposition of the biomass is performed in a jet layer, and the residence time is adjusted by the rising gas flow velocity, thus uniformalizing the degree of reaction of particles different in particle diameter. As a result, a method of thermal decomposition without using a grinding installation can be realized. An economical process can be realized by partitioning the ground material from one grinder according to the particle sizes so as to allow the use of the biomass suitable for each of thermal decomposition and gasification. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for rapidly pyrolyzing biomass by utilizing sensible heat of high temperature gas.

[0002]

2. Description of the Related Art To deal with the problem of global warming, the development and practical application of new energy, the shift to low carbon dioxide generation energy, the improvement of the nuclear power ratio, the efficient and rational use of existing primary energy, and the unused energy It is being promoted by using energy and waste energy. In particular, biomass is carbon neutral, and the Conference of the Parties to the United Nations Framework Convention on Climate Change (C
OP3-6, COP; The Conference
It can be said that it is a resource that should be actively used to replace petroleum, coal, etc. in the sense of achieving international commitments under the Of Party. Biomass is a general term for biomass, and according to FAO (United Nations Food and Agriculture Organization), agricultural systems (straw straw, sugar cane, rice bran, vegetation, etc.), forestry systems (paper waste, lumber waste, thinned timber, firewood charcoal forest) Etc.), livestock system (livestock waste), fisheries system (results of marine product processing), waste system (raw garbage,
RDF (solid waste fuel; Refused Deriv)
ed Fuel), garden trees, construction waste, sewage sludge), etc.

Considering energy recovery from biomass and energy conversion, a low efficiency method is usually used in which steam is generated by sensible heat of generated gas by combustion and is recovered as electric power by a steam turbine. This is because biomass generally contains a large amount of water and has a low amount of heat, and because the heat required for pyrolysis and gasification is insufficient, there is only a choice for combustion, and heat from the outside (heat from other fuels compensation)
There are many processes that cannot be achieved without it. Therefore, in order to recover energy from biomass and use it effectively, a method with high conversion efficiency is essential. Although there is no conventional technique using the same technique as the present invention, among the similar techniques, as a technique for converting biomass to gas energy, in recent years, Japanese Patent Laid-Open No. 11-302665 "using biomass and fossil fuels has been used. There is a technology of applying the partial oxidation process to biomass, which is seen in the "gasification method".

[0004]

In the prior art, when biomass was partially oxidized (gasified) with an oxidizing agent, it was necessary to finely pulverize the biomass in order to increase the reaction rate.
Coal (pulverized coal) gasification, which is an established field, is 50 to 1
Used after being crushed to an average particle size of 00 μm, biomass has strength and toughness directionality (strong fiber direction), and existing crushers (hammer type, mill type) produce crushed products of less than a few mm. It requires several times more power than coal. Therefore, the method of pulverization is economical and realistic, with a size of several mm, and the method of obtaining the reaction rate in the direction of increasing the reaction time is used. Therefore, in the partial gasification mainly in the airflow layer, the furnace volume is expanded and the reaction rate is lowered. This was one of the causes of increased equipment costs and reduced efficiency.

Therefore, the present invention provides a method of effectively utilizing the heat quantity of biomass, which is applicable to even coarse particles by selecting a method in which thermal decomposition is carried out by sensible heat of gasification and using a reaction mode suitable for biomass. The purpose is to do.

