JP7051384B2 - Biomass gasifier and its operation method - Google Patents

Description

The present invention relates to a biomass gasification apparatus for gasifying granular biomass fuel and an operation method thereof.

A biomass gasifier that gasifies biomass fuel is known (Patent Document 1). The liquefied fuel produced by gasification by the biomass gasifier is considered to be a fuel with less environmental load than fossil fuel.

Japanese Unexamined Patent Publication No. 2012-246439

A jet bed type gasification furnace that supplies granular biomass fuel to a gasification furnace and gasifies it is advantageous because it is relatively compact and can be increased in capacity because it gasifies at high speed.
However, even if the granular biomass fuel is supplied into the gasification furnace, if the gas flow velocity in the gasification furnace is less than the terminal speed, the granular biomass fuel will fall in the gasification furnace and gasify. There is a risk that the reaction will not be carried out sufficiently and the gas will be discharged.

On the other hand, if the particle size of the biomass fuel is reduced in order to sufficiently gasify (for example, about 1 mm), the crushing power of the crusher that crushes the biomass fuel increases accordingly, which leads to a decrease in plant efficiency. It ends up.

In view of such circumstances, it is an object of the present disclosure to provide a biomass gasifier and an operation method thereof capable of sufficiently gasifying granular biomass fuel without causing a decrease in plant efficiency.

The biomass gasification apparatus according to at least one aspect of the present disclosure includes a gasifier main body in which the first cylinder portion, the second cylinder portion and the third cylinder portion are connected in order from the lower side to the upper side from the upstream side of the gas flow. , A granular biomass fuel connected to the first cylinder portion and supplying a gasifying agent and a granular biomass fuel connected to the second cylinder portion and having an average sieve particle size of 0.5 mm or more and 3 mm or less. When the representative diameter of the first cylinder portion is 1, the representative diameter of the second cylinder portion is 3 or more and 4.5 or less, and the representative diameter of the third cylinder portion is 1. The representative diameter is 6.5 or more and 7.5 or less.

By supplying the gasifying agent from the gasifying agent supply unit to the first cylinder portion, a gas flow is formed in the order of the first cylinder portion, the second cylinder portion, and the third cylinder portion.
By supplying the granular biomass fuel to the second cylinder portion from the biomass fuel supply unit, the biomass fuel is gasified by reacting with the gasifying agent derived from the first cylinder portion to perform partial oxidative combustion. As described above, the biomass gasification device is a jet bed type.
The particle size of the granular biomass fuel decreases as the gasification reaction progresses. Therefore, even if the particles have a large particle size at the beginning of supply and decrease without increasing due to a gas flow velocity lower than the terminal velocity, the particle size becomes smaller as the reaction progresses, and finally the gas flow exceeds the terminal velocity. It is blown up by riding on.
Since the flow velocity of the gas flow passing through the gasification furnace main body is inversely proportional to the flow path cross-sectional area of each cylinder portion if the gas flow rate is constant, it is determined by the representative diameter of each cylinder portion. As a result of diligent studies by the present inventors, in the case of a biomass fuel having an average sieve particle size of 0.5 mm or more and 3 mm or less, when the representative diameter of the first cylinder portion is 1, the representative diameter of the second cylinder portion is used. It was confirmed that the biomass fuel was sufficiently gasified by setting the representative diameter of the third cylinder portion to 3 or more and 4.5 or less and the representative diameter of the third cylinder portion to 6.5 or more and 7.5 or less. Therefore, it is not necessary to crush the biomass fuel to about 1 mm, and the power of the crusher can be reduced to improve the plant efficiency.
The representative diameter means the so-called equivalent hydraulic diameter, and means the diameter of the circular pipe equivalent to the cross section of the flow path having a predetermined shape. Therefore, when the tubular portion is a cylinder, it corresponds to the diameter thereof.
As the biomass fuel, a wood-based biomass fuel is typically used.
As the gasifying agent, for example, oxygen and water vapor having a temperature of 400 ° C. or higher and 600 ° C. or lower are used.
For the biomass fuel supply unit, for example, a mechanical transfer method such as a screw feeder is used.
Terminal velocity is synonymous with terminal velocity, which is the velocity at which the gravity acting on an object and the drag that depends on the velocity are balanced and do not change.

Further, in the biomass gasifier according to at least one aspect, the representative diameter of the first cylinder portion is set to a size that can obtain the terminal rate of the maximum particle size of the biomass fuel.

By setting the representative diameter of the first cylinder portion to a size that allows the final rate of the maximum particle size of the biomass fuel to be obtained, the biomass fuel supplied from the biomass fuel supply portion descends below the first cylinder portion. It can be suppressed. This makes it possible to improve the gasification reaction of the biomass fuel. The terminal velocity in the first cylinder portion can be obtained by using the flow rate of the gasifying agent supplied from the gasifying agent supply unit.
The maximum particle size of the biomass fuel is preferably 10 mm, more preferably 8 mm.

Further, in the biomass gasification apparatus according to at least one aspect, the inclination angle of the connection portion between the first cylinder portion and the second cylinder portion and the connection portion between the second cylinder portion and the third cylinder portion is set. , It is said to be above the angle of repose.

Since the representative diameters of the first cylinder portion, the second cylinder portion, and the third cylinder portion are different from each other, an inclined wall portion is formed at the connection portion. By setting the inclination angle of the connection portion to the angle of repose or more (for example, 50 ° or more), particles can be guided downward without accumulating particles on the connection portion.

Further, in the biomass gasification device according to at least one aspect, a discharge valve is provided below the first cylinder portion.

By providing an discharge valve below the first cylinder portion, the deposits accumulated in the furnace are discharged to the outside of the furnace. As a result, it is possible to prevent the bottom of the furnace from being blocked.
Examples of the deposits deposited on the bottom of the furnace include stones and sand mixed in the biomass fuel.

The method of operating the biomass gasification apparatus according to at least one aspect of the present disclosure is gasification in which the first cylinder portion, the second cylinder portion and the third cylinder portion are connected in order from the lower side to the upper side from the upstream side of the gas flow. Granules connected to the furnace body, the gasifying agent supply unit connected to the first cylinder portion and supplying the gasifying agent, and the second cylinder portion having an average sieving particle size of 0.5 mm or more and 3 mm or less. The second cylinder portion is provided with a biomass fuel supply unit for supplying the biomass fuel of the above and a discharge valve provided below the first cylinder portion, and the representative diameter of the first cylinder portion is 1. The representative diameter of the biomass gasification device is 3 or more and 4.5 or less, and the representative diameter of the third cylinder portion is 6.5 or more and 7.5 or less. It is opened after a predetermined operation time has elapsed.

By opening the discharge valve provided below the first cylinder portion after the lapse of a predetermined operation time, the deposit accumulated in the furnace is discharged to the outside of the furnace. As a result, it is possible to prevent the bottom of the furnace from being blocked.
The timing for opening the discharge valve may be determined based on the operating time or the amount of deposits deposited in the furnace.

Further, in the operation method of the biomass gasifier according to at least one aspect, when the exhaust valve is opened, the supply of the biomass fuel and the gasifier is stopped, the exhaust valve is closed, and then the exhaust valve is closed. The supply of water vapor of the gasifying agent, the biomass fuel, and oxygen of the gasifying agent is started in this order.

By stopping the supply of biomass fuel and gasifying agent when the discharge valve is opened, the gasification reaction is temporarily stopped to ensure the discharge of sediment.
After that, when the exhaust valve is closed and the gasification reaction is restarted, the supply of steam, biomass fuel, and oxygen is started in this order. By supplying oxygen last in this way, a rapid oxidation reaction (for example, a combustion reaction) can be avoided.

By optimizing the representative diameters of the first cylinder, the second cylinder, and the third cylinder, the granular biomass fuel can be sufficiently gasified without causing a decrease in plant efficiency.

It is a schematic block diagram which showed the biomass gasification apparatus which concerns on at least one Embodiment. It is a graph which showed the terminal velocity ratio with respect to the particle diameter in the lower cylinder part. It is a graph which showed the terminal velocity ratio with respect to the particle diameter in the middle cylinder part and the upper cylinder part.

Hereinafter, the biomass gasification apparatus according to at least one embodiment will be described.
FIG. 1 shows a biomass gasification device 1. The biomass gasification device 1 includes a gasification furnace main body 3 for gasifying biomass fuel. Gasification in the gasifier main body 3 is performed at atmospheric pressure.