[0006]

The present invention is an effective method for solving the above problems. 1) The products of gas, tar and char are produced by a pyrolysis reaction in a spouted bed using biomass as a pyrolysis raw material. In the method for the thermal decomposition of biomass, the heat source for the thermal decomposition reaction is 8
A biomass pyrolysis method using a high-temperature gas of 00 ° C or higher, wherein the rising velocity of gas in the pyrolysis unit is 1 m / sec to
Biomass pyrolysis method, characterized in that it is set to 15 m / sec, 2) When biomass is used as a gasification raw material and oxygen or a gas obtained by gasification with oxygen and steam is used as a heat source for a pyrolysis reaction, pulverization 1) The biomass pyrolysis method described in 1), 3) a gasification furnace, characterized in that the biomass having a small particle size is used as a gasification raw material, and the biomass having a coarse particle size is used as a pyrolysis raw material. Pyrolysis part, connection part connecting the gasification furnace and the pyrolysis part, a biomass crusher, a sieving device for sieving pulverized products in the biomass crusher, and sieved on-screen particles In the pyrolysis part, a biomass pyrolysis device equipped with a supply device for supplying the undersize particles to the gasification furnace,
Consists of.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present specification, the definition of biomass follows the definition of FAO. In addition, among the products generated when pyrolyzing biomass, the solid content is char (biomass char), and the component that becomes liquid at room temperature is tar. The spouted bed is a solid-gas mixture layer in which solids are present in the ascending gas flow, and is a layer in which particles are circulated and accumulated due to the balance between the propulsive force (resistance) due to the gas flow and gravity. Particles with a higher specific gravity have a longer residence time in the circulation part. The general profile of the spouted bed outlet is that the rising gas outlet area is smaller than the spouted bed area, and high-speed gas / particle upward flow in the center part is opposite in the peripheral part (near the wall surface). A downward flow occurs in the particles, and the particles circulate and accumulate.

Next, an embodiment of the present invention will be described with reference to the drawings. That is, as shown in FIG. 1, the thermal decomposition part 1 of biomass is supplied with the biomass 3 by the thermal decomposition part biomass supply device 2. The supplied biomass 3 is rapidly heated and thermally decomposed by the high temperature gas 5 of 800 ° C. or higher supplied from the gasification furnace 8 through the connecting portion 4. For the temperature range of the hot gas 5, 800
When the temperature is lower than ℃, the sensible heat of gas required for thermal decomposition is insufficient. As the sensible heat of gas required for the thermal decomposition, 4
A temperature of 00 ° C or higher can be used as a guide. Further, the temperature upper limit of the high temperature gas is not particularly specified, and may be set appropriately in consideration of facility restrictions (furnace material etc.) due to high temperature. However, from the viewpoint of the radiated heat that increases as the furnace temperature rises and the stability of the furnace wall component that increases the fluidity as the temperature rises, 1700 ° C. or lower is preferable, and 1600 ° C. or lower is preferable.

The lower structure of the thermal decomposition part 1 is a tapered part 7 which is generally inclined due to the formation of the spouted bed 6,
An ascending flow of the hot gas 5 exists in the center, and a gas descending flow 9 exists near the wall surface. Downstream from the taper part 7 (post-stage side)
In the thermal decomposition section 1, the generated gas is conveyed to the subsequent stage at an ascending flow rate determined by the amount of high temperature gas, the amount of thermally decomposed product gas, and the ambient temperature / pressure. The rising flow velocity referred to in the present invention refers to the actual flow velocity of gas in the pyrolysis reactor, and is a numerical value obtained by correcting the gas flow rate (standard state) with the gas temperature and atmospheric pressure and dividing by the flow passage cross-sectional area (this In the case of the thermal decomposition section). When the shape of the reactor is complicated, the flow velocity at the portion near the connection portion 4 where the flow velocity is the slowest (the flow passage cross-sectional area is large) is used as the rising flow velocity. This is because the thermal decomposition reaction itself is a short-time reaction, and therefore the reaction in the place near the contact point with the high temperature gas (that is, the temperature is high and the reaction rate is fast) represents the entire reaction.

As shown in FIG. 1, when the pyrolysis unit 1 is a straight pipe and the internal temperature change is small, the amount of gas measured at the latter stage of the pyrolysis unit is divided by the cross-sectional area of the straight pipe. ,
An average flow velocity that is easy to calculate may be used. Immediately after being charged, the biomass particles circulate and stay in the spouted bed 6 due to the gas rising speed, reactor shape, particle shape / property, etc. However, due to reaction, the particle size and density decrease over time, which causes the rising gas. The driving force becomes relatively large, and the biomass particles are discharged to the latter stage. The condition is that the concept of terminal sedimentation velocity in spherical particles can be roughly applied, and the propulsive force (resistance) due to rising gas flow exceeds gravity, but particle morphology, internal pore volume (affecting density) Since it greatly changes depending on the reaction progress mode, particle position, etc., it is difficult to uniquely determine by calculation.

In the present invention, the flow rate condition, which is obtained from the experiment and allows the reaction to proceed sufficiently regardless of the particle size of the raw material, is defined. A specific flow velocity condition is an ascending flow velocity of 1 to 15 m / sec. If it is less than 1 m / sec, the amount of biomass retained in the furnace increases, so that the biomass density per unit volume increases, heat transfer and flow of reaction product gas are hindered, and pressure loss in the spouted bed 6 is reduced. It is not preferable because it increases and the operation becomes unstable. Further, when it exceeds 15 m / sec, only large particles can be retained, and due to insufficient reaction, the number of particles discharged to the subsequent stage increases in a short time and the reaction rate decreases. Of the above conditions, 2 to 10 m / sec is more preferable because it is a flow rate condition at which thermal decomposition sufficiently progresses and the operation is stable.

FIG. 1 shows a case where biomass is used as a gasification raw material and oxygen or a gas obtained by gasifying with oxygen and steam is used as a heat source for a thermal decomposition reaction. That is, the case where gasification and thermal decomposition are combined is shown. In this case, the biomass 3 is supplied to the biomass pyrolysis unit 1 by the pyrolysis unit biomass supply device 2. The supplied biomass 3 is 800 from the connection part 4.
The temperature is rapidly raised by the high temperature gas 5 of ℃ ~ 1700 ℃,
Pyrolyzed. Regarding the gasification temperature range (that is, the temperature of the high-temperature gas 5), when the temperature is less than 800 ° C, the overall efficiency is low due to insufficient sensible heat of gas required for thermal decomposition and generation of unburned materials due to a decrease in gasification reaction rate descend. Further, when the temperature exceeds 1700 ° C., facility restrictions due to high temperatures (furnace materials, etc.) and a decrease in the gasification reaction rate due to the formation of a large amount of soot occur.

At present, in the biomass pulverization, the grain size of about several mm is economically and practically the pulverization limit. As a crushing method, there are an impact type (hammer type, rod type, etc.), a cutting type (rotary blade cutting type, screw blade type, etc.), a mortar type mill, etc., but a hammer type is used for crushing a size of 10 mm or more,
A hammer type + rod type or a cutting type is mainly used for crushing a size of less than 10 mm. Further, for pulverization up to about 2 mm, a cutting die is mainly used as an equipment configuration, but since the required power is large, the processing capacity is small. Originally, in order to allow the thermal decomposition reaction to be sufficiently carried out in a short time, the smaller the particle size, the better (the particle size here is from the viewpoint of the reaction,
We shall refer to the short diameter). In order to react with a typical pyrolysis reaction time of several seconds in a typical air flow bed type furnace different from the present invention, the biomass needs to have a size of 100 μm to at most 1 to 2 mm. In the impact-type pulverization method, the pulverized product of biomass, which has the characteristic that the strength is strong in the fiber direction, has a wide particle size distribution (it is difficult to make the impact direction constant with respect to the fiber direction). It is difficult to make the same biomass react. Therefore, in the gasification of the gas stream, the upper limit of the particle size is inevitably controlled (for example, the total amount is less than 2 mm), and a crusher having a large crushing power and a low processing capacity such as a cutting die must be used.