The gasification furnace main body 3 is provided with a lower cylinder portion (first cylinder portion) 4, a middle cylinder portion (second cylinder portion) 5, and an upper cylinder portion (third cylinder portion) 6 in this order from the bottom to the top. ing. A first connection portion 8 is provided between the lower cylinder portion 4 and the middle cylinder portion 5, and a second connection portion 9 is provided between the middle cylinder portion 5 and the upper cylinder portion 6.

The lower tubular portion 4 has a cylindrical shape having an inner diameter (representative diameter) of ΦL. A gasifying agent supply pipe (gasifying agent supply unit) 10 for supplying the gasifying agent is connected to the lower side wall portion of the lower cylinder portion 4. As a result, the gas flow of the gasifier main body 3 is formed so as to go from the lower side to the upper side.

Oxygen and water vapor are used as the gasifying agent. The water vapor is set to 400 ° C. or higher and 600 ° C. or lower, and is supplied into the lower cylinder portion 4 at atmospheric pressure. Oxygen is brought to room temperature and is supplied into the lower cylinder portion 4 at atmospheric pressure. Therefore, the gas temperature in the lower cylinder portion 4 is set to 400 ° C. or higher and 600 ° C. or lower.

The gas flow velocity VL flowing through the lower cylinder portion 4 is set to be the terminal velocity when the particle diameter of the biomass fuel is 10 mm (or 8 mm), which is the maximum diameter. Specifically, it is determined using the graph shown in FIG. In the figure, the horizontal axis is the particle size (mm) of the biomass fuel, and the vertical axis is the terminal velocity ratio. The terminal velocity ratio is normalized based on the case where the particle size is 0.2 mm. As can be seen from the figure, when the maximum diameter of the biomass fuel particles is set to 10 mm, the terminal velocity ratio is around 40. The flow rate of the gasifying agent supplied from the gasifying agent supply pipe 10 and the inner diameter ΦL of the lower cylinder portion 4 are determined so as to match this terminal velocity ratio.

As shown in FIG. 1, a discharge valve 12 is provided at the lower end of the lower cylinder portion 4. The discharge valve 12 is fully closed during normal operation and fully opened when the deposits accumulated in the lower cylinder portion 4 are discharged. The opening / closing operation of the discharge valve 12 may be performed by a control unit (not shown) or may be performed manually.

The middle cylinder portion 5 has a cylindrical shape having an inner diameter (representative diameter) ΦM larger than that of the lower cylinder portion 4. The inner diameter ΦM of the middle cylinder portion 5 is 3 or more and 4.5 or less when the inner diameter ΦL of the lower cylinder portion 4 is 1.

A biomass fuel supply unit 14 for supplying biomass fuel is connected to the side wall portion of the central cylinder portion 5. Biomass fuel is considered to be wood-based such as wood scraps, sawdust, and wood pellets. The biomass fuel supply unit 14 is provided with a mechanical transfer device such as a screw feeder. Granular biomass fuel is quantified from the biomass fuel supply unit 14 and charged into the central cylinder portion 5. As described above, the biomass gasification device 1 of the present embodiment is a jet bed type.
Biomass fuel is gasified in the central cylinder portion 5. The gas temperature in the central cylinder portion 5 is 900 ° C. or higher and 1050 ° C. or lower.

A crusher (mill) (not shown) is connected to the upstream side of the biomass fuel supply unit 14. Woody biomass fuel is crushed to a predetermined particle size by a crusher. In the present embodiment, the biomass fuel has an average sieve particle size of 0.5 mm or more and 3 mm or less, and a maximum particle size of 10 mm, more preferably 8 mm. That is, a biomass fuel larger than 1 mm is used.

The average particle size of the sieve is obtained from a value of 50% by sieving the sample using, for example, a sieve specified in JIS Z8801, measuring the mass of the sample remaining on each sieve, and creating a cumulative distribution on the graph. Be done.

The first connecting portion 8 connecting the lower tubular portion 4 and the middle tubular portion 5 has a conical trapezoidal shape. The angle α formed by the inclined wall portion forming the conical trapezoid with respect to the vertical direction is set to be the angle of repose or more (for example, 50 ° or more).