In the present invention, by forming a spouted bed,
Fine particles react in a short time, large particles react in a long time,
It is possible to arrange the reaction degree of the particles discharged in the latter stage. As a result, even with biomass having a coarse particle size of 10 mm or more, by appropriately setting the rising flow rate, the biomass particles can be retained in the spouted bed and sufficiently reacted. Therefore, in the present invention, it has been found that it is possible to select a low-power crushing equipment such as an impact type, and it is possible to pyrolyze a large amount of biomass.

In the present invention, the gasification method was also examined. There are many candidates for high-temperature gas raw materials required for pyrolyzing biomass, such as natural gas and LPG gas fuel, carbonaceous raw materials such as coal, petroleum, and heavy oil, but biomass is also used as a gasification raw material. By doing so, it is possible to build an economical process that minimizes other external fuels.

However, in regard to the gasification of biomass, it is necessary to use a gasification method in an airflow layer in order to allow the reaction to proceed sufficiently, and as described above, for example, it is necessary to pulverize the whole amount to a diameter of less than 2 mm. Occurs. Therefore,
We devised a usage method that can be sufficiently applied with an impact type crusher aiming at 10 to 20 mm. That is, the wide particle size distribution characteristics of the above-mentioned impact type crusher are used in reverse, by sieving the crushed biomass into coarse particles and fine particles, the coarse particles are pyrolyzed, and the fine particles are gasified. It is to use. FIG. 2 shows an example of a reactor having a biomass supply mechanism by particle size distribution. In the configuration of FIG.
A biomass crusher 10, a particle size distribution mechanism 11, and a gasified biomass supply device 12 are added, and the particle size distribution mechanism 11
Can be carried out by using a screen, an air classifier, or the like. In the figure, the same reference numerals as those in FIG. 1 denote the same members.

Further, in the present invention, the definitions of coarse particles and fine particles are differences in relative particle sizes when comparing the two, and do not particularly specify the particle size. However, when operating in a gasification furnace having an efficient air flow layer, in reality, fine particles having a size of less than 10 mm are handled, and in view of reactivity, the particle size is preferably 5 to 6 mm or less. Coarse particles mean particles other than the above-mentioned fine particles.

[0018]

EXAMPLES Next, the present invention will be described in more detail with reference to examples.

Example 1 A test was carried out in which the biomass was crushed by a hammer crusher, which is one of the collision crushers, and the crushed biomass was put into the thermal decomposition section 1. Biomass particle size is 10% by mass with a short diameter of less than 10 mm, 60% by mass of 10 mm or more and less than 50 mm, 50 mm
The above was 30% by mass and coarse particles. In general, pulverized biomass has a large difference between the short diameter and the long diameter, and it is difficult to define a representative value. In this case, for example, the particles under the sieve that have passed through a screen of 10 mm × 10 mm sieve mesh for a sufficient time are “ Minor particles less than 10 mm ", also 10 mm
50m on the screen of a screen with a 10mm screen
Particles under the sieve of a screen of mx 50 mm sieve are "particles with a short diameter of 10 mm or more and less than 50 mm", 50 mm
The particles on the screen of the screen with a screen size of 50 mm × 50 mm were defined as “particles having a short diameter of 50 mm or more”.

The high-temperature gas as a heat source for the pyrolysis temperature contains L
When using PG combustion gas (Pyrolysis biomass amount 160
kg / hr, the above-mentioned high temperature gas temperature 1200 ° C, pyrolysis temperature 700 ° C, rising flow rate 4m / s), and 81% of the amount of pyrolysis biomass was converted to gas and tar. Even if a large particle size biomass is used, the volatile content of the biomass (industrial analysis value;
It was confirmed that about 83% by mass) was almost volatilized and that it was sufficiently heated.