The upper cylinder portion 6 has a cylindrical shape having an inner diameter (representative diameter) ΦU larger than that of the middle cylinder portion 5. The inner diameter ΦU of the upper cylinder portion 6 is 6.5 or more and 7.5 or less when the inner diameter ΦL of the lower cylinder portion 4 is 1.
In the upper cylinder portion 6, the biomass fuel is gasified. The gas temperature in the upper cylinder portion 6 is 900 ° C. or higher and 1050 ° C. or lower.
An exhaust portion 16 is connected to the upper end of the upper cylinder portion 6. Gasified gas or char, which is a gasification of biomass fuel, is discharged from the exhaust unit 16 and guided to a processing facility on the downstream side.

The second connecting portion 9 connecting the middle tubular portion 5 and the upper tubular portion 6 has a conical trapezoidal shape. The angle α formed by the inclined wall portion forming the conical trapezoid with respect to the vertical direction is set to be the angle of repose or more (for example, 50 ° or more).

FIG. 3 shows the grounds that the inner diameter ratio of the inner diameter ΦM of the middle cylinder portion 5 to the inner diameter ΦL of the lower cylinder portion 4 is 3 or more and 4.5 or less, and the inner diameter of the lower cylinder portion 4 of the inner diameter ΦU of the upper cylinder portion 6. The grounds for setting the inner diameter ratio to ΦL to 6.5 or more and 7.5 or less are shown.

In FIG. 3, as in FIG. 2, the horizontal axis indicates the particle size (mm) of the biomass fuel, and the vertical axis indicates the terminal velocity ratio. However, unlike FIG. 2, it reflects the increase in temperature and the amount of gas due to gasification.

In the range of the inner diameter ratio of 3 or more and 4.5 or less, the biomass fuel having a particle size of about 0.9 mm to 2 mm has a terminal velocity, so that the gasification reaction is carried out while staying in the central cylinder portion 5. When the gasification reaction is carried out, the particle size becomes smaller and rises toward the upper cylinder portion 6.
In the range of the inner diameter ratio of 6.5 or more and 7.5 or less, the particle size of the biomass fuel is about 0.32 to about 0.4, which is the terminal velocity. Is done. When the gasification reaction is carried out, the particle size becomes smaller and rises toward the exhaust portion 16.
As described above, when the inner diameter ratio is set as described above, the maximum particle size is 10 mm, and it can be seen that if the biomass fuel has an average sieve particle size of 0.5 mm or more and 3 mm or less, gasification is sufficiently performed. ..

Next, the operation method of the above-mentioned biomass gasification device 1 will be described.
The discharge valve 12 is closed during the gasification operation, but is temporarily opened after the operation time has elapsed. As a result, the deposits accumulated in the furnace are discharged to the outside of the furnace. Examples of the deposit include stones and sand mixed in the biomass fuel. The timing for opening the discharge valve 12 may be determined based on the operating time or may be determined based on the amount of deposits deposited in the furnace.

When the discharge valve 12 is opened, the supply of the biomass fuel and the gasifying agent is stopped. The stop time is, for example, 5 to 10 seconds.

When the gasification reaction is restarted by closing the discharge valve 12, the supply of steam, biomass fuel, and oxygen is started in this order. By supplying oxygen last in this way, a rapid oxidation reaction (for example, a combustion reaction) can be avoided.

According to the biomass gasification device 1 of the present embodiment, the following effects are exhibited.
The particle size of the granular biomass fuel decreases as the gasification reaction progresses. Therefore, even if the particles have a large particle size at the beginning of supply and decrease without increasing due to a gas flow velocity lower than the terminal velocity, the particle size becomes smaller as the reaction progresses, and finally the gas flow exceeds the terminal velocity. It is blown up by riding on.
Since the flow velocity of the gas flow passing through the gasification furnace main body 3 is inversely proportional to the flow path cross-sectional area of each cylinder portion 4, 5, 6 if the gas flow rate is constant, each cylinder portion 4, 5, 6 It is determined by the inner diameters of ΦL, ΦM, and ΦU. As a result of diligent studies by the present inventors, in the case of a biomass fuel having an average sieve particle size of 0.5 mm or more and 3 mm or less, when the inner diameter ΦL of the lower cylinder portion 4 is 1, the inner diameter ΦM of the middle cylinder portion 5 is set. It was confirmed that the biomass fuel can be sufficiently gasified by setting the inner diameter ΦU of the upper cylinder portion 6 to 3 or more and 4.5 or less and the inner diameter ΦU to 6.5 or more and 7.5 or less. Therefore, it is not necessary to crush the biomass fuel to about 1 mm, and the power of the crusher can be reduced to improve the plant efficiency.