Example 2 An example of separating gasifiable particles having a short diameter of less than 2 mm is shown below. When a hammer type biomass crusher 10 aiming at a crushing diameter of 20 mm is used and distribution is performed using a screen having an opening of 2 mm × 2 mm, particles having a short diameter of less than 2 mm are about 3 particles.
It became 0 mass%. As a result, an inexpensive impact-type (hammer-type) crusher is used without introducing a cutting-type crusher that has large power for gasification and is disadvantageous in terms of cost, and the biomass 70 with a short diameter and a particle size of 2 mm or more is used. % By mass was used for pyrolysis, and 30% by mass of biomass with a short diameter and a particle size of less than 2 mm was used for gasification. For example, biomass gasification amount 70kg
/ Hr, oxygen 40Nm3 / hr, steam 10kg / h
r, gasification temperature 1200 ° C, pyrolysis biomass amount 160
kg / hr, pyrolysis temperature 700 ° C, rising flow rate 4 m / s
When ec is set (adjusted by pressure), the amount of biomass gasification is 9
5% converted to hot gas, 82% of biomass pyrolysis
Converted to gas and tar. As in Example 1, the volatile components of the pyrolyzed biomass are almost volatilized and are sufficiently heated.

The size of the branch point for particle size separation (2 mm in the above case) can be adjusted by changing the rising flow rate (for example, when the ratio of the size of less than 2 mm is less than 30% by mass depending on the raw material properties, By setting the rising flow velocity to a large value by adjusting the pressure etc., the branch point size can be made large, for example, 3 mm, and the amount necessary for gasification can be secured.) This is a highly flexible facility.

[0023]

EFFECTS OF THE INVENTION According to the present invention, it is possible to stably proceed the thermal decomposition reaction even with biomass having a large particle size. In addition, as a result, it becomes possible to select the equipment configuration without using a cutting-type crushing equipment having a large power and a small throughput. In addition, the use of a sieving device allows pyrolysis with minimal external fuel.

[Brief description of drawings]

FIG. 1 is a schematic view of a spouted bed biomass gasification furnace and a pyrolysis unit.

FIG. 2 is a schematic diagram of a biomass supply device by particle size distribution.

[Explanation of symbols]

1 ... Thermal decomposition part 2 Pyrolysis section biomass supply device 3 ... Biomass 4 ... Connection part 5 ... High temperature gas 6 ... Spout layer 7 ... Tapered part 8 ... Gasification furnace 9 ... Gas downflow 10 ... Biomass crusher 11 ... Grain size distribution mechanism 12 ... Gasification biomass supply device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B09B 3/00 ZAB B09B 3/00 Z 5/00 5/00 Z (72) Inventor Haruta Shioda Chiba Prefecture 20-1 Shintomi, Futtsu-shi Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Atsushi Fujikawa 46-59 Nakahara, Tobata-ku, Kitakyushu, Fukuoka Prefecture F-Term (Reference) 4D004, Engineering Business Division, Nippon Steel Corporation AA01 CA04 CA08 CA24 CA27 CB01 DA03 DA06 DA20 4D021 AA03 EA10 EB01

Claims (3)

[Claims] 1. A high-temperature gas of 800 ° C. or higher is used as a heat source of the pyrolysis reaction in a biomass pyrolysis method for obtaining a product of gas, tar and char by a pyrolysis reaction in a spouted bed using biomass as a pyrolysis raw material. Biomass pyrolysis method, in which the rising velocity of gas in the pyrolysis unit is 1 m
/ Sec to 15 m / sec, biomass pyrolysis method 2. When using biomass as a gasification raw material and oxygen or a gas obtained by gasifying with oxygen and steam as a heat source for a thermal decomposition reaction, crushed pulverized biomass is sieved to gasify fine-grained biomass. The biomass pyrolysis method according to claim 1, characterized in that biomass having a coarse grain size is used as a raw material and as a pyrolysis raw material. 3. A gasification furnace, a thermal decomposition section, a connecting section connecting the gasification furnace and the thermal decomposition section, and a biomass crusher,
Biomass pyrolyzer equipped with a sieving device for sieving the pulverized material in the biomass pulverizer, and a supply device for supplying the sieved particles on the screen to the thermal decomposition part and the particles under the screen to the gasification furnace.