By setting the inner diameter ΦL of the lower cylinder portion 4 to a size that allows the terminal rate of the maximum particle size of the biomass fuel to be obtained, the biomass fuel supplied from the biomass fuel supply portion 14 descends below the lower cylinder portion 4. Can be suppressed. This makes it possible to improve the gasification reaction of the biomass fuel.

Since the inclination angle of the connecting portions 8 and 9 is set to the angle of repose or more (for example, 50 ° or more), the particles can be guided downward without being deposited on the connecting portions 8 and 9.

By providing the discharge valve 12 below the lower cylinder portion 4, it was decided to discharge the deposits accumulated in the furnace to the outside of the furnace. As a result, it is possible to prevent the bottom of the furnace from being blocked.

In the above-described embodiment, the shapes of the lower cylinder portion 4, the middle cylinder portion 5, and the upper cylinder portion 6 have been described as a cylindrical shape, but other shapes such as a polygon such as a quadrangle may be used. In this case, the equivalent hydraulic diameter is used as the representative diameter.

1 Biomass gasifier 3 Gasifier body 4 Lower cylinder (1st cylinder)
5 Middle cylinder (second cylinder)
6 Upper cylinder (third cylinder)
8 1st connection 9 2nd connection 10 Gasifier supply pipe (gasifier supply)
12 Exhaust valve 14 Biomass fuel supply part 16 Exhaust part ΦL Inner diameter of lower cylinder part (representative diameter)
Inner diameter of ΦM middle cylinder (representative diameter)
ΦU Inner diameter of upper cylinder (representative diameter)

Claims (6)

A gasifier main body in which the first cylinder, the second cylinder, and the third cylinder are connected in order from the lower side to the upper side from the upstream side of the gas flow.
A gasifying agent supply unit connected to the first cylinder portion and supplying a gasifying agent,
A biomass fuel supply unit connected to the second cylinder unit and supplying granular biomass fuel having an average sieve particle size of 0.5 mm or more and 3 mm or less.
Equipped with
When the representative diameter of the first cylinder portion is 1,
The representative diameter of the second cylinder is 3 or more and 4.5 or less.
A biomass gasification device having a representative diameter of 6.5 or more and 7.5 or less. The biomass gasification device according to claim 1, wherein the representative diameter of the first cylinder portion is a size that allows the terminal velocity of the maximum particle size of the biomass fuel to be obtained. Claim 1 or 2 in which the inclination angle of the connection portion between the first cylinder portion and the second cylinder portion and the connection portion between the second cylinder portion and the third cylinder portion is equal to or more than the angle of repose. Biomass gasifier according to. The biomass gasification device according to any one of claims 1 to 3, wherein a discharge valve is provided below the first cylinder portion. A gasifier main body in which the first cylinder, the second cylinder, and the third cylinder are connected in order from the lower side to the upper side from the upstream side of the gas flow.
A gasifying agent supply unit connected to the first cylinder portion and supplying a gasifying agent,
A biomass fuel supply unit connected to the second cylinder unit and supplying granular biomass fuel having an average sieve particle size of 0.5 mm or more and 3 mm or less.
The discharge valve provided below the first cylinder and
Equipped with
When the representative diameter of the first cylinder portion is 1,
The representative diameter of the second cylinder is 3 or more and 4.5 or less.
The representative diameter of the third cylinder is 6.5 or more and 7.5 or less, which is a method of operating a biomass gasification device.
The discharge valve is an operation method of a biomass gasification device which is opened after a predetermined operation time has elapsed. When the discharge valve is opened, the supply of the biomass fuel and the gasifying agent is stopped, and the supply is stopped.
The method for operating a biomass gasifier according to claim 5, wherein after closing the discharge valve, the supply of steam of the gasifying agent, the biomass fuel, and oxygen of the gasifying agent is started in this order.

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